Session: 14-04-02: Reliability and Safety in Transportation Systems II

Paper Number: 142194

142194 - Automotive Seat Back Strength Testing of 19 Front Seats 

Automotive front seat back strength in rearward loading has been researched and reported on for over fifty years.  In rear impacts the seat back provides the primary means of restraint to the occupant as the force of the collision causes the occupant to move rearward, away from their seatbelt webbing.  Seat strength requirements for vehicles Certified to be sold in the United States are prescribed in Federal Motor Vehicle Safety Standard (FMVSS) 207.  If the seat belt is attached to the seat frame, commonly referred to as an All Belts to Seat (ABTS) design, the seat must also meet the seat belt anchorage requirements of FMVSS 210.  The strength requirements of automotive seats have remained unchanged for several decades.

This paper describes the fabrication of a wooden body block, first designed, and used, in static seat back strength testing in the 1960’s, and a hydraulically actuated testing rig with instrumentation recording synchronized force and displacement measurements.  A six-seat repeatability study was undertaken where six seats of the same design were tested and the force versus displacement curves were analyzed for consistency prior to testing eighteen different seat designs.  Results of the current testing are added to previously reported seat back strength test results to identify trends in automotive seat back strength.

The nineteen seats tested were selected in groups by their parent vehicle sales classification.  Seventeen seats from vehicles sold in the United States D segment (mid-size) sedan, luxury sedan, and pickup-truck classifications were identified, seats located, and tested.  Also tested were two seats produced in two models of vehicles built by the same manufacturer, one was designed and manufactured by a long-standing Tier One automotive supplier of seats and interior trim components, the other was designed and manufactured in-house by the Original Equipment Manufacturer (OEM).  One of the tested seat frames has features in the seat back bracket that are designed to control the deflection in rear impacts.  The design of this feature changed during the production run of the seat frame design.  Seats with the original and modified bracket features were tested.  Maximum force and the force versus deflection curves are compared between the Tier One and OEM designed seats and the original and modified seat back brackets. 

The results of this study show the test fixture produced repeatable results.  The study adds to the available seat back strength test results reported in previous literature; adding these results to previous testing shows how seat back strength has changed throughout the past 60 years.

Presenting Author: Peter Leiss Robson Forensic, Inc.

Presenting Author Biography: PJ is an expert in vehicle engineering and crash reconstruction. He commonly investigates and testifies in matters pertaining to vehicle crashworthiness, vehicle performance/handling dynamics, and crash reconstruction.
As a vehicle engineer with Dodge, PJ was involved in the entire lifecycle of vehicle design and manufacture. He designed and engineered systems for concept vehicles, tuned and validated systems on prototype vehicles, resolved manufacturing issues during production, and made improvements to enhance vehicle quality and safety after the start of manufacture.
Outside of the office, PJ is active in restoring classic cars and building/maintaining vehicles for personal and motorsports use. He has been “restomodifying” an older vehicle with modern suspension, brakes, interior, and powertrain. He has also participated in track days and helped to build and campaign a race car in the National Auto Sport Association, American Iron Series.

Authors:

Peter Leiss Robson Forensic, Inc.
Christopher Roche Robson Forensic, Inc.
Marcus Mazza Robson Forensic, Inc.
Roland Hoover Robson Forensic, Inc.