An experimental investigation on the axial crush of a thin-walled, stainless steel box component.

摘要

Axial crush is a structural engineering response that for thin-walled, ductile metal alloy components, can provide controlled and reliable energy absorption required for automotive crashworthiness. An experimental investigation on quasi-static (20°C) axial crush was performed using thin-walled, commercially-produced, welded AISI 304 stainless steel box components. Control methods including tube end constraints (removable, grooved caps) and collapse initiators (shallow groove patterns in tube sidewalls) were developed to ensure a single axial crush response mode, i.e. fold formation process and axial load-axial displacement curve shape; and a specific initial collapse location for all specimens. The experimental program consisted of two studies. The first was a progressive axial crush study in which nine specimens with "constant" geometry, alloy composition and microstructure were axially compressed to different, predetermined displacements. The goals of this study were to demonstrate the ability to control axial crush mode and to study the fold formation process (deformation and material performance). Consistent fold appearance and load-displacement curve shape matches indicated that the specimens had undergone the same axial crush mode response. Very good agreement was obtained for crush characteristic values. In the first cycle of the secondary folding phase, the percent differences (average value basis) were less than 6% for minimum loads, 3% for maximum loads, and 3% for energy absorption. In the second study, for "constant" geometry and axial crush mode, the same experimental methodology as in the first study was used to investigate the effect of alloy composition and microstructure. Differences in composition and microstructural features, mainly significantly smaller grains, resulted in increased values for major crush characteristics. These included minimum increases in load magnitude of 8% for minimum loads and 12% for maximum loads and an 18% increase in energy absorption for secondary folding phase cycles. Overall, results showed that simple techniques can be used to control the axial crush mode of a commercially-produced product form and that, if an axial crush component's structural engineering response is controlled, material behavior can be isolated and alloy composition and microstructure can be modified to study and enhance energy absorption performance.