March 24, 2006 Just how far can you push weight reducation in a design before it breaks? What happens to a product after it leaves the factory? What stresses are placed on a mountain bike if the owner tackles a long set of concrete steps or a steep downhill slope or some steps on it? What is the magnitude and frequency of forces acting on the blade of a wind turbine? Computer simulation is one thing, but there’s no substitute for actually monitoring the loads a product will experience in usage, and German researchers have developed a new sensor system that does just that.

"In the age of lightweight construction it is particularly important for manufacturers to know just how far they can push product design", explains Stefan Weiland from the Fraunhofer Institute for Structural Durability and System Reliability LBF. If you buy a motorbike, then lower weight translates into lower fuel consumption but in return the motorbike must not be any less safe than its heavier stable mate. Consequently it is important to know exactly which components can be used to save weight and where safety has already been pushed to the limit.

But how do you find out? The Darmstadt-based researchers are using a monitoring system to measure for example forces during operation. "At the bike we measure the acceleration and the forces, and record these values on a memory chip", reports Stefan Weiland who will be presenting the bike at the Hannover Messe.

The engineers from the LBF provide the bike fitted with sensors to test cyclists who then, for instance, cross the Alps on it. Back in Darmstadt the measurement signals are fed into a database and analyzed: how often did the cyclist have to make an emergency stop and what forces acted on the components as a result? The manufacturer also learns what terrain the cyclist encountered and how many jumps were involved.

Monitoring technology is not only useful for the cycle industry. Sensors can measure voltages in wind turbines: this data is compared online with preset parameters. If the maximum value is exceeded, the system automatically switches off. Monitoring costly machinery has also proven effective: a brown coal excavator due to be decommissioned after 20 years turned out to be up to the job nonetheless still providing reliable service to this day.