When there exists anisotropy in underground media elastic parameters of the observed coordinate possibly do not coincide with that of the natural coordinate. According to the theory that the density of potential energ...When there exists anisotropy in underground media elastic parameters of the observed coordinate possibly do not coincide with that of the natural coordinate. According to the theory that the density of potential energy, dissipating energy is independent of the coordinate, the relationship of elastic parameters between two coordinates is derived for two-phase anisotropic media. Then, pseudospectral method to solve wave equations of two-phase anisotropic media is derived. At last, we use this method to simulate wave propagation in two-phase anisotropic media four types of waves are observed in the snapshots, i.e., fast P wave and slow P wave, fast S wave and slow S wave. Shear wave splitting, SV wave cusps and elastic wave reflection and transmission are also observed.展开更多
Based on the study of passive articulated rover,a complete suspension kinematics model from wheel to inertial reference frame is presented,which uses D-H method of manipulator and presentation with Euler angle of pitc...Based on the study of passive articulated rover,a complete suspension kinematics model from wheel to inertial reference frame is presented,which uses D-H method of manipulator and presentation with Euler angle of pitch,roll and yaw.An improved contact model is adopted aimed at the loose and rough lunar terrain.Using this kinematics model and numerical continuous and discrete Newton's method with iterative factor,the numerical method for estimation of kinematical parameters of articulated rovers on loose and rough terrain is constructed.To demonstrate this numerical method,an example of two torsion bar rocker-bogie lunar rover with eight wheels is presented.Simulation results show that the numerical method for estimation of kinematical parameters of articulated rovers based on improved contact model can improve the precision of kinematical estimation on loose and rough terrain and decrease errors caused by contact models established based on general hypothesis.展开更多
The model of nuclear reactor dynamics is an initial-boundary value problems of a cou- pled nonlinear integrodifferential equation system of one ordinary differential equation and one par-- tial differential equation. ...The model of nuclear reactor dynamics is an initial-boundary value problems of a cou- pled nonlinear integrodifferential equation system of one ordinary differential equation and one par-- tial differential equation. In this this,paper,a linearized difference scheme is derived by the method of reduction of order.It is proved that the scheme is uniquely solvable and unconditionally convergent with the convergence rate of order two both in discrete H1norm and in discrete maxinum narm,and one needs only to solve a tridiagonal system of linear algebraic equations at each time lev- el.The method of reduction of order is an indirect constructing-difference-scheme method,which aim is for the analysis of solvablity and convergence of the constructed difference scheme.展开更多
A novel method for calculating the magnetic stiffness matrix was proposed for the numerical analysis of the magneto-elastic stability of complicated current-carrying structures aim- ing for application in the magneto-...A novel method for calculating the magnetic stiffness matrix was proposed for the numerical analysis of the magneto-elastic stability of complicated current-carrying structures aim- ing for application in the magneto-elastic behavior of the tokamak system. A code based on the proposed method was developed and applied to the numerical analysis of two typical current- carrying structures. The good consistency of the numerical and analytical results validated the proposed method and the related numerical code.展开更多
充填体—边界介质组合体接触面的剪切力学特性与参数是研究充填采场应力分布与充填体揭露稳定性评价的基础数据。通过室内直剪试验与RFPA^(3D)数值模拟试验联合手段,对3种灰砂配比(1∶4、1∶8和1∶20)、4种接触面法向应力(50 k Pa、100 ...充填体—边界介质组合体接触面的剪切力学特性与参数是研究充填采场应力分布与充填体揭露稳定性评价的基础数据。通过室内直剪试验与RFPA^(3D)数值模拟试验联合手段,对3种灰砂配比(1∶4、1∶8和1∶20)、4种接触面法向应力(50 k Pa、100 k Pa、150 k Pa和200 k Pa)的充填体—边界介质组合体(充填体—围岩、充填体—矿体、胶结充填体—非胶结充填体)的剪切力学特性与声发射特征、黏聚力和内摩擦角参数变化规律进行了分析。结果表明:随灰砂配比降低,充填体—围岩组合体峰值剪切强度减少,破坏模式由脆性变为延性,破坏形态由颗粒粘连、块状粘连到凸起体尖端被剪断。灰砂配比1∶4组合体发生破坏时剪切应力垂直下降,振铃计数率突然骤增,其他阶段振铃计数率相对较小。灰砂配比1∶8和1∶20组合体从裂隙压密到破坏阶段,声发射振铃计数率密集,剪切过程中有明显剪胀变形;充填体—边界介质组合体接触面的峰值剪切强度随法向应力、灰砂配比降低而减少。胶结充填体—围岩接触面峰值剪切强度略小于胶结充填体—矿体强度,胶结—非胶结充填体组合体峰值强度远小于胶结充填体—矿岩组合体,接近非胶结充填体自身强度;充填体—边界介质组合体接触面的黏聚力和内摩擦角随灰砂配比降低而减少。充填体—围岩与充填体—矿体黏聚力和内摩擦角接近,胶结—非胶结充填体组合体黏聚力和内摩擦角参数远小于胶结充填体—矿岩组合体。研究结果拓展了充填体—边界介质组合体剪切力学特性获取方法,为充填采场稳定性分析提供了基础数据。展开更多
To simulate the mechanical behavior of the FCC crystal with the lower Peierls stress, the stiff property and physical meaning of the differential equation group consisting of dislocation evolution and mechanical state...To simulate the mechanical behavior of the FCC crystal with the lower Peierls stress, the stiff property and physical meaning of the differential equation group consisting of dislocation evolution and mechanical state was investigated based on the 3-D discrete dislocation dynamics; the results indicate that the differential equation group is serious stiff, namely the external stress changes more quickly than dislocation evolution. Using the established numerical algorithm, the mechanical behavior of FCC crystal was simulated with the dislocations located in the parallel slip planes, and the effect of strain rate on the dislocation configuration and mechanical behavior, and the sat- uration process of mobile dislocation were discussed. The simulation results indicate that the numerical algorithm can efficiently simulate the dislocation dipole and the low strain rate loading.展开更多
文摘When there exists anisotropy in underground media elastic parameters of the observed coordinate possibly do not coincide with that of the natural coordinate. According to the theory that the density of potential energy, dissipating energy is independent of the coordinate, the relationship of elastic parameters between two coordinates is derived for two-phase anisotropic media. Then, pseudospectral method to solve wave equations of two-phase anisotropic media is derived. At last, we use this method to simulate wave propagation in two-phase anisotropic media four types of waves are observed in the snapshots, i.e., fast P wave and slow P wave, fast S wave and slow S wave. Shear wave splitting, SV wave cusps and elastic wave reflection and transmission are also observed.
基金Sponsored by the National High Technology Research and Development Program of China(863 Program)(Grant No.2006AA04Z231)the National Science Foundation of Heilongjiang Province(Grant No.ZJG0709)"The 111 Project"(Grant No.B07018)
文摘Based on the study of passive articulated rover,a complete suspension kinematics model from wheel to inertial reference frame is presented,which uses D-H method of manipulator and presentation with Euler angle of pitch,roll and yaw.An improved contact model is adopted aimed at the loose and rough lunar terrain.Using this kinematics model and numerical continuous and discrete Newton's method with iterative factor,the numerical method for estimation of kinematical parameters of articulated rovers on loose and rough terrain is constructed.To demonstrate this numerical method,an example of two torsion bar rocker-bogie lunar rover with eight wheels is presented.Simulation results show that the numerical method for estimation of kinematical parameters of articulated rovers based on improved contact model can improve the precision of kinematical estimation on loose and rough terrain and decrease errors caused by contact models established based on general hypothesis.
基金NSF of Jiangsu Province (BK97004) and NSF of China (19801007)
文摘The model of nuclear reactor dynamics is an initial-boundary value problems of a cou- pled nonlinear integrodifferential equation system of one ordinary differential equation and one par-- tial differential equation. In this this,paper,a linearized difference scheme is derived by the method of reduction of order.It is proved that the scheme is uniquely solvable and unconditionally convergent with the convergence rate of order two both in discrete H1norm and in discrete maxinum narm,and one needs only to solve a tridiagonal system of linear algebraic equations at each time lev- el.The method of reduction of order is an indirect constructing-difference-scheme method,which aim is for the analysis of solvablity and convergence of the constructed difference scheme.
基金supported by National Magnetic Confinement Fusion Program of China (Nos. 2009GB104002, 2013GB113005)National Natural Science Foundation of China (Nos. 50977070, 51277139, 11021202)the National Basic Research Program of National China(No. 2011CB610303)
文摘A novel method for calculating the magnetic stiffness matrix was proposed for the numerical analysis of the magneto-elastic stability of complicated current-carrying structures aim- ing for application in the magneto-elastic behavior of the tokamak system. A code based on the proposed method was developed and applied to the numerical analysis of two typical current- carrying structures. The good consistency of the numerical and analytical results validated the proposed method and the related numerical code.
文摘充填体—边界介质组合体接触面的剪切力学特性与参数是研究充填采场应力分布与充填体揭露稳定性评价的基础数据。通过室内直剪试验与RFPA^(3D)数值模拟试验联合手段,对3种灰砂配比(1∶4、1∶8和1∶20)、4种接触面法向应力(50 k Pa、100 k Pa、150 k Pa和200 k Pa)的充填体—边界介质组合体(充填体—围岩、充填体—矿体、胶结充填体—非胶结充填体)的剪切力学特性与声发射特征、黏聚力和内摩擦角参数变化规律进行了分析。结果表明:随灰砂配比降低,充填体—围岩组合体峰值剪切强度减少,破坏模式由脆性变为延性,破坏形态由颗粒粘连、块状粘连到凸起体尖端被剪断。灰砂配比1∶4组合体发生破坏时剪切应力垂直下降,振铃计数率突然骤增,其他阶段振铃计数率相对较小。灰砂配比1∶8和1∶20组合体从裂隙压密到破坏阶段,声发射振铃计数率密集,剪切过程中有明显剪胀变形;充填体—边界介质组合体接触面的峰值剪切强度随法向应力、灰砂配比降低而减少。胶结充填体—围岩接触面峰值剪切强度略小于胶结充填体—矿体强度,胶结—非胶结充填体组合体峰值强度远小于胶结充填体—矿岩组合体,接近非胶结充填体自身强度;充填体—边界介质组合体接触面的黏聚力和内摩擦角随灰砂配比降低而减少。充填体—围岩与充填体—矿体黏聚力和内摩擦角接近,胶结—非胶结充填体组合体黏聚力和内摩擦角参数远小于胶结充填体—矿岩组合体。研究结果拓展了充填体—边界介质组合体剪切力学特性获取方法,为充填采场稳定性分析提供了基础数据。
文摘To simulate the mechanical behavior of the FCC crystal with the lower Peierls stress, the stiff property and physical meaning of the differential equation group consisting of dislocation evolution and mechanical state was investigated based on the 3-D discrete dislocation dynamics; the results indicate that the differential equation group is serious stiff, namely the external stress changes more quickly than dislocation evolution. Using the established numerical algorithm, the mechanical behavior of FCC crystal was simulated with the dislocations located in the parallel slip planes, and the effect of strain rate on the dislocation configuration and mechanical behavior, and the sat- uration process of mobile dislocation were discussed. The simulation results indicate that the numerical algorithm can efficiently simulate the dislocation dipole and the low strain rate loading.
