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Title: Endochronic theory of dynamic viscoplasticity

Abstract

This report summarizes the work completed on a project concerned with engineering models in dyanmic plasticity. The concept of the endochronic theory of viscoplasticity and its subsequent improvement are discussed briefly. Applications and extensions of the theory to various dynamic problems are presented. In particular, the strain-rate effect in the improved endochronic theory and its application to wave propagation problems are discussed. Comparing the numerical results with other calculations and experimental data, it appears that endochronic theory provides a promising representation of realistic material behavior. At the same time endochronic theory is often numerically more efficient than other formulations.

Authors:
Publication Date:
Research Org.:
Argonne National Lab., IL (USA)
OSTI Identifier:
5882705
Report Number(s):
ANL-83-59
ON: DE83017531
DOE Contract Number:
W-31-109-ENG-38
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 36 MATERIALS SCIENCE; METALS; DEFORMATION; PLASTICITY; DYNAMIC LOADS; IMPACT SHOCK; STRAIN RATE; WAVE PROPAGATION; ELEMENTS; MECHANICAL PROPERTIES; 656000* - Condensed Matter Physics; 360103 - Metals & Alloys- Mechanical Properties

Citation Formats

Lin, H.C. Endochronic theory of dynamic viscoplasticity. United States: N. p., 1983. Web. doi:10.2172/5882705.
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Lin, H.C. Endochronic theory of dynamic viscoplasticity. United States. doi:10.2172/5882705.
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Lin, H.C. Wed . "Endochronic theory of dynamic viscoplasticity". United States. doi:10.2172/5882705. https://www.osti.gov/servlets/purl/5882705.
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@article{osti_5882705,
title = {Endochronic theory of dynamic viscoplasticity},
author = {Lin, H.C.},
abstractNote = {This report summarizes the work completed on a project concerned with engineering models in dyanmic plasticity. The concept of the endochronic theory of viscoplasticity and its subsequent improvement are discussed briefly. Applications and extensions of the theory to various dynamic problems are presented. In particular, the strain-rate effect in the improved endochronic theory and its application to wave propagation problems are discussed. Comparing the numerical results with other calculations and experimental data, it appears that endochronic theory provides a promising representation of realistic material behavior. At the same time endochronic theory is often numerically more efficient than other formulations.},
doi = {10.2172/5882705},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Jun 01 00:00:00 EDT 1983},
month = {Wed Jun 01 00:00:00 EDT 1983}
}
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Technical Report:
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DOI:  10.2172/5882705
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  • ;
    The constitutive equations for strain-hardening metallic materials with strain-rate effects are presented in the framework of the endochronic theory of viscoplasticity using the improved intrinsic time measure. The derived constitutive c are then applied to the viscoplastic wave-propagation problem of a thin-walled tube subjected to impact loading. Numerical results using the improved endochronic time and theoretical results using conventional plasticity together with the experimental results are compared. It is shown that they are in good agreement qualitatively. In summary, the improved intrinsic time measure does predict both loading and unloading behavior in accordance with the observed phenomena.

  • The endochronic viscoplasticity model is presented, and the criteria for general problem analyses are discussed. Two approaches are then developed for inclusion of this model in nonlinear finite element codes. One approach includes reformulating the stiffness matrix for solution by iteration, and the other approach does not. Also, the uniaxial tension problem is studied, and the problems encountered with the use of this model are stated. Finally, recommendations are presented to check the basic postulates used to develop this model.

  • The endochronic theory of plasticity originated by Valanis has been applied to study the axially symmetric motion of circular cylindrical thick shells subjected to an arbitrary pressure transient applied at its inner surface. The constitutive equations for the thick shells have been obtained. The governing equations are then solved by means of the near-characteristics method.

  • As a part of an ongoing evaluation of the endochronic theory of plasticity to assess its utility in describing the dynamic inelastic response of shipping containers to several accident loads, the study explores recently raised questions concerning the numerical stability and uniqueness associated with practical application of the theory.

  • ; ;
    A gradual accumulation of inelastic strain can be most conveniently described in terms of the so-called intrinsic time, whose increment depends on the time increment as well as the strain increments. This approach, which gives a particularly simple description of irreversibility of strain at unloading and cyclic loading, was previously developed for metals and is extended herein to concrete by introducing the hydrostatic pressure sensitivity of inelastic strain, the inelastic dilatancy produced by deviator strains, and the strain-softening tendency at high stress. Failure envelopes are obtained as a collection of the peaks of stress-strain diagrams. By comparison with experimental datamore » from the literature, it is demonstrated that the proposed model predicts quite closely: stress-strain diagrams for concretes of different strength; uniaxial, biaxial and triaxial stress-strain diagrams and failure envelopes; failure envelopes for combined torsion and compression, lateral strains and volume expansion in uniaxial and biaxial tests; the behavior of spirally confined concrete; hysteresis loops or repeated high compression; cyclic creep up to 10/sup 6/ cycles; the strain rate effect; the decrease of long time strength; and the increase of short-time strength due to low stress creep.« less