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- 实验方案
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Ultrahigh Resolution Pulsed Laser-Induced Photoacoustic Detection of Multi-Scale Damage in CFRP Composites
摘要： This paper presents a photoacoustic non-destructive evaluation (pNDE) system with an ultrahigh resolution for the detection of multi-scale damage in carbon fiber-reinforced plastic (CFRP) composites. The pNDE system consists of three main components: a picosecond pulsed laser-based ultrasonic actuator, an ultrasound receiver, and a data acquisition/computing subsystem. During the operation, high-frequency ultrasound is generated by pulsed laser and recorded by an ultrasound receiver. By implementing a two-dimensional back projection algorithm, pNDE images can be reconstructed from the recorded ultrasound signals to represent the embedded damage. Both potential macroscopic and microscopic damages, such as surface notches and delamination in CFRP, can be identified by examining the reconstructed pNDE images. Three ultrasonic presentation modes including A-scan, B-scan, and C-scan are employed to analyze the recorded signals for the representation of the detected micro-scale damage in two-dimensional and three-dimensional images with a high spatial resolution of up to 60 μm. Macro-scale delamination and transverse ply cracks are clearly visualized, identifying the edges of the damaged area. The results of the study demonstrate that the developed pNDE system provides a non-destructive and robust approach for multi-scale damage detection in composite materials.
关键词： composites,non-destructive testing,photoacoustic,multi-scale,ultrasonic representation,embedded damage
更新于2025-09-19 17:13:59
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Defect Imaging from a Remote Distance by Using Scanning Laser Source Technique with Acoustic Microphones
摘要： Images of defects in plate-like structures can be generated using the scanning laser source (SLS) technique. When a laser Doppler vibrometer (LDV) is used as a receiving device in the SLS technique, images of defects can be obtained through measurements conducted from a distance. Because an LDV cannot receive vibrations reflected from outdoor structures that may have rough surfaces and large fluctuations in a stable manner, this paper discusses an imaging technique using a SLS with acoustic microphones as a receiving device. The results of the experiments that were conducted using various distances between the test plate and microphone showed that the quality of the defect images gradually degraded because of the attenuation of sound in air as the distance increased. Moreover, when the laser beam was reflected back to the microphone after scattering over the plate surface, the laser beam directly generated signals in the microphone due to the photovoltaic effect or alternating heat, preventing the acquisition of defect images. Thereafter, in order to establish remote defect imaging, an acoustic transmitter was connected to the microphone unit. Most of the experimental equipment were located at a remote distance except for the small microphone unit and transmitter. The experimental system enabled the generation of images of the defect in the test plate located at distances of 4 and 6 m.
关键词： non-destructive testing,acoustic transmitter,scanning laser source technique,microphone
更新于2025-09-16 10:30:52
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Design of a remote and integrated Sagnac interferometer that can generate narrowband guided wave through the use of laser and effective optics to detect defects occurred in plates
摘要： To inspect the integrity of specimens that are moving or no space available to mount sensors on their surfaces, laser generated guided wave (GW) becomes the only feasible option. However, conventional GW generated by laser-based emission is in broadband frequency range. Hence, unwanted GW modes, along with the emitted desired GW mode, also get produced simultaneously to the inspected specimen. The results generated from reflected GW become chaotic, making the identification of GW signals truly reflected by defects very difficult. Hence, substantial research efforts have been spent on reducing unwanted GW modes by spatially modulating the laser pattern to emit narrowband GW. Previous methods to generate narrowband GW include the use of slit mask, diffractive grating, lenticular array, and interference of laser beam. Among these techniques, each has certain shortcomings. A recent research achievement is the design of the integrated optical Mach-Zehnder system (IOMZ) (J. Chen et al, Opt. Lett., 42, 4255, 2017). It can emit desired narrowband Lamb wave into the aluminum plate by using pulsed laser and the designed optical system. Although the results showed IOMZ’s ability in emitting narrowband GW mode, significant unwanted noise was also generated, making the signal-to-noise ratio (SNR) of the received GW signals rather low. In this study a new optical system to overcome the shortcoming of the above reported devices is proposed. It is called integrated Sagnac interferometer-based optical system (SIOS) which can minimize generation of unwanted noise and substantially improve the SNR of reflected GW signals. A comparison study is also presented to illustrate the effectiveness of SIOS is superior to that of the IOMZ. Experimental results reveal that the proposed SIOS is promising for remote nondestructive testing and evaluation.
关键词： Non-destructive testing,Laser,Optical systems,Narrowband laser generated ultrasound,Guided wave,Optical Sagnac interferometer
更新于2025-09-12 10:27:22
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Comparison between multi-frequency and multi-speed laser lock-in thermography methods for the evaluation of crack depths in metal
摘要： Two original methods using lock-in thermography with a laser excitation are proposed for the estimation without contact of open crack depths in metal. The first uses a modulated punctual thermal source and is well suited for the study of complicated structures. In the second, a continuous moving thermal source allows to scan homogeneous structures. Each method relies on the heat diffusion modifications induced by a crack located in the thermal diffusion area of the synchronised heat source. The thermal signature of the crack is extracted to the amplitude of surface temperature images for various modulation frequencies or various scanning speeds of the thermal source. The thermal signatures are analysed according to a length representative of the thermal diffusion length to give a local evaluation of the crack depth. The obtained results demonstrate the potentiality of active lock-in thermography as a contactless measurement tool for the evaluation of crack depths up to 3 mm.
关键词： Infrared thermography,crack sizing,non-destructive testing,laser heating,crack depth,lock-in thermography
更新于2025-09-12 10:27:22
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Detection and imaging of local ply angle in carbon fiber reinforced plastics using laser ultrasound and tilt filter processing
摘要： Wrinkles in carbon-fiber reinforced plastics (CFRP) are extremely dangerous, dramatically changing the performance of a composite structure. However, wrinkles are one of the most difficult defects to detect and characterize with ultrasound since they do not produce large echoes like other flaws. Recent developments in laser-ultrasound (LU) have enabled non-contact, high-resolution imaging of CFRPs, providing sub-ply resolution and detailed visualization of CFRP structures. In this paper, we demonstrate that the superior resolution of LU systems can be used to help track ply orientation variations in composites. To improve the signal-to-noise ratio of LU generated signals, we propose a local cross-correlation based tilt-filtration procedure for coherent spatial signal averaging that accounts for the shape of subsequent layers. In addition, local ply angle is a straightforward output of the proposed processing, which can be used directly as an indicator of wrinkle severity.
关键词： D. Non-destructive testing,A. Carbon fibers,B. Directional orientation,D. Ultrasonics
更新于2025-09-11 14:15:04
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Characterizing the Complex Modulus of Asphalt Concrete Using a Scanning Laser Doppler Vibrometer
摘要： Asphalt mixtures are the most common types of pavement material used in the world. Characterizing the mechanical behavior of these complex materials is essential in durable, cost-effective, and sustainable pavement design. One of the important properties of asphalt mixtures is the complex modulus of elasticity. This parameter can be determined using different standardized methods, which are often expensive, complex to perform, and sensitive to the experimental setup. Therefore, recently, there has been considerable interest in developing new, easier, and more comprehensive techniques to investigate the mechanical properties of asphalt. The main objective of this research is to develop an alternative method based on an optical measurement technique (laser Doppler vibrometry). To do this, a frequency domain system identification technique based on analytical formulas (Timoshenko’s beam theory) is used to determine the complex modulus of asphalt concrete at its natural frequencies and to form their master curve. The master curve plotted by this method is compared with the master curve obtained from the standard four-point bending test, and it is concluded that the proposed method is able to produce a master curve similar to the master curve of the standard method. Therefore, the proposed method has the potential to replace the standard stiffness tests. Furthermore, the standard stiffness methods usually conduct experiments up to the maximum frequency of 30 Hz. However, the proposed method can provide accurate complex modulus at high frequencies. This makes an accurate comparison between the properties of the asphalt mixtures in high frequencies and the development of more accurate theoretical models for simulation of specimens possible.
关键词： laser Doppler vibrometry,asphalt mixtures,modal analysis,complex modulus,master curve,non-destructive testing
更新于2025-09-11 14:15:04
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A sensor detecting kissing bonds in adhesively bonded joints using electric time domain reflectometry
摘要： The joining technology with the highest potential in lightweight construction is the adhesive bonding. In an adhesively bonded joint different defects can occur. Alongside gross defects like areas of uncured adhesive and voids, adhesion defects like kissing bonds pose a serious problem to the confidence in these kind of joints in the aircraft industry and other industries. Since kissing bonds are small interfacial defects of as few as nanometers in thickness, the detection by conventional nondestructive testing methods is not possible in most applications. In this paper a novel adhesive sensor based on the electric time domain reflectometry is proposed detecting differences in the deformation of the adherents in an adhesively bonded joint to infer that a kissing bond is taking affect. Numerical calculations are used to show that the proposed sensor principle poses a productive approach. For the numerical calculations a finite difference time domain model is used. The sensor is then validated experimentally by shear tension testing of single lap shear specimens with the adhesive sensor integrated into the joint.
关键词： Kissing bond,Fiber reinforced plastics,Digital image correlation,Non-destructive testing,Adhesively bonded joint,Electric time domain reflectometry
更新于2025-09-10 09:29:36
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AIP Conference Proceedings [AIP Publishing LLC NEW OPERATIONAL TECHNOLOGIES (NEWOT’2015): Proceedings of the 5th International Scientific Conference ?New Operational Technologies? - Tomsk, Russia (29–30 September 2015)] - X-ray microtomographic scanners
摘要： The article studies the operating procedures of an X-ray microtomographic scanner and the module of reconstruction and analysis 3D-image of a test sample in particular. An algorithm for 3D-image reconstruction based on image shadow projections and mathematical methods of the processing are described. Chapter 1 describes the basic principles of X-ray tomography and general procedures of the device developed. Chapters 2 and 3 are devoted to the problem of resources saving by the system during the X-ray tomography procedure, which is achieved by preprocessing of the initial shadow projections. Preprocessing includes background noise removing from the images, which reduces the amount of shadow projections in general and increases the efficiency of the group shadow projections compression. In conclusion, the main applications of X-ray tomography are presented.
关键词： non-destructive testing,shadow projections,3D-image reconstruction,data compression,X-ray microtomography
更新于2025-09-10 09:29:36
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Digitised Frequency Modulated Thermal Wave Imaging for Non-destructive Testing and Evaluation of Glass Fibre Reinforced Polymers
摘要： The active thermal non-destructive testing and evaluation techniques have gained wide acceptance in health monitoring of various solids materials such as metals, composites and semiconductors. The most popular active infrared thermographic methods for non-destructive testing and evaluation applications are pulse based thermography and lock-in thermography techniques. But the usage of these techniques is limited due to their inherent limitations. To overcome the limitations of the existing approaches, the present work demonstrates the effectiveness of digitized frequency modulated thermal wave imaging technique for detection of different shaped defects in a glass fibre reinforced polymer specimen. Further, the usage of post-processing scheme facilitates defect detection with high resolution and also preserves the shape of defects.
关键词： Non-destructive Testing,Thermal waves,Thermal Wave Imaging,Active Infrared Thermography
更新于2025-09-10 09:29:36
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A Quantitative Comparison Among Different Algorithms for Defects Detection on Aluminum with the Pulsed Thermography Technique
摘要： Pulsed thermography is commonly used as a non-destructive technique for evaluating defects within materials and components. In the last few years, many algorithms have been developed with the aim to detect defects and different methods have been used for detecting their size and depth. However, only few works in the literature reported a comparison among the different algorithms in terms of the number of detected defects, the time spent in testing and analysis, and the quantitative evaluation of size and depth. In this work, starting from a pulsed thermographic test carried out on an aluminum specimen with twenty ?at bottom holes of known nominal size and depth, different algorithms have been used with the aim to obtain a comparison among them in terms of signal to background contrast (SBC) and number of detected defects by analyzing different time intervals. Moreover, the correlation between SBC and the aspect ratio of the defects has been investigated. The algorithms used have been: Pulsed Phase Thermography (PPT), Slope, Correlation Coef?cient (R2), Thermal Signal Reconstruction (TSR) and Principal Component Thermography (PCT). The results showed the advantages, disadvantages, and sensitivity of the various thermographic algorithms.
关键词： non-destructive testing,quantitative analysis,pulsed thermography,aluminum
更新于2025-09-10 09:29:36