Fastener Hole Angularity Test.
BOEING WICHITA CO KS
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This report presents the investigation through tests of the effects which non-perpendicular holes have on single shear lap joint fatigue life. Joints were made from 6Al-4V titanium alloy. Fasteners were 6Al-4V titanium alloy in 14-28 size. Both hex head and 100-degree head fastener were used in holes that ranged up to 5 degrees from normal. Joint specimens were produced in lots of ten. Nine were fatigue tested and one was static tension tested. Fatigue tests involved three different stress levels. Results indicated slanted holes had very little effect on static tensile strength. In fatigue, the direction of hole angularity, with respect to applied load, was a definite factor which influenced fatigue life. Lack of bolt head support allowed bending at the specimen minimum net section. As much as 47 reduction in fatigue life may be realized with holes slanted 2 degrees from normal. A 95 reduction is possible with holes slanted 5 degrees from normal. Thus extra fixturing to obtain superior holes through machine control is advisable in fatigue critical areas.
- Couplers, Fasteners and Joints