Study On Casting Process Simulation And Fatigue Life Of Vacuum Die Casting Aluminum Alloy Sub-frame

The research on the lightweight and fatigue performance of automobile chassis structure is one of the hotspots both at home and abroad.There are many related literatures,but the literature related to the fatigue life of the car sub-frame does not take into account the effect of the residual stress in the manufacturing process on the fatigue life of the sub-frame.Therefore,this paper designs a suitable pouring system with CAE simulation technology for the aluminum alloy sub-frame of a domestic brand car,which is produced by vacuum die-casting process,and studies the residual stress with CAE simulation technology and bench test.Frame fatigue life.The main work and results are as follows:(1)Unigraphics NX is used to optimize the structure of the original sub-frame according to the installation size,so as to obtain the aluminum alloy sub-frame three-dimensional model which can realize the vacuum die-casting process.It can ensure that the strength and structure size meet the requirements.Sub-frame weight from 14kg to 8.3kg,lightweight effect is obvious.And the design and modeling of the sub-frame were carried out and the casting simulation was carried out by casting simulation software.The casting system was optimized by Unigraphics NX according to the simulation results and the actual production conditions,so as to obtain a reasonable pouring system,exhaust and overflow system.(2)The casting residual stress field of the sub-frame was simulated by ProCAST simulation.The simulation results show that the residual stress is larger than that of the sub-frame,and the residual stress is 83.1 MPa.Two kinds of finite element models considering residual stress and no residual stress are established,and the two models are introduced into HyperMesh for material properties,boundary conditions and load settings.And then the stress distribution is calculated by ABAQUS.The stress distribution in the lateral,longitudinal and vertical conditions of the two models is obtained respectively.It is found that the residual stress of the sub-frame is the largest in the lateral,longitudinal and vertical working conditions The values of 137%,133%and 300%respectively increased.The results show that the residual stress increases the loading stress of the sub-frame.(3)Using the Seeger's Method and the mean stress correction method to obtain the S-N curve of the material,the load stress analysis results of the two models considering the residual stress and the residual stress are introduced into the FE-Safe software for fatigue life simulation.The fatigue life of the sub-frame in the lateral,longitudinal and vertical working conditions is reduced by 48%,71.3%and 32.5%,respectively.The fatigue life of the sub-frame is reduced by 48%,71.3%and 32.5%respectively.The results show that the presence of residual stress significantly reduces the fatigue life of the sub-frame.(4)The bench test and the road test of the sub-frame produced by vacuum die-casting were analyzed.The results show that the fatigue life simulation results considering the residual stress are closer to the bench test results,and the sub-frame meets the actual requirements The Therefore,in the actual vacuum die-casting aluminum sub-frame product structure of the R&D stage need to consider the impact of residual stress on the structure,thus designing the most reasonable sub-frame structure..