Analysis Of Thin-walled Structure For Energy Absorption

Thin-walled metal structures have been extensively employed in crashworthiness application because of their high strength-weight ratio, low price and superior energy absorption capability during crashworthiness analysis. This thesis focuses on the improvement of the structural crashworthiness under axial impact. Experimental investigation, theoretical analyses, numerical simulation and optimization are the main research tool adopted. The main works of the dissertation are as follow: 1. The quasi-static and impact test of the thin wall tubes with star-shaped cross sections(S-tube) samples are performed to investigate the deformation mode and the performances of energy absorption and confirm the accuracy of numerical simulation. Compared with the energy absorbing performance of the polygon tube(P-tube), the fold length of S-tube is longer than that of P-tube and the deformation resistance of S-tube is higher than that of P-tube for the increase of corner number.2. A mode classification chart is given based on simulation with tubes of various dimensions. It is found that the slenderness of tube plays an important role in the deformation mode. A theoretical expression of the mean crushing force(m P) and the specific energy absorption(SEA) of S-tube under axial impact is derived based on the Super Folding Element theory. 3. A new multi-walled structure named CSC-tube is performed in this paper. The experiment and simulation results show the fact that the new structure can significantly increase the crashworthiness of the S-tube through the interaction effect between the tubes walls. A preliminary structural optimization is conducted by using surrogate model to obtain the optimal wall thickness distribution of the CSC-tube. 4. Foam with positive and negative Possion’s ratio is represented by the cellular layout based on the hexagonal grid and re-entrant lattice. The simulations of foam-filled single tube and double tube under axial crushing are carried out to explore the effects of Possion’s ratio on structural crashworthiness and the interaction between foam and tube wall. A new foam model of mixed Possion’s ratio(MPR) is proposed, which have the advanta ge of positive and negative Possion’s ratio foam.