Abstract
It is known that the photoelastic coating method is a powerful technique for the determination of stress or strain of metal surface, but there are some errors due to the thickness of the coat, because the whole coat does not always follow the metal surface. To investigate the following of the coat, using the theory of elasticity we calculate the stress distributions in a beam which is fixed on a uniformly elongated floor by its bottom edge. From the results it is shown that observed fringe order becomes smaller with increase of the thickness than that expected from the true strain of the metal surface and the increase beyond a quarter of its length is of no use to obtain higher fringe order. Considering the above, experimental results must be corrected for the estimation of strain of the metal and the optimum thickness may be taken as about 15% to the length of the coating sticked on the metal surface.
