Rim design upper limit (steel)

[Sriwardene]

Hello

I am these days busy with designing a wheel using FEA. I use a steel where yield strength of 235 MPa and UTS of 340 MPa.
According to FEA, I see some regions with stresses above 235MPa (somewhere around 240 MPa) and those regions are moved to elastic-plastic region. In rim designs what is the strength limit usually take into account at design stage? Yield strength of 235MPa at 0 plastic strain or UTS of 340 MPa at non zero plastic strain?

Sriwardene

 

[loki3000]

http://www.lotustalk.com/forums/att...us-photoblog-4-broken-rota-wheel_thumb-1-.jpg

something to consider

 

[TVP]

Contemporary steel wheels use grades with considerably higher strength than what you are considering:

http://www.autosteel.org/~/media/Files/Autosteel/Programs/Wheels/wheels_brochure.pdf

http://www.nssmc.com/en/tech/report/sm/pdf/1b017001.pdf

http://www.prnewswire.com/news-rele...hare-in-automotive-steel-wheels-74249947.html

http://www.gruppofrattura.it/ocs/index.php/ICF/ICF10/paper/viewFile/4661/6668

 

[JayMaechtlen]

well, that link Loki posted is pretty scary!


Jay Maechtlen

http://www.laserpubs.com/techcomm

 

[loki3000]

the point is that i wouldn't even consider going anywhere near the yield stress.

Yield strength of 235MPa at 0 plastic strain or UTS of 340 MPa at non zero plastic strain?

 

[GregLocock]

Um, steel wheels are designed to function beyond yield. When you hit a pothole you want a wheel that bends and remains inflated.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[Tmoose]

yield while cornering might be fun.

start with this -

http://www.halfahemi.com/pics/dragneons/MVC-010S.JPG

2 laps later end up with the 1950s un-wide track look -

http://www.misterw.com/Oldsmobile/58Olds02.jpg

http://www.misterw.com/Oldsmobile/58Oldsmobile05.jpg

 

[tbuelna]

It is not correct to state that steel wheels (or wheels made of any material) are designed to "function" beyond the yield point of the material. As with the design of many other safety critical automotive components, the wheel is designed such that it will not suffer a fracture failure under certain crash or impact situations. But it is acceptable for the wheel to plastically deform. After an impact that deforms the wheel it is assumed that the wheel would be replaced. Thus a deformed wheel would not be expected to "function" after such an event.

 

[GregLocock]

Well, it goes round and it maintains pressure. Whether that is functioning or not depends on who writes the spec. In our book, if you can drive it to the workshop it is still functioning. More to the point it is a design load case that is part of the design of the wheel, and I can assure you that wheels that do not perform acceptably in this (a) cause customer concerns (b) cause warranty and (c) get redesigned until they do pass. BTDT got the T shirt. Alloy wheels are much harder to design for the same test.


Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[EdStainless]

In modern steel wheels you have the very high strength alloys and the cold work put in during forming.
You need to preserve enough ductility for some damage tolerance (fail gracefully).
I was shopping for new wheels recently, and found that steel ones were both stronger and lighter than Al ones that I could buy.
I have seen racing Mg wheels come apart in use. Very not fun.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[Tekton]

When working in Ghana during the 70's I was initially surprised that our fleet of 6 Peugeot 504's often returned to base with wheel rims sufficiently buckled they would have lost air if not shod with tubed radials

Careful examination of the suspension showed no ill affects whatsoever other than occasionally defective "o" rings in the repairable shocks

Clearly those wily French Engineers knew a thing or two about pot holed African roads, and designed the rims to serve as a "mechanical fuse"

Removing the tyre, belting the rims "straight" with a solid rubber mallet, and rebuilding the shock with new "o" rings used to take less than an hour

Of course, we sometimes held the vehicle for a day or two for disciplinary reasons, but one hour's labour and less than 5 bucks worth of "o" rings and oil was a damned economical fix

Keeping our 4 dozen GMC 3/4 ton pickups running however was far more ardurous

Tekton