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A statistical learning method for image-based monitoring of the plume signature in laser powder bed fusion
摘要： The industrial breakthrough of metal additive manufacturing processes mainly involves highly regulated sectors, e.g., aerospace and healthcare, where both part and process qualification are of paramount importance. Because of this, there is an increasing interest for in-situ monitoring tools able to detect process defects and unstable states since their onset stage during the process itself. In-situ measured quantities can be regarded as “signatures” of the process behaviour and proxies of the final part quality. This study relies on the idea that the by-products of laser powder bed fusion (LPBF) can be used as process signatures to design and implement statistical monitoring methods. In particular, this paper proposes a methodology to monitor the LPBF process via in-situ infrared (IR) video imaging of the plume formed by material evaporation and heating of the surrounding gas. The aspect of the plume naturally changes from one frame to another following the natural dynamics of the process: this yields a multimodal pattern of the plume descriptors that limits the effectiveness of traditional statistical monitoring techniques. To cope with this, a nonparametric control charting scheme is proposed, called K-chart, which allows adapting the alarm threshold to the dynamically varying patterns of the monitored data. A real case study in LPBF of zinc powder is presented to demonstrate the capability of detecting the onset of unstable conditions in the presence of a material that, despite being particularly interesting for biomedical applications, imposes quality challenges in LPBF because of its low melting and boiling points. A comparison analysis is presented to highlight the benefits provided by the proposed approach against competitor methods.
关键词： Process plume,Metal additive manufacturing,Laser powder bed fusion,Infrared imaging,In-situ monitoring,Zinc
更新于2025-11-28 14:24:20
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Development of an Intra-Layer Adaptive Toolpath Generation Control Procedure in the Laser Metal Wire Deposition Process
摘要： Recently developed concentric laser metal wire deposition (LMWD) heads allow metal addition processes which are independent of the deposition direction, thus enabling complex paths to be generated. The sensitivity of the process to height deviations has experimentally been observed to be greater with this type of head than with powder ones, therefore requiring more precise and local process control algorithms to be implemented. This work developed a methodology for measuring the part, layer by layer, using a 3D scanner based on structured laser light. Height corrections were applied to the mean and intra-layer height deviations by recalculating the deposition trajectories of the next layer to be deposited. Local height deviations were adjusted by varying the scanning speed, thus increasing the feed rate in the lower areas and decreasing it in the higher ones. Defects generated in the purpose, with height differences within the layer, were successfully corrected. A flat layer was re-established through the application of the control strategy. The internal integrity of the parts due to the scanning speed variation was analyzed, resulting in fully dense parts. The structured light measurement and height correction systems are found to be an affordable and time-efficient solution that can be integrated into an LMWD environment, thereby improving the process robustness.
关键词： cladding,coaxial wire feed,metal wire,additive manufacturing,monitoring,laser deposition,structured light scanning,height control
更新于2025-11-28 14:24:20
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Inconel625/316L functionally graded material using spectral diagnostics during laser additive manufacturing process
摘要： In this paper, the composition of Inconel625/316L functionally graded material during the additive manufacturing process was monitored on-line by laser-induced plasma optical emission spectroscopy. Several spectral lines are used to establish the quantitative relationship between relative intensity, relative intensity ratio, plasma temperature, and functional gradient material composition variation. It is shown that the change between relative strength and compositional content is similar to actual expectations. But, the relationship between the relative intensity with Inconel625 content is nonlinear. Cr-I/Ni-I relative intensity ratios almost linearly decrease with increasing Inconel625 content. The linear correlation coe?cient of the best ?tted curve was 0.943, and the maximum percentage error was 7.5%. The plasma temperature was obtained by the Boltzmann plot using ?ve neutral chrome lines between 330 and 380 nm. Plasma temperature almost linearly increases with increasing Inconel625 content in a range. The linear correlation coe?cient of the plasma temperature ?tted straight line was 0.93, and the maximum percentage error was 2.7%. The feasibility of composition monitoring of gradient materials by spectral information during the additive manufacturing process was veri?ed.
关键词： plasma temperature,spectral diagnosis,laser additive manufacturing,composition monitoring
更新于2025-11-28 14:24:20
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Hyperspectral and thermal temperature estimation during laser cladding
摘要： Although there is no doubt about the tremendous industrial potential of metal additive manufacturing techniques such as laser metal deposition, the technology still has some intrinsic quality challenges to overcome before reaching its industrial maturity. Noncontact in situ monitoring of the temperature evolution of the workpiece could provide the necessary information to implement an automated closed-loop process control system and optimize the manufacturing process, providing a robust solution to these issues. However, measuring absolute temperatures is not self-evident: wavelength-dependent emissivity values vary between solid, liquid, and mushy metallic regions, requiring spectral information and dedicated postprocessing to relate the amount of emitted infrared radiation to the material temperature. This paper compares the temperature estimation results obtained from a visible and near-infrared hyperspectral line camera and a conventional short-wave infrared (SWIR) thermal camera during the laser melting and cladding of a 316L steel sample. Both methods show agreeing results for the temperature distribution inside the melt pool, with the SWIR camera extending the temperature measurements beyond the melt pool boundaries into the solid region.
关键词： temperature estimation,laser cladding,hyperspectral imaging,additive manufacturing,thermal monitoring
更新于2025-11-28 14:24:20
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Refractive Index Measurement of Lithium Ion Battery Electrolyte with Etched Surface Cladding Waveguide Bragg Gratings and Cell Electrode State Monitoring by Optical Strain Sensors
摘要： In this scientific publication, a new sensor approach for status monitoring, such as state of charge and state of health, of lithium ion batteries by using special Bragg gratings inscribed into standard optical glass fibers is presented. In addition to well-known core gratings, embedded into the anode of 5 Ah lithium ion pouch cells as a strain monitoring unit, the manufacturing of a surface cladding waveguide Bragg grating sensor incorporated into the cell’s separator, that is sensitive to changes of the refractive index of the surrounding medium, is demonstrated. On the basis of the experiments carried out, characteristics of the cell behavior during standard cyclization and recognizable marks in subsequent post-mortem analyses of the cell components are shown. No negative influence on the cell performance due to the integrated sensors have been observed; however, the results show a clear correlation between fading cell capacity and changes of the interior optical signals. Additionally, with the novel photonic sensor, variations in the electrolyte characteristics are determinable as the refractive index of the solution changes at different molar compositions. Furthermore, with the manufactured battery cells, abuse tests by overcharging were conducted, and it was thereby demonstrated how internal battery sensors can derive additional information beyond conventional battery management systems to feasibly prevent catastrophic cell failures. The result of the research work is an early stage photonic sensor that combines chemical, mechanical and thermal information from inside the cell for an enhanced battery status analysis.
关键词： lithium ion,battery aging,cladding waveguide,battery electrolyte,optical sensors,battery safety,fiber Bragg grating,electrode active material,status monitoring
更新于2025-11-28 14:23:57
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[IEEE 2018 Asia Communications and Photonics Conference (ACP) - Hangzhou (2018.10.26-2018.10.29)] 2018 Asia Communications and Photonics Conference (ACP) - Non-invasive smart monitoring system based on multi-core fiber optic interferometers
摘要： A smart monitoring system based on fiber-optic interferometers using multi-core fiber (MCF) is presented in this paper. Interference among cores in the seven-core fiber (SCF) was introduced by using multi-mode fiber (MMF) coupling and experimental setup was designed to collect the data of user on bed for processing. With optimized algorithm, three body activities, including on the bed, off the bed and body movement, can be identified successfully. For further processing on collected data, respiration of the user can also be obtained. The smart monitor is contactless and non-invasive which is user-friendly and secure.
关键词： Smart monitoring system,Multi-core fiber,fiber sensor
更新于2025-11-28 14:23:57
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Fiber Brag grating monitoring of a morphing wing based on a polyvinyl chloride reinforced silicone substrate
摘要： Here, the three-dimensional (3D) shape monitoring of polyvinyl chloride (PVC)-reinforced silicone substrate for a morphing wing is detailed, using Fiber Bragg grating (FBG) sensors. An optical ?ber FBG sensor was embedded into a soft silicone substrate, which was glued onto the surface of a PVC substrate. This substrate was aligned with the morphing wing’s ?exible ribs of the. Sensing experiments were carried out both with and without the PVC reinforced silicone substrate, and the sensitivity and repeatability of the two sensors were compared. The PVC-reinforced silicone substrate sensor was calibrated using standard curvature calibration blocks to obtain a relationship between wavelength shift and the bending curvature of the PVC-reinforced silicone substrate, and the wing shape was reconstructed at di?erent deformation states. Several wing shapes were also reconstructed using a precise visual measurement system. Comparing the FBG sensing method with this visual measurement system demonstrated the e?ectiveness of the FBG method proposed here. Its maximum error was < 3%, so it can successfully sense the shape of a PVC-reinforced silicone substrate for morphing wing. The FBG sensing method therefore has potential for applications in shape monitoring in the ?elds of soft robotics and ?exible biosensor monitoring.
关键词： PVC reinforce silicone substrate,Wing shape monitoring,Soft sensor,FBG sensing
更新于2025-11-28 14:23:57
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Spectroscopic monitoring of laser blown powder directed energy deposition of Alloy 718
摘要： Experimental explorations of a spectrometer system used for in-process monitoring of the laser blown powder directed energy deposition of Alloy 718 is presented. Additive manufacturing of metals using this laser process experiences repeated heating and cooling cycles which will influence the final microstructure and chemical composition at every given point in the built. The spectrometer system disclosed, under certain process conditions, spectral lines that indicate vaporisation of chromium. Post process scanning electron microscope energy dispersive spectroscopy analysis of the deposited beads confirmed a reduction of chromium. Since the chromium concentration in Alloy 718 is correlated to corrosion resistance, this result encourages to further investigations including corrosion tests.
关键词： additive manufacturing,laser blown powder directed energy deposition,spectroscopic system,in-process monitoring
更新于2025-11-21 11:01:37
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Monitoring of polycyclic aromatic hydrocarbon contamination at four oil spill sites using fluorescence spectroscopy coupled with parallel factor-principal component analysis
摘要： Fluorescence spectroscopy analysis of oil and environmental samples collected from four oil spill incidents in Canada—a 2016 pipeline spill into the North Saskatchewan River (NSR), Saskatchewan; a 2015 train derailment in Gogama, Ontario; the 1970 sinking of the SS Arrow ship in Chedabucto Bay, Nova Scotia; and the 1970 sinking of the Irving Whale barge in the Gulf of St. Lawrence—permitted assessment of the PAH content of environmentally weathered samples. A recently developed fluorescence fingerprinting model based on excitation–emission matrix-parallel factor analysis-principal component analysis (EEM-PARAFAC-PCA) was applied to (i) evaluate the intensity of the abundant PAH groups in the samples, (ii) investigate changes in the PAH composition of environmental samples over time due to weathering, and (iii) classify the original spilled oil and environmental samples within the already established classes of the fingerprinting PCA model. The environmental sediment samples collected from the Husky Energy spill site show loss of PAHs occurring over the course of 15 months post-spill. However, the extent of weathering depends on several environmental factors rather than solely the time of weathering, the PAH loss was maximum at 15 months. There was a decrease in the PAH content of the environmental samples of Gogama spill collected 20 months post-spill. Almost all of Gogama environmental sediment samples underwent substantial weathering, making PCA classification impractical. The SS Arrow and Irving Whale samples fell within adjacent PCA groups, as they both had a similar type of spilled oil (Bunker C) with similarity in chemical composition.
关键词： EEM-PARAFAC-PCA,fluorescence spectroscopy,environmental monitoring,oil spill,PAH contamination
更新于2025-11-19 16:56:42
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Matrix-Independent Highly Conductive Composites for Electrodes and Interconnects in Stretchable Electronics
摘要： Electrically conductive composites (ECCs) hold great promise in stretchable electronics due to their printability, facile preparation, elasticity, and possibility for large area fabrication. A high conductivity at steady state and during mechanical deformation is a critical property for ECCs, and extensive efforts have been made to improve the conductivity. However, most of those approaches are exclusively functional to a specific polymer matrix, restricting their capability to meet other requirements such as the mechanical, adhesive and thermomechanical properties. Here we report a generic approach to prepare ECCs with conductivity close to that of bulk metals and maintain their conductivity during stretching. This approach iodizes the surfactants on the commercial silver flakes, and subsequent photo exposure converts these silver iodide nanoparticles to silver nanoparticles. The ECCs based on silver nanoparticles-covered silver flakes exhibit high conductivity because of the removal of insulating surfactants as well as the enhanced contact between flakes. The treatment of silver flakes is independent of the polymer matrix and provides the flexibility in matrix selection. In the development of stretchable interconnects, ECCs can be prepared with the same polymer as the substrate to ensure strong adhesion between interconnects and the substrate. For the fabrication of on-skin electrodes, a polymer matrix of low modulus can be selected to enhance conformal contact with the skin for reduced impedance.
关键词： conductive composites,human-machine interface,on-skin electronics,electrophysiological monitoring,iodization,silver nanoparticles,silver flakes
更新于2025-11-14 17:28:48