CHARACTERIZING THE PHYSICS OF TAPER-LOK FASTENER HOLES TO SUPPORT B-1 SUSTAINMENT
Taper-Lok fasteners provide great benefit to fatigue performance but create a complex scenario for analysis to fully account for its effects. The interference due to the oversized tapered fastener introduces tensile hoop stress around the hole and compressive radial stress that combine with applied loading to effectively reduce stress amplitude and improve fatigue performance. The combination of the stress due to interference, applied stress, and the likelihood of plastic deformation near the hole results in a complicated scenario for damage tolerance analysis. The objective of this work was to develop an analytical approach to support explicit incorporation of the physics of a Taper-Lok fastener installation for B-1 critical locations. The work included experimental measurements and finite element predictions of residual stress utilizing manufactured coupons and aircraft excised structure. A comprehensive fatigue crack growth test program was conducted to obtain validation data using coupons representative of wing rear spar and wing carry-through lower cover control points. The analytical approach and validation data developed in this work are discussed in detail.