二軸バルジ試験による冷延IF鋼板の加工硬化特性の測定と材料モデリング

概要

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Deformation behavior of cold rolled IF steel sheet (SPCE) under biaxial tension has been investigated for large plastic strain range over 0.15. The test material was bent and TIG welded to form a tubular specimen with an inner diameter of 44.6 mm and wall thickness of 0.8mm. Many linear stress paths in the first quadrant of stress space were applied to the tubular specimens using 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 were also performed to 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 were precisely measured and compared with those calculated using selected yield functions. Plastic deformation behavior up to a work equivalent plastic strain of 0.19 was successfully measured and the test material exhibited differential hardening. The Yld2000-2d yield function with an exponent of five most closely predicts the contours of plastic work and the directions of plastic strain rates.