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  • 1.
    Agmell, M.
    et al.
    Lund University, Sweden.
    Ahadi, A.
    Lund University, Sweden.
    Zhou, J. M.
    Lund University, Sweden.
    Peng, Ru
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Bushlya, V.
    Lund University, Sweden.
    Stahl, J. -E.
    Lund University, Sweden.
    Modeling subsurface deformation induced by machining of Inconel 7182017Ingår i: Machining science and technology, ISSN 1091-0344, E-ISSN 1532-2483, Vol. 21, nr 1, s. 103-120Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Traditionally, the development and optimization of the machining process with regards to the subsurface deformation are done through experimental method which is often expensive and time consuming. This article presents the development of a finite element model based on an updated Lagrangian formulation. The numerical model is able to predict the depth of subsurface deformation induced in the high- speed machining of Inconel 718 by use of a whisker-reinforced ceramic tool. The effect that the different cutting parameters and tool microgeometries has on subsurface deformation will be investigated both numerically and experimentally. This research article also addresses the temperature distribution in the workpiece and the connection it could have on the wear of the cutting tool. The correlation of the numerical and experimental investigations for the subsurface deformation has been measured by the use of the coefficient of determination, R-2. This confirms that the finite element model developed here is able to simulate this type of machining process with sufficient accuracy.

  • 2.
    Ahlbert, Gabriella
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Hållfasthetslära. Linköpings universitet, Tekniska högskolan.
    Method Evaluation of Global-Local Finite Element Analysis2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    When doing finite element analysis upon the structure of Saab’s aeroplanes a coarse global model of mainly shell elements is used to determine the load distribution for sizing the structure. At some parts of the aeroplane it is however desirable to implement a more detailed analysis. These areas are usually modelled with solid elements; the problem of connecting the fine local solid elements to the coarse global model will shell elements then arises.

     

    This master thesis is preformed to investigate possible Global-Local methods to use for the structural analysis on Gripen. First a literature study of current methods on the market is made, thereafter a few methods are implemented on a generic test structure and later on also tested on a real detail of Gripen VU. The methods tested in this thesis are Mesh refinement in HyperWorks, RBE3 in HyperWorks, Glue in MSC Patran/Nastran and DMIG in MSC Nastran. The software is however not evaluated in this thesis, and a further investigation is recommended to find the most fitting software for this purpose. All analysis are performed with linear assumptions.

     

    Mesh refinement is an integrated technique where the elements are gradually decreasing in size. Per definition, this technique cannot handle gaps, but it has almost identical results to the fine reference model.

     

    RBE3 is a type of rigid body elements with zero stiffness, and is used as an interface element. RBE3 is possible to use to connect both Shell-To-Shell and Shell-To-Solid, and can handle offsets and gaps in the boundary between the global and local model.

     

    Glue is a contact definition and is also available in other software under other names. The global respectively the local model is defined as contact bodies and a contact table is used to control the coupling. Glue works for both Shell-To-Shell and Shell-To-Solid couplings, but has problem dealing with offsets and gaps in the boundary between the global and local model.

     

    DMIG is a superelement technique where the global model is divided into smaller sub-models which are mathematically connected. DMIG is only possible to use when the nodes on the boundary on the local model have the same position as the nodes at the boundary of the global model. Thus, it is not possible to only use DMIG as a Global-Local method, but can advantageously be combined with other methods.

     

    The results indicate that the preferable method to use for Global-Local analysis is RBE3. To decrease the size of the files and demand of computational power, RBE3 can be combined with a superelement technique, for example DMIG.

     

    Finally, it is important to consider the size of the local model. There will inevitably be boundary effect when performing a Global-Local analysis of the suggested type, and it is therefore important to make the local model big enough so that the boundary effects have faded before reaching the area of interest.

  • 3.
    Ahmad, Maqsood
    et al.
    Base Engine & Materials Technology, Volvo Group, Gothenburg.
    Peng, Ru
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    König, Mathias
    Materials Technology for Basic Engine, Scania CV, Södertälje.
    Johansson, Sten
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Bending Fatigue Behavior of Blast Cleaned Grey Cast Iron2017Ingår i: Residual Stresses 2016: ICRS-10, Materials Research Proceedings 2 (2016), 2017, Vol. 2, s. 193-198Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper presents a detailed study on the effect of an industrial blast cleaning process on the fatigue behavior of a grey cast iron with regard to the residual stresses and microstructural changes induced by the process. A comparison was also made to the effect of a machining operation which removed the casting skin layer. The blast cleaning process was found to greatly improve the fatigue resistance in both the low and high cycle regimes with a 75% increase in the fatigue limit. Xray diffraction measurements and scanning electron microscopic analyses showed that the improvement was mainly attributed to compressive residual stresses in a surface layer up to 800 μm in thickness in the blast cleaned specimens. The machining also gave better fatigue performance with a 30% increase in the fatigue limit, which was ascribed to the removal of the weaker casting skin layer.

  • 4.
    Alm Grundström, Henrik
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Developments in Topology Optimization in the ADDMAN Project2018Rapport (Övrigt vetenskapligt)
    Abstract [en]

    This document gives an account of some of the work done so far on topology optimization (TO) in the ADDMAN project. As well as the mathematical formulations and implementations details, short discussions are presented on some of the nuances of the different formulations and how they should be used efficiently

  • 5.
    Alm Grundström, Henrik
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära.
    Topology Optimization for Additive Manufacturing Considering Stress and Anisotropy2017Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Additive manufacturing (AM) is a particularly useful manufacturing method for components designed using topology optimization (TO) since it allows for a greater part complexity than any traditional manufacturing method. However, the AM process potentially leads to anisotropic material properties due to the layer-by-layer buildup of parts and the fast and directional cooling. For Ti6Al4V tensile specimens built using electron beam melting (EBM), it has been observed that flat built specimens show superior strength and elastic moduli compared to top built specimens. Designs with the loading direction parallel to the build layers are therefore expected to show greater reliability.

    In this thesis a procedure is developed to optimize the AM build orientation considering anisotropic elastic material properties. A transversely isotropic material model is used to represent the in-plane and out-of-plane characteristics of AM produced parts. Two additional design variables are added to the TO formulation in order to control the orientation of the material using a coordinate transformation. Sensitivity analysis for the material direction variables is conducted for compliance as well as maximum von-Mises stress using a -norm stress aggregation function.

    The procedures for the AM build orientation optimization and stress constraints are implemented in the finite element software TRINITAS and evaluated using a number of examples in 2D and 3D. It is found that the procedure works well for compliance as well as stress but that a combination of these may lead to convergence issues due to contradicting optimal material orientations. An evaluation of the -norm stress aggregation function showed that a single global stress measure in combination with a stress correction procedure works well for most problems given that the mesh is refined enough to resolve the stresses accurately.  

  • 6.
    Andersson, Filip
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Maskinkonstruktion.
    Martinsson, Niklas
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Maskinkonstruktion.
    Filter cleaning device: for truck cab climate systems2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Scania has identified a problem among certain costumers in very dusty environments. The air filters for their truck’s climate system need extensive maintenance, replacement or manual cleaning, because of dust frequently loading up the filters. In this thesis the problem has been analyzed in order to find a solution. The process was initiated by the usage of the black box method, where needed transformations were found, resulting in three needed technical systems. Thereafter, brainstorming was used to find concepts for each technical system. Concepts were compared and ranked against each other. For the most critical of the three systems, the cleaning action, prototypes were built of the four highest ranked concepts. These prototypes were then used to compare the performance between the concepts.

    The selected filter cleaning device consists of a method to analyze filter blockage, alert the driver when cleaning is needed and a system to clean the filter for the Scania climate system. The system consists of a pressure sensor used to measuring filter blockage, an air pulse system which cleans the filter and a controller unit to control the cleaning cycle and to inform the driver. The air pulse system has two main parts, a pulse valve and an air tank. The pulse valve is used for releasing the air accumulated in the air tank. The complete system is supplied with 8.5 bar from the internal air pressure system in the truck and a 24 V power supply, also located in the truck.

    A suggestion on how a final implementation can be done has been developed, with a minimized number of variants and modifications of parts already in production. A proof of concept was built and mounted in a truck to validate the complete system. Numbers on cleaning performance and sound levels have been produced. The proof of concept manages to remove the restriction created from dust by approximately 50 %.

    Aside from developing a suitable filter cleaning device, figures on when the filter needs to be cleaned have been identified. To keep a good working environment within the cab a pressure drop over the filter of 936 Pa is recommended as a point of cleaning. This is to maintain the needed airflow of at least 123 m3/h with two persons seated in the cab to not exceed regulated levels of CO2 within the truck cab.

  • 7.
    Andersson, Håkan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    A Co-Simulation Approach for Hydraulic Percussion Units2018Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This Licentiate of Engineering thesis concerns modelling and simulation of hydraulic percussion units. These units are often found in equipment for breaking or drilling in rock and concrete, and are also often driven by oil hydraulics, in which complex fluid-structure couplings are essential for their operation.

    Current methodologies used today when developing hydraulic percussion units are based on decoupled analyses, which are not correctly capturing the important coupled mechanisms. Hence, an efficient method for coupled simulations is of high importance, since these mechanisms are critical for the function of these units. Therefore, a co-simulation approach between a 1D system simulation model representing the fluid system and a structural 3D FE-model is proposed.

    This approach is presented in detail, implemented for two well-known simulation tools and evaluated for a simple but relevant model. The Hopsan simulation tool was used for the fluid system and the FE-simulation software LS-DYNA was used for the structural mechanics simulation. The co-simulation interface was implemented using the Functional Mock-up Interface-standard.

    The approach was further developed to also incorporate multiple components for coupled simulations. This was considered necessary when models for the real application are to be developed. The use of two components for co-simulation was successfully evaluated for two models, one using the simple rigid body representation, and a second where linear elastic representations of the structural material were implemented.

    An experimental validation of the co-simulation approach applied to an existing hydraulic hammer was performed. Experiments on the hydraulic hammer were performed using an in-house test rig, and responses were registered at four different running conditions. The co-simulation model was developed using the same approach as before. The corresponding running conditions were simulated and the responses were successfully validated against the experiments. A parameter study was also performed involving two design parameters with the objective to evaluate the effects of a parameter change.

    This thesis consists of two parts, where Part I gives an introduction to the application, the simulation method and the implementation, while Part II consists of three papers from this project.

    Delarbeten
    1. A co-simulation method for system-level simulation of fluid-structure couplings in hydraulic percussion units
    Öppna denna publikation i ny flik eller fönster >>A co-simulation method for system-level simulation of fluid-structure couplings in hydraulic percussion units
    Visa övriga...
    2017 (Engelska)Ingår i: Engineering with Computers, ISSN 0177-0667, E-ISSN 1435-5663, Vol. 33, nr 2, s. 317-333Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    This paper addresses a co-simulation method for fluid power driven machinery equipment, i.e. oil hydraulic machinery. In these types of machinery, the fluid-structure interaction affects the end-product performance to a large extent, hence an efficient co-simulation method is of high importance. The proposed method is based on a 1D system model representing the fluid components of the hydraulic machinery, within which structural 3D Finite Element (FE) models can be incorporated for detailed simulation of specific sub-models or complete structural assemblies. This means that the fluid system simulation will get a more accurate structural response, and that the structural simulation will get more correct fluid loads at every time step, compared to decoupled analysis. Global system parameters such as fluid flow, performance and efficiency can be evaluated from the 1D system model simulation results. From the 3D FE-models, it is possible to evaluate displacements, stresses and strains to be used in stress analysis, fatigue evaluation, acoustic analysis, etc. The method has been implemented using two well-known simulation tools for fluid power system simulations and FE-simulations, respectively, where the interface between the tools is realised by use of the Functional Mock-up Interface standard. A simple but relevant model is used to validate the method.

    Ort, förlag, år, upplaga, sidor
    SPRINGER, 2017
    Nyckelord
    Co-simulation; Fluid-structure coupling; System simulation; Functional mock-up interface; Fluid power machinery; Transmission line modelling
    Nationell ämneskategori
    Datorsystem
    Identifikatorer
    urn:nbn:se:liu:diva-136875 (URN)10.1007/s00366-016-0476-8 (DOI)000398468100012 ()
    Anmärkning

    Funding Agencies|Atlas Copco Construction Tools

    Tillgänglig från: 2017-04-30 Skapad: 2017-04-30 Senast uppdaterad: 2018-09-11
    2. System level co-simulation of a control valve and hydraulic cylinder circuit in a hydraulic percussion unit
    Öppna denna publikation i ny flik eller fönster >>System level co-simulation of a control valve and hydraulic cylinder circuit in a hydraulic percussion unit
    Visa övriga...
    2017 (Engelska)Ingår i: Proceedings of 15:th Scandinavian International Conference on Fluid Power, June 7-9, 2017, Linköping, Sweden / [ed] Petter Krus, Liselott Ericson and Magnus Sethson, Linköping: Linköping University Electronic Press, 2017, Vol. 144, s. 225-235Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    In this study a previously developed co-simulation method that is based on a 1D system model representing the fluid components of a hydraulic machinery, within which structural 3D Finite Element (FE) models can be incorporated for detailed simulation of specific sub-models or complete structural assemblies, is further developed. The fluid system model consists of ordinary differential equation sub-models that are computationally very inexpensive, but still represents the fluid dynamics very well. The co-simulation method has been shown to work very well for a simple model representing a hydraulic driven machinery. A more complex model was set up in this work, in which two cylinders in the hydraulic circuit were evaluated. Such type of models, including both the main piston and control valves, are necessary as they represent the real application to a further extent than the simple model, of only one cylinder. Two models have been developed and evaluated, from the simple rigid body representation of the structural mechanics model, to the more complex model using linear elastic representation. The 3D FE-model facilitates evaluation of displacements, stresses, and strains on a local level of the model. The results can be utilised for fatigue assessment, wear analysis and for predictions of noise radiation.

    Ort, förlag, år, upplaga, sidor
    Linköping: Linköping University Electronic Press, 2017
    Serie
    Linköping Electronic Conference Proceedings, ISSN 1650-3686, E-ISSN 1650-3740 ; 144
    Nyckelord
    Co-simulation, Fluid-structure coupling, System simulation, Functional mockup interface, Fluid power machinery, Transmission line modelling
    Nationell ämneskategori
    Teknisk mekanik Farkostteknik Reglerteknik
    Identifikatorer
    urn:nbn:se:liu:diva-151015 (URN)10.3384/ecp17144225 (DOI)9789176853696 (ISBN)
    Konferens
    15th Scandinavian International Conference on Fluid Power, June 7-9, 2017, Linköping, Sweden
    Tillgänglig från: 2018-09-11 Skapad: 2018-09-11 Senast uppdaterad: 2018-09-11Bibliografiskt granskad
  • 8.
    Andersson, Håkan
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Hilding, Daniel
    DYNAmore Nordic AB, Brigadgatan 5, 587 58 Linköping, Sweden.
    Schill, Mikael
    DYNAmore Nordic AB, Brigadgatan 5, 587 58 Linköping, Sweden.
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    System level co-simulation of a control valve and hydraulic cylinder circuit in a hydraulic percussion unit2017Ingår i: Proceedings of 15:th Scandinavian International Conference on Fluid Power, June 7-9, 2017, Linköping, Sweden / [ed] Petter Krus, Liselott Ericson and Magnus Sethson, Linköping: Linköping University Electronic Press, 2017, Vol. 144, s. 225-235Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this study a previously developed co-simulation method that is based on a 1D system model representing the fluid components of a hydraulic machinery, within which structural 3D Finite Element (FE) models can be incorporated for detailed simulation of specific sub-models or complete structural assemblies, is further developed. The fluid system model consists of ordinary differential equation sub-models that are computationally very inexpensive, but still represents the fluid dynamics very well. The co-simulation method has been shown to work very well for a simple model representing a hydraulic driven machinery. A more complex model was set up in this work, in which two cylinders in the hydraulic circuit were evaluated. Such type of models, including both the main piston and control valves, are necessary as they represent the real application to a further extent than the simple model, of only one cylinder. Two models have been developed and evaluated, from the simple rigid body representation of the structural mechanics model, to the more complex model using linear elastic representation. The 3D FE-model facilitates evaluation of displacements, stresses, and strains on a local level of the model. The results can be utilised for fatigue assessment, wear analysis and for predictions of noise radiation.

  • 9.
    Andersson, Magnus
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska fakulteten. Swedish E Science Research Centre SeRC, Sweden.
    Lantz, Jonas
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för kardiovaskulär medicin. Linköpings universitet, Medicinska fakulteten. Swedish E Science Research Centre SeRC, Sweden.
    Ebbers, Tino
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för kardiovaskulär medicin. Linköpings universitet, Medicinska fakulteten. Region Östergötland, Hjärt- och Medicincentrum, Fysiologiska kliniken US. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Swedish E Science Research Centre SeRC, Sweden.
    Karlsson, Matts
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska fakulteten. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Swedish E Science Research Centre SeRC, Sweden.
    Correction: Quantitative Assessment of Turbulence and Flow Eccentricity in an Aortic Coarctation: Impact of Virtual Interventions (vol 6, pg 281, 2015)2015Ingår i: Cardiovascular Engineering and Technology, ISSN 1869-408X, E-ISSN 1869-4098, Vol. 6, nr 4, s. 577-589Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Turbulence and flow eccentricity can be measured by magnetic resonance imaging (MRI) and may play an important role in the pathogenesis of numerous cardiovascular diseases. In the present study, we propose quantitative techniques to assess turbulent kinetic energy (TKE) and flow eccentricity that could assist in the evaluation and treatment of stenotic severities. These hemodynamic parameters were studied in a pre-treated aortic coarctation (CoA) and after several virtual interventions using computational fluid dynamics (CFD), to demonstrate the effect of different dilatation options on the flow field. Patient-specific geometry and flow conditions were derived from MRI data. The unsteady pulsatile flow was resolved by large eddy simulation (LES) including non-Newtonian blood rheology. Results showed an inverse asymptotic relationship between the total amount of TKE and degree of dilatation of the stenosis, where the pre-stenotic hypoplastic segment may limit the possible improvement by treating the CoA alone. Spatiotem-poral maps of TKE and flow eccentricity could be linked to the characteristics of the post-stenotic jet, showing a versatile response between the CoA dilatations. By including these flow markers into a combined MRI-CFD intervention framework, CoA therapy has not only the possibility to produce predictions via simulation, but can also be validated pre-and immediate post treatment, as well as during follow-up studies.

  • 10.
    Andersson, Magnus
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.
    Lantz, Jonas
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Ebbers, Tino
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för kardiovaskulär medicin. Linköpings universitet, Hälsouniversitetet. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Östergötlands Läns Landsting, Hjärt- och Medicincentrum, Fysiologiska kliniken US.
    Karlsson, Matts
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan. Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV.
    Quantitative Assessment of Turbulence and Flow Eccentricity in an Aortic Coarctation - Impact of Virtual Interventions2015Ingår i: Cardiovascular Engineering and Technology, ISSN 1869-408X, E-ISSN 1869-4098, Vol. 6, nr 6, s. 281-293Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Turbulence and flow eccentricity can be measured by magnetic resonance imaging (MRI) and may play an important role in the pathogenesis of numerous cardiovascular diseases. In the present study, we propose quantitative techniques to assess turbulent kinetic energy (TKE) and flow eccentricity that could assist in the evaluation and treatment of stenotic severities. These hemodynamic parameters were studied in a pre-treated aortic coarctation (CoA) and after several virtual interventions using computational fluid dynamics (CFD), to demonstrate the effect of different dilatation options on the flow field. Patient-specific geometry and flow conditions were derived from MRI data. The unsteady pulsatile flow was resolved by large eddy simulation (LES) including non-Newtonian blood rheology. Results showed an inverse asymptotic relationship between the total amount of TKE and degree of dilatation of the stenosis, where turbulent flow proximal the constriction limits the possible improvement by treating the CoA alone. Spatiotemporal maps of TKE and flow eccentricity could be linked to the characteristics of the jet, where improved flow conditions were favored by an eccentric dilatation of the CoA. By including these flow markers into a combined MRI-CFD intervention framework, CoA therapy has not only the possibility to produce predictions via simulation, but can also be validated pre- and immediate post treatment, as well as during follow-up studies.

  • 11.
    Andersson, Magnus
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.
    Lantz, Jonas
    Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV. Linköpings universitet, Institutionen för teknik och naturvetenskap, Medie- och Informationsteknik. Linköpings universitet, Tekniska högskolan.
    Karlsson, Matts
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.
    NON-INVASIVE INTERVENTION PLANNING OF STENOTIC FLOWS USING SCALE-RESOLVED IMAGE-BASED COMPUTATIONAL FLUID DYNAMICS2013Konferensbidrag (Refereegranskat)
  • 12.
    Ankarberg, Martin
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Industriell Produktion.
    Jilnö, Erik
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Industriell Produktion.
    Redesign of Gas Hydraulic Suspension for Product Service System: A Master Thesis Work at Strömsholmen AB2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In these times, when manufacturing firms wonder how to integrate products and services into innovative offerings, how should products be designed to be of most value? This study is the investigation of this question for the manufacturing firm Strömsholmen AB, which designs gas springs and hydraulic suspension. The research has led to interviews of personnel to identify challenges and a workshop to generate new service ideas. By analyzing a specific gas hydraulic suspension product, this study shows that designing for product service systems (PSS) with a life-cycle perspective specifically for manufacturing, assembly, delivery, use, maintenance and remanufacturing, can greatly reduce costs and open up for innovative PSS business models. Using Design for Assembly, Design for Disassembly, Design for Serviceability and Design for Remanufacturing shows how concrete improvements to a product can be made. Improvements that show the potential of a redesign for the gas hydraulic suspension. Integrating products and services and pursuing the ideas and methods of this thesis, will ultimately make Strömsholmen better prepared to differentiate, to stay competitive, to deepen customer relations and to gain greater profits long-term.

  • 13.
    Arkman, Jonas
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Hållfasthetslära. Linköpings universitet, Tekniska högskolan.
    Boo, Christofer
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Hållfasthetslära. Linköpings universitet, Tekniska högskolan.
    Design och dimensionering av momentskärmsstativ för provflygning av JAS39 Gripen: Konceptverifiering med hjälp av handberäkningar och FEM2013Självständigt arbete på grundnivå (kandidatexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)
    Abstract [sv]

    Det här projektet har genomförts på uppdrag av Saab, med syftet att designa och dimensionera ett stativ för infästning av en momentskärm. Denna momentskärm används vid provflygning av JAS39 Gripen för att vid behov upphäva ett okontrollerat tillstånd som kan inträffa vid tester av spinnfall och högalfaflygningar.

    Det arbete som presenteras i den här rapporten är en del av ett större projekt där målet har varit att ta fram ett stativ. I den här rapporten presenteras analyser som har gjorts dels med handbokslösningar och klassisk hållfasthetslära, dels med FE-programmet Ansys för att kontrollera att det slutgiltiga konceptet uppfyller samtliga givna krav.

    Vid dimensioneringen har ett iterativt arbetssätt använts, det har byggt på att först ta fram ett grundläggande koncept och sedan förbättra detta under projektets gång. Efter varje iteration har analyser gjorts av resultatet för att verifiera stativets funktion. För att inte påverka flygegenskaperna mer än nödvändigt har det även varit viktigt att minimera stativets vikt. Projektet har resulterat i ett koncept av titanlegeringen Ti-6Al-4V med en vikt på 67,7 kg.

  • 14.
    Arrell, Douglas
    et al.
    Siemens Industrial Turbomachinery AB, Finspång.
    Hasselqvist, Magnus
    Siemens Industrial Turbomachinery AB, Finspång.
    Sommer, C
    ABB Technology Ldt, Heidelberg, Germany.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    On TMF damage, degradation effects, and the associated TMin influence on TMF test results in γ/γ′ alloys2004Ingår i: Proceedings of the International Symposium on Superalloys / [ed] Green K.A., Pollock T.M., Harada H., Howson T.E., Reed R.C., Schirra J.J., Walston S., Warrendale, PA, USA: The Minerals, Metals and Materials Society, TMS , 2004, s. 291-294Konferensbidrag (Övrigt vetenskapligt)
  • 15.
    Asghar, Raja Babar
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik.
    Optimization as a Thermodynamic System2010Självständigt arbete på avancerad nivå (masterexamen), 30 poäng / 45 hpStudentuppsats (Examensarbete)
    Abstract [en]

    As we know that nature made the things optimized in all point of views, also it is supposed that nature works under some evolutionary process.

    Since there was no such Evolutionary Structural Optimization (ESO) method having strong mathematical background, that’s why these are not much reliable. The purpose of this thesis work is a little effort to introduce such an ESO method having a strong mathematical background.

    In this thesis work Optimization as a thermodynamic system, we are introducing a new method for topology optimization by using concept of Free Energy and Dissipation Potential from non-smooth thermodynamics system. For better understanding we may call it as Evolutionary Structural Topology Optimization (ESTO), and this project work is done in the following steps.

    An evolution problem is formulated in terms of free energy and dissipation potential for a non-smooth thermodynamical system. Free energy is taken as an objective function for a general structural optimization problem. Derivation of a well posed evolution problem for which evolution is such that objective function always decreases. An optimality criteria method is derived for given evolution problem and it is implemented in a FEM program TRINITAS. And the behaviour of the so called evolutionary parameters such as Forward and Backward plastic constants is analyzed.

  • 16.
    Athanasiou, Vasileios
    Linköpings universitet, Institutionen för medicin och hälsa, Avdelningen för radiologiska vetenskaper. Linköpings universitet, Hälsouniversitetet.
    Estimation and modelling of fMRI BOLD response2014Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    One of the current topics of research in neuroimaging techniques is related to explaining and modelling the Blood Oxygen Level Dependent (BOLD) responses. BOLD responses are estimated by processing functional Magnetic Resonance Imaging (fMRI) data. BOLD responses are caused by hemodynamic responses to neural activity which alter the levels of blood oxygenation at local brain regions. The main aims of the current thesis were to i) develop and examine methods regarding BOLD response estimation from the visual cortex and the frontal cortex of human brain and to ii) develop a model in order to explain the physiological mechanisms which cause the estimated BOLD responses.

    In order to satisfy the main aims, fMRI data were provided by the Center of Medical Imaging and Visualization (CMIV). The provided fMRI data consist of fMRI brain measurements of twelve healthy human subjects who were subjected to visual stimulation. By processing the fMRI data, Regions Of Interest (ROIs) were extracted at the anatomical sites of the visual cortex and the frontal cortex. Afterwards, the fMRI data were manipulated in order to extract BOLD responses from the visual cortex and the frontal cortex. Various methods were developed and compared in terms of which technique provided well representative BOLD responses.       

    Subsequently, a model was developed by using software Wolfram Mathematica 9 in order to explain the physiological mechanisms of the estimated BOLD responses at the visual and the frontal cortex. The model aimed to solve for oxygen concentration in blood plasma as blood flows from the arterial part to the venous part of the blood circulation system through a capillary. Oxygen outward diffusion through the capillary wall and oxygen concentration at the extravascular environment were modelled as well. Blood plasma oxygen concentration was turned into hemoglobin oxygen saturation (Sa ) through hemoglobin oxygen dissociation curve and Henry’s law for gases. As a result, the Sa  was estimated through modelling for oxygen concentration in blood plasma. Finally, the developed model ended to a system with input the fractional change of Cerebral Blood Flow (CBF) velocity and Cerebral Metabolic Rate of Oxygen (CMR ) and as output a proportional signal to the BOLD response. By simulating for different scenarios of fractional changes of CBF velocity and CMR  and by comparing the resulted BOLD responses to the estimated ones, it was attempted to explain for the physiological mechanisms which caused the BOLD responses at the anatomical sites of the visual and frontal cortex.

  • 17.
    Azeez, Ahmed
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära.
    Effect of dwell time on stress intensity factor of ferritic steel for steam turbine applications2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    In the transition from conventional to green energy production resources, steam turbines are used to satisfy the lack of energy during peaks in the demand times and the limited access of renewable resources. This type of usage for steam turbines makes them operate on a flexible schedule, which leads to unpredictable issues related to shorter component life and faster crack propagation. Thus, the steam turbine components must be examined to determine their specific life period. This will help set proper maintenance intervals and prevent unexpected failures. For that, thermo-mechanical fatigue (TMF) testing is used, where a specimen made of the same material as the turbine component is subjected to both temperature and load variation. The specimen is pre-cracked to investigate the crack propagation behavior, which is the focus of this study.

    This thesis work concentrates on simulating the TMF cycle for the steam turbine casing component. The material is 9%-10%Cr ferritic steel. The aim is to understand the material behavior during crack propagation and to predict a useful testing parameter. The method provided in this work discusses two cases, both are out-of-phase (OP) TMF tests with strain control. The maximum and minimum temperatures for the cycle are 600 ˚C and 400 ˚C respectively, while the maximum and minimum strain levels are 0 and  respectively. The study will investigate different , which is the maximum compressive strain level. Case 1 has a dwell time at the maximum temperature only, while case 2 has dwell times at both maximum and minimum temperatures. The method utilizes the stress intensity factor (SIF) to characterize the crack tip conditions. Also, it uses Paris' law to estimate the duration of the tests. For simplification, only the elastic behavior of the material is considered.

    The results obtained show no effect of using different pre-crack lengths due to the strain control condition. Minor effects can be observed by using different dwell times, however very short dwell times must be avoided to produce reliable results. A recommended dwell time of 5 minutes could be used, since longer dwell times will make the test prohibitively time-consuming. The compressive strain levels used in the work shows large effects on the results. Using low compressive strain values will produce a very long time for the tests, while very high compressive strains produce large plasticity. Thus, high compressive strains must be avoided since the SIF describes cracks for only elastic or near elastic cases. Also, small compressive strain levels in case 2 should not be used since it will lead to results like case 1. This is due to the small creep effect at the minimum temperature. Finally, compressive strain levels of 0.6 %, 0.5 % and 0.4 % are recommended for case 1, while only 0.6 % compressive strain level is recommended for case 2.

    This thesis contributes to the fields of solid mechanics, fracture mechanics and the use of TMF testing, where a recommended set of testing parameters are provided.

  • 18.
    Bajuri, M. N.
    et al.
    University of Oxford, England; University of Teknol Malaysia, Malaysia.
    Isaksson, Hanna
    Lund University, Sweden.
    Eliasson, Pernilla T.
    Linköpings universitet, Institutionen för klinisk och experimentell medicin, Avdelningen för kliniska vetenskaper. Linköpings universitet, Medicinska fakulteten.
    Thompson, Mark S.
    University of Oxford, England.
    A hyperelastic fibre-reinforced continuum model of healing tendons with distributed collagen fibre orientations2016Ingår i: Biomechanics and Modeling in Mechanobiology, ISSN 1617-7959, E-ISSN 1617-7940, Vol. 15, nr 6, s. 1457-1466Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The healing process of ruptured tendons is problematic due to scar tissue formation and deteriorated material properties, and in some cases, it may take nearly a year to complete. Mechanical loading has been shown to positively influence tendon healing; however, the mechanisms remain unclear. Computational mechanobiology methods employed extensively to model bone healing have achieved high fidelity. This study aimed to investigate whether an established hyperelastic fibre-reinforced continuum model introduced by Gasser, Ogden and Holzapfel (GOH) can be used to capture the mechanical behaviour of the Achilles tendon under loading during discrete timepoints of the healing process and to assess the models sensitivity to its microstructural parameters. Curve fitting of the GOH model against experimental tensile testing data of rat Achilles tendons at four timepoints during the tendon repair was used and achieved excellent fits (0.9903 amp;lt; R-2 amp;lt; 0.9986). A parametric sensitivity study using a three-level central composite design, which is a fractional factorial design method, showed that the collagen-fibre-related parameters in the GOH model-kappa, k(1) and k(2)-had almost equal influence on the fitting. This study demonstrates that the GOH hyperelastic fibre-reinforced model is capable of describing the mechanical behaviour of healing tendons and that further experiments should focus on establishing the structural and material parameters of collagen fibres in the healing tissue.

  • 19.
    Baravdish, George
    et al.
    Linköpings universitet, Institutionen för teknik och naturvetenskap, Kommunikations- och transportsystem. Linköpings universitet, Tekniska fakulteten.
    Borachok, Ihor
    Ivan Franko Natl Univ Lviv, Ukraine.
    Chapko, Roman
    Ivan Franko Natl Univ Lviv, Ukraine.
    Johansson, B. Tomas
    Aston Univ, England.
    Slodicka, Marian
    Univ Ghent, Belgium.
    An iterative method for the Cauchy problem for second-order elliptic equations2018Ingår i: International Journal of Mechanical Sciences, ISSN 0020-7403, E-ISSN 1879-2162, Vol. 142, s. 216-223Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The problem of reconstructing the solution to a second-order elliptic equation in a doubly-connected domain from knowledge of the solution and its normal derivative on the outer part of the boundary of the solution domain, that is from Cauchy data, is considered. An iterative method is given to generate a stable numerical approximation to this inverse ill-posed problem. The procedure is physically feasible in that boundary data is updated with data of the same type in the iterations, meaning that Dirichlet values is updated with Dirichlet values from the previous step and Neumann values by Neumann data. Proof of convergence and stability are given by showing that the proposed method is an extension of the Landweber method for an operator equation reformulation of the Cauchy problem. Connection with the alternating method is discussed. Numerical examples are included confirming the feasibility of the suggested approach.

    Publikationen är tillgänglig i fulltext från 2020-04-24 00:01
  • 20.
    Barba, D.
    et al.
    Univ Oxford, England.
    Alabort, E.
    Univ Oxford, England.
    Garcia-Gonzalez, D.
    Univ Oxford, England.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Reed, R. C.
    Univ Oxford, England.
    Jerusalem, A.
    Univ Oxford, England.
    A thermodynamically consistent constitutive model for diffusion-assisted plasticity in Ni-based superalloys2018Ingår i: International journal of plasticity, ISSN 0749-6419, E-ISSN 1879-2154, Vol. 105, s. 74-98Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    An elasto-viscoplastic thermodynamically consistent constitutive model for diffusion-assisted phase transformations is presented here. The model accounts for the different deformation mechanisms, their time dependence, the crystal rotations produced by microtwin propagation and the chemistry-plasticity coupling occurring at high temperature. It is applied to the study of the chemically assisted microtwinning observed in Ni-based superalloys in the temperature range of 600-800 degrees C. The model parameters are calibrated against multi-directional mechanical data from tensile creep tests of single crystal superalloy MD2. The constitutive model is then implemented into a crystal plasticity finite element code to study the activation of the different deformation mechanisms within single crystal and polycrystalline aggregates. Doing so, a relation between the rotations of the crystal and the creep life of the different crystal orientations is established. The results eventually reveal the critical role of the strong anisotropy of microtwin formation on the asymmetric behavior of the alloy and its relevant role on the mechanical performance.

  • 21.
    Biju, Dona
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära.
    A parametric study of oil-jet lubrication in gear wheels2018Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    A parametric study of oil-jet lubrication in gear wheels is conducted using Computational Fluid Dynamics (CFD) to study the effect of the different design parameters on the cooling performance in a gearbox. Flow in oil jet lubrication is found to be complex with the formation of oil ligaments and droplets. Various hole radii of 1.5, 2 and 2.5 mm along with five oil velocities is analyzed and it is found that at lower volumetric rates, velocity has more effect on the cooling and at higher volumetric rates, hole size has more effect on the cooling. At higher velocities, the heat transfer is much greater than the actual heat production in the gear wheel, hence these velocity ratios are considered less suitable for jet lubrication. At low velocity ratios of below 2, the oil doesn’t fully impinge the gear bottom land and the sides leading to low cooling. Based on the cooling, impingement length and amount of oil lost to the casing surface, 2 mm hole with a velocity ratio of 2.225 is selected for a successful oil jet lubrication. Varying the inlet position in X, Y and Z directions (horizontal, vertical and lateral respectively) is found to have no improvement on the cooling. Making the oil jet hit the gear wheel surface at an angle is found to increase the cooling. Analysis with the use of a pipe to supply oil was conducted with circular and square inlet and it was found that the heat transfer decreases in both cases due to the splitting of oil jet caused by the combination of the effects of high pressure from the pipe and vorticity in the air field. A method has been developed for two gear analysis using overset meshes which can be used for further studies of jet lubrication in multi-gear systems. Single inlet is found to be better for cooling two gear wheels as it would require a reduced volumetric flow rate compared to double inlets. Oil system requirements for jet lubrication was studied and it was concluded that larger pumps have to be used to provide the high volumetric rates and highly pressurized oil required. On comparing the experimental losses from dip lubrication and the analytical losses for jet lubrication, dip lubrication is found to have lesser loses and more suitable for this case. Good quality lubrication would reduce the fuel consumption and also increase the longevity of gearboxes and hence more research into analyzing alternate lubrication systems can be carried out using the results from this thesis.

  • 22.
    Boqvist, Emil
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanisk värmeteori och strömningslära. Linköpings universitet, Tekniska högskolan.
    Investigation of a swing check valve using CFD2014Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    This master’s thesis is made to increase the understanding of the dynamic characteristics of a typical large swing check valve used in a system that transports pressurized water to a reactor tank.3D FSI-simulations are performed for a number of transients in order to study the dynamic characteristics their dependence of the deceleration rate. The purpose is to find information about the dynamics that could be used in a future improvement of a 1D-model.Steady state simulations are performed for angles in the whole spectrum. Seven transient FSI-simulations with different constantly decelerating flows from 630 kg/s2 (6.7 m/s2) to 40 320 kg/s2 (430 m/s2) have been performed. The pressure on the disc caused by the hydraulic torque is integrated and the corresponding torque contribution, together with the weight torque, is used in the second law of motion to calculate the movement of the disc throughout the transients.Steady state simulations yield the pressure drop over the valve, which could be compared with field measurements in order to validate the CFD-simulations. Comparison of the pressure distribution on the disc for the steady state and transient simulations shows the importance of taking the disc angular velocity into account when modelling in 1D. Correlations between the angle, angular velocity, torque and mass flow are obtained from the transient FSI-simulations. Torque coefficients according to (Li & Liou, Vol. 125) are also brought out from the simulated transients, but in order to create a model in line with this approach further simulations have to be performed. A prediction of the pressure rise that occurs when a swing check valve closes in backward flow according to the Joukowsky equation is brought out and gives an idea of the loadings that the system has to be able to handle.

  • 23.
    Busse, Christian
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Aspects of Crack Growth in Single-Crystal Nickel-Base Superalloys2017Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    Denna licentiatavhandling är en produkt av resultat som genererats i forskningsprojektet KME-702, och omfattar modellering, mikrostrukturundersökningar och materialprovning av gjutna nickelbaserade superlegeringar.

    Huvudsyftet med detta arbete är att modellera sprickförloppet under utmattning i enkristallina nickelbaserade superlegeringar. För att uppnå detta har kristallorienteringens inverkan på sprickbeteendet utvärderats. Resultaten visar att kristallorienteringen har en stark inverkan på materialbeteendet, således måste hänsyn till denna tas. Dessutom har en linjär-elastisk sprickdrivkraftsparameter lämplig att beskriva kristallografisk sprickbildning utvecklats. Denna parameter är baserad på anisotropa spänningsintensitetsfaktorer på kristallplan och kan prediktera det korrekta kristallografiska sprickplanet efter övergång från Modus I spricka. Slutligen har undersökts en metod för att ta hand om inelastiska deformationer i en linjär-elastisk brottmekanikskontext. Ett restspänningsfält extraherades från en osprucken finita element modell med en ideal plastisk materialmodell. Denna överlagrades på spänningsfältet från den spruckna modellen, som analyserades med en linjär-elastisk materialmodell, för att ta hänsyn till de inelastiska deformationerna vid bestämning av sprickdrivkraften. Modelleringsarbetet validerades genom materialprovning på två olika provgeometrier vid olika temperaturer.

    Licentiatavhandlingen består av två delar, där del I ger en introduktion och bakgrund till forskningsområdet medan del II består av tre papper.

    Delarbeten
    1. A FINITE ELEMENT STUDY OF THE EFFECT OF CRYSTAL ORIENTATION AND MISALIGNMENT ON THE CRACK DRIVING FORCE IN A SINGLE-CRYSTAL SUPERALLOY
    Öppna denna publikation i ny flik eller fönster >>A FINITE ELEMENT STUDY OF THE EFFECT OF CRYSTAL ORIENTATION AND MISALIGNMENT ON THE CRACK DRIVING FORCE IN A SINGLE-CRYSTAL SUPERALLOY
    Visa övriga...
    2016 (Engelska)Ingår i: PROCEEDINGS OF THE ASME TURBO EXPO: TURBINE TECHNICAL CONFERENCE AND EXPOSITION, 2016, VOL 7A, AMER SOC MECHANICAL ENGINEERS , 2016, nr UNSP V07AT28A002Konferensbidrag, Publicerat paper (Refereegranskat)
    Abstract [en]

    The elastic and plastic anisotropy of the single-crystal materials bring many difficulties in terms of modeling, evaluation and prediction of fatigue crack growth. In this paper a single-crystal material model has been adopted to a finite element-environment, which is paired with a crack growth tool. All simulations are performed in a three-dimensional context. This methodology makes it possible to analyze complex finite element-models, which are more application-near than traditional two-dimensional models. The influence of the crystal orientation, as well as the influence of misalignments of the crystal orientation due to the casting process are investigated. It is shown that both the crystal orientation and the misalignment from the ideal crystal orientation are important for the crack driving force. The realistic maximum limit of 10 degrees misalignment is considered. It can be seen that crack growth behavior is highly influenced by the misalignment. This knowledge is of great interest for the industry in order to evaluate the crack growth in single-crystal components more accurately.

    Ort, förlag, år, upplaga, sidor
    AMER SOC MECHANICAL ENGINEERS, 2016
    Nationell ämneskategori
    Teknisk mekanik
    Identifikatorer
    urn:nbn:se:liu:diva-132570 (URN)10.1115/GT2016-56305 (DOI)000385461600011 ()978-0-7918-4983-5 (ISBN)
    Konferens
    ASME Turbo Expo: Turbine Technical Conference and Exposition
    Tillgänglig från: 2016-11-14 Skapad: 2016-11-14 Senast uppdaterad: 2019-09-23
    2. Three-Dimensional LEFM Prediction of Fatigue Crack Propagation in a Gas Turbine Disk Material at Component Near Conditions
    Öppna denna publikation i ny flik eller fönster >>Three-Dimensional LEFM Prediction of Fatigue Crack Propagation in a Gas Turbine Disk Material at Component Near Conditions
    Visa övriga...
    2016 (Engelska)Ingår i: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 138, nr 4, artikel-id 042506Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    In this paper, the possibility to use linear elastic fracture mechanics (LEFM), with and without a superimposed residual stress field, to predict fatigue crack propagation in the gas turbine disk material Inconel 718 has been studied. A temperature of 400 degrees C and applied strain ranges corresponding to component near conditions have been considered. A three-dimensional crack propagation software was used for determining the stress intensity factors (SIFs) along the crack path. In the first approach, a linear elastic material behavior was used when analyzing the material response. The second approach extracts the residual stresses from an uncracked model with perfectly plastic material behavior after one loading cycle. As a benchmark, the investigated methods are compared to experimental tests, where the cyclic lifetimes were calculated by an integration of Paris law. When comparing the results, it can be concluded that the investigated approaches give good results, at least for longer cracks, even though plastic flow was taking place in the specimen. The pure linear elastic simulation overestimates the crack growth for all crack lengths and gives conservative results over all considered crack lengths. Noteworthy with this work is that the 3D-crack propagation could be predicted with the two considered methods in an LEFM context, although plastic flow was present in the specimens during the experiments.

    Ort, förlag, år, upplaga, sidor
    ASME, 2016
    Nationell ämneskategori
    Maskinteknik
    Identifikatorer
    urn:nbn:se:liu:diva-126240 (URN)10.1115/1.4031526 (DOI)000371125800020 ()
    Anmärkning

    Funding Agencies|Siemens Industrial Turbomachinery AB through Research Consortium of Materials Technology for Thermal Energy Processes [KME-702]; Swedish Energy Agency

    Tillgänglig från: 2016-03-21 Skapad: 2016-03-21 Senast uppdaterad: 2019-09-23
  • 24.
    Busse, Christian
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Modelling of Crack Growth in Single-Crystal Nickel-Base Superalloys2019Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This dissertation was produced at the Division of Solid Mechanics at Linköping University and is part of a research project, which comprises modelling, microstructure investigations and material testing of cast nickel-base superalloys. The main objective of this work was to deepen the understanding of the fracture behaviour of single-crystal nickel-base superalloys and to develop a model to predict the fatigue crack growth behaviour. Frequently, crack growth in these materials has been observed to follow one of two distinct cracking modes; Mode I like cracking perpendicular to the loading direction or crystallographic crack growth on the octahedral {111}-planes, where the latter is associated with an increased fatigue crack growth rate. Thus, it is of major importance to account for this behaviour in component life prediction. Consequently, a model for the prediction of the transition of cracking modes and the correct active crystallographic plane, i.e. the crack path, and the crystallographic crack growth rate has been developed. This model is based on the evaluation of appropriate crack driving forces using three-dimensional finite-element simulations. A special focus was given towards the influence of the crystallographic orientation on the fracture behaviour. Further, a model to incorporate residual stresses in the crack growth modelling is presented. All modelling work is calibrated and validated by experiments on different specimen geometries with different crystallographic orientations. This dissertation consists of two parts, where Part I gives an introduction and background to the field of research, while Part II consists of six appended papers.

  • 25.
    Busse, Christian
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Loureiro Homs, Jordi
    Siemens Ind Turbomachinery AB, Sweden.
    Gustafsson, David
    Siemens Ind Turbomachinery AB, Sweden.
    Palmert, Frans
    Siemens Ind Turbomachinery AB, Sweden.
    Sjodin, Bjorn
    Siemens Ind Turbomachinery AB, Sweden.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    A FINITE ELEMENT STUDY OF THE EFFECT OF CRYSTAL ORIENTATION AND MISALIGNMENT ON THE CRACK DRIVING FORCE IN A SINGLE-CRYSTAL SUPERALLOY2016Ingår i: PROCEEDINGS OF THE ASME TURBO EXPO: TURBINE TECHNICAL CONFERENCE AND EXPOSITION, 2016, VOL 7A, AMER SOC MECHANICAL ENGINEERS , 2016, nr UNSP V07AT28A002Konferensbidrag (Refereegranskat)
    Abstract [en]

    The elastic and plastic anisotropy of the single-crystal materials bring many difficulties in terms of modeling, evaluation and prediction of fatigue crack growth. In this paper a single-crystal material model has been adopted to a finite element-environment, which is paired with a crack growth tool. All simulations are performed in a three-dimensional context. This methodology makes it possible to analyze complex finite element-models, which are more application-near than traditional two-dimensional models. The influence of the crystal orientation, as well as the influence of misalignments of the crystal orientation due to the casting process are investigated. It is shown that both the crystal orientation and the misalignment from the ideal crystal orientation are important for the crack driving force. The realistic maximum limit of 10 degrees misalignment is considered. It can be seen that crack growth behavior is highly influenced by the misalignment. This knowledge is of great interest for the industry in order to evaluate the crack growth in single-crystal components more accurately.

  • 26.
    Busse, Christian
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Palmert, Frans
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Sjodin, B.
    Siemens Ind Turbomachinery AB, Sweden.
    Almroth, P.
    Siemens Ind Turbomachinery AB, Sweden.
    Gustafsson, D.
    Siemens Ind Turbomachinery AB, Sweden.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Evaluation of the crystallographic fatigue crack growth rate in a single-crystal nickel-base superalloy2019Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 127, s. 259-267Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Cracks in single-crystal nickel-base superalloys have been observed to switch cracking mode from Mode I to crystallographic cracking. The crack propagation rate is usually higher on the crystallographic planes compared to Mode I, which is important to account for in crack growth life predictions. In this paper, a method to evaluate the crystallographic fatigue crack growth rate, based on a previously developed crystallographic crack driving force parameter, is presented. The crystallographic crack growth rate was determined by evaluating heat tints on the fracture surfaces of the test specimens from the experiments. Complicated crack geometries including multiple crystallographic crack fronts were modelled in a three dimensional finite element context, The data points of the crystallographic fatigue crack growth rate collapse on a narrow scatter band for the crystallographic cracks indicating a correlation with the previously developed crystallographic crack driving force.

  • 27.
    Busse, Christian
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Palmert, Frans
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Sjodin, B.
    Siemens Ind Turbomachinery AB, Sweden.
    Almroth, P.
    Siemens Ind Turbomachinery AB, Sweden.
    Gustafsson, D.
    Siemens Ind Turbomachinery AB, Sweden.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Prediction of crystallographic cracking planes in single-crystal nickel-base superalloys2018Ingår i: Engineering Fracture Mechanics, ISSN 0013-7944, E-ISSN 1873-7315, Vol. 196, s. 206-223Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The inherent anisotropy of single-crystal nickel-base superalloys brings many difficulties in terms of modelling, evaluation and prediction of fatigue crack growth. Two models to predict on which crystallographic plane cracking will occur is presented. The models are based on anisotropic stress intensity factors resolved on crystallographic slip planes calculated in a three-dimensional finite-element context. The developed models have been compared to experiments on two different test specimen geometries. The results show that a correct prediction of the crystallographic cracking plane can be achieved. This knowledge is of great interest for the industry and academia to better understand and predict crack growth in single-crystal materials.

    Publikationen är tillgänglig i fulltext från 2020-05-05 15:21
  • 28.
    Calmunger, Mattias
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial.
    Effect of temperature on mechanical response of austenitic materials2011Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Global increase in energy consumption and global warming require more energy production but less CO2emission. Increase in efficiency of energy production is an effective way for this purpose. This can be reached by increasing boiler temperature and pressure in a biomass power plant. By increasing material temperature 50°C, the efficiency in biomass power plants can be increased significantly and the CO2emission can be greatly reduced. However, the materials used for future biomass power plants with higher temperature require improved properties. Austenitic stainless steels are used in most biomass power plants. In austenitic stainless steels a phenomenon called dynamic strain aging (DSA), can occur in the operating temperature range for biomass power plants. DSA is an effect of interaction between moving dislocations and solute atoms and occurs during deformation at certain temperatures. An investigation of DSA influences on ductility in austenitic stainless steels and nickel base alloys have been done. Tensile tests at room temperature up to 700°C and scanning electron microscope investigations have been used. Tensile tests revealed that ductility increases with increased temperature for some materials when for others the ductility decreases. This is, probably due to formation of twins. Increased stacking fault energy (SFE) gives increased amount of twins and high nickel content gives a higher SFE. Deformation mechanisms observed in the microstructure are glide bands (or deformations band), twins, dislocation cells and shear bands. Damage due to DSA can probably be related to intersection between glide bands or twins, see figure 6 a). Broken particles and voids are damage mechanisms observed in the microstructure.

  • 29.
    Cao, Cejun
    et al.
    Tianjin Univ, Peoples R China; Jinan Univ, Peoples R China.
    Li, Congdong
    Tianjin Univ, Peoples R China; Jinan Univ, Peoples R China.
    Yang, Qin
    Sichuan Normal Univ, Peoples R China.
    Liu, Yang
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Industriell miljöteknik. Linköpings universitet, Tekniska fakulteten. Jinan Univ, Peoples R China; Univ Vaasa, Finland.
    Qu, Ting
    Jinan Univ, Peoples R China.
    A novel multi-objective programming model of relief distribution for sustainable disaster supply chain in large-scale natural disasters2018Ingår i: Journal of Cleaner Production, ISSN 0959-6526, E-ISSN 1879-1786, Vol. 174, s. 1422-1435Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    To save lives and reduce suffering of victims, the focus of this paper is to design the strategies of relief distribution regarding beneficiary perspective on sustainability. This problem is formulated as a multi objective mixed-integer nonlinear programming model to maximize the lowest victims perceived satisfaction, and minimize respectively the largest deviation on victims perceived satisfaction for all demand points and sub-phases. Then, genetic algorithm is proposed to solve this mathematical model. To validate the proposed methodologies, a case study from Wenchuan earthquake is illustrated. Computational results demonstrate genetic algorithm here can achieve the trade-off between solution quality and computation time for relief distribution with the concern of sustainability. Furthermore, it indicates that the methodology provides the tools for decision-makers to optimize the structure of relief distribution network and inventory, as well as alleviate the suffering of victims. Increasingly, this paper expects to not only validate the proposed model and method, but also highlight the importance and urge of considering beneficiary perspective on sustainability into relief distribution problem. (C) 2017 Elsevier Ltd. All rights reserved.

  • 30.
    Chai, Guocai
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten. R&D Center, Sandvik Materials Technology, Sandviken, Sweden.
    Forsman, Tomas
    R&D Center, Sandvik Materials Technology, Sandviken, Sweden.
    Gustavsson, Fredrik
    R&D Center, Sandvik Materials Technology, Sandviken, Sweden.
    Microscopic and Nanoscopic Study on Subsurface Damage and Fatigue Crack Initiation During Very High Cycle Fatigue2016Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 83, nr 2, s. 288-292Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    “Fish eye” is a typical phenomenon of fatigue crack initiation at a subsurface defect such as inclusion during very high cycle fatigue. The formation of a fine grained area and micro-debonding is believed to cause fatigue crack initiation. This paper provides a basic study on the formation of the fine grained area in a martensitic stainless steel during very high cycle fatigue using scanning electron microscopy, SEM, focused ion beam technique, FIB, electron backscatter diffraction, EBSD, and electron channeling contrast imaging, ECCI. The results show that the formation of a fine grained zone is a local behavior. The fine grained zone is very near the fatigue crack initiation origin. In the transversal direction (cross section), the depth of the fine grained zone is only few micrometers. In the longitudinal direction (crack propagation direction), the depth of the fine grain zone is about one micrometer. ECCI analysis shows that in the fine grained area with high retained strain, high plastic deformation can be found. Dislocation slip bands can be observed. They interact with grain boundaries and cause the formation of damage due to impingement cracking. The results indicate that occurrence of plastic deformation in metallic material during very high cycle fatigue is very localized, mainly near the front of the crack tip or a defect.

  • 31.
    Eriksson, Erik
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Hållfasthetslära. Linköpings universitet, Tekniska högskolan.
    Jonsson, Ida
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Hållfasthetslära. Linköpings universitet, Tekniska högskolan.
    Skog, Christian
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Hållfasthetslära. Linköpings universitet, Tekniska högskolan.
    Öhrn, Robin
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Hållfasthetslära. Linköpings universitet, Tekniska högskolan.
    Dimensionering av momentskärmstativ2013Rapport (Övrigt vetenskapligt)
    Abstract [sv]

    På uppdrag av Saab ska fyra studenter vid Linköpings tekniska högskola designa och dimensionera ett momentskärmstativ till nya JAS39 Gripen E. På stativet fästs en skärmbehållare med en skärm, som används vid testflygning. Stativet sitter längst bak på planet, bakom sidorodret och ovanför stjärtkonen. Skärmen är en säkerhetsfunktion och kan skjutas ut och ge flygplanet ett stabiliserande tippmoment vid okontrollerade spinnfall som kan uppkomma vid högalfaflygning. Stativet ska klara av från uppdragsgivare givna lastfall och deformationskrav samtidigt som fokus skall ligga på viktreducering.

    Projektet började med konceptgenerering för att få fram ett grundkoncept att arbeta vidare med. Materialundersökningar genomfördes med hjälp av materialdatabasen CES EduPack 2012 för att hitta ett material med bättre egenskaper än det som använts i tidigare stativ. Utifrån materialet undersöktes även fogar, tillåtna initialsprickor samt knäckningsrisk. Olika tvärsnitt undersöktes och för att ta reda på deformationer och spänningar genomfördes FEM-analyser i Ansys Workbench 14.0. Utifrån analysresultaten förändrades stativets design tills det klarade kraven.

    Arbetet resulterade i ett fackverksstativ huvudsakligen uppbyggt av ihåliga kvadratiska balkar med yttermåtten 70 mm och innermåtten 63,8 mm. Maximala deformationen blir 53,1 mm, maximala spänningen 883 MPa och materialet som användes var titanlegeringen Ti-6Al-4V. Stativets balkar sammanfogas med lasersvets och det finns ingen risk för knäckning. Den tillåtna längden på en eventuell initialspricka är 0,7 mm för ytspricka och 0,9 mm för inre genomgående spricka. Det designade stativets slutvikt uppmättes till 60,5 kg.

  • 32.
    Eriksson, Erik
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system.
    Skog, Christian
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Fluida och mekatroniska system.
    Dimensionering av momentskärmstativ: Materialval samt analys av knäckrisk, fogar och initialsprickor2013Självständigt arbete på grundnivå (kandidatexamen), 10,5 poäng / 16 hpStudentuppsats (Examensarbete)
  • 33.
    Eriksson, Robert
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Chen, Zhe
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    A low cycle fatigue life model for a shot peened gas turbine disc alloy2019Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 124, s. 34-41Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Turbine disks in gas turbines are subjected to cyclic load at high temperature, making, especially the fir tree type blade attachments, susceptible to fatigue. Shot peening of the fir tree attachments may be used to increase the fatigue life by introducing compressive residual stresses. In the current study, both polished and shot peened notched specimens made from alloy 718 were subjected to low cycle fatigue at 450-550 degrees C. The shot peening generally increased the fatigue life, although the effect diminished for high loads. It was shown that the effect of shot peening could be handled as mean stress effects in a life model based on a Smith-Watson-Topper (SWT) type parameter, sigma(max)Delta epsilon/2. A material model which captured the mean stress was set up to get the SWT parameter at the notch root. It was shown that thermal relaxation of residual stresses and initial strain hardening from cold work could be excluded from the finite element analysis used to establish the mean stress; this since the plasticity in the first cycle dominated the plastic deformation of the specimen. Overall, the SWT-based life model worked satisfactorily. However, the prediction of correct mean stresses at 550 degrees C proved somewhat difficult as the degree of mean stress relaxation at this temperature varies widely in available literature data.

  • 34.
    Ewest, D.
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten. Siemens Ind Turbomachinery AB, Sweden.
    Almroth, P.
    Siemens Ind Turbomachinery AB, Sweden.
    Sjodin, B.
    Siemens Ind Turbomachinery AB, Sweden.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Moverare, Johan
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    A modified compliance method for fatigue crack propagation applied on a single edge notch specimen2016Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 92, s. 61-70Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Crack length measurements with high accuracy are often difficult to achieve during fatigue crack propagation testing under non-isothermal conditions. In this work a modified approach to the compliance method defined in e.g. ASTM E647 is described, which is better suited for high loads, varying temperatures and for taking the scatter in Youngs modulus into account. A numerical finite element study is performed for a single edge notch specimen, to investigate the influence of initiation locations on the accuracy of the method. The change in cracked area versus change in stiffness for three different cases are numerically shown to collapse to one curve, i.e. the result is not significantly affected by how the crack is initiated. The numerical study is compared to results from two experiments using different materials, with heat tinting during the tests for extracting snapshots of the crack fronts. A good agreement between the experiments and the numerical study is shown. A new compliance curve and a new geometry function for the stress intensity factor is proposed for the single edge notch specimen. (C) 2016 Elsevier Ltd. All rights reserved.

  • 35.
    Ewest, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Modelling and experimental evaluation of non-linear fatigue crack propagation in a ductile superalloy2016Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Fatigue life evaluation is an important part in the design process of an industrial gas turbine. The fatigue life can be divided into crack initiation and crack propagation, and not to address the crack propagation part usually yields a non-conservative and overcomplicated design. Historically a lot of attention has been directed towards the crack initiation, but the crack propagation part in an industrial gas turbine context has not been given the same attention due to limitations in theoretical modelling, lack of test possibilities and that the design requirements have been fulfilled within the initiation life. However, with the need to reduce service down time and to improve performance, the crack propagation life needs to be further accounted for. As an example, cracks that emerge from notches or other stress concentrations grow under non-elastic conditions, which cannot be modelled with linear theories.

    In this Licentiate of Engineering thesis a non-linear approach is put forward in which the plastic contribution in fatigue crack propagation is addressed and accounted for. The theoretical background is not new, but the finite element implementation done was, to the author knowledge, not available. This numerical post processing tool can calculate the non-linear ΔJ value for an arbitrary 2D-geometry. It was used to produce an expression for a non-linear geometry factor used in a simple expression for estimation of ΔJ in a test evaluation context. Room temperature tests were performed on a single notch specimen, under both displacement and force control. The latter were carried out in order to show the behaviour under small scale yielding conditions, while the displacement controlled testing was to show large scale yielding at the beginning of the tests. It was shown that all the test results could be collected in a Paris law type plot with ΔJ if the crack closure effect is taken into account. Furthermore, a study was performed where both a linear and a non-linear approach are applied on the displacement controlled tests. It was concluded that for the studied test series, the linear fatigue fracture parameter ΔK underestimates the crack growth behaviour if the elasto-plastic stresses from the tests are used, hence yielding non-conservative results.

    Since this project focuses on non-linear crack propagation at thermo-mechanical conditions a crack length description is put forward, which simplifies and increases the accuracy of crack length measurements in fatigue crack propagation tests. It has also been shown that irrespectively of the crack initiation location in a single edge notch specimen the data fall on one curve, meaning that no care has to be taken regarding this aspect when evaluating crack length with the modified compliance method put forward in Paper III.

    This Licentiate of Engineering thesis consists of two parts, where Part I gives an introduction to the subject, while Part II consists of three papers.

    Delarbeten
    1. Fatigue crack propagation in a ductile superalloy at room temperature and extensive cyclic plastic flow
    Öppna denna publikation i ny flik eller fönster >>Fatigue crack propagation in a ductile superalloy at room temperature and extensive cyclic plastic flow
    Visa övriga...
    2015 (Engelska)Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 80, s. 40-49Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Fatigue crack propagation experiments under both force and displacement control have been performed on the wrought superalloy Haynes 230 at room temperature, using a single edge notched specimen. The force controlled tests are nominally elastic, and the displacement controlled tests have nominally large plastic hysteresis at the beginning of the tests, but saturates towards linear elastic conditions as the crack grows. As some tests are in the large scale yielding regime, a non-linear fracture mechanics approach is used to correlate crack growth rates versus the fracture parameter Delta J. It is shown that crack closure must be accounted for, to correctly model the crack growth seen in all the tests in a unified manner. For the force controlled small scale yielding tests the Newman crack closure model was used. The Newman equation is however not valid for large nominal cyclic plasticity, instead the crack closure in the displacement controlled tests is extracted from the test data. A good agreement between all tests is shown, when closure is accounted for and effective values of Delta J are used.

    Ort, förlag, år, upplaga, sidor
    ELSEVIER SCI LTD, 2015
    Nyckelord
    Fatigue crack propagation; Haynes 230; Large scale yielding; Cyclic J-integral or Delta J; Crack closure
    Nationell ämneskategori
    Teknisk mekanik
    Identifikatorer
    urn:nbn:se:liu:diva-122045 (URN)10.1016/j.ijfatigue.2015.04.006 (DOI)000360596500005 ()
    Anmärkning

    Funding Agencies|Siemens Industrial Turbomachinery AB, Finspang, Sweden

    Tillgänglig från: 2015-12-18 Skapad: 2015-10-19 Senast uppdaterad: 2017-12-01
    2. Comparison between linear and non-linear fracture mechanics analysis of experimental data for the ductile superalloy Haynes 230
    Öppna denna publikation i ny flik eller fönster >>Comparison between linear and non-linear fracture mechanics analysis of experimental data for the ductile superalloy Haynes 230
    Visa övriga...
    2016 (Engelska)Ingår i: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 138, nr 6, s. 062101-1-062101-7Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    With increasing use of renewable energy sources, an industrial gas turbine is often a competitive solution to balance the power grid. However, life robustness approaches for gas turbine components operating under increasingly cyclic conditions are a challenging task. Ductile superalloys, as Haynes 230, are often used in stationary gas turbine hot parts such as combustors. The main load for such components is due to nonhomogeneous thermal expansion within or between parts. As the material is ductile, there is considerable redistribution of stresses and strains due to inelastic deformations during the crack initiation phase. Therefore, the subsequent crack growth occurs through a material with significant residual stresses and strains. In this work, fatigue crack propagation experiments, including the initiation phase, have been performed on a single edge notched specimen under strain controlled conditions. The test results are compared to fracture mechanics analyses using the linear ΔK and the nonlinear ΔJ approaches, and an attempt to quantify the difference in terms of a life prediction is made. For the tested notched geometry, material, and strain ranges, the difference in the results using ΔKeff or ΔJeff is larger than the scatter seen when fitting the model to the experimental data. The largest differences can be found for short crack lengths, when the cyclic plastic work is the largest. The ΔJ approach clearly shows better agreement with the experimental results in this regime.

    Ort, förlag, år, upplaga, sidor
    ASME Press, 2016
    Nationell ämneskategori
    Teknisk mekanik Annan materialteknik
    Identifikatorer
    urn:nbn:se:liu:diva-126576 (URN)10.1115/1.4031712 (DOI)000374713500010 ()
    Anmärkning

    Funding agencies: Siemens Industrial Turbomachinery AB, Finspang, Sweden

    Tillgänglig från: 2016-03-30 Skapad: 2016-03-30 Senast uppdaterad: 2017-11-30
  • 36.
    Ewest, Daniel
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten. Siemens Ind Turbomachinery AB,Finspång, Sweden.
    Almroth, P.
    Siemens Ind Turbomachinery AB, Finspång, Sweden.
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Sjodin, B.
    Siemens Ind Turbomachinery AB, Finspång, Sweden.
    Fatigue crack propagation in a ductile superalloy at room temperature and extensive cyclic plastic flow2015Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 80, s. 40-49Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fatigue crack propagation experiments under both force and displacement control have been performed on the wrought superalloy Haynes 230 at room temperature, using a single edge notched specimen. The force controlled tests are nominally elastic, and the displacement controlled tests have nominally large plastic hysteresis at the beginning of the tests, but saturates towards linear elastic conditions as the crack grows. As some tests are in the large scale yielding regime, a non-linear fracture mechanics approach is used to correlate crack growth rates versus the fracture parameter Delta J. It is shown that crack closure must be accounted for, to correctly model the crack growth seen in all the tests in a unified manner. For the force controlled small scale yielding tests the Newman crack closure model was used. The Newman equation is however not valid for large nominal cyclic plasticity, instead the crack closure in the displacement controlled tests is extracted from the test data. A good agreement between all tests is shown, when closure is accounted for and effective values of Delta J are used.

  • 37.
    Ewest, Daniel
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten. Siemens Ind Turbomachinery AB, Sweden.
    Almroth, P.
    Siemens Ind Turbomachinery AB, Sweden.
    Sjodin, B.
    Siemens Ind Turbomachinery AB, Sweden.
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Isothermal and thermomechanical fatigue crack propagation in both virgin and thermally aged Haynes 2302019Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 120, s. 96-106Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Fatigue crack propagation tests under both isothermal and non-isothermal thermomechanical fatigue conditions have been performed on wrought Haynes 230, a ductile combustor material. A number of specimens were thermally aged by pre-straining and subsequent furnace exposure for 3000 h at 600 degrees C. The tests were performed both under load and strain control, between room temperature and 600 degrees C. The thermally aged notched specimens show a decrease in the crack initiation life, similar to results previously reported for smooth test specimens at room temperature. For the crack growth rates, the effects of thermal ageing were less pronounced than for crack initiation. Further, the tests have been simulated using the finite element method to calculate the crack driving force, where the plasticity induced crack closure is handled with a full history description. A temperature dependent linear kinematic hardening plasticity law has been adopted for describing the material behaviour between room temperature and 600 degrees C. A post-processing tool was used in which the plasticity induced crack opening level was calculated, followed by a calculation of the effective Delta J range for each crack length. The adopted procedure yields good correlation between the different tests, under both isothermal and non-isothermal conditions.

  • 38.
    Ewest, Daniel
    et al.
    Siemens Industrial Turbomachinery AB, Finspång, Sweden .
    Almroth, Per
    Siemens Industrial Turbomachinery AB, Finspång, Sweden .
    Sjödin, Björn
    Siemens Industrial Turbomachinery AB, Finspång, Sweden .
    Leidermark, Daniel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Comparison between linear and non-linear fracture mechanics analysis of experimental data for the ductile superalloy Haynes 2302016Ingår i: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 138, nr 6, s. 062101-1-062101-7Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    With increasing use of renewable energy sources, an industrial gas turbine is often a competitive solution to balance the power grid. However, life robustness approaches for gas turbine components operating under increasingly cyclic conditions are a challenging task. Ductile superalloys, as Haynes 230, are often used in stationary gas turbine hot parts such as combustors. The main load for such components is due to nonhomogeneous thermal expansion within or between parts. As the material is ductile, there is considerable redistribution of stresses and strains due to inelastic deformations during the crack initiation phase. Therefore, the subsequent crack growth occurs through a material with significant residual stresses and strains. In this work, fatigue crack propagation experiments, including the initiation phase, have been performed on a single edge notched specimen under strain controlled conditions. The test results are compared to fracture mechanics analyses using the linear ΔK and the nonlinear ΔJ approaches, and an attempt to quantify the difference in terms of a life prediction is made. For the tested notched geometry, material, and strain ranges, the difference in the results using ΔKeff or ΔJeff is larger than the scatter seen when fitting the model to the experimental data. The largest differences can be found for short crack lengths, when the cyclic plastic work is the largest. The ΔJ approach clearly shows better agreement with the experimental results in this regime.

  • 39.
    Gade, Jan-Lucas
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Mechanical Properties of Arteries: Identification and Application2019Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [sv]

    I denna licentiatavhandling föreslås en metod för att identifiera mekaniska egenskaper hos artärer in vivo. De mekaniska egenskaperna är kopplade till utvecklingen av hjärt-kärlsjukdomar, och möjligheten att identifiera dessa egenskaper skulle således kunna underlätta diagnostisering, behandling och uppföljning av dessa sjukdomar.

    Den förslagna metoden använder kliniskt mätbara tryck-radie-signaler och löser ett minimeringsproblem för att bestämma sex parametrar som beskriver kärlets mekaniska egenskaper. Artären modelleras som ett homogent, inkompressibelt och spänningsfritt tunnväggigt rör där kärlväggen utgörs av en elastindominerad matris armerad med inbäddade kollagenfibrer.

    För att validera parameteridentifieringen skapas en uppsättning representativa, virtuella artärer med hjälp av finita element. Dessa in silico-artärer baseras på publicerade data för mänsklig bukaorta och används för att generera fiktiva tryckradie-signaler vilka sedan matas in i den förslagna modellen. Genom att parametrar och randvillkor för in silico-artärerna är kända fungerar dessa som en kontroll mot vilka resultatet från parameteridentifieringen kan jämföras. Parametrarna som beskriver den icke trycksatta radien och den elastindominerade matrisen visar god överensstämmelse med de in silico-artärerna för friska kärl. Större diskrepans erhålls för de parametrar som associeras med kollagenet, och den största avvikelsen erhålls för den parameter som beskriver den axiella försträckningen. För artärer med patologiskt lågt elastininnehåll identifieras felaktiga parametrar, men resultatet avslöjar ändå tydligt en sjuk artär.

    De identifierade parametrarna har också använts för att jämföra spänningstillst åndet i membranmodellen och in silico-artäreren. Spänningstillståndet har delats upp i en isotrop och en anisotrop komponent svarande mot, i huvudsak, den elastindominerade matrisen samt kollagenfibrerna. Resultatet visar en mycket god överensstämmelse för bägge komponenterna hos in silico-artärer med låg spänningsgradient genom väggen. Med ökande spänningsgradient försämras dock överensstämmelsen.

    Resultatet visar att den förslagna metoden är kapabel att identifiera adekvata parametrar och att förutsäga spänningskomponenterna i en frisk aorta.

    Delarbeten
    1. An in vivo parameter identification method for arteries: numerical validation for the human abdominal aorta
    Öppna denna publikation i ny flik eller fönster >>An in vivo parameter identification method for arteries: numerical validation for the human abdominal aorta
    2019 (Engelska)Ingår i: Computer Methods in Biomechanics and Biomedical Engineering, ISSN 1025-5842, E-ISSN 1476-8259, s. 426-441Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    A method for identifying mechanical properties of arterial tissue in vivo is proposed in this paper and it is numerically validated for the human abdominal aorta. Supplied with pressure-radius data, the method determines six parameters representing relevant mechanical properties of an artery. In order to validate the method, 22 finite element arteries are created using published data for the human abdominal aorta. With these in silico abdominal aortas, which serve as mock experiments with exactly known material properties and boundary conditions, pressure-radius data sets are generated and the mechanical properties are identified using the proposed parameter identification method. By comparing the identified and pre-defined parameters, the method is quantitatively validated. For healthy abdominal aortas, the parameters show good agreement for the material constant associated with elastin and the radius of the stress-free state over a large range of values. Slightly larger discrepancies occur for the material constants associated with collagen, and the largest relative difference is obtained for the in situ axial prestretch. For pathological abdominal aortas incorrect parameters are identified, but the identification method reveals the presence of diseased aortas. The numerical validation indicates that the proposed parameter identification method is able to identify adequate parameters for healthy abdominal aortas and reveals pathological aortas from in vivo-like data.

    Ort, förlag, år, upplaga, sidor
    Taylor & Francis, 2019
    Nyckelord
    In vivo, parameter identification, abdominal aorta, in silico, finite element method, validation
    Nationell ämneskategori
    Övrig annan teknik
    Identifikatorer
    urn:nbn:se:liu:diva-155056 (URN)10.1080/10255842.2018.1561878 (DOI)000466370800009 ()30806081 (PubMedID)2-s2.0-85062322494 (Scopus ID)
    Forskningsfinansiär
    Vetenskapsrådet, 21-2014-4165
    Tillgänglig från: 2019-03-11 Skapad: 2019-03-11 Senast uppdaterad: 2019-08-29Bibliografiskt granskad
  • 40.
    Ganghoffer, J. F.
    et al.
    Ecole des Mines, Nancy.
    Gautier, E.
    Ecole des Mines, Nancy.
    Denis, S.
    Ecole des Mines, Nancy.
    Simon, A.
    Ecole des Mines, Nancy.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Hållfasthetslära. Linköpings universitet, Tekniska högskolan.
    Sjöström, Sören
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Hållfasthetslära. Linköpings universitet, Tekniska högskolan.
    Micromechanical simulation of a martensitic transformation by Finite Elements1991Ingår i: Journal de Physique IV: Colloque, ISSN 1155-4339, E-ISSN 1764-7177, Vol. 1, s. C4-77-C4-82Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A micromechanical model describing the martensitic transformation on the grain scale has been developed, using Finite Elements. First results gained from the simulation illustrate how the morphological evolution within the grain is directly controlled by the internal stress state. The reversible and irreversible part of transformation "plasticity" strain and their evolution with the transformation can then be obtained from these calculations.

  • 41.
    Ganghoffer, J.F.
    et al.
    Laboratoire de Science et Génie des Matériaux Métalliques, Ecole des Mines, Parc de Saurupt, F-54042 Nancy cedex, France.
    Denis, S.
    Laboratoire de Science et Génie des Matériaux Métalliques, Ecole des Mines, Parc de Saurupt, F-54042 Nancy cedex, France.
    Gautier, E.
    Laboratoire de Science et Génie des Matériaux Métalliques, Ecole des Mines, Parc de Saurupt, F-54042 Nancy cedex, France.
    Simon, A.
    Laboratoire de Science et Génie des Matériaux Métalliques, Ecole des Mines, Parc de Saurupt, F-54042 Nancy cedex, France.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Sjöström, Sören
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Micromechanical simulation of martensitic transformation by Finite Elements1991Ingår i: Journal de Physique IV, ISSN 1155-4339, Vol. 1, s. C4-77-C4-82Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A micromechanical model describing the martensitic transformation on the grain scale has been developed, using Finite Elements. First results gained from the simulation illustrate how the morphological evolution within the grain is directly controlled by the internal stress state. The reversible and irreversible part of transformation "plasticity" strain and their evolution with the transformation can then be obtained from these calculations.

  • 42.
    Ganghoffer, J.F.
    et al.
    ICSI, 15, Rue Jean Starcky, BP 2478, 68057 Mulhouse Cedex, France.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    A micromechanical model of the martensitic transformation1998Ingår i: Mechanics of Materials, ISSN 0167-6636, Vol. 27, nr 3, s. 125-144Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A micromechanical model of the martensitic transformation at the grain scale has been established, considering the more specific case of ferrous alloys. The transformation proceeds through the formation of successive variants of the product phase within a unit cell representative of a grain; interactions between neighbouring grains are simulated by the choice of periodic boundary conditions. From a thermodynamical analysis, a selection rule for the order and orientation of the forming martensitic variants has been established, based on internal stresses anisotropy. These concepts have been implemented into a two-dimensional finite element simulation of the transformation, considering an elastoplastic behaviour of both parent and product phases. Morphological and crystallographical features of the transformation are considered: one variant consists of a thin layer of elements within the mesh that can form with four possible discrete orientations. Simulation results show the development of the plate pattern as a combination of the influence of both external load and internal stresses built during the progress of the transformation. These are related to global evolutions of transformation plasticity vs. transformation progress. Comparison with experiments show a similar form of the evolutions of the total strain; however, the model overestimates the strain levels. The possible reasons for this discrepancy are discussed.

  • 43.
    Ganghoffer, J.F.
    et al.
    Ecole des Mines, Nancy.
    Simonsson, Kjell
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Hållfasthetslära. Linköpings universitet, Tekniska högskolan.
    Denis, S.
    Ecole des Mines, Nancy.
    Gautier, E.
    Ecole des Mines, Nancy.
    Sjöström, Sören
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Hållfasthetslära. Linköpings universitet, Tekniska högskolan.
    Simon, A.
    Ecole des Mines, Nancy.
    Martensitic transformation plasticity simulations by finite elements1994Ingår i: Journal de Physique IV: Colloque, ISSN 1155-4339, E-ISSN 1764-7177, Vol. 4, s. C3-215-C3-220Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The mechanical behaviour associated to the martensitic transformation has been modelled using a 2D FE description. The martensite variants are constituted of different elements of the mesh and four different variants are allowed to transform in the grain. The transformation progress is prescribed using a thermodynamical criterion based on the maximal work associated to the variant formation. Transformation plasticity deformation and plates orientation patterns are obtained for three stress levels. These results are discussed in regard to the model used and the physical parameters introduced in the model.

  • 44.
    Gigan, Gael
    et al.
    Chalmers Univ Technol, Sweden.
    Norman, Viktor
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska fakulteten.
    Ahlström, Johan
    Chalmers Univ Technol, Sweden.
    Vernersson, Tore
    Chalmers Univ Technol, Sweden; AF Ind AB, Sweden.
    Thermomechanical fatigue of grey cast iron brake discs for heavy vehicles2019Ingår i: Proceedings of the Institution of mechanical engineers. Part D, journal of automobile engineering, ISSN 0954-4070, E-ISSN 2041-2991, Vol. 233, nr 2, s. 453-467Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    The development of fatigue life assessment models for vehicle components exposed to thermomechanical fatigue supports the establishing of adequate maintenance intervals that neither cause unnecessary vehicle downtime, nor jeopardize the function of the components. In modern automotive applications, braking is closely related to safety and is commonly performed with disc brakes. Failure here may result in structural damage or even breakdown and loss of lives. In the present work, the cyclic response of grey cast iron is analysed and the fatigue life of brake discs made from this material is studied by use of four different fatigue life assessment models: the Smith-Watson-Topper model, the Coffin-Manson model and two mechanism-based damage models. Results from isothermal and thermomechanical experiments on uniaxially loaded specimens are used for calibration of the models. Finally, the models are used to assess the life of a brake disc for a simulated brake dynamometer experiment. It is found that the fatigue model parameters that are calibrated using different sets of isothermal uniaxial test data show a substantial spread. A comparison with results from full-scale brake rig experiments shows that predictions by any of the models that have been calibrated using data from a well-designed thermomechanical test are in reasonable agreement with the estimated crack initiation phase for actual brake disc lives. It can be concluded that it is not sufficient to calibrate the studied fatigue life models using isothermal uniaxial tests for predictions of thermomechanical fatigue lives.

  • 45.
    Ginebre, Emmanuel
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik.
    Geometry-dependence of the adhesive strength of biomimetic, micropatterned surfaces2012Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    Pressure sensitive adhesive surfaces are often inspired by nature. Miming the toe-surface of gecko, engineered surfaces made of thousands of micro-pillars show promising adhesive properties. This surfaces, covered with cylindrical pillars arranged into a pattern have adhesive properties greatly dependent on the geometrical characteristics. In this thesis, have been studied successively two models of micro-patterned surfaces, one two-dimensional, the other in three-dimensional using a FEM tool. Varying geometry parameters, has been determined optimal geometries to improve adhesive strength on these biomimetic, micropatterned surfaces. This study concludes to the non-adaptability of one-level scale micropatterned surface to large area of adhesion, to the strong advantage from the point of adhesion per contact area for high aspect ratio at each level of the geometry and study the opportunity of hierarchical structures. Some further suggestions of improvements to adhesion properties are discussed in the final chapter.

  • 46.
    Govik, Alexander
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Hållfasthetslära. Linköpings universitet, Tekniska högskolan.
    Finite Element Analysis of Sheet Metal Assemblies: Prediction of Product Performance Considering the Manufacturing Process2014Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    This thesis concerns the development of methodologies to be used to simulate complete manufacturing chains of sheet components and the study of how different mechanical properties propagate and influence succeeding component performance.

    Since sheet metal assemblies are a major constituent of a wide range of products it is vital to develop methodologies that enable detailed evaluation of assembly designs and manufacturing processes. The manufacturing process influences several key aspects of a sheet metal assembly, aspects such as shape fulfilment, variation and risk of material failure.

    Developments in computer-aided engineering and computational resources have made simulation-based process and product development efficient and useful since it allows for detailed, rapid evaluation of the capabilities and qualities of both process and product. Simulations of individual manufacturing processes are useful, but greater benefits can be gained by studying the complete sequence of a product's manufacturing processes. This enables evaluation of the entire manufacturing process chain, as well as the final product. Moreover, the accuracy of each individual manufacturing process simulation is improved by establishing appropriate initial conditions, including inherited material properties.

    In this thesis, a methodology of sequentially simulating each step in the manufacturing process of a sheet metal assembly is presented. The methodology is thoroughly studied using different application examples with experimental validation. The importance of information transfer between all simulation steps is also studied. Furthermore, the methodology is used as the foundation of a new approach to investigate the variation of mechanical properties in a sheet metal assembly. The multi-stage manufacturing process of the assembly is segmented, and stochastic analyses of each stage is performed and coupled to the succeeding stage in order to predict the assembly's final variation in properties.

    Two additional studies are presented where the methodology of chaining manufacturing processes is utilised. The influence of the dual phase microstructure on non-linear strain recovery is investigated using a micromechanical approach that considers the annealing process chain. It is vital to understand the non-linear strain recovery in order to improve springback prediction. In addition, the prediction of fracture in a dual phase steel subjected to non-linear straining is studied by simulating the manufacturing chain and subsequent stretch test of a sheet metal component.

    Delarbeten
    1. Finite element simulation of the manufacturing process chain of a sheet metal assembly
    Öppna denna publikation i ny flik eller fönster >>Finite element simulation of the manufacturing process chain of a sheet metal assembly
    2012 (Engelska)Ingår i: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 212, nr 7, s. 1453-1462Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    An increasing number of components in automotive structures are today made from advanced high strength steel (AHSS). Since AHSS demonstrates more severe springback behaviour than ordinary mild steels, it requires more efforts to meet the design specification of the stamped parts. Consequently, the physical fine tuning of the die design and the stamping process can be time consuming. The trial-and-error development process may be shortened by replacing most of the physical try-outs with finite element (FE) simulations of the forming process, including the springback behaviour. Still it can be hard to identify when a stamped part will lead to an acceptable assembly with respect to the geometry and the residual stress state. In part since the assembling process itself will distort the components. To resolve this matter it is here proposed to extend the FE-simulation of the stamping process, to also include the first level sub-assembly stage. In this study a methodology of sequentially simulating each step in the manufacturing process of an assembly is proposed. Each step of the proposed methodology is described, and a validation of the prediction capabilities is performed by comparing with a physically manufactured assembly. The assembly is composed of three sheet metal components made from DP600 steel which are joined by spot welding. The components are designed to exhibit severe springback behaviour in order to put both the forming and subsequent assembling simulations to the test. The work presented here demonstrates that by using virtual prototyping it is possible to predict the final shape of an assembled structure.

    Ort, förlag, år, upplaga, sidor
    Elsevier, 2012
    Nyckelord
    Finite element simulation, Assembly, Sheet metal, Forming, Springback
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-77853 (URN)10.1016/j.jmatprotec.2012.02.012 (DOI)000304020800001 ()
    Anmärkning

    Funding Agencies|Swedish foundation for strategic research||ProViking programme||

    Tillgänglig från: 2012-05-31 Skapad: 2012-05-31 Senast uppdaterad: 2017-12-07Bibliografiskt granskad
    2. The effects of forming history on sheet metal assembly
    Öppna denna publikation i ny flik eller fönster >>The effects of forming history on sheet metal assembly
    2014 (Engelska)Ingår i: International Journal of Material Forming, ISSN 1960-6206, E-ISSN 1960-6214, Vol. 7, nr 3, s. 305-316Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    As demand for faster product development increases, physical prototypes are replaced by virtual prototypes. By using finite element simulations to evaluate the functional behaviour of the product as well as its manufacturing process, more design alternatives can be evaluated while a considerably smaller number of physical prototypes are needed. As sheet metal assemblies are common in a wide range of products, reliable methods for predicting their properties are necessary. By sequentially simulating the complete manufacturing process chain of an assembly, early predictions concerning the geometry and material properties of the assembly can be made.

    In this study a simulation-based sensitivity study is performed in order to investigate the influence of the forming history on the predictions of assembly properties. In the study, several simulations of the assembly stage are performed in which different types of forming histories are retained from the forming stage. The simulations of the assembly stage will range from a case with linear elastic conditions without forming history, to a case with the full forming history state and consistent material modelling throughout all simulations. It is found that the residual stress state is the most influential history variable from the forming stage. Especially for more complex geometries in which large residual stresses can be retained.

    Ort, förlag, år, upplaga, sidor
    Springer, 2014
    Nyckelord
    Finite element simulation, Assembly, Sheet metal, Forming, History variables, Chaining of manufacturing processes
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-78765 (URN)10.1007/s12289-013-1128-9 (DOI)000338323600004 ()
    Anmärkning

    On the day of the defence date of the Ph.D. thesis the status of this article was Manuscript.

    Tillgänglig från: 2012-06-20 Skapad: 2012-06-20 Senast uppdaterad: 2017-12-07Bibliografiskt granskad
    3. A study of the unloading behaviour of dual phase steel
    Öppna denna publikation i ny flik eller fönster >>A study of the unloading behaviour of dual phase steel
    2014 (Engelska)Ingår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 602, s. 119-126Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    It is important to understand the strain recovery of a steel sheet in order to predict its springback behaviour. During strain recovery, the stress–strain relation is non-linear and the resulting unloading modulus is decreased. Moreover, the unloading modulus will degrade with increasing plastic pre-straining. This study aims at adding new knowledge on these phenomena and the mechanisms causing them. The unloading behaviour of the dual-phase steel DP600 is characterised experimentally and finite element (FE) simulations of a representative volume element (RVE) of the microstructure are performed. The initial stress and strain state of the micromechanical FE model is found by a simplified simulation of the annealing processes. It is observed from the experimental characterisation that the decrease of the initial stiffness of the unloading is the main reason for the degrading unloading modulus. Furthermore, the developed micromechanical FE model exhibits non-linear strain recovery due to local plasticity caused by interaction between the two phases.

    Ort, förlag, år, upplaga, sidor
    Elsevier, 2014
    Nyckelord
    Micromechanics; Representative volume element; Dual phase steel; Unloading modulus; Non-linear recovery
    Nationell ämneskategori
    Metallurgi och metalliska material Teknisk mekanik
    Identifikatorer
    urn:nbn:se:liu:diva-106318 (URN)10.1016/j.msea.2014.02.069 (DOI)000335098500015 ()
    Tillgänglig från: 2014-05-05 Skapad: 2014-05-05 Senast uppdaterad: 2017-12-05Bibliografiskt granskad
    4. Prediction of fracture in a dual-phase steel subjected to non-linear straining
    Öppna denna publikation i ny flik eller fönster >>Prediction of fracture in a dual-phase steel subjected to non-linear straining
    2014 (Engelska)Ingår i: Journal of Materials Processing Technology, ISSN 0924-0136, E-ISSN 1873-4774, Vol. 214, nr 11, s. 2748-2758Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    In this work, selected fracture criteria are applied to predict the fracture of dualphase steel subjected to non-linear strain paths. Furthermore, the effects of manufacturing history are studied. Four fracture criteria were calibrated in three tests using standard specimens. The fracture criteria were first validated in the circular Nakajima test. A second validation test case was included in order to validate fracture prediction for non-linear strain paths. In this test a sheet metal component was manufactured and subsequently stretched until it fractured. All fracture criteria included in this study predict fracture during the Nakajima test with reasonable accuracy. In the second validation test however, the different fracture criteria show considerable diversity in accumulated damage during manufacturing which caused substantial scatter of the fracture prediction in the subsequent stretching. This shows that manufacturing history influences the prediction of fracture.

    Ort, förlag, år, upplaga, sidor
    Elsevier, 2014
    Nyckelord
    Sheet metal failure, high strength steels, forming limits, non-linear strain paths, forming history
    Nationell ämneskategori
    Maskinteknik
    Identifikatorer
    urn:nbn:se:liu:diva-105211 (URN)10.1016/j.jmatprotec.2014.05.028 (DOI)000340300400059 ()
    Anmärkning

    Funders: SSF ProViking project entitled "SuperLight Steel Structures"

    Tillgänglig från: 2014-03-13 Skapad: 2014-03-13 Senast uppdaterad: 2017-12-05
    5. Stochastic analysis of a sheet metal assembly considering its manufacturing process
    Öppna denna publikation i ny flik eller fönster >>Stochastic analysis of a sheet metal assembly considering its manufacturing process
    2014 (Engelska)Manuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    In order to accurately predict the mechanical properties of a sheet metal assembly it has been shown important to account for how the geometry and material properties are affected by the manufacturing process. It is also of a great interest to predict the variations of important responses, and how these variations depend on the manufacturing process.

    In this study, the variation of properties during the multi-stage manufacturing process of a sheet metal assembly is evaluated and the variability of a response due to loading is studied. A methodology to investigate how variations evolve during the assembling process is presented. The multi-stage assembling process is virtually segmented, such that stochastic analyses of each process stage are performed and coupled to succeeding stages in order to predict the variation in properties of the final assembly. The methodology is applied to an industrial assembly and experimental validations have been conducted. The prediction of the geometry of the final assembly is in good agreement with the experimental results, while the prediction of the variation of this geometry is in fair agreement.

    Nyckelord
    Finite element simulation, Assembly, Sheet metal, Forming, Monte Carlo analysis, Chaining of manufacturing processes
    Nationell ämneskategori
    Metallurgi och metalliska material Teknisk mekanik
    Identifikatorer
    urn:nbn:se:liu:diva-106636 (URN)
    Tillgänglig från: 2014-05-16 Skapad: 2014-05-16 Senast uppdaterad: 2014-05-16Bibliografiskt granskad
  • 47.
    Govik, Alexander
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Hållfasthetslära. Linköpings universitet, Tekniska högskolan.
    Nilsson, Larsgunnar
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Hållfasthetslära. Linköpings universitet, Tekniska högskolan.
    Moshfegh, Ramin
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Energisystem. Linköpings universitet, Tekniska högskolan.
    Stochastic analysis of a sheet metal assembly considering its manufacturing process2014Manuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    In order to accurately predict the mechanical properties of a sheet metal assembly it has been shown important to account for how the geometry and material properties are affected by the manufacturing process. It is also of a great interest to predict the variations of important responses, and how these variations depend on the manufacturing process.

    In this study, the variation of properties during the multi-stage manufacturing process of a sheet metal assembly is evaluated and the variability of a response due to loading is studied. A methodology to investigate how variations evolve during the assembling process is presented. The multi-stage assembling process is virtually segmented, such that stochastic analyses of each process stage are performed and coupled to succeeding stages in order to predict the variation in properties of the final assembly. The methodology is applied to an industrial assembly and experimental validations have been conducted. The prediction of the geometry of the final assembly is in good agreement with the experimental results, while the prediction of the variation of this geometry is in fair agreement.

  • 48.
    Govik, Alexander
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Hållfasthetslära. Linköpings universitet, Tekniska högskolan.
    Rentmeester, Rikard
    Saab AB, Linköping, Sweden.
    Nilsson, Larsgunnar
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Hållfasthetslära. Linköpings universitet, Tekniska högskolan.
    A study of the unloading behaviour of dual phase steel2014Ingår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 602, s. 119-126Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    It is important to understand the strain recovery of a steel sheet in order to predict its springback behaviour. During strain recovery, the stress–strain relation is non-linear and the resulting unloading modulus is decreased. Moreover, the unloading modulus will degrade with increasing plastic pre-straining. This study aims at adding new knowledge on these phenomena and the mechanisms causing them. The unloading behaviour of the dual-phase steel DP600 is characterised experimentally and finite element (FE) simulations of a representative volume element (RVE) of the microstructure are performed. The initial stress and strain state of the micromechanical FE model is found by a simplified simulation of the annealing processes. It is observed from the experimental characterisation that the decrease of the initial stiffness of the unloading is the main reason for the degrading unloading modulus. Furthermore, the developed micromechanical FE model exhibits non-linear strain recovery due to local plasticity caused by interaction between the two phases.

  • 49.
    Gunnarsson, Pontus
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Mekanik och hållfasthetslära. Linköpings universitet, Tekniska fakulteten.
    Methods to Predict Structural Response due to Random Sound Pressure Fields2015Självständigt arbete på avancerad nivå (masterexamen), 20 poäng / 30 hpStudentuppsats (Examensarbete)
    Abstract [en]

    To predict structural responses due to random sound pressure fields are of great interest within many fields of aircraft development, particularly within acoustic fatigue problems and definition of vibration requirements.  Today there exist some methods to quantify sound pressure fields affecting the air-fighters. Some of them are considered to be expensive, time consuming or with high computational cost. Examples of this would be to measure a real flight, produce data from wind tunnels, use Computational Fluid Dynamics (CFD) or obtain data from an engineering database. Once the sound pressure levels are known they can be applied as loads to structural models and this is the area studied in this work. To study these problems a new working tool is made using MATLAB. The tool’s main purpose is to give an opportunity to study structural responses caused by random sound pressure fields with different correlation methods.  Because of the complexity of both the sound pressure and different structures of the aircraft a few limitations are considered. The plate is used since this makes is easy to produce different mode shape functions. The mode shape function is an important part in this work as it can be used to create all possible frequency response functions in a structure. Then, to determine a structure response, different methods to produce pressure fields are used. The methods are called correlation-models and five different models are considered: uncorrelated, fully correlated and moving correlated load (MCL) and two empirical models due to the similarity to real sound pressure fields called Turbulent Boundary Layer (TBL) and a diffuse excitation model. To prove the accuracy of the created working tool, an independent FE-solver is used called Abaqus. Abaqus  is  used  to  validate  the  mode  shape-  and  the  frequency  response-fucntions.  Another advantage  with  Abaqus  is  that  the  solver  already  includes  three  of  the  correlation  models  which therefore simplify the verification of the new tool. Finally,  a  simulation  study  is  carried  out  in  order  to  validate  the  MATLAB  functions  and  test  the sensitivity  to  different  correlation  models.  In  order  to  do  this,  the  sound  pressure  field  is  to  be reasonable  approximated  and  therefore  data  from  the  database  ESDU  (acronym  of  Engineering Sciences Data Unit) is used that predicts sound pressure fields for different flight envelopes. In the simulation study all correlation models are compared to TBL due to its sound pressure and here it can be seen that fully correlated loads fails to predict response due to certain modes. On the other hand, the MCL model increases this accuracy for low Mach numbers and even more for high Mach numbers  due  to  its  velocity  dependence.  The  diffuse  model,  which  is  supposed  to  imitate  a  real pressure chamber load, is often believed to be conservative but in this study it can be seen that this is not always the case.

  • 50.
    Gustafsson, David
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Hållfasthetslära. Linköpings universitet, Tekniska högskolan.
    Constitutive and fatigue crack propagation behaviour of Inconel 7182010Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    In this licentiate thesis the work done in the TURBO POWER project Influence of high temperature hold times on the fatigue life of nickel-based superalloys will be presented. The overall objective of this project is to develop and evaluate tools for designing against fatigue in gas turbine applications, with special focus on the nickel-based superalloy Inconel 718. Firstly, the constitutive behaviour of the material has been been studied, where focus has been placed on trying to describe the mean stress relaxation and initial softening of the material under intermediate temperatures. Secondly, the fatigue crack propagation behaviour under high temperature hold times has been studied. Focus has here been placed on investigating the main fatigue crack propagation phenomena with the aim of setting up a basis for fatigue crack propagation modelling.

    This thesis is divided into two parts. The first part describes the general framework, including basic constitutive and fatigue crack propagation behaviour as well as a theoretical background for the constitutive modelling of mean stress relaxation. This framework is then used in the second part, which consists of the four included papers.

    Delarbeten
    1. Fatigue crack growth behaviour of Inconel 718 with high temperature hold times
    Öppna denna publikation i ny flik eller fönster >>Fatigue crack growth behaviour of Inconel 718 with high temperature hold times
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    2010 (Engelska)Ingår i: Procedia Engineering, ISSN 1877-7058, E-ISSN 1877-7058, Vol. 2, nr 1, s. 1095-1104Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    In this work, fatigue crack growth measurements have been made on center-cracked tension specimens of Inconel 718, where the focus has been to observe the effect of high temperature hold times on the fatigue crack growth behaviour of the material. The material testing has been done at three different temperatures, namely 450 degrees C, 550 degrees C and 650 degrees C. All testing were done in an isothermal LCF context with a standard test method for measuring the fatigue crack growth rates.

    Ort, förlag, år, upplaga, sidor
    ELSEVIER SCIENCE BV, 2010
    Nyckelord
    nickel-base superalloys; fatigue crack propagation; Inconel 718
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-58352 (URN)10.1016/j.proeng.2010.03.118 (DOI)000278762900116 ()
    Tillgänglig från: 2010-08-13 Skapad: 2010-08-11 Senast uppdaterad: 2017-12-12Bibliografiskt granskad
    2. Modeling of the Constitutive Behavior of Inconel 718 at Intermediate Temperatures
    Öppna denna publikation i ny flik eller fönster >>Modeling of the Constitutive Behavior of Inconel 718 at Intermediate Temperatures
    2011 (Engelska)Ingår i: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 133, s. 094501-1-094501-4Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    Turbine disks are of large importance to turbine designers as theyare exposed to hot environment and subjected to high loads. Inorder to analyze such components with respect to fatigue crackinitiation, the work generally starts with a rigorous analysis of thefirst few cycles, during which an important stress redistributionwill always take place in an inelastic structure. In this work, thenonlinear kinematic hardening law by Ohno and Wang (1998,“Constitutive Modeling of Cyclic Plasticity With Emphasis onRatchetting,” Int. J. Mech. Sci., 40, pp. 251–261) has been used incombination with an isotropic softening law for describing theinitial stress-strain distribution for strain controlled uniaxial testsof the material Inconel 718. Focus has been placed on finding asimple model with few material parameters and to describe theinitial softening and the comparatively small mean stress relaxationobserved during the material testing. The simulation resultsobtained by using the model fit the experimental resultswell.

    Ort, förlag, år, upplaga, sidor
    ASME, 2011
    Nationell ämneskategori
    Teknisk mekanik
    Identifikatorer
    urn:nbn:se:liu:diva-68035 (URN)10.1115/1.4002913 (DOI)000290494800020 ()
    Tillgänglig från: 2011-05-06 Skapad: 2011-05-06 Senast uppdaterad: 2017-12-11
    3. Influence of high temperature hold times on the fatigue crack propagation in Inconel 718
    Öppna denna publikation i ny flik eller fönster >>Influence of high temperature hold times on the fatigue crack propagation in Inconel 718
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    2011 (Engelska)Ingår i: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 33, nr 11, s. 1461-1469Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    High temperature fatigue crack growth in Inconel 718 has been studied at the temperatures 450 degrees C, 500 degrees C, 550 degrees C and 650 degrees C. The tests were conducted both without hold times and with hold times of different lengths and with a mix of both. Focus has been on quantifying the effect the hold time has upon the crack growth rate and how much it damages the material. Furthermore, it has been investigated how this damage influences the actual cracking behavior, i.e. where in the loading cycle the damage contributes most to the crack growth. This damage is related to the concept of a damaged zone in front of the crack tip. The size of the damaged zone has been derived from the tests and a microscopy study to confirm the findings has also been carried out. It is found that the concept of a damaged zone can be a successful explanatory model for the observed crack growth behavior under high temperature hold time.

    Ort, förlag, år, upplaga, sidor
    Elsevier, 2011
    Nyckelord
    Nickel-base superalloys, Fatigue crack propagation, Inconel 718, Hold times, Grain boundary embrittlement
    Nationell ämneskategori
    Teknik och teknologier
    Identifikatorer
    urn:nbn:se:liu:diva-70317 (URN)10.1016/j.ijfatigue.2011.05.011 (DOI)000293991000006 ()
    Anmärkning
    Funding Agencies|Swedish Energy Agency||Siemens Industrial Turbomachinery AB||Volvo Aero Corporation||Royal Institute of Technology||Tillgänglig från: 2011-09-02 Skapad: 2011-09-02 Senast uppdaterad: 2017-12-08
    4. Hold-time effect on the thermo-mechanical fatigue crack growth behaviour of Inconel 718
    Öppna denna publikation i ny flik eller fönster >>Hold-time effect on the thermo-mechanical fatigue crack growth behaviour of Inconel 718
    2011 (Engelska)Ingår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 528, nr 29-30, s. 8660-8670Artikel i tidskrift (Refereegranskat) Published
    Abstract [en]

    In-phase TMF crack growth testing with different lengths of the hold time at the maximum temperature of 550 °C has been conducted on Inconel 718 specimens. Focus has been on establishing a method for TMF crack growth testing and investigating the effect of high temperature hold times on the TMF crack growth of the material. The tests are compared to isothermal crack propagation tests and show good correlation. It is concluded that the controlling effect of the crack growth is an embrittlement of the material. This embrittlement is related to the concept of a damaged zone active in front of the crack tip. The size of this damaged zone will control the crack propagation rate and therefore it does not matter if the load is cycled under isothermal or TMF conditions.

    Ort, förlag, år, upplaga, sidor
    Elsevier, 2011
    Nyckelord
    TMF, crack growth
    Nationell ämneskategori
    Metallurgi och metalliska material
    Identifikatorer
    urn:nbn:se:liu:diva-71304 (URN)10.1016/j.msea.2011.08.027 (DOI)000296676800046 ()
    Anmärkning
    Funding agencies|Swedish Energy Agency||Siemens Industrial Turbomachinery AB||Volvo Aero Corporation||Royal Institute of Technology||Tillgänglig från: 2011-10-11 Skapad: 2011-10-11 Senast uppdaterad: 2017-12-08
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