MATEC Web Conf.
Volume 80, 2016NUMIFORM 2016: The 12th International Conference on Numerical Methods in Industrial Forming Processes
|Number of page(s)||6|
|Section||MS3: Defects and damage prediction in forming processes|
|Published online||24 October 2016|
Determination of instability of a DP 980 steel sheet under different stress states based on experiment and theoretical models
1 Institute of Metal Research, Chinese Academy of Sciences, 110016 Shenyang, China
2 Fraunhofer Institute for Mechanics of Materials IWM, 79108 Freiburg, Germany
a Corresponding author: firstname.lastname@example.org
It is generally accepted that the formability of sheet metal is limited by the onset of instability which can be described by forming limit diagram (FLD) in ε1-ε2 space. Common tests for FLD data usually cover strain ratio range from uniaxial to equal biaxial stretching, −1/2 ≤ ε2/ε1 ≤ 1. In this paper a new design of cruciform type specimen for uniaxial stretching is proposed to test formability with strain ratios in the range from shear to tension, −1 ≤ ε2/ε1 ≤ −1/2 which can be controlled by the geometry parameters. The forming limit of a DP 980 steel sheet was determined using both conventional method and proposed specimen with strain ratios from −1 ≤ ε2/ε1 ≤ 1. Then the experimental results were drawn in both ε1− ε2 and εeq−σm/σeq spaces, and the predicted results based on Hill, Swift, M-K, and Hora instability models were compared with the experimental ones. The formability features of the studied steel in whole strain ratio range and differences among the investigated theoretical models were finally discussed. The results indicate that the M-K instability model shows better prediction of the studied steel compared to the other models investigated in this research.
© The Authors, published by EDP Sciences, 2016
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