SBIR Phase II: Blind Fastener Inflation for Structural Joining of Aluminum

Tempress Technologies, Inc, Kent WA

Investigators

Abstract

This Small Business Innovation Research (SBIR) Phase II project continues the development of a hyper-pressure fluid pulse system for installation of blind structural fasteners. Riveting is the preferred method of assembling load-bearing aluminum airframe structures. Upset riveting requires the application of high load to both ends of the rivet using impact or hydraulic pistons. A structural fastener that could be installed from one side of the structure - blind fastening - would simplify aircraft assembly and repair. Existing blind fasteners are expensive, time-consuming and do not match the corrosion and fatigue performance of upset rivets. Phase I of this project demonstrated that a compact, hyper-pressure pulse generator can inflate aluminum alloy rivets with an interference fit and strength approaching conventionally upset rivets. Blind fastening was demonstrated in unsupported aluminum panels. Phase I analysis showed that rivet inflation can be accomplished with a much smaller tool. The Phase II effort will involve the development of a lightweight, hand-held tool with an enhanced trigger mechanism that will provide the pulse control required for reliable fastener installation. The work will continue the development of techniques for inflating rivets with aluminum pins to form a solid, all-aluminum fastener. The objective in Phase II is to meet the performance specifications for a fluid-tight aerospace structural rivet. Airframe assembly represents a major portion of the cost of military and commercial aircraft. The process to be developed will halve the cost of manual airframe fabrication and can be used in an automated flexible-manufacturing environment. There are a variety of other potential applications of hyper-pressure pulse technology including: fastening composite/titanium airframes; automotive aluminum sheet bonding; pulsed-jet peening for stress-relief and forming of aluminum sheet; and research into the behavior of materials under dynamic loading at extreme pressures.