Learning Forum

[Jayakrishna]

I am combing elastic and viscoplastic material models to analyze stresses in a solidifying body.  

I am able to incorporate Young's modulus and Poisson's ratio as given in the image but not the yield stress.

I need to incorporate yield stress value varies with temperature. 

I have one more doubt. 

How to incorporate any property as a function of temperature for example

Property (T) = a-b*T+c*T^2+d.

Please, help me regarding this issue. 

Thanks in advance.

 

[Jayakrishna]

can somebody reply to this, at least, is it possible to implement or not ?

[BenjaminStarling]

It is not possible to input material data as an equation into APDL. You can however parameterise this and read any value during the analysis (in between load steps) and use the equation to update the value of a material property. I would not advise this.

APDL primarily works with tables, linearly interpolating between values. Using workbench and checking the ds.dat file you can see how this is acheived.

For yield stress, this material property does not take part in the analysis and does not get sent to the APDL solver. It's only influence is on the stiffness of the material if you are doing a non linear analysis (it can affect other properties that depend on yield but just focussing on the most important for a static structural).

To input stiffness as a function of temperature add the 'Structural Steel NL' from the general non linear materials library. Under the Bilinear Isotropic Hardening heading you will have Yield Strength and Tangent Modulus which can both be specified with respect to temperature. There are other non-linear elastic models you may want to explore also.

I am not sure how this will go with your viscoplastic material models, but hopefully this points you in the right direction.

[Jayakrishna]

Dear BenjaminStarling

Thank you very much for your kind and elaborate reply to my query.

Actually, I did not convey it properly. I want to see, how the results will change for the elastic-plastic and elastic-viscoplastic model. For that purpose, I need to

use temperature-dependent yield stress value.

I am using 'Structural Steel'. Thanks for suggesting me to use 'Structural Steel NL' to incorporate temperature-dependent yield stress. 

 

 

[BenjaminStarling]

Hi Jay,

Just to be clear, there is no need to use the Structural Steel NL in your analysis. This is just an easy example of a NL material in the library.

There are many forms of plasticity available that can be added to any mateial. Simply click and drag from the toolbox on the left onto any material in Engineering Data.

Because your project is material dependant it will be important to consider and select the correct material model.

Best of luck with your project.

[mrife]

 Hi Jayakrishna

Actually Mechanical APDL does have the ability to define a material based on a polynomial equation.  Please see the Mechanical APDL Commands Guide in the help; the Notes section of the MP command.  Materials that can be defined via MP command can be of the form Property=C0 + C1*T+C2*T^2+C3*T^3+C4*T^4 where C's are defined and T is temperature.  You could implement this by way of a Commands Object.

If you prefer to use Workbench, then I'd suggest using a tool (Excel etc) to evaluate the expression, then copy/paste into the proper material definition in Engineering Data.

Mike

 

[BenjaminStarling]

Hi Mike,

The MP command is for linear material models only and does not allow for the Property to be Yield Stress.