[Show abstract][Hide abstract] ABSTRACT: This paper is primarily focused on the identification of structural forces, with the objective of localizing forces injected into structures in the mid-high frequency range. An energy method, called the simplified energy method (MES), has already been introduced for the purpose of predicting an energy density distribution for structural acoustic problems in the mid-high frequency range. The present paper proposes using this same energy method to solve inverse structural problems. More specifically, the injected forces are to be estimated and localized through knowledge of a set of energy densities within the structure. The 2D formulation of this inverse approach, known as inverse MES (or IMES), is first expressed. Both the boundary and internal sources can then be detected by applying the proposed formulation. Numerical test results are processed using a 2D Kirchhoff plate, and a number of conclusions are also drawn regarding IMES capabilities. Moreover, this paper offers a numerical comparison with another energy-based method.
Mechanical Systems and Signal Processing 01/2011; 25(8):2948-2961. · 1.91 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Nonlinear structural intensity (NSI) and nonlinear structural surface intensity (NSSI) based damage detection techniques were improved and extended to metal and composite airframe structures. In this study, the measurement of NSI maps at sub-harmonic frequencies was completed to provide enhanced understanding of the energy flow characteristics associated with the damage induced contact acoustic nonlinearity mechanism. Important results include NSI source localization visualization at ultra-subharmonic (nf/2) frequencies, and damage detection results utilizing structural surface intensity in the nonlinear domain. A detection metric relying on modulated wave spectroscopy was developed and implemented using the NSSI feature. The data fusion of the intensity formulation provided a distinct advantage, as both the single interrogation frequency NSSI and its modulated wave extension (NSSI-MW) exhibited considerably higher sensitivities to damage than using single-sensor (strain or acceleration) nonlinear detection metrics. The active intensity based techniques were also extended to composite materials, and results show both NSSI and NSSI-MW can be used to detect damage in the bond line of an integrally stiffened composite plate structure with high sensitivity. Initial damage detection measurements made on an OH-58 tailboom (Penn State Applied Research Laboratory, State College, PA) indicate the techniques can be transitioned to complex airframe structures achieving high detection sensitivities with minimal sensors and actuators.
The Journal of the Acoustical Society of America 01/2013; 133(1):186-200. · 1.65 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Abstract Closing delaminations in composite laminated structures exhibit a nonlinear
dynamic response when excited by high frequency elastic waves. The contact acoustic
nonlinear effects taking place at the damage interface act as a mechanism of energy
redistribution from the driving frequency to the nonlinear harmonic frequencies. In this paper,
we extend the concept of nonlinear structural intensity (NSI) to the analysis of closing
delaminations in composite laminated plates. NSI is calculated using a method based on ...
Smart Materials and Structures 12/2013; 22(12). · 2.02 Impact Factor
Data provided are for informational purposes only. Although carefully collected, accuracy cannot be guaranteed. The impact factor represents a rough estimation of the journal's impact factor and does not reflect the actual current impact factor. Publisher conditions are provided by RoMEO. Differing provisions from the publisher's actual policy or licence agreement may be applicable.