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Query concerning nonlinear stress vs strain graph

Builder
Builder

Hello everyone,

 

I have performed nonlinear static 106 test on porous material (Elastic –plastic model). My model consists 83000 elements. I have taken into considerations aluminum 6061 T6 property with initial yield stress of 55 MPa.

 

Now I want to generate nonlinear stress vs nonlinear strain graph for the whole model.

 

So what I did is I select all node and create one group and afterwards plot the graph.

 

I assume that this is not the right way, because nonlinear stresses are plotting vs all element.

 

On the other hand, if I see the research paper, they usually have stress ranging from 0 to 3 MPa.

 

I suppose it should be from 0 to 55 MPa because I have defined 55 M Pa initial yield stress.

 

Attached please find the pic of model that I have generated and the one that I wanted to make (from literature).

 

Does anybody please guide me how to do that?

 

Many thanks in advance.

14 REPLIES

Re: Query concerning nonlinear stress vs strain graph

Siemens Phenom Siemens Phenom
Siemens Phenom

I would suggest starting with a criteria plot of Von Mises stress and identify the element with the highest value, or use that plot to identify other elements of interest. Once you have identified one or more elements of interest, then use charting to plot the stress vs strain for those elements of interest.

In charting, use the type "vector vs vector" to make this plot.

It is usually of interest to plot "vector vs output set value" to see the results vs load magnitude also.

Hope this helps.

Regards,

 

Joe

Re: Query concerning nonlinear stress vs strain graph

Builder
Builder

Hi,

 

thanks for the answer.

 

well I have tried to followed your way as described above by just selecting few elements. Unfortunately. some options are prompting by showing ending outut must be greater then strating output.

 

Attached please find the picture of error and model. One more question, how can I select number of element out of the whole model when the model is so complicated. Attached please see the picture of model as well.

 

Looking forward for discussion.

 

Kind Regards

Varun

Re: Query concerning nonlinear stress vs strain graph

Siemens Phenom Siemens Phenom
Siemens Phenom

You have the 1st and last output set to the same output set which creates the error.

If you only see one output set, then you will need to rerun the analysis and request intermediate output so you have results at each converged load step. With a single output set, you only have one data point to plot, you cannot make a curve from one point.

 

2017-10-12 09_00_55-NASTRAN Nonlinear Analysis.png

 

 

Re: Query concerning nonlinear stress vs strain graph

Builder
Builder

Thanks, okay I got it. 

 

I need to run again the model and have to select yes in output control.

Re: Query concerning nonlinear stress vs strain graph

Builder
Builder

Hello@fembrackin,

 

I have run the analysis today and now I have all the output set.(Attached please find the pic)

 

I can only select two points , one in independent identity and one from dependent identity. 

 

and in the starting set, 1. I have used case 1 time 1, in ending set case 19 time 1. afterthat I plot the nonlinear solid von misses stress vs nonlinear solid von misses strain plot.

 

Graph is little bit confusing, it is in cyclic form, doesn't really understand. Can you please see the picture attached and disucss a bit about it.

 

on the other hand, I want to make stress strain graph for the whole model. How to make it?

 

selecting , independend and dependent identity means we are selecting all main stress level in the zone or something different?

 

Looking forward to hear soon.

Re: Query concerning nonlinear stress vs strain graph

Builder
Builder

Independent and dependent identity picture

Re: Query concerning nonlinear stress vs strain graph

Siemens Phenom Siemens Phenom
Siemens Phenom

In general, the vector vs vector plot would be used to look at 2 different vectors but at the same location. To create some meaningful plot that represents your entire structure, you will have to decide on some representative location or come up with some method to combine individual responses into some measure of the overall response. Think about calculating a "global strain" using the original dimensions and the final deformation from the nonlinear analysis. Maybe think about a load vs deflection plot. 

Creating a single number to measure the performance of your structure requires sound engineering judgement and knowledge of the fundamental behaviors that are important to your structure.

 

I have attached a sample model of a cantilever beam with nonlinear material. Look at some of the saved xy plots, maybe that will help you think of a good way to measure the overall performance of your structure.

Re: Query concerning nonlinear stress vs strain graph

Builder
Builder

Hi,

when I try to open the model, i got error saying 11.4 version is not compatible with 11.2. You may loose data.

Attached please see the pic.

 

Re: Query concerning nonlinear stress vs strain graph

Legend
Legend

Hello,

 

When you make a neutral file, you can change the version to 11.2:

 

Neutral File Write OptionsNeutral File Write Options

Best regards

 

Peter Kaderasz