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The deformation behavior of mild steels was discussed through analyzing a typical stress-strain curve obtained from standard tension tests. Material parameters were calculated from the stress-strain curve and a power-law model was developed for this typical mild steel. Based on the calculated material parameters, material property change with pre-deformation was studied and new stress-strain curves were developed for this mild steel after different pre-deformation. A rectangular tube model related to different pre-deformation magnitudes was created using LS-DYNA. The deformation behavior of this rectangular tube under four different basic loading conditions - tension, compression, bending, and torsion - was investigated through finite element analyses. The variation of internal energy and reaction force with the magnitude of pre-deformation and subsequent structural deformation was studied.

In response to Federal Motor Vehicle Safety Standards (FMVSS) 201 upper interior head impact protection, development of a suitable countermeasure has become an important aspect. FMVSS 201 safety regulation stipulates that the Head Injury Criterion, HIC (d) should be less than 1000 when a FMH is impacted at a speed of 15 mph. The interior components of a vehicle generally do not generate high HIC (d) numbers by themselves but the steel structures behind them to which they are attached do so. The gap between the interior component and the steel structure makes a provision for the introduction of some countermeasures which can absorb the kinetic energy of the FMH in the form of internal energy so that the acceleration response of the FMH does not generate high HIC (d) and Peak G force. This paper discusses the analysis of different countermeasures using a dynamic finite element tool LS-DYNA for automotive interior components to comply with FMVSS 201 requirements.