TABLE OF CONTENTS We've already seen how altering the mass, spring, and damping properties of an SDOF system will alter its response. This section will discuss an interesting twist in which we control the response of a sinusoidally forced mass by adding more spring and mass elements to the system. We won't need to add damping, and we won't be dissipating more energy to control the response. Instead, we'll distribute the vibrational energy, moving it from the original mass to the new one.
Devices that absorb energy in this way are found in a variety of applications. One common use is to reduce the vibrational response of high tension power lines. Figure 4.10a shows a photo of a typical powerline with attached vibrational absorbers, known as Stockbridge dampers. Figure 4.10b shows a close-up of the device, and Figure 4.10c shows a simplified diagram of the total powerline/vibration absorber system. Keep in mind that, as already mentioned, there is no energy dissipation taking place, in spite of the name. All that is happening is that energy which was vibrating the cable, will now vibrate the Stockbridge damper.
A simplified picture of a vibration absorber application is shown in Figures 4.11. Figure 4.11a indicates the original system, in which a spring-mass combination ( m 1 and k 1) is acted upon...
