This paper focused on the effect of pre-strain on forming limit curves(FLC)of 5754-O aluminum alloy sheet through utilizing biaxial tensile approach.Based on Swift model and Yld2000-2 d yield criterion,the dimensions ...This paper focused on the effect of pre-strain on forming limit curves(FLC)of 5754-O aluminum alloy sheet through utilizing biaxial tensile approach.Based on Swift model and Yld2000-2 d yield criterion,the dimensions of cruciform specimen was optimized through applying finite element method for increasing the strain at specimen center.After that,with the recommended specimen size,the cruciform specimen was tested under various stroke ratios to experimentally characterize the limit strains under different pre-strain levels.Subsequently,the biaxial tensile tests were simulated by Abaqus to obtain the limit strains and validate the material models.It can be observed in both experiments and simulations that the pre-strained uniaxial tension followed by plane tension or equi-biaxial tension can improve the formability of sheet metals.Besides,the strain path change affects the trend of first derivative of strain rate difference between neighboring points with respect to time.An early increase occurred and then fell back to the stable value,the steady evolution continued until to a new increase reaching the critical value.The M–K prediction approach was simulated to verify the influence of pre-strain on FLC.It can be found that the early increase peaks of the major strain incremental ratio rose with the amplitude of pre-strain.Finally,the phenomenon of pseudolocalization caused by the strain path change was explained through evolution of stress state inside the groove.展开更多
Magnesium alloys are frequently subjected to biaxial stress during manufacturing process,however,the work hardening behavior under such circumstance are not well understood.In this study,the deformation mechanisms and...Magnesium alloys are frequently subjected to biaxial stress during manufacturing process,however,the work hardening behavior under such circumstance are not well understood.In this study,the deformation mechanisms and differential work hardening behavior of rolled AZ31 magnesium alloy sheets under biaxial loading are investigated.The change of plastic work contours with increasing plastic strain indicates the differential work hardening behavior of AZ31 magnesium alloy under biaxial stress state,resulting in higher macroscopic work hardening rates of biaxial loading than uniaxial loading,with the elastic-plastic transition part of work hardening extended and stage Ⅲ hardly emerged.Electron backscatter diffraction and Schmid factor analysis confirm the low activation of non-basalslip during biaxial loading tests.While the thickness strain is primarily accommodated by pyramidal<c+a>slip at the initial stage of biaxial deformation,{10–11}contraction twinning is activated at larger plastic strain.The low activation of non-basalslip also retards the dynamic recovery and cross-slip of basal and prismaticslips,leading to the differential work hardening behavior of AZ31 magnesium alloy under biaxial stress state.展开更多
The biaxial tensile behavior of isotropic Ti-6Al-4 V is characterized in this paper.A novel cruciform specimen was designed and optimized to achieve uniform stress and strain distribution within the gauge area.Biaxial...The biaxial tensile behavior of isotropic Ti-6Al-4 V is characterized in this paper.A novel cruciform specimen was designed and optimized to achieve uniform stress and strain distribution within the gauge area.Biaxial tensile tests were conducted at three different loading ratios by the biaxial testing machine.The Digital Image Correlation(DIC)technique was applied to determine strain distribution,and a high-speed camera was employed to record the fracture process.An Inverse Analysis(IA)approach with a combined experimental and numerical method was proposed to determine the true stresses at the gauge section of the specimen during biaxial tensile tests.The results indicate that the initial yield locus can be described by the Cazacu criterion accurately,whereas the Mises criterion can predict better the strengthening behavior of Ti-6Al-4 V in the first quadrant in the principal stress space.展开更多
The biaxial tensile tests were carried out to investigate the deformation behavior and yield loci of dual-phase （DP） steel sheets under biaxial tensile conditions. The true stress-true strain curves of DP steel shee...The biaxial tensile tests were carried out to investigate the deformation behavior and yield loci of dual-phase （DP） steel sheets under biaxial tensile conditions. The true stress-true strain curves of DP steel sheets for different loading ratios were obtained, and the experimental yield loci were determined based on the equivalent plastic work principle. The experimental yield loci were compared to the theoretical yield loci based on Hi1148, Hi1190, Hi1193, Hosford, Barlat89, Yld2000-2d and Gotoh yield criteria. It is found that Yld2000-2d yield criterion can describe the general trends of experimental yield loci of DP steel sheets with comparably higher accuracy. Hosford criterion has the maximum error for DP590, whereas Hi1148 and Barlat89 have the maximum errors for DP780 and DP980.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.51875027)the China Postdoctoral Science Foundation(No.2018M630058)assistances of the program for the financial support。
文摘This paper focused on the effect of pre-strain on forming limit curves(FLC)of 5754-O aluminum alloy sheet through utilizing biaxial tensile approach.Based on Swift model and Yld2000-2 d yield criterion,the dimensions of cruciform specimen was optimized through applying finite element method for increasing the strain at specimen center.After that,with the recommended specimen size,the cruciform specimen was tested under various stroke ratios to experimentally characterize the limit strains under different pre-strain levels.Subsequently,the biaxial tensile tests were simulated by Abaqus to obtain the limit strains and validate the material models.It can be observed in both experiments and simulations that the pre-strained uniaxial tension followed by plane tension or equi-biaxial tension can improve the formability of sheet metals.Besides,the strain path change affects the trend of first derivative of strain rate difference between neighboring points with respect to time.An early increase occurred and then fell back to the stable value,the steady evolution continued until to a new increase reaching the critical value.The M–K prediction approach was simulated to verify the influence of pre-strain on FLC.It can be found that the early increase peaks of the major strain incremental ratio rose with the amplitude of pre-strain.Finally,the phenomenon of pseudolocalization caused by the strain path change was explained through evolution of stress state inside the groove.
基金the financial support from the National Key R&D Program of China(2018YFC0808800)the National Natural Science Foundation of China(Nos.51875398 and 51471116)the Sichuan Science and Technology Program(2019ZDZX0001).
文摘Magnesium alloys are frequently subjected to biaxial stress during manufacturing process,however,the work hardening behavior under such circumstance are not well understood.In this study,the deformation mechanisms and differential work hardening behavior of rolled AZ31 magnesium alloy sheets under biaxial loading are investigated.The change of plastic work contours with increasing plastic strain indicates the differential work hardening behavior of AZ31 magnesium alloy under biaxial stress state,resulting in higher macroscopic work hardening rates of biaxial loading than uniaxial loading,with the elastic-plastic transition part of work hardening extended and stage Ⅲ hardly emerged.Electron backscatter diffraction and Schmid factor analysis confirm the low activation of non-basalslip during biaxial loading tests.While the thickness strain is primarily accommodated by pyramidal<c+a>slip at the initial stage of biaxial deformation,{10–11}contraction twinning is activated at larger plastic strain.The low activation of non-basalslip also retards the dynamic recovery and cross-slip of basal and prismaticslips,leading to the differential work hardening behavior of AZ31 magnesium alloy under biaxial stress state.
基金the financial support from National Natural Science Foundation of China(Nos.11922211,11832015,11527803)the 111 Project,China(No.BP0719007)Science Challenge Project,China(No.TZ2018001).
文摘The biaxial tensile behavior of isotropic Ti-6Al-4 V is characterized in this paper.A novel cruciform specimen was designed and optimized to achieve uniform stress and strain distribution within the gauge area.Biaxial tensile tests were conducted at three different loading ratios by the biaxial testing machine.The Digital Image Correlation(DIC)technique was applied to determine strain distribution,and a high-speed camera was employed to record the fracture process.An Inverse Analysis(IA)approach with a combined experimental and numerical method was proposed to determine the true stresses at the gauge section of the specimen during biaxial tensile tests.The results indicate that the initial yield locus can be described by the Cazacu criterion accurately,whereas the Mises criterion can predict better the strengthening behavior of Ti-6Al-4 V in the first quadrant in the principal stress space.
基金This research was funded by National Natural Science Foundation of China （51275026） and State Key Laboratory of Development and Application Technology of Automotive Steels （Bao Steel Y 12ECEQ07Y）.
文摘The biaxial tensile tests were carried out to investigate the deformation behavior and yield loci of dual-phase （DP） steel sheets under biaxial tensile conditions. The true stress-true strain curves of DP steel sheets for different loading ratios were obtained, and the experimental yield loci were determined based on the equivalent plastic work principle. The experimental yield loci were compared to the theoretical yield loci based on Hi1148, Hi1190, Hi1193, Hosford, Barlat89, Yld2000-2d and Gotoh yield criteria. It is found that Yld2000-2d yield criterion can describe the general trends of experimental yield loci of DP steel sheets with comparably higher accuracy. Hosford criterion has the maximum error for DP590, whereas Hi1148 and Barlat89 have the maximum errors for DP780 and DP980.
