THERMOMECHANICAL COUPLING EFFECTS NEAR DEFECTS IN INELASTIC BODIES* I. K. Senchenkov, Ya. A. Zhuk, and O. P. Chervinko UDC 539.376 Models used to study thermal effects in elastoviscoplastic and viscoelastic bodies deformed under monotonic and harmonic loading are considered. They allow us to obtain qualitative and quantitative information on the thermomechanical state of the material. Numerical results can be used in a nondestructive analysis and in predicting thermal fatigue failure of inelastic bodies. Introduction. It is well known that the deformation of materials is accompanied by thermal phenomena both reversible (thermoelastic effects [4]) and irreversible (heating due to internal dissipation [3, 17, 18]). The study of these phenomena is the basis for solution of applied problems such as thermographic control of macrodefects [6], simulation of ultrasonic welding of thermoplastic materials [1], evaluation of the performance of rubber shock absorbers, formulation of criteria of thermal fatigue failure of plastics [2], etc. Coupled thermomechanical processes are simulated with the help of thermodynamically consistent and experimentally validated models describing the thermoviscoplastic or thermoviscoelastic behavior of materials [17, 18]. Among such models are the generalized theories of viscoplastic flow, which are currently developed intensively [14, 15]. They employ the apparatus of internal variables for description of hardening, creep, relaxation, etc. The good agreement with the thermodynamics of irreversible processes [14, 16] makes them an efficient tool for modeling thermal phenomena in deformable viscoplastic bodies. The coupling of mechanical and thermal fields is manifested best under cyclic loading. In a quasisteady mode of vibrations, the current state of a material element does not depend on the loading history. This allows us to consider a simplified scleronomous formulation of the problem using the generalized complex characteristics of the material [8, 10, 11]. Another aspect of the problem is the necessity of allowing for the coupling occurring, first of all, in areas of increased stresses and strains. Among them are areas of stress concentration near foreign inclusions and pores, inhomogeneities of the surface, various defects, etc. The present study is devoted to thermomechanically coupled processes in viscoplastic and viscoelastic bodies having internal and surface defects and subjected to monotonous and cyclic loading. 1. Formulation of the Coupled Thermoviscoplastic Problem. The general equations of the coupled problem developed based on the Bodner–Partom model were derived in [8]. They include constitutive equations in the form of Hooke’s law for an isotropic material σ ~ = 2 G ( e ~ - º ~ p 29 + K v I ~    tr º ~ - 3 α (θ - θ 0 29    , (1.1) the flow rule S. P. Timoshenko Institute of Mechanics, National Academy of Sciences of Ukraine, Kiev. Translated from Prikladnaya Mekhanika, Vol. 37, No. 7, pp. 93–99, July 2001. Original article submitted November 8, 2000. 1063-7095/01/3707-0913$25.00 ©2001 Plenum Publishing Corporation 913 International Applied Mechanics, Vol. 37, No. 7, 2001 * Read at the 20th International Congress of Theoretical and Applied Mechanics (August 27 – September 2, 2000, Chicago, USA). This is a complete report. The congress transactions include only an abstract.