Prediction and measurement of structural intensity in thin plates excited by distributed random fluctuating pressure fields.

摘要

This work investigates active structural intensity (power flow) fields in plates excited by distributed, partially correlated pressure fields. The pressure fields considered come in the form of turbulent boundary layers and diffuse acoustic fields. Both excitation types occur in common engineering applications. Structural intensity fields can reveal areas where vibrational energy enters or exits a system. As such, these fields can indicate how energy from the exterior of a vehicle is transmitted to the interior, for example. Studies of structural intensity, to date, have typically focused on structures excited at a point or group of points, thus limiting their applicability. The current study is aimed at overcoming this limitation.; Three different methods of predicting structural intensity in a plate due to distributed, partially correlated excitation are designed and compared. The first two employ multiple-input/multiple-output system theory to predict a structural response matrix at a frequency. Finite differencing techniques are applied to the response matrix to compute a structural intensity field.; The third prediction scheme appears new to the literature. Therein, the intensity is computed directly, without an additional finite differencing step. This method may potentially be applied to non-ideal structures such as thick plates, solids, or built up structures. This presents an advantage over finite-differencing based prediction methods, which apply only to structures where internal stresses are directly related to surface velocities (i.e. thin plates, beams, etc.).; The three prediction methods are applied to a thin, simply-supported plate with an attached damper. Their results are compared and found to agree within expectation. An experiment is performed to test the prediction methods using a scanning laser Doppler vibrometer and finite differencing techniques. The measured and predicted fields are found to agree well. Lastly, case studies are performed with the prediction methods to yield insight into the phenomena that govern structural intensity fields' shapes and magnitudes.