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PL1002 > Rheology > Flashcards

Rheology Flashcards

1
Q

Stress

A

Force per unit area that leads to deformation

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2
Q

Strain

A

Resulting deformation

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3
Q

Elastic

A

Material fully recovers when stress removed

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4
Q

Viscosity

A

Internal resistance involved in the relative motion of one layer of molecules with respect to the next

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5
Q

What happens to viscosity of a gas upon heating?

A

Viscosity increases due to increasing internal friction

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6
Q

What happens to viscosity of a liquid upon heating?

A

Viscosity reduces as there is decreased contact

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7
Q

Equation for dynamic viscosity

A

log(Π) = E/RT + logA

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8
Q

Equation for relative viscosity

A

Πrel = Π1/Π2 = t1p1/t2p2

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9
Q

Equation for relative viscosity when p1 ≅ p2

A

Πrel = t1/t2

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10
Q

Equation for specific viscosity

A

Πspecific = Πrel - 1

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11
Q

Equation for reduced viscosity

A

Πred = Πsp/c

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12
Q

Intrinsic viscosity

A

Theoretical viscosity at 0 concentration

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13
Q

How is intrinsic viscosity found?

A

Plot reduced viscosity against concentration. y-intercept is intrinsic viscosity

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14
Q

3 types of non-newtonian flow

A

Plastic, pseudoplastic and dilatant

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15
Q

What type of flow has a yield stress?

A

Plastic

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16
Q

What is the apparent viscosity equation for newtonian fluids?

A

Πapp = shear stress/shear rate = σ/γ

17
Q

Why do plastic and pseudoplastic have their graph shape?

A

Shear thinning

18
Q

What is the power law when related to shear stress?

A

σ = Π’γ^n
Π’ = viscosity coefficient
γ = shear rate
n = rate index

19
Q

What is the power law in graphic form?

A

logσ = nLogγ + LogΠ’

20
Q

What is the value of n in newtonian flow?

A

n = 1

21
Q

What is the value of n in pseudoplastic flow?

A

n < 1

22
Q

What is the value of n in dilatant flow?

A

n > 1

23
Q

What is the value of n in plastic flow?

A

n < 1 and y intercept = σ0

24
Q

What are the units of viscosity?

A

Pa.s

25
Q

Equation for rotational viscometers

A

Π = T/kw
T = torque
w = speed of rotation
k = constant

26
Q

Equation for falling sphere viscometer

A

v = 2a^2 g(σ-ρ) / 9n
a = radius of ball
σ = density of ball
ρ = density of fluid
Π = viscosity
g = acceleration due to gravity

27
Q

What is thixotropy?

A

To change by tough

28
Q

What is the area inside the rheogram of a thixotropic fluid measuring?

A

Degree of breakdown

29
Q

Why does thixotropy show up on a rheogram?

A

Viscosity is usually measured by increasing shear rate from 0 to a maximum and then decreasing at the same rate. This creates an increasing and decreasing curve

30
Q

Strain equation

A

Strain = ΔL/L

Strain = change in length/original length

31
Q

Strain percentage equation

A

Strain = ΔL/L x 100

32
Q

Rate of shear equation

A

Rate of shear = dv/dr

PL1002 (6 decks)

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