An Assessment of Nonlinearly Viscoelastic Constitutive Models for Cyclic Loading: The Effect of a General Loading/Unloading Rule

• Published in: Mechanics of time-dependent materials Vol. 9; no. 4; pp. 79 - 98
• Main Authors: Xia, Zihui, Shen, Xinghe, Ellyin, Fernand
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer 01.12.2005
• Subjects: Applied sciences; Exact sciences and technology; Fundamental areas of phenomenology (including applications); Inelasticity (thermoplasticity, viscoplasticity...); Mechanical properties; Physical properties; Physics; Polymer industry, paints, wood; Properties and testing; Solid mechanics; Static elasticity (thermoelasticity...); Structural and continuum mechanics; Technology of polymers; Constitutive equation; Ratchetting; Mean field approximation; ratcheting strain; viscoelastic constitutive model; Epoxy resin; Polymer; loading/unloading; Experimental study; Modeling; Stress relaxation; Cyclic load; mean stress relaxation; cyclic loading; Non linear effect; epoxy polymer
• ISSN: 1385-2000; 1573-2738
• DOI: 10.1007/s11043-006-9004-3

Predicting the unloading and/or cyclic deformation behavior of polymers is a challenge for most nonlinear viscoelastic constitutive models. Experimental data of an epoxy polymer under uniaxial loading/unloading and two other types of cyclic loadings are used to assess the predictive capabilities of three types of nonlinear viscoelastic models. A general loading/unloading criterion and a switching rule, proposed recently by the authors, are further modified and incorporated into each of the three models. For each model, predictions by both the original formulations and that incorporating the proposed loading/unloading rule are compared with the test data. It is clearly shown that such a rule is essential to correctly simulate the unloading and cyclic loading behavior of polymers. By introducing such a rule to constitutive models, the quantitative predictions can be improved, to various degrees of success, with respect to cyclic deformation features such as ratcheting under cyclic loading with a mean stress and stress relaxation under cyclic straining with a mean strain.