The paper discusses the use of wideband excitation in nonlinear vibro-acoustic modulation technique (VAM) used for damage detection. In its original form, two mono-harmonic signals (low and high frequency) are used for excitation. The low frequency excitation is typically selected based on a modal analysis test and high frequency excitation is selected arbitrarily in the ultrasonic frequency range. This paper presents a different approach with use of wideband excitation signals. The proposed approach gives the possibility to simplify the testing procedure by omitting the modal test used to determine the value of low frequency excitation. Simultaneous use of wideband excitation for high frequency solves the ambiguity related to the selection of the frequency of acoustic wave. Broadband excitation signals require, however, more elaborate signal processing methods to determine the intensity of modulation for a given bandwidth. The paper discusses the proposed approach and the related signal processing procedure. Experimental validation of the proposed technique is performed on a laminated composite plate with a barely visible impact damage that was generated in an impact test. Piezoceramic actuators are used for vibration excitation and a scanning laser vibrometer is used for noncontact data acquisition.
We present an overview of research developments related to the nonlinear vibroacoustic modulation technique used for structural damage detection. The method of interest is based on nonlinear interactions of a low-frequency pumping wave and a high-frequency probing wave. These two waves are introduced to monitored structures simultaneously. Then the presence of damage is exhibited by additional frequency components that result from nonlinear damage-wave interactions. A vast amount of research has been performed in this area over the last two decades. We aim to present the state-of-the-art of these developments. The major focus is on monitoring approaches, modeling aspects, actuation/sensing, signal processing, and application examples.
The paper presents a novel damage detection method that combines Lamb wave propagation with nonlinear acoustics.
Low-frequency excitation is used to modulate Lamb waves in the presence of fatigue cracks. The work presented shows
that the synchronization of the interrogating high-frequency Lamb wave with the low-frequency vibration is a key
element of the proposed method. The main advantages of the proposed method are the lack of necessity for baseline
measurements representing undamaged condition and lack of sensitivity to temperature variations. Numerical
simulations and experimental measurements are performed to demonstrate the application of the proposed method to
detect fatigue crack in aluminum beam.
The paper deals with the problem of Lamb waves dispersion curves sensitivity to the change of elastic constants
in composite materials. The framework of the present work is a more general problem of material constants
identification in thin plates made of composite materials. The approach is based on the analysis of guided waves
propagation and the related dispersion curves to find the underlying material elastic constants. In present work a
numerical study is performed to identify measurement directions and wave propagation modes that are most sensitive to
the change of the particular elastic constants. This approach will allow to optimize the material constants identification
procedure and experimental setup by specifying the preferred measurement directions and wave propagation modes. The
approach can be used within the Structural Health Monitoring framework to monitor material degradation of plate-like
structures made of composite materials.
The paper deals with the nonlinear vibro-acoustic modulation technique (VAM) used for nondestructive damage
detection in composites. In its original form the technique allows only for the determination of the presence of damage in
a structure. This paper presents an enhancement of the technique that allows also for the determination of damage
location. Experimental testing of the proposed procedure is performed on carbon fiber/epoxy laminated composite plates
with barely visible impact damage that was generated in an impact test. Shearography was used to verify damage
location. Piezoceramic actuators are used for vibration excitation and a scanning laser vibrometer is used for data