Cold Filament Failure
Definition
Fracture of a tungsten bulb filament below operational temperature; characterised by a clean, brittle transverse fracture with no deformation and no oxide layer, confirming the headlight was off at impact.
- Condition
- Filament fractures below operating temperature
- Fracture type
- Clean, brittle, transverse
- Absence
- No deformation, no oxide layer
- Conclusion
- Headlight was off at moment of impact
Common questions
How does a hot filament failure look different under examination?+
A filament that was glowing at impact stretches and deforms from the heated tungsten's ductility, and it often develops localised oxidation or fusion where the hot filament contacted air or glass, both signs entirely absent in a cold, brittle break.
Why does headlight filament condition matter in accident reconstruction?+
It establishes whether a vehicle's lights were on or off at the moment of collision, which bears on visibility, driver conduct, and sometimes contested claims about which vehicle had its headlights on before a nighttime crash.
Related terms
- ASTM E2927
- Standard test method for the determination of trace elements in glass samples using LA-ICP-MS; specifies the element suite, calibration standards (NIST SRM...
- BNS 2023 § 106
- Bharatiya Nyaya Sanhita 2023 provision criminalising causing death by negligence; the primary charging provision for fatal hit-and-run cases in India, with enhanced...
- EUCAP
- European Collection of Automotive Paints, maintained at the Bundeskriminalamt (BKA) in Wiesbaden; the European counterpart to PDQ for automotive hit-and-run paint comparison.
- FCIN
- Forensic Collision Investigation Network (UK); provides standardised protocols for fatal and serious-injury collision forensic examination, including paint, glass, tyre and filament examination.
- Hot Filament Failure
- Fracture of a tungsten bulb filament while at operational temperature (2,500-3,000 K); characterised by ductile deformation at the break, coiling, and tungsten...
- LA-ICP-MS
- Laser ablation inductively coupled plasma mass spectrometry; a technique that fires a laser pulse at a sample surface, vaporises a tiny amount,...
- PDQ (Paint Data Query)
- RCMP-maintained international automotive paint database. Stores binder, pigment and layer data for vehicle original-equipment finishes from major manufacturers. Used to narrow a...
- PVB Interlayer
- Polyvinyl butyral film bonding the two glass layers in a laminated automotive windshield; retains broken glass in place after fracture, preserving the...
- SWGTREAD
- Scientific Working Group for Shoeprint and Tire Tread Evidence; US body that developed the dominant guidelines for footwear and tyre-mark examination, class-subclass-individual...
- Treadmate
- RCMP database of outsole designs for footwear comparison, used by Canadian forensic laboratories and accessible to partner agencies.
- Tungsten Trioxide (WO3)
- Pale yellow oxide of tungsten formed rapidly at temperatures above approximately 800 K when tungsten is exposed to atmospheric oxygen; its presence...