All set for big bangs

This collision box folded up in an exemplary way after impact with the yellow test car. Photo: Rune Petter Ness

Using collision rigs and high-speed cameras, researchers can find out what happens during a high-speed impact.

By Even Gran

When the test vehicle, weighing three quarters of a tonne – as much as a car – impacts at 50 or 60 kph, reliable equipment is needed to register what happens when the test structure is smashed. Everything happens very quickly. It is impossible for the human eye to register what occurs in the time between that moment when the vehicles crashes and the metal is scattered, twisted and distorted. Yet what actually happens to the structure is the most interesting aspect of the impact for the Structural Impact Lab. at the Department of Structural Engineering at NTNU, which has two high-speed cameras for this purpose. These can take up to 60 000 images a second – enough to document everything that happens during a crash or an explosion.

Lots of customers
Daimler-Chrysler, Ford, Audi, Renault and Fiat, all want to make use of this new collision rig, which is the only one of its kind in Scandinavia and is finally ready for use. Most tests consist of sending the test vehicle, which weighs as much as a standard car, at full speed towards so-called collision boxes. These are small aluminium tubes 30 to 40 centimetres long that are constructed to absorb shocks. Such collision boxes are found in-between the bumper and the chassis in most new cars, as well as in other places.
The aim is to make the collision box absorb as much as possible of the energy released in a crash, thus preventing damage to the chassis. It is important to make sure that the collision box is not knocked to one side when there is an impact, but folds up neatly. This is easier to achieve if the collision boxes are filled with aluminium foam. The effect of this foam is one of a number of research projects that are being carried out in the Department, in cooperation with Hydro Aluminium and the automative industry.

These images show what happens when a projectile hits and exits an apple.

Photographing rifle bullets
The Department of Structural Engineering already has a high-speed camera that can record images at 1/20 000 000 of a second. This camera cannot store more than 24 images at a time so is not suited for use in the collision rig. It is used to image projectiles which are shot at various obstacles at extremely high speed so that the resistance of different materials can be tested.

Contact at NTNU: Professor Magnus Langseth
Tel: +47 73 59 47 82
Email: Magnus.Langseth@bygg.ntnu.no