ezz = (Zz − σXx − σYy) / E, exy = Xy / μ.
(1)
If we introduce a quantity λ, of the same nature as E or μ, by the equation
λ = Eσ / (1 + σ)(1 − 2σ),
(2)
we may express the stress-components in terms of the strain-components by the equations
Xx = λ(exx + eyy + ezz) + 2μexx, Yz = μeyz,
Yy = λ(exx + eyy + ezz) + 2μeyy, Zx = μezx,
Zz = λ(exx + eyy + ezz) + 2μezz, Xy = μexy;
(3)