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Active Contributor tim
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tim
Posts: 37
Registered: ‎10-10-2012

Simulating welds using 2d elements

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04-10-2013 08:44 AM

Greetings,

I've searched the forum for this and not found what i want.  Here's a link that explains this

 

http://www.mscsoftware.com/training_videos/patran/Reverb_help/index.html#page/Fatigue%2520Users%2520...

 

There are several other organisations that do this as well.

 

It details using plate elements for the fillet weld with thickness twice that of the structure (which also uses plate elements).

 

1.  Does any one know how I can draw in a long series of plate elements which represent the weld, on a midplane meshed structure (or brick element structure) which I have imported from Inventor?

 

2.  Other references, state that fillet welds must be simulated using solid elements.  Can anyone comment or give a useful link?

 

3.  Has anyone had much experience simulating welds using ASM?

 

4.  Can anyone comment on using the welded contact within ASM?

 

Thanks

 

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Active Contributor tim
Active Contributor
tim
Posts: 37
Registered: ‎10-10-2012

Re: Simulating welds using 2d elements

04-17-2013 09:38 AM in reply to: tim

I'm really hoping someone will have some advice on this as I have this need almost on a daily basis.  I'll cut down the question a bit:

 

1.  Does any one know how I can draw in a long series of plate elements which represent the weld, on a brick element structure which I have imported from Inventor?

 

 

2.  Has anyone had much experience simulating welds using ASM?

 

 

Thanks

 

 
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AstroJohnPE
Posts: 547
Registered: ‎08-30-2012

Re: Simulating welds using 2d elements

04-17-2013 01:31 PM in reply to: tim

Hi Tim,

 

The link to the MSC website that you provided does not work for me; is the link too long? It could be a problem on my end. Perhaps it would be better to give a link to their home page and the title of the page that can be found by a search.

 

To answer question 1, you could use the "Draw > Draw > Line" command, or if the existing mesh has a series of lines that would be good to use, select those lines and use "Draw > Pattern > Duplicate". Just keep in mind that the new lines you are creating need to be on a new part (number) since you are creating a new part.

 

The "Examples" section in the documentation gives a few samples of creating geometry by hand. See "Ball in a Box with Body to Body Radiation Model".

 

As for the weld analysis, you might want to answer some of these questions for the group:

  1. What effects do you want to include in the analysis, if any. For example, include the twisting due to the thermal load during welding? Include the residual stress due to the actual welding? Or are you willing to assume the model begins in a stress-free state?
  2. What results do you want? Do you want to know if the weld is properly sized? Do you want results that you can use for a hand calculation to size or confirm the welds? Something else?
  3. What other input do you need to enter that would help us to understand your arrangement? Perhaps an image of an area around the spot weld would be helpful.

 

 

 

John Holtz, PE
Mechanical Engineer
Pittsburgh, PA

16.9 years experience with Simulation Mechanical
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Active Contributor tim
Active Contributor
tim
Posts: 37
Registered: ‎10-10-2012

Re: Simulating welds using 2d elements

04-17-2013 04:43 PM in reply to: AstroJohnPE
thanks John, i"ll try some of these things. Sorry about the link, it used to work. I'm really only after approximate weld stresses in the weld once a load is applied to the structure, so that I can size the weld.

It would be starting in a stress free state although one fine day, modelling the stresses due to welding could be handy.

Usually, I'm just interested in the stress in a fillet weld for static strength calcs, thats why a fast, economic 2d approximation appeals (large plate structures have lots of welds!).

My understanding from various codes is that for fatigue calcs in a fillet weld, we should be modelling with solid elements which i can do in inventor by modelling a separate part (i understand that the weld tool in inventor does not give useable welds in asm?).

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Active Contributor tim
Active Contributor
tim
Posts: 37
Registered: ‎10-10-2012

Re: Simulating welds using 2d elements

04-22-2013 08:45 AM in reply to: tim

John, the attachment below seems to have done the trick thanks to your tutorial hint.  Thanks so much!

 

My only question now (haha) is that if you look at the junction between the 2d plate weld (orange) and the grey plates, there is a mismatch between the mesh.  Can this be easily fixed?

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Active Contributor tim
Active Contributor
tim
Posts: 37
Registered: ‎10-10-2012

Re: Simulating welds using 2d elements

04-22-2013 08:46 AM in reply to: tim
Sorry, just realized there are no grey and orange parts in this image. You'll have to use your imagination!
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*Expert Elite*
AstroJohnPE
Posts: 547
Registered: ‎08-30-2012

Re: Simulating welds using 2d elements

05-01-2013 09:44 AM in reply to: tim

Hi Tim,

 

The one idea that comes to mind is this:

  1. Import the CAD model, but it is not necessary to mesh the model yet.
  2. Create the welds by hand.
  3. Select the nodes along the two edges of each weld.
  4. Add a Construction Vertex to each node.
  5. Mesh the CAD model.

The mesher should create a node at each construction vertex. Depending on the mesh size and what the automatic mesher feels like doing, there may be additional nodes between the nodes on the weld.

 

Another idea is to activate the "smart bonding". ("Setup > Model Setup > Parameters > Contact" tab.) This method uses mathematics to "bond" two parts that have a dissimilar mesh. Because of the mathematics, you can get some "hot spots" in the stress results depending on the mesh sized, etc.

John Holtz, PE
Mechanical Engineer
Pittsburgh, PA

16.9 years experience with Simulation Mechanical
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Active Member
cooperjer
Posts: 9
Registered: ‎02-28-2013

Re: Simulating welds using 2d elements

02-11-2014 12:59 PM in reply to: tim

Hello Tim,

 

I've also tried to use the 2d element method to simulate welds; however, I found that an error would occur preventing the sucessful convergence of the model during analysis.  I see that this post is from April 2013 and I suspect you have found a solution.  If so, what did you find to work well?

 

In this particular model I would have added a split surface on the 3D model at the intersection of the weld plane on both parts.  I would have also crated a sketch and a plane in the 3D model to act as the weld.  If the mesh of the weld still did not line up I would have added refinement points with a mesh size equal to the weld leg size.

 

Did the results of the weld seem reasonalbe and accurate?

 

Thank you.

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