Thread keeps missions from falling apart

摘要

Extreme shock, g-force, vibration, and temperature cycles assault every in-use jet, rocket, and spacecraft. The mounting of critical aircraft avionics, the clamping of onboard generator cables for continuous power, or the securing of interplanetary satellite instrumentation to these vehicles affects mission success. While the internal and external threads of fasteners often are taken for granted, these are what primarily bind aerospace components together. Traditional methods of preventing joint loosening-such as prevailing torque nuts, deformed threads, nylon rings, and rivets-do not always measure up, especially when reusability and ongo- ing resistance to thermal expansion and contraction are necessary. The heart of the problem is the 60° "vee" thread design of traditional fasteners, which makes them prone to self-loosening rotational movement in high-load and -vibration use. Testing has found the first two threads alone often carry as much as 80% of the load, enough to cause shearing or stripping.