[Getfem-users] Stiffness matrix for linear elasticity

[Roman Putanowicz]

Dear All, 

I am looking at function asm_stiffness_matrix_for_linear_elasticity.
There is code like this:
generic_assembly assem("lambda=data$1(#2); mu=data$2(#2);"
         "t=comp(vGrad(#1).vGrad(#1).Base(#2));"
         "M(#1,#1)+=sym(t(:,i,j,:,i,j,k).mu(k)"
                     "+ t(:,j,i,:,i,j,k).mu(k)"
                     "+ t(:,i,i,:,j,j,k).lambda(k))");
I cannot figure why this is written as above.
In the Navier's equation we have terms

     mu * u_i,jj + (mu+lambda)*u_j,ji

so I would expect  
the second and third components at mu and lambda, respectively, be the same.

I would really appreciate a hint on this as I have serious doubts in my
ability to juggle the tensor indices :-).

Best regards

Roman
-- 
Roman Putanowicz, PhD  < address@hidden  >
Institute for Computational Civil Engng (L-5)
Dept. of Civil Engng, Cracow Univ. of Technology
www.l5.pk.edu.pl, tel. +48 12 628 2569, fax 2034