The following files were used in this problem:
usermat.F -- FORTRAN user material subroutine for the Neo-Hookean material.
sample_usr.dat -- Input file for a shear simulation with the Neo-Hookean user-defined material.
The stressstrain_usr.log output file is also included to verify
that the UserMat subroutine and custom executable are producing the
expected Neo-Hookean results.