变截面柔性杆撞击动力学子结构法研究

采用固定界面模态综合子结构法对柔性体的撞击问题进行研究.首先提出研究的力学模型,将模型子结构离散化,导出撞击时多自由度高度非线性的动力学方程,运用无条件稳定的直接积分法(Newmark法)对动力学方程进行求解,得到了变截面柔性杆撞击力的时间历程和其他动力响应.通过重点研究柔性体子结构单元离散的划分与其物理参数之间的关系对计算结果的影响,得到了变截面柔性杆子结构离散的基本准则.此外,首次实现了对柔性体中瞬态应力波和速度波传播过程的刻画,可以显示撞击瞬态波多个波阵面传播.研究结果表明子结构法能够完整地描述变截面柔性体的撞击过程和分析撞击瞬态波传播机理,可以更广泛地应用于其他实际柔性机械系统撞击动力学问题的研究.

Research on substructure technique for dynamics of variable section flexible rod with impact

The fixed-interface mode synthesis substructure technique is applied to solve the impact problem of a flexible structure. A dynamics model was built. The flexible structure was discretized by the substructure technique. A highly nonlinear dynamics equation was derived. The Newmark method, a stablely direct numerical integral method, was yielded for solving the equation. The impact force history and the dynamics responses of the flexible structure were calculated. The present investigation focused on the influences of the element number of substructures and physical parameters of the variable cross-section rod on the accuracy in the numerical analysis. The basic rule of substructure discretization of variable cross-section flexible rod was obtained. The propagation of the transient stress wave and velocity wave along the variable section flexible bar during impact can be depicted by the substructure technique firstly. The numerical results can show the travelling of the wavefront of the transient waves. The present investigation shows that the substructure technique can describe the impact process and analyze the mechanism of the propagation of the impact transient waves. The substructure technique might be applied widely to the impact problems of flexible mechanical systems in engineering.