17 September 2009

New simulation process boosts safety performance

Crash tests are often key components to creating a safer product. Now a new simulation process that factors in deformation during production as well as preliminary damage can predict the results of a crash test more accurately than ever.

Take a look at a car. If a car rolls over during an accident, the ‘B-pillar’ plays a key role. It forms one of the connections between the floor and roof of the vehicle, and it should prevent the passenger cell from deforming too much. The materials from which manufacturers make the B-pillar need to meet very exacting requirements: to save fuel they need to be ultra-lightweight, yet at the same time need to be tremendously strong and must not break. Yet, what does the optimum component actually look like? With the aid of countless experiments, simulations, and crash tests, the auto industry has been getting closer to answering this question.

Engineers will usually carry out a range of virtual tests with known materials properties providing the basic knowledge in such a scenario.

“We are well aware of the physical and mechanical characteristics of the materials in their original state,” said Dr. Dong-Zhi Sun, group leader at the Fraunhofer Institute for Mechanics of Materials IWM. However, during the course of the manufacturing process, components change—with a B-pillar, for instance, the material goes through a complicated manufacturing chain. As it is deformed and stretched, minor damage such as pore formation may occur. “If you’re going to fit these kinds of parts into vehicles, you need to take into account their deformation history during manufacture,” Sun said.

That is why researchers have developed a new method. “With our failure model, we can simulate manufacturing processes more effectively,” Sun said. “To ensure we understand the manufacturing processes inside out, we work together closely with automakers and materials producers.”

With the simulation method, researchers can precisely model and analyze the deformation of the component during manufacture. So they know to what extent the process affects the properties of the end product, and whether the manufacturing process gives rise to potential preliminary damage such as pore formation and microcracks. Engineers can combine the results of the process simulation with a crash simulation, conducted using a newly developed material model.

The new method enables components with optimum properties and improved crash performance to undergo development. “Unlike conventional crash simulations, we can predict far more accurately how extensively the component will deform during the crash before it fails,” Sun said.

For related information, go to www.isa.org/safety.