Creep-fatigue crack growth behaviours of a Ti-6242 alloy, a low carbon steel, a Type 304 stainless steel and Hastelloy X under reversed loading patterns (C-P, C-C, P-P and saw-tooth of slow-fast type) were investigated in air and vacuum environment in the light of fracture mechanics and fractography. The crack growth rate in each of the materials tested was successfully correlated in terms of the cyclic
J integral range Δ
J irrespective of loading patterns. In the region of low growth rate, the crack growth rates of all the materials were about the same for the same value of Δ
J. In the region of high growth rate, on the other hand, the growth rates were somewhat different depending on the creep ductility of material, those with lower ductility giving higher growth rate for the same Δ
J value. Significant difference was not found between the crack growth rates in air and vacuum, and it was consistent with little difference observed between the fracture surface morphologies in these environments. It was confirmed by creep void observation on the cross section of specimens that the difference in fracture morphology between C-C type and C-P type loading was due to the recovery of grain boundary sliding during compression hold in the C-C type loading. An experimental evidence was obtained to suggest that the better correlation in crack growth rate in terms of the separated
J integrals-fatigue and creep
J integrals, which was reported on a low carbon steel, was possibly related to the specimen geometry rather than the creep-fatigue interaction.
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