Numerical and experimental study on dynamic characteristics of planar mechanism with mixed clearances

Clearances in joints are unavoidable due to assemblage, manufacturing errors and wear, which will lead to poor dynamic performances and undesirable vibrations due to impact forces in clearance joints. In dynamics analysis of planar mechanical system, it is usually assumed that the revolute joint is planar joint with radial clearance. However, the axial clearance in the revolute joint and the clearance in the translational joint are ignored. In fact, even planar mechanical systems may exhibit out-of-plane motion due to misalignments. In this work, a planar slider-crank mechanism is used as the example to investigate the effects of mixed clearances on the dynamic responses of planar mechanical system considering radial and axial clearances in spatial revolute joint due to axis misalignment as well as clearance in planar translational joint. The dynamic responses of the planar slider-crank mechanism system with two spatial revolute clearance joints and a planar translation clearance joint are investigated using computational and experimental methodology. The mathematic model of the spatial revolute clearance joint and the planar translational clearance joint are presented. The clearance joints are considered as force constraints and the joint components of an imperfect joint with clearance are modeled as contact bodies. The normal contact force model of clearance joint is established using continuous contact force model. The friction effect is considered using modified Coulomb friction model. Different case studies are presented and discussed to investigate the effects of the mixed clearances on the dynamic responses of the planar slider-crank mechanism.