A Universal Method for Acquiring the Constitutive Behaviors of API-5 L X90 Welds

The uniform elongation, which is the key factor to the constitutive behavior, is generally calculated by the ConsidSre criterion, i.e., the uniform elongation equates the work-hardening exponent. However, it is found in this study that the widely used ConsidSre criterion is not applicable to metals when the materials are subjected to the maximum load, as the first derivative of the fitted constitutive behavior is not zero which is the basic assumption in ConsidSre criterion. To acquire the whole constitutive behaviors, an accurate and universal method is proposed, based on the work-hardening exponent and yield strength, to calculate the uniform elongation beforehand. With the yield strength obtained via the DIC data, and the work-hardening exponent determined by fitted Ramberg-Osgood model, the uniform elongation can be calculated by the new proposed method. The accuracy of the new method is validated by the conventional load method, indicating that the proposed method is applicable and feasible. With the uniform elongation calculated by the proposed method, the whole constitutive behavior of API 5 L X90 welds can be easily obtained.