The distinct element method(DEM)has been used successfully for the dynamic analysis of rigid block sys- tems.One of many difficulties associated with DEM is modeling of damping.In this paper,new procedures are propose...The distinct element method(DEM)has been used successfully for the dynamic analysis of rigid block sys- tems.One of many difficulties associated with DEM is modeling of damping.In this paper,new procedures are proposed for the damping modeling and its numerical implementation in distinct element analysis of rigid muhi-block systems.The stiff- ness proportional damping is constructed for the prescribed damping ratio,based on the non-zero fundamental frequency ef- fective during the time interval while the boundary conditions remain essentially constant.At this time interval,the funda- mental frequency can be estimated without complete eigenvalue analysis.The damping coefficients will vary while the damp- ing ratio remains the same throughout the entire analysis.A new numerical procedure is developed to prevent unnecessary energy loss that can occur during the separation phases.These procedures were implemented in the development of the dis- tinet element method for the dynamic analyses of piled multi-block systems.The analysis results |or the single-block and two-block systems were in a good agreement with the analytic predictions.Applications to the seismic analyses of piled four- block systems revealed that the new procedures can make a significant difference and may lead to much-improved results.展开更多
The orthogonality of eigenvector is a precondition to compute the dynamic responses of linear multi-rigid-flexible-body system using the classical modal analysis method. For a linear multi-rigid-flexible-body system, ...The orthogonality of eigenvector is a precondition to compute the dynamic responses of linear multi-rigid-flexible-body system using the classical modal analysis method. For a linear multi-rigid-flexible-body system, the eigenfunction does not satisfy the orthogonality under ordinary meaning. A new concept--augmented eigenvector is introduced, which is used to overcome the orthogonality problem of eigenvectors of linear multi-rigid-flexible-body system. The constitution method and the orthogonality of augmented eigenvector are expatiated. After the orthogonality of augmented eigenvector is acquired, the coupling of coordinates in dynamics equations can be released, which makes it possible to analyze exactly the dynamic responses of linear multi-rigid-flexible-body system using the classical modal analysis method.展开更多
In this paper, by defining new state vectors and developing new transfer matrices of various elements mov- ing in space, the discrete time transfer matrix method of multi-rigid-flexible-body system is expanded to stud...In this paper, by defining new state vectors and developing new transfer matrices of various elements mov- ing in space, the discrete time transfer matrix method of multi-rigid-flexible-body system is expanded to study the dynamics of multibody system with flexible beams moving in space. Formulations and numerical example of a rigid- flexible-body three pendulums system moving in space are given to validate the method. Using the new method to study the dynamics of multi-rigid-flexible-body system mov- ing in space, the global dynamics equations of system are not needed, the orders of involved matrices of the system are very low and the computational speed is high, irrespec- tive of the size of the system. The new method is simple, straightforward, practical, and provides a powerful tool for multi-rigid-flexible-body system dynamics.展开更多
采煤机摇臂壳体是采煤机的重要部件及薄弱环节,其寿命直接影响采煤机的工作性能。为研究采煤机截割复杂煤层时滚筒所受载荷对其摇臂壳体寿命的影响,以MG325型采煤机截割兖州矿区杨村煤矿17层含夹矸煤壁为工程背景,通过虚拟样机技术和离...采煤机摇臂壳体是采煤机的重要部件及薄弱环节,其寿命直接影响采煤机的工作性能。为研究采煤机截割复杂煤层时滚筒所受载荷对其摇臂壳体寿命的影响,以MG325型采煤机截割兖州矿区杨村煤矿17层含夹矸煤壁为工程背景,通过虚拟样机技术和离散单元法-多柔体动力学(Discrete Element Method-Multi Flexible Body Dynamics,DEM-MFBD)双向耦合技术,利用离散元仿真软件EDEM和多体系统动力学仿真软件RecurDyn,基于实际工况获得采煤机螺旋滚筒的外负载。在RecurDyn仿真平台中,建立采煤机摇臂三维实体模型并进行边界条件的设置及摇臂壳体的柔性化,通过软件本身的Durability疲劳耐久分析模块,计算摇臂壳体的疲劳寿命。利用专业绘图软件Origin绘制2个软件后处理的载荷曲线图,发现其走势较为一致,其后处理数据均值,标准差等相接近,证明两者耦合效果较好。结果表明:MG325型采煤机以滚筒转速83.5 r/min,截深600 mm,牵引速度5 m/min截割复杂煤层时,滚筒所受载荷具有较为强烈的载荷波动现象,由等效应力云图可得摇臂壳体的最大等效应力为230.51 MPa,且应力较大处集中位于壳体的各个齿轮轴孔处、凹槽处以及上下耳过渡处,经应力疲劳分析后得其最小寿命位于壳体的齿轮轴孔处,循环次数为8.3215×10~6次。本研究方法可为复杂条件下工矿装备大型结构件的优化设计提供参考。展开更多
A theoretical study is presented herein on the pen- etration of a semi-infinite target by a spherical-headed long rod for Yp 〉 S, where Yp is the penetrator strength and S is the static target resistance. For Yp 〉 S...A theoretical study is presented herein on the pen- etration of a semi-infinite target by a spherical-headed long rod for Yp 〉 S, where Yp is the penetrator strength and S is the static target resistance. For Yp 〉 S, depending upon initial impact velocity, there exist three types of penetration, namely, penetration by a rigid long rod, penetration by a deforming non-erosive long rod and penetration by an erosive long rod. If the impact velocity of the penetrator is higher than the hydrodynamic velocity （VH）, it will penetrate the target in an erosive mode; if the impact velocity lies between the hydrodynamic velocity （VH） and the rigid body velocity （VR）, it will penetrate the target in a deformable mode; if the impact velocity is less than the rigid body velocity （VR）, it will penetrate the target in a rigid mode. The critical conditions for the transition among these three penetration modes are proposed. It is demonstrated that the present model predictions correlate well with the experimental observations in terms of depth of penetration （DOP） and the critical transition conditions.展开更多
文摘The distinct element method(DEM)has been used successfully for the dynamic analysis of rigid block sys- tems.One of many difficulties associated with DEM is modeling of damping.In this paper,new procedures are proposed for the damping modeling and its numerical implementation in distinct element analysis of rigid muhi-block systems.The stiff- ness proportional damping is constructed for the prescribed damping ratio,based on the non-zero fundamental frequency ef- fective during the time interval while the boundary conditions remain essentially constant.At this time interval,the funda- mental frequency can be estimated without complete eigenvalue analysis.The damping coefficients will vary while the damp- ing ratio remains the same throughout the entire analysis.A new numerical procedure is developed to prevent unnecessary energy loss that can occur during the separation phases.These procedures were implemented in the development of the dis- tinet element method for the dynamic analyses of piled multi-block systems.The analysis results |or the single-block and two-block systems were in a good agreement with the analytic predictions.Applications to the seismic analyses of piled four- block systems revealed that the new procedures can make a significant difference and may lead to much-improved results.
文摘The orthogonality of eigenvector is a precondition to compute the dynamic responses of linear multi-rigid-flexible-body system using the classical modal analysis method. For a linear multi-rigid-flexible-body system, the eigenfunction does not satisfy the orthogonality under ordinary meaning. A new concept--augmented eigenvector is introduced, which is used to overcome the orthogonality problem of eigenvectors of linear multi-rigid-flexible-body system. The constitution method and the orthogonality of augmented eigenvector are expatiated. After the orthogonality of augmented eigenvector is acquired, the coupling of coordinates in dynamics equations can be released, which makes it possible to analyze exactly the dynamic responses of linear multi-rigid-flexible-body system using the classical modal analysis method.
基金supported by the Natural Science Foundation of China Government (10902051)the Natural Science Foundation of Jiangsu Province (BK2008046)the German Science Foundation
文摘In this paper, by defining new state vectors and developing new transfer matrices of various elements mov- ing in space, the discrete time transfer matrix method of multi-rigid-flexible-body system is expanded to study the dynamics of multibody system with flexible beams moving in space. Formulations and numerical example of a rigid- flexible-body three pendulums system moving in space are given to validate the method. Using the new method to study the dynamics of multi-rigid-flexible-body system mov- ing in space, the global dynamics equations of system are not needed, the orders of involved matrices of the system are very low and the computational speed is high, irrespec- tive of the size of the system. The new method is simple, straightforward, practical, and provides a powerful tool for multi-rigid-flexible-body system dynamics.
文摘采煤机摇臂壳体是采煤机的重要部件及薄弱环节,其寿命直接影响采煤机的工作性能。为研究采煤机截割复杂煤层时滚筒所受载荷对其摇臂壳体寿命的影响,以MG325型采煤机截割兖州矿区杨村煤矿17层含夹矸煤壁为工程背景,通过虚拟样机技术和离散单元法-多柔体动力学(Discrete Element Method-Multi Flexible Body Dynamics,DEM-MFBD)双向耦合技术,利用离散元仿真软件EDEM和多体系统动力学仿真软件RecurDyn,基于实际工况获得采煤机螺旋滚筒的外负载。在RecurDyn仿真平台中,建立采煤机摇臂三维实体模型并进行边界条件的设置及摇臂壳体的柔性化,通过软件本身的Durability疲劳耐久分析模块,计算摇臂壳体的疲劳寿命。利用专业绘图软件Origin绘制2个软件后处理的载荷曲线图,发现其走势较为一致,其后处理数据均值,标准差等相接近,证明两者耦合效果较好。结果表明:MG325型采煤机以滚筒转速83.5 r/min,截深600 mm,牵引速度5 m/min截割复杂煤层时,滚筒所受载荷具有较为强烈的载荷波动现象,由等效应力云图可得摇臂壳体的最大等效应力为230.51 MPa,且应力较大处集中位于壳体的各个齿轮轴孔处、凹槽处以及上下耳过渡处,经应力疲劳分析后得其最小寿命位于壳体的齿轮轴孔处,循环次数为8.3215×10~6次。本研究方法可为复杂条件下工矿装备大型结构件的优化设计提供参考。
基金supported by the National Natural Science Foundation of China (10872195)
文摘A theoretical study is presented herein on the pen- etration of a semi-infinite target by a spherical-headed long rod for Yp 〉 S, where Yp is the penetrator strength and S is the static target resistance. For Yp 〉 S, depending upon initial impact velocity, there exist three types of penetration, namely, penetration by a rigid long rod, penetration by a deforming non-erosive long rod and penetration by an erosive long rod. If the impact velocity of the penetrator is higher than the hydrodynamic velocity （VH）, it will penetrate the target in an erosive mode; if the impact velocity lies between the hydrodynamic velocity （VH） and the rigid body velocity （VR）, it will penetrate the target in a deformable mode; if the impact velocity is less than the rigid body velocity （VR）, it will penetrate the target in a rigid mode. The critical conditions for the transition among these three penetration modes are proposed. It is demonstrated that the present model predictions correlate well with the experimental observations in terms of depth of penetration （DOP） and the critical transition conditions.
