Numerical Prediction of Dynamic Progressive Buckling Behaviors of Single-Hat and Double-Hat Steel Components under Axial Loading 2013-01-0458

Hat sections, single and double, made of steel are frequently encountered in automotive body structural components such as front rails, B-Pillar, and rockers of unitized-body cars. These components can play a significant role in terms of impact energy absorption during collisions thereby protecting occupants of vehicles from severe injury. Modern vehicle safety design relies heavily on computer-aided engineering particularly in the form of explicit finite element analysis tools such as LS-DYNA for virtual assessment of crash performance of a vehicle body structure. There is a great need for the analysis-based predictions to yield close correlation with test results which in turn requires well-proven modeling procedures for nonlinear material modeling with strain rate dependence, effective representation of spot welds, sufficiently refined finite element mesh, etc. Although hat sections subject to axial loading have been studied widely in published literature, it is difficult to come across detailed information on modeling that can lead to sound correlation of CAE predictions with experimental results even for quasi-static conditions. In the current study, both single-hat and double-hat components made of mild steel are at first tested under axial loading in a UTM and the resulting load-displacement responses are predicted accurately through explicit finite element analysis carried out with LS-DYNA. Mean loads from theoretical predictions are then compared with the experimentally obtained results. Furthermore, studies are conducted for different impact conditions and the modeling procedures such as for definition of elasto-plastic material behavior are discussed in detail. The simulation-based impact dynamic responses including crash performance parameters such as mean load and total crush are found to compare well with corresponding experimental results. For generality and for relevance to practical impact scenarios, eccentrically loaded double hat-sections are tested and reasonably good numerical predictions of their behaviors are presented, perhaps for the first time in published literature.