# Include Stress as initial condition

**URL:** <https://calculix.discourse.group/t/include-stress-as-initial-condition/637>\
**Category:** Uncategorized\
**Created:** [June 24, 2021, 7:03am UTC](https://calculix.discourse.group/t/include-stress-as-initial-condition/637 "2021-06-24T07:03:01Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![irphe](https://avatars.discourse-cdn.com/v4/letter/i/43a26b/32.png) [@irphe](https://calculix.discourse.group/u/irphe)\
**Post date:** [June 24, 2021, 7:03am UTC](https://calculix.discourse.group/t/include-stress-as-initial-condition/637/1 "2021-06-24T07:03:01Z")

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Hello,

I want to check the behavior of a plate with an initial stress, but the result is not what I expect.

The idea is to apply a uniform pressure on a plate fixed on the right corner during a dynamic calculation.

 ![config](https://global.discourse-cdn.com/free1/uploads/calculix/original/1X/4c7a76cab2aff79db20d24bf762fb390a6dc3ada.png)  
 ![configopen](https://global.discourse-cdn.com/free1/uploads/calculix/original/1X/e28db22b01067f44a15b91b08fcb27ae0061f714.png)

Then I save the new deformed mesh and the stress at the last iteration, I run a new simulation with this mesh and this stress as initial condition but without any pressure.

If I do this new simulation in STATIC with the NLGEOM solver,the plate almost goes back to the initial state but there is still a gap about the value of displacement.

 ![static](https://global.discourse-cdn.com/free1/uploads/calculix/original/1X/abd1c24460a5b732a2c8c83adca82c6350723884.png)

When I check the stress in the \_main.dat, strangely the stress in the element change a little but doesn’t tend to zero during the calculation.

If I do the same in DYNAMIC, the time step decrease and the plate doesn’t go back at all to its original flat shape (I stopped the calculation after 1 day).

 ![dyna](https://global.discourse-cdn.com/free1/uploads/calculix/original/1X/496b824a0d65fe9f0238165a36221d8a4d7c1dfc.png)

For me, in both cases the plate should go back naturally to a the original shape in order to cancel the initial stress?

For information, I apply the initial stress by using “\*INCLUDE, INPUT=add\_stress.inp” in my \_main.inp with add\_stress.inp the file containing the stress during the last iteration of the first calculation.

I appreciate any hints

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**Author:** ![tugrultamerc](https://avatars.discourse-cdn.com/v4/letter/t/e274bd/32.png) [@tugrultamerc](https://calculix.discourse.group/u/tugrultamerc)\
**Post date:** [June 26, 2021, 5:04am UTC](https://calculix.discourse.group/t/include-stress-as-initial-condition/637/2 "2021-06-26T05:04:58Z")

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Hi  
I have tried this before. The most important hint I can give is telling you to check the stress types of output and input files of Calculix.  
As I recall,  
the output stress in dat file is SXX, SYY, SZZ, SXY, SXZ, SYZ  
however,  
the input of ccx should be SXX, SYY, SZZ, SXY, SYZ, SXZ

Also, I have tried the same thin with abaqus by making an analysis with two steps:  
I have fixed one side of bar before the step initialization,  
then applied pressure at first step  
and then to removed the pressure by typing \*DLOAD, OP=NEW  
I know that you have two analyses, one of which inherits the conditions from the other.  
If you can share the inp file here I can check the conditions.

PS: You can run the same analysis using \*INITIAL CONDITIONS, TYPE= DISPLACEMENT and exporting the displacement field of each node to the following lines.

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<div class="post-metadata">

**Author:** ![irphe](https://avatars.discourse-cdn.com/v4/letter/i/43a26b/32.png) [@irphe](https://calculix.discourse.group/u/irphe)\
**Post date:** [June 30, 2021, 8:18am UTC](https://calculix.discourse.group/t/include-stress-as-initial-condition/637/3 "2021-06-30T08:18:47Z")

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Hello

Ok, now I can go back to the initial state by using “\*DLOAD, OP=NEW” in a multi step run.

About start a simulation with an initial stress as condition, for the moment I still don’t have very good results in static even by switching SXZ and SYZ, I will check the conditions.

Thank you