Transcending dissipative force proportional to velocity in internal friction and in crack propagation: the role of phonon emission Original Research Article

After summarizing simple models of (a) internal friction and (b) crack propagation, in which essential input is a dissipative force which is a constant times velocity , where u is the displacement, their consequences are brought into contact with processes (a) and (b) when it is known from experiment that phonon emission constitutes a major damping mechanism. Same experiments on both (a) and (b) are noted, where such radiation force is important. One must expect then that it becomes essential to transcend damping which is assumed to be proportional to