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  • 51.
    Ericsson, Torsten
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    The effect of final shaping prior to heat treatment2001Annet (Annet (populærvitenskap, debatt, mm))
  • 52.
    Ericsson, Torsten
    et al.
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Larsson, Cecilia
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Peng, Ru
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Studies of residual stress, microcracks, hardness and microstructure of cold compacted metallic green bodies2003Inngår i: Materials Research Society Symposium Proceedings, ISSN 0272-9172, E-ISSN 1946-4274, Vol. 759, s. 53-64Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The residual stresses have been measured by X-ray and neutron diffraction on PM green bodies manufactured by conventional and high speed compaction of iron powder with and without added copper and brass powder. Compressive residual stresses are present in a thin layer in both top and side surfaces. They are largest in the side surfaces due to plastic deformation of the surface material caused by the friction forces during ejection out of the die. In the interior of the green body residual stresses exist with certain region under compression (periferical regions) and other under tension (more central regions). It is unclear whether mixing iron powder with brass or copper powder leads to considerable phase stresses between the two phases.

  • 53.
    Ericsson, Torsten
    et al.
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Luukkonen, Petri
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Residual stresses in green bodies of steel powder after conventional and high speed compaction2002Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 404-407, s. 77-82Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Residual stresses have been measured in green bodies after conventional compaction at 400 and 530 MPa and after high speed compaction with impact energies of 1400J and. 2200J. The former were rectangular bars and the latter cylinders. The stresses have been measured by X-ray and neutron diffraction. The full width half maximum peak widths were also recorded. :ft was found that all surfaces had compressive residual stresses in the range 5 to 90 MPa, the largest values found on side surfaces that had been deformed in shear during ejection from the die. The presence of lubricant reduces the residual stress values. The powders were basically water atomised iron powder: Hoganas ASC 100.29, Distalloy AE and Pasc.

  • 54.
    Fernadez, R
    et al.
    Dept of Physical Metallurgy CENIM, Madrid.
    Bruno, G
    Institute Laue-Langevin Genoble.
    Peng, Ru
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    Gonzalez-Doncel, G
    Dept of Physical Metallurgy CENIM, Madrid.
    Effect of Plastic Deformation on the Microscopic Residual Stresses in 6061Al-15vol%SiCw Composites2003Inngår i: THERMEC,2003, 2003Konferansepaper (Fagfellevurdert)
  • 55.
    Fernandez, R
    et al.
    Dept of Physical Metallurgy Centro Nacional de Invesigaciones Metalurgicas, Madrid.
    Bruno, G
    Institut Lau-Langevin Grenoble.
    Peng, Ru
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    Gonzalez-Doncel, G
    Dept of Physical Metallurgy Centro Nacional de Investigaciones Metalurgicas, Madrid.
    Effect of heat treatments on the residual stress state of 60661Al-15%SiCw composite2003Inngår i: Meca Sens,2003, 2003Konferansepaper (Fagfellevurdert)
  • 56.
    Gibmeier, Jens
    et al.
    Institute of Materials Technology University of Kassel.
    Peng, Ru
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    Odén, Magnus
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    Scholtes, B
    Institute of Materials Technology University of Kassel.
    Residual Stress Distributions around Clinched Joints2002Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 404-407, s. 617-622Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Clinching is a mechanical press joining method, which has become of growing interest in recent time since it has the potential to replace other conventional joining methods like e.g. spot welding. However, there still exists a lack of knowledge in terms of the mechanical behavior of clinched joints under quasistatic or cyclic loading. For that reason clinching is usually used for applications in structures which are not subjected to external loads. In particular the residual stress distribution in the vicinity of clinched joints and its influence on the mechanical behavior of the joints is unknown. Here diffraction methods are used for the determination of characteristic residual stress distributions in undismantled clinched samples. A combined residual stress determination by X-ray and neutron diffraction has been used to get a well-founded assessment of the residual stress distributions in the immediate vicinity of clinched joints. The residual stress analysis is supplemented by characterizations of the microstructures and the mechanical properties of single clinched joints. Two materials with different strain hardening behavior were used for clinching, a micro alloyed steel (ZStE340) and a non age hardenable aluminum base alloy (AlMg5). In addition two different common clinching techniques were applied - the TOX- [5] and the Eckold-technique [6]. Characteristic residual stress distributions were found for the combinations of clinching techniques and joined sheet materials investigated here. It has been determined that the clinching process induces predominantly compressive residual stresses inside the clinch and in the immediate vicinity of the clinch. The near surface residual stress distributions determined by X-ray diffraction measurements tend to reveal somewhat different residual stresses than measured by neutron diffraction, indicating a possible stress gradient through the sheet thickness. Further evaluation of the FWHM-values of the respective interference profiles shows that for both clinching techniques the largest amount of plastic deformation occurs in the clinch lock region.

  • 57.
    Gibmeier, Jens
    et al.
    Institute of Materials Technology University of Kassel.
    Rode, Nils
    Institute of Materials Technology University of Kassel.
    Peng, Ru
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    Odén, Magnus
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    Scholtes, B
    Institute of Materials Technology University of Kassel.
    Residual stress in clinched joints of metals2002Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Diffraction methods are used for the determination of characteristic residual stress (RS) distributions in undismantled clinched samples for the assessment of the influence of RS on the mechanical behaviour of clinched joints. While X-ray diffraction enables merely the determination of near-surface RS distributions, the higher penetration depth of neutron radiation allows the determination of triaxial RS states inside the material. In addition, the complex geometry of clinched joints restricts the application of X-ray RS analysis. Therefore a combined RS determination by X-ray and neutron diffraction has been used to obtain an expressive assessment of the RS distributions in the immediate vicinity of clinched joints. Two different materials with different mechanical behaviour were used for clinching, as well as two different common clinching techniques.

  • 58.
    Hammersberg, Peter
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    Mångård, Måns
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    Optimal Computerized Tomography Performance1999Inngår i: Computerized Tomography for Industrial Application and Image Processing in Radiology,1999, 1999, s. 31-Konferansepaper (Fagfellevurdert)
  • 59.
    Hammersberg, Peter
    et al.
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Måns, Mångård
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Correction for beam hardening artefacts in computerised tomography1998Inngår i: Journal of X-Ray Science and Technology, ISSN 0895-3996, E-ISSN 1095-9114, Vol. 8, nr 1, s. 75-93Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Conventional computerised tomography systems (CT) are usually equipped with polyenergetic X-ray sources, which prevents accurate density measurements because of the general CT-image artefact called beam hardening (BH). BH results in false gradients of the linear attenuation coefficient in the CT cross section images, indicating a non-existent density or composition gradient in the imaged object. A number of methods have been proposed to correct for, or limit the effect of, beam hardening. One of these is called linearisation of the CT-data, in which the polyenergetic CT-data are transformed to monoenergetic CT-data. This requires knowledge of the CT-data as a function of object thickness. Data points to derive this function are usually measured using a set of samples of different object material thicknesses at the imaging parameter settings used and fitted with a polynomial. However, the sample preparation makes this method tedious to use. In this work a simulation method has been developed, which can accurately simulate the polyenergetic CT-data for any arbitrary object material and thickness if a priori information of the object material density and composition exists. The simulation method requires detailed knowledge of the imaging system, that is, X-ray energy spectra, detector response and information transfer from detector to digitised data. Besides developing the simulation tool, it has been shown that one of the major difficulties with this BH-correction method is to accurately determine the curvature of the function representing the polyenergetic CT-data. Earlier proposed endorsements to fit a second-degree polynomial to the polyenergetic CT-data are not sufficient to describe its curvature, at least a polynomial of degree eight or higher is required. Here cubic-spine interpolation is used, which avoids the problem.

  • 60.
    Hjortsberg, Erik
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Attempts to use computerised tomography and image analysis to investigate the influence of the filling operation on the density of compressed ringsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Computerised tomography has the potential to become an invaluable tool for R&D activities within the field of powder metallurgy. At the present the method is however not sufficiently adapted for this application. Here a novel experimental routine combining computerised tomography with image analysis have been used to investigate the influence of the filling operation on the density distributions within compressed rings. Sufficient time was however not available to fully interpret the produced result and to validate the reliability of this technique. Analysis of less complex samples with known density distributions is suggested as a way to continue this investigation and to test the reliability of the method. The outline for a project where such a study could be perfom1ed is included in this report.

  • 61.
    Hjortsberg, Erik
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Density Variations in Iron Powder Caused by Die Filling2000Inngår i: PM2000, 2000Konferansepaper (Annet vitenskapelig)
    Abstract [en]

    In this work the influence of the filling shoe movement on the powder density in a lilled. ring shaped cavity has been investigated. The outer diameter of the cavity was 29 cm and the approximate weight of powder in a filled cavity was 650g. The density variations between different parts of the ring and different types of filling operations have been measured. It has been determined that the movement of the filling shoe causes density variations in the filled powder and that these density variations are identical for rings filled under the same conditions. Conventional filling. where the filling shoe only performs one filling cycle resulted in density variations from 0.354 to 0.363 in relative density. By measuring the particle size distribution in different sections of the rings by laser interferometry it was also possible to detem1ine that the filling shoe movement has a segregating effect on the filled powder. By comparing the amount of segregation with other investigations it was possible to determine that this segregation only has a limited influence (less then 10 %) on the powder density and that the major part of the densification originated from the physical rearrangement of the powder particles.

  • 62.
    Hjortsberg, Erik
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Studies of density variations in iron powder caused by the filling operation2001Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Detailed information about the density within a part produced by compression of a granular material is perhaps the most important piece of information you need if you are to predict its properties. Nearly all mechanical properties are strongly dependent on the density and the density of a very small region within the part can potentially be disastrous if it has a density level considerably lower then the rest of the part. Filling induced density variations is a problem that long has been overlooked by powder metallurgy scientists. One of the factors that are making investigations difficult is the lack of methods to make experimental data available. In this work four different methods for this purpose have been evaluated.

    Metallographic examinations

    Has proven to be a reliable method to provide information about the density variations in cut, 2 dimensional cross sections of PM samples. To produce the amount of data necessary to study the filling operation is however considered too labour intensive.

    Bulk densitv measurements of compressed samples

    A simple and reliable method, perfect for thorough investigations of densityvariations in industrially produced PM components.

    Density measurements of filled powder

    Although not as accurate as bulk density measurements the increased flexibility of this method can be an advantage when investigating filling behaviour. A novel test rig was constructed that was able to identify and link several different factors to the resulting density variations.

    Computerised Tomography

    This method has the potential to deliver the same information as metallographic examinations in a much faster and more reliable way. It has however not yet been established if the accuracy ofthe method is sufficient to provide information about the density variation in PM samples caused by the filling operation.

    With the bulk density and the filled powder methods deeper studies were also performed to increase the knowledge of powder filling behaviour. It has been established that the filling operation causes density variations within PM parts and that these variations are highly systematic. With the construction of the test rig it was possible to determine several aspects of the feed shoe cycle as responsible for these variations.

    Delarbeid
    1. Density Variations in Iron Powder Caused by Die Filling
    Åpne denne publikasjonen i ny fane eller vindu >>Density Variations in Iron Powder Caused by Die Filling
    2000 (engelsk)Inngår i: PM2000, 2000Konferansepaper, Publicerat paper (Annet vitenskapelig)
    Abstract [en]

    In this work the influence of the filling shoe movement on the powder density in a lilled. ring shaped cavity has been investigated. The outer diameter of the cavity was 29 cm and the approximate weight of powder in a filled cavity was 650g. The density variations between different parts of the ring and different types of filling operations have been measured. It has been determined that the movement of the filling shoe causes density variations in the filled powder and that these density variations are identical for rings filled under the same conditions. Conventional filling. where the filling shoe only performs one filling cycle resulted in density variations from 0.354 to 0.363 in relative density. By measuring the particle size distribution in different sections of the rings by laser interferometry it was also possible to detem1ine that the filling shoe movement has a segregating effect on the filled powder. By comparing the amount of segregation with other investigations it was possible to determine that this segregation only has a limited influence (less then 10 %) on the powder density and that the major part of the densification originated from the physical rearrangement of the powder particles.

    Emneord
    Powder Metallurgy, Powder Filling, Density Variations, Segregation
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-30163 (URN)15649 (Lokal ID)15649 (Arkivnummer)15649 (OAI)
    Konferanse
    PM2000, November 12-16 2000, Kyoto, Japan.
    Tilgjengelig fra: 2009-10-09 Laget: 2009-10-09 Sist oppdatert: 2013-11-28
    2. Filling induced density variations in metal powder
    Åpne denne publikasjonen i ny fane eller vindu >>Filling induced density variations in metal powder
    2002 (engelsk)Inngår i: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 45, nr 2, s. 146-153Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Filling induced density variations is a problem that has long been overlooked by powder metallurgy scientists. In this paper,densityvariations are addressed, both why they occur and what problems they may cause. A test method, including a test rig, is presented that is able to link several different factors to resulting powder densities. The relations are analysed and several density affecting mechanisms are suggested. These mechanisms could be used either to minimise density differences within parts or to control density by directing powder to critical areas.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-30012 (URN)10.1179/003258902225002578 (DOI)000176949500025 ()15456 (Lokal ID)15456 (Arkivnummer)15456 (OAI)
    Tilgjengelig fra: 2009-10-09 Laget: 2009-10-09 Sist oppdatert: 2017-12-13
    3. Attempts to use computerised tomography and image analysis to investigate the influence of the filling operation on the density of compressed rings
    Åpne denne publikasjonen i ny fane eller vindu >>Attempts to use computerised tomography and image analysis to investigate the influence of the filling operation on the density of compressed rings
    (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Computerised tomography has the potential to become an invaluable tool for R&D activities within the field of powder metallurgy. At the present the method is however not sufficiently adapted for this application. Here a novel experimental routine combining computerised tomography with image analysis have been used to investigate the influence of the filling operation on the density distributions within compressed rings. Sufficient time was however not available to fully interpret the produced result and to validate the reliability of this technique. Analysis of less complex samples with known density distributions is suggested as a way to continue this investigation and to test the reliability of the method. The outline for a project where such a study could be perfom1ed is included in this report.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-102052 (URN)
    Tilgjengelig fra: 2013-11-28 Laget: 2013-11-28 Sist oppdatert: 2013-11-28
  • 63.
    Hjortsberg, Erik
    et al.
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Bergquist, Bjarne
    Department of Quality Technology, Luleå University of Technology, Luleå, Sweden.
    Filling induced density variations in metal powder2002Inngår i: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 45, nr 2, s. 146-153Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Filling induced density variations is a problem that has long been overlooked by powder metallurgy scientists. In this paper,densityvariations are addressed, both why they occur and what problems they may cause. A test method, including a test rig, is presented that is able to link several different factors to resulting powder densities. The relations are analysed and several density affecting mechanisms are suggested. These mechanisms could be used either to minimise density differences within parts or to control density by directing powder to critical areas.

  • 64.
    Hofslagare, Per
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Effect of fiber reinforcement on fatigue crack growth in fiber metal laminates2002Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Fiber Metal Laminates (FML) are a class of materials with highly resistant fatigue behavior. developed primary for the aerospace industry. The laminates are comprised of alternating layers of high strength alurninum sheet and fiber reinforced polymers. The high fatigue resistance is mainly provided by the fatigue resisting fibers bridging the metal fatigue crack.

    Several works to describe and to predict the fiber bridging phenomena and their effect on crack growth rate of the laminate have been published in the literature. Some of these studies have used a modeling approach. where with the help of geometry and constitutive relations the effect or interaction of the fiber bridging and the metal crack propagation rate has been evaluated. Others have used an experimental approach, where the metal crack propagation rate is measured for different load ranges. or with modified reinforcement, to be compared with the behavior of non-reinforced aluminum sheets, so called monolithic sheets.

    In this work, an experimental method has been developed and used with the purpose of increasing the understanding of the stress field around a metal crack in fiber metal laminates. The experimental results and the assumptions in the method have been compared with FE analysis. Knowledge of the stress field around a metal crack for fiber-metal laminates is useful for fwther development in modeling the fiber bridging phenomena in fiber metal laminates.

    In order to prove the validity of an effective stress intensity range model found in the literature, a parametric study of some of the key variables of the model has been performed. Crack growth tests have been performed to give crack growth data for the fiber-metal-laminates and for the metal sheet material, used in the fiber metal laminates. The idea was to compare the fiber-metal-laminates with the metal sheet material in respect of the crack growth rate - stress intensity range relation.

    Delarbeid
    1. Parametric study for som variabels, which affects the fatigue crack growth of fiber metal laminates
    Åpne denne publikasjonen i ny fane eller vindu >>Parametric study for som variabels, which affects the fatigue crack growth of fiber metal laminates
    (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Research has been carried out to investigate the crack growth behavior of glass fiber reinforced aluminum laminates (GLARE®). In order to prove the validity of an effective stress intensity range model found in the literature, a parametric study of some of the key variables of the mode! has been performed. Crack growth tests have been performed to give crack growth data for the fiber-metal-laminates and for the metal sheet material, used in the fiber metal larninates. The idée is to compare fibermetal-laminates with metal sheet material with respect to the crack growth rate - stress intensity range relation. The experimental results show that the model seems to overestimate the stress intensity range for test conditions having a high mean stress in the aluminum layers. For the load range used, a high average stress in the aluminum layers also leads to larger delaminations. Any individual change of the key parameters investigated, cannot shift the calculated effective stress intensity range for the fiber-metal-laminates so that the experimental crack growth data fit the crack growth data of the non-reinforced aluminum.

    Even if the model overestimates the effective stress intensity range for some test conditions, the model succeeds to describe the overall crack growth behavior of fiber-metal-laminates.

    Emneord
    stress intensity factor, fiber-metal-laminate, crack growth, delamination
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-88096 (URN)
    Tilgjengelig fra: 2013-01-30 Laget: 2013-01-30 Sist oppdatert: 2013-11-28
    2. The influence of delamination size on fibre reinforcement in fibre metal laminates
    Åpne denne publikasjonen i ny fane eller vindu >>The influence of delamination size on fibre reinforcement in fibre metal laminates
    (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Research has been carried out to investigate the influence of delamination size for crack growth behaviour of glass fibre reinforced aluminium laminates (GLARE®). The aim of this work has been to investigate to what degree the restraining fibres in the wake of a metal fatigue crack carry load, and to what extent the size and shape of the delamination will affect the magnitude of the fibre-reinforcement. Tests for different delamination shapes by measuring the stiffness change when restraining fibres are removed has been performed and compared with finite element analysis. The investigation shows that the fibres can be assumed to have a constant stress through the metal crack length, and that a smaller delamination gives a higher restraining effect.

    Emneord
    glare, fibre, reinforcement, aluminium, delamination
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-88097 (URN)
    Tilgjengelig fra: 2013-01-30 Laget: 2013-01-30 Sist oppdatert: 2013-11-28
  • 65.
    Hofslagare, Per
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Fatigue crack growth in fiber metal laminates: experiment and modeling2004Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Fiber Metal Laminates (FML) is a class of materials with highly resistant fatigue behavior, developed primary for the aerospace industry. The laminates are comprised of alternating layers of high strength aluminwn sheet and fiber reinforced polymers. The high fatigue resistance is mainly provided by the fatigue resisting fibers bridging the metal fatigue crack.

    Several works to describe and to prediet the fiber bridging phenomena and their effect on crack growth rate of the laminate have been published in the literature. Some of these studies have used a modeling approach, where with the help of geometry and constitutive relations the effect or interaction of the fiber bridging and the metal crack propagation rate has been evaluated. Others have used an experimental approach, where the metal crack propagation rate is measured for different load ranges, or with modified reinforcement, to be compared with the behavior of non-reinforced aluminum sheets, so called monolithic sheets.

    In this work, an experimental method has been developed and used with the purpose of increasing the understanding of the stress field around a metal crack in fiber metal laminates. The experimental results and the assumptions in the method have been compared with FE analysis. Knowledge of the stress field around a metal crack for fiber-metal laminates is useful for further development in modeling the fiber bridging phenomena in fiber metal laminates.

    In order to prove the validity of an effective stress intensity range model found in the literature, a parametric study of some of the key variables of the mode! has been performed. Crack growth tests have been performed to give crack growth data for the fiber-metal-laminates and for the metal sheet material, used in the fiber metal Jaminates. The idea was to compare the fiber-metal-laminates with the meta! sheet material in respect of the crack growth rate - stress intensity range relation.

    A comparison between different residual stress measurement methods on FML has been made. The methods used were X-ray diffraction, neutron diffiaction and strain measurement throughout destructively produced stress release. Good agreement was found between the different methods.

    Neutron diffraction residual stress measurements have also been performed on fatigue-damaged material, specifically in the wake of a fatigue-induced metal crack in the laminate.

    A 3D FEA of a fatigue crack has been made with different fatigue crack geometries. The results has been compared with experimental data for the two crack fronts (delamination growth and metal crack growth).

    In order to magnify the role of the delamination shape on metal crack growth in FML, further crack growth tests have been performed. For different levels of the alternating loading different delamination shapes were developed. By changing the level of the alternating loading for some tests, a comparison ofthe metal crack growth at small delamination damage and larger delamination damage could be made. The experimental crack growth results are compared with 3D FEA and other models found in the literature.

    Delarbeid
    1. Parametric study for som variabels, which affects the fatigue crack growth of fiber metal laminates
    Åpne denne publikasjonen i ny fane eller vindu >>Parametric study for som variabels, which affects the fatigue crack growth of fiber metal laminates
    (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Research has been carried out to investigate the crack growth behavior of glass fiber reinforced aluminum laminates (GLARE®). In order to prove the validity of an effective stress intensity range model found in the literature, a parametric study of some of the key variables of the mode! has been performed. Crack growth tests have been performed to give crack growth data for the fiber-metal-laminates and for the metal sheet material, used in the fiber metal larninates. The idée is to compare fibermetal-laminates with metal sheet material with respect to the crack growth rate - stress intensity range relation. The experimental results show that the model seems to overestimate the stress intensity range for test conditions having a high mean stress in the aluminum layers. For the load range used, a high average stress in the aluminum layers also leads to larger delaminations. Any individual change of the key parameters investigated, cannot shift the calculated effective stress intensity range for the fiber-metal-laminates so that the experimental crack growth data fit the crack growth data of the non-reinforced aluminum.

    Even if the model overestimates the effective stress intensity range for some test conditions, the model succeeds to describe the overall crack growth behavior of fiber-metal-laminates.

    Emneord
    stress intensity factor, fiber-metal-laminate, crack growth, delamination
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-88096 (URN)
    Tilgjengelig fra: 2013-01-30 Laget: 2013-01-30 Sist oppdatert: 2013-11-28
    2. The influence of delamination size on fibre reinforcement in fibre metal laminates
    Åpne denne publikasjonen i ny fane eller vindu >>The influence of delamination size on fibre reinforcement in fibre metal laminates
    (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Research has been carried out to investigate the influence of delamination size for crack growth behaviour of glass fibre reinforced aluminium laminates (GLARE®). The aim of this work has been to investigate to what degree the restraining fibres in the wake of a metal fatigue crack carry load, and to what extent the size and shape of the delamination will affect the magnitude of the fibre-reinforcement. Tests for different delamination shapes by measuring the stiffness change when restraining fibres are removed has been performed and compared with finite element analysis. The investigation shows that the fibres can be assumed to have a constant stress through the metal crack length, and that a smaller delamination gives a higher restraining effect.

    Emneord
    glare, fibre, reinforcement, aluminium, delamination
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-88097 (URN)
    Tilgjengelig fra: 2013-01-30 Laget: 2013-01-30 Sist oppdatert: 2013-11-28
    3. Residual stress measurement on fiber-metal-laminates
    Åpne denne publikasjonen i ny fane eller vindu >>Residual stress measurement on fiber-metal-laminates
    2003 (engelsk)Inngår i: Journal of Neutron Research, ISSN 1023-8166, E-ISSN 1477-2655, Vol. 11, nr 4, s. 215-220Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    A comparison between different residual stress measurement methods on fibre reinforced metal laminates was made. The methods used were X-ray diffraction, neutron diffraction and strain measurement throughout destructively produced stress release. Good agreement was found between the different methods. For these types of laminates, thermally caused residual stresses arise during manufacture. Stretch operation of the laminate will modify the residual stress state. It is well documented that the residual stress state greatly affects the fatigue properties of these laminates, not only during the fatigue initiation stage but also during fatigue crack propagation [1–3]. Neutron diffraction residual stress measurements have also been performed on fatigue-damaged material, specifically in the wake of a fatigue-induced metal crack in the laminate. Delamination and fibre degeneration occur to some extent in the surroundings of the fatigue-induced metal flaw. This will cause a relaxation of the compressive residual stress, and it will affect further development of the fatigue damage.

    Emneord
    Neutron, X-ray, Diffraction, Residual stress, Glare, Delamination
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-88098 (URN)10.1080/10238160410001726639 (DOI)
    Tilgjengelig fra: 2013-01-30 Laget: 2013-01-30 Sist oppdatert: 2017-12-06
    4. Experimental observations and numerical analysis of fatigue crack development in fiber metal laminates
    Åpne denne publikasjonen i ny fane eller vindu >>Experimental observations and numerical analysis of fatigue crack development in fiber metal laminates
    (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Experimental and numerical studies have been carried out in order to reveal and explain the crack growth behavior of glass fiber reinforced aluminum laminates (GLARE®). Fatigue crack growth tests with center crack tension specimen have been performed. Optical crack growth measurements for surface cracks combined with in situ ultrasonic measurements, to determine the delamination size and shape, have been conducted. Complimentary fatigue induced delamination growth tests have also been performed, and the results from the two experiments have been compared. A 3D linear elastic model has been developed. Comparison between model and experimental results are made, and suggestions for further development in modeling are given.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-88100 (URN)
    Tilgjengelig fra: 2013-01-30 Laget: 2013-01-30 Sist oppdatert: 2013-01-30
    5. Delamination size dependence on fatigue crack growth in fiber metal laminates
    Åpne denne publikasjonen i ny fane eller vindu >>Delamination size dependence on fatigue crack growth in fiber metal laminates
    (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    A fatigue crack growth study have been carried out in order to reveal the dependence of the delamination shape and size on metal crack growth in fiber metal laminates (GLARE®). Fatigue crack growth tests with center crack tension specimen (CCT) with loading range shifts have been performed. Optical crack growth measurements for surface cracks combined with ultrasonic measurements, to determine the delamination size and shape, have been conducted. Experiment show that the shape of the delamination tip, in particular, but also the delamination size depends strongly on the loading range. The crack growth rate for a given loading range is dissimilar if the prior loading range was different. This dissirnilarity may remain with further crack growth, or disappear with further crack growth. A strong interaction between the development of the delamination tip and a loading shift exists. It is therefore believed that the crack tip shape is causing the dissimilar crack growth rate.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-88101 (URN)
    Tilgjengelig fra: 2013-01-30 Laget: 2013-01-30 Sist oppdatert: 2013-01-30
  • 66.
    Hofslagare, Per
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    Residual stress measurement on fiber-metal-laminates2003Inngår i: Meca Sens II, UMIST,2003, 2003Konferansepaper (Fagfellevurdert)
  • 67.
    Hofslagare, Per
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Residual stress measurement on fiber-metal-laminates2003Inngår i: Journal of Neutron Research, ISSN 1023-8166, E-ISSN 1477-2655, Vol. 11, nr 4, s. 215-220Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A comparison between different residual stress measurement methods on fibre reinforced metal laminates was made. The methods used were X-ray diffraction, neutron diffraction and strain measurement throughout destructively produced stress release. Good agreement was found between the different methods. For these types of laminates, thermally caused residual stresses arise during manufacture. Stretch operation of the laminate will modify the residual stress state. It is well documented that the residual stress state greatly affects the fatigue properties of these laminates, not only during the fatigue initiation stage but also during fatigue crack propagation [1–3]. Neutron diffraction residual stress measurements have also been performed on fatigue-damaged material, specifically in the wake of a fatigue-induced metal crack in the laminate. Delamination and fibre degeneration occur to some extent in the surroundings of the fatigue-induced metal flaw. This will cause a relaxation of the compressive residual stress, and it will affect further development of the fatigue damage.

  • 68.
    Hofslagare, Per
    et al.
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Johansson, Sten
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Delamination size dependence on fatigue crack growth in fiber metal laminatesManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    A fatigue crack growth study have been carried out in order to reveal the dependence of the delamination shape and size on metal crack growth in fiber metal laminates (GLARE®). Fatigue crack growth tests with center crack tension specimen (CCT) with loading range shifts have been performed. Optical crack growth measurements for surface cracks combined with ultrasonic measurements, to determine the delamination size and shape, have been conducted. Experiment show that the shape of the delamination tip, in particular, but also the delamination size depends strongly on the loading range. The crack growth rate for a given loading range is dissimilar if the prior loading range was different. This dissirnilarity may remain with further crack growth, or disappear with further crack growth. A strong interaction between the development of the delamination tip and a loading shift exists. It is therefore believed that the crack tip shape is causing the dissimilar crack growth rate.

  • 69.
    Hofslagare, Per
    et al.
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Johansson, Sten
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Experimental observations and numerical analysis of fatigue crack development in fiber metal laminatesManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Experimental and numerical studies have been carried out in order to reveal and explain the crack growth behavior of glass fiber reinforced aluminum laminates (GLARE®). Fatigue crack growth tests with center crack tension specimen have been performed. Optical crack growth measurements for surface cracks combined with in situ ultrasonic measurements, to determine the delamination size and shape, have been conducted. Complimentary fatigue induced delamination growth tests have also been performed, and the results from the two experiments have been compared. A 3D linear elastic model has been developed. Comparison between model and experimental results are made, and suggestions for further development in modeling are given.

  • 70.
    Hofslagare, Per
    et al.
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Johansson, Sten
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Parametric study for som variabels, which affects the fatigue crack growth of fiber metal laminatesManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Research has been carried out to investigate the crack growth behavior of glass fiber reinforced aluminum laminates (GLARE®). In order to prove the validity of an effective stress intensity range model found in the literature, a parametric study of some of the key variables of the mode! has been performed. Crack growth tests have been performed to give crack growth data for the fiber-metal-laminates and for the metal sheet material, used in the fiber metal larninates. The idée is to compare fibermetal-laminates with metal sheet material with respect to the crack growth rate - stress intensity range relation. The experimental results show that the model seems to overestimate the stress intensity range for test conditions having a high mean stress in the aluminum layers. For the load range used, a high average stress in the aluminum layers also leads to larger delaminations. Any individual change of the key parameters investigated, cannot shift the calculated effective stress intensity range for the fiber-metal-laminates so that the experimental crack growth data fit the crack growth data of the non-reinforced aluminum.

    Even if the model overestimates the effective stress intensity range for some test conditions, the model succeeds to describe the overall crack growth behavior of fiber-metal-laminates.

  • 71.
    Hofslagare, Per
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    Johansson, Sten
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    The influence of bonding strength and residaul stresses on delamination growth in FML1999Inngår i: Fatigue 1999,1999, 1999Konferansepaper (Fagfellevurdert)
  • 72.
    Hofslagare, Per
    et al.
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Johansson, Sten
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    The influence of delamination size on fibre reinforcement in fibre metal laminatesManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Research has been carried out to investigate the influence of delamination size for crack growth behaviour of glass fibre reinforced aluminium laminates (GLARE®). The aim of this work has been to investigate to what degree the restraining fibres in the wake of a metal fatigue crack carry load, and to what extent the size and shape of the delamination will affect the magnitude of the fibre-reinforcement. Tests for different delamination shapes by measuring the stiffness change when restraining fibres are removed has been performed and compared with finite element analysis. The investigation shows that the fibres can be assumed to have a constant stress through the metal crack length, and that a smaller delamination gives a higher restraining effect.

  • 73.
    Hosseini, Mehrdad
    et al.
    IKP, Konstruktionsmaterial Linköpings universitet.
    Ericsson, Torsten
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    Residual Stresses in Laser Cladded Layers2000Inngår i: ASM International Heat Treating Congress,2000, Ohio, USA: Materials Park, Ohio ASM International, the Materials Information Society 2000 , 2000Konferansepaper (Fagfellevurdert)
  • 74.
    Hultman, Lars
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Birch, Jens
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Odén, Magnus
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    Karlsson, Lennart
    Seco Tools AB Fagersta.
    Ljungcrantz, Henrik
    Impact Coatings AB Linköping.
    Review of the Themal and Mechanical Stability of TiN-based Thin Films1999Inngår i: Zeitschrift für Metallkunde, ISSN 0044-3093, Vol. 90, nr 10, s. 803-813Artikkel i tidsskrift (Fagfellevurdert)
  • 75.
    Hultman, Lars
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Engström, Carl
    Volvo Teknisk Utveckling AB Göteborg.
    Odén, Magnus
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    Mechanical and thermal stability of TiN/NbN superlattice thin films2000Inngår i: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 133-134, s. 227-233Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    High-temperature stability and mechanical deformation mechanisms of TiN/NbN superlattice structures have been investigated. Single-crystal TiN/NbN superlattices were deposited by reactive dual-cathode unbalanced magnetron sputtering in an Ar/N2 discharge onto MgO(001) substrates held at a temperature of 700 ░C. The thermal stability was studied by X-ray measurements of superlattice satellite peak intensity variation during and after annealing at up to 950 ░C. The apparent activation energy for metal interdiffusion in the TiN-NbN diffusion couple is temperature-dependent, with values ranging from 2.6 to 4.5 eV. Film hardness as measured by nanoindentation was observed to decrease during annealing, as the result of effective alloying of the nitride layers. TiN/NbN superlattices are ductile at room temperature and exhibit dislocation glide limited to within individual layers in scratching experiments.

  • 76.
    Högberg, H
    et al.
    Ångström Lab Uppsala university.
    Birch, Jens
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Odén, Magnus
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    Malm, J-O
    National Center of HREM Lunds university.
    Hultman, Lars
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Tunnfilmsfysik.
    Jansson, U
    Ångström lab Uppsala university.
    Growth, structure and mechanical properties of transition metal carbide superlattices2001Inngår i: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 16, nr 5, s. 1301-1310Artikkel i tidsskrift (Fagfellevurdert)
  • 77.
    Isaksson, Claes
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Compressive failure of glass fibre NCF composites2007Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Compressive failure of polymer matrix compos ites is very much controlled by material heterogeneity (e.g. fibre waviness and gaps) and out-of-plane loadings (e.g. impact), and to enable design of robust and trustworthy components it is important to understand how different heterogeneity and loadings affect the governing failure mechanisms.

    In the present thesis the governing failure mechanisms for laminates based on glass fibre non-crimp fabrics (NCFs) and unsaturated polyester have been studied. NCF composite materials are well established within the marine and wind turbine industries due to their very good mechanical properties and cost-efficient manufacturing, and has more recently also started to become very popular within the aerospace industry.

    Specimens with impact damage, holes, artificial delaminations, and dents have been tested in compression and examined by post-mortem analyses. Based on the results obtained it is clear that the governing failure mechanism for the specimens with impact damage and artificial delaminations was delamination growth, while the governing failure mechanisms for the specimens with holes were fibre microbuckling and kink band formation. A single dent in the specimens did not seem to influence the compressive strength to any great extent, but when the dent was combined with artificial delaminations the compressive strength was significantly reduced and the specimens failed due to delamination growth.

    As initiation and propagation of delaminations are very much affected by out-of-plane loadings, compression tests were conducted with a low through-the-thickness pressure. A hole was drilled in the middle of the specimens and a bolt and two washers were used to apply a through-the thickness pressure, and as expected, the initiation and propagation of delaminations was postponed and the compressive strength substantially improved.

    Delarbeid
    1. Compressive failure on non-crimp fabric composites containing impact damage, holes and artificial defects
    Åpne denne publikasjonen i ny fane eller vindu >>Compressive failure on non-crimp fabric composites containing impact damage, holes and artificial defects
    (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    The present study concerns compressive failure of glass fibre NCF composite laminates. The objectives of the study are firstly to give insight into the mechanisms leading to failure, and secondly to provide guidelines for development of physically based engineering models.

    The governing failure mechanism for laminates with impact damage, artificial delaminations as well as artificial delaminations and holes was delamination growth, while the governing failure mechanism for laminates with holes was fibre microbuckling and kink band formation. A single artificial dent in the specimens did not seem to reduce the compressive strength to any great extent, but when the dent was combined with artificial delaminations the compressive strength was substantially reduced and the specimens failed due to delamination growth.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-102644 (URN)
    Tilgjengelig fra: 2013-12-17 Laget: 2013-12-17 Sist oppdatert: 2013-12-17
    2. Effects on through-the-thickness pressure on the compressive failure of non-crimp fabric composites
    Åpne denne publikasjonen i ny fane eller vindu >>Effects on through-the-thickness pressure on the compressive failure of non-crimp fabric composites
    (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    This paper presents results from an experimental investigation of the influence of a low through-the- thickness pressure on the compressive failure of glass fibre non-crimp fabric composite laminates. Specimens with holes and artificial delaminattons have been manufactured and tested both with and without through-the-thickness pressure, and based on the results obtained it is clear that fibre microbuckling and kinking governs final failure of laminates with open holes, while initiation and propagation of delaminations governs final failure of laminates with artificial delaminations. However, by applying a low through-the-thickness pressure, initiation and propagation of delaminations can be prevented, or at least postponed, and the compressive failure strength thereby substantially improved.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-102645 (URN)
    Tilgjengelig fra: 2013-12-17 Laget: 2013-12-17 Sist oppdatert: 2013-12-17
  • 78.
    Isaksson, Claes
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    Sjögren, Anders
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    Compressive Failure of NCF Composites Containing Open and Bolted Holes2006Inngår i: Compressive Faliure of NCF Composites Containing Open and Bolted Holes,2006, 2006Konferansepaper (Fagfellevurdert)
  • 79.
    Isaksson, Claes
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    Sjögren, Anders
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    Compressive Failure of NCF Composites Containing Open and Bolted Holes2006Inngår i: 12th Europepan Conference on Composite Materials,2006, 2006Konferansepaper (Annet vitenskapelig)
  • 80.
    Isaksson, Claes
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    Sjögren, Anders
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    Improving the compessive strength of noched and delaminated GFRP laminates by utilizing through-the-thickness pressure2006Inngår i: ICEFA-II 2006 Second International Conference on Engineering Failure Analysis,2006, 2006Konferansepaper (Annet vitenskapelig)
  • 81.
    Jinnestrand, Magnus
    et al.
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Hållfasthetslära. Linköpings universitet, Tekniska högskolan.
    Brodin, Håkan
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Crack initiation and propagation in air plasma sprayed thermal barrier coatings, testing and mathematical modelling of low cycle fatigue behaviour2004Inngår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 379, nr 1-2, s. 45-57Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In the present paper failure mechanisms in air plasma sprayed thermal barrier coatings for land-based gas turbines have been studied. This has been done by finite element simulations and fractographic investigations of low cycle fatigue (LCF) tested material, here chosen as an 350 μm thick partially stabilised zirconia top coat (TC) together with a 150 μm thick Ni-Co-Cr-Al-Y bond coat (BC) on a nickel base substrate (Haynes 230). Both LCF testing, modelling results and fractographic investigations point in the same direction. An increased thickness of the thermally grown oxide (TGO) does decrease the LCF life of a coated structural alloy. Several points of crack initiation were found, in the TGO at the TC/BC interface, at the oxide network within the BC and at oxide inclusions between BC and substrate. During LCF tests the initiated cracks will grow radially into the substrate material. The behaviour is explained by increased TC/BC delamination stresses and changed oxidation behaviour with increased oxidation times.

  • 82.
    Johansson, Johan
    et al.
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Oden, Magnus
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Micro- and macrostress evolution in a duplex stainless steel during uniaxial loading2000Inngår i: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 347-3, s. 603-608Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The evolution of micro- and macrostresses in a duplex stainless steel during uniaxial loading has been investigated in situ by X-ray diffraction. Due to differences in the coefficient of thermal expansion between the two phases, compressive residual microstresses were found in the ferritic phase and balancing tensile microstresses in the austenitic phase. The initial microstresses were almost two times higher in the transverse direction compared to the rolling direction. During loading the microstresses increase in the macroscopic elastic regime but starts to decrease slightly with increasing load in the macroscopic plastic regime. During unloading from the plastic regime the microstresses increases by approximately 35 MPa in the direction of applied load but remains constant in the other directions.

  • 83.
    Johansson (Moverare), Johan
    et al.
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Odén, Magnus
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Load sharing between austenite and ferrite in a duplex stainless steel during cyclic loading2000Inngår i: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 31, nr 6, s. 1557-1570Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The load sharing between phases and the evolution of micro- and macrostresses during cyclic loading has been investigated in a 1.5-mm cold-rolled sheet of the duplex stainless steel SAF 2304. X-ray diffraction (XRD) stress analysis and transmission electron microscopy (TEM) show that even if the hardness and yield strength are higher in the austenitic phase, more plastic deformation will occur in this phase due to the residual microstresses present in the material. The origin of the microstresses is the difference in coefficients of thermal expansion between the two phases, which leads to tensile microstresses in the austenite and compressive microstresses in the ferrite. The microstresses were also found to increase from 50 to 140 MPa in the austenite during the first 100 cycles when cycled in tension fatigue with a maximum load of 500 MPa. The cyclic loading response of the material was, thus, mainly controlled by the plastic properties of the austenitic phase. It was also found that initial compressive macrostresses on the surface increased from −40 to 50 MPa during the first 103 cycles. After the initial increase of microstresses and macrostresses, no fading of residual stresses was found to occur for the following cycles. A good correlation was found between the internal stress state and the microstructure evolution. The change in texture during cyclic fatigue showed a sharpening of the deformation texture in the ferritic phase, while no significant changes were found in the austenitic phase.

  • 84.
    Johansson (Moverare), Johan
    et al.
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Odén, Magnus
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Zeng, Xiaohu
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Evolution of the residual stress state in a duplex stainless steel during loading1999Inngår i: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 47, nr 9, s. 2669-2684Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The evolution of micro- and macrostresses in a duplex stainless steel during loading has been investigated in situ by X-ray diffraction. A 1.5 mm cold-rolled sheet of alloy SAF 2304 solution treated at 1050°C was studied. Owing to differences in the coefficient of thermal expansion between the two phases, compressive residual microstresses were found in the ferritic phase and balancing tensile microstresses in the austenitic phase. The initial microstresses were almost two times higher in the transverse direction compared to the rolling direction. During loading the microstresses increase in the macroscopic elastic regime but start to decrease slightly with increasing load in the macroscopic plastic regime. For instance, the microstresses along the rolling direction in the austenite increase from 60 MPa, at zero applied load, to 110 MPa, at an applied load of 530 MPa. At the applied load of 620 MPa a decrease of the microstress to 90 MPa was observed. During unloading from the plastic regime the microstresses increase by approximately 35 MPa in the direction of applied load but remain constant in the other directions. The initial stress state influences the stress evolution and even after 2.5% plastic strain the main contribution to the microstresses originates from the initial thermal stresses. Finite element simulations show stress variations within one phase and a strong influence of both the elastic and plastic anisotropy of the individual phases on the simulated stress state.

  • 85.
    Johansson, Sten
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    Research in Engineering Materials at Linköping University2005Inngår i: China-Sweden Symposium on Materials Science,2005, 2005Konferansepaper (Annet vitenskapelig)
  • 86.
    Johansson, Sten
    et al.
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Andersson, Nils-Eric
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Zeng, Xiao-Hu
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    The variation of through thickness properties and structure of AA7010 thick plate1997Inngår i: International Conference on Thermomechanical Processing of Steel and Other Materials 1997: THERMEC '97 / [ed] T. Chandra and T. Sakai, 1997, s. 941-949Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The variation of through thickness structure and yield strength of AA7010-T7451 100 and 150 mm thick plate was investigated. Grain sizes at different depths were determined by using optical microscopy and EBSP maps. Texture measurements were carried out, using X-ray technique and EBSP, at the same depths as grain size studies and tensile property tests were performed. EBSP technique was used to compare degree of recovered and recrystallized grain structure at different depths. Tensile testing and hardness measurements reveal through thickness variations in yield strength and hardness. Variations in composition through the thickness are also possible. The influence of texture on yield strength was discussed.

  • 87.
    Johansson, Sten
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    Chai, Guocai
    RD Centre Sandvik Materials Technology, Sandviken.
    Fatigue Crack Propagation of Super-Duplex Stainless Steel at Different Temperatures2006Inngår i: ECF16 16th European Conference of Fracture,2006, 2006Konferansepaper (Fagfellevurdert)
  • 88.
    Johansson, Sten
    et al.
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Hedbrant, Johan
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Energisystem. Linköpings universitet, Tekniska högskolan.
    Kursskal eller aktiv kurshemsida: Sammanfattning av några erfarenheter av kursskali teknologkurser2001Rapport (Annet vitenskapelig)
    Abstract [sv]

    Möjligheten att kommunicera med hjälp av datorer har funnits i mer än 20 år och ur denna möjlighet har ett antal idéer om hur en sådan kommunikation kan utnyttjas vid undervisning realiserats. Istället för att ersätta konventionella brev med elektroniska varianter blev det istället vanligt att skicka korta meddelanden eller att man tog i anspråk de datorstödda sk konferenssystem som utvecklades. Centrala funktioner i dessa system innebar att man inte bara kunde utbyta meddelanden med kort svarstid utan även kunde skapa möten eller aktiviteter, nyhetskontroll och organisation av lästa och olästa meddelanden i en struktur [1]. Dessa konferenssystem kan kompletteras med funktioner som formellt behövs för att kunna bedriva distansundervisning elektroniskt. Exempel på sådana funktioner är:

    • Elektroniska gruppdiskussioner
    • Databaser där elever kan söka, läsa och kopiera information och ävenladda ner undervisningsprogram
    • Datorstöd där läraren växelverkar med studenten
    • Datorstöd för distanstentamen
  • 89.
    Johansson, Sten
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    Ossbahr, Gilbert
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik.
    Harris, Tom
    Airbus Filton.
    Study of the Inluence of Drilling Method and Hole quality on Static Strength and Fatigue Life of Carbon Fiber Reinforced Plastic Aircraft Material2002Rapport (Annet vitenskapelig)
  • 90.
    Johansson, Sten
    et al.
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Zeng, Xiaohu
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Andersson, Nils-Eric
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Peng, Ru
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Measurement of average texture of cold-rolled aluminium sheet by electron back-scattering diffraction: a comparison with neutron diffraction2001Inngår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 315, nr 1-2, s. 129-135Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

         Measurements of the average texture on sheet of commercial pure aluminium have been performed using neutron diffraction and electron back-scattering diffraction (EBSD). Orientation distribution function maps have been calculated and compared. The results show a good correspondence provided that the data from the EBSD measurements are corrected according to a texture index versus inverted number of measurement procedure. Most errors are probably related to differences in investigated volume and calculation technique and to the fact that the microstructure was difficult for EBSD measurements.

  • 91.
    Larsson, Cecilia
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Aspects of residual stress generation in functionally graded WC-Co composites: a literature surveyManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    This literature survey provides an introduction to functionally graded materials, WC-Co composites and estimations of residual stresses in such material systems.

    Functionally graded materials feature gradual transitions in microstructure and/or composition. Gradual transitions are preferred over abrupt transitions which introduce local stress concentrations. The various manufacturing methods for functionally graded materials are divided into two classes. Constructive processes (e.g., powder processes) use an appropriate distribution of constituents, often as a precursor to the component, to create the gradient. Transport based processes (e.g., infiltration) rely on natural transport phenomena such as fluid flow, diffusion of atomic species or conduction of heat.

    Liquid phase sintering of mixed and pressed powder is used to produce WC-Co functionally graded composites. The mechanical properties of WC-Cocomposites and their constituent phases are reviewed. A wide range of overall composite behavior can be achieved when the Co content is varied. For example, the hardness is reported to be 1650 HV for WC with 6 wt.% Co and 780 HV for WC with 25 wt.% Co. The corresponding fracture toughness values are 8.5 and 14.5 MPa m1/2, respectively. These values suggest, that WC contributes to the hardness of the composite and Co contributes to the toughness. Therefore, the possibility of tailoring material performance by varying composition in the component arises.

    During cooling from the sintering temperature, thermal residual stresses develop because of the differences between the WC and Co thermal expansion coefficients. It is possible to use X-ray diffraction methods to measure residual stresses in composites. Results from measurements, and finite element (FE) analysis of the residual stresses in WC-Co composites are also reviewed.

  • 92.
    Larsson, Cecilia
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Determination of residual stresses and mechanical properties using neutron, X-ray diffraction, micro- and nanoindentation techniques2003Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    The existence of residual stresses in engineering materials can significantly affect subsequent lifetime by augmenting or impeding failure. Consequently, for an accurate assessment of engineering lifetimes, there is a need to quantify residual stresses. Furthermore, knowledge of the origin of these stresses in conjunction with mechanical properties such as hardness and fracture toughness, among others, can be used to improve functionality by tailoring the microstructure through processing. In this work, neutron, x-ray diffraction, micro- and nanoindentation techniques were used for residual stress determination and mechanical characterization of WC-Co functionally graded composites, a Co-based Haynes® 25 alloy weld, compressed steel and compacted Fe-brass powders. The neutron and x-ray diffraction techniques were used to assess residual strains and stresses while the instrurnented indentation techniques were used to determine hardness, fracture toughness and elastic modulus. In each of these engineering materials, valuable insight relating to the overall mechanical performance was obtained.

    X-ray diffraction was used to determine thermal residual stresses that develop in a functionally graded WC-Co composite, commonly used as tool bits. Microstresses in the graded zone were attributed to the thermal mismatch between WC and the Co phase. The compressive macrostresses were determined to be a result of the compositional gradient. Micro- and nanoindentation experiments were used to determine hardness as a function of depth in two WC-Co functionally graded materials (FGMs). A relationship between hardness and Co phase content was established and explained for the two graded and five homogeneous samples.

    An experimental and simulation study of residual stresses was made in the vicinity of a gas tungsten arc weld in a Co-based Haynes® 25 alloy used in a satellite component. The experimental measurements were made by neutron diffraction on the recently commissioned Spectrometer for Materials Research at Temperature and Stress (SMARTS) at Los Alamos National Laboratory, USA and the simulation used the implicit Marc finite element code. Comparison between experiment and theory showed general agreement.

    Strain pole figures representative of residual intergranular strains were determined from an -2.98 % uniaxially compressed austenitic stainless steel sample. The neutron diffraction measurements were made on SMARTS, using an Euler cradle to obtain spectra over a range of sample orientations. The measurements were compared with predictions from an elasto-plastic self-consistent model and found to be in reasonable agreement. The model was also used to assess the sensitivity of the strain distribution in the deformed sample to the initial texture.

    Neutron diffraction was used to measure residual stresses in a powder metallurgical green body manufactured by high speed compaction from Fe and 15 wt.% brass powders. The tests were performed on SMARTS with the aid of radial collimators configured to measure spatially resolved strains in the axial and radial directions in a cylindrical specimen. Furthermore, sharp (Berkovich) and spherical (Hertzian) indenters were used for instrumented indentation experiments to determine the hardness and elastic modulus.

    Delarbeid
    1. X-ray diffraction determination of residual stresses in functionally graded WC–Co composites
    Åpne denne publikasjonen i ny fane eller vindu >>X-ray diffraction determination of residual stresses in functionally graded WC–Co composites
    2004 (engelsk)Inngår i: International Journal of Refractory Metals and Hard Materials, ISSN 0263-4368, Vol. 22, nr 4-5, s. 177-184Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    X-ray diffraction was used to determine the thermal residual stresses that develop in a functionally graded WC–Co composite. Stresses were measured in both WC and Co phases at various depths. Pole figures were obtained in order to determine optimal sample orientations that provided adequate intensity for measurements in the Co phase. For WC, the in-plane compressive residual stresses varied approximately between −300 and −500 MPa with depth below the surface. For the low volume fraction Co phase, the tensile residual stresses were approximately 600 MPa. The microstresses in the graded zone were attributed to the thermal mismatch between the WC and the Co phase during cooling from the liquid phase sintering temperature (1450 °C). The microstresses determined were in reasonable agreement with a prediction using Eshelby theory. The compressive macrostresses were attributed to the compositional gradient, a result further substantiated by the fact that no significant macrostresses were measured in a comparable homogeneous sample, i.e., without the compositional gradient. Thus, varying compositional gradients in WC–Co composites during fabrication can be expected to directly influence the macrostress component of the overall residual stress state.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-23160 (URN)10.1016/j.ijrmhm.2004.06.002 (DOI)2564 (Lokal ID)2564 (Arkivnummer)2564 (OAI)
    Tilgjengelig fra: 2009-10-07 Laget: 2009-10-07 Sist oppdatert: 2013-10-02
    2. Hardness profile measurements in functionally graded WC–Co composites
    Åpne denne publikasjonen i ny fane eller vindu >>Hardness profile measurements in functionally graded WC–Co composites
    2004 (engelsk)Inngår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 382, nr 1-2, s. 141-149Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Micro- and nanoindentation were used to determine hardness as a function of depth in two functionally graded WC–Co composites. The gradients were continuous (extended over ∼70 and ∼40 μm, respectively) and consisted of varying WC and Co phase volume fractions. Five comparable homogeneous samples with different Co contents and different average WC grain sizes were also used for direct comparison. A relationship between hardness and Co content was established for both the graded and the homogeneous samples wherein the hardness decreased with increasing Co content. The magnitude of the hardness was the same (for a given Co content) for the functionally graded and the homogeneous materials. The hardness measurements were also correlated with X-ray diffraction studies of thermal residual stresses and the absence of any major influence explained. It is generally concluded that the hardness values are dominated by the local Co content. Additionally, the examination of surface cracks around indents suggests that compositional gradients in WC–Co composites offer increased toughness.

    Emneord
    hardness, functionally graded composites, WC-Co, nanoindentation, microindentation, residual stress
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-46174 (URN)10.1016/j.msea.2004.04.065 (DOI)
    Tilgjengelig fra: 2009-10-11 Laget: 2009-10-11 Sist oppdatert: 2017-12-13
    3. Measurement and modeling of residual stress in a welded Haynes® 25 cylinder
    Åpne denne publikasjonen i ny fane eller vindu >>Measurement and modeling of residual stress in a welded Haynes® 25 cylinder
    Vise andre…
    2005 (engelsk)Inngår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 399, nr 1-2, s. 49-57Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    An experimental and simulation study of residual stresses was made in the vicinity of a gas tungsten arc weld, used to join a hemispherical end cap to a cylinder. The capped cylinder is used in a satellite application and was fabricated from a Co-based Haynes® 25 alloy. The cylinder was 34.7 mm in outer diameter and 3.3 mm in thickness. The experimental measurements were made by neutron diffraction and the simulation used the implicit Marc finite element code. The experimental resolution was limited to approximately 3 mm parallel to the axis of the cylinder (the weld was 6 mm in the same direction) and comparison over the same volume of the finite element prediction showed general agreement. Subject to the limited spatial resolution, the largest experimentally measured tensile residual stress was 180 MPa, located at the middle of the weld. However, the predictions suggest that there are regions in the weld where average tensile residual stresses as much as 400 MPa exist. One qualitative disparity between the model and the experiments was that the measurement included a larger degree of asymmetry on either side of the weld than predicted by the model.

    Emneord
    Cobalt, Finite element, Haynes® 25, Neutron diffraction, Residual stress, Weld
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-50481 (URN)10.1016/j.msea.2005.02.026 (DOI)
    Tilgjengelig fra: 2009-10-11 Laget: 2009-10-11 Sist oppdatert: 2017-12-12
    4. Measurements and predictions of strain pole figures for uniaxially compressed stainless steel
    Åpne denne publikasjonen i ny fane eller vindu >>Measurements and predictions of strain pole figures for uniaxially compressed stainless steel
    2004 (engelsk)Inngår i: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 51, nr 6, s. 571-575Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Strain pole figures representative of residual intergranular strains were determined from an −2.98% uniaxially compressed austenitic stainless steel sample. The measurements were made using neutron diffraction on the recently commissioned Spectrometer for Materials Research at Temperature and Stress (SMARTS) at Los Alamos National Laboratory, USA. The measurements were compared with predictions from an elasto-plastic self-consistent model and found to be in good agreement.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-23147 (URN)10.1016/j.scriptamat.2004.05.030 (DOI)2549 (Lokal ID)2549 (Arkivnummer)2549 (OAI)
    Tilgjengelig fra: 2009-10-07 Laget: 2009-10-07 Sist oppdatert: 2017-12-13
    5. Residual stress and mechanical property evaluation of compacted iron-brass powders using neutron diffracation and instrumented indentation
    Åpne denne publikasjonen i ny fane eller vindu >>Residual stress and mechanical property evaluation of compacted iron-brass powders using neutron diffracation and instrumented indentation
    (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Neutron diffraction was used to measure residual stresses in a powder metallurgical green body manufactured by high speed compaction of iron and 15 wt.% brass powders. The tests were performed with the aid of radial collimators configured to measure spatially resolved strains in the axial and radial directions in a cylindrical specimen. Compressive residual stresses were present in the iron phase and appear to be larger in the lower to middle sections along the specimen's axis. Furthermore, a combination of sharp (Berkovich) and spherical (Hertzian) indenters were used for instrumented indentation experiments. The results from the spherical indenter were used to determine the elastic modulus, while results from the sharp indenter were used to measure the hardness.

    Emneord
    Iron-Brass Powder, Neutron diffraction, Nanoindentation, Residual Stress, Mechanical Properties
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-86864 (URN)
    Merknad

    Parts of this manuscript have been published in the following article: http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-30079

    Tilgjengelig fra: 2013-01-07 Laget: 2013-01-07 Sist oppdatert: 2013-01-07
  • 93.
    Larsson, Cecilia
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Thermal residual stresses, hardness and microstructural characterisation of functionally graded WC-Co composites2001Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    Functionally graded materials (FGMs) incorporate gradual transitions in their microstructure and/or composition with distance. The gradients provide means to favourably engineer their thermomechanical properties by changing e.g., the local modulus, yield strength, state of residual stress etc. However, prior to optimising such gradients, an understanding of their effect on thermomechanical properties is necessary. WC-Co composites are commonly used as tool bits, where the presence of Co improves the toughness of the wear resistant WC. In this thesis, emphasis has been placed on investigating the thermal residual stresses, hardness, and toughness of functionally graded WC-Co.

    The first paper in this thesis reviews existing literature on the subject while introducing FGMs and WC-Co composites. Additional topics addressed include: fabrication of FGMs, mechanical properties of WC-Co and estimates of residual stresses.

    In the second paper, X-ray diffraction was used to determine thermal residual stresses that develop in a functionally graded WC-Co composite. The gradient was continuous during a distance of about 40 Jlm below the surface and the stresses were measured in both WC and Co phases at various depths. Due to the difference in coefficient of thermal expansion between the two phases, tensile residual stresses where found in the Co phase and balancing compressive stresses in WC. Pole figures were obtained in order to determine optimal sample orientations that provided adequate intensity for measurements in the Co phase. Microstresses in the graded zone were attributed to the thermal mismatch between WC and the Co phase. The compressive macrostresses were determined to be a result of the compositional gradient.

    The third paper reports micro- and nanoindentation experiments to determine hardness as a function of depth in two different WC-Co FGMs. A relationship between hardness and Co phase content was established for the two graded and five homogeneous samples wherein the hardness decreases with increasing Co phase content. For a given Co phase content, no significant differences were observed between the FGMs and homogeneous samples. The measured thermal residual residual stresses did not appear to influence the hardness. Additionally, examination of indents using a Vickers indenter with different loads suggested that larger loads were required to initiate cracks in the FGMs compared to the homogeneous materials. While the investigated WC-Co FGMs did not offer advantages in hardness properties (which seem to be dominated by the local Co content in the graded zone), they appear to offer tribological advantages through increased toughness in terms of crack suppression.

    Delarbeid
    1. Aspects of residual stress generation in functionally graded WC-Co composites: a literature survey
    Åpne denne publikasjonen i ny fane eller vindu >>Aspects of residual stress generation in functionally graded WC-Co composites: a literature survey
    (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    This literature survey provides an introduction to functionally graded materials, WC-Co composites and estimations of residual stresses in such material systems.

    Functionally graded materials feature gradual transitions in microstructure and/or composition. Gradual transitions are preferred over abrupt transitions which introduce local stress concentrations. The various manufacturing methods for functionally graded materials are divided into two classes. Constructive processes (e.g., powder processes) use an appropriate distribution of constituents, often as a precursor to the component, to create the gradient. Transport based processes (e.g., infiltration) rely on natural transport phenomena such as fluid flow, diffusion of atomic species or conduction of heat.

    Liquid phase sintering of mixed and pressed powder is used to produce WC-Co functionally graded composites. The mechanical properties of WC-Cocomposites and their constituent phases are reviewed. A wide range of overall composite behavior can be achieved when the Co content is varied. For example, the hardness is reported to be 1650 HV for WC with 6 wt.% Co and 780 HV for WC with 25 wt.% Co. The corresponding fracture toughness values are 8.5 and 14.5 MPa m1/2, respectively. These values suggest, that WC contributes to the hardness of the composite and Co contributes to the toughness. Therefore, the possibility of tailoring material performance by varying composition in the component arises.

    During cooling from the sintering temperature, thermal residual stresses develop because of the differences between the WC and Co thermal expansion coefficients. It is possible to use X-ray diffraction methods to measure residual stresses in composites. Results from measurements, and finite element (FE) analysis of the residual stresses in WC-Co composites are also reviewed.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-102050 (URN)
    Tilgjengelig fra: 2013-11-28 Laget: 2013-11-28 Sist oppdatert: 2013-11-28
    2. Thermal residues stresses and microstructural characterisation of functionally graded WC-Co composites
    Åpne denne publikasjonen i ny fane eller vindu >>Thermal residues stresses and microstructural characterisation of functionally graded WC-Co composites
    (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    X-ray diffraction was used to determine the thermal residual stresses that develop in a functionally graded WC-Co composite. The gradient was continuous within a distance of about 40 Jlm below the surface and consisted of varying WC and Co phase volume fractions. The composite was characterised by scanning electron microscopy, optical microscopy and X-ray diffraction. Thermal residual stresses develop due to the thermal mismatch between the WC and the Co phase during cooling from the liquid-phase sintering temperature (1450°C). Pole figures were obtained in order to determine optimal sample orientations that provided adequate intensity for measurements in the Co phase. Stresses were measured in both WC and Co phases at various depths. For WC, the in-plane compressive residual stresses varied approximately between -300 MPa to -500 MPa with depth below the surface. For the low volume fraction Co phase, the tensile residual stresses were approximately 600 MPa. The changes in the magnitude of the residual stresses can be related to the changes in the Co phase content through the graded zone. Microstresses in the graded zone are attributed to the thermal mismatch between WC and the Co phase. The compressive macrostresses were determined to be a result of the compositional gradient. This conclusion is strongly supported by the result that almost no macrostresses were measured in a similar homogenous sample i.e., without the corresponding compositional gradient. Therefore, varying the composition gradient during fabrication is expected to directly affect the macrostresses.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-102051 (URN)
    Tilgjengelig fra: 2013-11-28 Laget: 2013-11-28 Sist oppdatert: 2013-11-28
    3. Hardness profile measurements in functionally graded WC–Co composites
    Åpne denne publikasjonen i ny fane eller vindu >>Hardness profile measurements in functionally graded WC–Co composites
    2004 (engelsk)Inngår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 382, nr 1-2, s. 141-149Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    Micro- and nanoindentation were used to determine hardness as a function of depth in two functionally graded WC–Co composites. The gradients were continuous (extended over ∼70 and ∼40 μm, respectively) and consisted of varying WC and Co phase volume fractions. Five comparable homogeneous samples with different Co contents and different average WC grain sizes were also used for direct comparison. A relationship between hardness and Co content was established for both the graded and the homogeneous samples wherein the hardness decreased with increasing Co content. The magnitude of the hardness was the same (for a given Co content) for the functionally graded and the homogeneous materials. The hardness measurements were also correlated with X-ray diffraction studies of thermal residual stresses and the absence of any major influence explained. It is generally concluded that the hardness values are dominated by the local Co content. Additionally, the examination of surface cracks around indents suggests that compositional gradients in WC–Co composites offer increased toughness.

    Emneord
    hardness, functionally graded composites, WC-Co, nanoindentation, microindentation, residual stress
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-46174 (URN)10.1016/j.msea.2004.04.065 (DOI)
    Tilgjengelig fra: 2009-10-11 Laget: 2009-10-11 Sist oppdatert: 2017-12-13
  • 94.
    Larsson, Cecilia
    et al.
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Clausen, B.
    Los Alamos National Laboratory, Los Alamos, USA.
    Holden, T.M.
    Los Alamos National Laboratory, Los Alamos, USA.
    Bourke, M.A.M.
    Los Alamos National Laboratory, Los Alamos, USA.
    Measurements and predictions of strain pole figures for uniaxially compressed stainless steel2004Inngår i: Scripta Materialia, ISSN 1359-6462, E-ISSN 1872-8456, Vol. 51, nr 6, s. 571-575Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Strain pole figures representative of residual intergranular strains were determined from an −2.98% uniaxially compressed austenitic stainless steel sample. The measurements were made using neutron diffraction on the recently commissioned Spectrometer for Materials Research at Temperature and Stress (SMARTS) at Los Alamos National Laboratory, USA. The measurements were compared with predictions from an elasto-plastic self-consistent model and found to be in good agreement.

  • 95.
    Larsson, Cecilia
    et al.
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Ericsson, Torsten
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Residual stress and mechanical property evaluation of compacted iron-brass powders using neutron diffracation and instrumented indentationManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    Neutron diffraction was used to measure residual stresses in a powder metallurgical green body manufactured by high speed compaction of iron and 15 wt.% brass powders. The tests were performed with the aid of radial collimators configured to measure spatially resolved strains in the axial and radial directions in a cylindrical specimen. Compressive residual stresses were present in the iron phase and appear to be larger in the lower to middle sections along the specimen's axis. Furthermore, a combination of sharp (Berkovich) and spherical (Hertzian) indenters were used for instrumented indentation experiments. The results from the spherical indenter were used to determine the elastic modulus, while results from the sharp indenter were used to measure the hardness.

  • 96.
    Larsson, Cecilia
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    Holden, T M
    Los Alamos Lab Los Alamos.
    Bourke, M A M
    Los Alamos National Lab Los Alamos.
    Stout, M
    Los Alamos National Lab Los Alamos.
    Residual Stress Measurement in a Co-bsed Haynes -25 Cylinder2002Inngår i: American conference on Neutron Scattering ACNS,2002, 2002Konferansepaper (Fagfellevurdert)
  • 97.
    Larsson, Cecilia
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    Odén, Magnus
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    Determination of Thermal Residual Stresses in a Functionally Graded WC-Co composite2002Inngår i: Denver X-ray Conference,2002, 2002Konferansepaper (Fagfellevurdert)
  • 98.
    Larsson, Cecilia
    et al.
    Linköpings universitet, Institutionen för ekonomisk och industriell utveckling, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Odén, Magnus
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Hardness profile measurements in functionally graded WC–Co composites2004Inngår i: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 382, nr 1-2, s. 141-149Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Micro- and nanoindentation were used to determine hardness as a function of depth in two functionally graded WC–Co composites. The gradients were continuous (extended over ∼70 and ∼40 μm, respectively) and consisted of varying WC and Co phase volume fractions. Five comparable homogeneous samples with different Co contents and different average WC grain sizes were also used for direct comparison. A relationship between hardness and Co content was established for both the graded and the homogeneous samples wherein the hardness decreased with increasing Co content. The magnitude of the hardness was the same (for a given Co content) for the functionally graded and the homogeneous materials. The hardness measurements were also correlated with X-ray diffraction studies of thermal residual stresses and the absence of any major influence explained. It is generally concluded that the hardness values are dominated by the local Co content. Additionally, the examination of surface cracks around indents suggests that compositional gradients in WC–Co composites offer increased toughness.

  • 99.
    Larsson, Cecilia
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    Odén, Magnus
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial.
    Thermal Residual Stresses in Functionally Graded WC-Co Composites Determined by X-ray Diffraction2000Inngår i: ICRS-6,2000, 2000Konferansepaper (Fagfellevurdert)
  • 100.
    Larsson, Cecilia
    et al.
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Odén, Magnus
    Linköpings universitet, Institutionen för konstruktions- och produktionsteknik, Konstruktionsmaterial. Linköpings universitet, Tekniska högskolan.
    Thermal residues stresses and microstructural characterisation of functionally graded WC-Co compositesManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    X-ray diffraction was used to determine the thermal residual stresses that develop in a functionally graded WC-Co composite. The gradient was continuous within a distance of about 40 Jlm below the surface and consisted of varying WC and Co phase volume fractions. The composite was characterised by scanning electron microscopy, optical microscopy and X-ray diffraction. Thermal residual stresses develop due to the thermal mismatch between the WC and the Co phase during cooling from the liquid-phase sintering temperature (1450°C). Pole figures were obtained in order to determine optimal sample orientations that provided adequate intensity for measurements in the Co phase. Stresses were measured in both WC and Co phases at various depths. For WC, the in-plane compressive residual stresses varied approximately between -300 MPa to -500 MPa with depth below the surface. For the low volume fraction Co phase, the tensile residual stresses were approximately 600 MPa. The changes in the magnitude of the residual stresses can be related to the changes in the Co phase content through the graded zone. Microstresses in the graded zone are attributed to the thermal mismatch between WC and the Co phase. The compressive macrostresses were determined to be a result of the compositional gradient. This conclusion is strongly supported by the result that almost no macrostresses were measured in a similar homogenous sample i.e., without the corresponding compositional gradient. Therefore, varying the composition gradient during fabrication is expected to directly affect the macrostresses.

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