Comparative study of small crack growth behavior between specimens with and without machining-induced residual stress of alloy GH4169
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We investigated the small fatigue crack behavior of alloy GH4169 by using single-edge-notch tension specimens. Residual stress introduced by machining process was taken into consideration, and two stress levels were selected. A comparison was made between the experimental results of specimens with and without machining-induced residual stress. The results indicated that fatigue cracks of the two types of specimens initiated from surface inclusions or grain boundaries. For both types of specimens, small cracks grew very slowly when the crack lengths were less than 500 μm. The small crack growth might decelerate and retard temporarily for the existence of grain boundaries. The residual stress effect on crack growth can be identified at σmax = 380 MPa, i.e., compressive residual stress might impede the crack growth. However, this phenomenon was indistinguishable at σmax = 410 MPa.
KeywordsSmall fatigue crack Machining-induced residual stress Crack growth Ni superalloy
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