how to create four node quadliteral mesh ?

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  • Last Post 22 December 2018
mehmetbaki posted this 20 December 2018

I have a problem about creating mesh using four node quadliteral element. I'm very new about ansys. So I want to learn how to make mesh for my problem in picture below

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peteroznewman posted this 20 December 2018

mehmetbaki,

For a 2D surface like this, the mesher algorithm covers the face with triangles then automatically converts every pair of triangles it can into a quadrilateral element. That means there may be some triangles left that could not be paired. It is okay to have some triangle elements in your mesh.

If you want no triangles, then the labor intensive method to do that is to slice the surface up until you have only four-sided faces. The sides of the face can be curved. For example a vertical and horizontal slice through the 0, a slice along the right edge of the 1 and another vertical slice just a little to the right of the 0 will create many four-sided faces. There would be more work to slice up the rest of the 1, but you get the idea. As I said above, this is not necessary.

What is far more useful is to make an initial mesh, solve the model and look at the results. In areas of the result that have a high gradient in the solution quantity, refine the mesh to smaller elements in that local region.

What kind of analysis do you want to do?

Regards,
Peter

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peteroznewman posted this 21 December 2018

Do you want three faces with a mesh inside the 1 and 0 or do you want one face meshed with no mesh inside the 1 and 0?

Three faces:

One face:

Why can't you have a triangle element? How much work are you willing to do to have all quad elements?

Here is one mesh.

Here is the Mesh Metrics:

There are 1650 elements in the mesh.  The graph above binned them by their skewness metric.

Here you can count the number of triangles, there are 14 triangles out of 1650 elements.

Now if you look at the mesh data, ANSYS used 1650 PLANE182 elements.

The reason is that there is a degenerate quad that is in the shape of a triangle, they just put two nodes of the quad at the same location.

 Can you use that trick?

Regards,
Peter

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mehmetbaki posted this 21 December 2018

I just want to have node numbers and their location about x and y axis and topology array of only quad elements. ı want to import this excel files into matlab for my project but I cant. please help me about this? http://bit.ly/my_dxf_file here is my dxf file. just need mesh picture and excel files

mehmetbaki posted this 22 December 2018

ı want that you meshed one like this below.  node orders need to like this to reduce k matrix. this is my first ansys application. I need to see nodes and only four node quad elements like this. please send me picture like this and excel files. and project that show node numbers and quad elements and topology array and node location as I have mentioned. here is my e mail mehmetbaki.123@gmail.com

peteroznewman posted this 22 December 2018

 After meshing, an analysis system must be defined, then you can Write Input File, which is attached.

This is what the input file looks like where the node coordinates are defined...

 

/com,*********** Nodes for the whole assembly ***********

nblock,3,,1727

(1i9,3e20.9e3)

        1     0.000000000E+00     0.000000000E+00     0.000000000E+00

        2     0.000000000E+00     3.000000000E+02     0.000000000E+00

        3     1.000000000E+03     0.000000000E+00     0.000000000E+00

        4     1.000000000E+03     3.000000000E+02     0.000000000E+00

        5     4.876923077E+02     5.000000000E+01     0.000000000E+00

        6     4.876923077E+02     2.500000000E+02     0.000000000E+00

        7     4.492307692E+02     5.000000000E+01     0.000000000E+00

        8     4.568429487E+02     2.500000000E+02     0.000000000E+00

        9     4.005128205E+02     1.987179487E+02     0.000000000E+00

       10     4.005128205E+02     1.602564103E+02     0.000000000E+00

This is what the input file looks like where the elements are defined...

 

/com,*********** Elements for Body 1 "Surface" ***********

et,1,182

keyo,1,3,3

eblock,19,solid,,1448

(19i9)

        1        1        1        1        0        0        0        0        4        0        1     1566     1154     1570     1570

        1        1        1        1        0        0        0        0        4        0        2      833      787      716      716

        1        1        1        1        0        0        0        0        4        0        3     1170      725     1169     1169

        1        1        1        1        0        0        0        0        4        0        4     1476     1122     1123     1123

        1        1        1        1        0        0        0        0        4        0        5      833     1166     1167     1167

        1        1        1        1        0        0        0        0        4        0        6     1166        9      250      250

        1        1        1        1        0        0        0        0        4        0        7      998      999     1119     1119

        1        1        1        1        0        0        0        0        4        0        8     1079      924     1121     1121

        1        1        1        1        0        0        0        0        4        0        9     1489       13     1399     1399

        1        1        1        1        0        0        0        0        4        0       10     1162     1163     1405     1405

        1        1        1        1        0        0        0        0        4        0       19       45       44     1140      623    

You can see that element #6 uses node #9 on one of its corners, and that element #6 is a triangle because it uses the same node number twice. There are 18 triangles in this mesh (different than the one above) and at element #19, that is a quad element since it has four different nodes on the four corners.

Node #9 is the bottom left corner of the 1.

As I said above, if you divide up the surface into four-sided pieces, then you can eliminate all triangles. Note that the faces can have curved edges. Please reply with a map that divides that surface into four-sided pieces.

Regards,

Peter

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