Eigenvalues of matrixevalued gridfunction

General
1

Hello

I want to obtain the principal stresses in this example ( 3D Solid Mechanics — NGS-Py 6.2.2404-2-ge6a630133 documentation (ngsolve.org)). I use the method explained here ( Principal Stresses in Elasticity - Main Forum / Old-Forum - do not post here - Netgen/NGSolve). But when I use:

with TaskManager():
    fesstress = MatrixValued(H1(mesh,order=3), symmetric=True)
    gfstress = GridFunction(fesstress)
    gfstress.Interpolate (Stress(Sym(Grad(gfu))))
gfstress.eig()

I get this error:

‘ngsolve.comp.GridFunction’ object has no attribute ‘eig’

Can someone please guide me how to obtain the principal stresses using eig()?

Best regards
Hamed

2

the function is Eig

3

Thanks a lot! It is working now