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dc.contributor.authorSweeney, John
dc.contributor.authorO'Connor, C.P.J.
dc.contributor.authorSpencer, Paul E.
dc.contributor.authorPua, H.
dc.contributor.authorCaton-Rose, Philip D.
dc.contributor.authorMartin, P.J.
dc.date.accessioned2020-12-03T09:05:23Z
dc.date.accessioned2020-12-14T08:52:03Z
dc.date.available2020-12-03T09:05:23Z
dc.date.available2020-12-14T08:52:03Z
dc.date.issued2012-11
dc.identifier.citationSweeney J, O'Connor CPJ, Spencer PE et al (2012) A material model for multiaxial stretching and stress relaxation of polypropylene under process conditions. Mechanics of Materials. 54: 55-69.en_US
dc.identifier.urihttp://hdl.handle.net/10454/18228
dc.descriptionNoen_US
dc.description.abstractPolypropylene sheets have been stretched at 160 °C to a state of large biaxial strain of extension ratio 3, and the stresses then allowed to relax at constant strain. The state of strain is reached via a path consisting of two sequential planar extensions, the second perpendicular to the first, under plane stress conditions with zero stress acting normal to the sheet. This strain path is highly relevant to solid phase deformation processes such as stretch blow moulding and thermoforming, and also reveals fundamental aspects of the flow rule required in the constitutive behaviour of the material. The rate of decay of stress is rapid, and such as to be highly significant in the modelling of processes that include stages of constant strain. A constitutive equation is developed that includes Eyring processes to model both the stress relaxation and strain rate dependence of the stress. The axial and transverse stresses observed during loading show that the use of a conventional Levy-Mises flow rule is ineffective, and instead a flow rule is used that takes account of the anisotropic state of the material via a power law function of the principal extension ratios. Finally the constitutive model is demonstrated to give quantitatively useful representation of the stresses both in loading and in stress relaxation.en_US
dc.language.isoenen_US
dc.subjectConstitute equationen_US
dc.subjectLarge deformationsen_US
dc.subjectPolypropyleneen_US
dc.titleA material model for multiaxial stretching and stress relaxation of polypropylene under process conditionsen_US
dc.status.refereedYesen_US
dc.date.application2012-06-27
dc.typeArticleen_US
dc.type.versionNo full-text in the repositoryen_US
dc.date.updated2020-12-03T09:05:26Z


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