A Method for Predicting the Effects of Specimen Geometry and Loading Condition on Fatigue Strength

• Main Authors: Chengqi Sun, Qingyuan Song
• Format: Article
• Language: English
• Published: MDPI AG 2018-10-01
• Series: Metals
• Subjects: notch effect; size effect; loading condition; fatigue strength; control volume; titanium alloy
• Online Access: http://www.mdpi.com/2075-4701/8/10/811

Specimen geometry and loading condition usually have a great influence on the fatigue strength of metallic materials, which is an important issue in evaluating the reliability of component parts. In this paper, a rotating bending fatigue test is performed at first on an hourglass specimen and a notch specimen of a high strength titanium alloy. Experimental results indicate that, in terms of local stress, the notch specimen endures higher fatigue strength in comparison with the hourglass specimen due to its relatively smaller control volume. Then, a probabilistic control volume method is proposed for correlating the effects of specimen geometry and loading condition on the fatigue strength based on Weibull distribution and the concept of control volume. A simple formula is obtained for the fatigue strength in relation to control volumes, in which the parameter is the shape parameter of Weibull distribution of fatigue strength. The predicted results are in good agreement with the present experimental data for high strength titanium alloy and the data for the high strength steel and the full scale EA4T axle in the literature.