基于有限质点法的含间隙铰平面机构动力分析

The existence of clearances makes the bearings and journals of hinged joints prone to collision, thus making the dynamic response of mechanisms with clearances different from that of ideal mechanisms. Based on the finite particle method, a dynamic analysis of planar mechanisms with clearance hinges is carried out. Firstly, the particle motion control equations of the finite particle method and the internal force calculation formulas for planar beam elements are given. Then, the Lankarani - Nikravesh model and the modified Coulomb friction model are introduced to calculate the contact force and friction force during the collision process of the bearings and journals in the clearance hinges. A dynamic analysis of a planar four - bar mechanism and a crank - slider mechanism is carried out, verifying the correctness and effectiveness of the method in this paper. The analysis results show that: the clearance hinges have little impact on the displacement and velocity of the mechanism's motion, but cause a large oscillation in acceleration; compared with ideal hinges, the peak value of the contact force of the clearance hinges also increases significantly; compared with rigid mechanisms, the dynamic response caused by the clearance hinges in flexible mechanisms is smaller; and compared with a single clearance hinge, multiple clearance hinges will increase the dynamic effect of the mechanism.

间隙的存在使得铰节点的轴承和轴颈易发生碰撞,从而使带间隙机构的动力响应与理想机构不同。基于有限质点法,对含间隙铰的平面机构开展动力分析。首先给出有限质点法的质点运动控制方程和平面梁单元的内力计算公式。然后引入Lankarani-Nikravesh模型和修正库仑摩擦模型,来计算间隙铰中轴承和轴颈碰撞过程中的接触力和摩擦力。对平面四杆机构和曲柄滑块机构开展了动力分析,验证了该文方法的正确性和有效性。分析结果表明:间隙铰对机构运动的位移和速度影响不大,但使加速度有较大振荡;相比于理想铰,间隙铰的接触力峰值也有较大的增加;相比于刚性机构,柔性机构中间隙铰导致的动力响应要小;而相比于单个间隙铰,多个间隙铰将增大机构的动力效应。