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Perouskii p r . , 35 MOSCOW E-112, U . S . S . R .Thermal phenomena in deformation of solids and flows are reviewed. Regularities common to all these phenomena as well as their characteristic features and consequences important for science and engineering are reported. The analogy between thermal phenomena in polymer mechanics and in chemical reaction is noted. NON-ISOTHERMAL DEFORMATION OF SOLID POLYMERSwhere c0 and uo are strain and stress amplitudes, respectively, with frequency w , 6 is the material characteristic which may be called the angle of mechanical loss. It is characteristic that 6 depends on temperature and frequency, the change of 6 in certain ranges of these parameters being sharp. On passing a region of relaxation (glass transition being the most important) the storage modulus drastically dccreases while mechanical losses are on the increase. A marked change in mechanical properties and, consequently in 6, is also observed at phase transition, if the temperature increase at deformation produces a similar transition.As d 2~ oscillations are performed per unit time the energyA generated per unit time in cyclic deformation is expressed by:where G" characterizes the mechanical properties of viscoelastic bodies and is termed a loss modulus. Data on 6 and G" for various polymers are numerous in the literatnre (see, for example, Ref. 1). It is important to point out thLat G" > 0, i.e., the process ofdeformation is always dissipative.Equations I and 2 are useful for both solid and rubbery substances. The temperature growth here, as in all processes considered, is controlled by heat transfer. The polymer constants for heat generation intensities essentially display a temperature dependence, at least on attaining certain temperatures. This mechanical phenomenon (2-5) is therefore analogous to an exothermal chemical reaction, the analogy extending to the presence of similar critical effects: a thermal explosion in chemical reactions appears analogous to the temperature runawa.y in cyclic deformation which leads to polymer degradation or its inability to resist distortion. In cyclic deformation, various regimes of change in the polymer temperature are possible (2, 6). When heat transfer is sufficiently intensive and the level of operating stresses is limited, heating leads to an equilibrium temperature which depends on the stress amplitude (7).A similar "steady" case, convenient in practice, is a mechanical analogue to an exothermal reaction whose kinetics differ greatly from that of the "thermal explosion" regime. It is reminiscent of a polymerization reaction with relatively weak thermal effects. The analogy is also traced in the termination of the process: (i) the reaction cornes to an end because the reactants are exhausted and (ii) polymer destruction follows.

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