Why Should We Encourage Usage of Interference-Fit Fasteners at Airframe Structural Joints?

It is well established that using interference-fit fasteners will obtain longer fatigue lives to airframe structures, compare to using transition-fit fasteners (or close-tolerance) and certainly clearance-fit fasteners. But, common practical manufacturing considerations, drive to less usage of the interference-fit fasteners (due to various installation difficulties of these fasteners being applied into the corresponding holes in the structure layers). In addition, concerns may be raised whether the fatigue advantage is actually being kept for any practical interference-fit installation method (or even fatigue disadvantage may occur due to installation procedures). It seems that there is lack of information regarding the influence on fatigue lives for the different practical installation methods of the interference-fit fasteners. This study presents testing results supported by analyses, for the influence on fatigue life, of the following two main parameters: (I) The fastener-to-hole fit level. (II) Two different common manufacturing practice for fastener installation methods of: hand plastic hammering and pneumatic steel hammering. The study shows that the fatigue advantage of interference-fit fasteners, is being kept even for the more aggressive installation method. The study results show that whenever fatigue life improvements are needed for structural joints, usage of interference-fit fasteners for these joints, is a good option to achieve it.