Nord-Lock Wedge-Locking Washers
Massive components in trains aren’t likely reassembled frequently, and any damage these things might do is likely to be insignificant on the scale of locomotive application.
Bit late to the discussion but we use Nord washers in conjunction with conelock nuts on anything that you really really don’t want coming off. Best example I can think of is turbo manifolds and turbocharger dump pipes.
Note that in both these cases the washer is up against an easily repairable steel surface. In my experience though the Nord will split the moment you loosen it and that minimises damage to the surface. I don’t recall ever seeing anything really chewed up by them.
As for repeat on-off applications they’d probably actually be ok, but between those and the cone lock nuts it can get surprisingly pricey.
Aircraft mechanic here. For seldom-used fasteners like engine mounts, I cannot understand why you wouldn’t just use Loctite or safety wire. They’re very cheap, very easy to use and safety wire has the added advantage that you can just look at it and say “yep, safety still there, hasn’t backed off.” On my bike, I use Loctite on seldom-used bolts and mark the heads with Torque Seal, and the oil filter gets safety wired (this is a streetbike).
Loctite can still vibrate loose and safety wire wont keep a bolt tight.
Just because the bolt is in there, doesn’t mean it’s doing the job it was engineered to do; the stresses on a bolt become very different when the bolt is loosened and the parts it is fastening are allowed to shift.
The washers are actually quite soft. That’s part of how they work. They’re also specifically designed for applications where the fastener would need to ve removed somewhat regularly. Would I use them for engine cases? No. No need. A standard lockwasher, the correct fastener, and a torque wrench are all you need.