Oscillatory and simple shear flows of a flour-water dough: a constitutive model |
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Authors: | Dr Nhan Phan-Thien Mohsen Safari-Ardi Alexandro Morales-Patiño |
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Institution: | (1) Department of Mechanical Engineering, Sydney University, NSW 2006 Sydney, Australia |
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Abstract: | We reported some dynamic and viscometric data on an Australia strong flour-water dough. In oscillatory shear flow experiments, we found the linear viscoelastic strain limit is extremely low, of O(10–3), consistent with other published data on doughs. The relaxation spectrum derived from the dynamic data is broad, indicating the blend nature of dough. In the start-up of a simple shear flow, we found the shear stress increases nonlinearly with time to a peak value and then decreases rapidly, with no steady-state response. The concept of steady-state viscosity is not very meaningful here, unless the strain at which the measurements are taken is also specified. The stress peaks are strain-rate dependent; but they occur at a strain of O(10), for the strong flour/water dough used, over four decades of strain rates. The experimental data were used to construct a phenomenological model for dough, consisting of an hyperelastic term (representing the elastic gluten network of permanent cross-linked long chain polymers), and a viscoelastic contribution (representing the suspension of starch globules and other long-chain components in dough that are not parts of the permanent cross-linked gluten network). The model predictions compared favourably with experimental data in oscillatory and shear flows. |
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Keywords: | Dynamic data of dough viscometric data of dough rheology of dough constitutive modelling of dough |
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