A statistical model of dynamic spall damage due to void nucleation and growth is proposed for ductile materials under intense loading, which takes into account inertia, the elastic-plastic effect, and initial void siz...A statistical model of dynamic spall damage due to void nucleation and growth is proposed for ductile materials under intense loading, which takes into account inertia, the elastic-plastic effect, and initial void size. To some extent, void interaction could be accounted for in this approach. Based on this model, the simulation of spall experiments for copper is performed by using the Lagrangian finite element method. The simulation results are in good agreement with experimental data for the free surface velocity profile, stress record behind copper target, final porosity, and void concentrations across the target. The influence of elastic-plastic effect upon the damage evolution is explored. The correlation between the damage evolution and the history of the stress near the spall plane is also analyzed.展开更多
The growth and coalescence of two microholes in copper foil were studied experimental ly by in situ tensile tests under a,scanning electronic microscope.Two microholes of 15-35μm in di- ameter were arranged in differ...The growth and coalescence of two microholes in copper foil were studied experimental ly by in situ tensile tests under a,scanning electronic microscope.Two microholes of 15-35μm in di- ameter were arranged in different distances and orientations.It was found that the mechanisms of mi crohole evolution were represented by slipping band creation,and then crack initiation and propagation along the slipping bands,in ligament.The process of microhole growth and coalescence was influenced by the inter-center distance and orientation of microholes.The critical surface of microholes at coales- cence is about 2—2.5 times that of the initial one.The variation of both the inter center distance and orientation depends on the initial angle.展开更多
The dilatational plastic constitutive equation presented in this paper is proved to be in aform of generality. Based on this equation, the constitutive behaviour of materials at themoment of bifurcation is demonstrate...The dilatational plastic constitutive equation presented in this paper is proved to be in aform of generality. Based on this equation, the constitutive behaviour of materials at themoment of bifurcation is demonstrated to follow a loading path with the response as "soft"as possible.展开更多
This paper is concerned with evaluation of various ductile fracture criteria in a general three-dimensional stress state of stress triaxiality, the Lode parameter and the equiva- lent plastic strain to fracture. Evalu...This paper is concerned with evaluation of various ductile fracture criteria in a general three-dimensional stress state of stress triaxiality, the Lode parameter and the equiva- lent plastic strain to fracture. Evaluation is carried out by comparing fracture loci constructed by fracture criteria to experimental results of A12024-T351. Comparison demonstrates that the Modified Mohr-Coulomb criterion and a newly proposed criterion provide sufficient predictabil- ity of fracture strain. Moreover, evaluation is emphasized on the predicted cut-off value for stress triaxiality. The evaluation demonstrates that the Cockcroft-Latham, Brozzo, Oh, Ko-Huh and the new criteria coupled a reasonable cut-off value for ductile materials.展开更多
A new method is presented to determine the full-range, uniaxial constitutive relationship of materials by tensile tests on funnel specimens with small curvature radius and finite element analysis(FEA). An iteration me...A new method is presented to determine the full-range, uniaxial constitutive relationship of materials by tensile tests on funnel specimens with small curvature radius and finite element analysis(FEA). An iteration method using FEA APDL(ANSYS parametric design language) programming has been developed to approach the necking constitutive relationship of materials. Test results from SAE 304 stainless steel at room temperature show that simulated load vs displacement curve,diameter at funnel root vs displacement curve, and funnel deformation contours are close to modeled results. Due to this new method, full-range constitutive relationships and true stress and effective true strain at failure are found for 316 L stainless steel, TA17 titanium alloy and A508-III stainless steel at room temperature, and 316 L stainless steel at various elevated temperatures.展开更多
基金Project supported by the Science and Technology Development Foundation of China Academy of Engineering Physics (Grant Nos. 2009A09027, 2009A09006, and 2011B0101028)
文摘A statistical model of dynamic spall damage due to void nucleation and growth is proposed for ductile materials under intense loading, which takes into account inertia, the elastic-plastic effect, and initial void size. To some extent, void interaction could be accounted for in this approach. Based on this model, the simulation of spall experiments for copper is performed by using the Lagrangian finite element method. The simulation results are in good agreement with experimental data for the free surface velocity profile, stress record behind copper target, final porosity, and void concentrations across the target. The influence of elastic-plastic effect upon the damage evolution is explored. The correlation between the damage evolution and the history of the stress near the spall plane is also analyzed.
文摘The growth and coalescence of two microholes in copper foil were studied experimental ly by in situ tensile tests under a,scanning electronic microscope.Two microholes of 15-35μm in di- ameter were arranged in different distances and orientations.It was found that the mechanisms of mi crohole evolution were represented by slipping band creation,and then crack initiation and propagation along the slipping bands,in ligament.The process of microhole growth and coalescence was influenced by the inter-center distance and orientation of microholes.The critical surface of microholes at coales- cence is about 2—2.5 times that of the initial one.The variation of both the inter center distance and orientation depends on the initial angle.
文摘The dilatational plastic constitutive equation presented in this paper is proved to be in aform of generality. Based on this equation, the constitutive behaviour of materials at themoment of bifurcation is demonstrated to follow a loading path with the response as "soft"as possible.
文摘This paper is concerned with evaluation of various ductile fracture criteria in a general three-dimensional stress state of stress triaxiality, the Lode parameter and the equiva- lent plastic strain to fracture. Evaluation is carried out by comparing fracture loci constructed by fracture criteria to experimental results of A12024-T351. Comparison demonstrates that the Modified Mohr-Coulomb criterion and a newly proposed criterion provide sufficient predictabil- ity of fracture strain. Moreover, evaluation is emphasized on the predicted cut-off value for stress triaxiality. The evaluation demonstrates that the Cockcroft-Latham, Brozzo, Oh, Ko-Huh and the new criteria coupled a reasonable cut-off value for ductile materials.
基金co-supported by the National Natural Science Foundation of China (No. 11472228)the Sichuan Youth Science and Technology Innovation Team Projects (No. 2013TD0004)
文摘A new method is presented to determine the full-range, uniaxial constitutive relationship of materials by tensile tests on funnel specimens with small curvature radius and finite element analysis(FEA). An iteration method using FEA APDL(ANSYS parametric design language) programming has been developed to approach the necking constitutive relationship of materials. Test results from SAE 304 stainless steel at room temperature show that simulated load vs displacement curve,diameter at funnel root vs displacement curve, and funnel deformation contours are close to modeled results. Due to this new method, full-range constitutive relationships and true stress and effective true strain at failure are found for 316 L stainless steel, TA17 titanium alloy and A508-III stainless steel at room temperature, and 316 L stainless steel at various elevated temperatures.
