Evaluation of nonuniform residual stress using blind-hole drilling technique

The blind-hole drilling, a semi-destructive method, is used for evaluation of nonuniform residual stress in a structure. The hole drilling method can assess the residual stress that is either uniform or varying with depth. The relieved strains are measured at the end of the drilling operation for the stress that is uniform, while for the stress that is nonuniform with depth, an incremental technique is used. The relieved strains are measured during a series of small hole-depth increments. The constants relating the principal stresses to the measured strains are introduced using a calibration experiment. The rosette along with the structural material and the hole drilling system was calibrated as per ASTM E 837, ensuring that the hole geometry, the hole diameter, and depth are acceptable for the stress measurement.