Structural and Mechanical Aspects of Homogeneous and Non-Homogeneous Deformation in Solids
The aim of this work is to provide a basic experimental information about the physical nature of plastic deformation of crystalline bodies and to show the analytical workshop within which discreet micro-structural events of the plastic flow and the accomp
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A. Korbel Academy of Mining and MetaHurgy, Cracow, Poland
ABSTRACT The aim of this work is to provide a basic experimental information about the physical nature of plastic deformation of crystalline bodies and to show the analytical workshop within which discreet micro-structural events of the plastic flow and the accompanying effects may be accounted for. The attention is focused upon the slip which is a dominating micro-structural mechanism of deformation. The criterion for slip in the slip system is shown and discussed in terms of the effect of geometrical constraints upon the stress state and the choice of the operating system. The experimental patterns of slip during homogeneous and localised deformation are analysed in terms of the evolution of slip intrinsic features and the feedback between the mechanical, geometrical and structural aspects of slip in crystal. The analysis of the evolution of slip in crystals is supplemented by an essential information about the mechanism of slip and properties of dislocations. Interactions between dislocations of different slip systems are analysed from the point of view of the mechanisms of the strain hardening (formation of the obstacles network) and the softening mechanisms. The correlation between slip intrinsic features and global mechanical performance of crystals is made. It is shown that the change from a stable into an unstable mode of plastic flow is caused by the change of slip from a ,fine slip" into a ,coarse slip" in single crystals and into shear bands in polycrystals. The latter is shown to take the origin in the mechanical instability of the obstacles network. The :fuctors controlling the evolution of slip and responsible mechanisms are discussed in terms of the slip geometry and interactions between dislocations. P. Perzyna (ed.), Localization and Fracture Phenomena in Inelastic Solids © Springer-Verlag Wien 1998
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A. Korbel
1. INTRODUCTION If a body is subjected to the action of balanced external forces one can say that it is under load. The behaviour (reaction) of a body during loading and under the load depends upon the material of which the body is made and upon the loading conditions (loading rate, temperature). It may concern the change of of a body shape as well as its internal structure. RESPONSE OF A BODY (MATERIAL) TO APPLIED LOAD
Action:
Reaction:
Change of shape
Load
Analytical description :
a (stress)
Change of structure
e (deformation) & (strain) and ro rotation)
vanous structure elements
.!Relation(s) ) Constitutive Law:
properties
a
= f(&); and (properties )
f(&) =
=
(properties),
(mechanism of structural changes)
Regardless, however, of the kind of material and loading conditions the response of the material to the applied load shows some characteristic features. They become revealed with increasing stress, so that three physically different forms of the response (reaction) of the body to the load (or more precisely to the scheme of loading) can be identified. They are classified and analysed in terms of the mate
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