Evaluation of the dynamic-mechanical properties of solids from a cooperative model for stress relaxation |
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Authors: | C -G Ek C Högfors J Kubát M Rigdahl W Rychwalski S Uggla |
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Institution: | (1) Department of Polymeric Materials, Chalmers University of Technology, S-41296 Gothenburg, Sweden;(2) Department of Mechanics, Chalmers University of Technology, S-41296 Gothenburg, Sweden;(3) Department of Computer Science, Chalmers University of Technology, S-41296 Gothenburg, Sweden |
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Abstract: | For many solid materials the stress relaxation process obeys the universal relationF = – (d /d lnt)max = (0.1 ± 0.01) (
0 —
i
), regardless of the structure of the material. Here denotes the stress,t the time,
0 the initial stress of the experiment and
i
the internal stress. A cooperative model accounting for the similarity in relaxation behaviour between different materials was developed earlier. Since this model has a spectral character, the concepts of linear viscoelasticity are used here to evaluate the corresponding prediction of the dynamic mechanical properties, i.e. the frequency dependence of the storageE ( ) and lossE ( ) moduli. Useful numerical approximations ofE ( ) andE ( ) are also evaluated. It is noted that the universal relation in stress relaxation had a counterpart in the frequency dependence ofE ( ). The theoretical prediction of the loss factor for high-density polyethylene is compared with experimental results. The agreement is good. |
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Keywords: | Dynamic-mechanical properties cooperative model stress relaxation solid high-densitypolyethylene |
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