Biaxial Tensile Test of Cold Rolled IF Steel Sheet for Large Plastic Strain Range

Abstract

Deformation behavior of cold rolled IF steel sheet (SPCE) under biaxial tension has been investigated for large plastic strain range over 15%. The test material was bent and TIG welded to form a tubular specimen with an outer diameter of 46.2 mm and wall thickness of 0.8 mm. The tubular specimens have been subjected to linear stress paths in the first quadrant of stress space with the use of a servo‐controlled tension‐internal pressure testing machine developed by one of the authors [T. Kuwabara, K. Yoshida, K. Narihara, S. Takahashi, Anisotropic plastic deformation of extruded aluminum alloy tube under axial forces and internal pressure, Int. J. Plasticity 21, 101–117 (2005)]. Moreover, biaxial tensile tests using a cruciform specimen have also been carried out to more precisely measure the deformation behavior for a small strain range following initial yielding. True stress‐true plastic strain curves, contours of plastic work in stress space and the directions of plastic strain rates have been measured and compared with those calculated using selected yield functions: the von Mises, Hill’s quadratic and Yld2000‐2d [Barlat, F., Brem, J.C., Yoon, J.W., Chung, K., Dick, R.E., Lege, D.J., Pourboghrat, F., Choi, S.H., Chu, E., Plane stress yield function for aluminum alloy sheets—Part 1: Theory. Int. J. Plasticity 19, 1297–1319 (2003)]. The plastic deformation behavior up to a work equivalent plastic strain of ε0p = 0.19 has been successfully measured. It is found that the test material exhibits differential hardening and that the Yld2000‐2d yield function with an exponent of six most closely predicts the contours of plastic work and the directions of plastic strain rates.