Learning Forum

[Philippe CLECH]

Hello.

I want to insert an user defined results from the available solution quantities.

Which expression should I select from the list for create custom failure criteria (Tsai Hill) ?

In a tutorial I found an example where there is this expression but I don't know where to look for it in the list.

Thanks in advance for your help.

Philippe.

[Govindan Nagappan]

Available solution quantities will not have an expression for failure criteria. Becuase it is not a result saved in the result file.

It is evaluated after you insert the result object under solution branch using the material properties(example: tensile strength, compressive strength) and results(stress, strain etc). These material properties are not required for FEA solution and only used for evaluating failure criterion. So, these results are eveluated when you request it. 

[Govindan Nagappan]

For information on failure criteria, check these help pages

2.4. Combined Stresses and Strains (ansys.com)

2.1. Formulation of the Failure Criteria (ansys.com)

[Philippe CLECH]

Hello .

In a tutorial I found the expression I need to write to define the Tsai-Hill.

In my specific case, if I have understood correctly, I have the following values:

_ 107 strength in fiber direction

_ 75 strength transverse to fiber direction

_ 45 shear strength.

• 
• 
• 
•  
• So I wrote down this expression:  SX*SX/(107*107)+SY*SY/(75*75)+SZ*SZ/(75*75)-(1/107*107))*SX*SY-(1/(107*107))*SX*SZ-(2/(75*75)-1/(107*107))*SY*SZ+SXY*SXY/(45*45)+SXZ*SXZ/(45*45)+SYZ*SYZ*(4/(75*75)-1/(107*107))

And it doesn't work, I get the following error message: 

Thank you for your help.

Philippe.

[Erik Kostson]

 

Hi

put bits/parts of your expression in, and see where and when the error occurs – for sure there are some parts with too many or few brackets.

Erik

 

[Govindan Nagappan]

 

I think there is an additional bracket here

(1/107*107))*SX*SY

 

[Philippe CLECH]

Hi Eric.

I managed to write down the expression and got a result.

But my result seems incorrect.
Have I taken the right values?

_ 107 strength in fiber direction

_ 75 strength transverse to fiber direction

_ 45 shear strength.

Can you confirm this for me?

Philippe.

[Erik Kostson]

Hi

Closing this as a support request has been created and recieved (help will be provided via support request).

Thank you

Erik