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Burnishing a molydisulfide coating into the thread surfaces of fasteners eliminates the need for binders and vehicles which ensure coverage and retention of the lubricant during fastening. The coating may be applied by any convenient method.
Threaded fasteners used in corrosive environments are plated with electroless nickel and electroplated, over the nickel, with tin. This provides a corrosion-resistant coating for the fasteners.
Releasable pin-type toggle bolt fastener is constructed so that, when positioned in hole, toggle action prevents its removal and locknut anchors it firmly in place. Fastener is easily removed by loosening locknut and retraction of toggle wings.
A description is given of a fastener stretcher used to apply a substantial pure axial tensile force to a structural bolt or similar fastening element. The system is comprised of a pair of telescoping elements, one of which is temporarily secured to the bolt. By spreading the telescoping elements axially, the bolt is tensioned axially to permit a nut or the like to be threaded with a minimum of torque; when the elements are then removed from the bolt, the axial forces on the bolt are taken up by the nut to retain the bolt in its stressed state.
The state-of-the-art of mechanical fasteners is reviewed for 1800 F and above. Some of the problems associated with the use of these fasteners are discussed in view of the projected requirements of the space shuttle for metallic heal shields which would be reusable for 100 cycles of orbit and reentry.
The cold working process of stress coining is used to provide fatigue improvement of fastener holes in aircraft structures. The cold working produces a radial flow of the metal. The residual stresses resulting from stress coining provide protection against fatigue damage by opposing the applied tensile stresses in service at the edge of the fastener hole. However, it is shown in this paper that in addition to the compressive stresses surrounding the stress coined hole, there are tensile stresses that result from the coining operation and that these residual tensile stresses can have a deleterious effect on the stress corrosion susceptibility of the postcoined structure.
Modified shear-loading setup is used to determine allowable shear bending loads on mechanical fasteners. System reduces number of tests required for direct analysis of fasteners to two.
Panels, sheets, doors and other structures could be easily attached to and removed from mating part by proposed new fastener. Fastener is permanently anchored in removable part only. Its protruding end is inserted into a hole in mating part. When wedge pin is screwed tightly closed, segmented collar contracts or expands to release parts or to grip them. Installation has no loose parts, and no rear nut is needed.
Proposed quick-disconnect fastener for two or more parts resists shear loads and torque. Device centers parts to be joined, clamps and tightens them into single unit. Potential applications for removable fastener include holding parts for welding, brazing, soldering, riveting, and gluing. Other possible uses are for attaching removable panels and panels with poor access on one side and plugging leaks in pressure vessels.
Method of fastening road pads on tracked vehicles ensures retaining tabs properly installed and less likely to fail from shock or pad squirming when tracked vehicle turns. No risk squirming of pad might overcome retaining force of rubber encapsulation or teeth of split-collet fastener shred soft-iron projections on pad shell, causing inadvertent release of pad. Rod extending through track shells and tabs on pad shells includes grooved cams to secure pads.
Theoretical basis for design of thermal-stress-free fasteners developed. Two-dimensional analysis defines shapes of interfaces between materials. Design technique determines fastener shapes that maintain tight thermal-stress-free joint while joint undergoes uniform temperature change.
The external tank (ET) intertank structure for the space shuttle, a 27.5 ft diameter 22.5 ft long externally stiffened mechanically fastened skin-stringer-frame structure, was a labor intensitive manual structure built on a modified Saturn tooling position. A new approach was developed based on half-section subassemblies. The heart of this manufacturing approach will be 33 ft high vertical automatic riveting system with a 28 ft rotary positioner coming on-line in mid 1985. The Automatic Riveting System incorporates many of the latest automatic riveting technologies. Key features include: vertical columns with two sets of independently operating CNC drill-riveting heads; capability of drill, insert and upset any one piece fastener up to 3/8 inch diameter including slugs without displacing the workpiece offset bucking ram with programmable rotation and deep retraction; vision system for automatic parts program re-synchronization and part edge margin control; and an automatic rivet selection/handling system.
Quick-connect fastener actuated by simple motion of hexagonal wrench. Enables assembly of truss by heavily gloved technician or by robot. Originally designed for use by Astronaut or robot assembling a truss in outer space, fastener also adapts to various connection applications requiring quick assembly or disassembly.
Threaded halves of metallic collar fit around tapered shank of body of fastener. Retaining ring holds collar on body. Ceramic coat gives fastener its resistance to oxidation. Assembled and disassembled quickly from outside.
Fasteners hold flexible blanket on set of posts on supporting structure. Disk of silicone rubber cast on disk of Mylar, fastened to blanket and press-fit over post to nest securely in groove. No tools needed for installation or removal.
Proposed mechanism placed behind panel fastens panel to, or unfastens it from, underlying structure. Electric motor and gearbox drives bolt to engage or disengage captive floating nut. Used where head at outer end of bolt or other fastener covered with protective outer layer on panel and inner end of bolt inaccessible.
Fasteners made of advanced carbon/carbon material perform well at ambient and high temperatures. Exhibit shear strengths of more than 10 kpsi at room temperature and 13 kpsi at temperature of 2,700 degrees F. However, fasteners exhibited poor tensile strength at room temperature. Best suited to applications in which exposed to shear loads with minimal tension loads. Parts reused after thermal cycling.
This presentation summarizes the Systems Special Investigations Group (SIG) findings from testing and analysis of fastener assemblies used on the Long Duration Exposure Facility (LDEF) structure, the tray mounting clamps, and by the various experimenters. The LDEF deintegration team and several experimenters noted severe fastener damage and hardware removal difficulties during post-flight activities. The System SIG has investigated all reported instances, and in all cases examined to date, the difficulties were attributed to galling during installation or post-flight removal. To date, no evidence of coldwelding was found. Correct selection of materials and lubricants as well as proper mechanical procedures is essential to ensure successful on-orbit or post-flight installation and removal of hardware.