Learning Forum

[ashish35]

Hello,

I couldn't find any option to view signed Von Mises stress result in Mechanical. Is it possible to view this result?

Best,

Ashish

[Rohith Patchigolla]

Hi Ashish, 

Signed von Mises stress can be calculated using user-defined results.

Hydrostatic stress is simply the average of the three normal stresses [(sx+sy+sz)/3 ], so dividing the hydrostatic stress by the absolute value of itself will give -1 for compression and +1 for tension [(sx+sy+sz)/abs(sx+sy+sz)]. 

This stress sign can be directly multiplied by the unsigned von Mises stress to produce the signed von Mises stress. 

Signed Von Mises = seqv*(sx+sy+sz)/abs(sx+sy+sz)

 

But the method breaks down when the hydrostatic stress is zero. So, we add a small number to the equation as shown below.

Please use the below expression in a user defined result to get the Signed Von Mises stress. 

seqv*(sx+sy+sz+1e-6)/abs(sx+sy+sz+1e-6)

Hope this helps.

Best regards,

Rohith

 

[ashish35]

Rohith,

Thank you so much. This is spot on.

Best,

Ashish

[emmanuel.lecomte]

Hello,

 

What could be the python script to calculate this signed Von Mises stress ?

I try but I failed to calculate the abs value of the formula.

Thanks

E.L.

[Erik Kostson]

This post is from 2018 and is now closed. Open up a new one describing and showing any scripts used so members can provide some help.

Erik