An analysis of residual stress patterns resulting from hole expansion in an infinite plate, a thick cylinder, and an asymmetric lug

Residual stresses were induced in three specimen geometries: a quasiinfinite plate, a thick cylinder and an asymmetric lug. In each case, a hole expansion process was used, whereby the bore was expanded into the plastic regime; this in effect left residual compression at the bore and residual tension in the far field. In view of the symmetry, the stress patterns in the quasi-infinite plate were measured by a hole drilling method, using an interferometric moiré method to measure the resulting strain patterns. In the case of the thick cylinder and the asymmetric lug, the residual stresses were evidenced by a dissection method. A comparison with theoretical treatments shows that the theory predicts an approximate upper bound to the actual stress levels in the quasi-infinite plate. In the lug geometry, there was a similar systematic difference between theory and experiment.