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- 2018
- Phase difference method
- UTM
- Crack mouth opening displacement
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- Three point bend specimens
- Prenotched concrete
- Plastic optical fiber
- Optoelectronic Information Science and Engineering
- National Institute of Technology, Warangal
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[IEEE 2018 Days on Diffraction (DD) - St.Petersburg, Russia (2018.6.4-2018.6.8)] 2018 Days on Diffraction (DD) - Semi-analytical hybrid approach for modelling wave motion excited by a piezoelectric transducer in periodic layered composite with a crack
摘要： The paper presents a semi-analytical hybrid approach for modelling the interaction of a piezoelectric transducer and with a periodic elastic structure with a crack. It combines advantages of the frequency domain spectral element method using Gauss–Legendre–Lobatto polynomials and the boundary integral approach. The unknown crack-opening-displacement and the traction vector in the contact area are determined via Galerkin method.
关键词： semi-analytical hybrid approach,frequency domain spectral element method,Galerkin method,periodic elastic structure,boundary integral approach,piezoelectric transducer,crack
更新于2025-09-09 09:28:46
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Correlative optical and X‐ray imaging of strain evolution during Double Torsion Fracture Toughness measurements in shale
摘要： Mode-I Fracture Toughness, KIc, was measured in six shale materials using the double torsion technique. During loading, crack propagation was imaged both using twin optical cameras, and with fast X-Ray radiograph acquisition. Samples of Bowland, Haynesville, Kimmeridge, Mancos, Middlecliff and Whitby shales were tested in a range of orientations. The measured fracture toughness values were found to be in good agreement with existing literature values. The two imaging techniques improve our understanding of local conditions around the fracture tip, through in-situ correlation of mechanical data, inelastic zone size and fracture-tip velocity. The optical Digital Image Correlation (DIC) technique proved useful as a means of determining the validity of individual experiments, by identifying experiments during which strains had developed in the two ”rigid” specimen halves. Strain maps determined through DIC of the optical images suggest that the scale of the inelastic zone is an order of magnitude smaller than the classically used approximation suggests. This smaller damage region suggests a narrower region of enhanced permeability around artificially generated fractures in shales. The resolvable crack-tip was tracked using radiograph data and found to travel at a velocity around 470 m.s?1 during failure, with little variation in speed between materials and orientations. Fracture pathways in the bedding parallel orientations were observed to deviate from linearity, commonly following layer boundaries. This suggests that while a fracture travelling parallel to bedding may travel at a similar speed to a bedding perpendicular fracture, it may have a more tortuous pathway, and therefore access a larger surface area.
关键词： shale materials,fracture tip velocity,Double-torsion fracture toughness,optical digital image correlation,crack-mouth opening displacement,radiograph imaging
更新于2025-09-09 09:28:46
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[IEEE 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - Shanghai (2018.8.8-2018.8.11)] 2018 19th International Conference on Electronic Packaging Technology (ICEPT) - Development of Auto Infrared Photoelastic Microscope for Stress Measurement of Silicon
摘要： Silicon based materials take a great importance in semiconductor and electronics industries. Detecting the cracks and measuring the stress have become increasingly important for electronic packaging. With knowing of the position and the range of stress concentration and crack zone, people can optimize the arrangement before manufacturing or detect the reliability of devices inworking. We introduce an instrument in this paper which is used to measure both stresses and cracks in silicon based materials for electronic packaging. The instrument was built as a microscope (maximum multiple 20) based on infrared photo elasticity. It was built with the function of automatic rotation of optical devices inside the instrument instead the traditional manual rotation which greatly improved the resolution and stability. A micro heating platform (500 ℃max) can be attached for some experiments with temperature requirement such as TSV temperature cycling test. The resolution of stress-birefringence phase difference is less than 2° (calibrated by the quarter wave plate). It can also be used in Si or SiC wafer bonding quality detection, and stress in MEMS can be measured as well.
关键词： stress,Si-based material,crack,microscope,infrared photo elasticity
更新于2025-09-09 09:28:46
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Non-contact fatigue crack detection in civil infrastructure through image overlapping and crack breathing sensing
摘要： Fatigue cracks are of critical structural safety concern in civil infrastructure. Many existing fatigue crack sensing methods are contact-based, hence extensive human operation is necessary for sensor and/or actuator deployment. In this study, we propose a vision-based non-contact approach to detect fatigue cracks through image overlapping. We treat crack breathing behavior, the small cyclic movement of the crack perpendicular to the crack path under repetitive fatigue loads, as a robust indicator for crack identification. The differential image features provoked by a breathing crack can be extracted, enhanced, and visualized through a series of image processing techniques. The performance of the proposed approach is experimentally validated through two laboratory setups including a small-scale steel compact specimen and a large-scale bridge to cross-frame connection specimen. Test results demonstrate the capability of the proposed approach in reliably identifying the fatigue crack, even the true crack is surrounded by other non-crack features.
关键词： Computer vision,Bridges,Civil infrastructure,Feature matching,Non-contact sensing,Image processing,Structural health monitoring,Image registration,Breathing crack,Fatigue crack detection
更新于2025-09-04 15:30:14
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[IEEE 2018 24th International Conference on Pattern Recognition (ICPR) - Beijing, China (2018.8.20-2018.8.24)] 2018 24th International Conference on Pattern Recognition (ICPR) - A Fast Local Analysis by Thresholding applied to image matching
摘要： Keystructures extraction and matching are key steps in computer vision. Many fields of application need large image acquisition and fast extraction of finest structures. In this study, we focus on situations where existing local feature extractors give not enough satisfying results concerning both accuracy and time processing. Among good illustrations, we can quote short-line extraction in local weakly-contrasted images. We propose a new Fast Local Analysis by threSHolding (FLASH) designed to process large images under hard time constraints. We use "micro-line" points as key feature. These are used for shape reconstruction (like lines) and local signature design. We apply FLASH on the field of concrete infrastructure monitoring where robots and UAVs are more and more used for automated defect detection (like cracks). For large concrete surfaces, there are several hard constraints such as the computational time and the reliability. Results show us that the computations are faster than several existing algorithms in image matching and FLASH has invariance to rotation, partial occlusion, and scale range from 0.7 to 1.4 without scale-space exploration.
关键词： concrete infrastructure monitoring,crack detection,computer vision,feature extraction,FLASH,image matching
更新于2025-09-04 15:30:14
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Superwide-Range Fiber Bragg Grating Displacement Sensor Based on an Eccentric Gear: Principles and Experiments
摘要： Aiming at the large displacement monitoring needs of slope, road, and bridge engineering, a new method concerning the superwide-range fiber Bragg grating (FBG) displacement sensor based on eccentric gear was investigated. The structure of the sensor was designed and the formula for the wavelength-displacement relationship was established via waveform fitting from calibration tests. The lateral displacement of a first-story shear wall was successfully monitored in a hysteresis test of a steel frame–reinforced concrete infill wall. A FBG relative displacement sensor was developed refitting a superwide-range fiber Bragg grating displacement sensor based on eccentric gear. The refitted sensor was applied in a self-repairing performance test of a shape memory alloy (SMA) strengthened concrete beam. The monitoring results of the crack were compared with the results of an integrated test instrument, and the results showed that the sensor exhibited very good accuracy. The innovative FBG displacement sensor has a low influence on the structure, strong practicability, and good prospects for engineering applications.
关键词： Crack measurement,Fiber Bragg grating (FBG),Superwide-range displacement monitoring,Eccentric gear,Displacement sensor
更新于2025-09-04 15:30:14
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Foreground–background separation technique for crack detection
摘要： Current level-2 condition assessment methods for critical infrastructure assets mostly rely on human visual investigation of visible damages and patterns at the structure surface, which can be a costly, time-consuming, and subjective exercise in reality. In this article, a novel method for crack detection is proposed via salient structure extraction from textured background. This method first extracts strong edges and distinguishes them from strong textures in a local neighborhood. Then, the spatial distribution of texture features is estimated to detect cracks as salient structures that are not widely spread across the whole image. The outputs from these two key steps are fused to calculate the final structure saliency map for generation of the crack masks. This method was validated on a data set with 704 images and the outcome revealed an average f-measure of 75% in detecting the concrete cracks that is significantly higher than two other baseline methods.
关键词： salient structure extraction,crack detection,foreground-background separation,textured background,image processing
更新于2025-09-04 15:30:14
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[IEEE 2018 IEEE 38th International Conference on Electronics and Nanotechnology (ELNANO) - Kiev (2018.4.24-2018.4.26)] 2018 IEEE 38th International Conference on Electronics and Nanotechnology (ELNANO) - Study of Parametric Transducer Operation in Pulsed Eddy Current Non-Destructive Testing
摘要： In this article is considered the experimental results of the using the parametric type of an eddy current transducer at two excitation modes - pulsed and harmonic. The flat samples from aluminum alloy and steel with artificial crack-like defects on them were selected as testing objects. The estimation of the amplitude, decrement and natural oscillation frequency of the eddy current transducer signal as informative parameters was performed according to the analysis of experimental signals of the parametric transducer. The results of the comparative analysis of the eddy current transducer signals at harmonic and pulsed excitation are presented by estimating of changes in the signals amplitude values from the crack depth in the testing object. It is shown that the signals of parametric eddy current transducer in the form of damped harmonic oscillations obtained by pulse excitation of the transducer can be used in the eddy current non-destructive testing to estimate the depth of surface cracks. The types of the dependences of the attenuation and the natural oscillation frequency of the eddy current transducer signal from the change in the crack depth in the testing object were established using the experimental data. The analysis of the sensitivities of the informational parameters of the eddy current transducer at pulsed excitation to the crack depth in the testing objects is performed.
关键词： decrement,harmonic excitation,crack depth,frequency,pulse eddy current,pulsed excitation,parametric type eddy current transducer
更新于2025-09-04 15:30:14