NEW METHOD FOR MEASURING RESIDUAL STRESS FIELD OF COMPOSITE

This paper is based on the one-Iimensional surface grating,which can be formed by means of parallel and equidistant lines that are marked on the specimen surface.The distance between two adjacent marked lines is the nominal grating constant d.When the specimen is irradiated by a laser beam,a clear row of diffraction spots equally spaced along on a straight line is formed.The spacing of spots is related to d,which,under stress,changes and so does the spacing of spots.In measuring the changes in spacing of spots,use is made of charge coupled device,driving circuits,A/D transformation and computer.The authors' apparatus is also equipped with necessary computer software for control and data processing.Thus the authors'apparato s allows high-peed,high-precision and automatic determination of surface deformation and residual stress fields.