Year

2016

Degree Name

Doctor of Philosophy

Department

School of Mechanical, Materials and Mechatronic Engineering

Abstract

Shear viscosity is used as a parameter that characterizes the energy dissipation rate under shear loading. For instance, shear viscosity for Newtonian fluid is an intrinsic material parameter and independent of shear rate. Through the method of suspending small particles inside of the Newtonian fluid, particle concentration is formed and exhibits a number of rheological phenomena, for instance, shear thinning, shear thickening, thixotropy, yielding, and shear induced aggregation.

In some occasions, the energy dissipation rate decreases with the increasing shear rate, which means decreased shear viscosity and corresponding shear stress increases below linearity with the respect to shear rate, it is defined as shear thinning.

To the other end of the spectrum, another type of non-Newtonian behavior, in which a steep rise in shear viscosity is observed and corresponding shear stress increases faster than linearity with respect to shear rate, it is defined as Shear Thickening (ST).

Although this counter intuitive phenomenon of ST was initially viewed as a problem, for instance, complicating and limiting the rate of industrial processes which involved combination of high shear rates and highly concentrated suspensions such as paper coating and pumping of slurries, the unique material properties, such as increased energy dissipation together with increased elastic modulus, make the shear thickening materials very favorable candidates for damping and shock absorption applications. Consequently, engineers and colloid scientists have endeavored to study the science and practical problems of the shear thickening materials. More recently, it is widely proposed that when engineered into composite materials, Shear Thickening Fluids (STFs) can be controlled and harnessed, and thus triggers the development of large number of novel fluids or elastomer materials featuring shear thickening, which in turn broaden the horizon of shear thickening study, and the application of the shear thickening phenomenon is greatly widened as a result.

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