Residual Stress Characterization in Orthotropic Plate by Combining Hole-drilling Method and Speckle Interferometry

Novel method for a determination of residual stresses in orthotropic composite plates based on local displacement measurements by electronic speckle-pattern interferometry is developed and verified. The values of hole diameter increments in principal residual stress directions serves as initial experimental deformation. The technique is based on analytical solution of S.G. Lekhnitsky, which describes a stress concentration along the edge of central open hole in rectangular orthotropic plate under one-axis tension in arbitrary direction. A situation when principal directions of residual stresses coincide with principal axes of anisotropy is considered. It is shown that required relations, which connect initial experimental data with residual stress components, are unequivocally solution of the properly posed inverse problem. An availability of interference fringe patterns, a quality of which is high enough for reliable recognising of fringe orders at the hole edge immediately, is the essential experimental foundation of the approach developed.