Hi everyone,

I am using FEniCS to solve an elasto-viscoplastic problem, and would be nice to use a constitutive law which includes the Hencky logarithmic strain. So, for the implementation, it would be needed to calculate the logarithm of a matrix (the right stretch tensor, V).

As I have seen in UFL documentation, the logarithm included there is only valid for scalar functions. Is it possible to directly calculate the logarithm of a matrix (which will contain unknowns of the problem) in FEniCS? Is there a way to calculate the eigenvalues and eigenvectors of the matrix so then the logarithm will be easier to calculate?

Thanks in advance.