Dynamic Response of Vehicle Roof Structure and ATD Neck Loading During Dolly Rollover Tests 2010-01-0515

The debate surrounding roof deformation and occupant injury potential has existed in the automotive community for over 30 years. In analysis of real-world rollovers, assessment of roof deformation and occupant compartment space starts with the post-accident roof position. Dynamic movement of the roof structure during a rollover sequence is generally acknowledged but quantification of the dynamic roof displacement has been limited. Previous assessment of dynamic roof deformation has been generally limited to review of the video footage from staged rollover events.

Rollover testing for the evaluation of injury potential has typically been studied utilizing instrumented test dummies, on-board and off-board cameras, and measurements of residual crush. This study introduces an analysis of previously undocumented real-time data to be considered in the evaluation of the roof structure's dynamic behavior during a rollover event. A series of dolly rollover tests (Forester Test Series) were conducted on both concrete and compacted dirt surfaces. The test vehicles, 2003 Subaru Foresters, had a roof strength-to-weight ratio (SWR) of 4.8 ( Summers, 2005 ), among the highest of all vehicles NHTSA has tested to date. The vehicles were instrumented with accelerometers and angular rate sensors to measure the vehicle kinematics and dynamics. The vehicles were also instrumented at the A- and B-pillars with strain gages, accelerometers, and string potentiometers to document the dynamic loading and motion of the pillars at the roof rail junctions. High-speed and real-time video cameras visually documented vehicle motions and roof deformation. The third test in the Forester Test Series, conducted on a dirt surface, included Anthropomorphic Test Devices (ATDs) in the front seating positions to assess the interactions of the ATDs within the occupant space. This paper presents innovative techniques and data analysis that include the dynamic measurement of roof displacement, acceleration, and strain using polar plots and video synchronized with data.