Study On Finite-element Simulation Of Crash-box's Spot Welds And Optimization Of Their Location

With the improvement of people's living standard and domestic road conditions, the number of cars in China is increasing continuously. At the same time, there is a growing trend of vehicle crashes. Based on this background, it's self-evident that the protection of cars and passengers in them is very important. When the cars crash with each other, the failure of car body connections will seriously affect the performance of the vehicle collisions. While the resistance spot welding is the most important car body connection method, so the study on the simulation of spot weld is of momentous significance to improve the simulation accuracy of vehicle crashes.In this paper, the spot welds of the vehicle crash-box is selected as the object of study, and the optimal one was found out according to the research on kinds of spot weld simulation methods. And then, based on the optimal method, the location of spot welds is studied, and the car production cost is cut down by reducing the number of spot welds. The specific study work is summarized as follows:Firstly, the high strength and low strength beam elements are selected to simulate spot welds. The building of simplified model of vehicle energy absorber, meshing and setting of all parameters are done by using the HyperMesh software, and the keyword file which can be used to calculate by LS-DYNA3D is exported. Among the four evaluation parameters of the vehicle crash-box's energy absorbing property, the two models'maximum distortion is the same and the maximum collision force is similar, but the maximum energy absorption and the average collision force are significantly different. So simulation methods of spot welds are of very important significance to the simulation accuracy of vehicle energy absorber.Secondly, the beam with hat section is chose as the study object, and the finite element models using nine finite elements to simulate the spot welds are built with HyperMesh. After the calculation and simulation analysis in ANSYS, considering the three factors including simulation accuracy, modeling workload and the simulation of spot welds fracture, the optimal simulation method of spot welds is determined to be that the single beam elements are used to simulate the spot welds if they may fracture, otherwise the rigid beam elements should be used.Finally, the spot welds are simulated with the rigid beam elements. After the crash-box's requirement of the spot welds' density and the evaluation results of spot welds'location by using the topology optimization technology in OptiStruct are obtained, four new programs of the spot welds'location are determined. By comparing the crash simulation results of four models, the optimal program of spot welds'location is the one of using six spot welds, which not only can meet the demand for absorbing energy but also has the least spot welds.