Evolution of a new geometric profile for an ideal tube inversion for crash energy absorption

Abstract

Circular tubes under axial load undergoing deformation through inversion phenamena are referred to as invertubes. Inversion phenomena controls high initial peak crush force which is a fundamental requirement of an energy absorbing structure in road vehicles and helps in achieving nearly 100% stroke and crush force efficiencies. This rare combination of these three features offers a good potential for invertubes to be an ideal choice for impact crash energy absorption. Researchers have always attempted to predict inversion forces in invertubes in terms of geometrical and material parameters through empirical relations; and often ignored the geometric imperfections on plastic deformation and their influence on the inversion process. Limited knowledge exist on inversion using stainless steel SS304 material. In this paper, series of attempts are made to evolve a new invertube profile with SS304 material to achieve desirable inversion charecterisitics for an ideal energy absorption. In this process, the effect of geometric parameters and their imperfections that contribute to effective inversion of invertubes have been studied in detail through FEA and experiments. A new invertube profile has been proposed that addresses anamolies in existing literature and inversion characteristics of this profile have been validated experimentally in a quasi-static environment.