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linhmail

How to creat 2D element from nodes

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hi, everyone
i'm a beginner in Hypermesh. Recently, i've encountered a problem in 2D meshing. I  have 3 nodes (like in the photo below). I want to create a trias element from them, or creat some lines from them, so i go to Mesh - create - 2D element - Element. I chose those 3 nodes, but no element was created!!!
So could anyone tell me where i was wrong and how to fix this, thank you very much!!

 

Capture.PNG

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hi Tinh. I did exactly what u told, but after i choose 3 nodes, there is a message: select mid-side nodes, and after i click Create, there is a message: select conner nodes. And nothing was created
Help me!!

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10 hours ago, linhmail said:
8 hours ago, Q.NGUYEN-DAI said:

Maybe your mesh is "tria6" (2nd order), not "tria3". So in this case, you need define 6 nodes.

 

thanhk u Q.NGUYEN_DAI, it's ok now :D

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9 hours ago, Q.NGUYEN-DAI said:

Maybe your mesh is "tria6" (2nd order), not "tria3". So in this case, you need define 6 nodes.

@Q.NGUYEN-DAI, i just run into the same problem, when i deleted 1 element and i want to creat a new element to patch, i could not create any element. when i choose the first 2 nodes, they are highlighted, but when i choose the 3rd nodes, all nodes are not highlighted anymore. so no element was created. I've attached my model below, could u take a look and help me know what exactly the problem is!! Thank you

nap_lung_surface_deviation.hm

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Your mesh is 1st order, so for surface mesh, you need only 3 nodes for each element.

Attention 1: when you create element, have a look at CURRENT component, because new elements will be created on that.

Attention 2: Your current mesh is not so good. For TET4 meshing, you have to make finer mesh to get better results.

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For shell-like structure like yours, if you want to work with TET4 solid element, you need at least 3~4 elements on thickness to have acceptable results.

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but the thickness of my model is  <2mm, very thin, as my plan, i will mesh the shell with second order trias element, then use Mesh - Tetra Mesh to make solid, will it be ok???

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Even with 2nd order element, you have to make some elements on thickness. Only one element / thickness can not give you acceptable results.

Why not calculate with shell elements?

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On 4/17/2016 at 11:57 AM, Q.NGUYEN-DAI said:

Even with 2nd order element, you have to make some elements on thickness. Only one element / thickness can not give you acceptable results.

Why not calculate with shell elements?

 

I agree, I would calculate with shell elements.

 

However, I have tested this myself. I created a simple model of a cantilever beam and compared different solid meshes with the max output von Mises stress result.

 

Via hand calculations (baseline): Stress = 600 MPa

1x HEX8 element through thickness: Stress = 565 MPa

2x HEX8 element through thickness: Stress = 604 MPa

1x TET4 element through thickness: Stress = 154 MPa

2x TET4 element through thickness: Stress = 387 MPa

1x TET10 element through thickness: Stress = 623 MPa

 

The results are a bit iffy because the max stress is located near the constraints (I should've done this using a 3-point bending model...) You can clearly see here that TET4 elements are bad at calculating stresses through the thickness due to bending. However the TET10 element (with midside nodes) is a lot better.

 

Still, for best results calculating stresses through the thickness I would be using HEX elements (where possible) for thick components and QUAD elements for thin shell components.

Mrt, linhmail and Rahul R like this

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On ‎6‎/‎26‎/‎2018 at 6:55 AM, Karthik_kiran_solver said:

Hi

I have the same problem. 

Tried creating the element... 

But when I select the third node, the nodes are just unhighlighted and no element is created.

So what should I do? 

 

15299878278672112880761.jpg

it will be great if you can send full screenshot... but for now I am assuming that your current component is different than where you are adding element. So please try with setting current component. For changing current component click on "set current component" and choose appropriate(find attachment).
 

Unbenannt.PNG

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