Constitutive Relations for Base Metal and Weld Metal of Q355D Steel Considering Post-Necking Effects

Abstract The constitutive relation of steels before necking can be conveniently obtained through tension coupon tests. However, due to the uneven distribution of stress and strain caused by necking, the constitutive relation of steels after necking, determined using the same method, cannot accurately reflect the post-necking behavior of the steels. Different approaches have been proposed for correcting the post-necking constitutive relation of steels. In this research, tension coupon tests were conducted to determine the full-range constitutive relations for the base metal (BM) and weld metal (WM) of Q355D steel. Four approaches proposed in the literature—Bridgman’s formula, the MLR model, the power law tangent method, and the instantaneous area method—were employed to address the post-neck effects and correct the post-necking constitutive relations. The obtained full-range constitutive relations were adopted in finite element simulations of the tension coupon tests on the BM and WM of Q355D steel. The simulation results were compared with the test results to evaluate the effectiveness of the correction approaches and the applicability of the full-range constitutive relations for the BM and WM of Q355D steel.