Did anyone developed a code/function to create Stiffness matrix of 8-Node Brick (Hexahedral) in Finite Element Analysis ?

I am developing a model, which will use 8-nodded brick elements. I am looking for an already built code/function, which can create its stiffness matrix.

Thanks in advance,

Answer 1

[Precise Simulation]

Q1 hexahedral elements are available and pre-defined with the FEA Toolbox. Once installed, the following code assembles a bilinear diffusion matrix with 8 node brick elements on a 5x5x5 unit cube:

    grid = blockgrid( 5, 5, 5 );

    form = [2 3 4; 2 3 4];   % Bilinear form specification.
    sfun = { 'sf_hex_Q1'; 'sf_hex_Q1' };   % Q1 elements.
    coef = 1;   % Bilinear form coefficient. 
    icub = 2;   % Quadrature rule/order.

    [vrowinds,vrowcols,vavals,n_rows,n_cols] = ...
        assemblea( form, sfun, coef, icub, grid.p, grid.c, grid.a);
    help assemblea   % See help text.

    A = sparse(vrowinds,vrowcols,vavals,n_rows,n_cols);   % Create sparse matrix.
    spy( A )

To see the element/basis function definition simply open the featool/ellib/sf_hex_Q1.m file in a text editor.

[Asif Arshid]

Thanks for sharing this resource. I downloaded and installed FEATool but I am unable to view/print the stiffness matrix of (any) single brick element, which was my objective.

Answer 2

[Precise Simulation]

For a single element you can just create a grid with one cell, for example using

grid = blockgrid(1);

in the example above.