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Residual stress release characteristics of hole-drilling determined by in-plane three-directional optical interference moiré

ABSTRACT By adopting a new stress calibration method, a grating rosette moiré interferometry and incremental hole-drilling combined system is developed to determine the magnitud of the residual stress in aluminium plate subjected to a uniform uniaxial tensile load. Performing in-plane three-directional fringe analysis, the optical data contained in the moiré interferograms are converted into values of the strains in three directions corresponding to the grating rosette. The evaluation is carried out through the measurement of the in-plane displacement field in three directions generated by the introduction of the small incremental hole. The in-plane three-directional displacement fields are determined from the calculation of the optical in-plane three-directional phase distribution by means of a phase-shifting method. A new finite element calibration analysis that is general axisymmetric elements instead of 3-D block element and harmonic axisymmetric element is adopted to relate the relieved displacement field to the magnitude of the residual stress. The magnitude of the principal stresses is finally evaluated through a least-squares calculation and is also compared with the stress value applied to the specimen measured with strain gauges.