为研究冻胀荷载对双裂隙岩体裂纹扩展及贯通机制的影响,文章基于扩展有限元法(extended finite element method,XFEM),分析冻胀力作用下不同岩桥参数双裂隙试样的裂纹扩展特征和破坏形式,探究在冻胀力和侧向卸荷共同作用下双裂隙试样的...为研究冻胀荷载对双裂隙岩体裂纹扩展及贯通机制的影响,文章基于扩展有限元法(extended finite element method,XFEM),分析冻胀力作用下不同岩桥参数双裂隙试样的裂纹扩展特征和破坏形式,探究在冻胀力和侧向卸荷共同作用下双裂隙试样的裂纹扩展贯通规律。结果表明:基于XFEM的数值模拟结果与试验中的裂纹扩展路径基本吻合,验证了XFEM能够有效地应用于双裂隙岩体的裂纹扩展模拟;非岩桥区冻胀裂纹的扩展方向与预制裂隙走向相同,而岩桥区裂纹的扩展方向受到冻胀应力的影响,裂纹扩展方向偏向于另一条预制裂隙位置;冻胀裂纹的扩展模式受到围压的影响,随着围压增加,侧向卸荷过程中裂纹扩展模式由拉张模式变成拉剪混合模式,裂纹扩展方向也发生偏转。研究方法和结果可为低温裂隙岩体裂纹扩展相关研究提供参考。展开更多
A unit cell including the matrix, precipitation free zone(PFZ) and grain boundary was prepared, and the crystal plasticity finite element method(CPFEM) and extended finite element method(XFEM) were used to simulate th...A unit cell including the matrix, precipitation free zone(PFZ) and grain boundary was prepared, and the crystal plasticity finite element method(CPFEM) and extended finite element method(XFEM) were used to simulate the propagation of cracks at grain boundary. Simulation results show that the crystallographic orientation of PFZ has significant influence on crack propagation, which includes the crack growth direction and crack growth velocity. The fracture strain of soft orientation is larger than that of hard orientation due to the role of reducing the stress intensity at grain boundary in intergranular brittle fracture. But in intergranular ductile fracture, the fracture strain of soft orientation may be smaller than that of hard orientation due to the roles of deformation localization.展开更多
In this paper, the extended finite element method (XFEM) is adopted to analyze the interaction between a single macroscopic inclusion and a single macroscopic crack as well as that between multiple macroscopic or micr...In this paper, the extended finite element method (XFEM) is adopted to analyze the interaction between a single macroscopic inclusion and a single macroscopic crack as well as that between multiple macroscopic or microscopic defects under thermal/mechanical load. The effects of different shapes of multiple inclusions on the material thermomechanical response are investigated, and the level set method is coupled with XFEM to analyze the interaction of multiple defects. Further, the discretized extended finite element approximations in relation to thermoelastic problems of multiple defects under displacement or temperature field are given. Also, the interfaces of cracks or materials are represented by level set functions, which allow the mesh assignment not to conform to crack or material interfaces. Moreover, stress intensity factors of cracks are obtained by the interaction integral method or the M-integral method, and the stress/strain/stiffness fields are simulated in the case of multiple cracks or multiple inclusions. Finally, some numerical examples are provided to demonstrate the accuracy of our proposed method.展开更多
Extended finite element method (XFEM) implementation of the interaction integral methodology for evaluating the stress intensity factors (SIF) of the mixed-mode crack problem is presented. A discontinuous function and...Extended finite element method (XFEM) implementation of the interaction integral methodology for evaluating the stress intensity factors (SIF) of the mixed-mode crack problem is presented. A discontinuous function and the near-tip asymptotic function are added to the classic finite element approximation to model the crack behavior. Two-state integral by the superposition of actual and auxiliary fields is derived to calculate the SIFs. Applications of the proposed technique to the inclined centre crack plate with inclined angle from 0° to 90° and slant edge crack plate with slant angle 45°, 67.5° and 90° are presented, and comparisons are made with closed form solutions. The results show that the proposed method is convenient, accurate and computationally efficient.展开更多
文摘为研究冻胀荷载对双裂隙岩体裂纹扩展及贯通机制的影响,文章基于扩展有限元法(extended finite element method,XFEM),分析冻胀力作用下不同岩桥参数双裂隙试样的裂纹扩展特征和破坏形式,探究在冻胀力和侧向卸荷共同作用下双裂隙试样的裂纹扩展贯通规律。结果表明:基于XFEM的数值模拟结果与试验中的裂纹扩展路径基本吻合,验证了XFEM能够有效地应用于双裂隙岩体的裂纹扩展模拟;非岩桥区冻胀裂纹的扩展方向与预制裂隙走向相同,而岩桥区裂纹的扩展方向受到冻胀应力的影响,裂纹扩展方向偏向于另一条预制裂隙位置;冻胀裂纹的扩展模式受到围压的影响,随着围压增加,侧向卸荷过程中裂纹扩展模式由拉张模式变成拉剪混合模式,裂纹扩展方向也发生偏转。研究方法和结果可为低温裂隙岩体裂纹扩展相关研究提供参考。
基金Projects(51475162,51405153)supported by the National Natural Science Foundation of ChinaProject(14JJ5015)supported by the Hunan Provincial Natural Science Foundation,China
文摘A unit cell including the matrix, precipitation free zone(PFZ) and grain boundary was prepared, and the crystal plasticity finite element method(CPFEM) and extended finite element method(XFEM) were used to simulate the propagation of cracks at grain boundary. Simulation results show that the crystallographic orientation of PFZ has significant influence on crack propagation, which includes the crack growth direction and crack growth velocity. The fracture strain of soft orientation is larger than that of hard orientation due to the role of reducing the stress intensity at grain boundary in intergranular brittle fracture. But in intergranular ductile fracture, the fracture strain of soft orientation may be smaller than that of hard orientation due to the roles of deformation localization.
基金supported by the National Natural Science Foundation of China (Grants 11471262, 50976003, 51136005)
文摘In this paper, the extended finite element method (XFEM) is adopted to analyze the interaction between a single macroscopic inclusion and a single macroscopic crack as well as that between multiple macroscopic or microscopic defects under thermal/mechanical load. The effects of different shapes of multiple inclusions on the material thermomechanical response are investigated, and the level set method is coupled with XFEM to analyze the interaction of multiple defects. Further, the discretized extended finite element approximations in relation to thermoelastic problems of multiple defects under displacement or temperature field are given. Also, the interfaces of cracks or materials are represented by level set functions, which allow the mesh assignment not to conform to crack or material interfaces. Moreover, stress intensity factors of cracks are obtained by the interaction integral method or the M-integral method, and the stress/strain/stiffness fields are simulated in the case of multiple cracks or multiple inclusions. Finally, some numerical examples are provided to demonstrate the accuracy of our proposed method.
基金Projects(41172244,41072224) supported by the National Natural Science Foundation of ChinaProject(2009GGJS-037) supported by the Foundation of Youths Key Teacher by the Henan Educational Committee,China
文摘Extended finite element method (XFEM) implementation of the interaction integral methodology for evaluating the stress intensity factors (SIF) of the mixed-mode crack problem is presented. A discontinuous function and the near-tip asymptotic function are added to the classic finite element approximation to model the crack behavior. Two-state integral by the superposition of actual and auxiliary fields is derived to calculate the SIFs. Applications of the proposed technique to the inclined centre crack plate with inclined angle from 0° to 90° and slant edge crack plate with slant angle 45°, 67.5° and 90° are presented, and comparisons are made with closed form solutions. The results show that the proposed method is convenient, accurate and computationally efficient.
