In this paper,a class of new immersed interface finite element methods (IIFEM) is developed to solve elasticity interface problems with homogeneous and non-homogeneous jump conditions in two dimensions.Simple non-body...In this paper,a class of new immersed interface finite element methods (IIFEM) is developed to solve elasticity interface problems with homogeneous and non-homogeneous jump conditions in two dimensions.Simple non-body-fitted meshes are used.For homogeneous jump conditions,both non-conforming and conforming basis functions are constructed in such a way that they satisfy the natural jump conditions. For non-homogeneous jump conditions,a pair of functions that satisfy the same non-homogeneous jump conditions are constructed using a level-set representation of the interface.With such a pair of functions,the discontinuities across the interface in the solution and flux are removed;and an equivalent elasticity interface problem with homogeneous jump conditions is formulated.Numerical examples are presented to demonstrate that such methods have second order convergence.展开更多
A new test method was proposed to evaluate the cohesive strength of composite laminates. Cohesive strength and the critical strain energy for Mode-II interlamiar fracture of E-glass/epoxy woven fabrication were determ...A new test method was proposed to evaluate the cohesive strength of composite laminates. Cohesive strength and the critical strain energy for Mode-II interlamiar fracture of E-glass/epoxy woven fabrication were determined from the single lap joint(SLJ) and end notch flexure(ENF) test, respectively. In order to verify their adequacy, a cohesive zone model simulation based on interface finite elements was performed. A closed form solution for determination of the penalty stiffness parameter was proposed. Modified form of Park-Paulino-Roesler traction-separation law was provided and conducted altogether with trapezoidal and bilinear mixed-mode damage models to simulate damage using Abaqus cohesive elements. It was observed that accurate damage prediction and numerical convergence were obtained using the proposed penalty stiffness. Comparison between three damage models reveals that good simulation of fracture process zone and delamination prediction were obtained using the modified PPR model as damage model. Cohesive zone length as a material property was determined. To ensure the sufficient dissipation of energy, it was recommended that at least 4 elements should span cohesive zone length.展开更多
The mechanical behaviors of the interface between coarse-grained soil and concrete were investigated by simple shear tests under condition of mixed soil slurry (bentonite mixed with cement grout).For comparison,the in...The mechanical behaviors of the interface between coarse-grained soil and concrete were investigated by simple shear tests under condition of mixed soil slurry (bentonite mixed with cement grout).For comparison,the interfaces both without slurry and with bentonite slurry were analyzed.The experimental results show that different slurries exert much influence on the strength and deformation of soil/structure interface.Under mixed soil slurry,strain softening and shear dilatation are observed,while shear dilatation appears under the small normal stress of the interface without slurry,and shear contraction is significant under the condition of the bentonite slurry.The thickness of the interface was determined by analyzing the disturbed height of the sample with both simple shear test and particle flow code (PFC).An elasto-plastic constitutive model incorporating strain softening and dilatancy for thin layer element of interface was formulated in the framework of generalized potential theory.The relation curves of shear stress and shear strain,as well as the relation curves of normal strain and shear strain,were fitted by a piecewise function composed by hyperbolic functions and resembling normal functions.The entire model parameters can be identified by tests.The new model is verified by comparing the measured data of indoor cut-off wall model tests with the predictions from finite element method (FEM).The FEM results indicate that the stress of wall calculated by using Goodman element is too large,and the maximum deviation between the test data and prediction is about 45%.While the prediction from the proposed model is close to the measured data,and the error is generally less than 10%.展开更多
Because zirconium alloy cladding is the first containment barrier for fission products, its mechanical integrity is the most important concern. In view of the mechanical integrity, stress and strain are the main facto...Because zirconium alloy cladding is the first containment barrier for fission products, its mechanical integrity is the most important concern. In view of the mechanical integrity, stress and strain are the main factors that affect the cladding performance during normal or off-normal operation, which induces force interaction between the pellet and cladding. In the case of a normal operation period, to estimate the cladding stress and strain, various models and codes have been developed using a simplified 1D （one-dimensional） assumption. However, in the case of a slow ramp during start-up and shut-down and a fast transient such as an AOO （anticipated operational occurrence）, it is difficult for a 1D model to simulate the cladding stress and strain accurately due to its modeling limitation. To model a large deformation along the radial and axial directions such as a ＂＇ballooning＂ phenomenon, FE （finite element） modeling, which can simulate a higher degree of freedom, is an indispensable requirement. In this work, an axisymmetric two-dimensional FE module, which will be integrated into the transient fuel performance code, has been developed. To solve the mechanical equilibrium of the pellet-cladding system, taking into account the geometrical and material non-linearities, the FE module employs an ESF （effective-stress-function） algorithm. Verifications of the FE module for the cases of thermal and elastic analyes were performed using the results of ANSYS 13.0.展开更多
This paper presents the characteristics of the crack growth at the interface of rubber-rubber and rubber-steel bimaterials undertensile deformation using the non-linear finite element method. By using the commercial f...This paper presents the characteristics of the crack growth at the interface of rubber-rubber and rubber-steel bimaterials undertensile deformation using the non-linear finite element method. By using the commercial finite element software ABAQUS,the J integral calculations are carried out for the initial interface crack in the interfaces in-between two Neo-Hookean materials,two Mooney-Rivlin materials, Neo-Hookean and Mooney-Rivlin rubbers, Neo-Hookean and Polynomial, Mooney-Rivlin andPolynomial, and the Mooney-Rivlin and steel bi-materials. The computational results of the maximum J integral directionaround the crack tip illustrate the possible direction of crack growth initiation. Furthermore, it is found that the crack bends tothe softer rubber material at a certain angle with the initial crack direction if the crack depth is relatively small. For the crackwith a larger depth, the crack propagates to grow along the interface in-between the bimaterials.展开更多
基金supported by the US ARO grants 49308-MA and 56349-MAthe US AFSOR grant FA9550-06-1-024+1 种基金he US NSF grant DMS-0911434the State Key Laboratory of Scientific and Engineering Computing of Chinese Academy of Sciences during a visit by Z.Li between July-August,2008.
文摘In this paper,a class of new immersed interface finite element methods (IIFEM) is developed to solve elasticity interface problems with homogeneous and non-homogeneous jump conditions in two dimensions.Simple non-body-fitted meshes are used.For homogeneous jump conditions,both non-conforming and conforming basis functions are constructed in such a way that they satisfy the natural jump conditions. For non-homogeneous jump conditions,a pair of functions that satisfy the same non-homogeneous jump conditions are constructed using a level-set representation of the interface.With such a pair of functions,the discontinuities across the interface in the solution and flux are removed;and an equivalent elasticity interface problem with homogeneous jump conditions is formulated.Numerical examples are presented to demonstrate that such methods have second order convergence.
文摘A new test method was proposed to evaluate the cohesive strength of composite laminates. Cohesive strength and the critical strain energy for Mode-II interlamiar fracture of E-glass/epoxy woven fabrication were determined from the single lap joint(SLJ) and end notch flexure(ENF) test, respectively. In order to verify their adequacy, a cohesive zone model simulation based on interface finite elements was performed. A closed form solution for determination of the penalty stiffness parameter was proposed. Modified form of Park-Paulino-Roesler traction-separation law was provided and conducted altogether with trapezoidal and bilinear mixed-mode damage models to simulate damage using Abaqus cohesive elements. It was observed that accurate damage prediction and numerical convergence were obtained using the proposed penalty stiffness. Comparison between three damage models reveals that good simulation of fracture process zone and delamination prediction were obtained using the modified PPR model as damage model. Cohesive zone length as a material property was determined. To ensure the sufficient dissipation of energy, it was recommended that at least 4 elements should span cohesive zone length.
基金Project(20110094110002) supported by the Specialized Research Fund for the Doctoral Program of Higher Education of ChinaProject(200801014) supported by the Ministry of Water Resources of ChinaProject(50825901) supported by the National Natural Science Foundation of China
文摘The mechanical behaviors of the interface between coarse-grained soil and concrete were investigated by simple shear tests under condition of mixed soil slurry (bentonite mixed with cement grout).For comparison,the interfaces both without slurry and with bentonite slurry were analyzed.The experimental results show that different slurries exert much influence on the strength and deformation of soil/structure interface.Under mixed soil slurry,strain softening and shear dilatation are observed,while shear dilatation appears under the small normal stress of the interface without slurry,and shear contraction is significant under the condition of the bentonite slurry.The thickness of the interface was determined by analyzing the disturbed height of the sample with both simple shear test and particle flow code (PFC).An elasto-plastic constitutive model incorporating strain softening and dilatancy for thin layer element of interface was formulated in the framework of generalized potential theory.The relation curves of shear stress and shear strain,as well as the relation curves of normal strain and shear strain,were fitted by a piecewise function composed by hyperbolic functions and resembling normal functions.The entire model parameters can be identified by tests.The new model is verified by comparing the measured data of indoor cut-off wall model tests with the predictions from finite element method (FEM).The FEM results indicate that the stress of wall calculated by using Goodman element is too large,and the maximum deviation between the test data and prediction is about 45%.While the prediction from the proposed model is close to the measured data,and the error is generally less than 10%.
文摘Because zirconium alloy cladding is the first containment barrier for fission products, its mechanical integrity is the most important concern. In view of the mechanical integrity, stress and strain are the main factors that affect the cladding performance during normal or off-normal operation, which induces force interaction between the pellet and cladding. In the case of a normal operation period, to estimate the cladding stress and strain, various models and codes have been developed using a simplified 1D （one-dimensional） assumption. However, in the case of a slow ramp during start-up and shut-down and a fast transient such as an AOO （anticipated operational occurrence）, it is difficult for a 1D model to simulate the cladding stress and strain accurately due to its modeling limitation. To model a large deformation along the radial and axial directions such as a ＂＇ballooning＂ phenomenon, FE （finite element） modeling, which can simulate a higher degree of freedom, is an indispensable requirement. In this work, an axisymmetric two-dimensional FE module, which will be integrated into the transient fuel performance code, has been developed. To solve the mechanical equilibrium of the pellet-cladding system, taking into account the geometrical and material non-linearities, the FE module employs an ESF （effective-stress-function） algorithm. Verifications of the FE module for the cases of thermal and elastic analyes were performed using the results of ANSYS 13.0.
基金supported by the Hong Kong Polytechnic University (Grant No. G-YH32)
文摘This paper presents the characteristics of the crack growth at the interface of rubber-rubber and rubber-steel bimaterials undertensile deformation using the non-linear finite element method. By using the commercial finite element software ABAQUS,the J integral calculations are carried out for the initial interface crack in the interfaces in-between two Neo-Hookean materials,two Mooney-Rivlin materials, Neo-Hookean and Mooney-Rivlin rubbers, Neo-Hookean and Polynomial, Mooney-Rivlin andPolynomial, and the Mooney-Rivlin and steel bi-materials. The computational results of the maximum J integral directionaround the crack tip illustrate the possible direction of crack growth initiation. Furthermore, it is found that the crack bends tothe softer rubber material at a certain angle with the initial crack direction if the crack depth is relatively small. For the crackwith a larger depth, the crack propagates to grow along the interface in-between the bimaterials.
