Influence of retractor and anchor pretensioning on dummy responses in 40 km/h rear sled tests

This study compared dummy kinematics and biomechanical responses with and without retractor pretensioning in a severe rear sled test. It compliments an earlier study with buckle pretensioning.

Three rear tests were run at 40 km/h (25 mph) delta V with a lap-shoulder belted Hybrid III 50^th male dummy on a 2013-18 Ford Escape driver seat and belt restraint. One test was with the lap-shoulder belts only, a second with retractor and anchor pretensioning and a third with only retractor pretensioning. The head, chest and pelvis were instrumented with triaxial accelerometers. The upper and lower neck, thoracic spine and lumbar spine had transducers measuring triaxial loads and moments. Lap belt load was measured. High-speed video recorded different views of the dummy motion. Dummy kinematics and biomechanical responses were compared to determine the influence of retractor belt pretensioning.

The dummy kinematics and biomechanical responses were essentially similar with and without retractor or retractor and anchor pretensioning in rear sled tests. There was an initial spike in lap belt load with pretensioning, but it did not result in different dummy head, neck or chest responses. In the tests, the dummy moved rearward away from the shoulder belt. The belts were tightened with the rapid pull on the webbing by pretensioning. The dummy loaded the seat, which yielded rearward restraining its motion. There was no significant effect of pretensioning on the dynamics of the dummy until late in rebound.

There were no significant differences in dynamics of the Hybrid III with and without retractor or retractor and anchor pretensioning in a 40 km/h (25 mph) rear sled test. Belt pretensioning did not influence biomechanical responses in the rear impact because the seat supported the dummy.