Unable to see imported body temperature in structural transient solution

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  • Last Post 25 July 2018
TomRochefort posted this 03 July 2018

I am trying to simulate material removal from laser irradiation in workbench. I import my thermal load from transient thermal analysis to transient structural analysis and then I want to use a EKILL command to neutralize the elements above a certain temperature in the structural analysis. It seems the ADPL command cannot see the imported temperature field when I use the "NSEL" command to select the nodes above the specified temperature. I use SOLID227 elements to enable the temperature DOF on the nodes in structural analysis. When I plot the TEMP user defined result I also cannot observe the imported body temperature in the solution module.

The same mechanical ADPL command works fine in the Thermal analysis module. It seems that the imported body load is probably not imported in the database of the structural solution and therefore the ADPL command cannot see it... I'm lost on this part! If someone has an idea it would be a big help!

 

Tom

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bsista posted this 06 July 2018

Tom,

If you're running the thermal analysis in a separate system and then importing the temperatures into a structural system, then SOLID227 are not relevant for your case. In structural analysis, you can apply imported temperatures using BF or BFE commands. Perhaps, sharing your APLD snippet might be helpful in debugging.

Also, you may already know this but when you issue EKILL on some elements, it doesn't delete them but rather reduce their stiffness by a factor of 1e-6. Just letting you know so you can calibrate your expectations when you simulate the "material removal".

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TomRochefort posted this 06 July 2018

Hi Bsista,

Thank you for your time! 

Im using SOLID227 because the standard mechanical elements that the structural analysis mesher uses does not have a TEMP DOF. I have tried the "DOF,TEMP" command to simply add the DOF to the element set but it did not work

Here is a screenshot of my ADPL command to select and kill the elements above a certain temperature:

 

ADPL Command

 

My worktree looks like this:

Worktree

 

The problem is that the command does not see the imported body temperature:

Solution information file

Its important to note that the maximum body temperature reaches 800 degrees in the thermal analysis after the first load step and therefore some nodes should be selected by the NSEL command. The problem seems to be that the ADPL routine does not see the imported temperature field when it gets to the NSEL command.

As for the EKILL command, I knew about the 1E-6 stifness reduction. I will look into changing the material properties to more properly simulate the "absence" of the element using MPCHG command instead.

Sincerely,

 

Tom

TomRochefort posted this 23 July 2018

Hey Bsista!

Do you still think you could help me?

 

Thanks,

Tom

bsista posted this 24 July 2018

Hi Tom,

Sorry for not getting back to you on this, I was travelling for a bit.

The problem with your setup is that the imported temperature is defined as a body temp. (applied to the element) whereas Solid227 has temp. defined at the nodes. So, unless you solve for at least one load step, the temp. of all the nodes are at room temperature. You'll need to split your simulation into multiple load steps only then you'll be able to kill elements between the load steps. Before doing that try these steps to debug your setup:

1. Suppress the command snippet and solve the model. Then the TEMP object must plot the temperature results, this is to make sure that the temperature is being read and mapped as expected.

2. Use the NSEL commands to select elements within a temp. range in the /POST1 module to verify your element selection scheme.

3. If the above two steps work as expected, proceed with splitting your simulation into multiple load steps and issue the element selection and EKILL commands as you have in the setup. Make sure that in the details of the command snippet object, set Step selection model to All so the command is executed every load step. 

Also, have you set KEYOPT(1)=11 for SOLID227 element to turn on the structural-thermal analysis?

TomRochefort posted this 25 July 2018

Hi Bsista,

Thank you for your reply.

To answer your last question: I have set the KEYOPT(1)=11 to turn on the structural-thermal analysis.

However when I try step 1 of your troubleshooting, I still cannot see the imported body load from the thermal analysis.

All I can see is this weird temperature drop where the block is compressed against a fixed support. I do not understand why the temperature drops to about 0 degrees on the fixed surface.

 

In the image, the surface to the left is the fixed support and a force is applied to the left (+ Z direction) on the right surface

The imported body temperature is not plotted and therefore is not converted to nodal temperature in the 3 load step of the analysis.

 

Best regards,

 

Tom

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