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Applications Note 1-10:Structural or Solid Damping:It has been established that cyclically-stressed materials dissipate energywithin the material itself. This is the reason that the response of a cantileverbeam accelerometer or piezoelectric accelerometer is not infinite at the resonancefrequency due to the internal damping of the beam material itself.It has also been found that most structural materials such as steel and aluminumwill dissipate energy per stress cycle that is predominantly independentof frequency and is proportional to the square of the amplitude ofvibration. With the energy dissipated per cycle proportional to the square ofthe vibration amplitude, the loss coefficient is constant and the shape of thehysteresis curve remains independent of amplitude and strain rate. In concertwith the intrinsic structural damping afforded by the materials thatcomprise the sensor structure, external or extrinsic materials can be used tofurther aid in the structural damping of the sensor.FIGURE 1-35. Structural-Damping Model:AccelerationAccelerometerFoundationDamping MaterialKRFoundationSolid materials used for structural damping are generally mounted underthe accelerometer structure as shown in Figure 1-35 and therefore presentan additional spring and damper suspension which must be considered inthe determination of the total transfer function of the accelerometer. Soliddamping is not generally useful at low frequencies but can be of use in theexplosives and ordinance testing fields to mitigate the high-frequency componentsthat are induced in explosively-driven structures such as armorplating. It should be realized that structural damping is a form of frequencyThe Art of Practical and Precise Strain Based Measurement 2nd Edition © 1999 CHAPTER 1-65