Is this a simple fatigue failure?
Discussion
It looks unlike torsion fatigue failures I've seen. It looks as if each spline has separated from it's neighbour due to deep radial cracks, and then the whole thing has twisted quite a long way before it failed. It's hard to tell from the picture, but the splines have all twisted through about 20 degrees close to the fracture. It seems that the bar has been taken well past the yield point, but is this because it was weakened by fatigue cracks first?
yes I know its not helped with the question 
It's a half shaft.
I've broken a few in the past, and they all failed in a similar way with a notch round the outside that had clearly been developing for some time before the core finally fails. This one is completely different, the bar has a couple of dozen cracks that go from the splines right into the core, separating the bar into a couple of dozen thin strips, which have started to twist around each other before snapping. There's nothing on the exposed face to show a progressive failure, although I guess those deep radial cracks occurred gradually.
I've broken a few in the past, and they all failed in a similar way with a notch round the outside that had clearly been developing for some time before the core finally fails. This one is completely different, the bar has a couple of dozen cracks that go from the splines right into the core, separating the bar into a couple of dozen thin strips, which have started to twist around each other before snapping. There's nothing on the exposed face to show a progressive failure, although I guess those deep radial cracks occurred gradually.
Edited by GreenV8S on Tuesday 13th October 12:44
stevieturbo said:
Dont see why not.
I can't imagine shot peening after the splines are ground in being feasible, even if it was it would deform the surface so the splines are no longer accurate? On the other hand shot peening before grinding the splines would only affect the surface, so no effect on the base of the splines where the failures occur. That's just my guess from looking at it, no idea whether it's possible in practice.GreenV8S said:
stevieturbo said:
Dont see why not.
I can't imagine shot peening after the splines are ground in being feasible, even if it was it would deform the surface so the splines are no longer accurate? On the other hand shot peening before grinding the splines would only affect the surface, so no effect on the base of the splines where the failures occur. That's just my guess from looking at it, no idea whether it's possible in practice.
Might be posible to barrel the splines so they are more evenly loaded end to end? Have all the failure occurred at the same place axially?
stevieturbo said:
Cheaper to buy stronger once...then many sets of cheaper.
Or you could cut your axle tubes and weld larger outer ends on etc
I thought I was 'buying once' last time, and to be fair they did last 8 years and about 80,000 miles. I hadn't realised how long ago they were done, I can't really complain.Or you could cut your axle tubes and weld larger outer ends on etc
It's an independent back end so no axle tube, but I do wonder whether there's room to squeeze a bigger CV at the outboard end. It's only a 102mm lobro at the moment, which restricts the shaft size I can use.
So what actually broke ?
The CV stub, inner diff stub, or the shaft itself ?
There are places that will make anything uprated in a much stronger material....at a price of course.
Im sure GKN could do it, Driveshaft shop in the US, or there are a couple of Czech comapnies that arent overly expensive.
The CV stub, inner diff stub, or the shaft itself ?
There are places that will make anything uprated in a much stronger material....at a price of course.
Im sure GKN could do it, Driveshaft shop in the US, or there are a couple of Czech comapnies that arent overly expensive.
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