NonLinear material modelling

Naresh_20479

Hi ..

I am doing a material noninear analysis.

The material definition is as follows

E=210000Mpa     Limit1 =330MPa  

After running the solution for some time i am getting the following error.

I also attached output file. 

can any one help me ? 

Thomas Quenaon_21507

Hi Naresh,

Your stress-strain curve must be defined with data points being in ascending order. Also for analyses where small deformations are not assumed, the true (Vs. Engieneering) stress-strain curve should be used.

 

BR-

Thomas

Naresh_20479

Thanks for the reply ..

After posting the question , I tried that but some times the same error is coming ..

and some times it is not even converging ..

The model has no contacts ..Its a simple rod under tension ..But still not converging..

Please guide me..

 

Thomas Quenaon_21507

Naresh_20479 said:

Thanks for the reply ..

After posting the question , I tried that but some times the same error is coming ..

and some times it is not even converging ..

The model has no contacts ..Its a simple rod under tension ..But still not converging..

Please guide me..

 

I suggest to go step by step in the non-linear behavior. 

• First don't use MATS1 card and run the quasi static non-linear analysis with linear material
• Then add MATS1 by using the hardening slope H instead of a curve
• then modify MATS1 to use a curve

With those iterations you'll be able to isolate the problem. I haven't seen the last model but I would say that the curve is not defined according to the requested definition.

BR-

Thomas

Naresh_20479

Thomas Quenaon_21507 said:

I suggest to go step by step in the non-linear behavior. 

• First don't use MATS1 card and run the quasi static non-linear analysis with linear material
• Then add MATS1 by using the hardening slope H instead of a curve
• then modify MATS1 to use a curve

With those iterations you'll be able to isolate the problem. I haven't seen the last model but I would say that the curve is not defined according to the requested definition.

BR-

Thomas

Dear Thomas 

Thanks for the quick reply. 

I have give a try for three cases first two are converged and the third didnot.

The curve used for TABLES1 is as attached.

 Please give your suggestions.

 

Thomas Quenaon_21507

Naresh_20479 said:

Dear Thomas 

Thanks for the quick reply. 

I have give a try for three cases first two are converged and the third didnot.

The curve used for TABLES1 is as attached.

 Please give your suggestions.

 

Last segement of the curve is not right, the slope can't increase, it should only be decreasing from segment to segment.

BR-

Thomas

Naresh_20479

Thomas Quenaon_21507 said:

Last segement of the curve is not right, the slope can't increase, it should only be decreasing from segment to segment.

BR-

Thomas

I have deleted the last points , so that the slopes can all decresing only ..But i see the same result.

Also for other simulations the solution converged for increasing slopes as well.

Please guide me. this is crucial for us.

Thomas Quenaon_21507

Naresh_20479 said:

I have deleted the last points , so that the slopes can all decresing only ..But i see the same result.

Also for other simulations the solution converged for increasing slopes as well.

Please guide me. this is crucial for us.

What if you only use the 3 first points ?

Without the model and/or the .out file it's difficult to juge. It may be easier to contact your local support.

BR-

Thomas