Basic question

[Caro-Bretelle]

Hello
in most of hyperelastics model, the true stress is expressed via dev(b*). In the case of uniaxial tensile test (for exemple Neohookeen model) the Cauchy stress tensor has three diagonal components ! Only one describes this test! Can someone can help me ?
Thanks a lot

[Jorgen]

I don't understand your question. Can you explain more?

-Jorgen