Determination of residual stress by use of phase shifting moiré interferometry and hole-drilling method

A phase-shifting moiré interferometry and hole-drilling combined system was developed to determine residual stresses. The relationship between the 2D displacement data of three points around the drilled hole and the residual stresses relieved by hole-drilling was established. The experimental setup consisted of a four-beam moiré interferometer and a computer-controlled hole-drilling system. Two phase shifters controlled by computer were fixed in two of the four optic paths to directly get the displacement data. With special residual stresses calculation software, the phase distributions of the u and v field obtained by moiré interferometry were quickly converted into values of residual stresses. To analyze the accuracy of this experimental system, an aluminum specimen with a blind hole in the center was real-time tensioned in this system. The displacement field obtained by phase shifting moiré interferometry was compared with the finite element method solution. Good agreement was found with respect to each other. As an application, the in-depth residual stresses of a shot-peened aluminum plate were measured by this method, and possible error sources were discussed.