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It is not very fun to ride a bicycle on a street plastered withcobblestones. At least the bike has a saddle seat filled withsilicone. That lessens the shocks and bumps, and counteracts someof the annoying vibrations. In a professional's eyes, the materialin the saddle is an "elastomer" -- a material that isyielding and malleable, like a rubber band. Engineers at theFraunhofer Institute for Structural Durability and SystemReliability LBF in Darmstadt are now working on the nextgeneration: They are designing components made of elastomers thatactively respond to unwanted vibrations, and dampen them moreeffectively than ever before. Elastomers have been used in engineering for decades, such as shockabsorbers in mechanical engineering or in the bearings for vehicleengines. Until now, they have had a purely passive effect onvibrations or impact collisions. It would be more effective if theelastomers were to respond proactively and counteract vibrations.In the same way a tennis player slows down the ball on a drop shotby pulling back on her racket, an active elastomer draws out theenergy from the vibration in a targeted manner by swinging inprecise push-pull mode. Theoretically, this would make thevibration dissipate completely. Elastomers vibrate under alternating current There are already materials that are good for this purpose."They are called 'electroactive elastomers'," explainsLBF scientist William Kaal. "They are elastic substances thatchange their form when exposed to an electrical field." Thetrick: apply an alternating current, and the material starts tovibrate. If there are smart electronics controlling the elastomers,making them vibrate precisely in push-pull mode, then unwantedvibrations in equipment or an engine will dissipate for the mostpart. To demonstrate that the principle works, the Darmstadt-basedresearchers created a model. Smaller than a pack of cigarettes, itis composed of 40 thin elastomer electrode layers. The experts callit a "stack actuator." "The challenge was the design of the electrodes with which weapply the electric field to the elastomer layers," as Kaal'scolleague Jan Hansmann clarifies. Usually, electrodes are made outof metal. However, metals are relatively rigid, which impedes thedeformation of the elastomer. Fraunhofer experts deliver an elegantsolution to the problem: "We put microscopic-sized holes inthe electrodes," says Hansmann. "If an electric voltagedeforms the elastomer, then the elastomer can disperse into theseholes." The result is an actuator that can rise or fall a fewtenths of a centimeter upon command -- several times a second, infact. To demonstrate these capabilities, William Kaal attaches asmall mechanical oscillator to the device. When he turns it on, theoscillator begins shaking powerfully -- the actuator has hit itsresonance frequency perfectly. On the other hand, the instrumentcan actively absorb vibrations: If the oscillator is tapped byhand, it quickly settles down when the actuator vibrates inpush-pull mode. The LBF engineers believe one potential application for their stackactuator can be found in vehicle construction. "An engine'svibrations can be really disruptive," says William Kaal."The vibrations are channeled through the chassis into thecar's interior, where the passengers start to feel them." Ofcourse, engines are installed meticulously, and yet: "Activeelastomers may help further reduce vibrations in the car,"Kaal asserts. When vibrations turn into power The function of the stack actuator can also be reversed: ratherthan produce vibrations, the device can also absorb vibrations fromits surroundings to produce energy. The principle works, andresearchers have proven it. As they placed an electromagneticoscillator on their stack actuator, it converted the vibrationsinto power. "That would be of interest, for example, if youwanted to monitor inaccessible sites where there are vibrations butno power connections," Jan Hansmann believes -- as he cites anexample: the temperature and vibration sensors that monitor bridgesfor their condition. The stack actuator technology has been largely perfected: "Themanufacturing process can be readily automated. That is importantfor industrial mass production," thinks Kaal. Nevertheless,endurance tests still have to show what the long-term viability ofthe intelligent actuators is like. Ultimately, they must be able towithstand harsh environments of the kind found in the enginecompartment of a car. We are high quality suppliers, our products such as Turbocharger Rotor Manufacturer , Turbocharger Diffuser for oversee buyer. To know more, please visits Shroud Ring.
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