Abstract
We investigated a method to evaluate fatigue damage and estimate fatigue life using laser without contact. When a low carbon steel is loaded cyclically, slipbands appear on the specimen surface and 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 observing pattern change of diffused light when a laser illuminates the specimen surface. In this study, we observed change of surface and investigated correspondence with diffused light pattern during fatigue loading. We derived experimental equati ons expressing the relation between change of speckle pattern due to loading cycles, stress amplitude and fatigue life. We proposed a method to estimate fatigue life using these relationships.
