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http://hdl.handle.net/10985/22709
Real-time sinusoidal parameter estimation for damage growth monitoring during ultrasonic very high cycle fatigue tests
KISER, Shawn L.; RÉBILLAT, Marc; GUSKOV, Mikhail; RANC, Nicolas
Ultrasonic fatigue tests (UFT) are used to study the fatigue life behavior of metallic components undergoing a very high number of cycles (typically ≥ 107 − 109 cycles) under relatively low mechanical loads. By soliciting fatigue specimens at 20 kHz, ultrasonic fatigue machines are indispensable for monitoring damage growth and fatigue failures in a reasonable amount of time. As fatigue damage accumulates in the specimen, the specimen’s free-end exhibits a nonlinear dynamic response. The resulting quasi-stationary, harmonic signals have sinusoidal parameters (frequency and amplitude) which are slowly time-varying with respect to the excita-tion frequency. The discrete Fourier transform (DFT) is typically used to extract these evolving sinusoidal parameters from a window of finite data of the vibration signal. Alternative spectral estimation methods, specifically line spectra estimators (LSEs), exploit a priori information of the signal via their modeling basis and overcome limitations seen by the DFT. Many LSEs are known to have state-of-the-art results when benchmarked on purely stationary signals with unit amplitudes. However, their performances are unknown in the context of slowly time-varying signals typical of UFT, leading to a widespread use of the DFT. Thus, this paper benchmarks classical and modern LSEs against specific synthetic signals which arise in UFTs. Adequate algorithms are then recommended and made publicly available to process experimental data coming from ultrasonic fatigue tests depending on performance metrics and experimental restraints.
Fri, 01 Jul 2022 00:00:00 GMThttp://hdl.handle.net/10985/227092022-07-01T00:00:00ZKISER, Shawn L.RÉBILLAT, MarcGUSKOV, MikhailRANC, NicolasUltrasonic fatigue tests (UFT) are used to study the fatigue life behavior of metallic components undergoing a very high number of cycles (typically ≥ 107 − 109 cycles) under relatively low mechanical loads. By soliciting fatigue specimens at 20 kHz, ultrasonic fatigue machines are indispensable for monitoring damage growth and fatigue failures in a reasonable amount of time. As fatigue damage accumulates in the specimen, the specimen’s free-end exhibits a nonlinear dynamic response. The resulting quasi-stationary, harmonic signals have sinusoidal parameters (frequency and amplitude) which are slowly time-varying with respect to the excita-tion frequency. The discrete Fourier transform (DFT) is typically used to extract these evolving sinusoidal parameters from a window of finite data of the vibration signal. Alternative spectral estimation methods, specifically line spectra estimators (LSEs), exploit a priori information of the signal via their modeling basis and overcome limitations seen by the DFT. Many LSEs are known to have state-of-the-art results when benchmarked on purely stationary signals with unit amplitudes. However, their performances are unknown in the context of slowly time-varying signals typical of UFT, leading to a widespread use of the DFT. Thus, this paper benchmarks classical and modern LSEs against specific synthetic signals which arise in UFTs. Adequate algorithms are then recommended and made publicly available to process experimental data coming from ultrasonic fatigue tests depending on performance metrics and experimental restraints.Prediction of frequency and spatially dependent attenuation of guided waves propagating in mounted and unmounted A380 parts made up of anisotropic viscoelastic composite laminates
http://hdl.handle.net/10985/22016
Prediction of frequency and spatially dependent attenuation of guided waves propagating in mounted and unmounted A380 parts made up of anisotropic viscoelastic composite laminates
GUO, Shuanglin; RÉBILLAT, Marc; MECHBAL, Nazih
Monitoring damage in composite structures using guided wave-based techniques is particularly effective due to their excellent ability to propagate over relatively long distance and hence to cover a large area with few testing time and equipment. The industrialization of this method is highly tributary of the number and placement of the active elements. Yet, the optimal sensorization of a structure relies on the decrease in amplitude of guided waves over propagation distance. A reliable prediction of attenuation of guided waves is still a challenge especially for anisotropic viscoelastic composite materials which exhibit complex changes of attenuation with propagation direction and thus a spatial dependency of attenuation. In this paper, the damped global matrix method (dGMM), having stable and efficient merits, is developed to predict the frequency and spatially dependent attenuation of waves propagating in anisotropic composite materials. dGMM integrates three damping models (Hysteretic, Kelvin-Voigt, and Biot models) into the conventional undamped GMM to consider viscoelasticity of composite laminates. The proposed dGMM is first theoretically validated by numerical comparison with the semi-analytical finite element method. In addition, two industrial case studies, parts of an A380 nacelle at scale one, are employed to experimentally validate the proposed attenuation prediction method. The first one is a fan cowl structure and the second one is an inner fixed structure, both either unmounted or mounted on an actual instrumented A380 plane. This makes the validation extremely valuable for both the scientific and industrial communities. The proposed attenuation prediction method thus paves the way to optimally deploy sensor network for structural health monitoring of anisotropic viscoelastic composite structures.
Sun, 01 May 2022 00:00:00 GMThttp://hdl.handle.net/10985/220162022-05-01T00:00:00ZGUO, ShuanglinRÉBILLAT, MarcMECHBAL, NazihMonitoring damage in composite structures using guided wave-based techniques is particularly effective due to their excellent ability to propagate over relatively long distance and hence to cover a large area with few testing time and equipment. The industrialization of this method is highly tributary of the number and placement of the active elements. Yet, the optimal sensorization of a structure relies on the decrease in amplitude of guided waves over propagation distance. A reliable prediction of attenuation of guided waves is still a challenge especially for anisotropic viscoelastic composite materials which exhibit complex changes of attenuation with propagation direction and thus a spatial dependency of attenuation. In this paper, the damped global matrix method (dGMM), having stable and efficient merits, is developed to predict the frequency and spatially dependent attenuation of waves propagating in anisotropic composite materials. dGMM integrates three damping models (Hysteretic, Kelvin-Voigt, and Biot models) into the conventional undamped GMM to consider viscoelasticity of composite laminates. The proposed dGMM is first theoretically validated by numerical comparison with the semi-analytical finite element method. In addition, two industrial case studies, parts of an A380 nacelle at scale one, are employed to experimentally validate the proposed attenuation prediction method. The first one is a fan cowl structure and the second one is an inner fixed structure, both either unmounted or mounted on an actual instrumented A380 plane. This makes the validation extremely valuable for both the scientific and industrial communities. The proposed attenuation prediction method thus paves the way to optimally deploy sensor network for structural health monitoring of anisotropic viscoelastic composite structures.On the variation of interaural time differences with frequency
http://hdl.handle.net/10985/10702
On the variation of interaural time differences with frequency
BENICHOUX, Victor; BRETTE, Romain; RÉBILLAT, Marc
Interaural time difference (ITD) is a major cue to sound localization in humans and animals. For a given subject and position in space, ITD depends on frequency. This variation is analyzed here using a head related transfer functions (HRTFs) database collected from the literature and comprising human HRTFs from 130 subjects and animal HRTFs from six specimens of different species. For humans, the ITD is found to vary with frequency in a way that shows consistent differences with respect to a spherical head model. Maximal ITD values were found to be about 800 ls in low frequencies and 600 ls in high frequencies. The ITD variation with frequency (up to 200 ls for some positions) occurs within the frequency range where ITD is used to judge the lateral position of a sound source. In addition, ITD varies substantially within the bandwidth of a single auditory filter, leading to systematic differences between envelope and fine-structure ITDs. Because the frequency-dependent pattern of ITD does not display spherical symmetries, it potentially provides cues to elevation and resolves front/back confusion. The fact that the relation between position and ITDs strongly depends on the sound’s spectrum in turn suggests that humans and animals make use of this relationship for the localization of sounds.
Fri, 01 Jan 2016 00:00:00 GMThttp://hdl.handle.net/10985/107022016-01-01T00:00:00ZBENICHOUX, VictorBRETTE, RomainRÉBILLAT, MarcInteraural time difference (ITD) is a major cue to sound localization in humans and animals. For a given subject and position in space, ITD depends on frequency. This variation is analyzed here using a head related transfer functions (HRTFs) database collected from the literature and comprising human HRTFs from 130 subjects and animal HRTFs from six specimens of different species. For humans, the ITD is found to vary with frequency in a way that shows consistent differences with respect to a spherical head model. Maximal ITD values were found to be about 800 ls in low frequencies and 600 ls in high frequencies. The ITD variation with frequency (up to 200 ls for some positions) occurs within the frequency range where ITD is used to judge the lateral position of a sound source. In addition, ITD varies substantially within the bandwidth of a single auditory filter, leading to systematic differences between envelope and fine-structure ITDs. Because the frequency-dependent pattern of ITD does not display spherical symmetries, it potentially provides cues to elevation and resolves front/back confusion. The fact that the relation between position and ITDs strongly depends on the sound’s spectrum in turn suggests that humans and animals make use of this relationship for the localization of sounds.Vibroacoustics of the piano soundboard : (Non)linearity and modal properties in the low- and mid-frequency ranges
http://hdl.handle.net/10985/8195
Vibroacoustics of the piano soundboard : (Non)linearity and modal properties in the low- and mid-frequency ranges
EGE, Kerem; BOUTILLON, Xavier; RÉBILLAT, Marc
The piano soundboard transforms the string vibration into sound and therefore, its vibrations are of primary importance for the sound characteristics of the instrument. An original vibro-acoustical method is presented to isolate the soundboard nonlinearity from that of the exciting device (here: a loudspeaker) and to measure it. The nonlinear part of the soundboard response to an external excitation is quantitatively estimated for the ﬁrst time, at 40 dB below the linear part at the ff nuance. Given this essentially linear response, a modal identiﬁcation is performed up to 3 kHz by means of a novel high resolution modal analysis technique [K. Ege, X. Boutillon, B. David, High-resolution modal analysis, Journal of Sound and Vibration 325 (4–5) (2009) 852–869]. Modal dampings (which, so far, were unknown for the piano in this frequency range) are determined in the mid-frequency domain where FFT-based methods fail to evaluate them with an acceptable precision. They turn out to be close to those imposed by wood. A ﬁnite-element modelling of the soundboard is also presented. The low-order modal shapes and the comparison between the corresponding experimental and numerical modal frequencies suggest that the boundary conditions can be considered as blocked, except at very low frequencies. The frequency-dependency of the estimated modal densities and the observation of modal shapes reveal two well-separated regimes. Below 1 kHz, the soundboard vibrates more or less like a homogeneous plate. Above that limit, the structural waves are conﬁned by ribs, as already noticed by several authors, and localised in restricted areas (one or a few inter-rib spaces), presumably due to a slightly irregular spacing of the ribs across the soundboard.
Tue, 01 Jan 2013 00:00:00 GMThttp://hdl.handle.net/10985/81952013-01-01T00:00:00ZEGE, KeremBOUTILLON, XavierRÉBILLAT, MarcThe piano soundboard transforms the string vibration into sound and therefore, its vibrations are of primary importance for the sound characteristics of the instrument. An original vibro-acoustical method is presented to isolate the soundboard nonlinearity from that of the exciting device (here: a loudspeaker) and to measure it. The nonlinear part of the soundboard response to an external excitation is quantitatively estimated for the ﬁrst time, at 40 dB below the linear part at the ff nuance. Given this essentially linear response, a modal identiﬁcation is performed up to 3 kHz by means of a novel high resolution modal analysis technique [K. Ege, X. Boutillon, B. David, High-resolution modal analysis, Journal of Sound and Vibration 325 (4–5) (2009) 852–869]. Modal dampings (which, so far, were unknown for the piano in this frequency range) are determined in the mid-frequency domain where FFT-based methods fail to evaluate them with an acceptable precision. They turn out to be close to those imposed by wood. A ﬁnite-element modelling of the soundboard is also presented. The low-order modal shapes and the comparison between the corresponding experimental and numerical modal frequencies suggest that the boundary conditions can be considered as blocked, except at very low frequencies. The frequency-dependency of the estimated modal densities and the observation of modal shapes reveal two well-separated regimes. Below 1 kHz, the soundboard vibrates more or less like a homogeneous plate. Above that limit, the structural waves are conﬁned by ribs, as already noticed by several authors, and localised in restricted areas (one or a few inter-rib spaces), presumably due to a slightly irregular spacing of the ribs across the soundboard.PIEZOELECTRIC TRANSDUCER FOR LOW FREQUENCY SOUND GENERATION ON SURFACE LOUDSPEAKERS
http://hdl.handle.net/10985/19536
PIEZOELECTRIC TRANSDUCER FOR LOW FREQUENCY SOUND GENERATION ON SURFACE LOUDSPEAKERS
BOLZMACHER, Christian; BENBARA, Nassim; MECHBAL, Nazih; RÉBILLAT, Marc
This paper describes the comparison of three different types of piezoelectric actuators for application in sound emitting panels so-called load-bearing surface loudspeaker. The first actuator is a piezoelectric ring glued directly to a polypropylene surface of dimension 300 x 200 x 3 mm3. The other two are mechanically amplified piezoelectric actuators of the flat and the cymbal flextensional-type tested in a reactive configuration on the same sized polypropylene panel. Those actuators are compared in terms of vibration response measured with a laser vibrometer and audio response measured with a microphone.
Tue, 01 Jan 2019 00:00:00 GMThttp://hdl.handle.net/10985/195362019-01-01T00:00:00ZBOLZMACHER, ChristianBENBARA, NassimMECHBAL, NazihRÉBILLAT, MarcThis paper describes the comparison of three different types of piezoelectric actuators for application in sound emitting panels so-called load-bearing surface loudspeaker. The first actuator is a piezoelectric ring glued directly to a polypropylene surface of dimension 300 x 200 x 3 mm3. The other two are mechanically amplified piezoelectric actuators of the flat and the cymbal flextensional-type tested in a reactive configuration on the same sized polypropylene panel. Those actuators are compared in terms of vibration response measured with a laser vibrometer and audio response measured with a microphone.Repeated exponential sine sweeps for the autonomous estimation of nonlinearities and bootstrap assessment of uncertainties
http://hdl.handle.net/10985/10522
Repeated exponential sine sweeps for the autonomous estimation of nonlinearities and bootstrap assessment of uncertainties
EGE, Kerem; GALLO, Maxime; ANTONI, Jérôme; RÉBILLAT, Marc
Measurements on vibrating structures has been a topic of interest for decades. Vibrating structures are however generally assumed to behave linearly and in a noise-free environment, which is not the case in practice. This paper provides a methodology that allows for the autonomous estimation of nonlinearities and assessment of uncertainties by bootstrap on a given vibrating structure. Nonlinearities are estimated by means of a block-oriented nonlinear model approach based on parallel Hammerstein models and on exponential sine sweeps. Estimation uncertainties are simultaneously assessed using repetitions of the input signal (multi-sine sweeps) as the input of a bootstrap procedure. Mathematical foundations and a practical implementation of the method are discussed using an experimental example. The experiment chosen here consists in exciting a steel plate under various boundary conditions with exponential sine sweeps and at different levels in order to assess the evolution of nonlinearities and uncertainties over a wide range of frequencies and input amplitudes.
Thu, 01 Jan 2015 00:00:00 GMThttp://hdl.handle.net/10985/105222015-01-01T00:00:00ZEGE, KeremGALLO, MaximeANTONI, JérômeRÉBILLAT, MarcMeasurements on vibrating structures has been a topic of interest for decades. Vibrating structures are however generally assumed to behave linearly and in a noise-free environment, which is not the case in practice. This paper provides a methodology that allows for the autonomous estimation of nonlinearities and assessment of uncertainties by bootstrap on a given vibrating structure. Nonlinearities are estimated by means of a block-oriented nonlinear model approach based on parallel Hammerstein models and on exponential sine sweeps. Estimation uncertainties are simultaneously assessed using repetitions of the input signal (multi-sine sweeps) as the input of a bootstrap procedure. Mathematical foundations and a practical implementation of the method are discussed using an experimental example. The experiment chosen here consists in exciting a steel plate under various boundary conditions with exponential sine sweeps and at different levels in order to assess the evolution of nonlinearities and uncertainties over a wide range of frequencies and input amplitudes.Sensorless Nonlinear Stroke Controller for an Implantable, Undulating Membrane Blood Pump
http://hdl.handle.net/10985/19539
Sensorless Nonlinear Stroke Controller for an Implantable, Undulating Membrane Blood Pump
SCHEFFLER, Mattias; BARABINO, Nicolas; MONTEIRO, Eric; MECHBAL, Nazih; RÉBILLAT, Marc
This paper describes an original methodology to operate a new nonlinear vibrating membrane pump, actuated by a moving magnet actuator without the use of a motion sensor, in the scope of cardiac assistance. A nonlinear mathematical model of the system is established and used to parametrize a nonlinear position observer that uses the coils current as an input and which output is a feedback to a stroke controller. Actuator’s parameters are identified by a recursive least square algorithm and direct measurements. Finally, a numerical experiment illustrates the implementation of the algorithm and its possible applications.
Tue, 01 Jan 2019 00:00:00 GMThttp://hdl.handle.net/10985/195392019-01-01T00:00:00ZSCHEFFLER, MattiasBARABINO, NicolasMONTEIRO, EricMECHBAL, NazihRÉBILLAT, MarcThis paper describes an original methodology to operate a new nonlinear vibrating membrane pump, actuated by a moving magnet actuator without the use of a motion sensor, in the scope of cardiac assistance. A nonlinear mathematical model of the system is established and used to parametrize a nonlinear position observer that uses the coils current as an input and which output is a feedback to a stroke controller. Actuator’s parameters are identified by a recursive least square algorithm and direct measurements. Finally, a numerical experiment illustrates the implementation of the algorithm and its possible applications.Optimal Sensors Placement to Enhance Damage Detection in Composite Plates
http://hdl.handle.net/10985/8234
Optimal Sensors Placement to Enhance Damage Detection in Composite Plates
FENDZI, Claude; MOREL, Julien; COFFIGNAL, Gérard; MECHBAL, Nazih; GUSKOV, Mikhail; RÉBILLAT, Marc
This paper examines an important challenge in ultrasonic structural health monitoring (SHM), which is the problem of the optimal placement of sensors in order to accurately detect and localize damages. The goal of this study is to enhance damage detection through an optimal sensor placement (OSP) algorithm. The problem is formulated as a global optimization problem, where the objective function to be maximized is evaluated by a ray tracing approach, which approximately models Lamb waves propagation. A genetic algorithm (GA) is then used to solve this optimization problem. Simulations and experiments were conducted to validate the proposed method on a carbon epoxy composite plate. Results show the effectiveness and the advantages of the proposed method as a tool for OSP with reasonable computation time.
Wed, 01 Jan 2014 00:00:00 GMThttp://hdl.handle.net/10985/82342014-01-01T00:00:00ZFENDZI, ClaudeMOREL, JulienCOFFIGNAL, GérardMECHBAL, NazihGUSKOV, MikhailRÉBILLAT, MarcThis paper examines an important challenge in ultrasonic structural health monitoring (SHM), which is the problem of the optimal placement of sensors in order to accurately detect and localize damages. The goal of this study is to enhance damage detection through an optimal sensor placement (OSP) algorithm. The problem is formulated as a global optimization problem, where the objective function to be maximized is evaluated by a ray tracing approach, which approximately models Lamb waves propagation. A genetic algorithm (GA) is then used to solve this optimization problem. Simulations and experiments were conducted to validate the proposed method on a carbon epoxy composite plate. Results show the effectiveness and the advantages of the proposed method as a tool for OSP with reasonable computation time.Damage indexes comparison for the structural health monitoring of a stiffened composite plate
http://hdl.handle.net/10985/12042
Damage indexes comparison for the structural health monitoring of a stiffened composite plate
MECHBAL, Nazih; RÉBILLAT, Marc
Stiffened composite structures are very appealing in aeronautic applications due to their unique stiffness to mass ratio. However, they are also prone to various and complex damage scenario (stiffener debonding, impact damage...) and to complex wave propagation phenomena due to the presence of the stiffener. Consequently, autonomous monitoring of such structure is still a real issue. The process of monitoring in real-time a structure is referred to structural health monitoring (SHM) and consists of several steps: damage detection, localization, classification, and quantification. The focus is put here on the damage detection step of SHM. To detect damages, stiffened composite structures are equipped with piezoelectric elements that act both as sensors and actuators. A database at the unknown (and possibly damaged state) is then compared to a healthy reference database. Several damage indexes (DIs) designed for detection are extracted from this comparison. The SHM process classically relies on four sequential steps: damage detection, localization, classification, and quantification. The most critical step of such process is the damage detection step since it is the first one and because performances of the following steps depend on it. A common method to design such a detector consists in relying on a statistical characterization of the damage indexes available in the healthy behavior of the structure. On the basis of this information, a decision threshold can then be computed in order to achieve a desired probability of false alarm (PFA). In this paper, the performances of these DIs with respect to damage detection in a stiffened composite plate are studied. Results show that DIs based on energy consideration perform better than the ones based on cross-correlation. Furthermore Fourier-transform based DIs appear to be insensitive to the presence of damage in such structure.
Sun, 01 Jan 2017 00:00:00 GMThttp://hdl.handle.net/10985/120422017-01-01T00:00:00ZMECHBAL, NazihRÉBILLAT, MarcStiffened composite structures are very appealing in aeronautic applications due to their unique stiffness to mass ratio. However, they are also prone to various and complex damage scenario (stiffener debonding, impact damage...) and to complex wave propagation phenomena due to the presence of the stiffener. Consequently, autonomous monitoring of such structure is still a real issue. The process of monitoring in real-time a structure is referred to structural health monitoring (SHM) and consists of several steps: damage detection, localization, classification, and quantification. The focus is put here on the damage detection step of SHM. To detect damages, stiffened composite structures are equipped with piezoelectric elements that act both as sensors and actuators. A database at the unknown (and possibly damaged state) is then compared to a healthy reference database. Several damage indexes (DIs) designed for detection are extracted from this comparison. The SHM process classically relies on four sequential steps: damage detection, localization, classification, and quantification. The most critical step of such process is the damage detection step since it is the first one and because performances of the following steps depend on it. A common method to design such a detector consists in relying on a statistical characterization of the damage indexes available in the healthy behavior of the structure. On the basis of this information, a decision threshold can then be computed in order to achieve a desired probability of false alarm (PFA). In this paper, the performances of these DIs with respect to damage detection in a stiffened composite plate are studied. Results show that DIs based on energy consideration perform better than the ones based on cross-correlation. Furthermore Fourier-transform based DIs appear to be insensitive to the presence of damage in such structure.Spatial integration of baseline-free damage detection algorithms based on dual-PZT for the structural health monitoring of anisotropic composite aeronautic structures
http://hdl.handle.net/10985/19521
Spatial integration of baseline-free damage detection algorithms based on dual-PZT for the structural health monitoring of anisotropic composite aeronautic structures
LIZE, Emmanuel; BOLZMACHER, Christian; MECHBAL, Nazih; RÉBILLAT, Marc
The focus is put here on the Structural Health Monitoring (SHM) of composite aeronautic structure using Lamb waves emitted and recorded with piezoelectric transducers (PZT). Conventional algorithms perform Lamb waves acquisition in the healthy state of the structure (referred to as the “baseline”) and then compare incoming data from an unknown state with this one to detect, locate, classify and quantify any potential damage. The acquisition, storage, and update of the initially recorded baseline database constitute a severe drawback of such algorithms. Indeed, the structure under study as well as the environment may vary during its operational life without the appearance of any damage and thus the initial baseline may not be relevant at any instant where damage monitoring is needed. In order to circumvent this drawback, “baselinefree” method (such as the instantaneous baseline [BI] and rupture of reciprocity [RR]) have been developed. Moreover, the use of dual-PZT, i.e. concentric PZT made of a ring and a disk lying on the same ceramic, has been shown as attractive for baselinefree purposes. However, now that several algorithms based on dual-PZT are available, no study dealing with the spatial integration of the results provided by these algorithms have been reported in the literature. It is thus proposed in this paper to investigate strategies for the spatial integration of common baseline-free methods (namely BI and RR) on an experimental case of damage on a highly anisotropic composite plate. Results illustrate the decomposition of Lamb wave modes in signals measured via dual PZTs as well as the proposed spatial integration strategies for these methods.
Tue, 01 Jan 2019 00:00:00 GMThttp://hdl.handle.net/10985/195212019-01-01T00:00:00ZLIZE, EmmanuelBOLZMACHER, ChristianMECHBAL, NazihRÉBILLAT, MarcThe focus is put here on the Structural Health Monitoring (SHM) of composite aeronautic structure using Lamb waves emitted and recorded with piezoelectric transducers (PZT). Conventional algorithms perform Lamb waves acquisition in the healthy state of the structure (referred to as the “baseline”) and then compare incoming data from an unknown state with this one to detect, locate, classify and quantify any potential damage. The acquisition, storage, and update of the initially recorded baseline database constitute a severe drawback of such algorithms. Indeed, the structure under study as well as the environment may vary during its operational life without the appearance of any damage and thus the initial baseline may not be relevant at any instant where damage monitoring is needed. In order to circumvent this drawback, “baselinefree” method (such as the instantaneous baseline [BI] and rupture of reciprocity [RR]) have been developed. Moreover, the use of dual-PZT, i.e. concentric PZT made of a ring and a disk lying on the same ceramic, has been shown as attractive for baselinefree purposes. However, now that several algorithms based on dual-PZT are available, no study dealing with the spatial integration of the results provided by these algorithms have been reported in the literature. It is thus proposed in this paper to investigate strategies for the spatial integration of common baseline-free methods (namely BI and RR) on an experimental case of damage on a highly anisotropic composite plate. Results illustrate the decomposition of Lamb wave modes in signals measured via dual PZTs as well as the proposed spatial integration strategies for these methods.