Method and apparatus for preloading a joint

摘要

The invention disclosed herein relates to a fastener assembly and method of using same to preload a joint including a plurality of adjacent workpieces having aligned openings formed therein. The fastener assembly includes a pin member having an enlarged head and a shank located within the aligned openings in the workpieces and further includes a collar member having a deformable outer portion and a relatively hard inner portion located about a portion of the shank such that the inner portion is directly adjacent the shank portion. Also formed on the shank is a thread configuration adapted to cooperate with a complimentary thread configuration for snugging the workpieces together with a relatively light preload. After the joint has been snugged together, the collar member is crimped causing axial flow of material in the outer portion which reacts to stretch the pin member and induce a desired preload in the joint. Radial flow of the material in the outer portion is resisted by the hardened inner portion whereby the collar member does not flow into engagement with the shank portion of the pin member.