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Wagner model is a rheological model developed for the prediction of the viscoelastic properties of polymers. It might be considered as a simplified practical form of the Bernstein-Kearsley-Zapas model. The model was developed by German rheologist Manfred Wagner. For the isothermal conditions the model can be written as: : where: * is the Cauchy stress tensor as function of time ''t'', *''p'' is the pressure * is the unity tensor *''M'' is the memory function showing, usually expressed as a sum of exponential terms for each mode of relaxation: :, where for each mode of the relaxation, is the relaxation modulus and is the relaxation time; * is the ''strain damping'' function that depends upon the first and second invariants of Finger tensor . The ''strain damping function'' is usually written as: :, The strain hardening function equal to one, then the deformation is small and approaching zero, then the deformations are large. The Wagner equation can be used in the non-isothermal cases by applying time-temperature shift factor. ==References== *M.H. Wagner ''Rheologica Acta'', v.15, 136 (1976) *M.H. Wagner ''Rheologica Acta'', v.16, 43, (1977) *B. Fan, D. Kazmer, W. Bushko, ''Polymer Engineering and Science'', v44, N4 (2004) 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Wagner model」の詳細全文を読む スポンサード リンク
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