FEM CONSTRAINT

[spedtoe169]

I'm trying to figure out how to constrain a wheel model. I'm only analyzing the wheel center of a 3-piece wheel. It is in NO WAY in contact with the tire. I want to know how I should constrain the hub face and the studs. I realize that the nuts on the studs will be torqued and there will be a compressive load at the lug holes. But I want to know, is a torque about the wheel axis transmitted soley between the hub and the wheel hub face? Or do the studs take some of this load as well.

Thanks!

John

 

[GregLocock]

You are absolutely correct, I was thinking about the oscillating force, not the basic preload. I'm sure that in a correctly designed system the stud never reaches zero tension.

This is at least roughly calculable. Say lateral acceleration is 1g, mass is 400 kg rolling radius is 600 stud pcd is 120, and worst case (for a 4 stud fixing) is that all the cornering load is taken in tension by one stud then it sees a force of 400*10*600/60, that's 40 kN

Now, I'm not at all sure what the preload is, but say the wheelstud has a thread with a root diameter of 10 mm, yield at 500, torqued to maybe half yield, that is a preload of 19 kN.

So, the cornering load is of the same order as the preload, ie it needs a much more careful analysis to get the right answer.

Cheers

Greg Locock

 

[EnglishMuffin]

GregLocock: As you will note from an earlier post, I'm still a little curious as to how far an Automotive company would or should go in catering for people who drive with loose or inadequately torqued wheel nuts, since this will produce a massive reduction in stud fatigue life. I myself am partially in that category, since I have been driving my S10 Blazer for a couple of years with one wheel nut missing from one of the front wheels (5 stud), since it was lost by a guy in a tire changing facility. I have been admonished for my stupidity by friends - but it's just lethargy I'm afraid.
Merry Christmas, which you guys usually celebrate on the beach don't you?

 

[GregLocock]

We do NO formal durability work on cars with loose wheelnuts. In the back of my mind I think we do some sort of check with a missing wheelnut, but certainly not a full durability or anything like that.

Yeah, Chrimbo on the coast this year, 28 degrees C, lots of sunscreen.






Cheers

Greg Locock

 

[EnglishMuffin]

GregLocock: By the way, at the risk of being branded "pedant in chief" I expect what you meant to say in the opening sentence of your last but one post was something to the effect that the joint never loses its preload, rather than "the stud never reaches zero tension".