Shape Dependence of Bending Fatigue Strength Shown by Actual Stress and Strength Design Criterion Examination

Abstract:

The purpose of this study is to develop a general bending fatigue strength design method that can be applied to various geometries. Considering the conditions for fatigue crack initiation and crack arrest, the bending fatigue strength was evaluated using the actual stress at the critical point where the maximum stress occurs, and the relationship between the bending fatigue strength and the geometry close to the critical point was investigated. The results indicate that the bending fatigue strength evaluated using the actual stress depends on the shape close to the critical point. A higher stress concentration leads to a higher fatigue strength, which is defined as the apparent bending fatigue strength. The apparent bending fatigue strength decreased with a decreasing stress gradient. The lowest value of the apparent bending fatigue strength was observed at a zero stress gradient, which corresponded to the tensile fatigue strength of a smooth test piece. Therefore, the tensile fatigue strength of a smooth material can be used as a criterion for estimating the apparent bending fatigue strength. Moreover, the stresses at the critical point were much larger than the yield stresses of the test pieces, indicating the necessity of considering small-region yields in the evaluation of bending fatigue strength.

• Periodical: Key Engineering Materials (Volume 1014)
• Pages: 41-52
• DOI: https://doi.org/10.4028/p-7UL2eC
• Online since: June 2025
• Authors: Gang Deng*, Shijie Zhu, Yasuhiro Bonkobara
• Keywords: Actual Stress, Bending Fatigue Strength, Small-Region Yield, Stress Gradient, Tensile Fatigue Strength

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