ORAL REFERENCE: ICF100377OR HIGH STRAIN RATE BEHAVIOUR OF HIGH STRENGTH STEELS FOR AUTOMOTIVE APPLICATIONS O. Moriau1, P. Verleysen², J. Degrieck² and N. Akdut1 1OCAS N.V., Research Centre of the SIDMAR Group, ARBED Group Flat Rolled Products Division, J.F. Kennedylaan 3, B-9060 Zelzate, Belgium ²Department of Mechanical Construction and Production, University of Ghent, Sint-Piertersnieuwstraat 41, B-9000 Gent, Belgium ABSTRACT The continuous requirement of the automotive industry for increased safety and weight savings related to the reduction of the fuel consumption, results in an increasing application of High Strength Steels (HSS). Currently also austenitic stainless steels are under investigation for structural and safety relevant parts due to their high potential in energy absorption and their high strength. In order to achieve a better performance and accuracy of crash test finite element simulations, the mechanical characteristics at high strain rates of these different steel grades are of great importance. Therefore, the strain rate sensitivity of steel grades like dual phase, micro-alloyed and 301LN stainless steel, produced in the ARBED group, is investigated in a range of strain rates between 10-2s-1 and 1000s-1 using a hydraulic tensile machine and a recently developed impact test-bench based on the split Hopkinson bar method. Special emphasis is addressed to the austenitic stainless steel, which shows a relative low ductility loss at high strain rates and is characterised by a change in strain hardening confirmed by the measurements of the martensite volume fraction. The interaction between strain rate, temperature and strain is discussed in terms of γ→α’ transformation and strengthening behaviour. KEYWORDS Strain rate sensitivity, Hopkinson bar, high strength steels, austenitic stainless steels INTRODUCTION Since weight reduction has become more and more a hot topic in the automotive industry, industrial developments of new steel qualities with excellent deformability at high strength levels are a major concern in most steel industries. Although currently the automotive industry uses stainless steels only in small amounts for applications where corrosion resistance is an issue, austenitic stainless steel grades could challenge lowalloyed HSS grades for car body applications, due to their excellent mechanical properties. First assessments [1-4] have shown that the combination of high strength and good formability of austenitic stainless steels offers a high freedom in design. Due to their high impact energy absorption austenitic stainless steels are very well suited for e.g. safety relevant parts. However, it is essential to make the most efficient use of the available various steel grades in automotive applications to meet the competitive threat from alternative materials.
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