レーザによる疲労センサを用いた鋼材の疲労寿命評価

抄録

This article describes a method to evaluate fatigue damages and to estimate fatigue lives using laser without contact. In the fatigue of a low carbon steel, slipbands appear on the material surface in the early stage before crack initiation and the slipband density increases and thus the specimen surface changes with progress of fatigue damage. The present method intends to detect the surface change caused by fatigue by observing the pattern change of diffused light when a laser light illuminates the specimen surface. We observed the change of the surface and investigated correlation with diffused light pattern during fatigue loading. Empirical formulae were derived to express the relation between the change of diffusion pattern and loading cycles, stress amplitude and fatigue life. We proposed a method to estimate fatigue life of a steel material using these relationships based on observation of the laser diffusion pattern. The estimated result showed that we can predict the fatigue life at the stage before half of fatigue life with sufficient accuracy.