MATEPRO Module 5

Question 1

4 Roles of Materials in the History of Man

Answer 1

• Association of dominant material to time periods: Stone Age, Bronze Age, Iron Age
• Similar to manufacturing, it determines what is possible and contributes to comfort, productivity, safety and security of everyday living.
• One replaces another when new advantages and capabilities are
  realized.
• Knowledge of material properties is essential to an engineer in
  manufacturing: Structure, Properties, Processing, Performance.

Question 2

Iron, copper, aluminum, magnesium, nickel, titanium, lead, tin, and zinc are what type of material?

Answer 2

Metallic materials

Question 3

wood, rick, concrete, glass, rubber, and plastics are what type of material?

Answer 3

Nonmetallic materials

Question 4

______, such as fiber glass are capable of
demonstrating higher strength at a LOWER WEIGHT and VOLUME.

Answer 4

Composites

Question 5

used to distinguish one material from another: weight, density, melting point, optical characteristics, thermal and electrical properties, etc.

Answer 5

Physical Properties

Question 6

describe how a material responds to applied loads or forces: tensile strength, yield strength, Modulus of Elasticity,
etc.

Answer 6

Mechanical Properties

Question 7

force per unit area experienced by a material: S = F/A

Answer 7

Stress

Question 8

stress that causes material to increase in length (+deformation)

Answer 8

Tensile Stress

Question 9

stress that causes material to reduce in length (-deformation)

Answer 9

Compressive Stress

Question 10

the amount of deformation divided by the material’s original length: e = ΔL/L

Answer 10

Strain

Question 11

observed when the applied loads are constant (not changing)

Answer 11

Static Properties

Question 12

observed when the applied loads are changing: impact loads, fluctuating loads, time-dependent effects, etc.

Answer 12

Dynamic Properties

Question 13

• Measures the behaviour of
  a material with respect to a
  tensile load
• Uses the Universal Testing
  Machine (UTM)

Answer 13

Uni-Axial Tensile Strength

Question 14

• Proportional Limit (Hooke’s Law)
• Young’s Modulus (Modulus of
  Elasticity) – ratio of stress to strain;
  measure of toughness
• Elastic Limit
• Resilience
• Modulus of Resilience
• Plastic Deformation
• Yield Point
• Offset Yield Strength
• Ultimate Tensile Strength
• Necking
• Breaking Strength / Fracture Strength

Answer 14

The Engineering Stress-Strain Curve

Question 15

is the behavior when the load is first applied, the specimen elongates in
proportion to the load. The specimen returns to its original length and shape if the load is removed.

Answer 15

Linear elastic

Question 16

occurs when the yield stress of the material
is reached.

Answer 16

Permanent (plastic) deformation

Question 17

is defined as the ratio of the applied load, P, to the original cross-sectional area, Ao, of the specimen:
𝜎 = P/Ao

Answer 17

Engineering Stress (Nominal Stress)

Question 18

e = (l-lo)/lo

Answer 18

Engineering Strain

Question 19

As the specimen begins to elongate under a continuously increasing load, its cross-sectional area decreases ________ and _____________ throughout its gage length.

Answer 19

permanently, uniformly

Question 20

If the specimen is __________ from a stress level higher than the yield stress, the curve follows a _______________ and _________ to the original slope of the curve.

Answer 20

unloaded, straight line downward, parallel

Question 21

the maximum engineering stress of the material.

Answer 21

Tensile strength or ultimate tensile strength (UTS)

Question 22

If the specimen is loaded beyond its ultimate tensile strength, it begins to ____, or ____ down

Answer 22

neck, neck

Question 23

the engineering stress at fracture

Answer 23

Breaking or fracture

Question 24

• the ratio of stress to strain in the elastic region.
• the stiffness of the material
  E = 𝜎/e (Hooke’s law)

Answer 24

Modulus of Elasticity (E) or Young’s modulus

Question 25

the absolute value of the ratio of the lateral strain to the longitudinal strain. v = lateral strain/longitudinal strain

Answer 25

Poisson's Ratio (v)

Question 26

_____ materials show significant elongation before breaking/fracture.

Answer 26

Ductile

Question 27

When materials fail with little or no ductility, they are said to be_____

Answer 27

Brittle

Question 28

____ is simply the lack of ductility. Strong materials can be ____ and ___ materials can be strong

Answer 28

Brittleness, brittle, brittle

Question 29

Also known as _________ – defined as the work per unit volume required to fracture a material.

Answer 29

Modulus of toughness

Question 30

Upon continuous application of a tensile force, a material ______

Answer 30

elongates

Question 31

When a material elongates, that means it reduces in __________

Answer 31

cross-sectional area

Question 32

Since S = _____, that means, as the material reaches its ultimate and breaking strength, it gets stronger and stronger. * This phenomenon is called ________

Answer 32

F/A, Strain Hardening

Question 33

The greater the capacity of a material to absorbed energy, the greater is its ___________

Answer 33

Damping Capacity

Question 34

Measures the behaviour of a material with respect to a compression load

Answer 34

Compression Test

Question 35

* Assesses the wear resistance, strength of a material, resistance to scratching, cutting and drilling of a material. * Standard hardness testing tools press a diamond/hardened steeltipped material onto the flat surface of the material being tested. * Detailed tables are available for a wide range of materials.

Answer 35

Hardness Testing

Question 36

Brinell, Rockwell, Vickers, Knoop ______ Tests

Answer 36

Hardness

Question 37

* Uses a tungsten carbide or hardened steel ball 10mm in diameter. * Measures hardness using the _____ Hardness Number (__HN), which is equal to the load (kg) divided by the surface area (mm2) of the spherical indentation.

Answer 37

Brinell Harness Test, Brinell

Question 38

* Uses a hardened steel ball or a diamond-tipped cone. * Utilizes a minor load and a major load. * A material is initially indented using a minor load. * After relaxing the material, the material is re-indented again using a major load. * The hardness is then measured using the difference in depth between the minor and major indentations. * Different materials require different minor and major load settings.

Answer 38

Rockwell Test

Question 39

* Uses a square-based, diamond-tipped pyramid to indent the material. * Measures hardness by dividing the applied load (kg) by the indentation surface area (mm2). * Advantage is that even smaller loads are guaranteed to be measured because the surface area is easier to measure. (because of the diagonal of the pyramid) * Indentation is also easy to hide in the product compared to other tests.

Answer 39

Vickers Hardness Test

Question 40

* For microindentation tests * Measures loads ranging from 25 to 3600g. Other common hardness tests only measure loads between 1 to 120Kg. * Uses a microscope to measure indentation.

Answer 40

Knoop Hardness Test

Question 41

* Utilizes a diamond tipped hammer and drops it to the flat surface of the material. * Measures resilience of the material

Answer 41

Scleroscope Test

Question 42

* Files of different roughness are used to evaluate scratch sensitivity of the material

Answer 42

File Test

Question 43

Subjects the material to a rapidly applied load, or impact.

Answer 43

Impact Test

Question 44

Material is loaded horizontally on the tool.

Answer 44

Charpy Test

Question 45

Material is loaded vertically on the tool

Answer 45

Izod Test

Question 46

There are materials which are _____-sensitive and ____-insensitive.

Answer 46

notch, notch

Question 47

For notch-_____ materials, good surface finishing is key to good performace.

Answer 47

sensitive

Question 48

Notch-____ materials may be used for applications requiring rough surface finishes

Answer 48

insensitive

Question 49

From field data, 90% of material failure and breakages result from material _____

Answer 49

fatigue

Question 50

The stress below which the material will not break no matter how many cycles it is applied is called the ________ or ________ of the material.

Answer 50

endurance limit, endurance strength

Question 51

Fatigue Failures are caused by ________________ (beach marks)

Answer 51

successive micro-fractures

Question 52

Temperature affects _____________

Answer 52

rate of deformation

Question 53

* Some materials undergo a transition phase wherein they change from ductile to brittle material, vice-versa. * Fracture Appearance Transition Temperature (FATT)

Answer 53

Ductile-to-brittle transition

Question 54

* Even if just applied with a constant load, a material can still experience continuous elongation, provided that it is exposed to a high temperature. * Failure due to this phenomenon is called _____

Answer 54

Creep

Question 55

* ____________ refers to how easily or how suitable a particular machining process is to a particular material. * For example, plastics are good for extrusion and moulding processes, while poor in forming processes.

Answer 55

Machinability

Question 56

* The study of how an existing fracture or crack can be prevented from spreading and ultimately breaking the material. * Dormant vs Dynamic Fractures

Answer 56

Fracture Mechanics