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Welding of Dissimilar Steel/Al Joints Using Dual-Beam Lasers with Side-by-Side Configuration
摘要： Welding of dissimilar steel/Al lapped joints of 1.5 mm in thickness was carried out by using dual-beam laser welding with side-by-side configuration. The effect of the major process parameters including the dual-beam power ratio of (Rs) and dual-beam distance (d1) on the steel/Al joint characteristics was investigated concerning the weld shape, interface microstructures, tensile resistance and fracture behavior. The results show that dual-beam laser welding with side-by-side configuration produces soundly welded steel/Al lapped joints free of welding defects. The processing parameters of Rs and d1 have a great influence on the weld appearance, the weld penetration in the Al alloy side (P2) and the welding defects. Variation in the depth of the P2 and the locations at the Al/weld interface cause heterogeneous microstructures in the morphology and the thickness of the intermetallic compound (IMC) layers. In addition, electron back scattered diffraction (EBSD) phase mapping reveals that the IMC layer microstructures formed at the Al/weld interface include the needle-like θ-Fe4Al13 phases and compact lath η-Fe2Al5 layers. Some very fine θ-Fe4Al13 and η-Fe2Al5 phases generated along the weld grain boundaries of the steel/Al joints are also confirmed. Finally, there is a matching relationship between the P2 and the tensile resistance of steel/Al joints, and the maximum tensile resistance of 109.2 N/mm is obtained by the steel/Al joints produced at the Rs of 1.50 during dual-beam laser welding with side-by-side configuration. Two fracture path modes have taken place depending on the P2, and relatively high resistance has been achieved for the steel/Al joints with an optimum P2.
关键词： dual-beam laser welding,tensile resistance,side-by-side configuration,EBSD phase mapping,steel/Al joint
更新于2025-11-28 14:24:20
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Laser welding process evaluation on stake-welded T-joints
摘要： Ship structural steel EH36 sheets with thickness of 3 mm were stake-welded with T-joints by using ?ber laser beam welding (LBW). Optical microscope (OM) observation, angular distortion measurement and tensile test were conducted to investigate the in?uence of defocusing distance, welding speed and line energy on the joint properties. The experiment results showed that laser stake-welded T-joints with high quality could be obtained at 1.8 m min?1 speed high, ?5 mm defocusing distance and 5 kW power. The loss of liquid metal in the misalignment condition led to severe under?ll. In addition, laser line energy and misalignment contributed signi?cantly to welding angular distortion. The welding width between face panel and web panel exerted an important in?uence on the tensile properties. Moreover, the thermal distortion process induced by ?ber laser welding has been schematically illustrated and systematically revealed.
关键词： laser welding,angular distortion,tensile property,T-joint,misalignment
更新于2025-11-28 14:24:20
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Autogenous fiber laser welding of 70/30 Cu-Ni alloy plates
摘要： Cupronickel alloys such as 70/30 Cu-Ni have excellent resistance to sea water corrosion and anti-fouling properties, and thus have been widely used for naval and offshore applications. Traditionally, arc welding and brazing processes have been used to weld such materials. In contrast, laser beam welding is a promising technology due to its high productivity, good process flexibility and reliability, and good welding integrity. In the present work, a high power fiber laser system is used to weld 5-mm thick 70/30 Cu-Ni alloy plates in a configuration of butt joints. Then, the laser welded joints are evaluated in terms of microstructures, defects, and mechanical properties (hardness, face and root bend, and tensile) in accordance with the applicable International Organization for Standardization and Defence Standard specifications.
关键词： Tensile Properties,Microstructure,Butt Joint,Cupronickel Alloy,Bend testing,Laser Welding
更新于2025-11-28 14:24:20
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Derivation of space-resolved normal joint spacing and in situ block size distribution data from terrestrial LIDAR point clouds in a rugged Alpine relief (Kühtai, Austria)
摘要： Terrestrial laserscan (TLS) surveys allow the geological investigation of rock slopes, which cannot be measured by direct surveys because of inaccessibility, high hazard potential or excessive effort. The normal joint spacing and the in situ block size distribution are relevant properties for rock mass characterisation but are commonly evaluated statistically or at small regions only. This study presents the jointing characterisation of an Alpine rock slope by both scanline data and a new, automated analysis of point cloud data. The slope, located in the L?ngental (Austria), is characterised by a rugged Alpine relief and granodioritic gneisses fractured by non-persistent joints. The scanline data and the TLS surveys were used to investigate joint set orientations, normal joint spacings and in situ block sizes. Area-wide maps of rock slope properties were prepared from the results of the point cloud analysis. The general results derived from the point clouds are in good agreement with the scanline data. The space-resolved maps show larger block sizes in some of the higher ranging sub-regions and small block sizes in tectonically formed gullies, as well as various local variations. These visualisations are much more beneficial for most rock mechanical questions than common statistical data evaluation approaches using pre-defined sub-regions, which are treated as homogenous areas and thus are missing space-resolved information.
关键词： Point cloud analysis,Terrestrial laserscan,Normal joint spacing,Austria,In situ block size distribution,Joint characterisation
更新于2025-09-23 15:23:52
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Studies on apparatus and method for joining the high-temperature superconducting wires
摘要： High-temperature superconducting wires, such as REBa2Cu3O7-δ (REBCO or RE123, RE: rare-earth elements, δ = 0-1), are composite materials consisting of metals and ceramics. For nuclear magnetic resonance (NMR) and magnetic resonance imaging (MRI) applications, a superconducting connection between wires with high mechanical strength is necessary to realize a persistent-current magnet with required temporal stability of 0.01 ppm/h. However, high-temperature superconducting materials exhibit incongruent melting at high temperature, that is, they separate into a non-superconducting solid and a liquid. The precise temperature control is essential for recovery of the superconducting phase in the joint. In this study, we developed an infrared heating system with a small focal area of about 10×10 mm for heating only the joint part of a 150 mm long sample. A superconducting joint was obtained by applying a temperature gradient through rapid heating from the top of the sample. The details of the system configuration and joining method were described, along with the process of sample preparation.
关键词： joint,superconducting wire,RE123
更新于2025-09-23 15:23:52
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Calcination-free synthesis of high strength self-cleaning anti-reflective MgF2-TiO2 coating
摘要： In order to understand the nonlinear dynamic behavior of a planar mechanism with clearance, the nonlinear dynamic model of the 2-DOF nine-bar mechanism with a revolute clearance is proposed; the dynamic response, phase diagrams, Poincar′e portraits, and largest Lyapunov exponents (LLEs) of mechanism are investigated. The nonlinear dynamic model of 2-DOF nine-bar mechanism containing a revolute clearance is established by using the Lagrange equation. Dynamic response of the slider’s kinematics characteristic, contact force, driving torque, shaft center trajectory, and the penetration depth for 2-DOF nine-bar mechanism are all analyzed. Chaos phenomenon existed in the mechanism has been identi?ed by using the phase diagrams, the Poincar′e portraits, and LLEs. The e?ects of the di?erent clearance sizes, di?erent friction coe?cients, and di?erent driving speeds on dynamic behavior are studied. Bifurcation diagrams with changing clearance value, friction coe?cient, and driving speed are drawn. The research could provide important technical support and theoretical basis for the further study of the nonlinear dynamics of planar mechanism.
关键词： Lyapunov exponent,nonlinear dynamics,chaos,clearance joint,bifurcation
更新于2025-09-23 15:23:52
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Application of the hybrid complex variable method to the analysis of a crack at a piezoelectric-metal interface
摘要： A plane strain problem for an electrically conducting interface crack between linear transversely isotropic piezoelectric and isotropic elastic conductor materials under remote mechanical loading is considered. The attention is focused on a hybrid complex variable method which combines the Stroh formalism for piezoelectric materials with the Muskhelishvili formalism for conducting isotropic elastic materials. This method is illustrated in detail for the open crack model and the contact zone crack model. Using special presentations of mechanical quantities via sectionally analytic functions, a combined Dirichlet–Riemann and Hilbert boundary value problem is formulated and solved analytically. Stress intensity factors as well as the crack tip energy release rate are found in a clear analytical form. Furthermore, transcendental equations for the determination of the realistic contact zone length and the location of the first interpenetration point have been obtained. A significant influence of the external mechanical loading on the crack opening and the stresses as well as the contact zone and interpenetration region lengths is observed. The dependencies of the mentioned values on the intensities of the mechanical loading are presented in tables and associated diagrams.
关键词： electrically conducting interface crack,Piezoelectric-metal joint,contact zone,complex variable method
更新于2025-09-23 15:23:52
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Multi-target joint detection, tracking and classification based on random finite set for aerospace applications
摘要： Multi-target detection, tracking and classification are important problems in aerospace applications, such as reconnaissance, airborne and spaceborne sensing. These problems are correlated but are difficult to be solved simultaneously, especially for systems with multiple sensors. This paper summarized the existing work for multi-target joint detection, tracking and classification based on labeled random finite set. Furthermore, a new algorithm is proposed for multi-sensor multi-target joint detection, tracking and classification problem. A conditional multi-sensor multi-target state estimator is derived, and the optimal solution is then obtained based on the minimum Bayes risk criterion. The numerical simulations are performed, and the results are shown to be more accurate than that of the approximate solutions based on the unlabeled random finite set. It is observed that the labeled random finite set theory provides a good foundation for a joint solution for multi-target detection, tracking and classification.
关键词： Multiple targets,Tracking and classification,Labeled RFS,Generalized bayesian risk,Sensor registration,Joint detection
更新于2025-09-23 15:23:52
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[IEEE 2018 International Conference on Cyberworlds (CW) - Singapore, Singapore (2018.10.3-2018.10.5)] 2018 International Conference on Cyberworlds (CW) - Towards Automatic Optical Inspection of Soldering Defects
摘要： This paper proposes a method for automatic image-based classification of solder joint defects in the context of Automatic Optical Inspection (AOI) of Printed Circuit Boards (PCBs). Machine learning-based approaches are frequently used for image-based inspection. However, a main challenge is to manually create sufficiently large labeled training databases to allow for high accuracy of defect detection. Creating such large training databases is time-consuming, expensive, and often unfeasible in industrial production settings. In order to address this problem, an active learning framework is proposed which starts with only a small labeled subset of training data. The labeled dataset is then enlarged step-by-step by combining K-means clustering with active user input to provide representative samples for the training of an SVM classifier. Evaluations on two databases with insufficient and shifting solder joints samples have shown that the proposed method achieved high accuracy while requiring only minimal user input. The results also demonstrated that the proposed method outperforms random and representative sampling by ~ 3.2% and ~ 2.7%, respectively, and it outperforms the uncertainty sampling method by ~ 0.5%.
关键词： Classification of solder joint defects,active learning,Automatic Optical Inspection (AOI),SVM classifier,K-means
更新于2025-09-23 15:23:52
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A geometric approach for kinematic identification of an industrial robot using a monocular camera
摘要： We propose a generic formulation to identify the kinematic parameters of an industrial robot using a geometric approach when no prior information about the robot’s kinematics is available. The joint axes were estimated using the singular value decomposition applied to the pose data of the robot’s end-effector. These data were obtained by actuating one joint of the robot at a time. The approach is first illustrated using the CAD model of the robot. Next, a simulation study was performed to decide on the number of data points and angular actuation required by a revolute joint to estimate the kinematic parameters. This was done considering the fact that there exist noise in the measurements from the sensors. In this paper, we used a monocular camera mounted on the end-effector of an industrial robot KUKA KR5 Arc as the measurement sensor. We used ArUco Marker maps instead of a single calibration grid to enhance the range of actuation for each joint that was otherwise restricted due to the Field of View of the camera. The robot’s kinematic parameters were then identified using the proposed approach. The identified parameters using the monocular camera were compared with those obtained using other measurement devices, namely, a total station and a laser tracker.
关键词： Kinematic identification,Singular value decomposition,Joint axes vector,Pose measurement,Monocular vision
更新于2025-09-23 15:22:29