Hi,
In getfem, to model the Isotropic linearized elasticity described as below equation (1) and (2), we can use the “add_isotropic_linearized_elasticity_brick”
or “add getfem::add_nonlinear_term” of the weak formulation.
(1)
(2)
Where 
But what if we have a slightly modified question of (2) as below (3)
Where the 
is the first order time derivative of strain.
Could you please advise how to model this? I try to add Grad_Dot_u in the
weak formulation, but the getfem won’t allow me.
Thank you very much
Regards
Zhenghuai Guo