Analysis of a Frontal Rail Structure in a Frontal Collision

In the course of developing a body-on-frame vehicle for barrier crash performance, automotive manufacturers must take into account numerous regulatory and corporate requirements. One of the most common barrier crash modes is the perpendicular front barrier crash used to verify compliance to F/CMVSS 208. The frontal rail or “horn” is the primary component that absorbs a significant amount of the vehicle's crash energy. The frontal rail collapse determines the vehicle deceleration.

This paper evaluates several frontal horn designs for perpendicular front barrier impacts. Two basic frontal rail architectures are evaluated: a uniform rectangular cross section and a tapered cross section. For a 35 mph (15.65 m/s) impact test condition, a parametric design study was commenced to evaluate the affect of gauges, convolutions, triggers, and initiating holes for a total of eleven configurations. The study optimizes performance utilizing peak acceleration measured at the vehicle rocker at the B-pillar, front rail weight and energy dissipation.

Based on these parameters listed above, the tapered frontal horn design utilizing initiating inboard triggers on the rail cross section is considered to be the optimal configuration.