Effects of compressive residual stress on bending propagation behaviour of fatigue crack

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Testing for bending fatigue crack propagation under mixed-mode condition was carried out using fatigue and annealed slant pre-cracks with different slant angles, β, defined as the angle between loading and crack directions in a rectangular plate. As a result, bending fatigue crack from the fatigue pre-crack with β=45 deg propagated under mixed-mode condition with mode I and II stress intensity factors K_{I} and K_{II} , while bending fatigue cracks from the fatigue pre-crack of β=60 deg and from the annealed pre-cracks with both slant angles of β=60 deg and β=45 deg propagated under mode I crack behavior. Furthermore, the estimated fracture angles calculated by maximum tangential criterion using the stress intensity factors, K_{I} and K_{II} , are in good agreement with the measurement ones except the fatigue pre-crack of β=45 deg at the initial premium propagation. That is to say fatigue crack propagation behavior was effected by compressive residual stress around pre-crack while the slant angle β is smaller (such asβ=45 deg in this study). But the effect was disappeared if β became bigger (such as β= 60 deg.).