Continuum-based discrete element method(CDEM)is an explicit numerical method used for simulation of progressive failure of geological body.To improve the efficiency of contact detection and simplify the calculation st...Continuum-based discrete element method(CDEM)is an explicit numerical method used for simulation of progressive failure of geological body.To improve the efficiency of contact detection and simplify the calculation steps for contact forces,semi-spring and semi-edge are introduced in calculation.Semispring is derived from block vertex,and formed by indenting the block vertex into each face(24semisprings for a hexahedral element).The formation process of semi-edge is the same as that of semi-spring(24semi-edges for a hexahedral element).Based on the semi-springs and semi-edges,a new type of combined contact model is presented.According to this model,six contact types could be reduced to two,i.e.the semi-spring target face contact and semi-edge target edge contact.By the combined model,the contact force could be calculated directly(the information of contact type is not necessary),and the failure judgment could be executed in a straightforward way(each semi-spring and semi-edge own their characteristic areas).The algorithm has been successfully programmed in C++program.Some simple numerical cases are presented to show the validity and accuracy of this model.Finally,the failure mode,sliding distance and critical friction angle of Jiweishan landslide are studied with the combined model.展开更多
A quasi-three-dimensional shell element model, which can beeffectively used to simulate the flanging and spring-backdeformation, is introduced into the independently developed CAEsoftware, KMAS, In this model, a doubl...A quasi-three-dimensional shell element model, which can beeffectively used to simulate the flanging and spring-backdeformation, is introduced into the independently developed CAEsoftware, KMAS, In this model, a double surface contact algorithm,which allows the gap between punch and die to change, and a spring-back treatment scheme based on finite element meshing are described.And then the flanging and spring-back deformations of the retractor'skickstand of a railcar made of stamped thick metal plate arenumerically simulated. The simulation results of flanging deformationare compared with those of international commercial software,PAM-STAMP, and experimental ones. Finally, a predicting scheme ofspring-back quantily for this problem is given.展开更多
特高压直流GIL运行可靠性取决于内绝缘设计的可靠性。此外,导电元件直流电流密度的取值、弹簧触头的定位设计、GIL各元件中的绝缘件与金具连接处的楔形气隙的处理以及母线中支撑件的结构设计细节,都会对产品运行可靠性产生重大影响,不...特高压直流GIL运行可靠性取决于内绝缘设计的可靠性。此外,导电元件直流电流密度的取值、弹簧触头的定位设计、GIL各元件中的绝缘件与金具连接处的楔形气隙的处理以及母线中支撑件的结构设计细节,都会对产品运行可靠性产生重大影响,不能忽视。对于运行环境十分严酷的UHV DC GIL为保证内绝缘工作可靠性和减少气体维护工作量,文中还提出了高气密性结构设计。为适应-50℃低温运行要求,产品选用了液化温度很低的N_(2)/SF_(6)混合气体,对两种气体的配比,压力特性和绝缘特性进行了讨论与计算。还有产品的局放、气体密度及微水含量的监视系统的可靠性设计,都会对产品运行可靠性产生直接影响。文中对上述问题的研究成果作了介绍,可供高压直流产品设计使用。对其中未解的新技术如基于冷镜露点测试原理、微机电技术制作的智能气体湿度和密度监测装置、高压直流复合绝缘套管伞面局放起始场强提出了研究方案。文中提出的诸多GIL运行可靠性设计要点,对于其他超/特高压直流气体绝缘电器可参考选用。展开更多
基金the National Basic Research Program of the Ministry of Science and Technology of China (Grant No. 2010CB731506)the National Key Technology Research and Development Program of the Ministry of Science and Technology of China (Grant No. 2012BAK10B01)the Youth Science Fund of National Natural Science Foundation of China (Grant No. 11302230)
文摘Continuum-based discrete element method(CDEM)is an explicit numerical method used for simulation of progressive failure of geological body.To improve the efficiency of contact detection and simplify the calculation steps for contact forces,semi-spring and semi-edge are introduced in calculation.Semispring is derived from block vertex,and formed by indenting the block vertex into each face(24semisprings for a hexahedral element).The formation process of semi-edge is the same as that of semi-spring(24semi-edges for a hexahedral element).Based on the semi-springs and semi-edges,a new type of combined contact model is presented.According to this model,six contact types could be reduced to two,i.e.the semi-spring target face contact and semi-edge target edge contact.By the combined model,the contact force could be calculated directly(the information of contact type is not necessary),and the failure judgment could be executed in a straightforward way(each semi-spring and semi-edge own their characteristic areas).The algorithm has been successfully programmed in C++program.Some simple numerical cases are presented to show the validity and accuracy of this model.Finally,the failure mode,sliding distance and critical friction angle of Jiweishan landslide are studied with the combined model.
基金the National Natural Science Foundation of China(No.19832020)the Ministry of Education of China.
文摘A quasi-three-dimensional shell element model, which can beeffectively used to simulate the flanging and spring-backdeformation, is introduced into the independently developed CAEsoftware, KMAS, In this model, a double surface contact algorithm,which allows the gap between punch and die to change, and a spring-back treatment scheme based on finite element meshing are described.And then the flanging and spring-back deformations of the retractor'skickstand of a railcar made of stamped thick metal plate arenumerically simulated. The simulation results of flanging deformationare compared with those of international commercial software,PAM-STAMP, and experimental ones. Finally, a predicting scheme ofspring-back quantily for this problem is given.
文摘特高压直流GIL运行可靠性取决于内绝缘设计的可靠性。此外,导电元件直流电流密度的取值、弹簧触头的定位设计、GIL各元件中的绝缘件与金具连接处的楔形气隙的处理以及母线中支撑件的结构设计细节,都会对产品运行可靠性产生重大影响,不能忽视。对于运行环境十分严酷的UHV DC GIL为保证内绝缘工作可靠性和减少气体维护工作量,文中还提出了高气密性结构设计。为适应-50℃低温运行要求,产品选用了液化温度很低的N_(2)/SF_(6)混合气体,对两种气体的配比,压力特性和绝缘特性进行了讨论与计算。还有产品的局放、气体密度及微水含量的监视系统的可靠性设计,都会对产品运行可靠性产生直接影响。文中对上述问题的研究成果作了介绍,可供高压直流产品设计使用。对其中未解的新技术如基于冷镜露点测试原理、微机电技术制作的智能气体湿度和密度监测装置、高压直流复合绝缘套管伞面局放起始场强提出了研究方案。文中提出的诸多GIL运行可靠性设计要点,对于其他超/特高压直流气体绝缘电器可参考选用。
