Experimental and Numerical Investigations into the Failure Mechanisms of TRIP700 Steel Sheets

Niloufar Habibi,Ulrich Prahl,Veera Sundararaghavan,Ali Ramazani

doi:10.3390/met8121073

Niloufar Habibi, Ulrich Prahl + Show 2 more

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https://doi.org/10.3390/met8121073

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Abstract

The formability and failure behavior of transformation-induced plasticity (TRIP) steel blanks were investigated through various stress states. The forming limit diagram (FLD) at fracture was constructed both experimentally and numerically. Numerical studies were performed to evaluate the applicability of different damage criteria in predicting the FLD as well as complex cross-die deep drawing process. The fracture surface and numerical results reveal that the material failed in a different mode for different strain path. Therefore, the Tresca model, which is based on shear stress, accurately predicted the conditions where shear had a profound effect on the damage initiation, whereas Situ localized necking criterion could calculate the conditions in which localization was dominant.

Highlights

Transformation-induced-plasticity (TRIP) steel sheets are widely used in automotive structures due to their outstanding mechanical properties, such as the forming potential and high energy absorption [1,2,3,4,5]
Three different damage modelswere considered to predict the formability of TRIP700 steel sheets through various stress states
The simulation results, which were performed according to the experimental tests, show each specimen experienced a specific, almost linear strain path before fracture and the designed specimens were able to cover a wide range of strain paths (Figure 6), from uniaxial tension to equi-biaxial tension

Summary

Introduction

Transformation-induced-plasticity (TRIP) steel sheets are widely used in automotive structures due to their outstanding mechanical properties, such as the forming potential and high energy absorption [1,2,3,4,5]. Forming limit diagram at necking (FLD) is an indispensable tool for evaluating sheet metal formability at the industrial level. This diagram represents the maximum values of major strain–minor strain pairs at the onset of localized necking in a sheet subjected to different proportional linear strain paths. In this way, a boundary is established between strain states that facilitate sheet forming and those that lead the sheets into failure [6,7]. Theoretical prediction methods are considered for calculating and constructing the forming limit diagram for different materials. Bhargava et al [14] applied different failure

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