Optimization of the Cold Expansion Process for Titanium Holes

Cold expansion of metallic holes is widely used in the aerospace industry for improving the fatigue performance of mechanical assemblies. To increase the efficiency of the process, it is worth considering the possibility of carrying out the expansion twice in succession in the same hole. This paper discusses the consequences of such an operation on a single titanium hole through a numerical and experimental study. More precisely, numerical modeling is developed in order to simulate cases where the expansion is carried out twice: in the same direction and in opposite directions. The residual fields are analyzed and the results compared with experimental results using incremental hole-drilling technique. Results show that double expansion may have a very positive impact on the homogeneity of the compressive fields.