Symposiums & Conferences

Abstract:The US, European and Australian New Car Assessment Program (NCAP) and the Insurance Institute for Highway

Safety (IIHS) produce ratings of new vehicle performance based on dynamic crash tests in frontal, side and rear crashes; and vehicle handling tests. No dynamic based crashworthiness ratings exist to date in relation to rollover crashes. This study fills that gap and proposes a rating system for new vehicle performance in rollover crashes. Combined with existing rating systems, consumers will then have a complete and balanced picture of occupant protection performance.

A database of more than 40 Jordan Rollover System (JRS) dynamic rollover tests, assessing injury potential by roof crush and crush speed has generically validated NHTSA and IIHS statistical data as a function of FMVSS 216 quasi-static, strength to weight ratio (SWR). There is however a wide disparity between the performance of individual vehicles at the same or similar SWR between the IIHS statistical and JRS dynamic test data. That disparity has been partially investigated in a companion paper in this conference (Vehicle Roof Geometry and its Effect on Rollover Roof Performance.

IIHS data indicated a 50% reduction in incapacitating and fatal injury risk with a fleet average SWR = 4. However, the use of a SWR-based rollover criterion does not provide sufficient crashworthiness fidelity essential for consumers, nor does such a criterion provide industry the opportunity to design cost-efficient rollover crashworthy vehicles based on occupant injury performance. Only a dynamic rollover testing protocol based on injury criteria would provide this information.

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Abstract:Nearly a half century ago, the General Motors Research Laboratories, developed the high performance Electrovair, with an induction motor drive and solid state controller; the Lunar Rover, GM’s Mark on the Moon; passive occupant protection; separation cruise control; optical lane following; and an electrochemical rechargeable Lithium Iodine engine.

In 1968, a new company called Minicars grew out of this earlier work. This group developed prototype electric, gas and hybrid electric powered versions of a small car for the U.S. government. In 1970, Minicars was a subcontractor to AMF for the development of its Experimental Safety Vehicle.

The Minicars’ Research Safety Vehicle (RSV) was conceived in 1975 as a 1985 prototype. It was to be an S3E vehicle: Safe, Environmental, Efficient and Economical. It was built with foam filled, thin wall sheet metal sections and a polyurethane skin. This car passively protected occupants in 80 kph (50 mph) full frontal, 129 kph (80 mph) half car offset frontal, 64 kph (40 mph) angled side, rear and 48 kph (30 mph) rollover dynamic tests. An electronic version incorporated antilock brakes, radar separation cruise control, and emergency braking when a crash was unavoidable. A production version was to weigh 2,200 pounds, carry four people, and get 32 mpg. It also had 16 kph (10 mph) frontal and rear no damage bumpers and 80 km (50 mile) run flat tires.

Only years later have advanced air bags – as featured in the RSV – become standard in all light vehicles. In the decades since the ESV program and dynamic regulatory testing began, National Highway Traffic Safety Administration (NHTSA) now estimates that airbags save 2,500 lives annually, but we still lose about 12,000 people in frontal, 9,000 in side and over 10,000 in rollover crashes. We can do better by simply looking back to what the RSV program achieved.

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Abstract:The Jordan Rollover System (JRS) provides a realistic, highly controlled, repeatable dynamic test of vehicle roof crush performance under typical rollover conditions. The principal use thus far has been in comparing vehicles’ roof crush and injury potential performance in one and two roll events. Because the JRS directly measures the force between the roof and the ground during touchdown, it can be used to measure, assess and optimize occupant protection by adjusting roof geometry, roof structural design and material strength and elasticity, for the least cost and weight.

This study demonstrates that the peak force (load) between the initial leading side roof rail (near side) and the road is roughly four times the vehicle weight (the load-to-weight ratio or LWR) when a vehicle first touches down at around 150º of roll. The force then drops substantially as the vehicle continues to roll over the flat of the roof, in most instances dropping to zero because the vehicle is momentarily airborne. When the vehicle rolls beyond 180º and comes into contact with the side rail opposite to the leading side of roll (far side), the force rapidly rises again. The roof then either collapses or lifts the vehicle center of gravity (COG). The far side rail of a weak roof vehicle that cannot lift the COG may then halt the vehicle’s downward fall, imposing even larger forces on the road segment when the vehicle’s door and main body structure interact with the roadway. To deal with such forces, a long standing and natural presumption has been to substantially increase the roof strength to weight ratio (SWR), which can result in weight efficiency cost penalties. However, one production vehicle that was tested minimized roof crush without substantially increasing its SWR.

Analysis of the results has found that far side roof crush is strongly related to the difference between the major radius (the maximum distance from the principal axis of rotation to the roof rail) and minor radius (distance from that axis to the center of the roof). Three to four inches, as between cars and LTV’s has a significant effect on injury potential. The typical difference in a light truck vehicle LTV is around 15 cm to 25 cm (6” to 10”) while in an passenger car it is around 8 cm to 15 cm (3” to 6”).

These observations were confirmed by physical tests of strong and weak roofed vehicles. These tests led to the conclusion that a geometry change in the roof to minimize the difference in radius across the roof would reduce the degree to which the far side of a less strong roof had to lift the vehicle as it rolled beyond 180º. A finite element analysis confirmed that for a vehicle of modest roof strength, a structurally strong, rounded roof panel will reduce the far side deformation and intrusion speed by about two-thirds without increasing underlying roof strength. These results were confirmed in JRS testing of current production passenger cars and SUV vehicles and with a “HALO” TM – High Attenuation Load Offset (U.S. and International Patent Pending Rollover Damage Minimization Device) retrofit kit for SUVs.

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Abstract:In the U.S., more than 27,000 catastrophic and fatal injuries occur annually in rollovers. This study is part of an ongoing research project aimed at mitigating the likelihood and severity of such injuries.

Last year, the authors developed a dynamic rollover test methodology for replicating, predicting, and differentiating between types of real-world neck injuries using the non-biofidelic Hybrid III dummy as the human surrogate. Based on platen drop and pendulum test results, dummy positioning for flexion injury was determined and peak neck injury measures were rejected. A new neck injury criteria, the integrated bending moment (IBM), was proposed that related human neck flexion injury to Hybrid III lower neck moment-time histories. The IBM was validated by dynamic rollover tests performed with the Jordan Rollover System (JRS) with roofs of different strength-to-weight ratios (SWR's). The measured lateral and flexion neck moments were then roughly correlated with human neck flexion injury measures proposed by Pintar, et al., in 1998.

To date, real-world head injuries resulting from roof interaction and partial ejection could not be replicated in dynamic rollover tests with the non-biofidelic Hybrid III dummy because of stiffness differences between the Hybrid III and human neck.

Findings thus far suggest that improved correlations with human injury measures could be achieved with the development of a dummy neck that is biofidelic in the rollover crash mode. In this paper, the production Hybrid III neck was modified with lower durometer butyl rubber discs and nodding blocks for improved biofidelity. Pendulum tests were repeated to correlate the production and modified Hybrid III neck responses. JRS tests were performed with an increased far-side impact angle to evaluate the capability of the modified preflexed neck to replicate and predict head, neck, thoracic spine, and ejection injury potential in real-world rollovers.

Results of this study indicate the following:

Matched-pair platen pendulum tests with the low-durometer neck were found to be repeatable.

In JRS tests performed with an increased far-side impact angle, the low-durometer preflexed Hybrid III neck reasonably replicated head, neck, thoracic spine, and ejection injuries and kinematics of weak-roofed vehicles.

The low-durometer neck allowed a more direct correlation with human neck flexion injury measures.

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Abstract:Rollover accidents have the highest serious to fatal injury rates of any accident mode. Research and development on rollover occupant protection has been frustrated by the lack of a low cost, controlled, repeatable, dynamic test. The most widely used tests, dolly and CRIS system rollovers, do not meet all of these conditions, but the Jordan Rollover System (JRS) does. This study demonstrates JRS repeatability using three identical production vehicles with anthropomorphic test dummies. The first test of each vehicle used string potentiometers to measure roof performance. The second used both string potentiometers and an instrumented test dummy. The JRS test parameters, roof structural performance, and Hybrid III dummy injury measures were all shown to be highly repeatable with variation generally not more than 10 percent. The dummy and vehicle repeatability was on par with the repeatability shown in similar crash test studies conducted by IIHS and NHTSA.

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Abstract: World renowned expert engineers will meet to debate the cause of injury in a rollover (Diving vs. Roof Intrusion) and to expose the weak U.S. government standard that has led to more than three decades of unnecessary fatalities and catastrophic injuries in rollover accidents. Although the experts supporting the “Diving Theory” have declined to participate, the debate will go on with their testimony under oath on this issue. Other topics of discussion will be Ejection, Severity, Testing, Regulation, Injury Measures, Disabled Living & Spinal Cord Injuries, Societal Costs, Defense and Plaintiff Strategies, Public Information, NCAP, and International Cooperation. Engineers who have studied the issue of Roof Crush in depth will present scientific papers and videos of roof drop test comparisons and vehicle rollover comparisons of strong roofs vs. weak roofs. Survivors of Roof Crush will tell their stories.

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Abstract:In an attempt to find a test protocol that characterizes the rollover occupant protection capability of a passenger vehicle better than the test used in Federal Motor Vehicle Safety Standard 216, we developed equipment and protocols for a modified, quasi-static roof crush test (M216, a test conducted sequentially on both sides of the roof over the A pillars at a pitch angle of 10º and roll angles of 25° and 40° respectively) and for a repeatable, dynamic rollover test called the Jordan Rollover System (JRS).

We have conducted M216 and JRS tests on 17 production vehicles to determine roof crush and crush velocities at a number of points in the interior. These tests included complete production vehicles, body bucks at reduced weight to increase the effective roof strength-to-weight ratio, and pairs of identical vehicles where one has had the roof reinforced in a manner that is entirely hidden by the vehicle’s sheet metal and upholstery. Data from the JRS tests and the M216 tests are compared with the results of FMVSS 216 tests.

Analyses of the data highlight the relative value and validity of each test methodology, its ability to predict roof performance in actual rollovers, its use in vehicle roof structure design, and its potential contribution to regulation or consumer information. Based on the roof crush and crush speed in the vicinity of front seat occupants’ heads, we propose a rollover crashworthiness ranking system. While static tests measure the force and deformation of the roof on the outside, the dynamic tests measure the crush on the inside during the sequence of rollover roof impacts, where it is directly related to the occupant’s survival space and injury potential. .

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Abstract:In an attempt to understand the relationship between quasi-static and dynamic test results, repeatable, dynamic rollover tests were conducted on production vehicles to determine intrusion and intrusion velocities using the Jordan Rollover System (JRS). These tests included complete production vehicles and body bucks at reduced weight, to vary the roof strength-to-weight ratio. Data from these tests are compared with the results of quasi-static roof strength tests measured at greater roll and pitch angles than are used in FMVSS 216. Biomechanical data indicates that serious head, face, neck or thoracic spine injury are a consequence of rapid impacts with significant amplitude. The test data suggests a correlation between quasi-static roof strength and dynamic roof intrusion velocity. Localized failures (buckling and collapse of structural elements that often translate into the roof panel) are a more critical aspect of roof performance than its strength as measured in FMVSS 216.

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Abstract: Public release of previously confidential Malibu test data and film [1] provides the basis for this review. These are sixteen well-instrumented, definitive 32 mph dolly rollover tests of production Chevrolet Malibu sedans with unbelted Hybrid III dummies and eight with belted dummies (half of the cars in each group had roll cages to simulate strong roofs). This paper analyzes and reinterprets this material to resolve the principal motivating research question: does a strong roof reduce the potential for rollover head and neck injuries? Our findings are: (1) a rolling vehicle’s center of gravity rises and falls only about 10 cm during a rollover so that its vertical velocity at roof impact is never more than 2.5 m/sec; (2) the six dummies showing the highest head and neck forces were all seated on the far side of Malibus without roll cages; (3) these high head and neck loads occurred after onset of roof intrusion from rapid roof collapse and buckling, not from occupant diving; (4) average roof impact neck forces measured by near side dummies and by far side dummies seated under roofs that did not contact the ground all averaged 3,300 to 3,600 N, and none was sufficient to cause serious injury; (5) the unrestrained Hybrid III dummy drop tests showed that neck loads of 7,000 N correspond to a 2.4 m/sec roof intrusion velocity while 3,500 N neck loads corresponds to a 1.1 m/sec intrusion velocity; (6) the windshields of the production vehicles broke early leaving weakened roof structures that deformed back and forth with subsequent roof impacts; and (7) the tempered side glazing of production Malibus broke far more frequently than in rollcaged vehicles facilitating partial or complete ejection. The Malibu tests provide considerable insight into the potential countermeasures that could reduce rollover injuries.

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