Thermal expansion and material orientation

[Lucy A]

Hi,

I am trying to increase/decrease heights of vertebral body (local material orientation defined in z-axis )in a finite element scoliotic model using thermal expansion. The height is being changed but the problem is that it is not being changed according to the defined material orientation. To check the issue, I have copied all the orientations and sets from another input file (this is a template model and this model is running in the defined orientation) and tried to run but the issue still remains the same. The template model is straight spine model and my model has curve in thoracic region.

Since the template model is running, I could not figure out why my model is not running with same orientations copied from the template model. Can anyone of you suggest me what things should I be careful of while using thermal expansion and defining material orientation? Please let me know if the question is not clear. I will try to explain more.

Thanks.

 

[FEA way]

Can you attach a picture showing these material orientationas for both the discussed model and the template model ?
You say that you've copied all orientations and sets but are local coordinate systems the same too ?
Which elements do you use ? There are some special considerations for some types when assigning orientations.

 

[Lucy A]

Hi FEA way,

I have attached the pictures. Also, when I try to see the orientations in my model a dialog box pops up every time which does not happen in the template model when I double click on the orientations to see them. I have attached the picture too. Is it that I have to do assign the orientations manually in CAE rather than copying the orientations from input file?

Yss, the local coordinates are the same too. Element used in both the model is linear hexahedron type C3D8.

Thank you so much for your response.

 

[Lucy A]

Looks like all three images couldn't be attached in same post. So, sending it again.

 

[Lucy A]

This is the scoliotic model.

 

[FEA way]

I would try defining these orientations in CAE rather than through input file to see if it makes a difference.
Sometimes when you mix CAE and .inp usage then errors occur. Especially when you edit something in the file and then open it in CAE - the software may delete or change your edits even if they are supported by CAE too. Thus it is better to run the job through command line after editing the input file.

 

[Lucy A]

Thank you very much for the quick responses FEA way. Really appreciate it. I usually run job through command line after editing the input file. The issue is still there so it looks like I have to do it manually. I will try and see if it works.

 

[Lucy A]

Hi FEA way,

I did try few things but nothing worked. But I have figured out that the way I have been defining orientations is not correct. The overall steps that I did are:

1. Apply boundary condition (encastre) to the bottom surface of vertebra: Step initial
2. Use predefined field and select required region: Step 1
Go to property module:
3. Assign section to that selected region
4. Create coordinate system
5. Assign material orientation

Expansion type is orthotropic.

The issue I found is that after I created a input file and imported it back to CAE to see the orientations, I did not find the ones I assigned. This means that the way that I tried to define the orientation has been incorrect. Can you please let me know how to create a local coordinate system and assign material orientation? I am reading about this to figure out this issue but in the mean time thought of asking you so that I can gain some insight regarding this as well.

Thanks.

 

[FEA way]

This way seems correct as long as you define local coordinate system (for solid elements the only restriction in material orientations definition is that local CSYS must be defined).

As I said before, some features disappear when inp file is imported to CAE. Maybe even when inp was created in previous session of CAE only (no manual edits). It is better to open .cae files in Abaqus/CAE and use inp only for maual job submission.

 

[Lucy A]

Thank you so much for your suggestions and giving your time to respond to my questions. I could finally solve the issue. Thanks again.