Material Selection & Properties Flashcards

Which heat treatment process is used to increase the hardness and wear resistance of Audi crankshaft bearing journals?

Answer: Induction hardening

Induction hardening selectively heats only the bearing journal surface, creating a hard martensitic layer while leaving the core tough and ductile.

Audi uses magnesium alloy for certain engine components such as the crankcase. What is the biggest material handling concern with magnesium during machining?

Answer: Magnesium chips and dust are highly flammable and can ignite spontaneously

Magnesium swarf and fine dust are extremely flammable and can ignite spontaneously, requiring dry-chemical fire suppression and strict housekeeping procedures.

What distinguishes a thermoplastic from a thermoset polymer used in Audi interior and exterior components?

Answer: Thermoplastics can be remelted and reshaped; thermosets cannot

Thermoplastics soften and can be reprocessed when heated, while thermosets undergo irreversible cross-linking during curing and cannot be remelted.

Audi specifies titanium fasteners in certain high-performance applications. Compared to steel fasteners of the same size, titanium offers:

Answer: Approximately 45% lower density with comparable tensile strength

Titanium's density is about 4.5 g/cm³ versus steel's ~7.8 g/cm³, roughly 45% lighter, while high-grade titanium alloys match or exceed many steel grades in tensile strength.

Which rubber compound is most suitable for Audi's turbocharger intake hoses that must withstand sustained temperatures up to 200°C?

Answer: Silicone rubber (VMQ)

Silicone rubber retains flexibility and sealing properties across a wide temperature range from -60°C to over 200°C, making it ideal for high-temperature turbo hoses.

The tensile strength of a steel alloy is 800 MPa and its yield strength is 650 MPa. What does the difference between these values indicate?

Answer: The steel has a plastic deformation range before fracture, indicating ductility

The gap between yield and tensile strength represents the plastic deformation capacity of the material, which is a measure of its ductility and energy absorption ability.

Audi uses phosphate coating on steel body parts before painting. What is the primary function of this process?

Answer: To improve corrosion resistance and paint adhesion

Zinc or iron phosphate coatings create a conversion layer that improves both corrosion protection and the mechanical bond between the steel substrate and subsequent paint layers.