The Experts below are selected from a list of 41625 Experts worldwide ranked by ideXlab platform
Geunsu Jung - One of the best experts on this subject based on the ideXlab platform.
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Liquid Zn assisted embrittlement of advanced high strength steels with different microstructures
Metals and Materials International, 2016Co-Authors: Geunsu JungAbstract:In the present study, liquid metal embrittlement (LME) phenomenon during high temperature deformation was investigated for 3 grades of Zn-coated high strength automotive steel sheets consisting of different phases. Hot tensile tests were conducted for each alloy to compare their LME sensitivities at temperature ranges between 600 and 900 °C with different Strain Rates. The results suggest that Zn embrittles all the Fe-alloy system regardless of constituent phases of the steel. As hot tensile temperature and Strain Rate Increase, LME sensitivity Increases in every alloy. Furthermore, it is observed that the critical Strain, which is experimentally thought to be 0.4% of Strain at temperatures over 700 °C, is needed for LME to occur. It is observed via TEM work that Zn diffuses along grain boundaries of the substRate alloy when the specimen is Strained at high temperatures. When the specimen is exposed to the Strain more than 0.4% at over 700 °C, the segregation level of Zn at grain boundaries seems to become critical, leading to occurrence of LME cracks.
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Liquid Zn assisted embrittlement of advanced high strength steels with different microstructures
Metals and Materials International, 2016Co-Authors: Geunsu JungAbstract:In the present study, liquid metal embrittlement (LME) phenomenon during high temperature deformation was investigated for 3 grades of Zn-coated high strength automotive steel sheets consisting of different phases. Hot tensile tests were conducted for each alloy to compare their LME sensitivities at temperature ranges between 600 and 900 °C with different Strain Rates. The results suggest that Zn embrittles all the Fe-alloy system regardless of constituent phases of the steel. As hot tensile temperature and Strain Rate Increase, LME sensitivity Increases in every alloy. Furthermore, it is observed that the critical Strain, which is experimentally thought to be 0.4% of Strain at temperatures over 700 °C, is needed for LME to occur. It is observed via TEM work that Zn diffuses along grain boundaries of the substRate alloy when the specimen is Strained at high temperatures. When the specimen is exposed to the Strain more than 0.4% at over 700 °C, the segregation level of Zn at grain boundaries seems to become critical, leading to occurrence of LME cracks.
Sylvius Hartwig - One of the best experts on this subject based on the ideXlab platform.
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Compressive behaviour of axially loaded spruce wood under large deformations at different Strain Rates
European Journal of Wood and Wood Products, 2011Co-Authors: Martin Neumann, Jürgen Herter, Bernhard O. Droste, Sylvius HartwigAbstract:Stoßdämpfende Bauteile von Transportbehältern für radioaktive Stoffe sind oft als holzgefüllte Stahlkonstruktionen konstruiert. Um die Stoßbeanspruchung der dichten Umschließung zu minimieren, absorbiert das Holz einen Großteil der Aufprallenergie. Fallversuche mit stoßdämpfenden Bauteilen haben gezeigt, dass abhängig von seitlicher Dehnungsbehinderung unterschiedliche Kompressionsmechanismen für axial beanspruchtes Holz ersichtlich waren. Versuche mit Fichtenholzproben ( Picea abies ) wurden durchgeführt, um mit Hilfe statistischer Methoden den Einfluss der DehnRate von statisch bis 30 s^−1 auf (a) Druckfestigkeit, (b) Spannung bei globaler Stauchung von 50 % und (c) Energieabsorption bei einer Stauchung von 50 % zu ermitteln. Folgende Resultate wurden erzielt: Eine höhere DehnRate führte zu signifikant höheren Druckfestigkeiten, Druckspannungen und Energieabsorptionen bei 50 % Stauchung. Die seitliche Dehnungsbehinderung hatte keinen Einfluss auf die Druckfestigkeit, mit seitlicher Dehnungsbehinderung zeigten sich aber signifikant erhöhte Druckspannungen und Energieabsorptionen bei 50 % Stauchung. Daher ist die Definition einer allgemeingültigen Fließkurve für Holz bei großen Deformationen nicht möglich, die Fließkurve muss unter Einbeziehung der seitlichen Dehnungsbehinderung gewählt werden. Impact limiting components of packages for the transport of radioactive materials are often designed as wood filled steel constructions. Wood absorbs major part of the impact energy in order to minimise the impact load acting upon the containment. Dynamic impact experiments with wood filled impact limiters showed different crushing mechanisms for axially loaded wood depending on their lateral conStraint. Tests on spruce wood samples ( Picea abies ) were performed in order to clarify the influence of Strain Rate from static to 30 s^−1 on a) compression strength, b) stress at a global Strain level of 50%, and c) energy absorption capacity at 50% deformation, including statistical evaluation of the results. Results were as follows: Strain Rate Increase led to significantly higher compression strength, stress and Strain energy at a Strain level of 50%. Lateral Strain restriction had no effect on compression strength; it had a significant effect on stress and Strain energy at Strain level of 50%. Therefore, the definition of a general yield curve for wood under large deformations is not possible, the yield curve has to be chosen taking into account lateral conStraints.
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Compressive behaviour of axially loaded spruce wood under large deformations at different Strain Rates
European Journal of Wood and Wood Products, 2010Co-Authors: Martin Neumann, Jürgen Herter, Bernhard O. Droste, Sylvius HartwigAbstract:Impact limiting components of packages for the transport of radioactive materials are often designed as wood filled steel constructions. Wood absorbs major part of the impact energy in order to minimise the impact load acting upon the containment. Dynamic impact experiments with wood filled impact limiters showed different crushing mechanisms for axially loaded wood depending on their lateral conStraint. Tests on spruce wood samples () were performed in order to clarify the influence of Strain Rate from static to 30 s on a) compression strength, b) stress at a global Strain level of 50%, and c) energy absorption capacity at 50% deformation, including statistical evaluation of the results. Results were as follows: Strain Rate Increase led to significantly higher compression strength, stress and Strain energy at a Strain level of 50%. Lateral Strain restriction had no effect on compression strength; it had a significant effect on stress and Strain energy at Strain level of 50%. Therefore, the definition of a general yield curve for wood under large deformations is not possible, the yield curve has to be chosen taking into account lateral conStraints.
Guozheng Kang - One of the best experts on this subject based on the ideXlab platform.
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ratcheting behaviour of high strength rail steels under bi axial compression torsion loadings experiment and simulation
International Journal of Fatigue, 2014Co-Authors: Peter Mutton, Guozheng KangAbstract:Experimental studies were carried out to investigate the ratcheting behaviour of three high strength rail steels of similar nominal hardness but with different chemical compositions subjected to uniaxial and non-proportionally bi-axial compression–torsion cyclic loading conditions. Different axial stress and equivalent shear stress amplitudes and different non-proportional loading paths were considered. Experimental results show that an obvious cyclic softening (i.e., the stress amplitude decreases with the Increase of cyclic number) occurs in all three steels under uniaxial Strain cycling. The ratcheting Strain and ratcheting Strain Rate Increase with the axial stress and the equivalent shear stress amplitudes under bi-axial compression–torsion stress cycling. Moreover, both ratcheting Strain and ratcheting Strain Rate are strongly influenced by the non-proportional loading path. Among the three rail steels, it is found that the low alloy heat-treated rail steel grade has a better resistance to ratcheting than the two hypereutectoid rail steel grades. The hypereutectoid rail steel grade with a higher carbon content gives a lower ratcheting Strain and a lower ratcheting Strain Rate than the hypereutectoid rail steel grade with a lower carbon content under higher loading amplitude. To simulate the ratcheting behaviour of the high strength rail steels, an existing cyclic plasticity model was modified by coupling a non-proportionally multi-axial parameter into isotropic softening and kinematic hardening rules. The method to calibRate the material parameters for the plasticity model and the simulated results validated with experimental data for the three studied rail steels are presented in the paper. This modified plasticity model with the calibRated material data from the experimental study can be applied to investigate the ratcheting behaviour of the three rail steels under wheel–rail cyclic rolling contact in practice.
Youshi Hong - One of the best experts on this subject based on the ideXlab platform.
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effects of loading frequency and loading type on high cycle and very high cycle fatigue of a high strength steel
Materials, 2018Co-Authors: Chengqi Sun, Jijia Xie, Youshi HongAbstract:High-cycle and very-high-cycle fatigue tests via rotary bending (52.5 Hz), electromagnetic resonance (120 Hz) axial cycling, and ultrasonic (20 kHz) axial cycling were performed for a high-strength steel with three heat treatment conditions, and the effects of loading frequency and loading type on fatigue strength and fatigue life were investigated. The results revealed that the loading frequency effect is caused by the combined response of Strain Rate Increase and induced temperature rise. A parameter η was proposed to judge the occurrence of loading frequency effect, and the calculated results were in agreement with the experimental data. In addition, a statistical method based on the control volume was used to reconcile the effect of loading type, and the predicted data were consistent with the experimental results.
Martin Neumann - One of the best experts on this subject based on the ideXlab platform.
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Compressive behaviour of axially loaded spruce wood under large deformations at different Strain Rates
European Journal of Wood and Wood Products, 2011Co-Authors: Martin Neumann, Jürgen Herter, Bernhard O. Droste, Sylvius HartwigAbstract:Stoßdämpfende Bauteile von Transportbehältern für radioaktive Stoffe sind oft als holzgefüllte Stahlkonstruktionen konstruiert. Um die Stoßbeanspruchung der dichten Umschließung zu minimieren, absorbiert das Holz einen Großteil der Aufprallenergie. Fallversuche mit stoßdämpfenden Bauteilen haben gezeigt, dass abhängig von seitlicher Dehnungsbehinderung unterschiedliche Kompressionsmechanismen für axial beanspruchtes Holz ersichtlich waren. Versuche mit Fichtenholzproben ( Picea abies ) wurden durchgeführt, um mit Hilfe statistischer Methoden den Einfluss der DehnRate von statisch bis 30 s^−1 auf (a) Druckfestigkeit, (b) Spannung bei globaler Stauchung von 50 % und (c) Energieabsorption bei einer Stauchung von 50 % zu ermitteln. Folgende Resultate wurden erzielt: Eine höhere DehnRate führte zu signifikant höheren Druckfestigkeiten, Druckspannungen und Energieabsorptionen bei 50 % Stauchung. Die seitliche Dehnungsbehinderung hatte keinen Einfluss auf die Druckfestigkeit, mit seitlicher Dehnungsbehinderung zeigten sich aber signifikant erhöhte Druckspannungen und Energieabsorptionen bei 50 % Stauchung. Daher ist die Definition einer allgemeingültigen Fließkurve für Holz bei großen Deformationen nicht möglich, die Fließkurve muss unter Einbeziehung der seitlichen Dehnungsbehinderung gewählt werden. Impact limiting components of packages for the transport of radioactive materials are often designed as wood filled steel constructions. Wood absorbs major part of the impact energy in order to minimise the impact load acting upon the containment. Dynamic impact experiments with wood filled impact limiters showed different crushing mechanisms for axially loaded wood depending on their lateral conStraint. Tests on spruce wood samples ( Picea abies ) were performed in order to clarify the influence of Strain Rate from static to 30 s^−1 on a) compression strength, b) stress at a global Strain level of 50%, and c) energy absorption capacity at 50% deformation, including statistical evaluation of the results. Results were as follows: Strain Rate Increase led to significantly higher compression strength, stress and Strain energy at a Strain level of 50%. Lateral Strain restriction had no effect on compression strength; it had a significant effect on stress and Strain energy at Strain level of 50%. Therefore, the definition of a general yield curve for wood under large deformations is not possible, the yield curve has to be chosen taking into account lateral conStraints.
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Compressive behaviour of axially loaded spruce wood under large deformations at different Strain Rates
European Journal of Wood and Wood Products, 2010Co-Authors: Martin Neumann, Jürgen Herter, Bernhard O. Droste, Sylvius HartwigAbstract:Impact limiting components of packages for the transport of radioactive materials are often designed as wood filled steel constructions. Wood absorbs major part of the impact energy in order to minimise the impact load acting upon the containment. Dynamic impact experiments with wood filled impact limiters showed different crushing mechanisms for axially loaded wood depending on their lateral conStraint. Tests on spruce wood samples () were performed in order to clarify the influence of Strain Rate from static to 30 s on a) compression strength, b) stress at a global Strain level of 50%, and c) energy absorption capacity at 50% deformation, including statistical evaluation of the results. Results were as follows: Strain Rate Increase led to significantly higher compression strength, stress and Strain energy at a Strain level of 50%. Lateral Strain restriction had no effect on compression strength; it had a significant effect on stress and Strain energy at Strain level of 50%. Therefore, the definition of a general yield curve for wood under large deformations is not possible, the yield curve has to be chosen taking into account lateral conStraints.