Rheology

Rheology
The study of deformation and flow
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Viscosity
The resistance of the fluid to flow or movement
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Non-newtonian fluids
Fluids which don't obey the relationship where their sheer stress (sigma) is directly proportional to sheer rate (gamma)
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Newtonian fluids
A fluid whose viscosity does not change no matter the stress applied to it. Example: water. It has a LINEAR sheer stress versus sheer rate curve, which passes through the origin
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Pseudoplastic
A fluid where viscosity decreases as stress increases, e.g. suspensions. The sheer stress vs sheer rate curve begins at the origin and the material will flow as the stress is applied to it
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Dilatant
A fluid where viscosity increases as stress increases, e.g. corn starch with water. This occurs in dispersions containing a high concentration of small deflocculated particles, e.g. pastes. The curve starts at origin and curves upwards
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Plastic
This fluid behaves as a rigid body at low stress and flows as a viscous fluid at high stress, e.g. toothpaste will not leave the tube until a certain pressure (yield point) is applied. It has a linear curve but it does not pass through the origin
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Thixotropy
A property where the viscosity of a fluid changes with sheer stress but then returns to its initial value at rest. This is a property of non-Newtonian fluids
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Rotational viscometers
Instruments that measure the viscosity of fluids. They rely on the viscous drag exerted on a body when it is rotated in the fluid. Examples: concentric cylinder and cone and plate geometry
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Other cards in this set

Card 2

Front

The resistance of the fluid to flow or movement

Back

Viscosity

Card 3

Front

Fluids which don't obey the relationship where their sheer stress (sigma) is directly proportional to sheer rate (gamma)

Back

Preview of the back of card 3

Card 4

Front

A fluid whose viscosity does not change no matter the stress applied to it. Example: water. It has a LINEAR sheer stress versus sheer rate curve, which passes through the origin

Back

Preview of the back of card 4

Card 5

Front

A fluid where viscosity decreases as stress increases, e.g. suspensions. The sheer stress vs sheer rate curve begins at the origin and the material will flow as the stress is applied to it

Back

Preview of the back of card 5
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