Contact Mechanics Analysis On Grasping Interface Of Forging Manipulator

Forging manufacturing is conducted in dynamic loads cases and under high temperatures. For the complex manufacturing conditions, the contact mechanical behavior between clamps and workpiece is changeable, and subsequently affecting the stability of the interface. It is necessary and significant to analyze the mechanical properties for those contact mechanical behavior.Accordingly, this thesis mainly concerns with both the static and dynamic mechanical properties between clamps and workpiece through numerical analysis. It provides practical guidelines for the structure design and motion control of forging manipulator; also it gives useful suggestions for solving the stability problem.This thesis mainly concerns with the following areas:Firstly, the circumferential distribution of contact pressure along the workpiece was discussed by using the implicit algorithm for the established 2-D grasping FE model. Also, series factors that would influence the contact mechanical properties, such as the constitutive model, the roundness and size of the work piece, friction coefficient of the contact interface, the angle of clamps were investigated. In addition, as the gravity of the work piece will generate large moment for the clamp center, based on the 2-D model analysis, the axial distribution of contact pressure along work piece in 3-D model under different conditions was discussed in detail.Secondly, since the manipulator will have a rebound behavior for the forging impact, and thus the clamping force will change accordingly as well, the dynamic contact mechanics during the forging operation is studied. Based on the simplified physical model, the influence of velocity, mass of the forging hammer, the stiffness of the manipulator, the spring back of clamp and maximum plastic strain of work piece have been discussed by using explicit dynamic algorithm. Moreover, from the grasping stability perspective, the change of contact force between the contact interfaces under forging impact is discussed. The discussion can provide with useful suggestions for the study of constant force output grasping system.