Journal of Materials Science

, Volume 7, Issue 1, pp 52–63 | Cite as

The plastic flow of isotropic polymers

  • P. B. Bowden
  • J. A. Jukes


This paper describes a study of the plastic stress-strain behaviour of a number of polymeric materials deformed under different states of stress. Tests were carried out on samples of polymethyl methacrylate, polystyrene, polyethylene terephthalate, polyvinyl chloride, epoxy resin, and high density polyethylene. The extent to which plasticity theory can be used to describe the observed behaviour has been considered and it is concluded that in spite of their viscoelastic behaviour and the large elastic strains prior to yield plasticity theory can be applied provided that stresses are expressed as true stresses at yield. The most appropriate yield criterion for PMMA is a von Mises criterion modified so that the yield stress varies linearly with the hydrostatic component of the stress tensor. For PS a modified Tresca criterion is more appropriate.

The inclination of the bands of local shear deformation that form in these materials is not at 45° to the directions of principal stress. In most cases this apparent deviation appears to be entirely due to elastic recovery on unloading, but for polystyrene there is an extra deviation probably due to the occurrence of small plastic volume changes during yield.


PMMA Polymethyl Methacrylate High Density Polyethylene Terephthalate Polyvinyl Chloride 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


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Copyright information

© Chapman and Hall Ltd 1972

Authors and Affiliations

  • P. B. Bowden
    • 1
  • J. A. Jukes
    • 1
  1. 1.Metallurgy DepartmentUniversity of CambridgeUK

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