Torque-Tension Relationship and Static Preload Loss of High Strength, Heat Resistant, and Corrosion Resistant Aircraft Alloy Fasteners
LOCKHEED-CALIFORNIA CO BURBANK
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This report describes torque-tension and static preload loss tests conducted on high strength, heat resistant, and corrosion resistant fasteners that are currently used or intended for future use in aircraft. The results of this report may be used to determine the installation torque requirements for optimum joint preload. The test data resulting from this program was generated by wrenching the nut and was limited to two installation cycles. The effect of two different added lubricants was determined. These lubricants were MIL-T-5544, a graphite base lubricant, and MIL-L-23398 LAC-C34-1209A, a dry film lubricant. The conclusions of this report are that the installation torque requirements of fasteners vary due to fastener materials, lubricants used, rated strength of the fastener, finishes, and installation cycle number. In addition, each installed fastener is subject to a loss of preload during the first 72 hours after installation this loss may be as much as 11 percent of the initial preload.
- Couplers, Fasteners and Joints