An elasto-visco-plastic constitutive model incorporating the craze damage behavior was developed for the polypropylene(PP), by using the plastic failure model applied for the concrete, to capture the craze yielding an...An elasto-visco-plastic constitutive model incorporating the craze damage behavior was developed for the polypropylene(PP), by using the plastic failure model applied for the concrete, to capture the craze yielding and stress-whitening phenomena. In addition, the developed constitutive model was implemented into finite element codes in Abaqus to simulate the tensile deformation. The standard uniaxial tensile tests were carried out. The stress-strain curves from the uniaxial tensile tests show that the stress keeps decreasing after yielding and the yield stress rises with the increasing of the strain rate. It is worth noting that the craze damage is more visible with higher strain rate. The stress-whitening can be seen clearly around the fracture. The uniaxial tensile tests using specially designed specimen with circular holes weakening were performed for the validation of the developed model. The simulation results of the tensile deformation of the hole-weakened specimen suggest that the stress-whitening could be attributed to the equivalent visco-plastic strain. By comparing between the simulation analysis and the experimental results, the proposed model can describe the stress whitening phenomenon with good accuracy.展开更多
Application research of neural networks to geotechnical engineering has become a hotspot nowadays.General model may not reach the predicting precision in practical application due to different characteristics in diffe...Application research of neural networks to geotechnical engineering has become a hotspot nowadays.General model may not reach the predicting precision in practical application due to different characteristics in different fields.In allusion to this,an elasto-plastic constitutive model based on clustering radial basis function neural network(BC-RBFNN) was proposed for moderate sandy clay according to its properties.Firstly,knowledge base was established on triaxial compression testing data;then the model was trained,learned and emulated using knowledge base;finally,predicting results of the BC-RBFNN model were compared and analyzed with those of other intelligent model.The results show that the BC-RBFNN model can alter the training and learning velocity and improve the predicting precision,which provides possibility for engineering practice on demanding high precision.展开更多
基于次加载面的砂黏统一本构模型(clay and sand model with subloading surface,简称CASM-S)适用于描述砂土和超固结黏土的力学行为,然而该模型仍沿用线性临界状态描述砂土的应力−孔隙比关系。考虑高应力状态下砂土的压缩特性及其临界...基于次加载面的砂黏统一本构模型(clay and sand model with subloading surface,简称CASM-S)适用于描述砂土和超固结黏土的力学行为,然而该模型仍沿用线性临界状态描述砂土的应力−孔隙比关系。考虑高应力状态下砂土的压缩特性及其临界状态线在e-lnp平面内的非线性,在CASM-S中引入了描述砂土非线性临界状态线和参考固结线(reference compression curve,简称RCC)的幂函数形式;通过引入参数ξ和λ_(r),修正了CASM-S的屈服面与次加载面函数以描述砂土剪切特性,并利用参考固结线在e-(p/p_(a))^(ξ)(其中e为临界状态下的孔隙比,p为正应力,pa为标准大气压)平面内的线性关系给出了先期固结压力p_(c)0的求解方法。新建本构模型的11个参数均可通过常规土工试验或经验方法确定。基于修正CASM-S的预测结果,对比分析了4种砂土的三轴排水和不排水剪切试验结果,证实了该模型能够有效考虑非线性临界状态线的影响,并能够精确描述饱和砂土在不同孔隙比和围压下的三轴剪切特性。展开更多
基金Project(51275185)supported by the National Natural Science Foundation of China
文摘An elasto-visco-plastic constitutive model incorporating the craze damage behavior was developed for the polypropylene(PP), by using the plastic failure model applied for the concrete, to capture the craze yielding and stress-whitening phenomena. In addition, the developed constitutive model was implemented into finite element codes in Abaqus to simulate the tensile deformation. The standard uniaxial tensile tests were carried out. The stress-strain curves from the uniaxial tensile tests show that the stress keeps decreasing after yielding and the yield stress rises with the increasing of the strain rate. It is worth noting that the craze damage is more visible with higher strain rate. The stress-whitening can be seen clearly around the fracture. The uniaxial tensile tests using specially designed specimen with circular holes weakening were performed for the validation of the developed model. The simulation results of the tensile deformation of the hole-weakened specimen suggest that the stress-whitening could be attributed to the equivalent visco-plastic strain. By comparing between the simulation analysis and the experimental results, the proposed model can describe the stress whitening phenomenon with good accuracy.
基金Project(07031B) supported by the Scientific Research Fund of Central South University of Forestry and TechnologyProject(06C843) supported by the Scientific Research Fund of Hunan Provincial Education Department
文摘Application research of neural networks to geotechnical engineering has become a hotspot nowadays.General model may not reach the predicting precision in practical application due to different characteristics in different fields.In allusion to this,an elasto-plastic constitutive model based on clustering radial basis function neural network(BC-RBFNN) was proposed for moderate sandy clay according to its properties.Firstly,knowledge base was established on triaxial compression testing data;then the model was trained,learned and emulated using knowledge base;finally,predicting results of the BC-RBFNN model were compared and analyzed with those of other intelligent model.The results show that the BC-RBFNN model can alter the training and learning velocity and improve the predicting precision,which provides possibility for engineering practice on demanding high precision.
文摘基于次加载面的砂黏统一本构模型(clay and sand model with subloading surface,简称CASM-S)适用于描述砂土和超固结黏土的力学行为,然而该模型仍沿用线性临界状态描述砂土的应力−孔隙比关系。考虑高应力状态下砂土的压缩特性及其临界状态线在e-lnp平面内的非线性,在CASM-S中引入了描述砂土非线性临界状态线和参考固结线(reference compression curve,简称RCC)的幂函数形式;通过引入参数ξ和λ_(r),修正了CASM-S的屈服面与次加载面函数以描述砂土剪切特性,并利用参考固结线在e-(p/p_(a))^(ξ)(其中e为临界状态下的孔隙比,p为正应力,pa为标准大气压)平面内的线性关系给出了先期固结压力p_(c)0的求解方法。新建本构模型的11个参数均可通过常规土工试验或经验方法确定。基于修正CASM-S的预测结果,对比分析了4种砂土的三轴排水和不排水剪切试验结果,证实了该模型能够有效考虑非线性临界状态线的影响,并能够精确描述饱和砂土在不同孔隙比和围压下的三轴剪切特性。
