Papers by Author: Zhi Gang Li

Abstract: It is a technical challenge to insert sipes in a multi-sipe radial tire mold. The authors have invented a new method to make tire mold patterns by EDM which has solved the problems of inserting the sipes, characterized in that the patterns and sipes can be made at the same time, and as they are made as one body after EDM, there is no need to manually insert the sipes. The multi-sipe tire molds made by EDM meet the technical standards of famous international tire companies, and evaluation results show that this process works very well in the manufacture of complicated tire molds.

Abstract: A novel hybrid method is proposed in the paper, which is an assistant tool for product designers to estimate springback in sheet metal forming process at the preliminary design stage. In the hybrid method, the forming results are obtained firstly by an inverse finite element approach (IA) with a membrance element. The thickness strain and stress can be calculated according to the approximate curvature radius of the discrete meshes. Then, a rotation-free shell element is employed, with only three displacements at the corner nodes of the element, to calculate the springback. To verify the accuracy and efficiency of the hybrid method, the numerical results of the hybrid method on two benchmark tests are compared with experimental results.

Abstract: A special elasto-plastic dynamic finite element code named RingForm has been developed to analyze cold ring rolling process. Central difference method was introduced to solve the dynamic explicit finite element equations. Strain state was estimated by the value of yield function of the last and the present time step. To reduce the accumulative error caused by elasto-plastic constitutive relations, the radial return algorithm was employed. In comparison with the experimental results, the cold ring rolling process of a ring with rectangular section has been simulated to verify the accuracy and stability of the system solver.