Classification of Materials
Which of these is a polymer?
A. Copper
B. Polyethylene
C. Glass
D. Alumina
Answer:
B.Polyethylene
What is the chemical symbol for iron?
A. Ir
B. In
C. Fe
D. I
C. Fe
Which property measures resistance to scratching or indentation?
A. Hardness
B. Density
C. Ductility
D. Conductivity
A. Hardness
What should an engineer consider first when choosing a material for a component?
A. Only its color
B. Only its brand name
C. The component's functional requirements
D. Only its melting point
C. The component's functional requirements
What is casting?
A. Cutting a solid part with a saw
B. Pouring molten material into a mold to solidify
C. Joining two parts with screws
D. Grinding a surface
B. Pouring molten material into a mold to solidify
Which material is generally classified as a ceramic?
A. Aluminum
B. Rubber
C. Silicon carbide
D. Brass
Silicon carbide
Which two elements are the main constituents of ordinary carbon steel?
A. Iron and carbon
B. Copper and tin
C. Aluminum and magnesium
D. Nickel and chromium
A. Iron and carbon
What does ductility describe?
A. Resistance to corrosion
B. Ability to undergo plastic deformation in tension before fracture
C. Ability to conduct electricity
D. Resistance to scratching
B. Ability to undergo plastic deformation in tension before fracture
Which material is commonly preferred when low mass is important in a lightweight structure?
A. Lead
B. Aluminum
C. Tungsten
D. Copper
B. Aluminum
What is the main purpose of heat treatment?
A. To change a material's properties through controlled heating and cooling
B. To change a metal into a polymer
C. To remove all carbon from every metal
D. To increase the size of a component
A. To change a material's properties through controlled heating and cooling
Which material is a composite?
A. Fiberglass
B. Pure copper
C. Pure aluminum
D. Soda-lime glass
A. Fiberglass
Which elements are the main constituents of brass?
A. Iron and carbon
B. Copper and zinc
C. Copper and tin
D. Iron and chromium
B. Copper and zinc
What does Young's modulus measure?
A. Density
B. Fracture toughness
C. Elastic stiffness
D. Melting temperatur
C. Elastic stiffness
Which material is often suitable for a component exposed to a corrosive environment?
A. An appropriate corrosion-resistant stainless steel
B. Unprotected low-carbon steel in every environment
C. Pure sodium
D. Untreated iron in seawater
A. An appropriate corrosion-resistant stainless steel
What is the main difference between casting and forging?
A. Casting uses only plastic materials.
B. Forging always involves melting the metal.
C. Casting shapes molten material, while forging shapes metal using compressive forces.
D. Both processes require the material to remain liquid throughout.
C. Casting shapes molten material, while forging shapes metal using compressive forces.
Which class of materials generally has the highest electrical conductivity?
A. Ceramics
B. Polymers
C. Foams
D. Metals
D. Metals
What is the main role of chromium in many stainless steels?
A. To make the steel transparent
B. To eliminate all heat expansion
C. To turn the steel into a polymer
D. To improve corrosion resistance
D. To improve corrosion resistance
What is toughness?
A. Resistance to electrical current
B. Ability to recover only its original shape
C. Mass per unit volume
D. Ability to absorb energy before fracturing
D. Ability to absorb energy before fracturing
Why might a designer choose a polymer for an electrical cable's insulation?
A. Because all polymers conduct electricity extremely well
B. Because polymers are always stronger than steel
C. Because polymers cannot be damaged by heat
D. Because many polymers provide electrical insulation and flexibility
D. Because many polymers provide electrical insulation and flexibility
What is the purpose of quenching steel?
A. To reduce its density to zero
B. To make it electrically insulating
C. To melt the steel completely
D. To rapidly cool it and potentially increase its hardness
D. To rapidly cool it and potentially increase its hardness
Why are carbon-fiber composites widely used in aerospace structures?
A. They always cost less than steel.
B. They offer high stiffness and strength relative to their weight.
C. They are always more ductile than metals.
D. They conduct heat better than every metal.
B. They offer high stiffness and strength relative to their weight.
In a metal alloy, what is a solute element?
A. The element that must be a gas
B. An element that is always present in the greatest amount
C. An element dissolved in the base material to form a solid solution
D. A separate tool used to shape the alloy
C. An element dissolved in the base material to form a solid solution
Why can a high-strength ceramic still fail suddenly under impact?
A. Because ceramics always melt at room temperature
B. Because many ceramics have low fracture toughness and limited plastic deformation
C. Because ceramics have no atomic bonds
D. Because all ceramics are softer than polymers
B. Because many ceramics have low fracture toughness and limited plastic deformation
Two candidate materials meet a component's strength requirement. One is lighter but much more expensive. What is the best engineering approach?
A. Always choose the lighter material.
B. Always choose the cheaper material.
C. Compare performance, cost, safety, service life, and design constraints.
D. Choose randomly because both meet the strength requirement.
C. Compare performance, cost, safety, service life, and design constraints.
How can the grain structure of a metal affect its mechanical properties?
A. It determines only the color of the metal.
B. Grain size and structure can affect strength, ductility, and toughness.
C. It has no effect on mechanical properties.
D. It determines only the comp
B. Grain size and structure can affect strength, ductility, and toughness.