Non-Newtonian Systems: Three Classes and Rheograms
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Questions and Answers

What is a rheogram?

A plot of shear rate as a function of shear stress

What is the yield value in a plastic flow?

An indication of the force needed to convert the system into a Newtonian system

What is the slope of a rheogram called in plastic flow?

Mobility

What is the reciprocal of mobility termed in plastic flow?

<p>Plastic viscosity</p> Signup and view all the answers

What type of flow is associated with shear-thinning behavior?

<p>Pseudoplastic flow</p> Signup and view all the answers

What happens in dilatant flow as the rate of shear increases?

<p>Resistance to flow increases</p> Signup and view all the answers

What term is used to describe a system that increases in volume when sheared?

<p>Dilatant</p> Signup and view all the answers

What happens to a dilatant system when shear stress is increased?

<p>The bulk of the system expands (dilates) and the particles take an open form of packing.</p> Signup and view all the answers

Give an example of a dilatant system.

<p>Corn starch in water</p> Signup and view all the answers

What precaution should be taken during processing of dilatant materials?

<p>Appropriate precautions should be used to avoid solidification under high-speed mixing conditions.</p> Signup and view all the answers

What term is used to describe the decrease in viscosity as a function of time upon shearing, followed by recovery of the original viscosity without shearing?

<p>Thixotropy</p> Signup and view all the answers

What is the fundamental unit of viscosity measurement?

<p>The poise</p> Signup and view all the answers

Describe the behavior of a system exhibiting thixotropy.

<p>At rest, its rigidity is like a gel. As shear is applied, the structure breaks and undergoes a gel-to-sol transformation.</p> Signup and view all the answers

Define fluidity and its relationship to viscosity.

<p>Fluidity is the reciprocal of viscosity (Ø = 1/η).</p> Signup and view all the answers

What is kinematic viscosity and how is it calculated?

<p>Kinematic viscosity is the absolute viscosity divided by the density of liquid at a specified temperature (η = ρ).</p> Signup and view all the answers

How does viscosity change with temperature in fluids?

<p>Viscosity decreases as temperature increases.</p> Signup and view all the answers

What are examples of non-Newtonian fluids?

<p>Colloids, emulsions, liquid suspensions, and ointments.</p> Signup and view all the answers

How do non-Newtonian fluids differ from Newtonian fluids?

<p>Non-Newtonian fluids have a variable relationship between shear stress and shear rate, unlike Newtonian fluids.</p> Signup and view all the answers

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