Measuring the vibration in car panels to reduce metal fatigue

With each new vehicle, the car industry faces a fresh battle to cut out the unwanted vibrations that cause irritating rattles and the metal fatigue that can cause parts to break, with potentially lethal consequences.

The complexity of the problems persuaded the German automobile giant BMW to team up with smaller partners to find a new way of designing new vehicles. It got together with Belgian companies LMS International, a world market leader in noise and vibration engineering, optics specialist Labor Dr Steinbichler and the Free University of Brussels in the EUREKA project HOLO-MODAL.

HOLO-MODAL has developed a new way of measuring the way car body panels vibrate that combines traditional vibration measurement with the latest holographic techniques.

Traditional measurement of vibration relies on attaching sensors to a test panel. However, it only measures the vibration at the sensor and attaching too many sensors changes the way the panel moves, altering the results. To gain an accurate picture of the whole panel’s response to vibration, you need to be able to see the effect on every part of the panel’s surface at the same time and without affecting the results. This is where holographic techniques come in.

Holographic analysis avoids physical contact with the test panel by illuminating the whole panel with a laser beam. By measuring the light that is reflected by the panel, the system produces a high-resolution 3-dimensional image of the whole surface as it vibrates.

The HOLO-MODAL partners designed a software package that combines traditional and holographic techniques, controls the hardware and shows how to incorporate the technique into early design work. Now car makers can design body panels that are safer, more durable and save development costs spent on vibration and noise control.

The computer models developed from the measurement data allow the effect of any design changes to be predicted and hence they allow users the chance to try out alternative solutions “on the computer” before actually building them In this way the system helps the development of design solutions.

This new technology can also be used to help design a new generation of safer, more durable and quieter domestic and office appliances and consumer electronic products.

Dr Herman van der Auweraer, project leader at LMS International, says none of the partners could have succeeded on their own.

“EUREKA allowed us to define and work towards a common goal of mutual interest,” says van der Auweraer. “The partnership combined complementary capabilities and know-how in structural modelling and laser holography. This combination of technologies was critical to the development of the solution; however neither party had both skills available. The synergy was therefore essential for the success of the project.”

“It is however also very relevant that the project combined end-user know-how and research direction. This ensured that the research and development efforts were focused on the real problems and not on academic topics.”