Carbon – a dynamic material
Vibrations will usually occur when various parts of a machine are in motion. In most cases, vibrations are not wanted, as they reduce process dynamics and precision, while increasing the wear on individual components. Reducing or even eliminating machine vibrations is a very complex design task which is rewarded with highly increased efficiency and production quality. With machine components made of fiber composites, there are several technically interesting measures at hand to minimize unwanted machine vibrations.
By using fiber composites as design material, we can manipulate the damping ratio or the natural frequency; a targeted pole shift can render vibrations and excitations harmless. Thanks to specific material properties, fiber composites inherently boast high damping ratios which can be further increased with the help of optimized composite layering.By con-verting vibrational energy into inner warmth, we can reduce the amplitude and accelerate the subsidence of induced vibrations. Mea-sured as logarithmic decrement, these ratios have up to twenty times the values for steel which means that machine components can be adjusted to the perfect damping ratio for the required application. This allows a more abrupt positioning of components in highly dynamic applications or a better measuring signal quality.
Thanks to the many design characteristics of fiber compos-ites, it is also possible to adjust the natural frequency of a machine component to perfectly match the requirements of an application. By varying the component rigidity, the frequency can be moved into a range where the component can no longer be excited by its surroundings. In contrast, the natural frequency of machine components made of metals are permanently defined by their geometry. Here too, fiber composites allow for intelligent solutions and products that overcome the restrictions of conventional materials.
An overall low vibration level is achieved through a combination of characteristic material properties that include low amount of excitable component mass, a high degree of damping as well as high, in some cases "adjustable" natural frequency spectrums. As an example, the imbalance of shafts or rollers made of CFRP is very low.As a consequence, if the vibration displace-ment is the same as it would be for metal components, much higher production speeds can be achieved or, if the dynamics are the same, more smoothness can be achieved which in turn allows for things such as more precise measurement results or better pro-duction results.
Low- and high-frequency vibrations in machines can be further reduced by using tuned mass dampers or vibration absorbers. The design of tuned mass dampers is based on a spring mass system that counter-acts unwanted vibrations and thus suppresses them. To do so, the mass of the tuned mass dampers and the mass of the system that needs to be protected against vibration need to correspond to one another. If additional damping elements are used, these are referred to as vibration absorbers. We have developed adjustable tuned mass dampers that make it possible to move the location of the damping point without time-consuming calculations, so as to counter unwanted vibration or to stay away from problems caused by natural frequencies without much fuss.
With the help of actuators that induce artificial counter vibrations with controlled phase and amplitude, structure-borne interference noises can be created that cancel out the vibrations. We offer these more sophisticated solutions in cooperation with experienced specialists from our network. To us, adaptronic technology and composites are partners that create great solutions for higher complex problems.