In this study, behavior of fatigue crack growth and closure through tensile residual stress field are investigated under random loaing using welded CCT specimens of a structural steel SM50A. Fatigue crack growth tests are performed under constant amplitude loadings and two kinds of pseudo random loadings.
It is found that under constant amplitude loadings the fatigue crack growth rate is well represented by the effective stress intensity factor range ΔKeff even in the residual stress field.
It is found that under pseudo random loading the crack opening point varies from cycle to cycle in one block consisting of 500 cycles and the degree of variation is more significant for the wide band random sequence than for the narrow one. In addition, the crack opening point under random loading is found to be higher than the constant amplitude loading test results corresponding to maximum stress ratio Rmax and maximum stress intensity factor Kmax of the random sequence.