how to find out node coordinates for a simple quad element?

I want to know how to find out the node co-ordinates for a simple shell element?

Answer 1

[Wan Ji]

Hi, friend! It seems you are studying the finite element method.

For fem analysis, two important things for preprocessing are nodes and elements.

Usually nodes are stored in a n-by-d matrix (n is the number of nodes, d is the dimension), for example

nodes = [0,0,0; 1,0,0; 1,1,0; 0,1,0; 0,2,1; 1,2,1];

elements are stored in a m-by-s matrix, in a quad element with 4 nodes, s=4, and m is the number of elements. Elements record the node identity and their arrangement in an element. Here two elements are

elements = [1,2,3,4; 3,4,5,6];

IF YOU want show the two shell elements, then use patch function

patch('vertices', nodes, 'faces', elements, 'facevertexcdata', nodes(:,3),'facecolor','interp')
colormap(jet)

IF you want get the nodes of the second elements, just do

ecoor = nodes(element(2,:),:)
ecoor =

     1     1     0
     0     1     0
     0     2     1
     1     2     1

Here 2 represents the second element.

Answer 2

[Fabio Freschi]

It depends on your data structure: now your qeustion is rather vague.

Assuming that you have the node coordinates in the Nx3 array P and the connectivity matrix in the the Mx4 array T and you want to know the node coordinates of the element idx, you may write

Pelem = P(T(idx,:),:);

[S Priya]

I have only the relations between the x, y and z coordinates for the shell facet (quad) element. what would be the further steps for carrying the fem analysis?