MATEPRO Module 5 Flashcards
4 Roles of Materials in the History of Man
- 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.
Iron, copper, aluminum, magnesium, nickel, titanium, lead, tin, and zinc are what type of material?
Metallic materials
wood, rick, concrete, glass, rubber, and plastics are what type of material?
Nonmetallic materials
______, such as fiber glass are capable of
demonstrating higher strength at a LOWER WEIGHT and VOLUME.
Composites
used to distinguish one material from another: weight, density, melting point, optical characteristics, thermal and electrical properties, etc.
Physical Properties
describe how a material responds to applied loads or forces: tensile strength, yield strength, Modulus of Elasticity,
etc.
Mechanical Properties
force per unit area experienced by a material: S = F/A
Stress
stress that causes material to increase in length (+deformation)
Tensile Stress
stress that causes material to reduce in length (-deformation)
Compressive Stress
the amount of deformation divided by the material’s original length: e = ΔL/L
Strain
observed when the applied loads are constant (not changing)
Static Properties
observed when the applied loads are changing: impact loads, fluctuating loads, time-dependent effects, etc.
Dynamic Properties
- Measures the behaviour of
a material with respect to a
tensile load - Uses the Universal Testing
Machine (UTM)
Uni-Axial Tensile Strength
- 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
The Engineering Stress-Strain Curve
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.
Linear elastic
occurs when the yield stress of the material
is reached.
Permanent (plastic) deformation
is defined as the ratio of the applied load, P, to the original cross-sectional area, Ao, of the specimen:
𝜎 = P/Ao
Engineering Stress (Nominal Stress)
e = (l-lo)/lo
Engineering Strain
As the specimen begins to elongate under a continuously increasing load, its cross-sectional area decreases ________ and _____________ throughout its gage length.
permanently, uniformly
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.
unloaded, straight line downward, parallel
the maximum engineering stress of the material.
Tensile strength or ultimate tensile strength (UTS)
If the specimen is loaded beyond its ultimate tensile strength, it begins to ____, or ____ down
neck, neck
the engineering stress at fracture
Breaking or fracture
- the ratio of stress to strain in the elastic region.
- the stiffness of the material
E = 𝜎/e (Hooke’s law)
Modulus of Elasticity (E) or Young’s modulus
the absolute value of the ratio of the
lateral strain to the longitudinal strain.
v = lateral strain/longitudinal strain
Poisson’s Ratio (v)
_____ materials show significant elongation before breaking/fracture.
Ductile
When materials fail with little or no ductility, they are said to be_____
Brittle
____ is simply the lack of ductility. Strong materials can be ____ and ___ materials can be strong
Brittleness, brittle, brittle
Also known as _________ – defined as the work per unit volume required to fracture a material.
Modulus of toughness
Upon continuous application of
a tensile force, a material ______
elongates
When a material elongates, that
means it reduces in __________
cross-sectional area
Since S = _____, that means, as the
material reaches its ultimate
and breaking strength, it gets
stronger and stronger.
- This phenomenon is called
________
F/A, Strain Hardening
The greater the capacity of a material to absorbed energy, the greater is its ___________
Damping Capacity
Measures the behaviour of a material with respect to a compression load
Compression Test
- 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.
Hardness Testing
Brinell, Rockwell, Vickers, Knoop ______ Tests
Hardness
- 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.
Brinell Harness Test, Brinell
- 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.
Rockwell Test
- 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.
Vickers Hardness Test
- 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.
Knoop Hardness Test
- Utilizes a diamond tipped hammer and drops it to the flat surface of
the material. - Measures resilience of the material
Scleroscope Test
- Files of different roughness are used to evaluate scratch sensitivity of
the material
File Test
Subjects the material to a rapidly applied load, or impact.
Impact Test
Material is loaded horizontally on the tool.
Charpy Test
Material is loaded vertically on the tool
Izod Test
There are materials which are _____-sensitive and ____-insensitive.
notch, notch
For notch-_____ materials, good surface finishing is key to good
performace.
sensitive
Notch-____ materials may be used for applications requiring rough
surface finishes
insensitive
From field data, 90% of material failure and breakages result from material _____
fatigue
The stress below which the material will not break no matter how many cycles it is applied is called the ________ or ________ of the material.
endurance limit, endurance strength
Fatigue Failures are caused by ________________ (beach marks)
successive micro-fractures
Temperature affects _____________
rate of deformation
- Some materials undergo a transition phase wherein they change from
ductile to brittle material, vice-versa. - Fracture Appearance Transition Temperature (FATT)
Ductile-to-brittle transition
- 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 _____
Creep
- ____________ 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.
Machinability
- The study of how an existing fracture or crack can be
prevented from spreading and ultimately breaking the
material. - Dormant vs Dynamic Fractures
Fracture Mechanics
