Phenomenological formulation of viscoplastic constitutive equation for polyethylene by taking into account strain recovery during unloading

Autor: Yukio Sanomura, Mamoru Mizuno
Rok vydání: 2008
Předmět:
Zdroj: Acta Mechanica. 207:83-93
ISSN: 1619-6937
0001-5970
DOI: 10.1007/s00707-008-0111-x
Popis: A viscoplastic constitutive equation for polyethylene that properly describes significant strain recovery during unloading was proposed. The constitutive equation was formulated by combining the kinematic hardening creep theory of Malinin and Khadjinsky with the nonlinear kinematic hardening rule of Armstrong and Frederick. In order to describe the strain recovery, the nonlinear kinematic hardening rule was modified. First, a loading surface was defined in a viscoplastic strain space. A loading–unloading criterion was then introduced using the loading surface. Moreover, a new parameter was defined by the relationship between the loading surface and the current state of the viscoplastic strain, and the evolution equation of back stress was modified using this parameter, which has some value only during unloading. Experimental results for polyethylene were simulated by using the modified constitutive equations, and cyclic inelastic deformation in both uniaxial and biaxial states of stress was predicted. Finally, the validity of the above-described modification was verified, and the features of the constitutive equation and the deformation were discussed.
Databáze: OpenAIRE
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