Freely adjustable shock absorbers

Shock absorbers have their work cut out on bumpy roads. But whereas some drivers have a sportier driving style and are happy to accept harder damping for better cornering, others prefer greater comfort. Magnetorheological shock absorbers make damping infinitely adjustable. With this technology, a current-carrying coil in the shock absorber’s piston generates a magnetic field that causes a fluid to harden. The stronger the magnetic field, the more viscous the fluid becomes and the harder the damping. The system consumes around 20 watts for average damping. When power is cut, the damping reverts to its softest state.

Researchers at the Fraunhofer Institute for Silicate Research ISC in the German city of Würzburg have developed a shock absorber that offers a better safeguard against outages. A permanent magnet supplies a constant magnetic field for average damping – without using any electrical energy. Only when damping is to be increased or reduced is the coil activated to strengthen or weaken the magnetic field. Another new technology is based on a switchable magnet, where a short current pulse in the coil is sufficient to adjust the magnetization to requirements. This saves energy when damping has to be changed only rarely, such as when the vehicle’s load is altered.

Fraunhofer Institute for Silicate Research ISC
Neunerplatz 2 | 97082 Würzburg | www.isc.fraunhofer.de
Contact: Dr. Holger Böse | Phone +49 931 4100-203 | holger.boese@isc.fraunhofer.de
Press: Marie-Luise Righi | Phone +49 931 4100-150 | marie-luise.righi@isc.fraunhofer.de



Laser welding as driver of innovation

Can a laser weld with precision amid pounding machinery? The prototype of a new laser welding machine, developed within the EU’s Orbital project, has passed the acid test: it has demonstrated that it can operate reliably under tough everyday working conditions at the companies INTEGASA and ENSA, who manufacture heat exchangers for heavy industry in Spain. It is designed to replace the welding guns traditionally used in manufacturing to weld perforated tube sheets with thousands of tubes. This is a time-intensive process, and European manufacturers are finding it very difficult to cope with the competition from low-wage countries.

In future, lasers will do this job: baseplate and tube are welded together quickly and with pinpoint accuracy; a few seconds later, the robot arm, which transports the processing head, moves on to the next hole. “The prototype can even fuse materials that are considered difficult to weld,” says Patrick Herwig from the Fraunhofer Institute for Material and Beam Technology IWS in Dresden, which designed and tested the welding head within the EU project. Manufacturing heat exchangers, for example, calls for exotic material combinations. Heat exchangers are used in the chemical industry to draw heat away from hot, caustic solutions. Consequently, the tubes must be corrosion-resistant on the inside. On the other side, in the tank, there is a chemically neutral liquid that absorbs heat. Here it is possible to use low-cost materials. Where the tank and tubes meet, the different materials have to be joined. This pushes classical welding technology to its limits, whereas lasers manage the task with ease.

Fraunhofer Institute for Material and Beam Technology IWS
Winterbergstr. 28 | 01277 Dresden | www.iws.fraunhofer.de
Contact: Dipl.-Ing. Patrick Herwig | Phone +49 351 83391-3199 | patrick.herwig@iws.fraunhofer.de
Press: Dr. Ralf Jäckel | Phone +49 351 83391-3444 | ralf.jaeckel@iws.fraunhofer.de



Fuel cell generates power from methane

You can see the digesters at the Dresden sewage treatment plant from miles around. In them is thick brown sludge heated at around 38 degrees Celsius and used to obtain methane gas. This sewage gas powers a combined heat and power station. In this way, the sewage plant covers 60 percent of its own electricity needs. The power it produces would be sufficient to supply up to 16,000 households with electricity. However, it is possible to get even more from the gas. “Compared to a combined heat and power station, fuel cells are considerably more effective,” explains Matthias Jahn from the Dresden-based Fraunhofer Institute for Ceramic Technologies and Systems IKTS. Whereas conventional technology is able to achieve 40 percent efficiency at most, with the remainder lost as heat, fuel cells can reach an efficiency of 50 percent. “While cogeneration technology is largely exhausted, there is still scope for development with fuel cells,” says department head Jahn.

Jahn and his team are currently testing a solid oxide fuel cell (SOFC) under real conditions at the Dresden sewage works. The SOFC does not use hydrogen, which is energy-intensive to obtain, but rather sewage gas from municipal sewerage. “Our system remains stable in operation even when the methane content fluctuates between 30 and 70 percent,” explains Jahn. The carbon dioxide present in the biogas does not have to be separated out; it is used in the process. This allows greater flexibility in the composition of the fuel gas: food and market waste, leftovers from food production, and the contents of households’ organic waste bins can all go into the mix.

Fraunhofer Institute for Ceramic Technologies and Systems IKTS
Winterbergstr. 28 | 01277 Dresden | www.ikts.fraunhofer.de
Contact: Matthias Jahn | Phone +49 351 2553-7535 | matthias.jahn@ikts.fraunhofer.de
Press: Katrin Schwarz | Phone +49 351 2553-7720 | katrin.schwarz@ikts.fraunhofer.de