Discussion of thermomechanics on the basis of frame invariance of physical law

In continuum mechanics it is not clear what principle is equivalent to the principle of material frame indifference (PMFI). In the present paper, it is first shown that not only mechanical conservation laws but also frame transformation laws of constitutive quantities and source quantities are simultaneously derived for a changing frame under the assumption that the forms of the first and second laws of thermodynamics are invariant for changes of frame. Next, considering whether the reverse proposition is true or false, an explanation of the relationship between the PMFI and the invariance of the laws of thermodynamics for changes of frame is given. Then the bases of the PMFI are determined, clarifying the relationship between the PMFI and the frame invariance of the Clausius-Duhem inequality. Moreover, it is indicated that this method, which enables derivation of conservation laws using changes of frame, is equivalent to both the principle of virtual power and the method of Green and Rivlin.