ANALYTICAL AND FINITE-ELEMENT PREDICTIONS OF RESIDUAL-STRESSES IN COLD-WORKED FASTENER HOLES

Two-dimensional finite element (FE) studies, for plane stress, plane s train and axisymmetric conditions, were conducted to simulate 4 per ce nt cold working of a 6.35 mm diameter hole in a 6 mm thick plate of 20 24 T351 aluminium alloy. The simulations were used to assess the influ ence of strain hardening, the role of reversed yielding and through-th ickness residual stress distributions. Experiments were also conducted to determine the tensile and compressive stress-strain response of th e aluminium alloy, revealing a pronounced Bauschinger effect and non-l inear strain hardening in compression. The FE simulations and results from several earlier analytical models were compared and substantial d ifferences found in the region of reversed yielding. Approximations us ed to model the compressive deformation behaviour of the material over estimate the compressive residual stresses at the hole edge. From the axisymmetric FE model a residual stress gradient through the plate thi ckness was found. The plane stress and plane strain assumptions used i n the earlier analytical models did not satisfactorily approximate the three-dimensional residual stress fields obtained from the FE simulat ions.