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  • 101.
    Larsson, Cecilia
    et al.
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Odén, Magnus
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    X-ray diffraction determination of residual stresses in functionally graded WC–Co composites2004In: International Journal of Refractory Metals and Hard Materials, ISSN 0263-4368, Vol. 22, no 4-5, p. 177-184Article in journal (Refereed)
    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.

  • 102.
    Luukkonen, Petri
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Ericsson, Torsten
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Residual Stresses in Green Bodies of Steel Powder and Their Relaxation during Heat Treatment2000In: 20th ASM Heat Teating Society Conference,2000, ASM International, 2000, p. 435-440Conference paper (Refereed)
    Abstract [en]

    Stresses and residual stresses have been measured in rectangular bars after compaction under 400 and 530 MPa after the removal of the pressure and in three positions: The bar completely inside the die, the bar partially outside and the bar completely free. The stresses have been measured by X-ray and neutron diffraction. It was found that stresses around 35 MPa in compression on the top surface prevail when the bar is inside the die and it is reduced to half when the bar is partly outside and even more when completely outside the die. However on the side surfaces considerable compressive residual stresses exist in the free bar in a thin surface layer and tensile residual stresses below this layer. It is proposed that plastic deformation of the side surface during ejection is a major cause for the residual stresses. Heat treatment at 450°C decreases the residual stresses. Two different powders have been used: Höganäs ASC 100.29 with lubricant added and Höganäs Distaloy AE without lubricant. The presence of lubricant reduces the residual stresses. Direct current potential drop, DCPD, measurements have also been carried out and are discussed together with the residual stress data.

  • 103.
    Luukkonen, Petri
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Ericsson, Torsten
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Robust direct current potential drop method to inspect cold pressed green bodies2003Article in journal (Refereed)
    Abstract [en]

    The basics of the direct current potential drop (DCPD) method is presented. It is applied to studies of pressing defects in green bodies made of iron based powders. Three types of bodies are studied: rectangular bars, two level L shaped bodies and a multilevel industrial body. It is found that by using ratios of potential drop (PD) between defective and defect free areas of a body the method becomes more insensitive to disturbances. For this purpose a five electrode probe has been designed. An analysis of the statistical scatter indicates that the DCPD method is more suited to find the correct press settings than to look for defective specimens under production.

  • 104.
    Luukkonen, Petri
    et al.
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Hjortsberg, Erik
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Ericsson, Torsten
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Potential drop measurements of porosity in PM green bodies2003In: Powder Metallurgy, ISSN 0032-5899, E-ISSN 1743-2901, Vol. 46, no 4, p. 335-341Article in journal (Refereed)
    Abstract [en]

    The direct current potential drop method (DCPD) has been applied to four differently shaped green bodies made of iron based powders. The density and porosity has been measured in the bodies and correlated with potential drop. When the porosity is well known, a good correlation between potential drop and porosity is found. By comparison with literature it is concluded that the potential drop in green bodies varies more with porosity than in sintered bodies.

  • 105.
    Martinez-Perez, M L
    et al.
    ICMM CSIC, Spain.
    Mompean, F J
    ICMM CSIC, Spain.
    Peng, Ru
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Ruiz, J
    Depaartamento de Fisica de Materiales UPM, Spain.
    Borlado, C R
    ICMM CSIS, Spain.
    Atienza, J M
    Departamento de Fisica de Materiales UPS, Spain.
    Gil-Sevillano, J
    CEIT.
    Garcia-Hernadez, M
    ICMM CSIC, Spain.
    Elices, M
    Departamento de Fisica de Materiales UPM, Spain.
    Buslaps, T
    ESRF France.
    Strain Mapping in Cold-Drawn Pearlite Rods by High Energy Synchrotron Radiation and Thermal Neutron Diffraction2003In: Meca Sens,2003, 2003Conference paper (Refereed)
  • 106.
    Mikula, P
    et al.
    Nuclear Physics Institute Rez.
    Peng, Ru
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Asymmetric diffraaction geometry of the bent crystal monohromator - A way to improve the properties of strain diffractometers2002In: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 74, p. 204-206Article in journal (Refereed)
  • 107.
    Moverare, Johan
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Microstresses and anisotropic mechanical behaviour of duplex stainless steels2001Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The evolution of deformation during monotonic and cyclic loading of a two-phase material like duplex stainless steel is more complex than in a single-phase material. One reason for this is the microstresses formed due to differences in thermal and mechanical properties between the two phases. Another factor contributing to a complex load partitioning between the two phases is that hot and cold rolled duplex stainless steel exhibits anisotropic material properties. The aim of this thesis has therefore been to investigate the influence of microstresses and an isotropy on the mechanical properties of duplex stainless steels.

    The effect of microstresses was clearly revealed when X-ray diffraction was used to study the evolution of microstresses during cyclic loading. Even if the hardness and yield strength were found to be higher in the austenitic phase compared to the ferritic phase more plastic deformation occurs in austenite during cyclic tensile loading. This was also confirmed by transmission electron microscopy investigations of the dislocation structure in both phases. The main reason for the higher degree of plastic deformation in the austenitic phase is that the microstresses are tensile in this phase and compressive in the ferritic phase.

    Measurements of the crystallographic texture were used as input to theoretical predictions of both elastic and plastic anisotropy. The predicted anisotropic material properties were then used in finite element simulations to study the flow behavior and the load partitioning between phases during deformation in different loading directions. The experiments and the simulations show that the microstresses and the anisotropy make the load partitioning between the two phases dependent on the loading direction. For loading in the rolling direction, both phases deform plastically to the same degree, while more plastic deformation occurs in the austenitic phase during loading in the transverse direction. For loading in the 45°-direction more plastic deformation occurs in the ferritic phase.

    The anisotropic flow behaviour of the as-received material can be predicted from the crystallographic texture. However, it was found that prestraining introduces a transient work hardening behaviour during the second stage deformation, whjch causes an anisotropic flow behaviour immediately after yielding that cannot be described by the crystallographic texture. Instead the an isotropy can be associated with the rearrangement of the dislocation structure that occurs during changes in the loading path. Prestraining also alters the microstresses from being higher in the transverse direction to being higher in the rolling direction. At the same time the fatigue limit is changed from being higher in the rolling direction to being higher in the transverse direction. This study shows that microstresses have a significant influence on fatigue crack initiation and the fatigue limit of duplex stainless steels.

    List of papers
    1. Evolution of the residual stress state in a duplex stainless steel during loading
    Open this publication in new window or tab >>Evolution of the residual stress state in a duplex stainless steel during loading
    1999 (English)In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 47, no 9, p. 2669-2684Article in journal (Refereed) Published
    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.

    Place, publisher, year, edition, pages
    Elsevier, 1999
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-30076 (URN)10.1016/S1359-6454(99)00149-4 (DOI)15539 (Local ID)15539 (Archive number)15539 (OAI)
    Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-12-13
    2. Load sharing between austenite and ferrite in a duplex stainless steel during cyclic loading
    Open this publication in new window or tab >>Load sharing between austenite and ferrite in a duplex stainless steel during cyclic loading
    2000 (English)In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 31, no 6, p. 1557-1570Article in journal (Refereed) Published
    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.

    Place, publisher, year, edition, pages
    SpringerLink, 2000
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-30134 (URN)10.1007/s11661-000-0166-3 (DOI)15614 (Local ID)15614 (Archive number)15614 (OAI)
    Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-12-13
    3. Influence of elastic and plastic anisotropy on the flow behavior in a duplex stainless steel
    Open this publication in new window or tab >>Influence of elastic and plastic anisotropy on the flow behavior in a duplex stainless steel
    2002 (English)In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 33, no 1, p. 57-71Article in journal (Refereed) Published
    Abstract [en]

    The load partitioning between two phases in a cold-rolled duplex stainless steel has been experimentally studied in situ by X-ray diffraction, for different loading directions. It was found that the load partitioning between the two phases is dependent on the loading direction. For loading in the rolling direction, both phases deform plastically to the same degree, while more plastic deformation occurs in the austenitic phase during loading in the transverse direction. For loading in the 45-deg direction, more plastic deformation occurs in the ferritic phase. The strong crystallographic texture in the ferritic phase makes the material anisotropic, with a higher stiffness and yield strength in the transverse direction compared to the rolling direction. The measured texture was used as input to theoretical predictions of both elastic and plastic anisotropy. The plastic anisotropy was predicted by assuming intragranular slip as the main deformation mechanism. The predicted anisotropic material properties were then used in finite-element simulations to study the flow behavior of the material in different directions. The predicted flow behavior was found to be in good agreement with the experimentally observed load partitioning between the phases for loading in the rolling and transverse directions. However, the yield strength of the ferritic phase during loading in the 45-deg direction was found to be lower than what was predicted. The reason for this is the difference in slip characteristics in different sample directions, because of the morphological texture.

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-30019 (URN)10.1007/s11661-002-0005-9 (DOI)15470 (Local ID)15470 (Archive number)15470 (OAI)
    Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-12-13
    4. Deformation behaviour of a prestrained duplex stainless steel
    Open this publication in new window or tab >>Deformation behaviour of a prestrained duplex stainless steel
    2002 (English)In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 337, no 1-2, p. 25-38Article in journal (Refereed) Published
    Abstract [en]

    The anisotropic flow behaviour due to a change in strain path during uniaxial deformation of a duplex stainless steel has been investigated. The anisotropic flow behaviour of the as-received material could be predicted from the crystallographic texture. However, it was found that prestraining introduces a transient work hardening behaviour during the second stage deformation, which causes an anisotropic flow behaviour immediately after yielding that cannot be described by the crystallographic texture. Samples subjected to a coaxial second stage deformation show a small increase in flow stress and similar work hardening rate as in the monotonic loading. Samples subjected to noncoaxial second stage deformation show a pronounced transient stage characterised by early yielding and a high work hardening rate in the first part of the transient stage. Beyond the earliest stage of deformation a higher flow stress and a lower work hardening rate compared to monotonic loading is observed for the noncoaxial samples. The transient phenomena are discussed based on the measured internal stresses and the differences in dislocation structures in the two different phases.

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-30008 (URN)10.1016/S0921-5093(02)00022-9 (DOI)15451 (Local ID)15451 (Archive number)15451 (OAI)
    Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-12-13
    5. Anisotropic high cycle fatigue behaviour of duplex stainless steels: influence of microstresses
    Open this publication in new window or tab >>Anisotropic high cycle fatigue behaviour of duplex stainless steels: influence of microstresses
    2002 (English)In: International Journal of Materials Research - Zeitschrift für Metallkunde, ISSN 1862-5282, E-ISSN 2195-8556, Vol. 93, no 1, p. 7-11Article in journal (Refereed) Published
    Abstract [en]

    The anisotropic high cycle fatigue behaviour has been investigated for a duplex stainless steel in as-received and prestrained condition. It was found that the anisotropy of the fatigue limit is different from the anisotropy of yield strength. The main reason for this is the influence of microstresses on fatigue crack initiation. Fatigue cracks are seen to nucleate preferably in the austenite phase, which has tensile microstresses. Prestraining alters the microstresses from being higher in the transverse direction to being higher in the rolling direction. At the same time, the fatigue limit is changed from being higher in the rolling direction to being higher in the transverse direction.

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-30022 (URN)15473 (Local ID)15473 (Archive number)15473 (OAI)
    Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-12-13
  • 108.
    Moverare, Johan
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Residual Stresses and Fatigue in a Duplex Stainless Steel1999Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Duplex stainless steels, consisting of approximately equal amounts of austenite and ferrite, often combine the best features of austenitic and ferritic stainless steels. They generally have good mechanical properties, including high strength and ductility, and the corrosion resistance is often better than conventional austenitic grades. This has lead to a growing use of duplex stainless steels as a material in mechanically loaded constructions. However, detailed knowledge regarding its mechanical properties and deformation mechanisms are still lacking. In this thesis special emphasis has been placed on the residual stresses and their influence on mechanical behaviour of duplex stainless steels. Due to the difference in coefficient of therrnal expansion between the two phases, tensile rnicrostresses are found in the austenitic phase and balancing compressive rnicrostresses in the ferritic phase.

    The first part of this thesis is a literature survey, which will give an introduction to duplex stainless steels and review the fatigue properties of duplex stainless steels and the influence of residual stresses in two-phase material.

    The second part concems the evolution of the residual stress state during uniaxial loading. Initial residual stresses were found to be almost two times higher in the transverse direction compared to the rolling direction. During loading the absolute value of the rnicrostresses increased in the macroscopic elastic regime but started to decrease with increasing load in the macroscopic plastic regime. A significant increase of the rnicrostresses was also found to occur during unloading. Finite element simulations also show stress variation within one phase and a strong influence of both the elastic and plastic anisotropy of the individual phases on the simulated stress state.

    In the third part, the load sharing between the phases during cyclic loading is studied. X-ray diffraction stress analysis and transmission electron rnicroscopy 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 rnicrostresses present in the material. These rnicrostresses were also found to increase from 50 MPa to 160 MPa in the austenitic phase during the first 100 cycles when cycled in tension fatigue with a maximum load of 500 MPa. A sharpening of the texture was found in the ferritic phase, while a small decrease was found in the austenitic phase. The changes in texture lead to a reduction of the stiffness in the loading direction.

  • 109.
    Moverare, Johan
    et al.
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Odén, Magnus
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Anisotropic high cycle fatigue behaviour of duplex stainless steels: influence of microstresses2002In: International Journal of Materials Research - Zeitschrift für Metallkunde, ISSN 1862-5282, E-ISSN 2195-8556, Vol. 93, no 1, p. 7-11Article in journal (Refereed)
    Abstract [en]

    The anisotropic high cycle fatigue behaviour has been investigated for a duplex stainless steel in as-received and prestrained condition. It was found that the anisotropy of the fatigue limit is different from the anisotropy of yield strength. The main reason for this is the influence of microstresses on fatigue crack initiation. Fatigue cracks are seen to nucleate preferably in the austenite phase, which has tensile microstresses. Prestraining alters the microstresses from being higher in the transverse direction to being higher in the rolling direction. At the same time, the fatigue limit is changed from being higher in the rolling direction to being higher in the transverse direction.

  • 110.
    Moverare, Johan
    et al.
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Odén, Magnus
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Deformation behaviour of a prestrained duplex stainless steel2002In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 337, no 1-2, p. 25-38Article in journal (Refereed)
    Abstract [en]

    The anisotropic flow behaviour due to a change in strain path during uniaxial deformation of a duplex stainless steel has been investigated. The anisotropic flow behaviour of the as-received material could be predicted from the crystallographic texture. However, it was found that prestraining introduces a transient work hardening behaviour during the second stage deformation, which causes an anisotropic flow behaviour immediately after yielding that cannot be described by the crystallographic texture. Samples subjected to a coaxial second stage deformation show a small increase in flow stress and similar work hardening rate as in the monotonic loading. Samples subjected to noncoaxial second stage deformation show a pronounced transient stage characterised by early yielding and a high work hardening rate in the first part of the transient stage. Beyond the earliest stage of deformation a higher flow stress and a lower work hardening rate compared to monotonic loading is observed for the noncoaxial samples. The transient phenomena are discussed based on the measured internal stresses and the differences in dislocation structures in the two different phases.

  • 111.
    Moverare, Johan
    et al.
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Odén, Magnus
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Influence of elastic and plastic anisotropy on the flow behavior in a duplex stainless steel2002In: Metallurgical and Materials Transactions. A, ISSN 1073-5623, E-ISSN 1543-1940, Vol. 33, no 1, p. 57-71Article in journal (Refereed)
    Abstract [en]

    The load partitioning between two phases in a cold-rolled duplex stainless steel has been experimentally studied in situ by X-ray diffraction, for different loading directions. It was found that the load partitioning between the two phases is dependent on the loading direction. For loading in the rolling direction, both phases deform plastically to the same degree, while more plastic deformation occurs in the austenitic phase during loading in the transverse direction. For loading in the 45-deg direction, more plastic deformation occurs in the ferritic phase. The strong crystallographic texture in the ferritic phase makes the material anisotropic, with a higher stiffness and yield strength in the transverse direction compared to the rolling direction. The measured texture was used as input to theoretical predictions of both elastic and plastic anisotropy. The plastic anisotropy was predicted by assuming intragranular slip as the main deformation mechanism. The predicted anisotropic material properties were then used in finite-element simulations to study the flow behavior of the material in different directions. The predicted flow behavior was found to be in good agreement with the experimentally observed load partitioning between the phases for loading in the rolling and transverse directions. However, the yield strength of the ferritic phase during loading in the 45-deg direction was found to be lower than what was predicted. The reason for this is the difference in slip characteristics in different sample directions, because of the morphological texture.

  • 112.
    Moverare, Johan
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Odén, Magnus
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Influence of Texture and Anisotropy on Microstresses and Flow Behavior in a Duplex Stainless Steel During Loading2000In: Advances in X-ray Analysis, Vol. 44, 2000, p. 229-234Conference paper (Other academic)
    Abstract [en]

    The load partitioning between the two phases in a cold rolled duplex stainless steel sheet have been experimentally studied in situ during loading, via X-ray diffraction, for different loading directions. The microstresses in the two phases were found to decrease when loading in the transverse direction, while they increase during loading in the rolling and 45°-direction. Due to strong crystallographic texture in the ferritic phase the material is anisotropic with a higher stiffness and yield strength in the transverse direction compared to the rolling direction. The texture have been measured and used as input to theoretical predictions of both elastic and plastic anisotropy. The predicted anisotropic material properties have then been used in finite element simulations to study the flow behaviour of the material in different directions. The predicted flow behaviour was found to be in good agreement with the experimentally observed load partitioning between the phases for loading in the rolling and transverse direction. However, the yield strength of the ferritic phase during loading in the 45°-direction was found to be lower than what can be predicted by the crystallographic texture.

  • 113.
    Moverare, Johan
    et al.
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Odén, Magnus
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Micro-and Macrostreess Evolution in a Duplex Stainless Steel during Uniaxial Loading1999In: Proceedings of the Fifth European Conference on Residual Stresses : held September 28-30, 1999 in Delft-Noordwijkerhout, The Netherlands / [ed] A.J. Böttger, R. Delhez and E.J. Mittemeijer, 1999Conference paper (Refereed)
  • 114.
    Moverare, Johan
    et al.
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Odén, Magnus
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    The Stress State Evolution Measured in situ during Cyclic Loading of a Duplex Stainless Steel2000In: Proc. 6th International Conference on Residual Stresses (ICRS-6), 2000Conference paper (Other academic)
  • 115.
    Mångård, Måns
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Computerised tomography with optimised sensitivity to physical variations in the sampleManuscript (preprint) (Other academic)
    Abstract [en]

    Digital X-ray imaging techniques such as radiography or computerised tomography produce images of the interior of a sample. It is difficult to empirically find equipment settings such that the obtained images arc of high quality. This work presents an optimisation procedure for finding the optimal equipment settings for the imaging task at issue. It includes a suggested procedure for finding the optimiscd equipment settings even when complex samples arc investigated. To be able to mathematically optimisc the image quality, it is necessary to have a model of the X-ray imaging system together with an appropriate measure of image quality. This work proposes the ratios geometry-sensitivity/noise, density-sensitivity/noise and mass attenuation sensitivity/noise as measures of the physical image quality. A mathematical model of the imaging system was used to calculate and predict the ratios. The model predictions agreed well with the measured values. It is shown that the geometry- and density-sensitivity/noise ratios can be related to the signal-to-noise ratio and the traditional thickness (contrast) sensitivity.

    The weighted maximin method is used to obtain the optimal equipment settings. With the optimal settings, no improvement can be made without worsening at least one other sensitivity/noise ratio. It is demonstrated how the weights (penalties) can be selected to focus the sensitivity on different types of features in the investigated sample.

    The optimisation procedure is demonstrated on thermal barrier coatings investigated with CT. Optimised and non-optimiscd settings were used in the investigation. By optimising the equipment settings, the sensitivity/noise ratios are increased with approximately 100% for the selected X-ray path. With the optimised settings, the obtained CT images are of better quality and more features in the microstructure can be observed.

  • 116.
    Mångård, Måns
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Optimised performance of industrial high resolution computerised tomography2000Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The purpose of non-descructive enluation (NDE) is to acquire knowledge of the investigated sample. Digital x-ray imaging techniques such as radiography or computerised tomography (CI) produce images of the interior of a sample. The obtained image quality determines the possibility of detecting sample, ·elated features, e.g. details and flaws. this thesis presents a method of optinllsing the performance of industrial X-ray equipment for the imaging task at issue in order to obtain images with high quality.

    CT produces maps of the X-ray linear attenuation of the sample's interior. CT can produce two-dimensional cross-section images or three-dimensional images with volumetric information on the investigated sample. The image contrast and noise depend on both the investig-Ated sample and the equipment and settings used (X-ray tube potential, X-ray filtration, exposure time, etc.). Hence, it is vital to find the optimal equipment settings in order to obtain images of high quality.

    To be able to mathematically optimise the image guality, it is necessary to have a model of the X-ray imaging system together with an appropriate measure of image quality. The optimisation is performed with a developed model for an X-ray image-intensifier-based radiography system. The model predicts the mean value and variance of the measured signal level in the collected radiographic images. The traditionally used measure of physical image guality is the signal-to-noise ratio (SNR). To calculate the signal-to-noise ratio, a well-defined detail (flaw) is required. It was found that maximising the SNR leads to ambiguities, the optimised settings found by maximising the SNR were dependent on the material in the detail. When CT is performed on irregular shaped samples containing density and compositional variations, it is difficult to define which SNR to use for optimisation. This difficulty is solved by the measures of physical image quality proposed here, the ratios geometry-sensitivity/ noise, density-sensitivity/noise, and mass attenuation-sensitivity/noise. With these measures, a meiliod is presented that finds the optimal eguipment settings, where no improvement can be made without worsening at least one other sensitivity/noise ratio.

    This thesis includes modelling and verification of the sharpness of the CT system in terms of the modulation transfer function, MTF. Together with the limiting perception factor and the maximised SNR, the detectability limits for any specific contrasting detail in the centre of a cylindrical sample can be determined. It is also demonstrated that the model can be used to suppress beam hardening when collecting CT-data. When homogeneous samples are imaged, the model can in addition be used to make post-processing corrections for suppressing the beam hardening artefacts.

    Wavelet-based local tomography has been found to produce images with good accuracy from projection data only from a small region in a sample. Tlus technique is demonstrated on thermal barrier coatings, which contain internal cracks. With optimised eguipment settings and geometrical magnification of a region in the sample, wavelet-based local tomography produced high-resolution images of excellent quality. The increased resolution reveals features in the microstructure that cannot be resolved wiili traditional CT. This technigue will be a useful tool for characterisation of the microstructure in advanced materials.

    List of papers
    1. Modelling of an X-ray image-intensifier-based radiography system
    Open this publication in new window or tab >>Modelling of an X-ray image-intensifier-based radiography system
    1998 (English)In: Journal of X-Ray Science and Technology, ISSN 0895-3996, E-ISSN 1095-9114, Vol. 8, no 1, p. 31-50Article in journal (Refereed) Published
    Abstract [en]

    A model will be proposed for predicting the expected value and variance of the measured signal-level in collected radiographic images obtained with an image-intensifier-based X-ray radiography system. The model parameters are determined from both theoretical and experimental data and incorporate all parameters that can be varied by the system operator, except CCD-camera readout rate. The proposed model predicts the expected value and variance of the grey-level in the output image with high accuracy. It is also shown that it is very important to compensate for the inhomogeneous pixel sensitivity when comparing the variance of the signal-level in a pixel from sequentially collected images with the variance determined in a single image.

    Keywords
    Image intensifier, X-ray radiography, modelling
    National Category
    Medical and Health Sciences
    Identifiers
    urn:nbn:se:liu:diva-20933 (URN)22388425 (PubMedID)
    Available from: 2009-09-25 Created: 2009-09-25 Last updated: 2017-12-13
    2. Optimised detail detectability in computerised tomography
    Open this publication in new window or tab >>Optimised detail detectability in computerised tomography
    1998 (English)In: Journal of X-Ray Science and Technology, ISSN 0895-3996, E-ISSN 1095-9114, Vol. 8, no 1, p. 51-73Article in journal (Refereed) Published
    Abstract [en]

    It is of interest to know the minimum discernible detail size when performing non-destructive testing with high-resolution computerised tomography. But it is difficult to empirically find optimal parameter settings that maximise detectability for each individual imaging task. In this work a method to determine the optimal performance for a high-resolution computerised tomography system has been developed. It reveals the detectability limit for specific contrasting details in terms of imaged object diameter when the signal-to-noise ratio, SNRΔS,CT, between the contrasting detail and its surroundings has been maximised using optimal data collection parameter settings.

    This work includes modelling and verification of the total unsharpness of the CT-system in terms of modulation transfer-function, MTF. Together with the limiting perception factor and maximised SNRΔproj in the CT projection data, the detectability limits for any specific contrasting detail are determined as a function of imaged object material and geometry. Maximised SNRΔproj was obtained by optimising the parameters: X-ray source tube potential, X-ray filter, exposure time and optical aperture. The importance of using optimal settings when performing CT-investigations, especially when investigating objects with large diameters, is demonstrated.

    It was found that it is possible to predict the detectability for any specific contrasting detail. It was also discovered that the optimal settings for a given object diameter and material are dependent on the detail material. In some cases an improvement of the detail signal-to-noise-ratio was obtained by using a combination of X-ray filter materials. It was also found that SNRΔproj is very sensitive to the thickness of denser X-ray filter materials (higher atomic number and density).

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-88688 (URN)
    Available from: 2013-02-14 Created: 2013-02-14 Last updated: 2017-12-06
    3. Correction for beam hardening artefacts in computerised tomography
    Open this publication in new window or tab >>Correction for beam hardening artefacts in computerised tomography
    1998 (English)In: Journal of X-Ray Science and Technology, ISSN 0895-3996, E-ISSN 1095-9114, Vol. 8, no 1, p. 75-93Article in journal (Refereed) Published
    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.

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-88689 (URN)
    Available from: 2013-02-14 Created: 2013-02-14 Last updated: 2017-12-06
    4. Optimal conditions for X-ray imaging by mathematical simulation
    Open this publication in new window or tab >>Optimal conditions for X-ray imaging by mathematical simulation
    1999 (English)In: AIP Conference Proceedings 509 / [ed] Sarah Kallsen, Connie Nessa, Donald O. Thompson, Dale E. Chimenti, Linda Poore, 1999, p. 665-672Conference paper, Published paper (Refereed)
    Abstract [en]

    Image quality strongly affects the detectability, which is the possibility to detect defects. To obtain maximum detectability it is necessary to conduct the testing with optimal equipment settings. In radiography and computerized tomography based on conventional poly-energetic x-rays, the optimal equipment settings depend on the imaging task. An imaging task is defined as testing of a specific object with a specific defect, defined by composition and geometry. However, the optimal equipment settings (e.g., x-ray tube potential, x-ray filtration and exposure time) are tedious to find experimentally. This is particularly true for industrial applications due to the wide range of imaging tasks. In this work, mathematical models of the image collection process for radiography and computerized tomography have been developed. The objective has been to develop techniques to aid the imaging operator to find optimal imaging parameters. With the models it is possible to find the optimal settings and to predict the detectability of defects in terms of its size as a function of imaged object diameter and these are formulated in terms of detectable detail—object diameter diagram. It is shown that the image quality is very sensitive with respect to the settings, with e.g., slightly non-optimal choice of x-ray filter thickness leading to a loss of image quality that cannot be compensated by varying the x-ray tube potential. Furthermore, non-optimal conditions are found to considerably reduce the detectability of defects, especially for large objects.

    Keywords
    nondestructive testing, X-ray imaging, radiography, computerised tomography, modelling, digital simulation, optical transfer function, optimisation, random noise, image processing
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-30136 (URN)10.1063/1.1306113 (DOI)15616 (Local ID)1-56396-930-0 (ISBN)15616 (Archive number)15616 (OAI)
    Conference
    Review of progress in quantative nondestructive evaluation, 25-30 July, Montreal, Canada
    Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2013-02-14
    5. Computerised tomography with optimised sensitivity to physical variations in the sample
    Open this publication in new window or tab >>Computerised tomography with optimised sensitivity to physical variations in the sample
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Digital X-ray imaging techniques such as radiography or computerised tomography produce images of the interior of a sample. It is difficult to empirically find equipment settings such that the obtained images arc of high quality. This work presents an optimisation procedure for finding the optimal equipment settings for the imaging task at issue. It includes a suggested procedure for finding the optimiscd equipment settings even when complex samples arc investigated. To be able to mathematically optimisc the image quality, it is necessary to have a model of the X-ray imaging system together with an appropriate measure of image quality. This work proposes the ratios geometry-sensitivity/noise, density-sensitivity/noise and mass attenuation sensitivity/noise as measures of the physical image quality. A mathematical model of the imaging system was used to calculate and predict the ratios. The model predictions agreed well with the measured values. It is shown that the geometry- and density-sensitivity/noise ratios can be related to the signal-to-noise ratio and the traditional thickness (contrast) sensitivity.

    The weighted maximin method is used to obtain the optimal equipment settings. With the optimal settings, no improvement can be made without worsening at least one other sensitivity/noise ratio. It is demonstrated how the weights (penalties) can be selected to focus the sensitivity on different types of features in the investigated sample.

    The optimisation procedure is demonstrated on thermal barrier coatings investigated with CT. Optimised and non-optimiscd settings were used in the investigation. By optimising the equipment settings, the sensitivity/noise ratios are increased with approximately 100% for the selected X-ray path. With the optimised settings, the obtained CT images are of better quality and more features in the microstructure can be observed.

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-88697 (URN)
    Available from: 2013-02-14 Created: 2013-02-14 Last updated: 2013-02-14
    6. Optimised wavelet-based local tomography of thermal barrier coatings
    Open this publication in new window or tab >>Optimised wavelet-based local tomography of thermal barrier coatings
    (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Optimised wavelet-based local tomography has been found to be a useful non-destructive evaluation tool for studying the microstructure in thermal barrier coatings. Two-dimensional wavelet-based local tomography produced high-resolution images of regions inside the investigated samples. The investigated samples were cur from two thermal shock tested jet engine burner cans. The inside of the burner cans was coated with a thick thermal barrier coating consisting of a top coating made of partially stabilised zirconia (PSZ) and a bond coating (BC) of NiCoCrAlY. The coatings were manufactured with plasma spraying with two different spraying parameters. This resulted in samples with and without a segmented crack network in the as-sprayed top coating.

    The obtained wavelet-based local CT-imagcs of the investigated samples from the thermal shock tested burner cans reveal cracks and pores in the microstructure. The obtained pixel-sizes in the local CT-images were 4.0 μm and 3.1 μm respectively. Small or no improvements in resolution arc made when the pixel-size is in the vicintiy of the X-ray focal spot size, in this case 5 μm. A traditional CT-investigation, collecting global data that covers the whole cross-section of the sample, would have resulted in 2.6 and 6.8 times bigger pixel-sizes respectively. A CT-image reconstructed from global data would therefore not resolve all features seen in the wavelet-based local CT-images.

    To obtain CT-images with a high image quality a mathematical optimisation procedure is used to find the optimal equipment settings for collecting the CT-data. The geometry-sensitivity/noise, density-sensitivity/noise and mass attenuation-sensitivity/noise ratios are maximised using the weighted minimax method. The sensitivity/noise ratios are calculated using a mathematical model of the X-ray imaging system. The image quality is improved if the sample completely shades the detector and optimised equipment settings for this case are used. The sensitivity/noise ratios in the local CT-investigation of one of the samples are increased with at least 20% compared to if air gaps would have been present.

    A procedure to suppress ring artefacts in the reconstructed CT-images is presented. The procedure is found to give good results.

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-88707 (URN)
    Available from: 2013-02-14 Created: 2013-02-14 Last updated: 2013-02-14
  • 117.
    Mångård, Måns
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Optimised wavelet-based local tomography of thermal barrier coatingsManuscript (preprint) (Other academic)
    Abstract [en]

    Optimised wavelet-based local tomography has been found to be a useful non-destructive evaluation tool for studying the microstructure in thermal barrier coatings. Two-dimensional wavelet-based local tomography produced high-resolution images of regions inside the investigated samples. The investigated samples were cur from two thermal shock tested jet engine burner cans. The inside of the burner cans was coated with a thick thermal barrier coating consisting of a top coating made of partially stabilised zirconia (PSZ) and a bond coating (BC) of NiCoCrAlY. The coatings were manufactured with plasma spraying with two different spraying parameters. This resulted in samples with and without a segmented crack network in the as-sprayed top coating.

    The obtained wavelet-based local CT-imagcs of the investigated samples from the thermal shock tested burner cans reveal cracks and pores in the microstructure. The obtained pixel-sizes in the local CT-images were 4.0 μm and 3.1 μm respectively. Small or no improvements in resolution arc made when the pixel-size is in the vicintiy of the X-ray focal spot size, in this case 5 μm. A traditional CT-investigation, collecting global data that covers the whole cross-section of the sample, would have resulted in 2.6 and 6.8 times bigger pixel-sizes respectively. A CT-image reconstructed from global data would therefore not resolve all features seen in the wavelet-based local CT-images.

    To obtain CT-images with a high image quality a mathematical optimisation procedure is used to find the optimal equipment settings for collecting the CT-data. The geometry-sensitivity/noise, density-sensitivity/noise and mass attenuation-sensitivity/noise ratios are maximised using the weighted minimax method. The sensitivity/noise ratios are calculated using a mathematical model of the X-ray imaging system. The image quality is improved if the sample completely shades the detector and optimised equipment settings for this case are used. The sensitivity/noise ratios in the local CT-investigation of one of the samples are increased with at least 20% compared to if air gaps would have been present.

    A procedure to suppress ring artefacts in the reconstructed CT-images is presented. The procedure is found to give good results.

  • 118.
    Mångård, Måns
    et al.
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Hammersberg, Peter
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Optimal conditions for X-ray imaging by mathematical simulation1999In: AIP Conference Proceedings 509 / [ed] Sarah Kallsen, Connie Nessa, Donald O. Thompson, Dale E. Chimenti, Linda Poore, 1999, p. 665-672Conference paper (Refereed)
    Abstract [en]

    Image quality strongly affects the detectability, which is the possibility to detect defects. To obtain maximum detectability it is necessary to conduct the testing with optimal equipment settings. In radiography and computerized tomography based on conventional poly-energetic x-rays, the optimal equipment settings depend on the imaging task. An imaging task is defined as testing of a specific object with a specific defect, defined by composition and geometry. However, the optimal equipment settings (e.g., x-ray tube potential, x-ray filtration and exposure time) are tedious to find experimentally. This is particularly true for industrial applications due to the wide range of imaging tasks. In this work, mathematical models of the image collection process for radiography and computerized tomography have been developed. The objective has been to develop techniques to aid the imaging operator to find optimal imaging parameters. With the models it is possible to find the optimal settings and to predict the detectability of defects in terms of its size as a function of imaged object diameter and these are formulated in terms of detectable detail—object diameter diagram. It is shown that the image quality is very sensitive with respect to the settings, with e.g., slightly non-optimal choice of x-ray filter thickness leading to a loss of image quality that cannot be compensated by varying the x-ray tube potential. Furthermore, non-optimal conditions are found to considerably reduce the detectability of defects, especially for large objects.

  • 119.
    Mångård, Måns
    et al.
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Hammersberg, Peter
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Optimised detail detectability in computerised tomography1998In: Journal of X-Ray Science and Technology, ISSN 0895-3996, E-ISSN 1095-9114, Vol. 8, no 1, p. 51-73Article in journal (Refereed)
    Abstract [en]

    It is of interest to know the minimum discernible detail size when performing non-destructive testing with high-resolution computerised tomography. But it is difficult to empirically find optimal parameter settings that maximise detectability for each individual imaging task. In this work a method to determine the optimal performance for a high-resolution computerised tomography system has been developed. It reveals the detectability limit for specific contrasting details in terms of imaged object diameter when the signal-to-noise ratio, SNRΔS,CT, between the contrasting detail and its surroundings has been maximised using optimal data collection parameter settings.

    This work includes modelling and verification of the total unsharpness of the CT-system in terms of modulation transfer-function, MTF. Together with the limiting perception factor and maximised SNRΔproj in the CT projection data, the detectability limits for any specific contrasting detail are determined as a function of imaged object material and geometry. Maximised SNRΔproj was obtained by optimising the parameters: X-ray source tube potential, X-ray filter, exposure time and optical aperture. The importance of using optimal settings when performing CT-investigations, especially when investigating objects with large diameters, is demonstrated.

    It was found that it is possible to predict the detectability for any specific contrasting detail. It was also discovered that the optimal settings for a given object diameter and material are dependent on the detail material. In some cases an improvement of the detail signal-to-noise-ratio was obtained by using a combination of X-ray filter materials. It was also found that SNRΔproj is very sensitive to the thickness of denser X-ray filter materials (higher atomic number and density).

  • 120.
    Mångård, Måns
    et al.
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Hammersberg, Peter
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Sandborg, Michael
    Linköping University, Department of Medicine and Care, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Modelling of an X-ray image-intensifier-based radiography system1998In: Journal of X-Ray Science and Technology, ISSN 0895-3996, E-ISSN 1095-9114, Vol. 8, no 1, p. 31-50Article in journal (Refereed)
    Abstract [en]

    A model will be proposed for predicting the expected value and variance of the measured signal-level in collected radiographic images obtained with an image-intensifier-based X-ray radiography system. The model parameters are determined from both theoretical and experimental data and incorporate all parameters that can be varied by the system operator, except CCD-camera readout rate. The proposed model predicts the expected value and variance of the grey-level in the output image with high accuracy. It is also shown that it is very important to compensate for the inhomogeneous pixel sensitivity when comparing the variance of the signal-level in a pixel from sequentially collected images with the variance determined in a single image.

  • 121.
    Odén, Magnus
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Almer, J.
    Håkansson, G.
    Olsson, M A
    Microstructure - property relationships in arc-evaporatedCr-N coatings2000In: Thin solid films : an international journal on the science and technology of thin and thick films, ISSN 0563-4652, p. 377-378-407-412Article in journal (Refereed)
    Abstract [en]

      

  • 122.
    Odén, Magnus
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Almer, J
    IKP, Konstruktionsmaterial Linköpings unversitet.
    Håkansson, Greger
    Bodycote Värmebehandling AB Linköping.
    Olsson, M
    Dalarna University .
    Microstructure-property relationships in arc-evaporated Cr-N coatings2000In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 377-378, p. 407-412Article in journal (Refereed)
    Abstract [en]

    Chromium nitride (Cr-N) coatings have received increased attention for tribological applications due to their favorable properties including wear resistance, toughness and oxidation resistance. These properties, in turn, can be strongly influenced by the coating microstructure and residual stress resulting from deposition and subsequent processing operations. In this study these microstructure-property correlations are investigated in Cr-N coatings grown by arc-evaporation. Prominent as-deposited features include formation of metastable amounts of the cubic d-CrN phase, and high levels of compressive residual stress and defect density. During annealing up to 650 ░C the residual stress and defect density decrease substantially, accompanied by a diffusion-based d-CrN to ▀-Cr2N phase transformation and equiaxed grain formation. The effects of these microstructural modifications on the hardness, fracture and wear properties of the coatings are evaluated using a combination of nanoindentation, scratch and pin-on-disk testing. Appreciable changes in these properties are found after annealing, and are correlated to the Cr-N microstructure. As-deposited coating hardness is enhanced by high levels of lattice defect density, with both decreasing concomitantly during annealing. Scratch results show that resistance to cohesive flaking is increased by annealing, suggesting ductility increases via defect annealing and equiaxed grain formation. Finally, the wear rate under dry sliding generally increased with annealing temperature, although wear rates of all Cr-N coatings significantly outperformed TiN tested under identical conditions.

  • 123.
    Odén, Magnus
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Almer, Jonathan
    IKP, Konstruktionsmaterial Linköpings universitet.
    Håkansson, Greger
    Tixon Brukens Sverige AB Linköping.
    The effects of bias voltage and annealing on the microstructure and residual stress of arc-evaporated CR-N coatings1999In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 120-121, p. 272-276Article in journal (Refereed)
  • 124.
    Odén, Magnus
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Ericsson, Claes
    Tixon Brukens Sverige AB Linköping.
    Håkansson, Greger
    Tixon Brukens Sverige AB Linköping.
    Ljungcrantz, Henrik
    Tixon Brukens Sverige AB Linköping.
    Microstructure and mechanical behavior of arc-evaporated Cr-N coatings1999In: Surface & Coatings Technology, ISSN 0257-8972, E-ISSN 1879-3347, Vol. 114, p. 39-51Article in journal (Refereed)
  • 125.
    Odén, Magnus
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Gall, D
    Dept of Materials Science University of Illinois.
    Shin, C-S
    Dept of Materials Science University of Illinois.
    Spilla, T
    Dept of Materials Science University of Illinois.
    Senna, M J H
    Dept of Materials Science University of Illinois.
    Greene, J E
    Dept of Materials Science University of Illinois.
    Petrov, I
    Dept of Materials Science University of Illinois.
    Growth of single-crystal CrN on MgO(001): Effects of low-energy ion-irradiation on surface morphological evolution and physical properties2002In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 91, no 6, p. 3589-3597Article in journal (Refereed)
    Abstract [en]

    CrN layers, 0.5 ╡m thick, were grown on MgO(001) at Ts=570-775░C by ultrahigh vacuum magnetically unbalanced magnetron sputter deposition in pure N2 discharges at 20 mTorr. Layers grown at Ts=700░C are stoichiometric single crystals exhibiting cube-on-cube epitaxy: (001)CrN(001)MgO with [100]CrN[100]MgO. At higher temperatures, N2 desorption during deposition results in understoichiometric polycrystalline films with N fractions decreasing to 0.35, 0.28, and 0.07 with Ts=730, 760, and 775░C, respectively. The surface morphologies of epitaxial CrN(001) layers were found to depend strongly on the incident ion-to-metal flux ratio JN2+/JCr which was varied between 1.7 and 14 with the ion energy maintained constant at 12 eV. The surfaces of layers grown with JN2+/JCr=1.7 consist of self-organized square-shaped mounds, due to kinetic roughening, with edges aligned along orthogonal <100> directions. The mounds have an average peak-to-valley height =5.1 nm and an in-plane correlation length of =0.21 ╡m. The combination of atomic shadowing by the mounds with low adatom mobility results in the formation of nanopipes extending along the growth direction. Increasing JN2+/JCr to 14 leads, due to increased adatom mobilities, to much smoother surfaces with =2.5 nm and =0.52 ╡m. Correspondingly, the nanopipe density decreases from 870 to 270 ╡m-2 to <20 ╡m-2 as JN2+/JCr is increased from 1.7 to 6 to 10. The hardness of dense CrN(001) is 28.5▒1 GPa, but decreases to 22.5▒1 GPa for layers containing significant nanopipe densities. The CrN(001) elastic modulus, 405▒15 GPa, room-temperature resistivity, 7.7╫10-2 cm, and relaxed lattice constant, 0.4162▒0.0008 nm, are independent of JN2+/JCr. ⌐ 2002 American Institute of Physics.

  • 126.
    Peng, Ru
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Chai, G C
    Sandvik Materials Technology Sandviken.
    Jia, N
    School of Materials and Metallurgy Northeastern University, Shenyang.
    Johansson, Sten
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Low cycle fatigue damage and phase interactions in a super duplex stainless steel2006In: Fatigue 2007,2007, 2006Conference paper (Other academic)
  • 127.
    Peng, Ru
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Chai, G
    RD SFM Sandvik Materials Technology, Sandviken.
    Jia, N
    School of Materials and Metallurgy Northeastern University, Shenyang.
    Wang, Y D
    School of Materials and Metallurgy Northeasterna University, Shenyang.
    Johansson, Sten
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Low Cycle Fatigue Damage and Phase Interactions in a Superduplex Stainless Steel2007In: Fatigue 2007 The 6th Engineering Integrity Society International Conference on Durability and Fatigue,2007, 2007Conference paper (Refereed)
  • 128.
    Peng, Ru
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    D Y, Cong
    Key Laboratory of Electromagnetic Processin gof Materials Notheastern University, Shenyang.
    Zetterström, P
    The Studsvik Neutron Research Laboratory Uppsala University.
    Wang, Y D
    Dept of Mateials Science Engineering Northeastern University, Sheyang.
    Delaplane, R
    The Studsvik Neutron Research Laboratory Uppsala University.
    Zhao, X
    Key Laboratory of Electromagnetic Processing of Materials Northeastern University, Shenyang.
    Zuo, L
    Key Laboratory of Electromagnetic Processing of Materials Northeastern University, Shenyang.
    Crystal structure and phase transformation in Ni53Mn 25Ga22 shape memory alloy from 20 K to 473 K2005In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 87, no 11Article in journal (Refereed)
    Abstract [en]

    The crystal structures, magnetic structures, and phase transformation of the off-stoichiometric Ni53 Mn25 Ga22 were studied by neutron powder diffraction at different temperatures. It is shown that Ni53 Mn25 Ga22 has a tetragonal I4/mmm structure from 20 K to 403 K. An abrupt jump in unit-cell volume around room temperature, corresponding to an endothermic peak in the differential scanning calorimetry curve, was observed. This indicates a pretransformation in the martensitic phase of Ni53 Mn25 Ga22, which is completely different from the phase transformation in the stoichiometric Ni2 MnGa. The sequence of structural transformation in Ni53 Mn25 Ga22 is closely related to its intrinsic temperature-dependent magnetic structure. © 2005 American Institute of Physics.

  • 129.
    Peng, Ru
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Deng, J N
    Liaonin gKey Laboratory of New Materials Technology Northeastern University, Shenyang.
    Fundenberger, J J
    Insitut Superieur de Genie Mecanique et productique Universite de Metz.
    Bouzy, E
    Insitut Superieur de Genie Mecanique et Productique University de Metz.
    He, C S
    Liaoning Key Laboratory of New Mateials Technology Northeastern University, Shenyang.
    Zhang, D Z
    Institute of Metala Research Shinese Academy of Science, Shenyang.
    Wang, Y D
    Lianoning Key Laboratory of New Materials Technology Northeastern University, Shenyang.
    Texture and Local Textures in Severely Cold-Rolled and Annealed Ultra-rfine-Grained FeCo Alloy2005In: ICOTOM 14,2005, 2005Conference paper (Other academic)
  • 130.
    Peng, Ru
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Ericsson, Torsten
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Johansson, Sten
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Thorsson, Lena
    IUC Karlskoga AB .
    Residual Stresses in Metallic Samples Produced byh Laser FreeForm Fabrication2004In: 10th Swedish Neutron Scattering Society Meeting,2004, 2004Conference paper (Other academic)
  • 131.
    Peng, Ru
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Fernandez, R
    Deåt of Physical metallurgy CSIC, Spain.
    Bruno, G
    Institut Laue-Langevin France.
    Gonzalez-Doncel, G
    Dept of Physical Metallurgy CSIC, Spain.
    Effect of Heat Treatments on the Residual Stress State of 6061Al-15vol%SiCw Composite2004In: Journal of Neutron Research, ISSN 1023-8166, E-ISSN 1477-2655, Vol. 12, p. 105-109Article in journal (Refereed)
  • 132.
    Peng, Ru
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Gibmeier, Jens
    Inst of Materials Engineering University of Kassel.
    Eulert, S
    Inst of Materials Engineering University of Kassel.
    Johansson, Sten
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Chai, G C
    Sandvik Materials Technology Sandviken.
    In-sity X-ray diffraction study of load partitioning and microyielding for the super duplex stainless steel SAF2507 (UNS S32750)2006In: ECRS7 - The 7th European Conference on Residual Stresses,2006, 2006Conference paper (Other academic)
  • 133.
    Peng, Ru
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Jia, N
    School of Materials and Metalluryg Northeastern University, Shenyang.
    Wang, Y D
    School of Materials and Metallurgy Northeastern University, Shenyang.
    Chai, G C
    R D Sandvik Materials Technology, Sandviken.
    Johansson, Sten
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Wang, G
    School of Materials and Metallurgy Northeastern University, Shenyang.
    Liaw, P K
    dept of Materials Science and Engineering University of Tennessee, Knoxville.
    Interactions between the phase stress and the grain-orientation-dependent stress in duplex stainless steel during deformation2006In: Acta Materialia, ISSN 1359-6454, E-ISSN 1873-2453, Vol. 54, no 15, p. 3907-3916Article in journal (Refereed)
    Abstract [en]

    The development of phase stress and grain-orientation-dependent stress under uniaxial compression was investigated in a duplex stainless steel consisting of austenite and ferrite. Using in situ neutron diffraction measurements, the strain response of several h k l planes to the applied compressive stress was mapped as a function of applied stress and sample direction. Analysis based on the experimental results and elastoplastic self-consistent simulations shows that phase stresses of thermal origin further increase during elastic loading but decrease with increased plastic deformation. Grain-orientation-dependent stresses become significant in both austenite and ferrite after loading into the plastic region. After unloading from the plastic regime, a considerable intergranular stress remains in the austenitic phase and dominates over the phase stress. This study provides fundamental experimental inputs for future micromechanical modeling aiming at the evaluation and prediction of the mechanical performance of multiphase materials. © 2006 Acta Materialia Inc.

  • 134.
    Peng, Ru
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Johansson, Sten
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Ericsson, Torsten
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Thorsson, Lena
    IUC Karlskoga AB Karlskoga.
    Residual Stresses Induced by Laser FreeForm Fabrication2005In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 490-491, p. 334-339Article in journal (Refereed)
  • 135.
    Peng, Ru
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Johansson, Sten
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Thorsson, Lena
    IUC Karlskoga AB .
    Ericsson, Torsten
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Residual stresses Induced by Laser FreeForm Fabrication2004In: ICRS7,2004, 2004Conference paper (Refereed)
  • 136.
    Peng, Ru
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Liu, T
    Shenyang National Laboratory for Materials Science Chinese Academy of Sciences, Shenyang, China.
    Wang, S D
    Studsvik Neutron Research laboratory, Nyköping.
    Wu, S D
    Shenyang National Laboratory for Materials Science Chinese Academy of Sciences.
    Huang, C X
    Shenyang National Laboratory for Materials Science Chinese Academy of Sciences,.
    Jiang, C B
    Shenyang National Laboratory för Materials Science Chinese Academy of Sciences.
    Li, S X
    Shenyang National Laboratory for Materials Science Chinese Academy of Sciences.
    Textures and mechanical behavior of Mg-3.3%Li alloy after ECAP2004Article in journal (Refereed)
    Abstract [en]

    The texture evolutions of the Mg-3.3%Li alloy after the equal channel angular pressing (ECAP) with two different routes have been investigated by neutron diffraction. The substantial enhancement of mechanical properties of the alloy after ECAP has been explained by the texture modifications and microstructure changes.

  • 137.
    Peng, Ru
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    M, Ericsson
    University of Trollhättan.
    Nylén, P
    University of Trollhättan, Volvo Aero Corp, Trollhättan.
    Berglund, D
    SSAB HardTech AB, Luleå.
    Three Dimensional Simulation of Robot path, Heat Trnasfer and Residual stresses of a welded Part with Complex Geometry2005In: International Journal for the Joining of Materials, ISSN 0905-6866, Vol. 17, no 2, p. 42-51Article in journal (Refereed)
  • 138.
    Peng, Ru
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Martinez-Perez, M L
    ICMM, CSIC Spain.
    Mompean, F J
    ICMM, ISic Spain.
    Ruiz, J
    Departemento de Fisica de Materiales, UPM Spain.
    Borlando, R C
    ICMM, CSIC Spain.
    Atienza, J M
    Departemento de Fisica de Materiales, UPM Spain.
    Gil-Sevillano, J
    CEIT Spain.
    Garcia-Hernandez, M
    ICMM, CSIC Spain.
    Elices, M
    Departemento de Fisica de Materiales, UPM Spain.
    Buslaps, T
    ESRF France.
    Residual Stresses in Cold-drawn Pearlite Rods by High Energy Synchrotron Radiation and Thermal Neutron Diffraction2004In: Journal of Neutron Research, ISSN 1023-8166, E-ISSN 1477-2655, Vol. 12, p. 175-180Article in journal (Refereed)
  • 139.
    Peng, Ru
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Odén, Magnus
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Wang, Y D
    Studsvik Neutron Research Lab Uppsala university.
    Johansson, Sten
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Integranular Strains in a Deformed Austenitic Stainless Steel2000In: ICRS-6,2000, London: IOM Communications , 2000Conference paper (Refereed)
  • 140.
    Peng, Ru
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Odén, Magnus
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Wang, Y D
    Studsvik Neutron Research Lab Uppsala University.
    Johansson, Sten
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Intergranular strains and plastic deformation of an austenitic stainless steel2002In: Materials Science & Engineering: A, ISSN 0921-5093, E-ISSN 1873-4936, Vol. 334, no 1-2, p. 215-222Article in journal (Refereed)
    Abstract [en]

    Intergranular strains due to tensile plastic deformation were investigated in a sheet material of austenitic stainless steel. The objective was to study the development of residual intergranular strains in samples unloaded from the intermediate and large plastic deformation regimes for which few theoretical and experimental studies were available. By using neutron diffraction, residual lattice strain distribution as a function of sample direction was mapped for a number of crystallographic planes. Deformation microstructures were examined by both transmission electron microscopy and the electron back scattering pattern technique. Residual intergranular strains were observed in samples deformed significantly beyond the elastic limit and the strains varied with sample directions as well as the amount of applied plastic strain. In addition, a different tendency of intergranular strain evolution was observed after large plastic deformation, which could be attributed to the change of dominant plastic deformation mode from slip to mechanical twinning. The results are discussed based on the observed deformation microstructure studies. ⌐ 2002 Elsevier Science B.V. All rights reserved.

  • 141.
    Peng, Ru
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Rode, Nils
    Intitute of Materials Technolgy University of Kassel.
    Odén, Magnus
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Gibmeier, Jens
    Institute of Materials Technology University of Kassel.
    Scholtes, B
    Institute of Materials Technology University of Kassel.
    Characterisation of residual stress distribution in clinching joints of carbon steel by diffraction methods2003In: Materials Science and Technology, ISSN 0267-0836, E-ISSN 1743-2847, Vol. 19, no 3, p. 336-342Article in journal (Refereed)
    Abstract [en]

    Sheet joints of carbon steel fabricated by two different clinching methods, namely TOX and Eckold, have been investigated. The holding force of the joints was determined by shear tension tests and the deformation microstructure was characterised using optical microscopy. The surface residual stress and mean residual stress distributions as a function of increasing distance from the outer diameter of the interlock button were mapped by X-ray and neutron diffractometry, respectively.The Eckold joints showed more severe joint distortion in the form of global sheet bending, but nevertheless possessed higher shear tension strength than the TOX joints. Characteristic residual stress distributions depending on the clinching method were found in both the TOX and Eckold joints. The observed residual stress distributions have been attributed to the different die construction employed by the two methods, which permitted different degrees of plastic deformation during clinching.

  • 142.
    Peng, Ru
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Wang, Y D
    Inst of New Materials Technology Northeastern University, Shenyang.
    Almer, J
    Advanced Photon Source Argonne National Laboratory.
    Odén, M
    Engineering Materials Luleå Tekniska Universitet.
    Liu, Y D
    Inst of New Materials Technology Northeastern University, Shenyang.
    Zuo, L
    Inst of New Materials Technology Northeastern University, Shenyang.
    Determination of Grain-Orientation-Dependent Stress in Coatings2005In: Diffusion and defect data, solid state data. Part A, Defect and diffusion forum, ISSN 1012-0386, E-ISSN 1662-9507, Diffusion and defect data, solid state data.. P. B,. Solid state phenomena, Vol. 105, p. 107-112Article in journal (Refereed)
    Abstract [en]

    Quantitative interpretations of the so-called non-linear lattice strain distributions observed in coatings and thin films are important not only for determining the macro- and micro-stress fields, but also for inferring the active mechanisms of grain interactions during various deposition processes. In this paper, we present a method, which determines simultaneously both the macro- and micro-stress fields in the coatings and thin films. This method is extended from the previous stress-orientation distribution function (SODF) analysis method, which has already been used for residual stress analysis in bulk materials subjected to rolling and fatigue deformation. The validity of analysis method is demonstrated through measurements of lattice strains by high-energy x-ray and analysis of grain-orientation-dependent stresses in a CrN coating

  • 143.
    Peng, Ru
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Wang, Y D
    Key Laboratory of Electromagnetic Processing of Materials Northeastern University, Shenyang.
    Chai, G C
    FU, SFM Sandvik Materials Technology, Sandviken.
    Jia, N
    Key Laboratory of Electromagnetic Processing of Materials Northeastern University, Shenyang.
    Johansson, Sten
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Wang, G
    Key Laboratory of Electromagnetic Processing of Materials Northeastern University, Shenyang.
    Lattice strain evolution and phase interaction in a super duplex stainless steel under uniaxial loading2006In: ECRS7,2006, 2006Conference paper (Other academic)
  • 144.
    Peng, Ru
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Wang, Y D
    Studsvik Neutron Research Lab Uppsala university.
    Chai, G C
    Sandvik Materials Technology Sandviken.
    Jia, N
    Studsvik Neutron Research Laboratory Uppsala University.
    Johansson, Sten
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Wang, G
    School of Materials and Metallurgy Northeastern University, Shenyang.
    On the development of grain-orintatin-dependent and inter-phase stresses in a super duplex stainless steel under uniaxial loading2006In: ECRS7 - The 7th European Conference on Residual Stresses,2006, 2006Conference paper (Other academic)
  • 145.
    Peng, Ru
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Wang, Y D
    Neutron Research Lab Studsvik, Uppsala University.
    McGreevy, R L
    Neutron Research Lab Studsvik, Uppsala University.
    Development of Integranular Stress of Annealed Stainless Steel2001In: Journal of Neutron Research, ISSN 1023-8166, E-ISSN 1477-2655, Vol. 9, p. 331-336Article in journal (Refereed)
  • 146.
    Peng, Ru
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Wang, Y D
    Key Loaboratory for anisotropy and Texture of Materials Northeastern University, Shenyang.
    Nie, Z D
    Key Laboratory for Anisotropy and Texture of Materials Northeastern University, Shenyang.
    Oliver, E C
    ISIS Facility CCLRC rutherford Appleton Loaboratory Chilton, Didcot.
    Johansson, Sten
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Liu, Y D
    Key Laboratory for Anisotropy and Texture of Materials Northeastern University, Shenyang.
    Ren, Y D
    X-ray Science Division Argonne National Laboratory, USA.
    Jorgensen, J D
    Intense Pulsed Neturon Source Argonne National Laboratory, USA.
    Fieramosca, J
    Intense Pulsed Neutron Source Argonne National Laboratory, USA.
    In situ neutron diffraction study of micromechanical interactions and phase transformation in Ni-Mn-Ga alloy under uniaxial and hydrostatic stress2008In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 20, no 10Article in journal (Refereed)
    Abstract [en]

    This paper deals with the experimental study of stress-induced phase transformation in a polycrystalline Ni-Mn-Ga alloy under uniaxial compression and its powder under hydrostatic compression. In situ neutron diffraction experiments were employed to follow changes in the structure and lattice strains caused by the applied stresses. Large lattice strains that are dependent on the lattice planes or grain orientations were observed in the parent Heusler phase for both the bulk material and the powder sample. The development of such anisotropic strains and the influence of external load conditions are discussed in the paper. © IOP Publishing Ltd.

  • 147.
    Peng, Ru
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Wang, Y D
    Studsvik Neutron Research Laboratory Nyköping.
    Odén, Magnus
    Engineering Materials Luleå University.
    Almer, J
    Advanced Photon Soruce Argonne National Laboratory, Argonne.
    Residual Stress Analysis in both As-deposited and Annealed CrN Coatings2004In: ICRS7,2004, 2004Conference paper (Refereed)
  • 148.
    Peng, Ru
    et al.
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Wang, Y D
    Studsvik Neutron Research Laboratory, Uppsala universitet, Nyköping , Sweden.
    Odén, Magnus
    Engineering Materials, Luleå University, Luleå, Sweden.
    Almer, J
    Advanced Photon Source Argonne National Laboratory, Argonne, IL, USA.
    Residual Stress Analysis in both As-deposited and Annealed CrN Coatings2005In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 490-491, p. 643-648Article in journal (Refereed)
    Abstract [en]

    In this paper, we report on residual stress analysis in physical vapour deposited (PVD) CrN coatings. Two 9 µm thick coatings were grown on tool steel substrates with bias voltages of - 50 V and -300 V, respectively. High-energy (E=80 keV) synchrotron radiation measurements have been performed to investigate residual stresses in both as-deposited and annealed CrN coatings. To understand the origins of non-linear distribution of lattice strain versus sin2ψ for certain (hkl) planes in both coatings, a stress orientation distribution function (SODF) analysis has been carried out, which yields grain-orientation-dependent residual stresses. The results are compared to previous analyses using Reuss and Vook-Witt models on the as-deposited coatings.

  • 149.
    Peng, Ru
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mechanical Engineering, Engineering Materials.
    Wang, Yandong
    Dept of Materials Science and Engineering Northeastern University, Shenyang.
    Zetterström, Per
    Studsvik Neutron Reseach Laboratory Uppsala University.
    Jia, Nan
    Dept of Materials Science and Engineering Northeastern University, Shenyang.
    Cong, Daoyong
    Dept of Materials Science and Engineering Northeastern University, Shenyang.
    Structure Characterization and Stress Measurement by Neutron Diffraction2005In: China-Sweden Symposium on Materials Science,2005, 2005Conference paper (Other academic)
  • 150.
    Schlauer, Christian
    Linköping University, Department of Mechanical Engineering, Engineering Materials. Linköping University, The Institute of Technology.
    Near-surface residual stresses and microstructural changes after turning of a nickel-based superalloy2003Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Nickel-based superalloys are precipitation hardened alloys with complex compositions. They are used in aircraft engines and land-based gas turbines in load-bearing structural components that are exposed to high temperatures. Failure mechanisms in this environment are high and low cycle fatigue, creep, and corrosion.

    During manufacturing, residual stresses are often introduced into the material due to inhomogeneous plastic deformations, both intentionally and unintentionally. One such manufacturing process is metal cutting, which introduces residual stresses in the surface layer. The stress state in the near-surface zone of components is of special interest as the surface often experiences peak loads and cracks have their starting point there.

    In this thesis, near-surface residual stress distributions and microstructural changes are studied in the nickel-based superalloy Inconel 718 for two different turning operations, face grooving and facing. Process variables are in both cases cutting speed and feed that have been varied between (10 and 1200) m/min and (0.01 and 0.5) mm, respectively.

    The first turning technique face grooving, which gives cutting conditions similar to orthogonal cutting, showed a clear dependency of the residual stresses on the cutting speed. The tensile stress at the surface, the maximum compressive stress below the surface, and the thickness of the affected layer increase with increasing cutting speed. The tensile stresses are constrained to a thin surface layer and compressive residual stresses below the surface dominate the depth profile of the residual stresses. Only at low cutting speed, residual stresses were largely avoided.

    The second turning technique facing confirmed the dependency of the residual stresses on the cutting speed and revealed a similar dependency on the feed. Microstructural investigations of near-surface cross-sections by means of transmission electron microscopy showed a zone where the grains had undergone plastic deformation, indicated by slip bands. On top of this layer, a surface layer exists where the grain size has radically decreased to between 50 nm and 130 nm. The grain size of the nanocrystalline layer is fairly constant for a certain cutting speed and feed but depends on these cutting parameters. An increase in cutting speed and feed leads to larger grains in the nanocrystalline layer.

    List of papers
    1. Residual Stresses in a Nickel-based Superalloy Introduced by Turning
    Open this publication in new window or tab >>Residual Stresses in a Nickel-based Superalloy Introduced by Turning
    2002 (English)In: Materials Science Forum, ISSN 0255-5476, E-ISSN 1662-9752, Vol. 404-407, p. 173-178Article in journal (Refereed) Published
    Abstract [en]

    Near-surface residual stress distributions in the nickel-based superalloy Inconel 718 that originate from the machining operation turning are studied. The turning process that is used in the experiments is face grooving which gives quasi-orthogonal cutting conditions. Cutting speed and feed have been varied to investigate their effects on the residual stress state. Tensile residual stresses with a maximum of 1300 MPa were found at the surface that turn rapidly into compressive residual stresses of up to -800 MPa. The depth distributions of the residual stresses are presented and discussed with respect to observations made by optical and transmission electron microscopy.

    Keywords
    residual stress, machining, superalloy, microstructure
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-24027 (URN)10.4028/www.scientific.net/MSF.404-407.173 (DOI)3582 (Local ID)3582 (Archive number)3582 (OAI)
    Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2017-12-13
    2. Residual stress evolution and near-surface microstructure after turning of the nickel-based superalloy Inconel 718
    Open this publication in new window or tab >>Residual stress evolution and near-surface microstructure after turning of the nickel-based superalloy Inconel 718
    2005 (English)In: Zeitschrift für Metallkunde, ISSN 0044-3093, Vol. 96, no 4, p. 385-392Article in journal (Refereed) Published
    Abstract [en]

    Turning experiments have been carried out with the cutting speed and feed as variables that were systematically varied between 10 m min−1 and 1200 m min−1, and 0.1 mm and 0.5 mm, respectively, while all other cutting parameters were held constant. The arising residual stress distributions are presented and the influence of the varied machining parameters is investigated. Compressive residual stresses dominate the depth profiles but are often accompanied by a thin tensile residual stress layer at the surface. Microstructural investigations of near-surface cross-sections by means of transmission electron microscopy showed a zone where the grains had undergone plastic deformation, indicated by slip bands. On top of this layer, a surface layer exists where the grain size has radically decreased to only 50 nm to 130 nm. The grain size of the nanocrystalline layer is fairly constant for a certain cutting speed and feed, but depends on these cutting parameters. An increase in cutting speed and feed leads to larger grains in the nanocrystalline layer.

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-28422 (URN)13560 (Local ID)13560 (Archive number)13560 (OAI)
    Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-12-13
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