Dual damage criteria in a crash stop

Abstract

This study proposes a method to apply dual criteria for the assessment of product damage based on the deceleration signal in a crash-stop incident. To evaluate the shock effects, a procedure is proposed to decompose the original crash signal into two components, i.e. an equivalent crash signal and a residual shock signal. The characteristics of crash signals are analysed in both time and frequency domains. It is found that the equivalent crash signal can represent the original crash signal if the dominant frequency (fn) of the product structure is relatively lower than the effective frequency (fs) of the crash signal, i.e. fnfs≤15. Otherwise, the original crash signal should be used in the assessment of product damage if fnfs>15. The dual damage criteria method is proposed by combing the maximum-acceleration vs. velocity-change (Amax-ΔV) diagram and shock response spectrum (SRS), i.e. the former can offer a lower bound of damage boundary on Amax-ΔV diagram while the latter can define an upper bound of damage boundary on SRS graph. The method of dual damage criteria is illustrated numerically using two types of cantilever beams, as an example. The proposed method can be applied with the critical SRS (Sc) method recommended in ASTM D3332-99 for the packaging design and test, and may also be considered in the design and test of other impact energy and shock absorbers in a crash-stop incident.