Chapter 6

Question 1

brittleness

Answer 1

tendency to fracture when even a small load is applied

Question 2

ductility

Answer 2

how much a material can deform without sustaining internal damage

Question 3

creep

Answer 3

deformation of a material at elevated temperatures

Question 4

elasticity

Answer 4

ability of a material to return to its original shape after some deformation

Question 5

plasticity

Answer 5

ability of a material to remain deformed after an external force is removed

Question 6

fatigue

Answer 6

weakening of a material due to repeated cyclic load

Question 7

hardness

Answer 7

ability of a material to resist permanent (plastic) change in shape

Question 8

resilience

Answer 8

ability to absorb energy and resist impact load

Question 9

stiffness

Answer 9

ability of a material to resist additional deformation when loading continues

Question 10

toughness

Answer 10

ability of a material to resist fracture

Question 11

tensile test

Answer 11

stretches a sample of a material in a specific form with a decreased diameter in the middle for 2in

Question 12

engineering stress

Answer 12

stress = F/A(o)
F = force
A(o) = original cross-sectional area

Question 13

engineering strain

Answer 13

strain = (l(i) - l(o)) / l(o)
l(o) = original length
l(i) = instantaneous length

Question 14

shear

Answer 14

type of deformation that results in stress and strain = apply force in opposite directions to top and bottom of an object parallel to the surface

Question 15

shear strain

Answer 15

strain = alpha + beta
alpha = angle between ground and bottom surface
beta = angle between z-axis and side of material

Question 16

shear stress

Answer 16

stress = F/A(o)

Question 17

torsion

Answer 17

occurs when twisting a material

Question 18

when is poissons ratio applied? (v)

Answer 18

for elastically behaving materials - elongation in z-direction is proportional to force acting in the z-direction - causing contraction of the material in x and y directions

Question 19

what strain can most materials handle elastically

Answer 19

0.005 or 0.05%

Question 20

what happens above a strain of 0.005?

Answer 20

atomic bonds permanently deform creating permanent deformation

Question 21

what is the suggested value for yield stress?

Answer 21

0.002 or 0.02%

Question 22

yielding

Answer 22

point of transition from elastic to plastic deformation

Question 23

stress at yielding

Answer 23

yield stress

Question 24

how to find yield stress from graph

Answer 24

find initial slope (m) then draw a line with that slope starting at 0.002 or 0.005 on x-axis and find intersection

Question 25

ultimate tensile strength

Answer 25

material begins to fail, voids form and create cracks.

Question 26

at ultimate tensile strength: as ______ decreases, the amount of load needed to continue deformation decreases

Answer 26

area

Question 27

how to compare ductility on stress strain graph

Answer 27

higher strain value at fracture means more ductile

Question 28

how do we numerically represent ductility

Answer 28

percent elongation or percent area reduction

Question 29

how to compare resilience on stress strain graph

Answer 29

area under the curve before yield strain find Ur

Question 30

how to compare toughness on stress strain graph

Answer 30

area under the curve before fracture

Question 31

rockwell scale

Answer 31

machine applies a load onto a material then determines the hardness subject to: - indenter type - load - dwell duration

Question 32

brinell hardness test

Answer 32

steel ball forced into a material then the indentation diameter is measured convert to mpa or psi using equation for HB

Question 33

Vickers microhardness test

Answer 33

diamond indenter used and then distance between opposite corners of the diamond indent is used to get the hardness

Question 34

strain hardening

Answer 34

for some materials, deformation after yield becomes difficult equation with n = strain hardening exponent

Question 35

fatigue definition with stress/strain

Answer 35

cracks develop in a material below the yield strength as damage accumulates over time and may not be visible

Question 36

fatigue limit

Answer 36

any stress below fatigue limit means the material has an unlimited life

Question 37

fatigue strength

Answer 37

stress after 10^7 cycles

Question 38

fatigue life

Answer 38

number of cycles to reach fatigue failure at a given load

Question 39

creep definition 2

Answer 39

deformation of a material over a long period with a static load

Question 40

3 stages of creep

Answer 40

primary, secondary, tertiary

Question 41

primary creep

Answer 41

initial deformation (lnx)

Question 42

secondary creep

Answer 42

steady state (predictable) deformation mx+b

Question 43

tertiary creep

Answer 43

deformation up to failure e^x