The effect of strain recovery is taken into consideration in establishing a constitutive equation for metals at elevated temperatures. Internal state variables and Rice's flow potential are used in the representation. Growth law for the state variables is discussed and interpreted to be a more general form of the kinematic hardening condition. Yield condition is obtained from the flow law. Accordingly, the flow rule is established with the effect of the recovery mechanism, as a slightly general version of the time-independent theory with the kinematic hardening rule. In the discussion of the time-independent limit, the duration of time required for the inelastic strain to reach its saturated value is defined.

The effect of strain recovery is taken into consideration in ORNL efforts to establish unified constitutive equations for time-dependent plastic deformation for metals at elevated temperatures. Representation by internal state variables and Rice's flow potential are under consideration. Here the growth law for the internal state variables is discussed and interpreted in terms of a generalized form of the kinematic hardening condition of Prager. The yield condition is obtained from the flow potential representation of the inelastic strain rate. A consistency condition is derived from the yield condition and leads to a flow rule which assumes a slightly general form as compared with that of the classical plasticity due to the effect of strain recovery and the time-dependent property of the yield condition. Based on this representation, the time-independent limit is discussed. From a vanishing effect of recovery and a rate-independent limit for the yield condition at low temperature, this flow rule reduces to the well-known form of time-independent plasticity with a kinematic hardening condition. The duration of time (the characteristic time) required for the inelastic strain to reach its saturated value is defined for the inelastic loading condition. It provides the measure of a minimum duration of time which is required for a valid approximation made by the time-independent plasticity model.

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The Symposium was initiated in 1977 by Dr. M.G. CHABERT, Directeur des plans et programmes du C.E.T.I.M. His death, which occurred a few weeks before the Symposium, was deeply felt by all participants, who decided to dedicate this volume to his memory. The purpose, as set out by Dr. CHABERT, was to bring together people speaking the language of research and the language of industry in discussing problems of structural analysis. The Centre Technique des Industries M~caniques (C.E.T.I.M.) at Sen1is was considered a suitable place for organizing such a meeting. Modern structural analysis, aided by high speed computers, is mainly concerned with non-linear phenomena, such as plasticity, visco-plasticity, damage and fracture mecha nics. Scientists involved in research in this field also speak two different languages: that of material analysts and that of structural analysts. The Bureau of IUTAM had appointed the following Scientific Committee to implement the ideas proposed by Dr. CHABERT: J. LEMAITRE, Universite Paris VI, ENSET, Cachan, France Chairman J. HULT, Chalmers University of Technology, Gothenburg, Sweden, Co-Chairman G. CHABERT, Centre Technique des Industries M~caniques, Sen1is, France F.A. LECKIE, University of Illinois, Urbana, Illinois, USA G. MAIER, Istituto di Scienza e Technica delle Costruzi oni, Po1otechnico di Milano, Italy Z. MROZ, Polish Academy of Sciences, Warsaw, Poland G.S.