AUDI Material Selection & Properties 2 — Questions and Answers
Question 1: Audi uses hot-formed ultra-high-strength steel (UHSS) in structural areas primarily because it offers:
- Lower cost than mild steel
- Tensile strength exceeding 1,500 MPa with reduced weight (Correct answer)
- Better corrosion resistance than aluminum
- Easier weldability in body repair
Correct answer: Tensile strength exceeding 1,500 MPa with reduced weight
Hot-formed UHSS achieves tensile strengths above 1,500 MPa, enabling thinner gauges that reduce vehicle weight while maintaining crash performance.
Question 2: Which welding process is typically required when repairing Audi's press-hardened steel (PHS) components?
- MIG welding at standard settings
- Resistance spot welding only, per OEM specifications (Correct answer)
- Oxy-acetylene welding
- TIG welding with argon shielding
Correct answer: Resistance spot welding only, per OEM specifications
Press-hardened steel must be joined using resistance spot welding at OEM-specified parameters to avoid heat-affected zone embrittlement.
Question 3: Audi's Audi Space Frame (ASF) design uses aluminum extrusions joined to cast aluminum nodes. What property of aluminum castings makes them suitable for these nodes?
- High tensile ductility
- Ability to form complex three-dimensional shapes with integrated attachment points (Correct answer)
- Superior fatigue resistance compared to extrusions
- Lower density than aluminum sheet
Correct answer: Ability to form complex three-dimensional shapes with integrated attachment points
Cast aluminum nodes can be produced in complex 3D geometries that integrate mounting points and load-transfer features impossible to achieve with extrusions alone.
Question 4: When Audi specifies a 5xxx-series aluminum alloy for a body panel, what is the primary alloying element?
- Copper
- Silicon
- Magnesium (Correct answer)
- Zinc
Correct answer: Magnesium
The 5xxx-series aluminum alloys use magnesium as the primary alloying element, providing good corrosion resistance and moderate strength.
Question 5: Which material property is most critical when selecting a brake disc material for an Audi high-performance application?
- Low coefficient of thermal expansion
- High thermal conductivity and heat capacity (Correct answer)
- High tensile strength
- Low density
Correct answer: High thermal conductivity and heat capacity
Brake discs must absorb and dissipate large amounts of heat rapidly, making thermal conductivity and heat capacity the primary selection criteria.
Question 6: Audi's carbon fiber reinforced polymer (CFRP) roof panels are bonded rather than welded. What adhesive characteristic is most critical for this joint?
- Rapid cure at room temperature
- High peel and shear strength with flexibility to absorb vibration (Correct answer)
- Electrical conductivity for grounding
- Resistance to UV radiation only
Correct answer: High peel and shear strength with flexibility to absorb vibration
Structural adhesives for CFRP-to-metal joints must provide high peel and shear strength while remaining flexible enough to accommodate differential thermal expansion.
Question 7: In an Audi multi-material body, what is the purpose of applying a structural foam insert inside certain steel pillars?
- To reduce NVH by damping vibration and increasing section stiffness (Correct answer)
- To prevent rust formation inside the cavity
- To reduce electrical conductivity
- To act as a firewall between compartments
Correct answer: To reduce NVH by damping vibration and increasing section stiffness
Structural foam inserts expand inside pillars during the paint oven cycle, bonding to the metal walls to damp vibration and stiffen the cross-section without adding significant weight.
AUDI Material Selection & Properties 2
Audi uses hot-formed ultra-high-strength steel (UHSS) in structural areas primarily because it offers: