Learning Forum

[tobias.doerr]

Dear All,

I'm using Ansys 2023 R2, Mechanical Application within Workbench.

The purpose is a crack simulation of an arbitrary crack, calculating Fatigue (number of cycles under variying loads).

For this purpose, I use Paris law (Fig.1). This works fine as long as I use only one value for Material constant C and exponent m in the Engineering data.

 

However, if I want to use Paris law with different material constants and exponents depending on temperature (Fig.2), it doesnt work.

Is there a way to make it work?

        

Thanks for your help.

Regards,

Tobi

   

[Lydia Lymperopoulou]

Hi Tobias,

You can define a temperature-dependent crack growth law in a SMART Crack Growth analysis but you will need to employ some APDL commands.

"The constants can be defined as a function of temperature (TBTEMP or TBFIELD,TEMP) and/or stress ratio (TBFIELD,SRAT)" :  https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v241/en/ans_frac/franundcgrowmech.html%23fraccgrowmechanics

So, insert a Commands Object under your SMART Crack Growth Object; First apply Paris law  but then define the two temperature points like tbdata,1,C1,m1and tbdata,1,C2,m2

Then assign the crack growth law to crack CGROW (ansys.com) like:

cgrow,fcop,mtab,cglawid

[tobias.doerr]

Thank you very much for your great help.

In the meantime another question pops up:

I would like to map external imported Loads like initial strain on to my mesh. However, it seems, it cannot be used together with SMART fracture. 

Is there a solution for this?

Thanks a lot!

[tobias.doerr]

EDIT: The question before mentioned aims to adress the following:

• 1. I want to make a creep calculation of the model
• 2. map the residual stresses/strains onto a submodel
• 3. calculate crack fatigue with the pre-conditioned stresses/strains (stress ratio is 0)

Thank you very much for your help!