23.03.2012
Smart materials strengthen flexible automation
Automation: Intelligent materials or smart materials can be switched, stretched or shortened by applying electric or magnetic fields - this opens up a wide range of application fields for automation and mechatronic engineers. Experts recently met at the Würzburg Fraunhofer Institute for Silicate Research (ISC) for an exchange of experience.
Once a magnetic field is applied to a magnetorheological fluid (MRF), this fluid substance becomes a semi-solid. The reason for this is the effect of the same name, in which microscopically small iron particles form within milliseconds to chains of magnetic dipoles and the liquid stiffens. "Here, shear stresses up to 100 kPa can be achieved," emphasizes Dieter Sporn, head of the Smart Materials Center at the Fraunhofer Institute for Silicate Research (ISC). The whole thing happens extremely fast, reversible and exactly reproducible. For such a MRF, there is no fixed composition, but it is composed as in a kit of different components. With Smart Materials, much simpler couplings for controllable force and torque transmissions, adaptive gripping tools, intelligent seals and metering valves can be developed in the future, according to ISC. "What you need is a tailor-made profile that can be used to tailor these smart materials to the task at hand," adds Sporn.
In the meantime, smart materials are also reflected in practice. Therefore, the members of the Cluster Mechatronics and Automation and the Automation Valley recently met at the ISC for an initial exchange of experience. The Fraunhofer researchers presented, among other exhibits, an encapsulated door lock for car doors based on Smart Materials, which adapts its holding power to the respective requirements. Even if the vehicle electrical system fails, the functional safety is guaranteed.
Another group of smart materials includes materials that can be used to transfer forces. Here, electrical signals are converted into mechanical motion or vice versa. "When an electric field is applied to an electroactive polymer between the electrodes, the dielectric elastomer actuator (DEA) expands rapidly and with a high energy density," explains the ISC scientist. So it is possible to build a precise linear motor, which manages without rare earths. Similar materials can be used to build a self-sufficient energy supply that generates electricity from the vibrations of machines, systems or other components.
"If one uses further properties of these materials, highly flexible capacitive sensors are developed to monitor forces, pressures and deformations", continues Dieter Sporn. Here, too, a wide field of application opens up for automation technology. However, there is still insufficient experience regarding the reliability, robustness and lifetime of the smart materials. Sporn: "But it only seems to be a matter of time until appropriate methods and tools are developed here as well."
Source: VDI news, Würzburg, 23. 3. 12, kip ROLAND HENSEL
