Natural Lagrangian Strain Measures of the Non-Linear Cosserat Continuum

Definitions of the Lagrangian stretch and wryness tensors in the nonlinear Cosserat continuum are discussed applying three different methods. The resulting unique strain measures have several distinguishing features and are called the natural ones. They are expressed through the translation vector and either the rotation tensor or various finite rotation vector fields. The relation of the natural strain measures to those proposed in the representative literature is reviewed.