STEEL GRIPS online - Crash behaviour of various modern steels exposed to high deformation rates

STEEL GRIPS online
ISSN 1866-8453

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Feb 3, 2012

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Till Laumann and Markus Pfestorf:
Crash behaviour of various modern steels exposed to high deformation rates

Hot forming, crash appropriateness, annealing, tailored blanks, evaluation of characteristic values

Besides several other aspects it is an important objective of car manufacturers to develop cars that provide maximum driving pleasure together with highly sophisticated passive and active safety systems. This ambivalent challenge often demands to solve various conflicts of objectives and, thus, requires a well-balanced coordination of engineering and materials science.

The focus of this paper is on the crash behaviour of galvanized 22MnB5 material. This steel is used for press hardening by default and combines superior formability with very high strength values. In addition to the press hardened condition the material is analysed after different subsequent annealing treatments. The annealing treatments were performed to improve the ductility versus brittle material fracture. To evaluate the crash performance the real crash is reenacted. For this purpose, specimens of the altered conditions are deformed by a highly accelerated mass and hereupon compared and evaluated in terms of absorbed energy, maximum deformation and other aspects like wrinkling behaviour. Since analysis of crash worthiness always implies considering the dynamic impact behaviour under high strain rates, this method is a suitable approach to this problem. The different materials are further analysed by means of tensile tests, optical deformation measurement, bending test and microscopy.