Cracking During the Installation of Interference Fit Fasteners and Bucked Rivets in 7050-T7XXX Machined Aluminum Parts

This test program evaluated the effect of the installation of solid rivets and interference fit Hi-Tigue bolts on machined 7050 longerons (HiTigue is a registered trademark of the Hi-Shear Corporation of Torrance, (CA). Two simulated longeron specimens were machined from both 7050-T7451 and 7050-T7651 plate. Titanium Hi-Tigues and solid aluminum and Monel rivets were then installed with a pneumatic riveting hammer in sections of various thicknesses in the four machined longeron specimens. After all fasteners were installed, each fastener was subjected to a simulated mishap by applying the pneumatic riveting hammer to the installed fastener without support from an underlying bucking bar. Dye penetrant inspections to detect cracks were performed after the fastener installations and simulated mishaps. All fasteners were then removed and the open holes subjected to eddy current inspection. Visual observations concerning deformation of the machined longeron specimens during fastener installations and simulated mishaps were recorded. Cracking was noted in 0.063 inch thick longeron sections, compelling additional testing involving Hi-Tigues. Recommendations concerning the use of Hi-Tigues and solid rivets in 7050-T7XXX machined parts were made based on the results of the testing.