FEA torsional rigidity testing setup

[deejay]

Does anyone know if there exists a standard for testing the chassis torsional rigidity by FEA? Ideally I was wanting the boundary conditions and loads for a simulation?

[deejay]

Does anyone know if there exists a standard for testing the chassis torsional rigidity by FEA? Ideally I was wanting the boundary conditions and loads for a simulation?

[Mark Bacchetti]

Cornell University wrote a good paper on this subject. Search for a SAE technical paper on chassis design at sae.org.

Mark
Cal Poly Pomona

[stephen j]

Tortional test is set up with the chassis mounted rigid at the rear, no suspension interference, front tie rail is pivoted at the centre,no suspension interference, tortional twist is calculated from the centre of the front tie rail at a measure of 4000nm dialed for four cylinder enines and 6000nm dialed for six or V8s. the twist has to sustain that weight with a maximum of two mm deflection.

[Denny Trimble]

Stephen,
Where is that procedure from?

Deejay,
The most accurate way is to restrain and load the frame by the hubs, and include suspension links and "dummy shocks". We've had very good success correlating these FEA results to physical testing.

If you try to clamp the frame at the suspension points, and apply a load at the pickups, without a-arms and pushrods installed, the loading will be different.

Since the search feature on this forum is intermittent at best, I'll post another picture of our torsion test rig:

[stephen j]

Denny, this procedure is from the Australian design rules Tech dept. it states that no tortional test is to be taken from any suspension component.So the test would have to be initiated from the outer extremeties of the chassis corners.

[Denny Trimble]

Australian design rules for what series? How many 6-cylinder or 8-cylinder FSAE cars have you seen? I've only seen one 8-cylinder...

It just sounds to me like the procedure you listed is for some production-car based series, and the 2mm deflection limit at 4000 N*m (3000 ft-lb) is arbitrary, maybe a "safety" rule.

Can anybody else confirm that this is in the FSAE-A rules?

[Colin]

We do a torsional test every year to validate our Stressed engine setup and i've never seen this procedure before, in the FSAE-A rules or anywhere else.

[Jarrod]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Tortional test is set up with the chassis mounted rigid at the rear, no suspension interference, front tie rail is pivoted at the centre,no suspension interference, tortional twist is calculated from the centre of the front tie rail at a measure of 4000nm dialed for four cylinder enines and 6000nm dialed for six or V8s. the twist has to sustain that weight with a maximum of two mm deflection </div></BLOCKQUOTE>


that measurement technique is certainly not in the FSAE-A rules, I think it is actually a rule for individually constructed road cars, for roadworthy testing. CAMS (australian motorsport governing body) have similar rules for home-built race cars in some series. It sounds like a simplfied method of testing so that anyone can do it without having to construct proper test rigs. Not really useful if you want proper stiffness results though.

[Z]

"Australian design rules"?

That would be "Australian Design Rules", aka ADR's, aka the bureaucratic bull$#!t that petty-minded, puerile, pencil-heads write to spoil the fun of hard working, honest citizens trying to, ahem, improve their road cars...

Z