Accuracy of Numerical Methods in Determination of Residual Stresses Due to Cold Expansion in Metallic Materials

Today more than ever, it was tried to reach the optimum usage of materials by applying various methods of manufacturing processes. Increasing the fatigue life of components is one of important aims. All parts of a machine must be connected together for incoming to service. Nonpermanent connections like bolt and nut joints must have hole on both components. Fatigue life was increased if these holes were reinforced by various methods. One of the ways is producing compressive residual stress in near fields of hole by cold expansion (CE) method. In this study the CE process was applied to plate was made from elastic–perfectly plastic material. Residual stresses distributions were obtained by analytical and numerical methods (using finite elements analysis). Results of these methods were compared together for determination the accuracy of numerical methods. In the next step, residual stress distribution due to the CE in real material (aluminum) was determined numerically. Three numerical methods were used: really simulation method (3D plate with punch), 2D and 3D model with internal pressure (using try and error, the amount of pressure that was needed to introduce the same CE ratio was determined) and finally, 2D and 3D model with radial displacement in internal surface of the hole. It was determined that the first and second methods have good agreement with experimental results so can be used for simulation of the CE process.