Variable material property method in the analysis of cold-worked fastener holes

Based on a general axisymmetric method of elastic-plastic analysis presente d by Jahed and Dubey, elastic-plastic boundaries and residual stress fields induced by cold expansion of fastener holes is predicted. The method uses a linear elastic solution to construct an elastic-plastic solution. The mat erial parameters are treated as field variables and their spatial distribut ions are obtained as part of the solution. This method uses the actual load ing-unloading behaviour of the material and therefore is capable of predict ing an accurate residual stress field. Results obtained here are compared w ith available experimental and finite element results. The agreement of the results with experimental measurements is very good. It is shown that empl oyment of the actual unloading material curve can make a significant change in residual field prediction.