Effect of Proximity Hole on Induced Residual Stresses during Cold Expansion of Adjacent Holes

Presence of a neighboring hole introduces limits on the level of expansion that can be applied during cold expansion of adjacent holes. Particularly in case of closely spaced holes, it is required to consider the effect of proximity hole in arriving at optimum cold expansion level. The present work is aimed at assessing the effect of neighboring hole on induced residual stresses during cold expansion of adjacent holes through finite element simulation. Four different situations of cold expansion of adjacent holes including a proposed novel approach are considered to obtain detailed insight into the extent of residual stresses induced. The proposed novel approach suggests insertion of a rigid pin into the neighboring hole during cold expansion. This effect has been incorporated during simulation of cold expansion. The simulation results show higher values of residual stresses induced and consequently, larger fatigue life enhancement benefits are expected through the proposed novel approach.