Various microstructure-level finite element models were generated according to the real microstructure of DP590 steel to capture the mechanical behavior and fracture mode.The failure mode of the dual-phase(DP)steels,m...Various microstructure-level finite element models were generated according to the real microstructure of DP590 steel to capture the mechanical behavior and fracture mode.The failure mode of the dual-phase(DP)steels,mainly resulting from microstructure-level inhomogeneity and initial geometrical imperfection,was predicted using the plastic strain localization theory.In addition,dog-bone-type tensile test specimens with different edge qualities were prepared and the deformation processes were recorded using a digital image correlation system.When the steel exhibited no initial geometrical imperfection,void initiation was triggered by decohesion between martensite and ferrite which was predicted based on the severe strain concentration,or tensile stress in areas where stress triaxiality and strain values were high.Final failure was caused by shear localization in the vicinity.Moreover,the initial geometrical imperfections severely affected the overall ductility and failure mode of the DP590steel.When initial geometrical imperfections were deeply ingrained,an incipient crack began at the site of initial geometrical imperfection,and then caused progressive damage throughout the microstructure,from the area of shear localization to the final fracture.Overall,the depth of the geometrical imperfection was the critical factor in determining whether internal decohesion or a local crack plays a dominant role.展开更多
We describe an implementation of the cluster-in-molecule （CIM） resolution of the identity （RI） approximation second-order Moller-Plesset perturbation theory （CIM-RI-MP2）, with the purpose of extending RI-MP2 cal...We describe an implementation of the cluster-in-molecule （CIM） resolution of the identity （RI） approximation second-order Moller-Plesset perturbation theory （CIM-RI-MP2）, with the purpose of extending RI-MP2 calculations to very large systems. For typical conformers of several large polypeptides, we calculated their conformational energy differences with the CIM-RI-MP2 and the generalized energy-based fragmentation MP2 （GEBF-MP2） methods, and compared these results with the density functional theory （DFT） results obtained with several popular functionals. Our calculations show that the conformational energy differences obtained with CIM-RI-MP2 and GEBF-MP2 are very close to each other. In comparison with the GEBF-MP2 and CIM-RI-MP2 relative energies, we found that the DFT functionals （CAM-B3LYP-D3, LC-ωPBE-D3, M05-2X, M06-2X and coB97XD） can give quite accurate conformational energy differences for structurally similar conformers, but provide less-accurate results for structurally very different conformers.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.51105250)
文摘Various microstructure-level finite element models were generated according to the real microstructure of DP590 steel to capture the mechanical behavior and fracture mode.The failure mode of the dual-phase(DP)steels,mainly resulting from microstructure-level inhomogeneity and initial geometrical imperfection,was predicted using the plastic strain localization theory.In addition,dog-bone-type tensile test specimens with different edge qualities were prepared and the deformation processes were recorded using a digital image correlation system.When the steel exhibited no initial geometrical imperfection,void initiation was triggered by decohesion between martensite and ferrite which was predicted based on the severe strain concentration,or tensile stress in areas where stress triaxiality and strain values were high.Final failure was caused by shear localization in the vicinity.Moreover,the initial geometrical imperfections severely affected the overall ductility and failure mode of the DP590steel.When initial geometrical imperfections were deeply ingrained,an incipient crack began at the site of initial geometrical imperfection,and then caused progressive damage throughout the microstructure,from the area of shear localization to the final fracture.Overall,the depth of the geometrical imperfection was the critical factor in determining whether internal decohesion or a local crack plays a dominant role.
基金supported by the National Natural Science Foundation of China(21073086,21333004)the National Basic Research Program of China(2011CB808501)
文摘We describe an implementation of the cluster-in-molecule （CIM） resolution of the identity （RI） approximation second-order Moller-Plesset perturbation theory （CIM-RI-MP2）, with the purpose of extending RI-MP2 calculations to very large systems. For typical conformers of several large polypeptides, we calculated their conformational energy differences with the CIM-RI-MP2 and the generalized energy-based fragmentation MP2 （GEBF-MP2） methods, and compared these results with the density functional theory （DFT） results obtained with several popular functionals. Our calculations show that the conformational energy differences obtained with CIM-RI-MP2 and GEBF-MP2 are very close to each other. In comparison with the GEBF-MP2 and CIM-RI-MP2 relative energies, we found that the DFT functionals （CAM-B3LYP-D3, LC-ωPBE-D3, M05-2X, M06-2X and coB97XD） can give quite accurate conformational energy differences for structurally similar conformers, but provide less-accurate results for structurally very different conformers.
