Debonding Defect Detection Research Articles

Robot-based dynamic optics scanning infrared thermography for debonding defect detection of big-sized CFRP specimen

ABSTRACT The use of infrared thermography (IRT) for non-destructive testing (NDT) of large aerospace composites, such as carbon fibre reinforced polymer (CFRP), is often limited by the narrow field of view infrared cameras. This paper experimentally investigates the big-sized CFRP specimens with simulated debonding defects using a robot-based dynamic optics scanning infrared thermography (RDOS-IRT) method to meet these issues. Then, static pulse IRT and RDOS-IRT were performed, and the processing performance of different algorithms (pulsed phase thermography, PPT; total harmonic distortion, THD; matched filtering, MF; and supervised dimensionality reduction, SDR) on pulsed IRT was discussed. A combination of pseudo-static matrix reconstruction (FSMR) algorithm and static image sequence processing algorithm is innovatively adopted to improve the defect detection performance of RDOS-IRT results. The experiments show that the RDOS-IRT method with FSMR and static image sequence processing algorithm is effective; moreover, it has almost a similar detection ability compared to the traditional static pulse IRT method in practical applications and saves more time. Results show that the signal-to-noise ratio (SNR) of the repeated defects is not differentiated, and the detection effect is similar. Therefore, the RDOS-IRT method is a reliable tool for NDT tasks on big-sized CFRP specimens and can be practically applied in an industrial setting for high detection efficiency.

Interface debonding defect detection for CFST columns based on EMI measurements: Experiment, numerical simulation and blind inspection in practice

Concrete-filled steel tube (CFST) members have been widely used in skyscrapers and long-span bridges. Non-uniformly distributed hydration heat during curing, inadequate compaction during construction and unavoidable shrinkage and creep of mass concrete in service most likely lead to interface debonding defects between concrete core and steel tube, which has been a common concern. The development of effective non-destructive inspection methods for interface bonding condition of existing CFST members is critical. In this study, an interface debonding defect detection method based on electromechanical impedance (EMI) measurement using surface-mounted piezoelectric-lead-zirconate-titanate (PZT) sensors is proposed at first. Then, experimental study on the feasibility of the proposed approach is carried out with scaled CFST specimens with artificially mimicked interface debonding defects. EMI of surface-mounted PZT sensors at different frequency bands are measured and compared to verify the detectability of the proposed approach for the mimicked interface debonding defects. Thirdly, a multi-physics CFST-PZT coupling finite element model (FEM) with interface debonding defects is established, and EMI of surface-mounted PZT sensors at different locations is simulated. The influence of interface debonding defects on EMI measurements is illustrated. Finally, a blind inspection on the interface bonding condition of selected CFST columns in an existing skyscraper in service using the proposed approach is carried out. Both bonding and debonding defect in the tested CFST columns are detected correctly and validated with drilling hole observation. Experimental, numerical and engineering application results show the proposed approach is effective for interface debonding detection of CFST members and sensitive to minor debonding defect of 0.3 mm in CFST members.

Debonding Defect Detection by Applying Pulsed, Lock-in and Linear Frequency Modulation Thermal Excitation Methods in the Inspection of Fiber-Reinforced Metal Laminates

Debonding Defect Detection by Applying Pulsed, Lock-in and Linear Frequency Modulation Thermal Excitation Methods in the Inspection of Fiber-Reinforced Metal Laminates

LFM-Chirp-Square pulse-compression thermography for debonding defects detection in honeycomb sandwich composites based on THD-processing technique

ABSTRACT Honeycomb Sandwich Composites (HSCs) have been widely used in aerospace and aircraft industries because of their high temperature and corrosion resistance, etc. As defects and damage to HSCs are unavoidable, non-destructive testing (NDT) is essential to ensure the reliability of HSCs. A series of artificial flat-bottomed holes (FBHs) defects of HSCs were prepared for pulse thermography (PT) and LFM-Chirp-Square pulse-compression thermography (PuCT). LFM-Chirp-Square PuCT has the advantage of frequency modulation over PT to detect different depth ranges of FBHs defects. In order to improve the efficiency of defect detection, pulse phase thermography (PPT) and total harmonic distortion (THD) techniques were applied to process the infrared image sequences. The results show that THD processing technique outperforms the PPT processing technique in improving the signal-to-noise ratio (SNR) from feature images. The combination of LFM-Chirp-Square PuCT and THD techniques can be applied to improve the defect detection identification results in HSCs.

Interface debonding detection of grouted connection based on Lamb wave energy leakage

Grouted connections (GCs) are transitional elements that have been extensively employed in offshore wind turbine support structure to transfer loads from superstructure to foundation. However, interface debonding defects between steel tube and grout layer have an adverse effect on the durability and fatigue resistance of the GC. An effective interface debonding defects detection approach for GC is necessary. In this study, interface debonding defects detection approach based on Lamb wave energy leakage was proposed and validated numerically and experimentally. Numerical studies on Lamb wave energy leakage models and the GC models were performed to study mechanism of detection approach. Lamb wave is excited on the surface, and stress wave fields and time-history response of models were extracted and compared. Experimental investigations were carried out to verify the applicability of the proposed approach in practice. A scaled GC specimen was constructed and Lamb wave was excited by the PZT patches mounted on the surface of GC specimen. The output voltage of surface-mounted PZT sensors under different axial loads were compared. Both numerical and experimental results show that the proposed approach is effective to the detection of interface debonding defects. The damage evolution index (DEI) based on wavelet packet energy is defined and it can be adopted to qualitatively determine the initiation and evolution of the damage.

Multi-Physics Mesoscale Substructure Analysis on Stress Wave Measurement within CFST-PZT Coupling Models for Interface Debonding Detection.

In recent years, the development of interface debonding defect detection methods for concrete-filled steel tubes (CFSTs) using stress wave measurement with piezoelectric-lead-zirconate-titanate (PZT) actuator and sensor has received significant attention. Because the concrete core in CFSTs is a heterogeneous material with randomness at the mesoscale, the size, position and distribution of aggregates unavoidably affect the stress wave propagation and the PZT sensor response. In this study, to efficiently investigate the influence of the mesoscale structure of the concrete core of CFSTs on the response of embedded PZT sensors, a multi-physics substructure model of CFST members coupled with a PZT actuator and a PZT sensor, where a single circular aggregate with different size and position and randomly distributed circular aggregates are considered, are established first. Then, multi-physics simulations on the effect of the local mesoscale structure of the concrete core on the response of the embedded PZT sensor excited by both a sinusoidal signal and sweep frequency signal are carried out. Moreover, corresponding multi-physics and mesoscale simulations on the embedded PZT sensor response of substructures with different interface debonding defects are also carried out for comparison. The amplitude and the wavelet packet energy of the embedded PZT sensor response of each mesoscale substructure are employed to distinguish the influence of the concrete core mesoscale structure and interface debonding defect on sensor measurement. The findings from the results with the multi-physics coupling substructure models are compared with those of the full CFST-PZT coupling models and the tested members of the previous studies to verify the rationality of the embedded PZT sensors measurement of the established substructure models. Results from this study show that the effect of interface debonding defect on the amplitude and the wavelet packet energy of the embedded PZT sensor measurement of the CFST members is dominant compared with the mesoscale heterogeneity and randomness of the concrete core.

Local wave propagation analysis in concrete-filled steel tubes with spectral element method using absorbing layers – Part II: Application in coupling system

In this paper, a two-dimensional (2D) time domain spectral element method (SEM) is developed for concrete-filled steel tube (CFST) and piezoelectric lead zirconate titanate (PZT) patches coupling system, where the piezoelectric and inverse piezoelectric effect of PZT actuator and sensor and their coupling effect with CFST are considered. The local wave field and the response of the embedded PZT sensor was numerically studied in a substructure of the CFST coupled with PZT patches and surrounded by absorbing layers with increasing damping (ALID) and the performance of the ALID in attenuating wave reflection at boundaries of the coupling substructure model is further investigated. Then, numerical simulation on the effect of interface debonding defect on local wave propagation within the coupling substructure model surrounded by the designed ALID was carried out. By comparing the displacement-based wave fields and the response of the embedded PZT sensor within the substructure, the effect of interface debonding defect on the wave propagation along the steel tube and in the concrete core, and the time history of the response voltage of the embedded PZT sensor is investigated in detail. Numerical results show that interface debonding defects in the substructure leads to changes in the wave propagation path, the local wave field, the time duration of wave travelling to the embedded PZT sensor from the PZT actuator mounted on the surface of the steel tube of CFST, as well as response voltage of the embedded PZT sensor. In addition, PZT sensor measurement is sensitive to the length of interface debonding defects but insensitive to their depth. SEM for the coupling substructure model with ALID instead of the model of whole cross section of CFST provides an efficient way to simulate the local elastic wave propagation for understanding the mechanism of the interface debonding defects detection approach based on wave measurement.

Debonding defects detection of FMLs based on long pulsed infrared thermography technique

Fiber metal laminates (FMLs) are the popular materials in the fields of aerospace, automobile and rail transportation. In the process of preparation and service, the defects of matrix, fiber fracture and fiber matrix debonding are easily produced, which poses a threat to the safety of FMLs’ quality, performance and the operational safety of the aircraft and other equipment using the material. Aiming at developing a method for defects detection in FMLs by long pulsed infrared thermography, test was applied to FMLs with debonding defects. Halogen lamps were used as active heat source into the sample, and the infrared image sequence was collected with an infrared camera A325sc. Thermal wave signal reconstruction, pulsed phase thermography and principal component analysis methods were used to process the original image sequences. Experimental results show that the signal-to-noise of processed images by these three methods are all increased, while that of principal component analysis method increases significantly under the same given test parameters, and it can be used to detect the defects in FMLs.

Experimental Study on Active Interface Debonding Detection for Rectangular Concrete-Filled Steel Tubes with Surface Wave Measurement.

Concrete-filled steel tube (CFST) members have been widely employed as major structural members carrying axial or vertical loads and the interface bond condition between steel tube and concrete core plays key roles in ensuring the confinement effect of steel tube on concrete core. An effective interface debonding defect detection approach for CFSTs is critical. In this paper, an active interface debonding detection approach using surface wave measurement with a piezoelectric lead zirconate titanate (PZT) patch as sensor mounted on the outer surface of the CFST member excited with a PZT actuator mounted on the identical surface is proposed in order to avoid embedding PZT-based smart aggregates (SAs) in concrete core. In order to validate the feasibility of the proposed approach and to investigate the effect of interface debonding defect on the surface wave measurement, two rectangular CFST specimens with different degrees of interface debonding defects on three internal surfaces are designed and experimentally studied. Surface stress waves excited by the PZT actuator and propagating along the steel tube of the specimens are measured by the PZT sensors with a pitch and catch pattern. Results show that the surface-mounted PZT sensor measurement is sensitive to the existence of interface debonding defect and the interface debonding defect leads to the increase in the voltage amplitude of surface wave measurement. A damage index defined with the surface wave measurement has a linear relationship with the heights of the interface debonding defects.

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.

Thermography Sequence Processing and Defect Edge Identification of TBC Structure Debonding Defects Detection Using Long-Pulsed Infrared Wave Non-Destructive Testing Technology

General infrared image processing and analysis methods mainly include non uniformity correction, enhancement, noise reduction, segmentation, etc. The handling objects of these algorithms are ordinarily single images, which can improve the display effect of defects in infrared image and increase the signal-to-noise ratio. The active heat source excitation is usually used for defects detection in long pulse infrared thermal wave testing technology, so the collected image sequences are dynamic images. At the same time, as in-homogeneous characteristics of thermal excitation, the detection accuracy of defects is affected. Compared with ordinary infrared images, thermal dynamic image sequence is affected by uneven thermal excitation and wave flow. So the characteristics of the dynamic sequence should be analyzed, in order to get better defect display effect. Using the SVD (singular value decomposition, SVD) method for infrared image sequence reconstruction, and the component of surface temperature signal feature information has been extracted. Compared to the original image, the contrast and signal-to-noise ratio of the reconstructed image has been improved. Canny, LOG and other classical edge detection operators were used to detect the edge of infrared images, and their detection results were compared and analyzed. On the basis of analyzing the effect of the classical edge detection operators on the defect edge recognition in infrared images, a hybrid algorithm for edge detection based on Retinex-watershed-Canny operator is proposed for image edge detection, and the thermal barrier coating structure debonding defects’ edge has been recognized. A large number of useless and untrue boundary information around has been reduced, and the boundary contour of defects is more clear and continuous, which can improve the feature extraction effect of defects. The research work of this paper lay a certain foundation for the quantitative detection of defects.

Experimental research on YSZ TBC structure debonding defect detection using long-pulsed excitation of infrared thermal wave non-destructive testing

Thermal barrier coating structure components are prone to coating cracking, debonding and peeling defects in the service process, which affects the work safety and reliability of the hot end parts, even result to catastrophic consequences. Experimental research on Yttria-stabilized zirconia thermal barrier coating structure debonding defect detection has been conducted using long-pulsed excitation of infrared wave non-destructive testing technology. Differences between surface temperature signals of sound and defective regions, detection effect comparison of heating and cooling process, detection effect comparison of different defect preparation methods, and impact of inspection parameters on detection effect were studied and discussed. The research conclusions will provide technical guidance to Yttria-stabilized zirconia thermal barrier coating structure debonding defects using long-pulsed excitation of infrared wave non-destructive testing technology

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.

Dominance of debonding defect of CFST on PZT sensor response considering the meso-scale structure of concrete with multi-scale simulation

Abstract Piezoelectric-lead-zirconate-titanate(PZT)-based interface debonding defects detection for concrete filled steel tubulars (CFSTs) has been proposed and validated through experiments, and numerical study on its mechanism has been carried out recently by assuming that concrete material is homogenous. However, concrete is composed of coarse and fine aggregates, mortar and interface transition zones (ITZs) and even initial defects and is a typical nonhomogeneous material and its mesoscale structure might affect the wave propagation in the concrete core of CFST members. Therefore, it is significantly important to further investigate the influence of mesoscale structure of concrete on the stress wave propagation and the response of embedded PZT sensor for the interface debonding detection. In this study, multi-physical numerical simulation on the wave propagation and embedded PZT sensor response of rectangular CFST members with numerical concrete core considering the randomness in circular aggregate distribution, and coupled with surface-mounted PZT actuator and embedded PZT sensor is carried out. The effect of randomness in the circular aggregates distribution and the existence of ITZs are discussed. Both a local stress wave propagation behavior including transmission, reflection, and diffraction at the interface between concrete core and steel tube under a pulse signal excitation and a global wave field in the cross-section of the rectangular CFST models without and with interface debonding defects under sweep frequency excitation are simulated. The sensitivity of an evaluation index based on wavelet packet analysis on the embedded PZT sensor response on the variation of mesoscale parameters of concrete core without and with different interface debonding defects under sweep frequency voltage signal is investigated in details. The results show that the effect of the interface debondings on the embedded PZT measurement is dominant when compared to the meso-scale structures of concrete core. This study verified the feasibility of the PZT based debonding detection for rectangular CFST members even the meso-scale structure of concrete core is considered.

Debonding defect detection of metal and composite bonding structures

Metal and composite bonding structures are widely used in many industrial fields. But in the material production and processing and bond- ing process, the adhered surface is not clean, is between the two surface bonding with adhesive is not strict, the existence of gas, dust and other rea- sons, the adhesive structure foaming, deboning, bonding strength decrease- e, durability and reliability reduce etc. In this paper, a kind of typical metal and composite bonding structure was studied by electromagnetic ultrasonic testing. The results show that the results are obvious. The electromagnetic ultrasonic can be used to test the adhesion of metal and composite materials.

Wave propagation simulation and its wavelet package analysis for debonding detection of circular CFST members

In order to investigate the interface debonding defects detection mechanism between steel tube and concrete core of concrete-filled steel tubes (CFSTs), multi-physical fields coupling finite element models constituted of a surface mounted Piezoceramic Lead Zirconate Titanate (PZT) actuator, an embedded PZT sensor and a circular cross section of CFST column are established. The stress wave initiation and propagation induced by the PZT actuator under sinusoidal and sweep frequency excitations are simulated with a two dimensional (2D) plain strain analysis and the difference of stress wave fields close to the interface debonding defect and within the cross section of the CFST members without and with debonding defects are compared in time domain. The linearity and stability of the embedded PZT response under sinusoidal signals with different frequencies and amplitudes are validated. The relationship between the amplitudes of stress wave and the measurement distances in a healthy CFST cross section is also studied. Meanwhile, the responses of PZT sensor under both sinusoidal and sweep frequency excitations are compared and the influence of debonding defect depth and length on the output voltage is also illustrated. The results show the output voltage signal amplitude and head wave arriving time are affected significantly by debonding defects. Moreover, the measurement of PZT sensor is sensitive to the initiation of interface debonding defects. Furthermore, wavelet packet analysis on the voltage signal under sweep frequency excitations is carried out and a normalized wavelet packet energy index (NWPEI) is defined to identify the interfacial debonding. The value of NWPEI attenuates with the increase in the dimension of debonding defects. The results help understand the debonding defects detection mechanism for circular CFST members with PZT technique.

Numerical study on the mechanism of active interfacial debonding detection for rectangular CFSTs based on wavelet packet analysis with piezoceramics

In recent years, Piezoelectric Lead Zirconate Titanate (PZT) based active interfacial debonding defect detection approach for concrete-filled steel tubular (CFST) columns has been proposed and validated experimentally. In order to investigate the mechanism of the PZT based interfacial debonding detection approach, a multi-physics coupling finite element model (FEM) composed of surface-mounted PZT actuator, embedded PZT sensor and a rectangular CFST column is constructed to numerically simulate the stress wave propagation induced by the surface-mounted PZT actuator under different excitation signals with different frequency and amplitude. The measurements of the embedded PZT sensor in concrete core of the CFST columns with different interfacial debonding defect lengths and depths are determined numerically with transient dynamic analysis. The linearity between the PZT response and the input amplitude, the effect of different frequency and measurement distance are discussed and the stress wave fields of CFST members without and with interface debonding defects are compared. Then, the response of the embedded PZT in concrete core is analyzed with wavelet packet analysis. The root mean square deviation (RMSD) of wavelet packet energy spectrum of the PZT measurement is employed as an evaluation index for the interfacial debonding detection. The results showed that the defined index under continuous sinusoidal and sweep frequency signals changes with the interfacial defects length and depth and is capable of effectively identifying the interfacial debonding defect between the concrete core and the steel tubular. Moreover, the index under sweep frequency signal is more sensitive to the interfacial debonding. The simulation results indicate that the interfacial debonding defect leads to the changes in the propagation path, travel time and the magnitude of stress waves. The simulation results meet the findings from the previous experimental study by the authors and help understand the mechanism of interfacial debonding defect detection for CFSTs using PZT technology.

Experimental study on debonding defects detection in thermal barrier coating structure using infrared lock-in thermographic technique

The infrared lock-in thermographic (LT) technique was used to detect debonding defects in ZrO2 coated Ni-based super alloy GH4169 plates. The basic principle of infrared LT technique and the correlated extraction algorithm of thermal wave signal feature was described. Experiments were performed to investigate the influence of the light source output power, number of analysis periods and modulation frequency on the detection results. Results show that, for the given size range of sample defects, greater total phase contrast CPh can be obtained while the light source output power is 1000W, number of analysis periods is 4, and modulation frequency is 0.2Hz, respectively.