[Hisham]

Dear "oh dear"

How can I define a 4th rank tensor in OF?

I need to write the incremental stress-strain relationship for, say, an elastic material as (tensorial notation):

Sigma = E: Epsilon

; E(ijkl) = (B-2G/3) dij dkl + G (dik djl + dil djk)

E --- isotropic elastic coefficient 4th rank tensor
B,G ---- scalars
d ----- Kronecker delta(s) ??????? (how to implement them dij/dkl/etc.)

Lastly, how to write this equation???

Best regards
Hisham