Tech Briefs
Twin track safety for Volvo

The new Volvo Cars Safety Center. A schematic of Volvo's new crash laboratory, including rollover, two car crash test, and real traffic environment testing. Diagram of Volvo's crash simulator system. The Volvo crash simulator. A simulated collision with an elk

Volvo has created a new Safety Center that includes two tracks measuring 154 m (505 ft) and 108 m (354 ft)—one of which can be swiveled through 90° to facilitate car-to-car impacts from full frontal to right-angle crashes. "We can simply move the reality of the roads into our crash laboratory," said Stefan Nilsson, the center's Director.

Aircushions are used to move the 600-t (660-ton) track. A 0.1-mm (0.004-in) layer of air is created between the concrete floor and 20 rubber aircushions. Six specially designed trucks then move the track. Cars under test are accelerated via two 1800-kW (2450-hp) electric motors per track connected with 18-mm (0.71-in) steel cables via a drum. Laser instrumentation is used for position measurement. This information is transferred to the electric motors, which ensure that the cars collide at exactly the right position and speed. Some 2 m (6.6 ft) before point of impact, the cars run freely. For barrier tests only the fixed track is used. Again, the aircushion system is used to move an 850-t (937-ton) block. The fixed track can also be used for rolling tests that involve pulling the car in the opposite direction out onto a track where it does several rollovers. A crash into a ditch or into a mountainside can also be simulated. The new facility has 30 high-speed cameras and there are two photo pits for under-vehicle recording.

In an accident a car may rotate and move vertically simultaneously. According to Volvo, no simulation has so far succeeded in taking this into account. However, it says that this type of "pitch" can be simulated in the Safety Center's new crash simulator. The sledge runs on two rails that allow vertical movement. At the instant of impact, hydraulics pull down the front end of the platform carrying the car, thus simulating the pitch movement of a true frontal impact. The sledge then continues along the rails and comes to a standstill when the simulation is over. Volvo claims as "another world first" the facility's ability to simulate the deformation of the front bulkhead between the engine and passenger compartments in a severe frontal impact. This is done with the help of an intrusion actuator system that can most easily be described as 10 hydraulic pistons programmed to intrude into the passenger compartment via selected parts of the bulkhead. Up to 10 crash tests per week can be performed on a complete car. The new crash simulator was designed and built by MTS Systems Corp. to meet Volvo's specifications.

Other rigs at the new Center include a Free Motion Head and a Dynamic Impactor Test System to simulate the effects of impacts on torso, legs, and knees. The work includes pedestrian/hood impacts. Drop test rigs of 18 m (59 ft), 7 m (23 ft), and 2.5 m (8.2 ft) are installed. Artificial body parts are dropped onto test objects including dashboards and door panels. Volvo uses an NEC SX-4 supercomputer for virtual testing.

Stuart Birch