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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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In-situ monitoring method of PECVD process equipment condition
摘要： A key to successfully have a consistent plasma processing is the maintaining a consistent process chamber condition over a certain production period. To alleviate the concern, in-situ process monitoring sensors are optical emission spectroscopy (OES), optical plasma monitoring sensor (OPMS), VI-probe, and self-plasma optical emission spectroscopy (SP-OES). During the deposition, we perform the monitoring of plasma condition associated with the applied RF power via OES, OPMS and VI-probe. In the chamber cleaning step using remote plasma system does not allow plasma monitoring through sidewall because the plasma is not formed in the process chamber, thus we employed SP-OES to monitor by-product gas chemistry during the chamber cleaning process step. Successful monitoring results with some useful applications, such as arc detection, part failure detection, and cleaning process chemistry analysis, are presented in this paper. The use of in-situ sensors with proper combination can help understanding plasma process better to achieve more precise control of the plasma processing.
关键词： in-situ monitoring,advanced process control,advanced equipment control
更新于2025-09-23 15:23:52
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Effects of low-temperature sintering on surface morphology and electrical performance of silver nanoparticle/carbon nanotube composite films
摘要： Silver nanoparticle (AgNP)/carbon nanotube (CNT) composites are drawing increasing attention for several applications, especially where transparency is required. However, interfacial interaction and stability of the AgNP/CNT composites have been scarcely investigated. In the present study, transparent coatings were prepared from dispersed AgNP-coated multiwalled CNTs and exposed to different annealing conditions. The changes in surface morphology and evolution of interfacial configuration of AgNP-decorated CNT transparent composite films were investigated. Under certain conditions, CNT ropes were glued to one another by the melted AgNP aggregates, resulting in the improvement of the measured electrical properties. The in situ measurements of the electrical properties allowed correlating the AgNPs sintering mechanism with the morphological observations. Notably, at a given temperature, increasing the initial film density increased the time necessary to complete the AgNPs sintering. The obtained results show that the electrical resistance can be used as a tool to indirectly monitor the network state of transparent AgNP-decorated CNT composite films, hence paving the way to tuning the composite film properties with a high precision for the desired application. These findings also explain the mechanism of reinforcement of polymer nanocomposites by the current nanofillers.
关键词： A. Silver nanoparticle,B. Carbon nanotube,E. In situ monitoring,D. Sintering,F. Electrical properties,C. Nanocomposite
更新于2025-09-23 15:22:29
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Thermal Mapping of a Lithium Polymer Batteries Pack with FBGs Network
摘要： In this paper, a network of 37 fiber Bragg grating (FBG) sensors is proposed for real-time, in situ, and operando multipoint monitoring of the surface temperature distribution on a pack of three prismatic lithium polymer batteries (LiPBs). Using the network, a spatial and temporal thermal mapping of all pack interfaces was performed. In each interface, nine strategic locations were monitored by considering a three-by-three matrix, corresponding to the LiPBs top, middle and bottom zones. The batteries were subjected to charge and discharge cycles, where the charge was carried out at 1.0 C, whereas the discharge rates were 0.7 C and 1.4 C. The results show that in general, a thermal gradient is recognized from the top to the bottom, but is less prominent in the end-of-charge steps. The results also indicate the presence of hot spots between two of the three batteries, which were located near the positive tab collector. This occurs due to the higher current density of the lithium ions in this area. The presented FBG sensing network can be used to improve the thermal management of batteries by performing a spatiotemporal thermal mapping, as well as by identifying the zones which are more conducive to the possibility of the existence of hot spots, thereby preventing severe consequences such as thermal runaway and promoting their safety. To our knowledge, this is the first time that a spatial and temporal thermal mapping is reported for this specific application using a network of FBG sensors.
关键词： in situ monitoring,lithium polymer batteries pack,FBGs network,safety,thermal mapping
更新于2025-09-23 15:22:29
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Au@Ag nanorod horizontal arrays: Self-assembly preparation and in situ monitoring SERS of plasmonic catalytic reaction
摘要： Here, we successfully synthesized silver-coated gold nanorods (Au@Ag NRs) via a facile wet chemical method. The catalytic property of Au@Ag NRs in water solution was much better than that of Au NRs in water solution. To obtain high catalytic properties, we self-assembled a single-layer Au@Ag NR array by evaporation on a silicon wafer. The catalytic activity of the Au@Ag NR array was probed using the reduction of 4-nitrothiophenol. The reaction processes were monitored and identified through in situ surface-enhanced Raman spectroscopy based on the confocal Raman microscope system. This study provides a simple and fast method to improve the catalytic property of the noble nanoparticles.
关键词： In situ monitoring,Self-assembly,Au@Ag nanorods,Plasmonic catalytic reaction,SERS
更新于2025-09-23 15:19:57
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An investigation on the measurement of instantaneous temperatures in laser assisted additive manufacturing by thermal imagers
摘要： Powder bed fusion additive manufacturing processes has started to be investigated by means of temperature distribution and change on parts, since problems such as residual stresses, deformations, microstructural differences and lack of mechanical properties were observed due to temperatures of parts during manufacturing. In the current studies, thermal cameras were used to analyze thermal history of parts. Depending on the accuracy of thermal cameras, temperature values were varied. In this study, a mathematical model which was supported by the data of experimental tests was developed to obtain increased accuracy. Melt pool temperatures were predicted by using the model which consisted of average temperature and extrapolated measurement area approaches. Melt pool temperatures were calculated ranging between 1700 and 2800 °C. Besides, temperature-dependent cooling rate was considered in the model to improve accuracy of temperature measurement. In addition, finite element analysis of manufacturing process was performed to verify results. Comparison between results of the mathematical equations and finite element analysis showed the accuracy as minimum 85% and maximum 98%. A trusted equation was generated to calculate melt pool temperatures by using an ordinary thermal imager.
关键词： Thermal imager,Additive manufacturing,Powder bed fusion,In-situ monitoring
更新于2025-09-23 15:19:57
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In-situ optical emission spectroscopy of selective laser melting
摘要： The variances in local processing conditions during Selective Laser Melting (SLM), a powder bed Additive Manufacturing (AM) process, can cause defects that lead to part failure. The nature of SLM permits in-situ monitoring of radiometric signals emitted from the part surface during the process, including optical emission from excited alloying elements. Using Optical Emission Spectroscopy (OES) to measure the spectral content of light emitted gives insight into the chemistry and relative intensities of excited species vaporized during SLM processing. The contribution from investigating the use of in-situ OES to gain information about local processing conditions during SLM is reported in this paper. A spectrometer is split into the SLM system laser beam path to measure visible light emitted from the melt pool and plume during the processing of 304L stainless steel. The in-line configuration allows signal collection regardless of the laser scan location. The spectroscopic information is correlated to the melt pool size and features of SLM samples for various build conditions (i.e., process parameters, build chamber atmosphere type, and pressure).The limitations that exist in OES implementation for certain build chamber conditions are discussed. The results in this paper are initial progress towards the use of OES in SLM part qualification and controls applications.
关键词： Metal additive manufacturing,Optical emission spectroscopy,In-situ monitoring,Powder bed fusion
更新于2025-09-19 17:13:59
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In-situ characterization of tungsten microcracking in Selective Laser Melting
摘要： Additive Manufacturing is a promising way of processing tungsten, with opportunities to create more complex parts than are possible using other powder metallurgical routes. This may lead to extended applications such as collimators, in fusion reactors, or in other structurally loaded, high temperature environments. The poor thermal shock resistance and ductile-to-brittle transition that occurs in tungsten above room temperature are challenges that hinder production of fully dense and crack free parts. This research employs high speed in-situ monitoring of Selective Laser Melting of single tracks to visualize crack initiation and propagation. The circumstances that lead to cracking are correlated with microstructural morphology and processing conditions.
关键词： In-situ monitoring,Additive Manufacturing,Microcracking,Laser powder bed fusion,Tungsten,Selective Laser Melting
更新于2025-09-12 10:27:22
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Why is in situ quality control of laser keyhole welding a real challenge?
摘要： In this work, we investigated keyhole welding including the pore dynamics (creation and collapse) of aluminium at the European Synchrotron Radiation Facility (ESRF, Grenoble, France). Optical back reflection and acoustic signals were simultaneously recorded during the welding process which was also visualized by high-speed X-ray imaging. This allows correlating the different momentary events with the signals recorded by the sensors. We demonstrate that keyhole welding is a highly dynamical and unstable process. In addition, to use either acoustic or optical sensors for pore detection, highly advance statistical methods such as machine learning are a requisite for signal processing.
关键词： in-situ monitoring,acoustic emission,X-ray imaging,Laser welding
更新于2025-09-12 10:27:22
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Spatial modulation of laser sources for microstructural control of additively manufactured metals
摘要： Metal powder-bed fusion additive manufacturing (AM), while demonstrating great potential across a diverse application space, still lacks the necessary control to obtain parts that meet strict performance-driven criteria. In this work, we explore spatial laser modulation to enhance the properties and processability of AM metals. Experiments are carried out with the goals of demonstrating control of the columnar-to-equiaxed transition, identify methods to reduce surface roughness, and extend processing windows for AM alloys. Results show that beam modulation provides site-specific microstructural control, and these results are interpreted using finite element modeling of the melt pool dynamics and thermal profiles.
关键词： In situ monitoring,Microstructure,Additive Manufacturing,Beam shaping,Selective Laser Melting
更新于2025-09-12 10:27:22