Teoretyczna i eksperymentalna analiza wzrostu szczelin zmęczeniowych w obecności spawalniczych naprężeń własnych

The article deals with the effect of welding residual stresses on fatigue crack growth in 18G2AV high strength low alloy steel weldments. Three kinds of flat specimens have been used – unwelded ones, specimens with butt perpendicular welds and specimens with butt longitudinal welds. Residual stress distributions have been measured in both kinds of welded specimens. AH specimens were tested under constant and variable amplitude load with stress ratios R>0. The Forman's law and Wheeler's model of crack retardation were used for theoretical analysis. The theoretical results were more realistic when effective stress ratio R_eff and effective stress intensity range DK_eff compensating for residual stresses had been used. It was found that the tension resisdual stresses increase the fatigue crack growth rate while compresive ones reduce it. The lower was the applied load the higher the residual stress effect. A distribution of residual stress had a significant effect on fatigue crack growth rate and fatigue life of welded specimens. This report presents experimental results and analytical method of fatigue crack growth prediction in steel weldments on the basis of results obtained from parent material.