Research On Crashworthiness And Dynamic Characteristics Of Car Frame Filled With Foam Aluminum

The vehicle frame is the most important bearing and energy-absorbing parts, which crashworthiness and dynamic characteristics is directly related to comfort, ride performance and crash safety of car. In order to further improve the crashworthiness and dynamic characteristic of frame structure, the new type energy-absorption material foam aluminum is considered to fill into the frame structure. Therefore, the foam aluminum is filled into the thin-walled square tube, which is the main energy-absorbing component of automobile frame structure. And square tube filled with foam aluminum is taken as the research object to further research its energy-absorbing and damping performance by using experiment, theoretical analysis and numerical simulation method. Based on the research above, the crashworthiness and dynamic performance of car frame filled with foam aluminum are studied by using finite element numerical simulation method. The main contents and conclusions of this dissertation are as follows:The axial compression and three-point bending performance of square empty tube and square tube filled with foam aluminum are studied by comprehensive using experiment, finite element simulation and theoretical analysis method, respectively. The mechanical behavior and energy absorption property theoretical model of square tube filled with foam aluminum are established under static and dynamic compression and bending. And the results of finite element simulation and theoretical analysis are verified by using experiment results. The results show that the foam aluminum filling can significantly improve the bearing and energy absorption performance of square tube structure under compression and bending deformation. The adhesive connection mode can further improve the bearing capacity of filling structure, but it also make the structure destroyed in a smaller angular easily.The damping properties of empty square tube, two forms of foam aluminum filling square tube (with glue and without glue) are studied by using experiment and finite element simulation method, respectively. And the mechanism of damping is also analyzed. The results show that the experiment and finite element modal analysis results are basically the same. The foam aluminum filling can improve the damping performance of square empty tube. And the adhesive connection mode has a bad influence on the damping performance of square tube filled foam aluminum.By taking a certain type frame structure of pickup truck as a prototype, the frame structure filled with foam aluminum has been designed. And the finite element model of frame filled with foam aluminum is established by using Hypermesh software. Based on the parameters of frontal crash against a rigid wall in C-NCAP, the crash safety of whole vehicle which contains frame filled with foam aluminum is simulated by using LS-DYNA software. The results show that the longitudinal beam filled with foam aluminum can absorb more impact energy than original frame type, and the deformation amplitudes and collision accelerations of filled structure frame are reduced. Thus, the filled structure can improve the crash safety of vehicles. The free and constraint modal of original and foam aluminum filling frame are analyzed by using finite element simulation method. Through the comparison of the modal results of two type structure of frames, it shows that the free and constraint modal dynamic characteristics of frame filled with foam aluminum are better than the original frame structure. Based on the analysis of constraint modal, the vibration responses of original frame and frame filled with foam aluminum are analyzed under the excitations of random road input power spectrum by using finite element analysis. The results show that the resonance frequency of original frame and frame filled with foam aluminum are corresponding to the first and ninth-order natural frequency of its structure. But the resonant response of frame filled with foam aluminum is lower than the original frame. So, the dynamic characteristics of frame can be improved by filling foam aluminum. And it is also an effective method to improve the ride performance of vehicles, which has a broad application prospects.