High strength steel and extra reinforcement a new design of side impact beam improves crashworthiness and helps the automotive industry to lower the weight of its products and rationalise production.

The automotive industry is constantly striving to lower the weight of its products, improve crashworthiness and rationalise production. The German company Dura Automotive Body and Glass Systems has met all of these three objectives with a new design of side collision protection beam manufactured from ultra-high strength steel with reinforcement. The company has also developed a system for volume production of the beams.

As a result, the new collision protection beam has been nominated for the Swedish Steel Prize 2005 international industrial award.

Advanced high strength steel is an obvious material for safety components of cars - it makes it possible to produce different types of crash protection components that are not only lightweight but also have high energy absorbing capacity.

Side impact beams using advanced high strength steels are currently fitted as standard to the vast majority of cars, although the design is far from standardised.

There are many different designs - certain carmakers use pressed open profiles, some employ tubular designs, and others use profiles that have welded-on reinforcements.

Naturally, the optimum solution is a side impact beam capable of being produced in large volumes that can be used for a number of different car models with only minor modifications.

This has been the basic objective of Dura's development work.

Another fundamental condition was the use of ultra-high strength Docol 1200 M steel that has good weldability and good roll forming properties.

The steel has a minimum tensile strength of 1200N/mm2, which makes it one of the most advanced high strength steels available on the market.

All safety parts in a car must be provided with very effective anti-corrosion treatment, which can be achieved by using zinc electroplated Docol 1200 M steel.

The patented Dura side impact beam is a closed square-section profile that is necked on the sides.

The design of the profile has been optimised to provide the side impact beam with very high energy absorption capacity.

The thickness of the steel in the beam is only 2 mm, which results in a weight of 1.75kg for a 1.1 metre long beam.

But Dura designers were not content with merely achieving the good basic properties provided by this type of beam.

They realised that the properties could be improved still further by adding a 200-300mm long reinforcement in the middle of the beam.

This is where the stresses are highest in the event of a crash.

The reinforcement increases the weight by only 200 grams, but enables the deformation of the beam to be optimised in a side collision situation.

'We tested virtually every type of material for the reinforcement,' recalls Torsten Hundt from Dura, whose responsibility it was to test the prototypes.

'The extra reinforcement of ultra-high strength steel enabled us to make the beam much stronger'.

'But in safety work, efforts are often also made to achieve controlled energy absorption in which the beam deforms more but without failing'.

'We found that a reinforcement of a certain type of plastic material produced just these properties.' The type of reinforcement that is suitable for a particular car is dependent on the safety philosophy of the carmaker.

Certain car manufacturers give priority to closely controlled deformation, whereas others specify maximum strength.

'Depending on the safety philosophy, the beams can be tailored to suit the requirements by varying the type and length of reinforcement,' adds Meinhard Schwermann who participated in the work at Dura.

The type of mounting can also be varied.

Depending on the remainder of the design, the beam can be fixed to the door by riveting, welding or securing with screws.

The benefit to the carmaker is that the beam can readily be adapted to several different variants of a given car model.

In parallel with the development of the beam and the various types of reinforcement, Dura has created a highly efficient production system.

All operations take place on a production line in which the steel runs in a continuous strip directly from the coil.

The bottom part of the profile is first roll formed, and the reinforcements are then placed in position.

The profile is then closed and joined together by laser welding.

The beam is finally cut to the appropriate length.

The reinforcement is secured to the profile in different ways depending on the type - steel reinforcements are spot welded during roll forming, whereas plastic reinforcements are gripped by the necking on the sides.

Dura Automotive Systems is one of the world's leading producers of components and systems for the automotive industry.

The group of companies is based in the USA, but has development and production units in all corners of the world and their list of customers includes all major American and European carmakers.

The Group has a total of 17 000 employees and its turnover is US$ 2.5 billion.

The new side collision beam has been developed in Germany by Dura Automotive Body and Glass Systems in Plettenberg.

The beam will be produced in the company's factory in Blatna in the Czech Republic, where the beam production line came on stream in the autumn of 2005.