作大范围回转运动柔性梁斜碰撞动力学研究

THE OBLIQUE IMPACT DYNAMIC STUDY FOR A FLEXIBLE BEAM UNDERGOING LARGE OVERALL MOTION

为正确估计由于碰撞引起的多柔体系统动力学特性的变化，针对作大范围回转运动的柔性梁与一固定斜面发生斜碰撞的情况，在考虑刚柔耦合效应的多柔体系统动力学建模理论的基础上，利用假设模态法建立起重力场作用下的柔性梁一致线性化动力学方程．为精细研究斜碰撞过程中系统的动力学行为，基于Hertz接触理论和非线性阻尼项建立法向碰撞接触模型，基于线性切向接触刚度建立柔性梁切向碰撞接触模型.提出的数值算法保证了计算结果的合理性，给出的仿真算例详细描述了柔性梁斜碰撞过程中的动力学特征．

The key to solve the iIllpact question during in flexible multi-b0dy systems is tocorrectly establish the impact-contact nlodel. S. Dubowskey[1~3] provides a 'impact pair model'to study the impact 0ccurring in Inechanislns due to clearances at different joints. Chen Bin[4,5]adopted the similar model to researcll the dynamic behavior of the space deployable mechanismscontaining joint clearances through numerical simulations and experiments. But the 'Impact pairmodel' assumed a linear viscous damping law and a Hertzian spring for modeling the contact forcesand the daxnping forces in impact surfaces, so this model can n0t be satisfied with the boundarycondition in c0ntact areas.A spring-dashpot In0dels, which can be contented with the contact boundary condition, isdeveloped by Wang & Lee[6]. The efficiency of this models is also testified through experiments,but the model is only suited t0 the normal impact situation.When oblique impact occurred between in multi-body systems, the friction effects on impact process is considered directly by using the sliding friction theory in traditional impact model.For correctly estimating the friction effects on oblique impact process, a tangential impact model should be studied to describe the stick phenomenon due to the tangential velocity reversing its direction.For correctly establishing the contact-impact model in oblique impact process,this paper adopted the spring-dashpot models to describe the normal impact process which satisfied with the contact boundary condition, the tangential movement in impact process is described by a tangential impact model which adopted a linear contact stiffness in tangential direction to consider the effects of friction force.For a flexible beam undergoing large overall motion impacting a fixed slope surface under the effects of gravity, a contact condition is described by using the displacement relationship between the tip of flexible beam and the fixed slope surface in the normal direction. The system dynamic equations of consistent linearization which including impact process are derived using the mode assumption method. Furthermore, the algorithms suited to the oblique impact are also presented in this paper.The dynamic property of the fiexible beam during oblique impacting process is minutely studied through an example, and the validity of the theories and the algorithms established in this paper is also testified by a numerical simulation example.