Welding and tig-dressing induced residual stresses - Relaxation and influence on fatigue strength of spectrum loaded weldments

Relaxation of residual stresses by spectrum fatigue loading and their influence on fatigue life have been studied numerically and experimentally for steel weldments. The experiments include spectrum fatigue testing and residual stress measurements by X-ray and neutron diffraction. The numerical studies include detailed stress analysis and modelling of fatigue crack growth. The correlation between experimentally obtained fatigue life and fatigue crack growth calculations are good. This can be attributed to the accurate residual stress information through the thickness, provided by neutron diffraction measurements and accurate initial defect size assumptions used in the calculation. Measurements of residual stress distribution after fatigue loading to certain numbers of cycles show that most of the relaxation of residual stresses occurred within 10% of the total fatigue life obtained with the load spectrum used in the study.