Simulation Mechanical Forums (Read-Only)
Welcome to Autodesk’s Simulation Mechanical Forums. Share your knowledge, ask questions, and explore popular Simulation Mechanical topics.
cancel
Showing results for 
Show  only  | Search instead for 
Did you mean: 

Bodies moving through each other in static stress analysis

6 REPLIES 6
Reply
Message 1 of 7
sbhardwaj.amu
492 Views, 6 Replies

Bodies moving through each other in static stress analysis

Hello everyone,

I am quite new to Autodesk Simulation. I am using Autodesk Simulation Mechanical 2014. While I was doing a linear static stress analysis for an assembly, I saw an assembly part moving through another part when increasing the displacement (displacement option from result bar). I have kept the contact between these two parts as 'surface contact', so logically they should never cross each other. But parts happen to cross each other. Please help me with this problem and any mistake that I might be committing. Is this also taking my simulation result far away from reality?

I have attached the pictures depicting the situation that I am facing. First Image is showing my assembly and second image is what I get after after doing the stress analysis.

assembly.jpg

after stress analysis.jpg

 

6 REPLIES 6
Message 2 of 7

Hi,

 

Firstly, in Linear Static Stress, the computation is only performed at one instance of time. Hence, if two surfaces are not contacting each other in the original CAD geometry, then they will not contact each other and may pass through one another in the results, even though you set the contact type to surface contact between the parts. If you want to analyse the contact between parts, I suggest you perform a MES analysis, which will update the geometry as the analysis progresses through time.

 

Secondly, exaggerating the displacements via Results Contours>Displacement>Displaced Options is only meant for visualizing the very small displacements of your part. If you set the scale to be too large, it is possible that the visual might indicate that the objects are passing through each other, while in the actual result, they are actually not. Verify this by checking the displacement values at the critical node whether it has surpassed the gap size between the two parts. If the result values indicate that the parts do not cross each other, then they definitely do not cross each other, even if the exaggerated visual indicate otherwise.

 

Regards

Ilyas 

Message 3 of 7

Hi Ilyas, Thanks for looking into the problem.

 

I do not have any dynamic part in my assembly, so would it be right to use MES. My real concern here is that, though my 'part 1' (dark grey color) is not in direct contact with my base part i.e.. 'part 2' (light grey in color) in actual geometry. However with the application of load these two parts may interact with each other due to large deflection of 'part 1' pertaining to load. So over here a static analysis will give me the right result ? Or I have to shift towards MES.

 

Thanks

Siddharth

Message 4 of 7

Hi Siddharth,

 

If I remember correctly, LSS have gap elements to help simulate contact, but I am not familiar with those, and I think that it is not easy to use it with CAD generated mesh as the gap size must be specified. Hence, I would choose MES. Primary reason would be due to contact. MES does it best. Moreover, you might also take advantage of the large displacement analysis type in MES as LSS is only valid for small displacements.

 

Regards

Ilyas

Message 5 of 7

Hi IIyas..

Thats a better way and now the result looks more realistic...

Can you quote me some resource where I can learn about the 'element type' i.e. brick, truss, beam etc... because I am really confused about using them ...

Thanks
Siddharth
Message 6 of 7

You can look through the new help under User's Guide > Setting up and Performing the Analysis > Analysis-Specific Information > Linear/Nonlinear > Element Types and Parameters.

 

or just go here for linear analysis elements. If you have further questions on this, I suggest opening up a new thread.

 

Regards

Ilyas

Message 7 of 7

Thanks IIyas, that's a good idea to start a new thread as this forum is really informative.

Regards
Siddharth

Can't find what you're looking for? Ask the community or share your knowledge.

Post to forums  

Autodesk Design & Make Report