Learning Forum

[Nelsen FOLY-TOULAN]

Hello everyone i have an issue with my thermal analysis.

i've done a thermal expansion analysis with ansys workbench and i've displayed many informations like stress, displacement etc... 

But in my case only the displacements are interesting. The issue come's when i try to check the result in  Woekbench with a handed calculation ( i find differents values with the hand calculation ( 25µm) and with workbench i find (33µm)). For the handed calculation i've used the formula :$\Delta L=a\cdot L_1\cdot (T_2-T_1)$

$the\; system\; is\; just\; a\; roll\; represented\; by\; a\; quart\; of\; a\; circle$

$thanks\; for\; your\; help$

[Sampat Kumar]

Hi Nelsen, 
Will you please upload a screenshot of the simulation and hand calculation that you have done so that I can verify where is difference created? 
Please include the BC also in the screenshot.

Regards, 
Sampat

[Nelsen FOLY-TOULAN]

Hello thanks for the reply, and sorry for the delay 

With the handed calculation, just take in consideration the first calculation ΔL1 ( the 2 others are for other part of my assemby and i've disabled the in Workbench)

 

Material used is stainless steel

PS : Sorry, some BC are in French

The BC (support fixe= fixed support).

I have disabled the remote displacement (deplacement distant) because my model is an assembly of different pieces and the main goal of my study is to find the slack between them. In this case I just wanna the displacement of the roll and  when I compare just the displacement of this one with the handed calculation, I find different results.

Thx for the help

[Nelsen FOLY-TOULAN]

Next to my last reply , this is the displacement

[Sampat Kumar]

Hi Nelsen,

I have some queries and suggestions based on your data; please verify those.

1. Please check whether the large deformation is ON or not.
2. Where have you applied fixed support in the simulation, Please mark that part. 
3. Apply the probe and see what the value of the deformation is on the larger area instead of a single point. 
4. Please also verify the directional deformation here in the simulation. 

Regards,
Sampat

[Nelsen FOLY-TOULAN]

Hi, 

So i've checked the differents options you are talking about in your last post:

1. Large deformations are OFF

i've also applied displacements on 2 faces :

3. Results with the probe:

4. directional deformation:

[Nelsen FOLY-TOULAN]

Ps to my last post: i've also run the same analysis on another FE software ( femap) with the same boundary conditions and i find the same results as my handed calculation

[Sampat Kumar]

Hi Nelsen, 
Will you please do Large deformation ON in the analysis setting? and let me know. 

Regards, 
Sampat

[Nelsen FOLY-TOULAN]

 

Hi M Sampat, there’s the calculation with the large deformations ON : 

( This is the 2D model where i've also try the analysis)

(3D model)

[Sampat Kumar]

Hi Nelsen,
I have tested it on my end. The deformation depends on the loading conditions that you applied. What types of boundary conditions have you applied to the model?
I have applied for fixed support on both faces as highlighted, and then you can see the total deformation in the below image.


It makes sense that if you apply the fixed support to both flat faces, then your deformation will be maximum at the center of the outer surface. The body can deform radially outward.

Regards,
Sampat

[Sampat Kumar]

Hi Nelsen,
I think you can use frictionless support also but again it depends on how you want to model your geometry and what are the boundary conditions that you have applied. I have used frictionless support at the two side faces and one bottom face.


Regards,
Sampat

 

 

 

 

[Sampat Kumar]

If you attach frictionless support to the side, top, and bottom faces also, you can experience the 0.033806 mm deformation that you mentioned earlier in the screenshot.

Please let me know if you have any issues.

Regards,
Sampat

 

[Nelsen FOLY-TOULAN]

hi Mr Sampat, thanks for the reply. So i've tried your loads of my model but i've always the same problem. i find 0.023mm in total deformation.

In my inital model i've also applied 2 displacement on flat faces but i've allowed 1 displacement on each face ( eg : Ux=0 Uy=0 Uz=free) Screenshot :

My analysis is about thermal expansion of a roll reprenseted by a quart in Ansys for simplifying the problem. I think frictionless support is not the most adapted to represent the problem. I'll retry a new analysis and i'll update you  

Best regards 

Nelsen 

[Nelsen FOLY-TOULAN]

 

And the results with the handed calculation are not the same

You're result of 25.9 µm is the correct displacement ( i've found the same with handed calc).

 

[Sampat Kumar]

Hi Nelsen,
Sorry for the late reply.
Will you please apply for fixed support instead of using displacement? For displacement can you provide constrain (displacement=0) to all the directions in your model? Are you performing the 2D analysis? 
I applied the fixed support to both sides of the flat surface or provided the displacement zero to all the directions on both flat surfaces and got the deformation of 25.9 µm. please apply the same BCs and let me know what you observed in that. 

Regards,
Sampat

 

 

 

[Nelsen FOLY-TOULAN]

update: i've tried a new analysis but i've exactly the same results as my last analysis. Is it possible to send you my analysis ? 

[Sampat Kumar]

yes, You can upload the screenshot of the analysis. I can't download any files or documents from here. 

Regards,
Sampat

[Nelsen FOLY-TOULAN]

Hello Mr Sampat, thanks for the reply and sorry for the late. I was in holidays so i havent acess to my desk. 

For the problem, i've already applied constraint ( displacement =0) to all directions of my model but i never found the 25.9µm , instead i find 34.3µm. 

For the type of analysis i've run 2D and 3D analysis with constraint on flat surfaces but i never found the good results. 

Screenshoots:

3D analysis:

(Constraints for both surfaces) 

Also tried with fixed support for the BC but i find the same result.

 

2D analysis :