Ramp breaks common thread of fastener failures - A special thread form keeps bolts and nuts tight under vibration by attacking the problem from a different angle

摘要

Two conventional methods for securing threaded fasteners against preload loss include locking and single-use drypatch adhesives. But thread adhesives are temperature limited and cumbersome to deal with in production and during maintenance. The reason such measures are needed in the first place is the thread form itself. A standard 60° thread form leaves a gap between the crest of the male and female threads. This makes the nut-bolt assembly susceptible to transverse motion and loosening under vibrational loads. Just the first few threads carry most of the axial load, which raises contact stresses, fatigue, and the probability for shear and thread stripping, especially when bolts thread into soft metals.