Abstract
In this study, the effect of the shape of a notch and a circular hole on the effect of the evaluation of the plane bending fatigue property in Ti-6Al-4V was examined. Furthermore, the fracture mechanism was clarified based on the evaluation of the depth of crack from the surface. Material used in this study was a Ti-6Al-4V alloy. The used specimens are two types: notch (R=42.5mm, R=2.0mm, R=0.7mm) and circular hole (φ=20mm, φ=6mm). The plane bend fatigue testing is performed under the condition of constant displacement. The testing condition is stress ratio R=-1 and frequency 1OHz. Since fatigue test is conducted under constant displacement condition, the maximum load set at the start of the test decreases when fatigue cracking occurs. The stress distribution around the edge of a circular hole and the maximum stress (σmax) in tensile test is obtained by finite element method (FEM). In the circular hole, fatigue strength becomes lower as the diameter of the hole increase. The stress concentration factor obtained by using FEM for is Kt=6.3φ=20mm and for is Kt=3.0 φ=6mm. Therefore, the fatigue strength of the shape of a notch and a circular hole can be organized with its stress concentration factor. And the effect of the shape of a circular hole can be related to not only the maximum stress but also the stress distribution near it..
