Volvo views offset crash tests

Gothenburg, Sweden -When it comes to automobile crash testing, computer simulations are only as good as the input data. That's why the new Volvo Car Corp. Center, which was officially inaugurated on 29 March 2000, is equipped with a crash test barrier capable of measuring offset impacts. Designed by Kistler Instrumente AG (Winterthur, Switzerland), the new barrier's corner segments measure the magnitude of forces applied along the x-, y-, and z-axes.

Until now, mandatory crash testing involved only full frontal crashing into a large and rigid concrete block. Performance requirements for the instrumentation of such crash test barriers are relatively straightforward. Their specifications do not call for separate measurements of the force vectors acting on the crashed body. These measurements, however, are critical when simulating offset frontal crashes.

"If only part of the front of a vehicle makes initial contact with the object it strikes, there is a tendency for the car's tail to slide sideways," explains Kistler Market D ivision Manager Thomas Berther. "This can significantly alter the force distribution and hence the collapse mode of the initial contact zones, and subsequently others as these are being crumpled."

To gather this data, Volvo's crash test barrier incorporates two corner segments. Each segment consists of five force-measuring elements capable of measuring, simultaneously in two directions, forces as high as 1.5 MN. Orthogonal top plates and a series of quartz piezoelectric sensors make up each corner element.

As with the crash test barrier's front force measuring elements, output from the sensors pass to a charge amplifier box mounted on a base plate. A common bus controls the charge amplifiers and measurements are fed to the acquisition computer in the form of analog signals.

In order to satisfy every possible test requirement that might involve corner elements having radii ranging from 2 to 200 mm, the modular design allows quick changeout of the corner elements without changing the quartz force sensors. In addition, a special force shunt accommodates the high load requirements, transferring the major force component directly to a steel structure.

Berther points out that the corner segments, as with all of Kistler's crash test barriers, use quartz sensors instead of strain gauge load cells. Durability, no recalibration requirements, and the ability to handle a wide range of forces and masses are the primary reasons.