An Overview of Some Current Research on Welding Residual Stresses and Distortion in the U.S. Navy

Abstract : This paper describes some of the current U.S. Navy efforts geared toward managing residual stresses and distortion during weld fabrication. These efforts include model development, model verification, thermo-mechanical and thermo-physical property development, the generation of residual stress measurement data using x-ray and neutron diffraction techniques, the analysis of the effects of residual stresses on fatigue and stress corrosion cracking, and the use of weld residual stresses to achieve desired shapes in part manufacturing. Due to the complexities involved in weld residual stress development, significant emphasis has been placed on modeling. The importance of experimental data for model development and validation has been emphasized. It was shown that there were some differences between FE models and experimental results, but in general both were in good agreement. However, it was also shown that residual stress development is highly dependent upon the details of the fabrication process and the material properties and characteristics. Little difference between thermomechanically coupled and uncoupled FE results were demonstrated, but additional work is necessary since the work presented here did not include phase transformation effects or varying material properties representative of remelted or reheated material. Careful experimental techniques for measuring residual stresses must be employed to obtain reliable neutron diffraction and x-ray diffraction results for comparing to model analysis. It was shown that welding creates a wide variation in material properties, and can therefore significantly affect measurement results. This was attributed to dilution and thermal cycling that occurs during welding. It was also shown that when analyzing x-ray diffraction results, it is important to realize that the technique is a surface analysis method and can therefore be influenced by surface conditions.