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过滤筛选
- 2018
- Phase difference method
- UTM
- Crack mouth opening displacement
- FBGs
- Three point bend specimens
- Prenotched concrete
- Plastic optical fiber
- Optoelectronic Information Science and Engineering
- National Institute of Technology, Warangal
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Multichannel fiber laser acoustic emission sensor system for crack detection and location in accelerated fatigue testing of aluminum panels
摘要： Detection and location of the source of acoustic emission in a thin aluminum panel is demonstrated using a multichannel fiber laser sensor system. Acoustic emission generated by a crack in an aluminum panel used as a test coupon in an accelerated fatigue experiment is detected and the location of the crack identified. Acoustic emission is detected over a bandwidth of around 0.5 MHz from a serially multiplexed array of four laser sensors and compared with measurements taken from four piezo-electric sensors co-located with the fiber laser sensors. The location of the crack is determined by first estimating time difference of arrival of signals at each sensor using a novel algorithm based on the cumulative distribution transform method with hyperbolic positioning. The fiber laser sensor is shown to match the signal-to-noise ratio of the industry standard (Mistras S9225) piezo-electric acoustic emission sensor.
关键词： location,crack detection,fiber laser,acoustic emission,accelerated fatigue testing
更新于2025-09-23 15:21:01
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Study on high-efficiency separation of laminated glass by skillfully combining laser-induced thermal-crack propagation and laser thermal melting
摘要： Laminated glass has a wide range of applications, but the cutting process is too cumbersome. In this paper, a novel laser composite separation method was proposed to separate the laminated glass by one time and simplify the cutting process from five steps to two steps for the first time by skillfully combining laser-induced thermal-crack propagation and laser thermal melting. This method generated three laser foci, and each laser focus is acting on one layer of laminated glass. Then, the composite mechanism combining laser-induced thermal-crack propagation for glass layers and laser thermal melting separation for PVB layer was realized to separate entire laminated glass. The experiments of separating laminated glass with thickness of 5 + 0.38 + 5 mm were carried out by laser composite separation successfully, and the separation side wall was very smooth (roughness of glass layer reached 10.24 nm) without any separation defects such as chipping, micro-cracks or subsurface damage. A mathematical model was also established to analyze the separation mechanism.
关键词： Laser melting,Numerical simulation,Laser-induced thermal-crack propagation,Laser separation,Laminated glass
更新于2025-09-23 15:21:01
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Rapid detection of building cracks based on image processing technology with double square artificial marks
摘要： In order to measure the crack width of dangerous buildings quickly and accurately, this article presents a new crack width measurement method, which is based on image processing technology, using double square artificial markers to identify building cracks and calculate crack width. It makes two 10 mm 3 10 mm black square artificial marks and places them near the sides of the crack. Then it uses a camera to collect crack images and transfer photos to a computer. The crack image is subjected to image graying, binarization, denoising, image segmentation, and pixel calibration based on the image processing technique. Finally, the actual length value of the unit pixel is calculated. Then it can calculate the actual width of the crack according to the number of pixels included in the test crack. The calculation results show that the accuracy of the proposed method is 98.56% compared with the measured data. The calculation method can accurately and effectively detect the crack width of dangerous buildings and improve work efficiency. At the same time, it can avoid long hours of work in dangerous operating environments.
关键词： building cracks,digital image processing,safety,MATLAB,double square artificial marks,crack width
更新于2025-09-23 15:21:01
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Drying-induced soil shrinkage and desiccation cracking monitoring with distributed optical fiber sensing technique
摘要： Monitoring of drying-induced volume shrinkage and desiccation cracking in clayey soils is of great importance in geological and geotechnical engineering. Compared with conventional strain monitoring methods providing discrete measurements, the Brilliouin optical time domain reflectometer (BOTDR) technique enables continuous measurement of the distributed strain generated along optical fibers. In this study, a physical model test is conducted to investigate the feasibility of monitoring drying-induced soil shrinkage and desiccation cracking using BOTDR. Three optical fibers with different surface protections (thermoplastic polyester elastomer (TPEE) jacket, nylon jacket, and acrylate coating) are tested and compared. Experimental results validate that BOTDR is applicable for the direct strain monitoring of desiccation cracking soils. Monitored strain values are strongly influenced by water content, soil cracking, and fiber types. The strain measured by the optical fiber reaches only several micro strains when the soil is over-saturated, gradually increases with the decreasing water content and the increasing soil-fiber interfacial shear stresses, and drops rapidly after the occurrence of decoupling between fiber and soil resulting from the mature development of desiccation cracks. The optical fiber with acrylate coating is not suitable because of its fragility and the poor interfacial coupling with the soil. Optical fibers covered with TPEE jacket or nylon jacket are both applicable for soil strain monitoring, with the former one more sensitive to water content variations. The study is the first attempt to apply the BOTDR technique for the direct and continuous monitoring of drying-induced soil shrinkage and desiccation cracking process. It is expected bring new insights into the fundamental understanding of volumetric shrinkage and desiccation cracking in clayey soils.
关键词： Brilliouin optical time domain reflectometer (BOTDR),Desiccation crack,Volumetric shrinkage,Strain monitoring,Optical fiber sensing
更新于2025-09-23 15:21:01
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[Lecture Notes in Computer Science] Pattern Recognition and Computer Vision Volume 11256 (First Chinese Conference, PRCV 2018, Guangzhou, China, November 23-26, 2018, Proceedings, Part I) || Robust Crack Defect Detection in Inhomogeneously Textured Surface of Near Infrared Images
摘要： Robust crack defect detection in solar cells has been challenging because of the inhomogeneously textured surface, low contrast between crack defect and background, the diversity of crack types, and so on. To overcome these challenges, this paper presents a new robust crack defect detection scheme for multicrystalline solar cells. Firstly, a steerable evidence ?lter is designed to process EL image to obtain the response map, which enhances the contrast between crack and background and provides evidence for the presence of crack defect. Secondly, complete crack extraction from the response map is employed. Finally, the complete crack can be located in the inspection image by the crack skeleton extraction. Experimental results on defective and defect-free EL images show that the proposed scheme is robust, and various cracks can be effectively detected, which outperforms the previous methods.
关键词： Crack defect,Inhomogeneous texture,Steerable evidence ?lter
更新于2025-09-23 15:21:01
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Study on Needles and Cracks of Tin-doped Indium Oxide Tablets for Electron Beam Evaporation Process
摘要： Tin-doped indium oxide (ITO) tablets were used to deposit ITO films on p-GaN layer of light-emitting diodes. Needles and cracks in ITO tablets generated during electron beam evaporation process were deeply investigated. The formation of needles is predominantly resulted from the scanning trace, which is controlled by x and y axes scanning singles. The needles can be eliminated by controlling electron beam scanning trace. The loose microstructure with uniform grains and pores in the ITO tablets results in weak bonding strength, which leads to cracks under the thermal shock of high energy electron beam. A three-dimensional reticulated skeleton structure with strong bonding strength can restrain these cracks.
关键词： needle,crack,ITO,electron beam evaporation
更新于2025-09-23 15:21:01
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On the application of laser shock peening for retardation of surface fatigue cracks in laser beam-welded AA6056
摘要： The present study aims to investigate the extent to which the fatigue behaviour of laser beam-welded AA6056-T6 butt joints with an already existing crack can be improved through the application of laser shock peening. Ultrasonic testing was utilized for in situ (nondestructive) measurement of fatigue crack growth during the fatigue test. This procedure allowed the preparation of welded specimens with surface fatigue cracks with a depth of approximately 1.2 mm. The precracked specimens showed a 20% reduction in the fatigue limit compared with specimens without cracks in the as-welded condition. Through the application of laser shock peening on the surfaces of the precracked specimens, it was possible to recover the fatigue life to the level of the specimens tested in the as-welded condition. The results of this study show that laser shock peening is a very promising technique to recover the fatigue life of welded joints with surface cracks, which can be detected by nondestructive testing.
关键词： fatigue crack,aluminium alloys,laser beam welding,ultrasonic crack tip diffraction,residual stress,laser shock peening
更新于2025-09-23 15:19:57
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Bionic Repair of Thermal Fatigue Cracks in Ductile Iron by Laser Melting with Different Laser Parameters
摘要： Nodular iron brake discs typically fail due to serious thermal fatigue cracking, and the presence of graphite complicates the repair of crack defects in ductile iron. This study presents a novel method for remanufacturing ductile iron brake discs based on coupled bionics to repair thermal fatigue cracks discontinuously using bio-inspired crack blocking units fabricated by laser remelting at various laser energy inputs. Then, the ultimate tensile force and thermal fatigue crack resistance of the obtained units were tested. The microhardness, microstructure, and phases of the units were characterized using a digital microhardness meter, optical microscopy, scanning electron microscopy, and X-ray di?raction. It was found that the units without defects positively impacted both the thermal fatigue resistance and tensile strength. The unit fabricated at a laser energy of 165.6+19?15 J/mm2 had su?cient depth to fully close the crack, and exhibited superior anti-cracking and tensile properties. When the unit distance is 3 mm, the sample has excellent thermal fatigue resistance. In addition, the anti-crack mechanism of the units was analysed.
关键词： bionic crack blocked unit,repair discontinuously,thermal fatigue crack,ductile iron,laser remelting
更新于2025-09-23 15:19:57
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Concrete Crack Monitoring Using a Novel Strain Transfer Model for Distributed Fiber Optics Sensors
摘要： In this paper, we study the strain transfer mechanism between a host material and an optical fiber. A new analytical model handling imperfect bonding between layers is proposed. A general expression of the crack-induced strain transfer from fractured concrete material to optical fiber is established in the case of a multilayer system. This new strain transfer model is examined through performing wedge splitting tests on concrete specimens instrumented with embedded and surface-mounted fiber optic cables. The experimental results showed the validity of the crack-induced strain expression fitted to the distributed strains measured using an Optical Backscattering Reflectometry (OBR) system. As a result, precise estimations of the crack openings next to the optical cable location were achieved, as well as the monitoring of the optical cable response through following the strain lag parameter.
关键词： crack,distributed strains,crack opening,wedge splitting test,fiber optics sensors,strain transfer,imperfect bonding,concrete
更新于2025-09-23 15:19:57
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Deep learning-based roadway crack classification using laser-scanned range images: A comparative study on hyperparameter selection
摘要： In recent years, deep learning-based crack detection methods have been widely explored and applied due to their high versatility and adaptability. In civil engineering applications, recent research on crack detection through deep convolutional neural network (DCNN) includes road pavement crack detection, bridge inspection, defects detection in shield tunnel lining, etc. Despite the increasing popularity of DCNN on crack detection, many challenges have yet to be properly addressed. For crack detection using three-dimensional (3D) range (i.e., elevation) images, disturbances such as surface variation can negatively affect the detection performance. Besides, some typical non-crack patterns such as grooves can be easily misidentified as cracks, i.e., false positives. Another issue lies in the selection of hyperparameters related with the design of a DCNN architecture. For example, the hyperparameters which are related with network structure (e.g., kernel size, network depth and width) and training (e.g., mini-batch size and learning rate) can impact the network performance to a significant extent. Therefore, they need to be properly determined for optimal performance. However, for deep learning-based roadway crack classification using laser-scanned range images, a comprehensive discussion on the hyperparameter selection/tuning has not been thoroughly performed. This study develops a hyperparameter selection process involving a series of experiments on laser-scanned range images with high diversities, investigating the optimal joint hyperparameter configuration on network structure and training for DCNN-based roadway crack classification. In a comparative study, 36 DCNN architectures with varying layouts are developed for crack classification. These architecture candidates differ in kernel sizes (e.g., 3 × 3, 7 × 7, and 11 × 11), network depths (from 5 to 8 weight layers), and widths (from 16 to 96 kernels in each convolutional layer). The 7-layer DCNN with constant 7 × 7 kernels and increasing network widths yields the highest classification performance among the proposed 36 DCNN classifiers, which may be because it can best reflect the complexity of the acquired laser-scanned roadway range images. Once the optimal architecture layout is determined, further discussion on the selection of min-batch sizes, learning rates, dropout factor and leaky rectified linear unit (LReLU) factor is performed. Experimental results show the optimal architecture with associated training configuration can achieve consistent and accurate performance, under the contamination of surface variations and grooved patterns in laser-scanned range images. Discussion on the hyperparameter selection can provide insights for the development of DCNN in similar applications using laser-scanned range images.
关键词： Roadway crack,Groove,Laser-scanned range image,Hyperparameter selection,Deep convolutional neural network
更新于2025-09-23 15:19:57