Crashworthiness Simulation And Optimization Of Functionally Graded Foam-filled Thin-walled Columns Under Oblique Impact Loading

With the development of automobile industry, road accidents have become increasingly frequent, which attract more attention to the vehicle passive safety. Crashworthiness design of the vehicle’s energy absorbing structures such as the front rail, has become a hot topic in the field of automotive passive safety.In this thesis, the failure mode and energy absorbing characteristics of novel functionally graded foam-filled (FGF) thin-walled columns were investigated using finite element analysis (FEA). These columns are potentially used as vehicle front rails under impact loadings. The specific energy absorption (SEA) and the peak crushing force (PCF) were adopted as crashworthiness performance indices. The effects of structural parameters and boundary conditions on the crashworthiness of the columns were analyzed. These parameters and boundary conditions include the graded foam index parameter, the foam density range, the wall thickness, the impact velocity and the added mass. It was found that the FGF column was superior to its counterpart with uniform foam density in terms of SEA and PCF under oblique impact loading. It was also found that the structural parameters interact with each other in affecting the crashworthiness characteristics of the FGF columns. To further explore the relationship among these parameters and their combined effects on the energy absorption capability of the column, multi-objective optimization design (MOD) was carried out for the FGF columns under oblique impact loadings. In the MOD problem, SEA and PCF were selected as the objective functions. The multi-objective particle swarm optimization (MOPSO) algorithm was used to seek the optimal solution sets in the MOD process. Based on the Pareto set, some optimal designs under different boundary conditions were obtained. This research provide some useful information in guiding the crashworthiness design of a vehicle’s front rail, especially for improving the crashworthiness performance of these rails under oblique impact loadings.