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Development of technology for robotic laser welding of thin-walled products from heat-resistant alloys
摘要： The results of testing the modes of robotic laser welding of spatial welded joints of thin-walled products from heat-resistant steels are considered. Comparative studies of the influence of the parameters of various methods of industrial welding on the metallography of the weld and the technological strength of the welded joint are presented. The resistance of welded joints against the formation of crystallization (hot) cracks is evaluated.
关键词： heat-resistant alloys,robotic laser welding,technological strength,metallography,crystallization cracks,thin-walled products
更新于2025-09-23 15:19:57
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Fatigue behavior improvements of laser-induction hybrid welded S690QL steel plates
摘要： In this paper, the improvements of fatigue performances of S690QL steel welded by laser-induction hybrid welding (LIHW) method were performed, mainly through the infrared imaging device to obtain the weld thermal cycle, fatigue machine to test the fatigue strength and scanning electron microscope to observe the fracture morphology. In fatigue tests, tension-tension fatigue loading and stress ratio R = 0.1 was selected. The LIHW fitted S-N curves were derived. It was found that the cracks with symmetrical grooves were initiated at the weld center (WC), while the single-laser welding (SLW) fatigue samples were fractured at the WC. However, the LIHW samples were finally fractured near heat-affected zone (HAZ). The fracture morphology of fatigue samples with stress amplitude of 108 MPa and 144 MPa were further selected to analysis. Due to different degree of defects or stress concentration, and different welding heat input absorption ability and cooling rate, in sudden fracture region, SLW fatigue samples mainly contained the brittle transient failure mode, LIHW fatigue samples mainly showed a ductile failure mode. It can thus be concluded that the LIHW method could improve the fatigue performance of S690QL steel joints.
关键词： Transient failure mode,Single-laser welding,Cracks,Laser-induction hybrid welding,Fatigue strength
更新于2025-09-23 15:19:57
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Weld cracks nondestructive testing based on magneto-optical imaging under alternating magnetic field excitation
摘要： This paper researches the magneto-optical (MO) imaging law of weld cracks under alternating magnetic field excitation. Weld surface and subsurface cracks are detected by a MO sensor, and the relationship between the MO images' characteristics and the magnetic field strength is analyzed based on the Faraday MO effect. A magnetic dipole model is proposed to study the magnetic field distribution over the weld crack. A finite element analysis (FEA) model of the weld crack is established, and the relationship between the magnetic flux leakage signal and the crack width is analyzed, which is useful for identifying cracks either on the surface or on the subsurface of the weld. A MO imaging nondestructive testing (NDT) experiment is carried out to detect weld cracks under alternating magnetic field excitation, and the difference among weld cracks is obtained by analyzing the gray values of the weld cracks' MO images. Research results show that the magnetic flux leakage signals of weld surface and subsurface cracks can be clearly distinguished, the magnetic field intensity of the surface cracks is larger than that of the subsurface cracks at the same width, and the MO image of the weld cracks can reflect the intensity of the magnetic field through varied brightness, that is, the gray value of the MO image can match the corresponding magnetic field intensity.
关键词： Weld cracks,Nondestructive testing,Faraday MO effect,Magneto-optic systems
更新于2025-09-19 17:15:36
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Microchannel fabrication and metallurgical characterization on titanium by nanosecond fiber laser micromilling
摘要： Laser micromilling technique is used to manufacture microchannel on metals and nonmetals. Microfeatures ≤100 μm are still challenging for fabrication by common methods. Nanosecond fiber laser micromachining has become more popular owing to its prospective implementation in laser micromilling. Microchannel application relies on its geometric dimension, profile, and surface quality. In this study, an attempt was made to explore the impact of process parameters scanning times, scanning velocity, pulse repetition rate, and assist gas pressure on top kerf width, taper, surface roughness, and metal removal rate in laser micromilling experimentally. Microchannel width varied between 45.5 and 70.9 μm. A regression model has been developed for each response. ANOVA (analysis of variance) has been carried out to remove insignificant parameters. Thermal stress analyzed by surface cracks inside microchannel by Scanning Electrone Microscopy (SEM) images. Higher PRR, lower no. of scans, higher scanning speed and high air pressure found suitable for lesser surface cracks. Redeposition observed at slower scanning velocity and minimum scanning times. Oxidation zone from boundary of channel varies between 37 and 58 μm. Oxide formed on Ti surface which increases oxygen content toward center of channel from 51.08 to 76.22% compared to outside surroundings.
关键词： oxidized zone,MRR,kerf width,LMM,surface cracks,taper,surface roughness,recast layer
更新于2025-09-19 17:13:59
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[IEEE 2019 IEEE International Conference on Big Knowledge (ICBK) - Beijing, China (2019.11.10-2019.11.11)] 2019 IEEE International Conference on Big Knowledge (ICBK) - U-Net Based Defects Inspection in Photovoltaic Electroluminecscence Images
摘要： Efficient defects segmentation from photovoltaic (PV) electroluminescence (EL) images is a crucial process due to the random inhomogeneous background and unbalanced crack non-crack pixel distribution. The automatic defect inspection of solar cells greatly influences the quality of photovoltaic cells, so it is necessary to examine defects efficiently and accurately. In this paper we propose a novel end to end deep learning-based architecture for defects segmentation. In the proposed architecture we introduce a novel global attention to extract rich context information. Further, we modified the U-net by adding dilated convolution at both encoder and decoder side with skip connections from early layers to later layers at encoder side. Then the proposed global attention is incorporated into the modified U-net. The model is trained and tested on Photovoltaic electroluminescence 512x512 images dataset and the results are recorded using mean Intersection over union (IOU). In experiments, we reported the results and made comparison between the proposed model and other state of the art methods. The mean IOU of proposed method is 0.6477 with pixel accuracy 0.9738 which is better than the state-of-the-art methods. We demonstrate that the proposed method can give effective results with smaller dataset and is computationally efficient.
关键词： cracks detection,electroluminescence images,U-net,Solar cell defects detection
更新于2025-09-16 10:30:52
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Solar cells micro crack detection technique using state-of-the-art electroluminescence imaging
摘要： In this article, we present the development of novel technique that is used to enhance the detection of micro cracks in solar cells. Initially, the output image of a conventional electroluminescence (EL) system is determined and reprocessed using a binary and discreet Fourier transform (DFT) image processing models. The binary image is used to enhance the detection of the cracks size, position and orientation, principally using the geometric properties of the EL image. On the other hand, the DFT has been used to analyse the EL image in two-dimensional spectrum. The output image of the DFT consists of structures of all required frequencies, hence, improve the detection of possible cracks presents in the solar cell. As a result, the developed technique improves the detection of micro cracks in solar cells compared to conventional EL output images.
关键词： Photovoltaics,Micro cracks,EL imaging,Solar cells
更新于2025-09-12 10:27:22
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Ultra-Fast High-Resolution Solar Cell Cracks Detection Process
摘要： This paper presents the advancement of an ultra-fast high-resolution cracks detection in solar cells manufacturing system. The aim of the developed process is to (i) improve the quality of the calibrated image taken by a low-cost conventional electroluminescent (EL) imaging setup, (ii) proposing a novel methodology to enhance the speed of the detection of the solar cell cracks, and finally (iii) develop a proper procedure to decide whether to accept or reject the solar cell due to the existence of the cracks. The proposed detection process has been validated on various cracked/free-crack solar cell samples, evidently it was found that the cracks type, size and orientation are more visible using the proposes method, while the speed of calibrating the EL images are in the range of 0.1s to 0.3s, excluding the EL imaging time.
关键词： Solar cells,Micro cracks,Electroluminescence,Photovoltaic
更新于2025-09-12 10:27:22
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Prediction of quality characteristics of laser drilled holes using artificial intelligence techniques
摘要： Micro-drilling using lasers finds widespread industrial applications in aerospace, automobile, and bio-medical sectors for obtaining holes of precise geometric quality with crack-free surfaces. In order to achieve holes of desired quality on hard-to-machine materials in an economical manner, computational intelligence approaches are being used for accurate prediction of performance measures in drilling process. In the present study, pulsed millisecond Nd:YAG laser is used for micro drilling of titanium alloy and stainless steel under identical machining conditions by varying the process parameters such as current, pulse width, pulse frequency, and gas pressure at different levels. Artificial intelligence techniques such as adaptive neuro-fuzzy inference system (ANFIS) and multi gene genetic programming (MGGP) are used to predict the performance measures, e.g. circularity at entry and exit, heat affected zone, spatter area and taper. Seventy percent of the experimental data constitutes the training set whereas remaining thirty percent data is used as testing set. The results indicate that root mean square error (RMSE) for testing data set lies in the range of 8.17–24.17% and 4.04–18.34% for ANFIS model MGGP model, respectively, when drilling is carried out on titanium alloy work piece. Similarly, RMSE for testing data set lies in the range of 13.08–20.45% and 6.35–10.74% for ANFIS and MGGP model, respectively, for stainless steel work piece. Comparative analysis of both ANFIS and MGGP models suggests that MGGP predicts the performance measures in a superior manner in laser drilling operation and can be potentially applied for accurate prediction of machining output.
关键词： Laser drilling,ANFIS,Genetic programming,Stainless steel,Artificial intelligence,Ti6Al4V,Surface cracks
更新于2025-09-12 10:27:22
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Modulation of the local grain structure in laser beam welds to inhibit the propagation of centerline hot cracks
摘要： The morphology and the size of the grains of a weld result from the solidification rate and the temperature gradient during solidification. The heat input and the velocity of the welding process directly affect these quantities. The laser power, the welding velocity and the beam diameter were periodically modulated to achieve a periodical change of the solidification conditions during welding. It leads to a continuous change of the type of grain structure over the welded length. The metallographic analysis of welds in close edge position shows the periodical interruption of centerline cracks at local changes of the grain structure.
关键词： Laser Beam Welding,Grain Structure,Aluminum Alloys,Hot cracks
更新于2025-09-12 10:27:22
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Techniques for Evaluating the Depth of a Crack by Means of Laser Spot Thermography
摘要： Laser Spot Thermography is a useful tool in nondestructive crack detection. Our goal is to estimate the depth of a fracture from external thermal measurements. First we transform a set of real 3D data in a 2D effective one. Then we use the 2D data set as input in different methods for solving an inverse problems for the heat equation. Our guiding idea is that an effort in the direction of the mathematical analysis of the problem, rewards us in term of computational costs.
关键词： laser-spot thermography,cracks,inverse problems
更新于2025-09-11 14:15:04