Podcast
Questions and Answers
Which of the following is NOT a type of engineering material?
Which of the following is NOT a type of engineering material?
What characteristic is NOT associated with metals?
What characteristic is NOT associated with metals?
What is the structural arrangement of atoms in a solid metal called?
What is the structural arrangement of atoms in a solid metal called?
What is formed when two or more metals are combined?
What is formed when two or more metals are combined?
Signup and view all the answers
Which of the following materials is an example of an alloy?
Which of the following materials is an example of an alloy?
Signup and view all the answers
What happens to the atoms in a metal when it solidifies from a molten state?
What happens to the atoms in a metal when it solidifies from a molten state?
Signup and view all the answers
Which of the following can be considered a characteristic of metals?
Which of the following can be considered a characteristic of metals?
Signup and view all the answers
What type of applications can metals NOT be used for?
What type of applications can metals NOT be used for?
Signup and view all the answers
What is the primary alloying element in steel?
What is the primary alloying element in steel?
Signup and view all the answers
What is the maximum carbon limit for commercial steels?
What is the maximum carbon limit for commercial steels?
Signup and view all the answers
Which of the following materials is too weak for engineering applications?
Which of the following materials is too weak for engineering applications?
Signup and view all the answers
What characteristics make cast iron difficult to fabricate using techniques like rolling or shearing?
What characteristics make cast iron difficult to fabricate using techniques like rolling or shearing?
Signup and view all the answers
In what applications is pure iron typically used?
In what applications is pure iron typically used?
Signup and view all the answers
What is the minimum carbon content required for a material to be classified as steel?
What is the minimum carbon content required for a material to be classified as steel?
Signup and view all the answers
Which of the following statements correctly defines carbon steel?
Which of the following statements correctly defines carbon steel?
Signup and view all the answers
Which material is recognized for being brittle when carbon content exceeds 2%?
Which material is recognized for being brittle when carbon content exceeds 2%?
Signup and view all the answers
What is one of the primary advantages of powdered metallurgy (P/M)?
What is one of the primary advantages of powdered metallurgy (P/M)?
Signup and view all the answers
Which manufacturing method can achieve up to 98% of wrought material properties?
Which manufacturing method can achieve up to 98% of wrought material properties?
Signup and view all the answers
What is used in the compacting process of powdered metallurgy?
What is used in the compacting process of powdered metallurgy?
Signup and view all the answers
Which of the following is NOT utilized in the powdered metallurgy process?
Which of the following is NOT utilized in the powdered metallurgy process?
Signup and view all the answers
What is one of the primary materials mentioned in relation to low melt temperature metals?
What is one of the primary materials mentioned in relation to low melt temperature metals?
Signup and view all the answers
Which is a key benefit of using nonferrous metals in manufacturing?
Which is a key benefit of using nonferrous metals in manufacturing?
Signup and view all the answers
Which component is commonly produced using powdered metallurgy methods?
Which component is commonly produced using powdered metallurgy methods?
Signup and view all the answers
What is achieved by sintering parts after the compaction process in powdered metallurgy?
What is achieved by sintering parts after the compaction process in powdered metallurgy?
Signup and view all the answers
What is a characteristic of polymers?
What is a characteristic of polymers?
Signup and view all the answers
Which of the following is a type of thermoplastic?
Which of the following is a type of thermoplastic?
Signup and view all the answers
What property do amorphous thermoplastics exhibit?
What property do amorphous thermoplastics exhibit?
Signup and view all the answers
What is a disadvantage of polymers for high temperature applications?
What is a disadvantage of polymers for high temperature applications?
Signup and view all the answers
Which of the following is NOT a typical application of polymers?
Which of the following is NOT a typical application of polymers?
Signup and view all the answers
How do thermosetting polymers behave at high temperatures?
How do thermosetting polymers behave at high temperatures?
Signup and view all the answers
Which characteristic is NOT associated with crystalline thermoplastics?
Which characteristic is NOT associated with crystalline thermoplastics?
Signup and view all the answers
What describes the mechanical properties of amorphous polymers near their glass transition temperatures (Tg)?
What describes the mechanical properties of amorphous polymers near their glass transition temperatures (Tg)?
Signup and view all the answers
What characteristic of crystalline thermoplastics contributes to their strength and stiffness?
What characteristic of crystalline thermoplastics contributes to their strength and stiffness?
Signup and view all the answers
Which of the following is a property of liquid crystalline plastics (LCPs)?
Which of the following is a property of liquid crystalline plastics (LCPs)?
Signup and view all the answers
How does the melting point of semicrystalline polymers compare to entirely crystalline polymers?
How does the melting point of semicrystalline polymers compare to entirely crystalline polymers?
Signup and view all the answers
What is the impact of adding plasticizers to a polymer mix?
What is the impact of adding plasticizers to a polymer mix?
Signup and view all the answers
Which property is associated with the amorphous phase present in crystalline polymers?
Which property is associated with the amorphous phase present in crystalline polymers?
Signup and view all the answers
What effects can mixing different types of polymers have on plastics?
What effects can mixing different types of polymers have on plastics?
Signup and view all the answers
Which material is NOT typically used as a particulate filler to modify plastic characteristics?
Which material is NOT typically used as a particulate filler to modify plastic characteristics?
Signup and view all the answers
What property of amorphous/crystalline blends is dependent on the proportions of the blend?
What property of amorphous/crystalline blends is dependent on the proportions of the blend?
Signup and view all the answers
What is the primary advantage of using higher-molecular-weight resins?
What is the primary advantage of using higher-molecular-weight resins?
Signup and view all the answers
Which factor influences the choice of molecular weight for injection-molding applications?
Which factor influences the choice of molecular weight for injection-molding applications?
Signup and view all the answers
Which additive is specifically mentioned as being required to meet fire safety standards?
Which additive is specifically mentioned as being required to meet fire safety standards?
Signup and view all the answers
What property do fillers and modifiers provide to plastics?
What property do fillers and modifiers provide to plastics?
Signup and view all the answers
For thin-walled injection-molding applications, which molecular weight grade is preferable?
For thin-walled injection-molding applications, which molecular weight grade is preferable?
Signup and view all the answers
Which polymer is described as having a structure composed of acrylonitrile, butadiene, and styrene?
Which polymer is described as having a structure composed of acrylonitrile, butadiene, and styrene?
Signup and view all the answers
What term is used to describe the total weight of individual atoms in a polymer molecule?
What term is used to describe the total weight of individual atoms in a polymer molecule?
Signup and view all the answers
What role do additives like UV stabilizers play in plastics?
What role do additives like UV stabilizers play in plastics?
Signup and view all the answers
Study Notes
ID 2322 Materials & Production - Week 2
- Course: Materials & Production
- Institution: National University of Singapore
- Division: Industrial Design
- College: Design and Engineering
- Level: BA(ID) 2
- Semester: 1
- Module Leader: Kouo Wai Chiau
- Email: [email protected]
Engineering Materials
- Engineering materials are classified into four categories: Metals, Polymers, Ceramics, Composites.
- These materials differ significantly in structure, properties, and applications.
Metals
- Structure: Crystalline (atoms arranged in a regular pattern).
- Appearance: Opaque, lustrous (shiny).
- Conductivity: Good electrical and thermal conductors.
- Shape Change: Capable of changing shape permanently under external forces (ductility).
- Strength & Stiffness: Relatively high strength and stiffness.
- Alloy: Formed when two or more metals are combined.
- Common Examples: Copper, Aluminum, Gold, Steels, Brasses, Bronzes (copper + tin), Bell metal (copper + tin), Sterling silver (silver + copper), Nichrome (nickel + chromium), Super alloys.
- Applications: Car bodies, tin cans, construction, rails, engine blocks, wires, cabinets, valves.
The Nature of Metals
- Metals are defined as solids made up of atoms held together by an electron matrix.
Structure of Metals
- Molten state: atoms arranged randomly.
- Solid state: atoms arrange in a regular 3D pattern (space lattice).
- Unit cell: the smallest repeating unit in the space lattice.
- Common unit cells: body-centered cubic (BCC), face-centered cubic (FCC), hexagonal close-packed (HCP).
Types of Unit Cells (Lattice Structures)
-
BCC: High melting point, high yield strength, but low ductility. Examples include tungsten, molybdenum, vanadium.
-
FCC: More open-spaced arrangement, ductile and easily deformed. Examples include copper, aluminum, lead, nickel, silver, gold, and iron.
-
HCP: Found in less common metals (beryllium, zinc, titanium, magnesium, zirconium). Wide spacing between basal planes leads to low plasticity. Brittleness readily arises upon deformation at room temperature.
-
Electrical properties: Electrons are free to move throughout the crystal, making them good conductors.
-
Other properties: Malleability (ability to deform plastically), opacity (light cannot pass through), and ability to be strengthened.
-
Cleavage failure: Crystalline solids subjected to loads may try to split atoms apart when bonds are very strong.
-
Atomic slip: In metals, loading can cause slip rather than cleavage.
-
Dislocations: Atomic in size, observed with microscopic and etching techniques. Sources include crystal mismatch in solidification, external stresses (like plastic deformation), phase transformations, and alloying elements.
-
Strengthening Mechanisms: Dislocation interactions, solid solution strengthening (adding impurity atoms), mechanical working (multiplicating dislocations), and precipitation hardening.
Additional Metal Types
- Precious Metals: Rhodium, Sterling silver, 14k/18k yellow/rose gold, 14k nickel/PD white gold, palladium, platinum.
- Ferrous Metals: Iron based metals.
- Nonferrous Metals: Not based on iron (i.e. copper, aluminum, magnesium, zinc)
Steel
- Steel: An alloy of iron and carbon (typically 0.06% to 2.0% carbon).
- Pure Iron: Soft, ductile, relatively weak. Used for applications like magnetic devices and enameling.
- Cast Iron: Contains more than 2% carbon, too brittle for rolling, forming, shearing, or other fabrication techniques. Primarily used for castings.
Steel Production & Processing
- Refining iron ore and limestone is heated with coke in a blast furnace; removes impurities.
- Molten iron is transported to steel-making furnaces.
- Ingot teeming, soaking, pits, continuous casting, shaping (billets, slabs, blooms, skelp), rolling, drawing are part of steel product processing.
Different Forms of Steel Products
- Sheet, Bar, Coil, Flat wire, Shapes, Tin plate, Wire, Free machining, Drawing quality, Merchant quality, Pickling.
Stainless Steel
- A minimum of 10.5% chromium is the key alloying element.
- Categorized by microstructure: austenitic, ferritic, martensitic, precipitation hardening.
Types of Nonferroous metals
- Aluminum.
- High strength-to-weight ratio, good formability.
- Corrosion resistance due to an oxide coating.
- Electrical conductivity.
- Copper
- Ease of forming, joining, good electrical and thermal conductivity, attractive color, high corrosion resistance.
- Brass and Bronze: Copper alloys used extensively in plumbing and fine art casting.
- Magnesium:
- Excellent combination of low density and good mechanical strength, giving high strength-to-weight ratio.
- Commonly used in transportation, power tools, etc.
- Zinc alloy: Used for die-cast components in a wide range of products (automotive, building hardware, industrial tools, and toys). Also used as a coating for steel (galvanized steel) to prevent corrosion.
Powdered Metallurgy (P/M)
- Provides new processes and alloys for weight reduction and enhanced mechanical properties.
- Applications include sports, electronics, office equipment, automotive parts, and off-road vehicles.
- Steps involve atomization of molten metal, mixing, compacting, and sintering.
Metal Injection Moulding (MIM)
- Hybrid technology combining plastic injection molding and powder metallurgy.
- Economical method for mass manufacturing of small intricately shaped components.
- Results in components with 95-98% of wrought properties at reduced cost.
Polymers
- Structure: Long molecular chains of carbon atoms.
- Weight: Typically light weight.
- Conductivity: Low electrical and thermal conductivity.
- Common Examples: Polyamide, polyvinyl chloride (PVC), polystyrene, ABS, rubber, nylon.
-
Applications: Carrier bags, plumbing pipes, hoses, tires, domestic items.
- Specific applications often involve thermosets, thermoplastics, or blends thereof.
- Types: Thermoplastics, Thermosets, and Composites.
Types of Polymers
-
Thermoplastics: Can be melted and reshaped repeatedly.
- Amorphous (no long-range order), Crystalline (long-range order), Liquid Crystalline Polymers (LCPs).
- Thermosets: Can be molded only once. - These, with their cross-linking, inhibit crystallizations.
Copolymers and Blends
-
Copolymers: Polymers composed of two or more different monomers.
- Types: Random, Alternating, Block, Graft.
- Applications can differ significantly from the homopolymers.
-
Blends: Mechanical mixing of two or more polymers.
- Applications include polymers with balanced characteristics such as strength and flame resistance.
Terpolymers
- Polymers with three different repeating units. Tailored for wide ranges of properties.
- Example: ABS - acrylonitrile, butadiene, styrene.
Molecular Weight
- Sum of weights of the atoms that make up the polymer molecule.
- Indicates the average length of polymer chains.
- Variation in molecular weight affects plastic properties, including viscosity and performance.
Additives
- Fillers (glass, minerals) - change properties (aesthetic, resistance, conductivity).
- Plasticizers - reduce stiffness and increase flexibility.
- Flame retardants - comply with safety regulations.
- UV stabilizers - counteract degradation from UV light.
Factors Affecting Mechanical Properties
- Weld lines: Grooves in molded parts due to flow front join; they weaken the part.
- Residual Stress: Uneven cooling, differential shrinkage cause stresses in parts.
- Ultimate Strength: Property related to the alignment of polymer chains; may vary depending on the direction.
Ceramics
- Formed from metal and nonmetal (oxygen, nitrogen, or carbon).
- Brittle, high compressive strength.
- Good heat resistance. insulating properties. Common examples: refractories, glasses, concrete, silica, magnesium oxide, and fireclays.
- Applications include: cookware, electrical insulators, cutting tools, and building materials.
Composites
- Combo of two or more materials, creating unique properties not found in individual materials.
- One material (matrix) holds another material (reinforcement).
- Examples include fibrous (e.g., roof covers) and particulate (e.g., cermets) composites.
- Benefits often include strength and light weight, but varies with types (fiber, matrix, and manufacturing process).
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
