Chapter 6

Question 1

is the study of the mechanical properties of solid materials as well as fluids and gases.

Answer 1

Rheology

Question 2

Equations that mathematically describe the relationship between stress and strain or strain rate.

Answer 2

constitutive laws

Question 3

By isotropic we mean a medium that has the same mechanical properties in all directions, so that it reacts identically to stress regardless of its orientation.

Answer 3

Isotropic medium

Question 4

resists a change in shape, but strains as more stress is applied. Ideally, it returns to its original shape once the applied stress (force) is removed.

Answer 4

elastic material

Question 5

a linear relationship between stress (or force) and strain.

Answer 5

linear elastic material

Question 6

is a constitutive equation for elastic materials

Answer 6

Hooke’s Law

Question 7

The curves defined during straining (loading) and unstraining (unloading) may still be identical, in which case the material

Answer 7

perfect elastic

Question 8

materials that do not change volume during deformation.

Answer 8

Incompressible materials

Question 9

which gives the ratio between the extensions normal and parallel to the stress vector.

Answer 9

Poisson’s Ratio

Question 10

are waves of elastic deformation or energy in which particles oscillate in the direction of wave propagation.

Answer 10

P-waves

Question 11

are elastic body waves where particles oscillate perpendicular to the propagation direction.

Answer 11

S-waves

Question 12

is the inverse of the compressibility of a medium, which is a measure of the relative volume change (volumetric strain) of a fluid or solid as a response to a pressure or mean stress change.

Answer 12

Bulk Modulus

Question 13

The ease with which fluids flow is described in terms of their

Answer 13

Viscosity

Question 14

implies dependence of stress on strain rate: higher stress means faster flow or more rapid strain accumulation.

-is therefore said to be irreversible and creates permanent strain

Answer 14

Viscous deformation

Question 15

Viscous deformation can therefore be said to be ____________ strain is not instant but accumulates over time.

Answer 15

time-dependent deformation;

Question 16

is a measure of how fast a rock object changes length or shape.

Answer 16

Strain rate

Question 17

is resistance of layers or objects to flow. The term is qualitative and relative to that of its neighboring layers or matrix.

Answer 17

Competency

Question 18

permanent strain is added to the elastic strain. If permanent strain keeps accumulating under a constant stress condition

Answer 18

perfect plastic deformation.

Question 19

is the permanent change in shape or size of a body without fracture, accumulated over time by a sustained stress beyond the elastic limit (yield point) of the material.

Answer 19

Plastic Strain

Question 20

is one where the stress cannot rise above the yield stress and strain can continue to accumulate without any change in the stress level.

Answer 20

perfectly plastic material

Question 21

Where there is an additional component of elastic deformation, then the material is

Answer 21

elastic perfect plastic

Question 22

means that the stress necessary to deform the rock must be increased for strain to accumulate, because the rock becomes stronger and harder to deform.

Answer 22

strain hardening

Question 23

During deformation, atomic-scale defects are known as

Answer 23

Dislocations

Question 24

If there is no strain hardening and the material keeps deforming without any increase in the applied force or stress

Answer 24

Creep

Question 25

is the case when less stress is required to keep the deformation going.

Answer 25

strain softening

Question 26

A geologic example is the effect of grain size reduction during plastic deformation

Answer 26

mylonitization

Question 27

This is the situation where stress and elastic strain increase until the yield point is reached, beyond which the deformation is plastic. A material that responds in this way is

Answer 27

elastic–plastic

Question 28

is one that flows as a perfectly viscous material, but only above a certain yield stress (a characteristic of plastic behavior). Below this yield stress there is no deformation at all.

Answer 28

Viscoplastic

Question 29

is where the deformation process is reversible, but both the accumulation and recovery of strain are delayed.

Answer 29

Kelvin viscoelastic behavior

Question 30

accumulates strain from the moment a stress is applied, first elastically and thereafter in a gradually more viscous manner.

Answer 30

Maxwell viscoelastic

Question 31

is a model that more closely approximates the response of natural rocks to stress.

Answer 31

General linear behavior

Question 32

is the plastic deformation of a material that is subjected to a persistent and constant stress when that material is at a high homologous temperature.

Answer 32

Creep

Question 33

An increase in temperature lowers the yield stress or weakens the rock.

Answer 33

Increasing the strain rate means increasing the flow stress level.

Question 34

tends to weaken rocks, lower the yield stress, and enhance crystal-plastic deformation

Answer 34

Presence of Fluid

Question 35

Increasing the _________ allows for larger finite strain to accumulate before failure and thus favors crystal-plastic deformation mechanisms.

Answer 35

confining pressure

Question 36

means being similar or uniform, while isotropic means having properties that do not vary with direction.

Answer 36

Homogeneous

Question 37

means that the state of strain is identical in any one piece of the area or volume in question

Answer 37

Homogeneous strain

Question 38

means that the volume has been shortened or extended by the same amount in every direction. It involves no change in shape, only a change in volume.

Answer 38

Isotropic Strain

Question 39

is a state where all three principal stresses are of equal magnitude. If they are not, stress can still be homogeneous if the state of stress is the same in every part of the rock

Answer 39

Isotropic Stress

Question 40

is one that accumulates permanent strain (flows) without macroscopically visible fracturing, at least until a certain point where its ultimate strength is exceeded.

Answer 40

Ductile material

Question 41

is one that deforms by fracturing when subjected to stress beyond the yield point.

Answer 41

Brittle Material

Question 42

are well represented in metamorphic rocks, i.e. rocks that have been deformed in the middle and lower part of the crust.

Answer 42

Ductile structures

Question 43

preserves continuity of originally continuous structures and layers and describes a scale-dependent deformation style that can form by a range of deformation mechanisms.

Answer 43

Ductile deformation

Question 44

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 44

Plastic deformation