Fatigue strength of weld repair specimens under simulated program loading of an overhead traveling crane

Service stresses acting on an overhead traveling crane were monitored and analyzed by the rain flow method. To assess the effectiveness of various repair schemes for components of aged overhead traveling cranes, weld-repaired gusset specimens, several kinds of plate specimens with cracks repaired by welding, and cover plate specimens were fabricated, and the fatigue strength of the weld-repaired specimens was evaluated under a program loading determined from the monitored service stresses. The fatigue strength of weld-repaired gusset plate specimens was approximately the same as that of uncracked gusset plate specimens, because the fatigue crack always initiated from the weld toe of the as-welded side in both specimens. The fatigue strength of one-surface repaired specimens decreased with an increase in the initial crack length. In case of one-surface repaired specimens with the initial crack length beyond half of the specimen width and one-surface cover plate specimens, the fatigue strength did not satisfy the design requirement. On the other hand, the specimens with cracks repaired completely by welding on both surfaces displayed sufficient fatigue strength to satisfy the requirement. The Fatigue crack growth rate of the weld-repaired gusset specimens under the program loading was correlated with an effective stress intensity factor range, which considered the effect of residual stresses.