期刊
POLYMER
卷 54, 期 24, 页码 6599-6607出版社
ELSEVIER SCI LTD
DOI: 10.1016/j.polymer.2013.10.008
关键词
Nonlinear viscoelasticity; Stress relaxation; Constitutive model
Kim, et al. (Polymer, 54(15), 3949, 2013) recently reported on the unexpected relaxation behavior of an amorphous polymer in the T-g-region, where the rate of stress relaxation increased with deformation at a strain rate of 1.5 x 10(-4) s(-1) but decreased at a strain rate of 1.2 x 10(-5) s(-1). This inversion in the ordering with strain rate challenges the underlying structure of the existing nonlinear viscoelastic and viscoplastic constitutive models, where the key nonlinearity is a deformation dependent material clock. The nonlinear stress relaxation predictions of a recently developed stochastic constitutive model, SCM, (Medvedev, et al., J. Rheology, 57(3), 949, 2013) that acknowledge dynamic heterogeneity of the glass have been investigated. The SCM predicts the inversion in the ordering of the mobility with the loading strain rate as reported by the stress relaxation response. The change in perspective on the nonlinear viscoelastic behavior of glassy polymers engendered by the SCM is discussed. (C) 2013 Elsevier Ltd. All rights reserved.
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