Structural intensity based damage detection assessments of aluminum panel structures

The use of a scanning Laser Doppler Vibrometer (LDV) for measuring a panel's surface response velocity or Operating Deflection Shape (ODS) has become a common non-contact engineering measurement technique. Previous research at Penn State University by Daley (2005) used scanning LDV measurements and a finite differencing post processing scheme to estimate the Structural Intensity (SI) and power flow of thin plates under diffuse acoustic excitation. In the finite difference formulation the surface velocities were used along with spatial derivative approximations to the (thin) plate moments and shears to estimate the structural intensity shear, bending and twisting components. In this research, aluminum plate structures with progressively increasing levels of damage were studied using scanning LDV measurements and a finite differencing formulation to compute structural intensities. Several healthy and damaged plate structures were tested using point vibration sources and dissipative sinks. The structure (vibration) sources and sinks were identified using the computed SI fields. The progressively increasing damage was identified in terms of how the damage was manifested in changes to the SI field (magnitudes and directions). Implementations of general SI based structural damage detection techniques are also discussed.