1996 Volume 45 Issue 3 Pages 346-351
In this paper, we present a method for monitoring fatigue damage of steel specimens non-contactly using a laser speckle sensor. This method is based on the phenomenon whereby the intensity distribution of laser speckle changes depending on surface profile change invoked by fatigue damage. Analysis of the laser speckle distribution can be made quantitatively using an image processing system. The distribution of speckle intensity was observed under cyclic tensile load with a constant stress amplitude. The intensity distribution of laser speckle was found to expand with the occurrence of slipbands due to fatigue. The experiment was also made for plate specimens with a circular hole. The result showed that the distribution of laser speckle at the hole edge changes with the number of loading cycles and the detection of fatigue damage is possible in the case that plastic strain is not localized in a very small region.
