Thermal- stress-free fasteners for joining orthotropic materials Several aspects of the application of high performance corrosion resistant fasteners are discussed including galvanic compatibility and torque-tension relationships. Mechanical properties and chemical compositions are included for the fasteners discussed. Case histories are presented to illustrate the problems which can arise when material selection is made without proper regard for the environmental conditions. A discussion of fastener stress corrosion failures is presented including a review of the history and a description of the mechanism. The fasteners are unique in that they provide a combination of high strength and immunity to stress corrosion cracking not previously attainable. Most of the fasteners utilize cold worked and aged materials to achieve the desired properties. The materials discussed are mainly A-286, Inconel 718, MP35N and MP159. Exposure to accelerated weathering did not impair their performance.Ī family of high performance aerospace fasteners made from corrosion resistant alloys for use in applications where corrosion and stress-corrosion cracking are of major concern are discussed. The test results show these fasteners to have strength characteristics suitable for light structural applications. The effects of variations in hole size, grip length and sheet thickness on strength properties of the fastener were determined. Results of tensile, shear, fatigue and accelerated weathering tests are presented for the ram fastener, a reusable, single unit blind rivet. The Alcoa ram fastener: A reusable blind rivet The fastener is capable of joining materials together from only one side with substantial strength in tension and shear over many resue attachment cycles, with no special operations on the main assembly parts other than the tapering of the back end of the insertion hole. Reversing the direction of the pin withdraws the cone from the collar, and allows the tangs to resume their contracted configuration without withdrawing the fastener from the insertion hole. Turning the pin in one direction draws the cone into the collar, deforming the tangs radially outward to mate with tapered back-tapered hold in the workpiece, thus fastening the two pieces together. The fastener is set by inserting it through aligned holes in the workpieces to be joined. The cone cooperates within a slotted collar end which has a number of tangs on a cylindrical body. A one piece reusable fastener capable of joining materials together from one side ( blind backside) comprises a screw driven pin ending in a wedge-shaped expander cone.
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