Residual Stresses at Girth-Butt Welds in Pipes and Pressure Vessels. Quarterly Progress Report, July 15, 1976--October 15, 1976

摘要

A progress summary is presented for a combined experimental and analytical study to develop mathematical models for predicting residual stresses in girth-butt welds. The program is divided into three tasks, a critical literature review, laboratory tests, and development of analytical models. The literature review has been completed. Specific analytical models for predicting temperature distributions and residual stresses have been identified. Preliminary calculations with the temperature model showed good correlation with experimental data. The mathematical representation for predicting stress distributions in welded joints is in early stages of development. The model recognizes individual weld passes, distortions, and stresses due to each weld pass, temperature dependent material properties, elastic-plastic stress-strain behavior, and elastic stress-strain unloading from an elastic-plastic state of stress. Preliminary checks on the stress analysis model successfully demonstrated its capability to handle unloading. The first welding experiment has been completed. Data are still being obtained from the specimens. Residual strains are obtained by placing gages on the pipe after the test. The gages are cut out and the change in strain is recorded. This strain is attributed to the residual stress in the material. Foil strain gages placed on the pipe prior to welding did not survive the high temperature environment. Plans for future experiments are to use a special high temperature strain gage at selected locations to obtain some information about the strain history during welding. (ERA citation 02:024519)