Computational aspects of planar mechanisms with revolute joint clearances : modelization and simulation

This paper deals with a methodology to assess the influence of the revolute joint clearances in planar mechanisms that are constituted by rigid links and joints. The existence of a radial clearance in a revolute joint removes the two kinematic constraints associated with the ideal revolute joint, and, hence, two extra degrees of freedom are introduced. Thus, the journal can move freely inside the bearing boundaries. When the journal reaches the bearing wall an impact takes place and contact forces control the dynamic of the joint. While an ideal revolute joint imposes kinematic constraints to the systems, a revolute joint with clearance deals with force constraints. These impacts and the eventual continuous contact are described here by a force model that accounts for the geometric and material characteristics of the journal and bearing. The energy dissipative effects are introduced in the joint through the contact force model developed during the contact. An illustrative example shows how the dynamics of mechanisms can be influenced by the existence of joint clearances.Fundação para a Ciência e a Tecnologia and partially financed by Fundo Comunitário Europeu FEDER under project POCTI/EME/2001/38281, entitled ‘Dynamic of Mechanical Systems with joint Clearances and Imperfections