Papers by Author: Ji Long Yin

Abstract: Numerical simulation technology has been used widely in plastic forming area. However, the simulation of increasingly complex forming process leads to the generation of vast quantities of data, which implies much useful knowledge. Consequently domain knowledge is very significant to product design and process development in metal plastic forming area. The paper presented a new robust optimization method based on knowledge discovery from numerical simulation. Firstly, the knowledge discovery model from numerical simulation is established. In this model, interval-based rule presentation is adopted to describe the uncertainty of design parameters quantitatively to enhance the design robustness. Secondly, the optimization process based on knowledge discovery and management is presented, and genetic arithmetic is used to obtain the robust optimization parameter. Finally, the application to robust optimization of extrusion-forging processing is analyzed to show the scheme to be effective. The proposed method can overcome the pathologies in simulation optimization and improve the efficiency & robustness in design optimization.

Abstract: To examine the formability of a magnesium-based alloy AZ31 sheet, a temperature and strain rate related constitutive model for AZ31 sheet was developed based on tensile experiments. The relative parameters were obtained by fitting the equation to the experimental data. The comparison between the fitted and the experimental data proved the effectiveness of the model. Based on this model, the deep drawing process has been simulated with the finite element method and the limit drawing ratio (LDR) of AZ31 sheet was numerically studied. The study result was helpful to the application of the stamping technology for the magnesium alloy sheet.

Abstract: Most magnesium alloy components available for automobile are made through die casting. In this paper, PAM-CASTTM, commercial die casting simulation software based on the finite difference method, is employed to simulate the low-pressure die casting process of magnesium wheel hub. The temperature field and velocity field during filling and solidification stages are analyzed; the evolution of temperature distribution and liquid fraction was numerically studied. Then, the potential defects including the gas entrapments in the middle of the spokes, shrinkages between the rim and the spokes are predicted. The cooling performance of mould during casting is also investigated. Via analyzing the shrinkage defects generated under various cooling conditions, the cooling system set in the side mould is found to be more effective for enhancing the cooling capacity at the rim/spoke junction areas. With this cooling system, the hot spots at the junctions are obviously reduced and product quality is improved.