The finite element method based on the equivalent domain integral technique was developed to simulate the push out test and evaluate the interfacial fracture toughness of SiC reinforced titanium matrix composites. A s...The finite element method based on the equivalent domain integral technique was developed to simulate the push out test and evaluate the interfacial fracture toughness of SiC reinforced titanium matrix composites. A special subroutine was introduced while modeling the push-out test to control interfacial failure process. In addition, the residual stresses, Poisson ratio and friction stresses were all considered in the finite element analysis and the interface debonding was described as a continuous process. The results show that the interfacial fracture toughness of SiC/Timetal-834 is about 50 J/m2. Moreover, the effects of various parameters on the interfacial fracture toughness and the variations of energy release rates at both ends of the specimen were analyzed in detail.展开更多
The relationship between shale toughness and its mechanical parameters is of significance for predicting the shale toughness at a great depth based on the geophysical logging data. A large amount of experiments is per...The relationship between shale toughness and its mechanical parameters is of significance for predicting the shale toughness at a great depth based on the geophysical logging data. A large amount of experiments is performed for toughness measurement of the artificial shale specimens of thick-wall cylinder, with internal pressures applied. Moreover, the finite element method is used to interpret the toughness. The acoustic speeds of the specimens are measured and the relationships between shale toughness and the mechanical parameters, which are almost linear, are established.展开更多
The fracture behavior of a series of geometrically similar three point bend specimens is simulated by a nonlinear multi zone boundary element computer program. The material is based on Al 2O 3 SiC (p) ceramic in which...The fracture behavior of a series of geometrically similar three point bend specimens is simulated by a nonlinear multi zone boundary element computer program. The material is based on Al 2O 3 SiC (p) ceramic in which particles are randomly dispersed in a relatively soft matrix. A single edge main crack and a large number of interfacial microcracks randomly distributed between particles and matrix are prescribed. The load deflection curve and the spread of the fracture process zone (FPZ) are observed with confidence. The computer simulated results show that the fracture toughness of the material increases with increasing specimen dimension and becomes constant when the specimen size exceeds a critical value. A practical specimen size for predicting the true fracture toughness of aggregate materials is proposed.展开更多
Effect of rare earth elements (RE) on erosion resistance of nitrocarburized layer of 38CrMoAl steel was investigated. The results indicate that significant improvement occurs in erosion resistance of nitrocarburized 3...Effect of rare earth elements (RE) on erosion resistance of nitrocarburized layer of 38CrMoAl steel was investigated. The results indicate that significant improvement occurs in erosion resistance of nitrocarburized 38CrMoAl steel by introducing RE during nitrocarburizing processing as compared with conventional nitrocarburizing processing. Results of mechanical testing show that both hardness and impact toughness of RE-nitrocarburizing layer of 38CrMoAl steel increase as compared with the conventional one. Optical microscopy reveals that there is improvement in the nitrocarburized layer attributed to the introduction of RE, which results in improvement in erosion resistance. Surface morphology observation of tested samples reveals that predominantly furrow-like peelings from plastic deformation are observed for RE nitrocarburizied 38CrMoAl steel, while the furrow-like peeling with initial cross crack and large grinding peelings were observed for conventionally nitrocarburized samples.展开更多
Mode-I fracture behavior of glass-carbon fiber reinforced hybrid polymer composite was investigated based on experimental and finite element analysis. The compact tension (CT) specimen was employed to conduct mode-I f...Mode-I fracture behavior of glass-carbon fiber reinforced hybrid polymer composite was investigated based on experimental and finite element analysis. The compact tension (CT) specimen was employed to conduct mode-I fracture test using special loading fixtures as per ASTM standards. Fracture toughness was determined experimentally for along and across the fiber orientation of the specimen. Results indicated that the cracked specimens are tougher along the fiber orientations as compared with across the fiber orientations. A similar fracture test was simulated using finite element analysis software ANSYS. Critical stress intensity factor (K) was calculated at fracture/failure using displacement extrapolation method, for both along and across the fiber orientations. The fractured surfaces of the glasscarbon epoxy composite under mode-I loading condition was examined by electron microscope.展开更多
The Small-Scale Steady State (S4) test has been recently developed in order to assess the fracture behaviour of polyethylene (PE) gas distribution pipe material during rapid axial crack propagation. Based on an invest...The Small-Scale Steady State (S4) test has been recently developed in order to assess the fracture behaviour of polyethylene (PE) gas distribution pipe material during rapid axial crack propagation. Based on an investigation of the S4 test, a simulation model of S4 test has been developed. This paper describes the use of the results obtained from the S4 test and program modified from PFRAC (Pipeline Fracture Analysis Code) to evaluate the fracture toughness of the material, G(d), which could not be directly obtained from the test, and to predict critical pressure, p(c), for rapid crack propagation (RCP) in a full scale PE pipe. The algorithms for contact conditions are developed to consider the opening pipe wall impact against a series containment rings and the capabilities of PFRAC are also extended. When G(d) is evaluated, investigations are made on the effect of temperature, wall thickness and crack velocity. In addition, procedures to evaluate the critical pressure for the S4 test pipe are also discussed.展开更多
基金Project(50371069) supported by the National Natural Science Foundation of ChinaProject(04G53044) supported by the Defense Fundamental Research Program of ChinaProject supported by the Doctoral Innovation Foundation of Northwestern Polytechnical University, China
文摘The finite element method based on the equivalent domain integral technique was developed to simulate the push out test and evaluate the interfacial fracture toughness of SiC reinforced titanium matrix composites. A special subroutine was introduced while modeling the push-out test to control interfacial failure process. In addition, the residual stresses, Poisson ratio and friction stresses were all considered in the finite element analysis and the interface debonding was described as a continuous process. The results show that the interfacial fracture toughness of SiC/Timetal-834 is about 50 J/m2. Moreover, the effects of various parameters on the interfacial fracture toughness and the variations of energy release rates at both ends of the specimen were analyzed in detail.
基金Supported by the National Natural Science Foundation of China (No. 50274054)
文摘The relationship between shale toughness and its mechanical parameters is of significance for predicting the shale toughness at a great depth based on the geophysical logging data. A large amount of experiments is performed for toughness measurement of the artificial shale specimens of thick-wall cylinder, with internal pressures applied. Moreover, the finite element method is used to interpret the toughness. The acoustic speeds of the specimens are measured and the relationships between shale toughness and the mechanical parameters, which are almost linear, are established.
文摘The fracture behavior of a series of geometrically similar three point bend specimens is simulated by a nonlinear multi zone boundary element computer program. The material is based on Al 2O 3 SiC (p) ceramic in which particles are randomly dispersed in a relatively soft matrix. A single edge main crack and a large number of interfacial microcracks randomly distributed between particles and matrix are prescribed. The load deflection curve and the spread of the fracture process zone (FPZ) are observed with confidence. The computer simulated results show that the fracture toughness of the material increases with increasing specimen dimension and becomes constant when the specimen size exceeds a critical value. A practical specimen size for predicting the true fracture toughness of aggregate materials is proposed.
文摘Effect of rare earth elements (RE) on erosion resistance of nitrocarburized layer of 38CrMoAl steel was investigated. The results indicate that significant improvement occurs in erosion resistance of nitrocarburized 38CrMoAl steel by introducing RE during nitrocarburizing processing as compared with conventional nitrocarburizing processing. Results of mechanical testing show that both hardness and impact toughness of RE-nitrocarburizing layer of 38CrMoAl steel increase as compared with the conventional one. Optical microscopy reveals that there is improvement in the nitrocarburized layer attributed to the introduction of RE, which results in improvement in erosion resistance. Surface morphology observation of tested samples reveals that predominantly furrow-like peelings from plastic deformation are observed for RE nitrocarburizied 38CrMoAl steel, while the furrow-like peeling with initial cross crack and large grinding peelings were observed for conventionally nitrocarburized samples.
文摘Mode-I fracture behavior of glass-carbon fiber reinforced hybrid polymer composite was investigated based on experimental and finite element analysis. The compact tension (CT) specimen was employed to conduct mode-I fracture test using special loading fixtures as per ASTM standards. Fracture toughness was determined experimentally for along and across the fiber orientation of the specimen. Results indicated that the cracked specimens are tougher along the fiber orientations as compared with across the fiber orientations. A similar fracture test was simulated using finite element analysis software ANSYS. Critical stress intensity factor (K) was calculated at fracture/failure using displacement extrapolation method, for both along and across the fiber orientations. The fractured surfaces of the glasscarbon epoxy composite under mode-I loading condition was examined by electron microscope.
文摘The Small-Scale Steady State (S4) test has been recently developed in order to assess the fracture behaviour of polyethylene (PE) gas distribution pipe material during rapid axial crack propagation. Based on an investigation of the S4 test, a simulation model of S4 test has been developed. This paper describes the use of the results obtained from the S4 test and program modified from PFRAC (Pipeline Fracture Analysis Code) to evaluate the fracture toughness of the material, G(d), which could not be directly obtained from the test, and to predict critical pressure, p(c), for rapid crack propagation (RCP) in a full scale PE pipe. The algorithms for contact conditions are developed to consider the opening pipe wall impact against a series containment rings and the capabilities of PFRAC are also extended. When G(d) is evaluated, investigations are made on the effect of temperature, wall thickness and crack velocity. In addition, procedures to evaluate the critical pressure for the S4 test pipe are also discussed.
