X-Ray Diffraction Techniques and Finite Element Modeling to Control Residual Stress in High-Temperature Pressure Vessels

摘要

Manufacturing operations, such as swage autofrettage, shot peening, and overload processes, have been used to impart advantageous residual stresses to improve fatigue life in components used in high-temperature pressure vessels. Both experimental and modeling techniques depend on the geometry and processing history of the component under investigation. This report compares x-ray diffraction residual stress measurements in a swage autofrettage steel cylinder with finite element modeling results of a cylinder with a given bore expansion. The report also examines an analytical model of a cylinder under internal pressure, including both Bauschinger and strain-hardening effects. From a simple swaged cylinder to a complicated perforated cylinder and overstrained and shot- peened multiple-lug breech structure, control of residual stresses through experimental and modeling efforts is vital in the design of pressure vessels. This report discusses the role of slicing operations, surface polishing, surface roughness, and resolution effects in structures that contain high stress gradients.