Rheology

Question 1

Strain that is easily recovered instantaneously on removal of stress

Answer 1

Elastic Strain

Question 2

involve permanent strain that occur without loss of cohesion and is the result of chemical bonds in crystal lattices in minerals by one of the dislocation creep mechanisms

Answer 2

Plastic Strain

Question 3

behaviour of fluids such as water or magma of any other substance with little internal structure.

Answer 3

Viscous

Question 4

the stress point beyond which a material becomes plastic.

Answer 4

Yield point

Question 5

Rupture

Answer 5

Rupture point

Question 6

The maximum ordinate point in the stress-strain diagram in which there is a ultimate strength or tensile strength and is before the actual rupture strength

Answer 6

Ultimate Strength

Question 7

is the strength of the material at rupture. This is also known as the breaking strength.

Answer 7

Rupture Strength

Question 8

have properties that are the same throughout any sample of any size

Answer 8

Homogeneous materials

Question 9

have properties which vary with location; either in a hand specimen or in a region which leads to scale-dependent behavior of rocks

Answer 9

inhomogeneous material

Question 10

have the same properties in all directions

Answer 10

isotropic materials

Question 11

properties vary with direction; layered rocks are strongly anisotropic to stress, but the degree of expression of the anisotropy depends on the direction in which the stress is oriented.

Answer 11

Anisotropic Materials

Question 12

A behavior that explains material exhibiting linear elastic behavior if it deforms in direct proportion to the applied stress and, after the stress is removed, will immediately rebounds to its original configuration.

Answer 12

Elastic (Hookean) Behaviour

Question 13

Elastic (Hookean) Behaviour:

is a measure of the ability of a material to withstand changes in length when under lengthwise tension or compression

Answer 13

Young’s Modulus (E)

Question 14

Elastic (Hookean) Behaviour:
is the elasticity coefficient for shearing or torsion force. The ratio of shear stress and shear strain
A linear relationship exists in ideal elastic behavior between the application of stress and the resulting strain. Below the elastic limit, an elastic material rebounds instantaneously to the original shape when the stress is removed.

Answer 14

Rigidity or Shear Modulus

Question 15

Elastic (Hookean) Behaviour:
the ratio of the proportional decrease in a lateral measurement to the proportional increase in length in a sample of material that is elastically stretched

Answer 15

Poisson’s Ratio

Question 16

Fluid - like behavior

Answer 16

Viscous Behavior

Question 17

Viscious Behavior: Stationary fluid that does not transmit shear stress

Answer 17

Perfect Fluid

Question 18

Viscous Behavior: Fluids in which there is a linearly proportional
relationship between differential stress and shear strain rate.

Answer 18

Newtonian Fluids

Question 19

Viscous Behavior: The reciprocal of viscosity

Answer 19

Fluidity

Question 20

True or False: Rocks at high temperatures near their melting points behave in a nearly viscous fashion, but their behavior is better described as plastic.

Answer 20

True

Question 21

True or False: Permanent strain in the form of viscous or plastic deformation occurs in a material beyond the elastic limit.

Answer 21

True

Question 22

True or False: Viscous behavior occurs in fluids, whereas plastic deformation occurs in solids below their melting points.

Answer 22

True

Question 23

True or False: Presence of water or other fluid may lower threshold temperatures and pressures for ductile behavior.

Answer 23

True

Question 24

a behavior that involves permanent deformation that affects the entire rock mass and begins at a yield stress.

Answer 24

Plastic (Saint-Venant) Behavior

Question 25

After the yield point is passed, the material flows at a constant stress unless one of the two things occurs:

Answer 25

Strain hardening or Strain Softening

Question 26

Increased resistance to deformation as strain increases
(Fossen: during plastic deformation, stress is necessary to deform the rock must be increased for strain to accumulate, because as the strain is accumulated the rocks become stronger. If the stress level is exceeded, this may end up brittleing. This, state is related to dislocations in atomic scale deformation because these atoms are intertangle, making it hard to accumulate strain.)

Answer 26

Strain hardening

Question 27

the stress in the material is actually decreasing with an increase in strain
(Fossen: less stress is needed to keep the deformation going. Geologic example is the effect of
grain size reduction during plastic deformation (mylonitization) because it makes more the frictional sliding become more effective, recrystalization into new and weaker minerals, introduction of fluids, increase in temperature.)

Answer 27

Strain Softening

Question 28

Behavior of Crustal Rocks: Brittle behaviour generally dominates the upper crust. A transition occurred due to increase in temperature and pressure.

Answer 28

Ductile-Brittle behavior

Question 29

Behavior of Crustal Rocks:

It is a combination of elastic and viscous behavior. It depends on the stress and strain rates(time dependent). Total strain in an elasticoviscous material is given by the sum of elastic and viscous strain components
(Fossen: these models are useful in large-scale modeling of the crust, while elastic deformation describe the short term strain in response to short term stress)
It states that we must consider strain rate def. Rocks that deform brittlely over a short time, will deform ductilelyover periods of thousands to million years.

Answer 29

Elasticoviscous (Maxwell) Behavior

𝛾 = 𝛾𝑒 + 𝛾𝑣 or 𝛾 = 𝜏 + 𝜏𝑡 /G+n

Question 30

True or False:
Elastoviscious (Maxwell) Behavior:
Hence, we must consider time-dependence of deformation. Rocks that deform brittlely over a short time (milliseconds to a few years) will deform ductilely over periods of thousands to million years.

Answer 30

True

Question 31

Behavior of rocks may vary in space as well as in time; concentration of deformation into specific parts of a rock mass by different behavior or mechanisms is

Answer 31

Strain Partitioning

Question 32

Factors Controlling Behaviors:

Temperature ↑ = Yield stress ↓ =

Answer 32

Weakens rocks

Question 33

Strain rate ↑ = Flow of stress level ↑ =

Answer 33

Strengthen rock

Question 34

Presence of fluids ↑ = Yield stress ↓ =

Answer 34

weakens rock

Question 35

Give the parameters that satisfies the condition of plastic deformation

Answer 35

Confining pressure ↑ = accumulate larger finite strain before failure, favors plastic deformation

Question 36

In plastic regime, if the grain size is ↓the resulting strain is

Answer 36

strain weakening

Question 37

If theres is no strain hardening, and the rock keeps accumulating strain without the need to apply stress the process is called

Answer 37

Creep

Question 38

Rheology: Ideal end member of Upper crust

Answer 38

Elastic

Question 39

Ideal end member of Magma

Answer 39

Viscous

Question 40

Ideal end member of Rock Salt and Lower Crust

Answer 40

Plastic

Question 41

True or False:Increasing the temperature, increasing the amount of fluid, lowering the strain rate and, in plastically deforming rocks, reducing the grain size all tend to cause strain weakening.

Answer 41

True

Question 42

is generally defined as the permanent change in shape or size of a body without fracture, produced by a sustained stress beyond the elastic limit of the material due to dislocation movement.

Answer 42

Plastic Deformation

Question 43

In frictional regime, if the grain size is decreasing the resulting strain is

Answer 43

Strain hardening