A FINITE-ELEMENT SIMULATION OF THE COLD-WORKING PROCESS FOR FASTENER HOLES

Two-dimensional axisymmetric finite element simulations have been cond ucted for the cold working of a fastener hole in an aluminium plate. T he simulation models the actual cold working process where an oversize mandrel is pulled through the fastener hole. The results of the simul ation are compared with a simplified finite element model where the co ld working process is reduced to applying a uniform radial expansion t o the hole edge. It is shown that substantial differences exist betwee n the finite element simulations; specifically, the simulation of the actual process shows tensile residual radial stresses on the surface o f the plate after cold working whereas the simplified simulation shows only compressive ones. Further comparisons are made for the axial def ormation of the plate by using the results of an experimental measurem ent of the surface profile around a cold worked hole. There is good ag reement between the finite element and experimental results. The resul ts of this work show that accurate simulations of cold working are nec essary if predicted residual stresses are to be used to assess fatigue life.