79 Questions
What type of strength is the ability of a piece of sheet metal to withstand stress in tension?
Tensile strength
Which definition of tensile strength refers to the stress at which material changes from elastic deformation to plastic deformation?
Yield strength
What is the maximum stress a material can withstand when subjected to tension, compression, or shearing?
Ultimate strength
Which coordinate on the stress-strain curve represents the stress at the point of rupture?
Rupture (or fracture)
What term refers to the measure of how a metal reacts to a specific type of loading?
Tensile strength
In which region of the stress-strain curve does material strain change from elastic to plastic deformation?
Yield strength (elastic limit)
Which type of loading does bending strength specifically refer to?
Bending
What is the technical term for the maximum stress a material can withstand before rupturing?
Ultimate strength
What property refers to a metal's tendency to return to its original shape after normal stretching and bending?
Elasticity
Which property measures a material's resistance to tearing or breaking when bent or stretched?
Toughness
What enables a metal to carry heat or electricity?
Conductivity
What is the ability of a metal to expand when heated and shrink when cooled called?
Thermal Expansion
Examples of metals that must be both tough and hard are:
Hammer faces and wrenches
Which property is the measure of a material's ability to allow electron flow?
Conductivity
What must a metal first do before it can carry heat away from its source?
Absorb heat
Metals that can carry heat also carry electrons, making them good:
Electrical conductors
What is the primary focus of the text?
Explaining the different types of metallic strengths
What is the relationship between tensile strength and hardness in steel?
They are directly proportional
Which of the following is NOT listed as a fundamental loading force?
Ductility
What does the term 'fatigue strength' refer to?
A metal's ability to withstand repeated loading
What property of metals is described as their ability to resist shock?
Impact strength
What is the relationship between tensile strength and hardness for most metals?
The relationship is not absolute
What does the term 'necking' refer to in the context of the stress-strain curve?
The localized reduction in cross-sectional area before fracture
What is the ability of a metal to resist rotational shear called?
Torsional strength
What characteristic does tungsten add to steel when alloyed?
High melting point
What are typical applications of tungsten steels?
Control surface balance weights and breaker contacts
Which property do titanium steel alloys possess?
High tensile strength and toughness
What is a key characteristic of stainless steel?
Corrosion resistance
Which materials are stainless steels suitable for in aircraft applications?
Firewalls and exhaust system components
What is the purpose of heat treating steel?
To modify strength, toughness, and ductility
Which material is NOT suitable for use as a structural material without modification?
Pure iron
What is the primary alloying element in steel that allows it to be heat-treated?
Carbon
How is normalising different from annealing?
Normalising involves cooling in still air, while annealing involves cooling in the furnace.
Why is normalising important in aircraft work?
To reduce the internal stresses and strains in welded parts.
What is the key factor determining the maximum hardness attained by carbon steel during hardening?
The uniform dispersion of carbon in the steel.
How does hardening steel differ from normalising and annealing?
Hardening involves rapid cooling after uniform dispersion of carbon, while normalising and annealing do not require rapid cooling.
What is one method of quenching steel during the hardening process?
Quenching in water, oil, or brine.
Why are stresses relieved in ferrous metals by normalising?
To prevent failure due to internal stresses.
What is an important use of normalising in aircraft work?
To relieve internal stresses and strains in welded parts.
What happens to carbon steel during hardening?
Steel is rapidly cooled after uniform carbon dispersion.
What is the term used to describe the predictable expansion or contraction of materials at specific temperatures?
Thermal expansion coefficient
What is the ability of metal to be joined by heating and melting called?
B and C
Which of the following is NOT considered a ferrous metal?
Aluminum
What is the chief constituent of ferrous metals?
Iron
What is the term used to describe iron poured from a furnace into molds?
Cast iron
What is a characteristic of iron in its pure form?
It is silvery white in color and quite heavy
What is the primary reason why iron is usually mixed with various forms of carbon and other alloying agents or impurities?
To prevent it from readily combining with oxygen to form rust
What is the typical composition of cast iron?
More than 2% carbon and some silicon
What is the primary benefit of alloying chromium with steel?
Increases strength and hardness
What is a common application of chromium steel?
Antifriction bearings
What is the purpose of alloying nickel and chromium with steel?
Enhances high-strength structural applications
Which property does molybdenum impart to steel when alloyed?
Reduced grain size and increased impact strength
What is a common application of chrome-molybdenum steel?
Both b and c
What property does vanadium impart to steel when alloyed with chromium?
Enhanced ductility
What is a common application of chrome-vanadium steel?
Ball bearings
Which alloying element is NOT mentioned in the text?
Manganese
What property of metals is the opposite of ductility and malleability?
Brittleness
Which type of metal is more likely to break or crack before changing its shape?
Brittle metal
What is the property that describes a metal's tendency to return to its original shape after normal stretching and bending?
Elasticity
Which metals are examples of brittle ferrous metals?
Cast iron and very hard steel
What is the point beyond which a metal does not return to its original shape after a deforming force is removed?
Elastic limit
Which type of metal is more likely to exhibit elasticity in its behavior?
Hard spring steel
What is the term used to describe a material's resistance to breaking or shattering when bent or stretched?
Brittleness
What is the primary purpose of heat treating steel?
To alter the steel's physical and mechanical properties
What is the process of annealing steel?
Heating and cooling steel to relieve internal stress and soften it
Which alloying element is most important for the heat treatment of steel?
Carbon
What makes high-carbon steels particularly suitable for heat treatment?
They respond well to the heat treatment process
What is the primary advantage of heat treating steel in manufacturing processes?
It increases the strength and other desirable characteristics
Which statement about the different heat treatment processes is true?
Each heat treatment process provides different desirable characteristics
What is the primary reason for the commercial use of steels exceeding that of any other material?
Steels can be heat treated to improve their properties
What is the primary effect of annealing on steel?
It softens the steel and relieves internal stress
What is the purpose of normalizing steel?
To relieve internal stresses and strains
How does the hardening process for carbon steel differ from normalizing?
Hardening involves rapid cooling by quenching
What is the primary factor determining the maximum hardness of carbon steel during hardening?
The carbon content of the steel
What is an important application of normalizing in aircraft work?
Welded parts
How does the cooling process differ between normalizing and annealing?
Normalizing involves cooling in still air, annealing in a controlled environment
Which quenching medium is NOT mentioned for hardening carbon steel?
Air
What happens to the carbon particles in steel during the annealing process?
They precipitate out into larger particles
Which statement about normalizing steel is NOT true?
It allows carbon particles to precipitate out into larger sizes
Study Notes
Types of Strength
- There are several types of strength, including:
- Tensile strength: ability of a metal to withstand stress in tension
- Compressive strength: ability to withstand being pressed or squeezed
- Shear strength: ability to withstand shear stress
- Torsional strength: ability to resist rotational shear
- Bending strength: ability to withstand bending forces
- Fatigue strength (endurance strength): ability to resist repeated loading
- Impact strength (toughness): ability to resist shock
Tensile Strength
- Yield strength: stress at which material strain changes from elastic deformation to plastic deformation
- Ultimate strength: maximum stress a material can withstand
- Breaking strength: stress coordinate on the stress-strain curve at the point of rupture
- Reference numbers on the stress vs strain curve for structural steel include:
- Ultimate strength
- Yield strength (elastic limit)
- Rupture (or fracture)
- Strain-hardening region
- Necking region
Toughness
- Ability of a material to resist tearing or breaking when bent or stretched
- Examples: hammer faces and wrenches
Conductivity
- Ability of a metal to carry heat or electricity
- Examples: fins on cylinder heads of an air-cooled piston engine
- Metals that can carry heat also carry electrons, making them good electrical conductors
Thermal Expansion
- Ability of a metal to expand when heated and shrink when cooled
- Metals expand when heated and contract when cooled
Hardness
- Ability of a metal to resist cutting, penetration or abrasion
- Related to tensile strength, but not absolute
- Examples: tungsten, titanium
Metals
- Ferrous metals: contain iron as chief constituent
- Examples: steel, cast iron, alloys of iron with other metals
- Properties: corrosion resistance, high strength, high ductility
- Non-ferrous metals: do not contain iron
- Examples: aluminum, copper, titanium
- Properties: high strength-to-weight ratio, corrosion resistance, high ductility
Properties of Metals
- Brittleness: tendency to break or shatter when exposed to stress
- Elasticity: ability to return to original shape after normal stretching and bending
- Conductivity: ability to carry heat or electricity
Heat Treatment
- Process of heating and cooling carbon steel to change its physical and mechanical properties
- Types of heat treatment:
- Annealing: softens steel and relieves internal stress
- Normalising: relieves internal stresses in ferrous metals
- Hardening: increases hardness of carbon steel
Alloying Elements
- Chromium: increases strength, hardness, and corrosion resistance of steel
- Molybdenum: increases strength, toughness, and corrosion resistance of steel
- Vanadium: produces strong, tough, ductile steel alloys
- Nickel: toughens steel, increases corrosion resistance
Test your knowledge on different types of strength in materials, including tensile strength, compressive strength, shear strength, torsional strength, bending strength, fatigue strength, and impact strength. Understand how each type of strength measures the ability of a metal to react to specific types of loading.
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