Can you calculate torsional constant in AutoCad? 1

[sutki1]

I am familiar with massprop.
Can AutoCad calculate the torsional constant, J?

 

[chicopee]

Your J value is just the sum of Ix and Iy which you will get when invoking the command LI on solids

 

[dik]

The sum or the root of the squares? Been so long, I've forgotten (second thing to go is the memory) <g>

dik

 

[sutki1]

That J is the polar moment of inertia which is different from Torsional Constant

 

[chicopee]

I am so use to using J as the polar moment of inertia and not as the torsional constant that my answer was not was you were looking for. Since torsional constant is in essence a polar moment of inertia calculation, you can still apply the region/mass property command and use the J value with a slight error. For circular thin wall tubing that error will be of a magnitude( ie, slightly higher value)of (pie*R*t^3)/2. Note t^3 is very small for thin wall tubing. For circular thin wall tubing the polar constant is 2*pie*t*R^3 and the polar moment of inertia will sligthly higher by the error value that I mentioned.

 

[sutki1]

I dont think torsional constant can replace polar moment of inertia. even for simple rectangular tube the difference is in the magnitude of 400%. I am however not familiar with solids.

 

[chicopee]

Yes, you are correct, I rechecked my calculations on a couple of exercises and values for torsional constant were greater than the polar moment values.