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Mesh Matching Problem

19 REPLIES 19
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Message 1 of 20
mschroepfer
1136 Views, 19 Replies

Mesh Matching Problem

Hello,

 

I have a meshing problem.  The automatic mesh matching does not match all of the nodes that I want meshed and it matches nodes that I do not want meshed.  If I increase the mesh matching tolerance it distorts the model even more causing eroneous stress concentrations.  Attached is some screen shots where I want to mech to be meshed or contacted in a particular way.  What is the typical way for modeling stich welds?  I want to stop the model from mesh matching and control what is in contact by creating bonded contact between the surfaces and setting the tolerance value.   I was reading that mesh matching could be stopped by deactivating components and meshing the components individually.  However, I read in the version 2012 release notes that the deactviate/activate feature was replaced by the suppress feature.  This does not work with suppressing portions of the model because I have to remesh before it will let me solve.  I tried meshing the model with setting the contact default to "Contact (Default Free/No Contact)" which gives me the mesh that I want to work with.  However, even though I define the bonded contacts that I want the free contact that is detected during meshing prevents my bonded contacts from holding.  What would the best stategy/method to give me the control I want.

 

I worked with ANSYS Mechanical for static structural analysis before this and I am trying to gain the same or similar functionality at least out of Autodesk Simulation Multiphyisics 2012.

 

Thanks,

Michael

19 REPLIES 19
Message 2 of 20
madg1
in reply to: mschroepfer

did you check the model after surface mesh?

coz some elements look distorted ? Ior the geometry looks like that?

 

 

 

madg1
ASIMM 2012
Message 3 of 20
mschroepfer
in reply to: madg1

I did check the model after surface meshing and yes the elements become distorted.  The geometry does not look like that before meshing.

Message 4 of 20
madg1
in reply to: mschroepfer

then, i guess you need to fix that....

madg1
ASIMM 2012
Message 5 of 20
mschroepfer
in reply to: madg1

How do you fix that?

Message 6 of 20
madg1
in reply to: mschroepfer

you can play with mesh size or turn off automatic sutace mesh refinement......or vcad....i don't know....  that distortion may be a prob...

madg1
ASIMM 2012
Message 7 of 20
mschroepfer
in reply to: mschroepfer

There is no option I can choose that does not distort the model except by changing the default contact to "Free/No Contact".  However, the parts in the assembly do not hold together no matter what I specify for contact options.

Message 8 of 20
mschroepfer
in reply to: mschroepfer

When I set the Contact default to "Free/No Contact" and then mesh the model is when the parts don't hold together.  Otherwise the parts do stay bonded together but are distorted.

 

 I just wanted to clarify.

 

I still have not found a way to prevent the distortion but also maintain the appropriate contacts.

Message 9 of 20
madg1
in reply to: mschroepfer

I m no expert...but try this..

assuming you are using static analysis and solid elements..

set the mesh size

go to parameters---contact ----smart bonding----fine to coarse....

now push mesh model.....

see if this meshes perfectly...if not

 turn off vcad

turn off automatic surface refinement....

repeat the above process....

check again...

 

change the mesh size....and check atleast 3 times....cross check the cad model......

 

if all these doesn't work.......then we need A-team......:)  

madg1
ASIMM 2012
Message 10 of 20
mschroepfer
in reply to: madg1

It does not work.  Just a note; Plate elements are being used not solid elements.

Message 11 of 20
mschroepfer
in reply to: mschroepfer

I am trying to midplane mesh sheet metal parts that are connected together.

Message 12 of 20
madg1
in reply to: mschroepfer

upload the model...if you can.....

madg1
ASIMM 2012
Message 13 of 20
mschroepfer
in reply to: madg1

I cannot upload the actual model that I am working on because of confidentiality but I have created a 'mock' model that is similar and is giving me the same problems.  I am uploading two archives of the model, the first is without results and the second one is the one with the most recent results.

 

Just a note on some on the model.  The center two plates are offest 0.1 in from the L shaped piece and the meshes are matched.  The end plates are assembled in Invertor flush with the L-shaped piece but the top edge is not matched with the L-shaped piece.  The last time the model was meshed the tolerance value was set to 0.001 in and absolute value which means the center pieces should not be matched.

 

 

It would not let me upload the autodesk simulation archive or file so I uploaded the CAD model.

Message 14 of 20
madg1
in reply to: mschroepfer

madg1
ASIMM 2012
Message 15 of 20
mschroepfer
in reply to: mschroepfer

Parts included.

Message 16 of 20
madg1
in reply to: mschroepfer

hello mschroepfer 

 

please try to convert assembly file into .stp file and upload it for me....or you can try your self stp format once

madg1
ASIMM 2012
Message 17 of 20
mschroepfer
in reply to: mschroepfer

It won't allow .stp files to be uploaded.

Message 18 of 20
KubliJ
in reply to: mschroepfer

Hi mschroepfer,

 

 

How are you planing to mesh it? Solid or Midplane?  Solid may not work due to aspect ratios, the part is very thin for its size.  And on that I do not recommend using Midplane as it is unfortunately not intelligent enough when it comes to parts seperated by a small gap and features ( airbag spacers 2 & 3 in respect to Angle Frame) with parallel faces.  If you wish to use plate elements (I would recommend) then the best practice would be to model surfaces in CAD and import that in for plate meshing.

 

If you are trying to simulate a welded connection I would suggest changing the default contact to Welded.  This will ensure that only the nodes on the edge of a matched surface are used for contact.  I do not recommend this if the contact is likely to be under compressive forces as the interior nodes are set for free no contact and will pass through each other (assuming there are interior nodes).

 

 

Please mark as solved if this answers your questions.



James Kubli, P.E.


Please marked this as solved if your question has been answered.
Message 19 of 20
mschroepfer
in reply to: KubliJ

Hi James,

 

Thank you for responding to my question.

 

I am planning on midplane meshing the model and using plate elements. 

 

I found that I can midplane mesh the model and by using a very fine surface mesh refinement around the edges to prevent distortion.  I can make connections by setting the bonded contact option to ‘coarse bonded to fine mesh’ and manually defining each contact and setting the tolerance  absolute distance on each contact.  By setting the contact to a specific tolerance the parts that make a perpendicular interfaces with each other can be connected so that only the nodes along the edge of the surface are in contact. 

Is this a poor modeling method?

 

There seems to be higher stress concentrations using this method at corners and connection interfaces (shown in the attached image).  Is this preventable? 

 

Thanks,

Michael Schroepfer

 

 

Message 20 of 20
KubliJ
in reply to: mschroepfer

Hi Michael,

Please see the attached model on one way to model the connections desired.  I converted some of the parts to surfaces for direct meshing as plate elements and others I left as solids.  To create the contact with the welds I manually drew the welds for inclusion in the analysis.  This method gives me more control over the quality of the model, uses a lower mesh density and provides quicker results. 

 

As for the method you are using with the refinement points, I would not recommend it based mostly on the extreme mesh density created.



James Kubli, P.E.


Please marked this as solved if your question has been answered.

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