Abstract
This paper presents a method to detect damage of metals with no contact using a laser speckle technique. This method is based on observations of the change of the laser speckle pattern depending on the surface roughness and texture change of the material caused by slip bands due to plastic deformation. The laser speckle pattern was analyzed automatically and quantitatively using an image processing system in this experiment. A new parameter, ck, was derived to statistically express the features of the speckle pattern. It was found that this parameter can express the features of the speckle pattern accurately and has excellent reproducibility. Also, it allows an accurate measurement of plastic strain. The experiment was carried out for cases of both static tensile and fatigue loading using aluminum alloy as the material.
