Frame indifference (Q1195198)

The bases of the author's arguments are that he knows (sic!) the laws of material frame indifference to be true for Navier-Stokes fluids and elastic solids, therefore true for all if not to be material dependent. Thus if \(\sigma\) and \(\bar\sigma\) are the stresses in two frames, one rotating with respect to the other, then it must be that \(\bar\sigma=R\sigma R^ T\); \(RR^ T=I\). As is well known this relation is necessary and sufficient to guarantee that surface tractions are invariant under rotations of frame, and most accept this as axiomatic. The introductory remarks on constitutive relations derived from the kinetic theory of gases are based on incomplete and outdated references.