Torsional rigidity of 6061-T6 aluminum of varying thickness?

[Sam_Sung]

I'm here because I'm debating the purchase of a 1/4" thick 6061-t6 aluminum chassis reinforcement plate for a 3000# track car, versus one that is 3/8" thick. This is a chassis plate that runs below the length of the driveshaft and helps tie the left/right sides of the car together. Let's say the plate is 4 feet long and 1 foot wide.

The question isn't which is more torsionally rigid, the question is which is most effective in the real-world?

Ie. Let's say both are over-engineered and can withstand forces beyond what the car's shocks/springs/tire grip could ever handle. In this case, there's no added benefit to getting the 3/8" thick plate if the 1/4" plate is already well over-engineered.

But really, this layman doesn't know where to start; how does one find the torsional (flexural?) rigidty values?

I've searched the "Internet" and found aluminum vs steel strength comparisons, but they don't say what the thickness of the Al material is...

Thanks for any input you can provide!
- Sam

 

[Navin A S]

You can calculate the torsional rigidity (also known as flexural rigidity) of the aluminum plates using the following equation: T = (W x L^3)/12 x (E x I). In this equation, W is the load applied, L is the length of the plate, E is the modulus of elasticity of the material (for aluminum, it's 10^6 psi), and I is the second moment of area for the cross-section of the plate. You can find the second moment of area for a rectangular section by using the formula I=bh^3/12, where b is the width of the plate and h is the thickness. By plugging in the values for the two plates (1/4" and 3/8"), you should be able to calculate the differences in torsional rigidity between them. Once you have the values, you can compare them to determine which plate would be more effective in real-world applications.