THE ESPI MEASUREMENT OF THE RESIDUAL-STRESS DISTRIBUTION IN CHEMICALLY ETCHED COLD-ROLLED METALLIC SHEETS

A new method for the measurement of residual stresses in sheet materia ls is presented. The method is based upon the measurement of the curva ture resulting from progressive removal of uniform layers from the sur face of the specimen by chemical etching. The curvature is obtained fr om electronic speckle pattern interferograms (ESPI). As an illustratio n, a thin cold-rolled steel sheet was tested. Surface residual stresse s were measured in as-received and heat-treated specimens. Results wer e found to be within the range given by x-ray diffraction measurements and show that annealing is an effective procedure for the reduction o f residual stresses.