Overview
ISO/TR 12351:1999 - "Road vehicles - Determination of head contact and duration in impact tests" provides standardized methods to identify the instant of head contact and the duration of that contact during vehicle impact tests. Determining head engagement and disengagement times is essential for calculating the contact Head Injury Criterion (HIC). The report describes three approaches (calculation, visual/film analysis and electrical contact) and identifies the preferred technique where suitable instrumentation is available.
Key topics and technical requirements
- Purpose: Establish time windows of head contact used to compute contact HIC values (HIC calculated from the head centre-of-gravity resultant acceleration-time profile).
- Recommended (calculation) method:
- Requires a test device (full, partial or simulated dummy) equipped with triaxial head accelerometers and an upper neck load cell with a minimum of three force channels (Fx, Fy, Fz).
- Acceleration components are multiplied by head mass (M) to form inertial forces; neck forces from the load cell are subtracted to derive the external resultant contact force.
- Signals filtered using CFC 1000 (filtering per ISO 6487) before computing resultants.
- Contact threshold: head contact occurs when resultant external contact force exceeds 500 N. Engagement time (te) and disengagement time (td) are found using a 200 N search level before/after the 500 N crossing.
- Visual (film) method:
- Uses high-speed cameras (recommended ≥1 000 frames/s) and synchronized time bases (resolution at least 1/100 s, error