Figure 1

FCG properties under the absence and presence of H for δ-FG and CG: (a) Relationship between FCG rate, da/dN, as a function of stress intensity factor range, ΔK, obtained by ΔK-increasing and -decreasing tests. (b) Relationship between acceleration rate of FCG, (da/dN)H/(da/dN)Non-H, as a function of loading frequency, f, obtained by ΔK-constant tests. (da/dN)H/(da/dN)Non-H = 1 means no acceleration of FCG by the presence of H.