Crashworthiness Analysis And Structure Optimal Design For Vehicle Frame

More than 50% of the impact energy is absorbed by the frame for those vehicles with frame car body structure during frontal crash. Frame crashworthiness is the foundation of the vehicle crashworthiness. Energy shortage and environmental pollution issues have become increasingly prominent with the growing number of automobiles. Research on lightweighting of vehicle frame has important significance in energy conservation and environmental protection. To avoid the shortcomings of experiential design method brings, the structural topology optimization technique is introduced into frame development design. It can bring greater economic benefits.This paper takes a sport utility vehicle frame as an example. Through meshing the frame CAD model and obtaining the Johnson-Cook constitutive equation of the frame material by experiment, finally the frame finite element model for carsh analysis is established. The shortage of the frame crashworthiness is studied, and then put forward some structure improvement measures, such as extending the former frontal longitudinal beam, bringing in inducing groove, adding reinforcement panel and so on. The deformation is obviously improved and the maximum acceleration is reduced from 8×105mm/s2 to 4×105mm/s2 of the improved frame. The crashworthiness of the improved frame is significantly enhanced.After the preliminary analysis of stiffness and lower modal frequency of the improved frame, we find that the frame bending stiffness and torsion stiffness meet the design requirements, but we also discover the problem that it easily lead to resonance for the frame first order modal frequency is very close to the engine idle speed frequency. An size optimization is conducted with a constraint of meeting the requirements of bending stiffness, torsion stiffness, lower modal frequency and crashworthiness and an objective of minimizing the mass of frame based on sensitivity analysis. The result shows that the total mass of the frame reduced by 7.68%, at the same time the bending stiffness increased by 5.71%, the torsion stiffness increased by 0.79% and the first order modal frequency increased from 24.95Hz to 27.10Hz, it effectively avoid the engine idle speed frequency (25Hz). Single-objective topology optimization under each of the four common load cases is conducted with a constraint of volume fraction and an objective of minimizing the compliance of the frame. To overcome the shortcomings of the objective is too single of single-objective optimization methods and ensure Pareto optimal solution can be obtained, a multi-objective topology optimization based on compromise programming under four load cases is presented at last. The topology optimization results can provide a reference for the development design of the vehicle frame.