Computer-Aided Material Design for Crash Boxes Made of High Manganese Steels

Abstract

During the last decades, high manganese steels (HMnS) were considered as promising materials for crash-relevant automobile components due to their extraordinary energy absorption capability in tensile tests. However, in the case of a crash, the specific energy, absorbed by folding of a crash box, is lower for HMnS as compared to the dual phase steel DP800. This behavior is related to the fact that the crash box hardly takes advantage of the high plastic formability of a recrystallized HMnS during deformation. It was revealed that with the help of an alternative heat treatment after cold rolling, the strength of HMnS could be increased for low strains to achieve a crash behavior comparable to DP800. In this work, a multi-scale finite element simulation approach was used to analyze the crash behavior of different material conditions of an HMnS. The crash behavior was evaluated under consideration of material efficiency and passenger safety criteria to identify the ideal material condition and sheet thickness for crash absorption by folding. The proposed simulation methodology reduces the experimental time and effort for crash box design. As a result of increasing material strength, the simulation exhibits a possible weight reduction of the crash box, due to thickness reduction, up to 35%.

Potential of inverted process-chain development to improve crash box performance

“…By applying the same crush energy, the crushing distance of the crash box decreased almost by 28% due to the strain-hardening engineering. Similar results were reported by Quadfasel et al who also used strain-hardening engineering to enhance the material properties and thus the crash box efficiency [34].…”

“…An increase in component performance can be achieved through either material, process or design techniques [23,26,34]. In most cases, material-technical approaches to enhance the component performance first obtain improved mechanical material properties by means of heat treatment strategies, which then positively influence the component behavior [34]. The mentioned approach would possibly have led to a closer match of the experimental and FEM results of the crash box performance.…”

Physical Metallurgy of High Manganese Steels

“…This Special Issue gathers manuscripts from internationally recognized researchers with stimulating new ideas and original results. It consists of fifteen original research papers, seven contributions focus on steels with manganese content above 12% mass [4][5][6][7][8][9][10], whereas eight deal with alloys having less manganese [11][12][13][14][15][16][17][18].…”

“…The most probable application of HMnS is anticipated to be as sheet products. Therefore, profound understanding of the material behaviour during thermo-mechanical processing is of eminent importance and has been addressed in the contributions by Torganchuk et al [4], Haupt et al [5], Oevermann et al [6], and Quadfasel et al [7]. As has been shown in [4], the combination of severe cold rolling (86% thickness reduction) and annealing promotes very fine-grained HMnS.…”

“…It was found that deep rolling improved the monotonic mechanical properties, whereas the fatigue performance decreased after cryogenic rolling due to the formation of ε-martensite. Finally, Quadfasel et al [7] present a computer-aided design approach for the application of HMnS sheets in automotive crash-boxes. Optimum crash behaviour is evaluated based on a multiscale simulation chain with ab initio calculation of the SFE, crystal-plasticity simulation of the strain-hardening behaviour and finite-element simulation of the crash behaviour.…”