Wear Resistance Design And Influence Of Cast Defects Of Ti-alloy Piston

With the improvement of the strengthening degree of the internal combustion engine, the piston is required to have higher bearing capacity under high temperature, so it is necessary to find new materials to satisfy the strengthening working condition. Titanium alloy, as a new kind of material, is of higher strength-to-weight ratio, better performance under high temperature, and lower thermal conductivity etc. compared with traditional piston material and with a grander application prospect. But titanium alloy shows bad wear resistance and cast defects such as shingkage and inclusion, which lead to its limited application.In order to solve the key technical problems which restrict the application of the titanium alloy on the piston, the wear resistance scheme of the ti-alloy piston was determined and the influence of the cast defect on the strength of the piston was evaluated based on experimental research and simulation analysis. The issue was illustrated in the following three aspects:First, a new style of Ti-alloy piston was designed considering its material characteristics and processing technology. The performance simulation software was used to determine boundary conditions in disel engine piston finite element analysis and Abaqus was applied to conduct simulation analysis on the temperature field, stress field and defoemation conditions of the piston. The result shows that the head of the ti-alloy piston can insulate most of the heat, so there is a big difference between the head and the skirt in temperature. The whole piston exhibits sound strength and little deformation.According to the bad wear resistance of Ti-alloy, the wear resistance scheme of the ti-alloy piston was designed. By checking the wear life of the ring groove, ECC coating was found to be adequate. Chose SPCC to be the material of the piston bush and the magnitude of interference between the piston and the bush was to be determined to be 0.1mm by simulation analysis. To enhance the wearing capacity of the piston skirt, molybdenum disulfide was chosen to be plated upon ECC coating. The cylinder clearance and the piston profile were designed considering the deformation of the piston.Based on the RVE finite element model created by a microstructure photo, the influence of cast defects on the Ti-alloy piston was analysed by micro-mechanics FEM and the simulation results turned out to be closed to the test data. It is found in micro stress field and strain field that the matrix around defects is easily to become invalid because of its high stess. To check the load states of some key parts of piston, the stress fields of the pistons with defect was calculated. The results show that the defects around the pinhole and the neck of inner cavity may increase the stress of matrix near them, while the defect part near the piston throat has less influence on stress of the piston.