Compaction process simulation and residual stress prediction of green PM compact were carried out with elasto-plastic 3D FEA based on the modified Drueker-Prager Cap model in Abaqus. The model parameters of the invest...Compaction process simulation and residual stress prediction of green PM compact were carried out with elasto-plastic 3D FEA based on the modified Drueker-Prager Cap model in Abaqus. The model parameters of the investigated powder Distaloy AE were determined as functions of relative density through typical mechanical property tests of powder. The model was implemented as a user subroutine USDFLD. Single sided compaction of a d20 ram^5 mm disk green compact of Distaloy AE was simulated, and the residual stress of the disk after ejection was predicted with FEA. The FEA results of the compaction process and the residual stress of the disk show good agreement with compaction experiments and X-ray diffraction measurements, which validates the model and its parameters. The results indicate that the compressive residual stresses exist mainly in a thin layer on the side surface, but the residual stresses are very small on the top and bottom surfaces.展开更多
The vector model for gravitational field is a modified theory of gravitational field. In this model, the gravitational field is a vector field and its source is the gravitational mass of matter. This model predicts th...The vector model for gravitational field is a modified theory of gravitational field. In this model, the gravitational field is a vector field and its source is the gravitational mass of matter. This model predicts the existence of a new universal object after the black hole disappeared. It is named the white-black hole （or white hole） in the vector model for the gravitational field. The white- black hole has many interesting properties different from that of black hole in Einstein＇s theory of gravity. This paper presents an investigation of the spherically-symmetric pressure free collapse of a white-black hole in the vector model for gravitational field from the point of view of an observer at infinity and on its surface. The obtained results have many interesting differences compared with that in the spherically-symmetric pressure free collapse of black holes. In addition, the metric of space-time of the white-black hole in modified Eddington-Finkelstein coordinates and modified Kruskal-Szekeres coordinates are found.展开更多
In order to study the distribution of lateral floor abutment pressure at a working face,we first used elasticity theory to establish a distribution model of lateral floor abutment pressure and then analysed its distri...In order to study the distribution of lateral floor abutment pressure at a working face,we first used elasticity theory to establish a distribution model of lateral floor abutment pressure and then analysed its distribution.Second,we established a three-dimensional numerical simulation model of the Haizi Coal Mine No.86 mining area by using FLAC^（3D）（ITASCA Consulting Group） software.We investigated the distribution of lateral floor abutment pressure of a stope,which indicated that the position of abutment pressure peak varies at different floor depths.We then determined the rational reinforcement range of a floor roadway,based on the conclusion reached earlier.Finally,we used our conclusions in support of the No.86 mining area crossing-roadway.The supported crossing-roadway remained stable when mining the upper workface,which validates the accuracy of our numerical simulation and provides a future reference for the support of span-roadways under similar conditions.展开更多
基金Project(2009ZX04004-031-04) supported by the National Science and Technology Major Project of the Ministry of Science and Technology of China
文摘Compaction process simulation and residual stress prediction of green PM compact were carried out with elasto-plastic 3D FEA based on the modified Drueker-Prager Cap model in Abaqus. The model parameters of the investigated powder Distaloy AE were determined as functions of relative density through typical mechanical property tests of powder. The model was implemented as a user subroutine USDFLD. Single sided compaction of a d20 ram^5 mm disk green compact of Distaloy AE was simulated, and the residual stress of the disk after ejection was predicted with FEA. The FEA results of the compaction process and the residual stress of the disk show good agreement with compaction experiments and X-ray diffraction measurements, which validates the model and its parameters. The results indicate that the compressive residual stresses exist mainly in a thin layer on the side surface, but the residual stresses are very small on the top and bottom surfaces.
文摘The vector model for gravitational field is a modified theory of gravitational field. In this model, the gravitational field is a vector field and its source is the gravitational mass of matter. This model predicts the existence of a new universal object after the black hole disappeared. It is named the white-black hole （or white hole） in the vector model for the gravitational field. The white- black hole has many interesting properties different from that of black hole in Einstein＇s theory of gravity. This paper presents an investigation of the spherically-symmetric pressure free collapse of a white-black hole in the vector model for gravitational field from the point of view of an observer at infinity and on its surface. The obtained results have many interesting differences compared with that in the spherically-symmetric pressure free collapse of black holes. In addition, the metric of space-time of the white-black hole in modified Eddington-Finkelstein coordinates and modified Kruskal-Szekeres coordinates are found.
基金supported by the National Basic Research Program of China(No.2010CB226805)the National Natural Science Foundation of China(Nos.50874103 and 50974115)+1 种基金the Natural Science Foundation of Jiangsu Province(No.KB2008135)the State Key Laboratory Fund(No.SKLGDUEK0905)
文摘In order to study the distribution of lateral floor abutment pressure at a working face,we first used elasticity theory to establish a distribution model of lateral floor abutment pressure and then analysed its distribution.Second,we established a three-dimensional numerical simulation model of the Haizi Coal Mine No.86 mining area by using FLAC^（3D）（ITASCA Consulting Group） software.We investigated the distribution of lateral floor abutment pressure of a stope,which indicated that the position of abutment pressure peak varies at different floor depths.We then determined the rational reinforcement range of a floor roadway,based on the conclusion reached earlier.Finally,we used our conclusions in support of the No.86 mining area crossing-roadway.The supported crossing-roadway remained stable when mining the upper workface,which validates the accuracy of our numerical simulation and provides a future reference for the support of span-roadways under similar conditions.
