chapter 6

Question 1

What is brittleness

Answer 1

Tendency to fracture when even small load/deformation is applied i.e glass

Question 2

what is creep

Answer 2

creep is deformation of material at elevated temperature

Question 3

what is Elasticity

Answer 3

ability to return to original shape after deformation

Question 4

what is plasticity

Answer 4

ability of material to maintain deformation/shape

Question 5

what is fatigue

Answer 5

ability of metal to sustain a repeated cyclic road

Question 6

what is resilience

Answer 6

ability to absorb energy and resist soft/impact loading

Question 7

what is stiffness

Answer 7

ability to resist additional deformation when loading is continuous

Question 8

what is toughness

Answer 8

ability of material to resist fracture.

Question 9

what can be used to to quantify materials(asking about type of test)

Answer 9

tensile test we can get experimental numerical data

Question 10

does strain have units

Answer 10

no strain does not have units but in many cases you will see”in/in” or percent sign

Question 11

what does stress and strain equation apply

Answer 11

stress and strain apply to tension and compression

Question 12

what is shear starin

Answer 12

measure of how much material deforms in response to shear stress

Question 13

what is sheer tress

Answer 13

shear stress is a type of stress that occurs when forces are applied parallel or tangential to a material surface causing layer of material to slide relative to each other.

Question 14

when is material perfectly distributed

Answer 14

when alpha equal beta

Question 15

what is torsion

Answer 15

not deforming a material in parallel plates but twist the material

Question 16

what is result of loading a material

Answer 16

it is strain. For example if we load in z-direction Ez and at the same time material will deform in Ex and Ey direction

Question 17

What is relationship between Ex,Ey and Ez

Answer 17

they are defined by poissons ratio. It is able to relate tension and torsion

Question 18

What is material stress proportional to during the initial stage of loading

Answer 18

stress is proportional to strain

Question 19

Higher the value of E, the stiffer the material is (T/F)

Answer 19

True

Question 20

When a stress is applied in z-direction longitude direction what is the direction of elongation

Answer 20

The stress causes the metal to elongate in the z-direction resulting in the axis strain Ez.

Question 21

When a stress is applied in z-direction longitude direction what is the direction of elongation? But now answer what happens to the lateral component’s x and y?

Answer 21

Lateral contraction in x and y direction is when the material is stretched along the z-direction it contracts in xy plane. Results in Ex and Ey which are compressive.Vice versa if the material is being compressed then lateral compenets will experince tenisle

Question 22

Is the value of E related to bonding structure or crystal structure in a material? T/F

Answer 22

T

Question 23

WHAT is G and how can we determine it ?

Answer 23

G is shear modulus which can be determine from linear elastic region of a shear stress-strain curve

Question 24

Do compressive shear or torsional stress impose elastic behavior ?

Answer 24

Yes

Question 25

When is shear stress is calculated and when is engineering stress ?

Answer 25

Shear stress is calculated when forces acts parallel to the surface. Engineering stress is calculated when forces act perpendicular to the surface.

Question 26

What is the most complex loading ?

Answer 26

when tension/shear/torsion are applied simultaneously

Question 27

explain why result of loading a material is strain

Answer 27

When a material is loaded (subjected to a force), it deforms as a response to that force. Strain is the measure of this deformation, expressed as the change in shape or size relative to the original dimensions of the material. Here’s why loading results in strain:

Question 28

what relates tension and torsion

Answer 28

possion ratio

Question 28

Define shear

Answer 28

Shear refers to a type of force that causes one part of a material to slide or deform parallel to the direction of the applied force. Unlike normal forces (compression or tension), which act perpendicular to a surface, shear forces act parallel to that surface

Question 28

what is pure torsion?

Answer 28

if we are not deforming a material but we are twisting it then it is pure torision.

Question 29

At what strain value do many material exhibt some amount of elastic strain?

Answer 29

many material exhibit some amount of elastic strain typically up to 0.005 (i.e 0.5% strain). Above this value atomic bond tend to break and material permentally deforms

Question 30

What is yield strength

Answer 30

Yield strength is the transition between elastic and plastic which can be approximated. A parallel line from 0.002(i.e 0.2 % strain) and we can do the same at 0.005 i.e 0.5% strain

Question 31

What is ultimate tensile strength ?

Answer 31

the maximum stress a material can sustain is called it can approximated from the graph at the highest point

Question 32

How can we quantify ductility and what region do we take into account when calculating ductility?

Answer 32

% Elongation or %Reduction in area we only consider the plastic region

Question 33

what is resilience and associated property modules of resilience?

Answer 33

Resilience is the capacity of a material to absorb energy when it is deformed elastically
and then, upon unloading, to have this energy recovered. The associated property is the
modulus of resilience, Ur, which is the strain energy per unit volume required to stress a
material from an unloaded state up to the point of yielding.
Computationally, the modulus of resilience for a specimen subjected to a uniaxial
tension test is just the area under the engineering stress–strain curve taken to yielding

Question 34

What is toughness ?

Answer 34

Area under the engineering stress stain curve till fracture occur.

Question 35

From engineering stress-strain diagram, it appears that less __________(fill in the blank) is required to keep the deforming

Answer 35

Force

Question 36

The issue is that, in real life the _____ (fill in the blank), so the_____ (fill in the blank) is actually increasing

Answer 36

1) area 2) stress

Question 37

whats true stress ?

Answer 37

True stress is measure of stress based on the actual cross-sectional area of the material at a given instant during deformation. it accounts for material change in geometry as it deforms. True stress increases during the plastic deformation even if the applied force is constant because the cross sectional area decreases due to the material necking

Question 38

What is true strain ?

Answer 38

True strain is a measure of deformation that accounts for the continuous change in the dimensions of a material during deformation. It is based on the natural logarithm of the ratio of the current length to the original length, making it more accurate for large deformations compared to engineering strain

Question 39

How are true stress and strain different from engineering stress and strain ?

Answer 39

Engineering stress and strain ignore changes in the geometry during deformation. They assume the cross-sectional area and intial length remain constant

whereas true stress and strain consider these changes making them more accurate for large deformation

Question 40

what is yielding ?

Answer 40

Yielding is a process where a material transitions from elastic deformation ( reversible ) to plastic deformation which means it cannot reverse

Question 41

what is yield point and yield offset ?

Answer 41

yield point is a specific point on the stress-strain curve where a material transitions from plastic deformation. However, some material dont have this so we use yield offset at 0.2% strain to estimate this point

Question 42

what is strain hardening related too ?

Answer 42

It is related to stress.

Question 43

Describe Rockwell ?

Answer 43

Test parameter: indenter, load, dwell time.
The indenter makes an impression on the material and the depth of the impression is related to the hardness ( resistance to plastic deformation) . If reading is less than 20 or greater than 100 use a different scale/load/time parameter.

Question 44

Describe Brinell and Vickers hardness test?

Answer 44

For Brinell we use steel ball as indenter whereas for vickers hardness we use diamond indenter and it is done on small scale.

Question 45

what is hardness in terms of testing?

Answer 45

a non destructive way to measure plastic deformation resistance a material.