Optimization of the Cold Expansion Process for Titanium Holes

Abstract

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.

Cold Working Process on Hard Metal Stacked Assembly

“…During the classic process, plates are expanded individually and the local deformations of the metal plates create a volcano on each face of the coupon. In his works, [8] performed cold working expansion on several similar coupons and the measured heights of such volcanoes were around a tenth of a millimeter. Although the coupons are stacked and strongly clamped in the present work, similar deformations are present, as shown by Fig.…”

Incorporating Asymmetric Hardening Behavior In Modeling The Cold Expansion Process Of Az31B Sheet

“…Due to the surface damage caused by these methods [4], they have been replaced by a more advanced method called split sleeve cold expansion. This method, which consists of pulling a tapered mandrel covered with split sleeve through the hole [6], is now widely used in aerospace industry as the fatigue life improvement technique [7]. From the design point of view, determination of the residual stress due to cold expansion is key to estimation of fatigue life.…”