CAE Materials Science in Automotive 2

Question 1

Which heat treatment process produces a hard martensitic surface layer while keeping the core tough in automotive gear components?

Accepted Answer

Case hardening

Answer

Case hardening (carburizing + quenching) creates a high-carbon martensitic surface with a ductile low-carbon core, ideal for gears.

Question 2

What is the primary reason aluminum alloys are used in automotive engine blocks instead of cast iron?

Accepted Answer

Lower density reducing vehicle weight

Answer

Aluminum's density (~2.7 g/cm³) is about one-third that of cast iron (~7.2 g/cm³), offering significant weight savings.

Question 3

Which composite material architecture offers the highest in-plane stiffness-to-weight ratio for automotive structural panels?

Accepted Answer

Unidirectional (UD) fiber laminate

Answer

Unidirectional laminates align all fibers along the load axis, maximizing specific stiffness compared to other fiber architectures.

Question 4

In the iron-carbon phase diagram, what phase exists at room temperature in a slowly cooled 0.8% carbon steel?

Accepted Answer

Pearlite

Answer

A 0.8% C steel is eutectoid; slow cooling through 727°C transforms all austenite to pearlite (alternating ferrite and cementite lamellae).

Question 5

Which mechanism is responsible for age hardening (precipitation hardening) in aluminum alloys used in automotive structural components?

Accepted Answer

Coherent precipitate strain fields impeding dislocation motion

Answer

Fine coherent precipitates (e.g., GP zones, θ' in Al-Cu) create strain fields that act as barriers to dislocation glide, increasing strength.

(CAE) Certified Automotive Engineer Practice Test