In order to study the effect of the dissimilar material stack-structure on the surface integrity and fatigue properties of holes

under the stacked condition

ϕ8.36mm holes were prepared by different processes

such as drilling reaming

burnishing

and split sleeve cold expansion (SSCX). The surface morphology

surface roughness

residual stress and microstructure were investigated. Fatigue test and fracture surface analysis were performed. The results show that burnishing forms obvious material pile-up at the end of the interlayer hole and introduces circle-shaped micro-crack around the 7B04–T6 hole

while SSCX imparts micro-crack in the region corresponding to sleeve split. Under fatigue loading conditions in present paper

burnishing increases the fatigue life (99.9% survival rate

95% confidence) of 7B04–T6 and TA15 hole structures by 0.01 times and 0.63 times

and SSCX with interference value of A increases that of 7B04–T6 hole by 3.25 times but reduces that of TA15 holes

while SSCX with interference value of B increases that of 7B04–T6 and TA15 by 18 times and 3.30 times

respectively. The fatigue sources of the three types of hole all originate from the hole wall or corner

and never start from the micro cracks of cold expansion or burnishing