The Non-linear Virtual Fields Method

The case of constitutive equations that non-linearly depend on their governing parameters is addressed in this chapter. Because of this non-linear nature, the sought parameters are now solution of a set of non-linear equations which has generally to be solved by minimizing a certain cost function defined with some quantities involved in the principle of virtual work. However, even though the resolution is not as simple as for the linear case, the main interest of the Virtual Fields Method is still to avoid the need to iteratively calculate the solution of problem 1 that exists for instance in the identification methods based on finite element models updating.