Monitoring of Surface Fatigue Crack Growth and Crack Tip Closure Behavior by the Ultrasonic Isoscanning Technique : Solid-Mechanics, Strength of Materials

抄録

The ultrasonic isoscanning technique using shear waves is employed to monitor the surface fatigue crack growth under a constant stress intensity factor range. It is shown that this technique has the potential to become an effective tool for the evaluation of quantitative surface fatigue crack growth characteristics. Not only can the three-dimensional crack profile be continuously measured with fairly high accuracy during fatigue crack growth testing, but this study indicates that the crack tip closure can be detected at the maximum depth point and near the surface. The surface regions under plane-stress conditions are closed for a greater portion of the fatigue load cycle than the maximum depth point under a predominantly plane-strain condition. The plane-strain crack tip opening load is smaller than the plane stress crack tip opening load.