Analysis of anisotropy and plastic spin effects on localization phenomena |
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Authors: | Maria K Duszek-Perzyna P Perzyna |
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Institution: | (1) Centre of Mechanics, Institute of Fundamental Technological Research, Polish Academy of Science, Swietokrzyska 21, 00-049 Warsaw, Poland, PL |
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Abstract: | Summary The main objective of the paper is the investigation of the influence of the anisotrophy and plastic spin effects on criteria
for adiabatic shear band localization of plastic deformation. A theory of thermoplasticity is formulated within a framework
of the rate-type covariance material structure with a finite set of internal state variables. The theory takes into consideration
such effects as plastic non-normality, plastic-induced anisotropy (kinematic hardening), micro-damage mechanism, thermomechanical
coupling and plastic spin.
The next objective of the paper is to focus attention on cooperative phenomena in presence of the plastic spin, and the discussion
on the influence of synergetic effects on localization criteria. A particular constitutive law for the plastic spin is assumed.
The necessary condition for a localized plastic deformation region to be formed is obtained. This condition is accomplished
by the assumption that some eigenvalues of the instantaneous adiabatic acoustic tensor vanish. A procedure has been developed
which allows us to discuss two separate groups of effects on the localization phenomenon along a shear band. Plastic spin,
spatial covariance and kinematic hardening effects are investigated at an isothermal process in an undamaged solid. In the
second case, an adiabatic process in a damaged solid is discussed when the spatial covariance terms and the plastic spin are
neglected. Here the thermomechanical coupling, micro-damage mechanism and kinematic hardening effects are examined. For both
cases, the criteria for adiabatic shear band localization are obtained in an exact analytical form.
Particular attention is focused on the analysis of the following effects: (i) plastic non-normality; (ii) plastic spin; (iii)
covariant terms; (iv) plastic strain-induced anisotropy; (v) micro-damage mechanism; (vi) thermomechanical couplings. Cooperative
phenomena are considered, and synergetic effects are investigated.
A discussion of the influence of the plastic spin, kinematic hardening and covariant terms on the shear band localization
conditions is presented. A numerical estimation of the effects discussed is given.
Received 24 April 1997; accepted for publication 23 December 1997 |
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Keywords: | plastic-induced anisotropy plastic spin localization micro-damage stress triaxiality |
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