Vehicle Construction, Materials, and Collision Repair Fundamentals
What this domain tests
This domain tests vehicle construction, material identification, and repair decisions that preserve crash energy management. Expect questions on unibody load paths, steel grades, aluminum, sectioning limits, and heat sensitivity.
Core rules
- Body-on-frame uses a frame and separate body; unibody uses welded panels, rails, aprons, pillars, and rockers as load paths.
- The occupant safety cage uses high-strength steel (HSS), advanced high-strength steel (AHSS), ultra-high-strength steel (UHSS), and boron/martensitic grades; mild steel is more ductile.
- Heat softens many HSS/UHSS grades; use OEM heat limits, and never heat a boron part unless the procedure allows it.
- Aluminum panels need dedicated tools, aluminum-specific fasteners, and isolation from steel to prevent galvanic corrosion.
- Sectioning is allowed only at OEM-defined locations with specified joints, welds, rivets, and corrosion protection.
Worked example
A 2020 sedan has a dented B-pillar. The OEM procedure identifies the pillar as boron/UHSS and prohibits heat and sectioning. The technician replaces the pillar at factory joints using specified welds and corrosion protection. Reasoning: the pillar is a safety-cage load path; softening or an unapproved section can change crash performance, so procedure beats appearance.
Traps
Treating all steel as mild steel; using heat to straighten a high-strength part; skipping galvanic isolation on aluminum; assuming a bolt-on panel is never structural; ignoring one-time fasteners.