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 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
This paper investigates the nonlinear cross-modulation vibro-acoustic technique for fatigue crack detection in metallic
structures. The method is used in an aluminium plate instrumented with low-profile piezoceramic transducers that are
used for excitation. Laser vibrometry is used to acquire vibro-acoustic responses. The results demonstrate the modulation
transfer from one excitation signal to the other excitation signal in the presence of crack in the plate. The work
presented focuses on the analysis of modulation intensities. The paper demonstrates that the method can be used for
fatigue crack detection in metallic structures.
This 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.