Abstract:

Power released in or transferred to a structure will cause noise radiation, fatigue, or mechanical malfunction in the structure or parts connected to the structure. Nonlinear behavior is of great significance to the integrity of any structure and is therefore of fundamental interest. An ideal machine would produce no vibration at all because all energy would be channeled into the job to be done. In practice, vibration occurs as a by-product of the normal transmission of cyclic forces through the mechanism. Machine elements react against each other and energy is dissipated through the structure in the form of vibration and acoustic noise. If the surface area is large compared to an acoustic wavelength, acoustic intensity is a good indicator of dynamic activity. If the area is small compared to a wavelength at the frequencies in question, surface measurements using the vibratory motion on the structure's surface will be a good indicator. If the energy transfer takes place between two separate structures coupled at points, the point power measurement method should be applied. Two accelerometers, accelerometer and force gauge, two microphones, multi microphone arrays or laser techniques may be used for transduction. Signal processing and interpretation will be discussed.