A large and growing number of original papers on both the experimental and the theoretical aspects of stress wave propagation is appearing in the scientific literature, and two international conferences solely concerned with the subject have been held during the last five years. The purpose of this paper is to review recent experimental and theoretical advances in the propagation of deformation waves of arbitrary shape through elastic and anelastic solids, and also to attempt to outline the problems on which present efforts are being directed and to predict probable lines of future development.

Stress Waves in Solids

Publisher Summary The fundamental assumption of all theories of plasticity—that of time independence of the equations of state—makes simultaneous description of the plastic and rheologic properties of a material impossible. I t is well-known that in many practical problems, the actual behaviour of a material is governed by plastic as well as by rheologic effects. It can even be said that for many important structural materials, rheologic effects are more pronounced after the plastic state has been reached. Every material shows more or less pronounced viscous properties. In some problems, the influence of viscous properties of the material may be negligible, while in others, it may be essential. Both sciences—plasticity and rheology—are concerned with the description of important mechanical properties of structural materials. Each of them has created its own methods of investigation and has developed within the framework of certain assumptions which, unfortunately, cannot always be satisfied in reality. The results of rheology are confined to cases where plastic strain is of no decisive importance.

Fundamental Problems in Viscoplasticity

: The principal im is to generalize h one- im ion l con itutive equ tions for r te-sensi ive plastic materials to general sta s of s ress. T HE DYNAMIC L YIELD CONDITIONS FOR LASTIC, VISCO-PLASTIC MATERIALS ARE DISCUS ED A D NEW R L XATION FUNCTIONS ARE INTRODUCED. S OLUTION OF THE RELAXATION EQUATIONS FOR SUCH MATERIALS ARE GIVEN. (Author)

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The Constitutive Equations for Rate Sensitive Plastic Materials

The paper is concerned with the structure of multiaxial stress-strain relations in timedependent metal plasticity, as for transient creep and rate sensitive yielding. First. a general kinematical relation is developed between the macroscopic inelastic strain tensor and microstructural slip displacements, as modeled either by continuum shearing on crystallographic planes of individual grains or by the motion of discrete dislocation lines. It is assumed that at any given slipped state, the rate of slipping on a particular system is governed by the resolved shear stress on that system (or by the local \"forces\" on dislocation lines). 'This leads to the primary result of the paper: Components of the macroscopic inelastic strain rate tensor are deriz!able, at each instant in the course of deformation, from a potential function of stress, General features of the flow potential surfaces in stress space are discussed, and some specific functional forms are examined, Linear viscoelasticity and tirre-independent plasticity are developed as limiting cases of the flow potential formulatic!, and the appropriateness of a potential function for stationary creep is discussed,

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L. E. Malvern

Papers

The Propagation of Longitudinal Waves of Plastic Deformation in a Bar of Material Exhibiting a Strain-Rate Effect