How to get stresses between substeps or loadsteps?

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  • Last Post 16 February 2020
edyijung posted this 13 February 2020

I am modeling a uniaxial compaction test for a granular material using Ansys workbench 19 & Mechanical.

There is a pack of grains in a container, and will be considered as one solid body for simplicity.

One of unique physical properties of this body is that the Young's modulus is a function of stress (not like most materials which have constant modulus - only dependent on temperatures)

My model consists uniaxial loading to 6 MPa and unloading to 0 MPa. I have applied EDP plastic model to materials properties under the Geometry tree as a Command (APDL) Snippet. I set up two steps (one for loading and the other for unloading), and could solve without any troubles if I used a constant Young's modulus.

However, I wanted to change the Young's modulus during calculation process. So, I look up the ADPL manual, and find the *Get commend. To use the command during calculation, I increased the number of steps, for example, 2 to 20 (10 steps for loading and another 10 steps for unloading). I found that the Command (APDL) Snippet inserted at Static Structural Environment worked well after every time steps if I set the Step Selection Mode to All.

However, unfortunately, I cannot get the stress value after each time step when I use the *Get commend as follow:

----------------------------------------------

!/post1

*GET,substress,NODE,100,S,EQV   ! Get the equivalent stress as stress

newym = 1200*substress + 5e7

 

!/prep7

MP,EX,1,newym,                            ! Pa

----------------------------------------------

This is the Solver Output

*** WARNING ***                         CP =       1.172   TIME= 16:227
 Requested data is not stored for node 100.                             
  Line= *GET, substres, NODE, 100, S, EQV                               
  The *GET command is ignored.                                          

 *** WARNING ***                         CP =       1.172   TIME= 16:227
 Unknown parameter name= SUBSTRESS.  A value of 7.888609052E-31 will be  used.                                                                  
 PARAMETER NEWYM =     50000000.00   

 MATERIAL          1     EX   =  0.5000000E+08 
 *****  ANSYS SOLVE    COMMAND  *****

 

Please, help me to get the right values, and let me know how to use correctly the Command.

(By the way, is there any way to get the equivalent stress of body during or after substeps? If possible, I might not need to make multiple time steps.)

Thank you in advance!

peteroznewman posted this 16 February 2020

If you are in Mechanical and using Command snippets, if you have just two steps, load and unload, but each step has specified a minimum of 20 substeps, put in an Equivalent Stress plot under the Solution branch and in the Tabular Data window, you can see all the substeps and can plot the stress from each of them.

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