Detection Of Debonding Research Articles

Interface Debonding Detection of Precast Segmental Concrete Beams (PSCBs) Using Piezoceramic Transducer-Based Active Sensing Approach

An active sensing approach using piezoceramic induced stress wave is proposed to provide monitoring and early warning for the development of interface debonding damage of precast segmental concrete beams (PSCBs). Three concrete specimens with toothed interfaces were fabricated and bonded with high-strength epoxy resin adhesive to form PSCBs. Smart aggregates (SAs) embedded in concrete specimens are used as actuators and sensors. The PSCBs are subjected to periodic loading with hydraulic jack to test the different degrees of debonding damage. The experimental results of time-domain and frequency-domain analysis clearly show that the amplitude of the signal received by the piezoceramic sensor is reduced when debonding crack occurs. The energy analysis and damage index based on wavelet packet can be used to determine the existence and severity of interface debonding damage in PSCBs. The experimental research validates the feasibility of monitoring the interface debonding damage in PSCBs using SA transducers based on active sensing technique.

Interfacial debonding detection of strengthened steel structures by using smart CFRP-FBG composites

The interfacial debonding detection of multi-layered strengthened structures (i.e. carbon fiber reinforced polymer (CFRP) strengthened steel/concrete beams) has always been an important problem urgent to be solved. Fiber Bragg grating (FBG) sensor is limited to directly perceive the shear strain. How to monitor the interfacial bonding state based on optical fiber sensing technology thus attracts high attention. A smart CFRP-FBG composite has then been developed in this paper. The structural integrity of the composites has been non-destructively checked by ultrasonic testing technique. Theoretical study on the strengthened steel beam has been conducted to establish a relationship between the interfacial shear stress and the normal stress of the CFRP-FBG composites. Loading tests have been performed to check the measurement accuracy of the FBGs in series and the effectiveness of the composites to perceive the interfacial debonding failure. Results indicate that the proposed smart CFRP-FBG composites can accurately identify the interfacial debonding of the multi-layered structures. The degradation process of the interfacial bonding state can be favorably reflected by the variations of strain profiles measured by the FBGs in series in the composites. The proposed method can be used to instruct the concept design of damage detection. The developed CFRP-FBG composites can be adopted to identify the damage and make in-time maintenance in practical engineering.

Toward Creating a Portable Impedance-Based Nondestructive Testing Method for Debonding Damage Detection of Composite Structures

Debonding detection of composite structures is a vital task as such damage weakens the structure leading to a failure. As adhesive bonding is a more preferable choice over the conventional mechanical fastening method, detecting debonding as early as possible could minimize the overall maintenance costs. For this reason, a vast amount of research in the nondestructive testing field is being conducted as we speak. However, most of the methods may require well-trained experts or heavy equipment. In this study, the piezoelectric (PZT) material-based method known as the electromechanical impedance technique is investigated to seek the possibility of making the technique very cheap and portable by temporarily attaching the sensor. Furthermore, ANSYS simulation studies using smaller PZT patches as small as 0.1 mm × 0.1 mm are simulated to investigate the impedance signatures acquired from the simulations. The results show the possibility of using smaller PZT patches compared to the conventional PZT sizes of 10 mm × 10 mm for a successful damage identification process.

Detection of edge debonding in composite patch using novel post processing method of thermography

In the present work, the step heating thermography technique has been used to detect disbond defects at the edge of the adhered carbon/epoxy patch on the aluminum plate. The four common post-processing algorithms including principle component analysis (PCA), thermal signal reconstruction (TSR), Fourier transform (FT), and one-dimensional wavelet transform (1D WT) have been applied to the infrared thermal images obtained from the composite patch thermography inspection. A novel post processing method based on the area under temperature-time curve (Thermal Signal Area: TSA) has been proposed for the infrared thermal image analysis. The proposed post-processing method is fast and non-sensitive to noise. A comparison of the new proposed method with the four common post-processing methods has been carried out on disbond detection in a composite patch in a quantitative and qualitative manner. Furthermore, a data fusion of the proposed method with the 1D wavelets transform has been applied to disbond defect characterization which improves the accuracy by decreasing noise level.

Debonding Detection and Monitoring for CFRP Reinforced Concrete Beams Using Pizeoceramic Sensors.

The bonding status between Carbon Fiber Reinforced Polymer (CFRP) and concrete is one of the key issues for the safety of CFPR-reinforced structures, thus it is of great importance to detect the debonding as early as possible. Instead of detecting the debonding which is artificially set at the very beginning, this paper investigates the feasibility of using low-cost piezoceramic sensors to detect and monitor the debonding of CFRP-reinforced concrete beams in situ. For existing debonding detection, a concrete beam reinforced with CFRP sheet was loaded through the three-point bending test till failure to induce debonding between CFRP sheet and the concrete substrate, and piezoceramic sensors were used to detect the existing debonding by analyzing the receiving ultrasonic waves. In addition, the debonding detection results were further compared with and verified by the vision-based strain testing results. For in-situ debonding monitoring, 10 piezoceramic sensors were used as an array to track the wave transmission changes during the loading process of a CFRP-reinforced concrete beam, and the debonding development process was successfully monitored. The test results show that the low-cost piezoceramic sensors are very effective to generate and receive ultrasonic waves, and are capable of detecting the existing debonding and monitoring of the in-situ debonding process as well.

Performance assessment of SVM-based classification techniques for the detection of artificial debondings within pavement structures from stepped-frequency A-scan radar data

Owing to traffic and weather conditions, pavement structures may suffer from horizontal and vertical cracks that shorten the overall lifetime of roadways. In this paper, we focus on the detection of the horizontal subsurface cracks (debondings) occurring between the first two pavement layers from Stepped-frequency Radar (SFR) data. The processing of radar data requires some refined signal analysis to detect constructive interference between overlapping echoes. It is performed from timely data by a supervised machine learning method namely, Support Vector Machines (SVM) and compared to the conventional reference method, namely, the Amplitude Ratio Test (ART), which is routinely performed at the operational level. Besides, the straightforward application of SVM on raw data is compared to the solution using physical signal features (global and local) that reduces the computational burden. Performance assessment and comparison of the processing methods are conducted on data collected on a specific test-site with three different types of artificial debondings.

Interfacial Debonding Detection for Rectangular CFST Using the MASW Method and Its Physical Mechanism Analysis at the Meso-Level

In this study, the transient multichannel analysis of surface waves (MASW) is proposed to detect the existence, the location and the length of interface debonding defects in rectangular concrete-filled steel tubes (CFST). Mesoscale numerical analysis is performed to validate the feasibility of MASW-based interfacial debonding detection. Research findings indicate that the coaxial characteristics in the Rayleigh wave disperse at the starting point of the debonding area and gradually restores at the end of the defect. For healthy specimens, the surface wave mode in CFST is closer to the Rayleigh wave. However, it can be treated as a Lamb wave since the steel plate is boundary-free on both sides in the debonding area. The displacement curves are further investigated with forward analysis to obtain the dispersion curves. The mesoscale numerical simulation results indicate that the propagation characteristic of the surface wave is dominated by the debonding defect. The detectability of interfacial debonding detection for rectangular CFST using the MASW approach is numerically verified in this study. The proposed MASW-based nondestructive testing technique can achieve bond-slip detection by comparing the variation trend of the coaxial characteristics in the time-history output signals and the dispersion curves obtained from the forward analysis, for avoiding misjudgment of the experimental observations.

Guided Wave Propagation in Detection of Partial Circumferential Debonding in Concrete Structures.

The following article presents results of investigating the damage detection in reinforced concrete beams with artificially introduced debonding between the rod and cover, using a non-destructive method based on elastic waves propagation. The primary aim of the research was to analyze the possible use of guided waves in partial circumferential debonding detection. Guided waves were excited and registered in reinforced concrete specimens with varying extents of debonding damage by piezoelectric sensors attached at both ends of the beams. Experimental results in the form of time–domain signals registered for variable extent of debonding were compared, and the relationships relating to the damage size and time of flight and average wave velocity were proposed. The experimental results were compared with theoretical predictions based on dispersion curves traced for the free rod of circular cross-section and rectangular reinforced concrete cross-section. The high agreement of theoretical and experimental data proved that the proposed method, taking advantage of average wave velocity, can be efficiently used for assessing debonding size in reinforced concrete structures. It was shown that the development of damage size in circumferential direction has a completely different impact on wave velocity than development of debonding length. The article contains a continuation of work previously conducted on the detection of delamination in concrete structures. The proposed relationship is the next essential step for developing a diagnostics method for detecting debondings of any size and orientation.

Stringer debonding edge detection employing fiber optics by combined distributed strain profile and wave scattering approaches for non-model based SHM

The paper presents a comparison of two novel damage detection approaches for interrogating stiffened composites. A guided wave assessed methodology based on piezoelectric patches is integrated with a distributed fiber optic sensor providing a cost-effective and time-saving monitoring system. Being the two techniques characterized by different sample ranges, they are prone to be integrated without any interference or cross talk effect and can be applied to provide a redundant inspection system.The structural health monitoring by distributed fiber optic is a non-model based damage detection method. The relative aspect ratio between shape profile at different time stamps or at different locations along the fiber segments are taken into consideration and the first order derivative is applied, both in time and spatial domain, correlating sensors values characterized by high gradient events. The occurrences of a such dispersed pattern can be associated to a structural non-linearity induced by damage. In order to make this approach effective the PZT guided wave scattering methodology is used as reference. Both systems are tested to the same specific target, nominally a composite stiffened plate undergoing to impact. Good results are reported when comparing the resolutions of the two methodologies, indeed verified by ultrasonic nondestructive investigation analysis.

Enhancement of thermographic images of composite laminates for debond detection: An approach based on Gabor filter and watershed

Spacecraft structures use materials which require high stiffness and low mass. Subjected to high thermal and acoustic loads, their health is of utmost importance. These structures are vulnerable to debonding and delaminations which are identified as defects. Non-destructive way of inspecting these components is very essential to detect the debonding defects. Debond defects are not visible to naked eyes and hence conventional optical cameras will not serve the purpose of automating inspection. For this purpose, we have used thermography. Passing the thermographic images through stages like enhancement, segmentation and feature extraction by using techniques like watershed segmentation, active contours and texture classification through Gabor filter are attempted in this study. Defects are brought out which help in taking corrective steps to avoid failure of the materials during actual life of the spacecraft.

Detection of debonding in adhesive joints using Lamb wave propagation

Adhesively bonded joints are widely used in many branches of industry. Mechanical degradation of this type of connections does not have significant symptoms that can be noticed during visual assessment, so non-destructive testing becomes a very important issue. The paper deals with experimental investigations of adhesively bonded steel plates with different defects. Five samples (an intact one and four with damages in the form of partial debonding) were prepared. The inspection was conducted with the use of guided wave propagation method. Lamb waves were excited at one point of the sample, whereas the out-of-plane velocity signals were recorded in a number of points spread over the area of overlap. The processing of signals consisted of calculations of weighted root mean square (WRMS). The results of the analysis showed that the WRMS maps allow for identification and determination of size and shape of debonding areas.

Thermal barrier coating debonding defects detection based on infrared thermal wave testing technology under linear frequency modulation heat exitation

Thermal barrier coating debonding defects detection based on infrared thermal wave testing technology under linear frequency modulation heat excitation was studied. The principle the infrared thermal wave testing technology under linear frequency modulation was presented. The effects of different light source power and Chirp modulation frequency on signal-to-noise ratio were compared and analyzed. The results show that, defects can be more easily detected with the bigger power of light source, and the signal-to-noise ratio can be increased by using lower initial and termination frequencies.

A Linear Prediction and Support Vector Regression-Based Debonding Detection Method Using Step-Frequency Ground Penetrating Radar

In the field of civil engineering, ground penetrating radar (GPR) is a highly efficient nondestructive testing tool for sustainable management of pavement infrastructures. GPR allows to evaluate the structure of the roadway over large distances (with contactless configurations) and to detect significant subsurface defects. This letter presents a new method to detect thin debondings within pavement structures with the step-frequency GPR. The proposed method enables us to carry out the detection with only a small number of frequency samples and A-scans. It is based on the linear prediction and support vector regression theories. Two experimental results show its effectiveness.

Nondestructive analysis of core-junction and joint-debond effects in advanced composite structure

This paper presents a theoretical, numerical and experimental analysis of Lamb wave propagation and joint-debond identification in an advanced composite structure with core-junction. In the process, the wave modes in the recorded sensor-signals are effectively identified based on the theoretically obtained time-history response and dispersion curves for the sample structure. In order to study the core-junction and joint-debond effects, the finite element based numerical simulations were carried out in ABAQUS and the results verified with laboratory experiments. It was observed that the presence of core-junction in the structure reduces the propagating Lamb wave mode amplitudes, whereas the presence of localized joint-debond significantly increases the modal amplitudes. The study was further extended for the analysis of variable core-junction thickness and joint-debond size effects on the amplitude difference between the baseline and affected Lamb wave signals. Finally, a baseline-free debond detection strategy is proposed for the detection of hidden joint-debond locations in the target structure.

Numerical study on interface debonding detection mechanisms with 2D spectral element method for concrete-filled steel tube using embedded PZT sensor

Interface debonding detection approaches based on stress wave measurement for concrete-filled steel tube (CFST) members have received a great deal of attention in civil and infrastructural engineering societies. The development of efficient computing approaches to investigate the mechanisms of the interface debonding detection approaches and the effect of interface debonding on wave propagation within CFST members is critical. In this study, the wave propagation within the cross section of CFST members with and without interface debonding under a single point excitation force is simulated with a two-dimensional (2D) spectral element method (SEM) at first and that of CFST models coupled with a surface-mounted piezoelectric lead zirconate titanate (PZT) actuator and an embedded PZT sensor in the concrete core under continuous and sweep sinusoidal signals is simulated with the 2D SEM and a piezoelectric spectral element. The debonding defect is modeled by removing concrete elements between the steel tube and the concrete core. Results show that interface debonding affects the wave propagation process, the output potentials of the embedded PZT sensors as well as the displacement responses at different locations of CFST specimens obviously. Rayleigh damping identified from experiments is introduced to the SEM models to reflect wave attenuation in the coupled models. The effect of interface debonding on the amplitude, the Fourier spectra and the wavelet packet energy of stress waves are analyzed. For comparison, another numerical model in which the PZT actuator is not located near the interface debonding defect is studied numerically and the effect of the debonding defect on the response of the embedded PZT sensor is illustrated. SEM provides an efficient way to simulate stress wave propagation and to understand the mechanisms of interfacial debonding defect detection for CFSTs with PZT technique.

Debonding detection for rectangular CFST using surface wave measurement: Test and multi-physical fields numerical simulation

Abstract The interfacial debonding detection approach for concrete-filled steel tubular (CFST) members using surface-mounted piezoelectric-lead-zirconate-titanate (PZT) actuators and sensors is experimentally and numerically investigated. In this study, an interfacial debonding detection approach using surface wave measurement with PZT patches is propoed firstly and experimental investigation on the feasibility of the proposed approach with two CFST specimens with different levels of interface debonding defects is carried out. For comparison, a PZT sensor is also embedded in concrete core to measure the stress wave traveling from the surface-mounted PZT actuator. Experiment results indicate that the voltage amplitude of the embedded PZT sensor representing the wave propagation from the steel plate into the concrete core decreases due to the existence of interfacial debonding defect, but the output signal of the surface-mounted PZT sensor increases accordingly when interface debonding occurs. Moreover, the increment of surface-mounted PZT sensor measurement is related to the dimension of the interface debonding defects. The experimental finding implies that the interface debonding is detectable using surface wave measurement. In order to investigate the mechanism of the proposed approach, numerical study on the wave propagation process in CFSTs is further discussed by using three-dimensional (3D) solid element models and two-dimensional (2D) plane strain models, respectively. Finally, in order to consider the effect of nonhomogeneous meso-scale structure of concrete on the wave propagation, a random aggregate method (RAM) is employed to model the concrete core and multi-physical fields coupling numerical analysis on stress wave propagation of the CFST member with different interface debonding defects is performed. The numerical findings meet well with the experimental observations and the results indicate that the interface debonding of CFST can be detected efficiently using surface wave measurement.

Sparse ensemble matrix factorization for debond detection in CFRP composites using optical thermography

With the increasing use of CFRP in aircraft and automotive industry, it has become necessary to monitor the health of the composite structure during the manufacture and service process from flaws such as debond or delamination by using optical pulsed thermography non-destructive testing (OPTNDT) techniques. However, current OPTNDT methods cannot efficiently tackle the influence from the strong noise, and the resolution enhancement of the defects detection remains as a critical challenge. To alleviate this problem, this paper proposes the sparse ensemble matrix factorization approach to remove the noise and enhance the resolution for the defects detection. Specifically, the algorithm is based on the sparse representation and noise is modeled as a mixture of Gaussian (MoG) distribution. It provides a projection from the raw data onto the sparse and low dimensional sub-space while the defects information is significantly enhanced with the layer decomposed approach in the low dimensional space. Not withstand above, a Gaussian low pass filtering and non-linear enhancement is conducted for further enhancement. The proposed method is coupled with several comparison studies to verify the efficacy.

Debonding Detection in Hidden Frame Supported Glass Curtain Walls Using the Nonlinear Ultrasonic Modulation Method with Piezoceramic Transducers.

Debonding defects are common and they are the main reason for the failure of hidden frame supported glass curtain walls, which are widely used as an external enclosure and decorative structure. In this paper, a debonding detection method for hidden frame supported glass curtain walls is developed based on nonlinear ultrasonic modulation and piezoceramic transducers. First, the excitation frequency was determined according to the response characteristics. Then, empirical mode decomposition (EMD) was applied to extract the feature components. After discrete Fourier transform (DFT), the nonlinear coefficients were calculated to evaluate the debonding defect. Finally, the experimental setup was established and a series of experiments were carried out to verify the feasibility and effectiveness of the nonlinear ultrasonic modulation method. The nonlinear harmonics detection method was also investigated and it was compared with the nonlinear ultrasonic modulation method. The detection effect at different temperatures and impact were studied. The results showed that the nonlinear coefficient increases with the debonding length. The mean squared error (MSE) of the nonlinear ultrasonic modulation method was improved by 41% compared with the nonlinear harmonics method. The nonlinear ultrasonic modulation method can successfully detect debonding defects in hidden frame supported glass curtain walls at different temperatures and impact.

Automatic seeded region growing for thermography debonding detection of CFRP

The carbon fiber reinforced polymer (CFRP) has been widely used in aerospace, automobile and sports industries. In laminated composite materials, cyclic stresses and impact will cause internal defects such as delamination and debonding. In order to guarantee internal quality and safety, optical pulsed thermography (OPT) nondestructive testing has been used to detect the internal defects. However, current OPT methods cannot efficiently tackle the influence from uneven illumination, and the resolution enhancement of the defects detection remains as a critical challenge. In this paper, a hybrid of thermographic signal reconstruction (TSR) and automatic seeded region growing (ASRG) algorithm is proposed to deal with the thermography processing of CFRP. The proposed method has the capability to significantly minimize uneven illumination and enhance the detection rate. In addition, it has the capacity to automate segmentation of defects. It also overcomes the crux issues of seeded region growing (SRG) which can automatically select the growth of image, seed points and thresholds. The probability of detection (POD) has been derived to measure the detection results and this is coupled with comparison studies to verify the efficacy of the proposed method.

Skin–stringer debonding detection using distributed dispersion index features

Statistical approaches have been extensively used to detect structural damage. This article proposes a preliminary investigation on the use of a non-model-based damage identification method, implementing “dispersion feature” indicators, extracted from the differential strain signal. In detail, the method takes advantage of the elaboration of the full-spectrum acquisition, irrespective of the healthy state of the structure under test. Large variations of some selected statistical features, representative of the acquired signals, are taken as indicators of the presence of anomalous structural condition. At this stage, these features have been arbitrarily selected. In synthesis, a cumulative dispersion index is defined as the combination of the selected feature variations, contemporarily overcoming prescribed thresholds, providing a scalar output that can be used as an index to identify and possibly quantify the extension of a damage location. Experimental results confirm the envisaged potentiality of the proposed technique. In this study, damage in the form of a stringer debonding is referred to, obtained as a consequence of point impacts on a wing box stiffened panel. A distributed fiber optic strain sensor network is used to detect the input data.