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Status Report, Vol. 37, No. 6 | June 8, 2002 Subscribe

New sled will simulate crashes, expand testing

There's something new at the Institute's Vehicle Research Center — a sled on fixed rails that can simulate the decelerations that occur inside a passenger vehicle compartment during the 100 milliseconds or so of a crash.

The Institute's sled, named the HyperG, is a new design. It's the first one produced for sale by a joint venture of U.S. and Austrian companies, Seattle Safety and DSD. "The HyperG gives us an important supplement to our vehicle crash testing program. It will allow us to evaluate vehicle components plus other components like child seats and safety belts, without the expense of full-vehicle crash testing," explains David Zuby, Institute vice president and engineer.

The pattern of decelerations over time in a crash is referred to as a crash pulse. Zuby says the Institute "can re-create various crash pulses quickly and run numerous sled tests in the time it takes to prepare for and conduct one full-vehicle crash test. The pulses the sled can simulate cover those that can occur in a range of crashes from low to relatively high speeds."

Initial tests

The first research program slated for the HyperG will be an international effort to develop dynamic procedures for comparing whiplash injury risk among seat and head restraint designs. This program is part of an effort by the International Insurance Whiplash Prevention Group (IIWPG), of which the Institute is a member, to compare and rate various seat/head restraint designs (see "Institute to begin dynamic testing with new sled," Oct. 6, 2001). Other IIWPG members include three European research groups — Allianz Technology Center and the Institute for Vehicle Safety, both in Germany, plus the United Kingdom's Motor Insurance Repair Research Centre at Thatcham. As part of the cooperative research effort to evaluate seats and head restraints, Thatcham is acquiring its own HyperG sled.

IIWPG has settled on BioRID for sled tests of seat/head restraint combinations. Another rear impact dummy option would have been RID2 which, like BioRID, has a more humanlike neck and spine than the Hybrid III dummy designed for frontal testing. Until recently, BioRID was the only commercially available rear-impact dummy. RID2 was a prototype.

"Whiplash injuries are relatively minor. They usually result in short periods of pain but sometimes long-term pain. In many countries these are the most common crash injuries, so the cost is high — billions of dollars in insurance claims in the United States alone," Institute president Brian O'Neill points out.

The HyperG won't be just for whiplash research. Zuby says it's "appropriate for many different kinds of research. It's useful for simulating any kind of crash where there's not significant risk of injury from deformation or intrusion of the vehicle itself. When intrusion is a risk, you need to crash the whole vehicle. But when crash forces alone are sufficient to evaluate a component, then sled tests make sense because they're so much faster and less expensive to conduct."

How it works

Sled testing has been an important aspect of vehicle research for years. Like most sleds, the HyperG works something like a catapult. The sled itself is a steel flatbed that runs on fixed rails. Vehicle seats and other components are fixed to the sled for testing.

To simulate a crash, compressed air is pumped into a special cylinder, thrusting a ram forward. The ram launches the sled with a preprogrammed pattern of acceleration (crash pulse). Because the sled is accelerated, while the vehicles in frontal crashes are decelerated, the seat and other vehicle components being evaluated are mounted on the sled facing backwards for frontal tests. The HyperG's hydraulic brakes control the force that launches the sled. Compared with other sleds that rely on complicated hydraulic systems, the HyperG's design makes it simpler to program to run different crash pulses.

"The sled can be operated very quickly," Zuby says. "But it takes a little more time to set up the dummies and cameras for a test. We could run as many as 10 tests a day, depending on their complexity. Front, side, and rear impacts all can be simulated by changing the orientation of the sled components."

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