Finite Element Analysis of Tire Curing Process

Abstract

Curing is one of the most important steps in the tire manufacturing process. During this process, a green tire is formed to the desired shape and the compound is converted to a strong, elastic material to meet tire performance needs. The process of curing is usually accomplished under pressure and an elevated temperature provided by the mold. The curing process is energy consuming and has a strong effect on material properties. To attain an optimal state of cure for different compounds of various dimensions at minimal capital and energy costs requires proper evaluation of the state of cure in a tire. Various numerical models have been proposed to determine the state of cure of rubber compounds in molds. Their applications are limited to simple geometry and boundary conditions. For a tire, which has complex shape and variable boundary conditions and is built from layers of rubber compounds and fiber/rubber composites, the finite element method appears to be an ideal candidate because of its versatility. In this paper, a simulator for the tire curing processes was developed based on the finite element method of an axisymmetric heat transfer problem for composite materials. The anisotropy of heat transfer properties of composite materials, the dependence of properties of rubber compounds on the temperature and/or the extent of cure, the time-varying boundary conditions which include the cooldown of the tire out of the press and the rigorous cure kinetic models are taken into account. The numerical simulation results of a truck tire curing process show that the simulator successfully describes the variation trends in temperature and in state of cure with the tire curing process. It also serves as the core module of an optimization algorithm, which is being developed for the tire curing and rubber formulation designs.