Ls Dyna

This paper presents studies of the numerical prediction of the behaviour of polyurethane (PU) foam filled hat section tubes. Experimental results of the foam-filled single-hat and double-hat components tested in an impact testing machine are described. Consistent experimental load displacement curves were generated. FE analyses using LS-DYNA of the impact behaviours predicted are shown to agree favourably with experimental results. INTRODUCTION Tubular structures of single and double hat sections made of steel are frequently used as automotive body structural components such as front rails and rockers of unitized-body cars. An example is shown in Figure 1. These components absorb significant amounts of impact energy during front collisions and thus are indispensable countermeasures in ensuring vehicle crashworthiness and occupant safety. With the need for higher fuel economy and stringent emission norms, auto manufacturers are looking for means to reduce the vehicle's weight either by employing lighter materials like fiber-reinforced plastics or by decreasing the thickness (gauge) of the vehicle structures or a combination of both. Reducing the gauge leads to structural instability due to early inelastic buckling. This phenomenon of instability evokes the proposition of filling the thin walled tube like structural members with light, crushable fillers. Such members filled with PU-foam (and such other fillers) have increased resistance to local buckling mechanisms and higher strengths as well as energy absorbing capabilities. There has been a continued interest in the study of the axial crush behaviour of thin-walled structural components with box and hat sections through experimental, semi-analytical, empirical, and numerical means. Mahmood and Paluszny [1] presented semi-empirical relations for the prediction of average load-carrying capacities of closed rectangular box sections subjected to progressive local buckling under quasi-static axial compressive loads. Comparisons with experimental results were also given for steel columns with geometric aspect ratios relevant to automotive body applications such as front rails. Simplified theoretical and empirical procedures for predicting the performances of hollow-hat sections were reported in [2-4]. White and Jones [5] carried experimental studies on quasi-static axial crushing of steel tubes of single and double hat-sections. A detailed experimental study on progressive collapse behaviour of thin-walled closed-section structural components made from high-strength steels under quasi-static and impact axial loads was reported by Schneider and Jones [6], who also made a comparison with theoretical formulas which had been used successfully for predicting the behaviour of mild steel thin-walled structures.