1994 Volume 43 Issue 489 Pages 696-702
This paper presents a method to measure the plastic strain of steel specimens with no contact using the laser speckle method. This method is based on a phenomenon that the intensity distribution of the laser speckle changes depending on surface profile change occurred by plastic deformation. The intensity distribution of the laser speckle was analyzed quantitatively using an image processing system. The laser speckle pattern and surface profile were observed for specimens of three kinds of steels plastically deformed by static tension. The distribution of the speckle intensity was evaluated after smoothing by calculating correlation function. A new parameter to express the width of the distribution was derived. It was clarified that there is a fixed relation between speckle distribution and the magnitude of plastic strain and it is possible to estimate plastic strain using the speckle distribution. It was also found that the relation between speckle distribution and plastic strain is almost identical for three kinds of steels treated in this experiment.
