Feasibility study of cold expansion processes modelling

A comprehensive review is presented of the cold expansion techniques currently used for the improvement of fatigue strength of fastened joints. Two common practices of generating residual stress fields responsible for increasing fatigue life are cold working of the open hole before fastener installation and interference fit fastener systems. Most of the materials studied were aluminum, and experimental work has shown that the benefits of cold working on fatigue life enhancement were substantial in some cases, particularly in the high cycle fatigue region. The performance of cold working depends on several parameters, the most influential being the material characteristics, degree of cold working, and remote applied stress. Analytical work characterizing cold working in order to establish the residual stress distribution uses several simplified assumptions, and analytical results may sometimes be unrealistic compared to results from experiments or finite element methods. Life prediction methods for cold worked materials, relaxation of the compressive residual stress during cycling, and nondestructive examination methods applied to cold working problems are also summarized.