Photoviscoplastic Strain Analysis of Surface Coatings by the Scattered-Light Method

A coating method for measuring large surface strains of three-dimensional bodies using the scattered-ligt technique was proposed associated with an investigation of photoviscoplastic bhavior of properly mixed polyester resin. A major advantage of this method is that interference fringes at the boundary between a real specimen and coatings can be observed directly. Two components of shearing strains on the surface of the real specimen in axi-symmetrical torsion problems could be calculated using two kinds of scattered-light fringe patterns obtained by two different incidences of polarized light. For the demonstration of effectiveness of the proposed method, this method was applied to analyses of surface strains of solid and circumferentially notched cylindrical specimens made of aluminum alloy with polyester coatings under torsion. Shearing strains on the surface of solid specimens were estimated, which were well consistent with ones calculated from twisting angles. For the notched specimen, shearing strains on the notch surface were estimated and the distributions were well consistent with FEM analyses