This is a clevis made for linking the tie-rods to the steering rack. This part is under dynamic loading and is getting loosened. We tried using jam nuts but it did not work well. Due to loosening the thread came out of the rack and the part fractured maybe due to bending fatigue.
to prevent the nut from unscrewing, you must use either 1) a thread-locking compound (Loctite or equivalent) on the threads during assembly, 2) split lock washers, 3) an aircraft-grade castellated nut-and-safety-wire assembly, or 4) a nut with a nylon insert to prevent unscrewing (Nylock or equivalent).
The problem here is moments of force. Rather than stiffening the fixings, add dampers like rubber washers with steel washers either side of the rubber dampers. This should absorb much of the instantaneous moment forces while providing vibration protection from adjacent mechanisms and fixings.
The fracture is due to strain hardening of the mild steel threaded section. Really what you want is a weaker replacement section attached to the steering rack. The break occurs where the concentration of forces exceeds the elastic modulus of the bolt resulting in what happened. Ideally you want a failure to be gradual so you have warning of imminent fatiguing failure. This would be designing the bent steel section as a thinner and more flexible bit so that it absorbs much of the shock forces at motion.
