Computational Analysis and Validation of Residual Stresses in a Dissimilar Metal Butt Weld
By: Minh Tran Advisors: Professor Michael Hill
External loads are important, often well understood, and taken into account in the design of mechanical or structural components. However, there are other factors that can significantly affect the performance of materials, such as pre-existing defects and residual stresses. Those factors are usually difficult to detect and quantify, and thus they can be easily overlooked or simply ignored in the design phase. This work focuses on the residual stresses due to welding and was developed in the context of research with the nuclear power industry. We begin with an introduction of a weld process model, based on nonlinear finite element computation, to predict residual stresses due to the manufacturing process of a pressurizer surge nozzle, used in the cooling system of pressurized water reactors. In addition to weld residual stress produced in the course of manufacturing, plant components are subject to internal water pressure and elevated temperature during operation. Therefore, we next investigate the changes in weld residual stress state in the presence of internal pressure and temperature at operating conditions. In the end, the purpose of computing residual stress is often to determine its effect on component operability. For that reason, we also conduct fracture mechanics assessment on the total residual stress at operating condition.
It is important to obtain accurate weld residual stress information in order to develop an optimal strategy for plant management. However, there is no established, consensus approach for weld residual stress model validation, which could be used to judge model quality. This work provides technical detail of example approaches for weld residual stress model validation, and applies these approaches to a set of weld residual stress model outputs, that were developed in the context of an industry round robin. The validation metrics for comparisons range from simple (e.g., evaluation of mechanical section forces) to complex (e.g., assessment of predicted crack growth behavior). Applying a range of validation approaches provides information for use within the technical community and to support development of a consensus approach for weld residual stress model validation.
Date(s) - 03/15/2017
10:30 am - 11:30 am
1131 Kemper Hall