Bengham Plastics start to flow linearly after reaching a critical shear stress. Assuming this critical shear stress is very small, then approximately, we can consider it behaves like a Newtonian fluid.
Dear Ahmed, it is in fact this threshold that marks the difference between the two viscoelastic liquids. Its meaning is that the respence or deformation is not instantaneous for Bingham liquid compared to A Newtonian one. When you say small, to what entent ? If too much close to zero yes, you may approximate Thé Bingham behavior to a Newtonian one. Regards
Thank you, Mr Abdelkader.
My argument is that a Bengham fluid (such as Mountain bee Honey) is temperature dependent and act linearly after exceeding the critical shear stress. If the critical shear stress is for example 1MPa which is very near to the origin, then we can consider this fluid as a Newtonian one, given the fact that viscosity will be constant.
To clarify my argument:
Equation of a Newtonian fluid would be in the form of y = mx
Equation of a Bengham fluid would be in the form of y = mx + c , where c is the critical shear stress. Therefore, for small c, y will depend mainly on mx.
It is only you who can take such a decision, I am teaching the first year master students à course on viscoelasticity but I have never met a situation in which such an approximation is done. Ragards
First of all, to avoid confusion among students, let me clarify that neither Newtonian nor Bingham fluids are considered as viscoelastic.
Ahmed, when considering real case situations where sagging is important, yield stress will be relevant. On the other hand, if your process remains in the range of shear stresses or shear rates much above your yield stress then you may then neglect this later effect.
Why would you like to make such an approximation?
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