Numerical analysis of the physical phenomena in the working zone in the rolling process of the round thread

摘要

Thread rolling is a very complicated technological process. To improve the quality of the product and reduce production cost of the round thread, we should know the physical phenomena existing in the contact zone between rolls and deform work pieces. Therefore, this paper presents the physical and mathematical models of deformations (displacements and strains) and stress in the cold process of round thread rolling. The process is initially considered in a geometrically and physically non-linear regime, as well as a boundary value problem. The physical phenomena on a typical incremental step were described using a step-by-step incremental procedure, with an updated Lagrangian formulation. The state of strains was described by Green-Lagrange's tensor, while the state of stress by the second symmetrical Pioli-Kirchhoff s tensor. The object was treated as an elastic (in the reversible zone) and visco-plastic body (in the non-reversible zone) with mixed hardening. The variational equation of motion in three dimensions for this case was proposed. Then, the finite elements methods (FEM) and dynamic explicit method (DEM) were used to obtain the solution. The application is developed for the method of finite elements in the ANSYS programme, which provides a complex time analysis for displacement, strains and stresses occurring in the object. The effective discrete computable model which counts minimum degrees of freedom and a guide to convergence of solutions for the maximum value of stresses and strains, is proposed. Examples of simulation of the influence on various process conditions on the states of strain and stress are presented.