Tony Posted December 15, 2010 Report Share Posted December 15, 2010 A fault in the casting or impact, the reason i ask is the wheel was not dented, what do you think? Quote Link to comment Share on other sites More sharing options...
Rich Posted December 15, 2010 Report Share Posted December 15, 2010 Runflat tyre...the lack of give in the tyre wall caused the crack? Quote Link to comment Share on other sites More sharing options...
Tony Posted December 15, 2010 Author Report Share Posted December 15, 2010 Non RFT, old Merc wheel. Quote Link to comment Share on other sites More sharing options...
parthiban Posted December 15, 2010 Report Share Posted December 15, 2010 Is it corrosion or is that just on the surface? Quote Link to comment Share on other sites More sharing options...
dazz33 Posted December 16, 2010 Report Share Posted December 16, 2010 I would say road impact BUT the tyre was knackerd also..? BUT could be a defect as it looks like a clean break.? Quote Link to comment Share on other sites More sharing options...
Tango Posted December 16, 2010 Report Share Posted December 16, 2010 Rim flange failure can be due to fatigue initiated from pits at the surface caused by exposure to chlorides (like the rock salt we put on the roads) and propagated as a result of cyclic stress and hoop stress from the loads imposed on the rim from normal use (all influenced by tyre pressure, vehicle weight, cornering loads etc. etc.). Dunno if the Merc wheels are die cast or roll forged? The AMG rims are roll forged. The forged would be more resistant to the failure mode. Quote Link to comment Share on other sites More sharing options...
Tony Posted December 16, 2010 Author Report Share Posted December 16, 2010 Rim flange failure can be due to fatigue initiated from pits at the surface caused by exposure to chlorides (like the rock salt we put on the roads) and propagated as a result of cyclic stress and hoop stress from the loads imposed on the rim from normal use (all influenced by tyre pressure, vehicle weight, cornering loads etc. etc.). Dunno if the Merc wheels are die cast or roll forged? The AMG rims are roll forged. The forged would be more resistant to the failure mode. Nail and head spring to mind... Quote Link to comment Share on other sites More sharing options...
parthiban Posted December 18, 2010 Report Share Posted December 18, 2010 Oh so it was corrosion? That's interesting, always thought that just sits on the surface but it makes sense that it could eat through the wheel. I think only the AMG ones are forged. Quote Link to comment Share on other sites More sharing options...
Sagitar Posted December 18, 2010 Report Share Posted December 18, 2010 Oh so it was corrosion? That's interesting, always thought that just sits on the surface but it makes sense that it could eat through the wheel. I think only the AMG ones are forged. It's not that it eats through the wheel. Any kind of imperfection can act a "stress raiser" i.e. it has the effect of causing a much higher level of localised stress at a particular point. In situations where the load on a component is cycling, as it is a wheel, the raised stress level at the point of imperfection causes fatigue to set in earlier at that point. The crack is initiated because of this fatigue and once it starts it accelerates rapidly to failure. Other factors can give rise to a stress raiser e.g. a groove left by poor machining, or too small a radius at the intersection between two surfaces. Fatigue induced cracking can occur in components that appear, on the face of it, to be adequately strong to support the load that they carry and good design involves the careful avoidance of stress raisers. Quote Link to comment Share on other sites More sharing options...
HighlandPete Posted December 18, 2010 Report Share Posted December 18, 2010 I'll go with stress fatigue, can be high duty cyclic loadings, even without any stress raiser. Could be some age hardening depending on the material. The experience with BMW wheels with RFTs, show rims can crack like that, sometimes several places around the rim, (seen seven cracks on one inner edge) so suggesting loadings are far too high for the expected life cycle. HighlandPete Quote Link to comment Share on other sites More sharing options...
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