Papers by Author: Yuan Biao Wu

Abstract: Due to the flow behavior of molten metal is affected by the back pressure of mold residual air in high pressure die casting (HPDC) process, the back pressure conditions should be considered in order to simulate the HPDC process precisely. In this study, an aluminum colander of automobile’s filling process in HPDC was calculated by combining the back pressure conditions. The optimized schemes were given by considering the simulation results. Both initial and optimized schemes simulation results were compared with actual parts. The contribution of gas porosity between simulation and actual part were in agreement when back pressure conditions were applied. The local back pressure can be controlled by coordinating the position of the vents. Therefore the flow behavior of molten metal can be changed and the porosity defects can be fixed.

Abstract: The quality of the green and the shaping efficiency are affected by the mold structure during the course of powder injection molding (PIM). Based on the numerical simulation, the mathematic model for the optimal design of the gating and runner system in PIM mould is constructed. The method is testified by the Moldflow software and the experiment. From the result, it is suggested that the clamp force and the shape cycle are clearly decreased, the green is densified and the samples’ density error of the green is decreased after the optimal design of the mold structure. Furthermore, the number of trial mold is reduced and the shape efficiency is improved.

Abstract: In this paper, based on the CAE technology for MIM and fractional factorial design method, the simulation for the filling process was executed in different process conditions by the Moldflow software. And then it was realized that the extent of the effects of the single factor and pairwise interaction between the process parameters on quality of green parts were forecasted. According to that, the relationships of pressure, velocity and time and their optimal combination were researched by the experiments using a FC-80 plastic-Injection-Moulding machine. The experimental results suggested that the pressure, velocity and time have a obvious pairwise interaction which can have more effect on the product than single factor. It was shown that there was a good consistency between the numerical simulation and experiment. The CAE technique and the experiments are combined to optimize the process conditions and improve the part quality automatically by using smaller number of experiments.

Abstract: Conventional powder metallurgy processing can produce copper green compacts with density less than 8.3 g/cm3 (a relative density of 93%). Performances of these conventionally compacted materials are substantially lower than their full density counterparts. Warm compaction, which is a simple and economical forming process to prepare high density powder metallurgy parts or materials, was employed to develop a Ti3SiC2 particulate reinforced copper matrix composite with high density, high electrical conductivity and high strength. In order to clarify the warm compaction behaviors of copper powder and to optimize the warm compaction parameters, effects of lubricant concentration and compaction pressure on the green density of the copper compacts were studied. Copper compact with a green density of 8.57 g/cm3 can be obtained by compacting Cu powder with a pressure of 700 MPa at 145°C. After sintered at 1000°C under cracked ammonia atmosphere for 60 minutes, density of the sintered compact reached 8.83 g/cm3 (a relative density of 98.6%). Based on these fabrication parameters a Ti3SiC2 particulate reinforced copper matrix composite was prepared. Its density, electrical conductivity, ultimate tensile strength, elongation percentage and tribological behaviors were studied.