Experimental investigation of strain rate dependent damage mechanisms in DP1000 automotive steel

Sarath Chandran,Patricia Verleysen,F Gálvez Díaz-Rubio,D.A Cendón Franco

doi:10.1051/epjconf/202125003005

Abstract

Present study aims to investigate the effect of stress state and loading rates on the damage mechanisms in a DP1000 steel using a welldesigned series of experiments. A specimen family comprising of central hole, in-plane shear and plane strain samples is applied to characterise damage under well-controlled stress states. The optimization of the specimen geometries is achieved using finite element simulations. To assess the influence of strain rate, quasi-static, intermediate and dynamic tests are performed on the designed samples. Local strain fields are obtained by digital image correlation. After testing, scanning electron microscopy is employed to systematically analyse the micromechanisms driving the damage in the investigated material. The underlying damage mechanisms are ferrite-martensite interphase debonding, martensite cracking and debonding at ferrite-ferrite grain boundaries. Stress state and strain rate are found to have distinct influences on triggering the underlying damage mechanisms.

Highlights

Over the past decades, the rising demand for light weight structures for enhanced fuel efficiency, concurrently with the goal of achieving efficient passenger safety design in the automotive industry, is met by advanced high strength steels, dual phase (DP) steels [1]
Much of the improvement occurs in the transition to the dynamic loading rates for the tensile specimens, whereas for the SH sample, enhanced strength is achieved even from the intermediate strain rate
With the aim of elucidating the effect of strain rate on the mechanical behaviour and damage mechanisms in a DP1000 steel, lab-scale tests were performed under explicitly defined stress states and deformation rates

Summary

Introduction

The rising demand for light weight structures for enhanced fuel efficiency, concurrently with the goal of achieving efficient passenger safety design in the automotive industry, is met by advanced high strength steels, dual phase (DP) steels [1]. To the intrinsic material aspects such as the morphology, volume fraction and spatial size distribution of the phases, deformation behaviour in DP steels is influenced by strain rate and stress state. The effect of the former aspect has been reasonably wellestablished [2,3,4,5,6], the impact of the latter variables on the micromechanisms of deformation is not well-documented. Present work reports experimental evidence of the influence of strain rate and stress state on the damage characteristics of a DP1000 steel using mechanical tests performed on 3 purpose-developed fracture specimens at three distinct strain rates. After testing, scanning electron microscopy (SEM) is employed to reveal the principle damage modes

Methods

Results

Conclusion