1,256 research outputs found
Impact Damage Detection in Composite Laminates Using Nonlinear Acoustics
No full textThe paper demonstrates the application of nonlinear acoustics for impact damage detection in composite laminates. A composite plate is monitored for damage resulting from a low-velocity impact. The plate is instrumented with bonded low-profile piezoceramic transducers. A high-frequency acoustic wave is introduced to one transducer and picked up by a different transducer. A low-frequency flexural modal excitation is introduced to the plate at the same time using an electromagnetic shaker. The damage induced by impact is exhibited in a power spectrum of the acoustic response by a pattern of sidebands around the main acoustic harmonic. The results show that the amplitude of sidebands is related to the severity of damage. The study investigates also the effect of boundary conditions on the results
Effect of boundary conditions on nonlinear acoustics used for impact damage detection in composite structures
No full textNonlinear Acoustics uses different types of nonlinear phenomena to detect structural damage. One of the major difficulties associated with this technique is the fact that nonlinearities can be produced not only by damage but also by various intrinsic effects such as material behaviour and/or structural boundary conditions. The paper investigates the effect of boundary conditions on Nonlinear Acoustics used for damage detection. A simple composite plate with impact damage is investigated. The plate is clamped using various force levels. The experimental study focuses on the effect of clamping force on vibro-acoustic interaction. The results demonstrate the importance of the effect of boundary conditions when nonlinear acoustics is used for impact damage detection
Sensor Location Analysis for Nonlinear Acoustics Based Damage Detection in Composite Structures
No full textThis paper investigates the piezo-based nonlinear vibro-acoustic modulation technique for impact damage detection in composite structures. The method is based on combined low-frequency modal excitation and high-frequency ultrasonic excitation that lead to vibro-acoustic modulations in damaged specimens. The work presented focuses on sensor location analysis. Low-profile, surface bonded piezoceramic transducers are used for ultrasonic and modal excitation.. Modulated responses are acquired using laser vibrometry. Various areas of monitored composite structures are investigated to establish positions exhibiting the largest intensities of vibro-acoustic modulations resulting from impact damage. The study shows that sensor location in composite structures is important for efficient damage detection
Investigation of low-frequency excitation amplitude on the effectiveness of nonlinear vibro-acoustic method used for damage detection
No full textIdentificazione del danno da impatto in laminati compositi con tecniche di acustica nonlineare
No full textAnalysis of Vibro-Acoustic Modulations in Nonlinear Acoustics Used for Impact Damage Detection – numerical and experimental study
No full textAnalysis of Nonlinear Vibro-Acoustic Wave Modulations Used for Impact Damage Detection in Composite Structures
No full textImpact damage detection in smart composites using nonlinear acoustics - Cointegration analysis for removal of undesired load effect
No full textThe paper presents a reliable methodology - based on nonlinear acoustics - for impact damage detection in composite materials. The nonlinear vibro-acoustic wave modulation technique is used to detect damage. The problem of operational variability of the method with respect to the selection of frequency and amplitude of low-frequency (LF) modal excitation is investigated. This problem is addressed using the concept of stationarity of time series of vibro-acoustic data. Cointegration analysis is employed to compensate for the effect of variable operational conditions associated with LF modal (or vibration) excitation in nonlinear vibro-acoustic wave modulations. Analysis of stationary statistical characteristics of vibro-acoustic responses - after cointegration analysis - are used for damage detection. The proposed method is validated using vibro-acoustic data from laminated composite plates and composite sandwich panels. The results demonstrate that the proposed approach can effectively compensate for the effect of LF modal excitation on nonlinear vibro-acoustic wave modulations and detect the damage more accurately and robustly than the existing nonlinear acoustics based on the analysis of modulation sidebands
Impact damage detection in laminated composites by non-linear vibro-acoustic wave modulations
No full textThe paper presents an application of nonlinear acoustics for impact damage detection in composite laminates. Two composite plates were analysed. A low-velocity impact was used to damage one of the plates. Ultrasonic C-scan was applied to reveal the extent of barely visible impact damage. Finite element modelling was used to find vibration mode shapes of the plates and to estimate the local defect resonance frequency in the damaged plate. A delamination divergence study was performed to establish excitation parameters for nonlinear acoustics tests used for damage detection. Both composite plates were instrumented with surface-bonded, low-profile piezoceramic transducers that were used for the high frequency ultrasonic excitation. Both an arbitrary frequency and a frequency corresponding to the local defect resonance were investigated. The low-frequency modal excitation was applied using an electromagnetic shaker. Scanning laser vibrometry was applied to acquire the vibro-acoustic responses from the plates. The study not only demonstrates that nonlinear vibro-acoustic modulations can successfully reveal the barely visible impact damage in composite plates, but also that the entire procedure can be enhanced when the ultrasonic excitation frequency corresponds to the resonant frequency of damag
- …
