How to export FEMesh?

Dear Matlab Community,

how can I export a FEMesh created in Matlab?

Alternatively, it would also help me to just regularise the imported stl-file and then export it again as a stl-file.

Here is my code so far:

meshSize=0.05;
meshGrowthRate=1.1;
meshOrder='quadratic';

% import any unordered stl-file
model = createpde(1);
importGeometry(model,'geometry.stl');

% generation of a regular FE mesh
mesh=generateMesh(model,'Hmax',meshSize,'Hmin',meshSize,'Hgrad',meshGrowthRate,'GeometricOrder',meshOrder);
pdeplot3D(model)

I am very grateful for any help.

Best regards,

FG

Answer 1

[Wan Ji]

The mesh is now the field of model

you can get mesh by

Mesh = model.Mesh; 
% nodes are obtained by
Nodes = Mesh.Nodes; % d-by-n matrix where d is the number of dimension
% elements are obtained by
Elements = Mesh.Elements; % s-by-m matrix where s is the number of nodes of one element

[Wan Ji]

I donot know what kind of format you want to export the mesh. Now that you have got the nodes and elements of this mesh. You can do anything you like to perform the fem analysis.

[Fabian Günther]

I would like to export the mesh in order to import it afterwards in another FE program (Abaqus), edit it and finally solve it there.

However, it would also be possible, if the entire model cannot be exported, to export only the surface as an .stl file.

[Wan Ji]

Use the following function to write to an abaqus inp file

function toinp(Mesh, fileName, ElementType)
Mesh.Elements = Mesh.Elements';
Mesh.Nodes = Mesh.Nodes';
    if(~strcmpi(fileName(end-3:end),'.inp'))
        fileName = [fileName,'.inp'];
    end
    while(exist(fileName,'file'))
        s = input('File name already exists, are you sure to overwrite it (1 for yes and 0 for no)?');
        switch s
            case {'yes', 1}
                break;
            otherwise
                fileName = input('Please input a new file name:');
        end
    end
    
    fid = fopen(fileName,'wt');
    fprintf(fid,'*HEADING\n');
    fprintf(fid,'%s\n**\n',fileName);
    fprintf(fid,'*Node\n');
    for i = 1:1:size(Mesh.Nodes,1)
        ndim = size(Mesh.Nodes,2);
        fprintf(fid, ['%d',repmat(',%f', 1, ndim),'\n'], i, Mesh.Nodes(i,:));
    end
    switch lower(ElementType)
        case{'c2d3','c2d4','c2d6','c2d8'}
            eType = ElementType;
            eType(2:3) = 'ps';
        otherwise
            eType = ElementType;
    end
    fprintf(fid,'*Element, Type=%s\n', upper(eType));
    for i = 1:1:size(Mesh.Elements,1)
        nenode = size(Mesh.Elements,2);
        fprintf(fid,['%d',repmat(',%d', 1, nenode),'\n'], i, Mesh.Elements(i,:));
    end
    fclose(fid);
end

For example

toinp(Mesh, 'myinp.inp', 'c3d10')

[Fabian Günther]

Thank you for this powerful function!

Unfortunately, I get the error message when I use it:

Unable to set the 'Elements' property of class 'FEMesh' because it is read-only.

Do you have any idea how I can fix this?

[Wan Ji]

Mesh = model.Mesh; 
% nodes are obtained by
Nodes = Mesh.Nodes; % d-by-n matrix where d is the number of dimension
% elements are obtained by
Elements = Mesh.Elements; % s-by-m matrix where s is the number of nodes of one element
myMesh.Nodes = Nodes;
myMesh.Elements = Elements; % Now myMesh is a struct, not femMesh class
toinp(myMesh, 'myinp.inp', 'c3d10')

[Wan Ji]

Or just have a little modification on the function

function toinp(MeshIn, fileName, ElementType)
Mesh.Elements = MeshIn.Elements';
Mesh.Nodes = MeshIn.Nodes';
if(~strncmpi(fileName(end:-1:1),'pni.',4))
    fileName = [fileName,'.inp'];
end
while(exist(fileName,'file'))
    s = input('File name already exists, are you sure to overwrite it (1 for yes and 0 for no)?');
    switch s
        case {'yes', 1}
            break;
        otherwise
            fileName = input('Please input a new file name:','s');
    end
end
if(~strncmpi(fileName(end:-1:1),'pni.',4))
    fprintf('File name not with suffix ''.inp'', program will add it\n')
    fileName = [fileName,'.inp'];
end
fid = fopen(fileName,'wt');
fprintf(fid,'*HEADING\n');
fprintf(fid,'%s\n**\n',fileName);
fprintf(fid,'*Node\n');
for i = 1:1:size(Mesh.Nodes,1)
    ndim = size(Mesh.Nodes,2);
    fprintf(fid, ['%d',repmat(',%f', 1, ndim),'\n'], i, Mesh.Nodes(i,:));
end
switch lower(ElementType)
    case{'c2d3','c2d4','c2d6','c2d8'}
        eType = ElementType;
        eType(2:3) = 'ps';
    otherwise
        eType = ElementType;
end
fprintf(fid,'*Element, Type=%s\n', upper(eType));
for i = 1:1:size(Mesh.Elements,1)
    nenode = size(Mesh.Elements,2);
    fprintf(fid,['%d',repmat(',%d', 1, nenode),'\n'], i, Mesh.Elements(i,:));
end
fclose(fid);
fprintf('Output Inp File Successfully!\n')
end

Then use

Mesh = model.Mesh;
toinp(Mesh, 'myinp.inp', 'c3d10')

It is OK now

[Fabian Günther]

Thanks alot man!