Abstract
The fatigue crack growth and crack closure behaviors of an explosively bonded stainless clad pressure vessel steel plate (SUS-SPV plate) were studied by using the through thickness crack specimens and the surface crack specimens. The observed behaviors of the fatigue crack growth and crack closure were complicated, mainly due to the influence of the residual stresses which had been introduced in the clad plate through the production process. The shape of the crack was also influenced strongly by the residual stress in the surface crack specimens. The crack was elongated in the thickness direction when the crack was propagated from SUS to SPV, while it was elongated in the surface direction when the crack was propagated from SPV to SUS. The exceptionally high and low values of the aspect ratio, a/c, of the surface crack, the maximum value of 2.2 and the minimum value of 0.35, were observed. The stress intensity factor range, ΔK, was not in good correlation with the crack growth rate for both types of specimens. The effective stress intensity factor range, ΔKeff, was successfully correlated with the crack growth rate for all the specimens tested in this study, including those of the parent materials of the clad plate.
