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Advanced Design Fatigue Resistant Rivetless Nut Plate System
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English
Abstract
This paper discusses an advanced design rivetless nut plate system which overcomes the inherent problems associated with typical riveted and rivetless nut plate configuration used in blind assembly of aerospace structures.
The ForceTec™ (FtCx™) rivetless nut plate system presented utilizes hole cold expansion technology to radially expand a nut retainer into the fastener hole. Torque and push-out resistance are achieved by the resultant high interference fit of the retainer. Residual compressive stresses induced in the metal surrounding the hole during cold expansion and the reduction in applied cyclic stress range, caused by the high interference fitted retainer, significantly improve resistance to fatigue cracking. This system significantly reduces the high stress concentration associated with other methods and has demonstrated superior nut plate qualities with fast, consistent and reliable installation.
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Citation
Reid, L. and Easterbrook, E., "Advanced Design Fatigue Resistant Rivetless Nut Plate System," SAE Technical Paper 941833, 1994, https://doi.org/10.4271/941833.Also In
References
- Military Specification MIL-N-25027F “Nut, Self-Locking, 250 Deg. F, 450 Deg. F, and 800 Deg. F,” February 1994
- Fatigue Technology Inc. Engineering Process Specification FTI 8101C “Cold Expansion of Holes Using the Standard Split Sleeve System ™ (SsCx ™ ) and Countersink Cold Expansion ™ (CsCx ™ ),” July 1994
- Champoux, R.L. Landy, M.A. “Fatigue Life Enhancement and High Interference Bushing Installation Using the ForceMate Bushing Installation Technique,” Fatigue in Mechanically Fastened Composites and Metallic Joints Potter John A. American Society for Testing and Materials Philadelphia 1986 39 52
- Reid, L. Easterbrook, E. T. Rufin, A. C. “Production and Repair of Fastened Joints Incorporating Cold Expansion,” SAE Technical Paper Series 922400 , Aerofast '92 October 1992
- Fatigue Technology Inc. Technical Report #92045-1 “Fatigue Performance Comparison Testing of the ForceTec Rivetless Nut Plate,” February 1992
- Easterbrook, E. T. Maier, M. C. “Automated Split Sleeve Cold Expansion,” SAE Technical Paper Series 931755 , Aerofast '93 September 1993