Arc Spectrum Research Articles

Features detection of Al alloy porosity during GTAW process based on arc spectrum and improved porosity-focus decision tree

As one of the common internal defects in the aluminum welding process, porosity defect is still challenging for real-time control due to the complexity and diversity of the welding process. Arc spectrum contains large amount of welding process information and is effective for the detection of internal defects. This paper proposed a real-time porosity defect detection method for aluminum alloy in gas tungsten arc welding (GTAW) based on the improved gradient boosting decision tree and arc spectrum. The line and continuum spectrum are separated, and the arc blackbody radiation energy and electron temperature are extracted based on the new spectral separation algorithm. Considering the long-tail distribution characteristic of the training samples, a porosity-focus loss function and a parallel training structure were proposed. More targeted line spectrum features were extracted. The defect recall rate increased by 8.6 %, and the area under the receiver operating characteristic curve (AUC) increased by 5 %, without affecting the detection accuracy and response speed. The confidence level of the prediction results was improved. The model shows better robustness through testing experiments in the face of complex welding conditions and is of great importance to the internal quality monitoring of GTAW.

Cu/W Electrode Ablation and Its Influence on Free-Burning Arcs in SF₆ Alternatives

A free-burning arc experiment was performed in a gas mixture composed of CO2/O2/C5F10O (85%/10%/5%). An optical emission spectroscopy (OES) diagnostic was developed to obtain spatially resolved arc spectra at a high frame rate. Spectral measurements are compared with simulated spectra to estimate arc parameters including temperature and composition. These techniques are used to characterize the arc and its associated electrode jets over a range of conditions, in order to study the influence of ablated Cu/W on arc characteristics. The observed spectra indicate that the ablation of the contact tip primarily occurs through vaporization rather than the expulsion of droplets. The metal vapor content of the arc is investigated as the arc driving current is varied, and a transition threshold for increased ablation at electrode current densities above 50 A <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\cdot $ </tex-math></inline-formula> mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{-2}$ </tex-math></inline-formula> is determined. The expansion angle of the electrode jet is estimated from the concentration of metal vapor in the arcing region at different axial positions, using a basic conical expansion model. The dependence of the measured voltage on the arc composition is examined, and a positive correlation between Cu content and arc voltage is identified. This trend is attributed to the higher emissivity of the metal vapor, which suppresses the central arc temperature and increases its resistivity.

Spectrum of Corona Discharges and Electric Arcs in Air under Aeronautical Pressure Conditions

Due to the increase in electrical power demand, future more electric and all-electric aircraft designs will operate at higher voltage levels compared to current aircraft. Due to higher voltage levels and reduced operating pressure, insulation systems will be at risk. Air is the main insulating medium, and it is well known that its dielectric strength decreases considerably with operating pressure. Although electrical discharges can be detected by different techniques, optical methods are very attractive due to their sensitivity and immunity to acoustic and electromagnetic noise typical of aeronautical environments. This work analyzes the UV-visible spectrum of corona discharges and electric arcs in the 10–100 kPa pressure range, which covers most of the aeronautical applications, due to the lack of experimental data for this pressure range. The data presented in this work are important to select the most suitable optical sensors to detect electrical discharges at an early stage, before significant damage occurs. This approach will help implement preventive maintenance plans and increase aircraft safety. The results presented in this paper can also be applied to other areas, such as monitoring of discharges in power lines, particularly those located in high-altitude regions.

Critically Evaluated Spectral Data for Singly Ionized Carbon (C ii)

All available experimental data on the spectrum of singly ionized carbon have been critically analyzed. Measurement uncertainties of all published studies have been reassessed. The scope of observational data includes laboratory emission spectra of arcs, sparks, electrodeless discharges, and hollow cathode lamps recorded with grating and Fourier transform spectrometers, laboratory photoabsorption spectra, and emission spectra of planetary nebulae. The total number of observed spectral lines included in this compilation is 597. These lines participate in 972 transitions. From this list of identified transitions, we have derived a set of 414 energy levels, which are optimized using a least-squares fitting procedure. The identifications are supported by parametric calculations with Cowan’s codes. The existing tables of critically evaluated transition probabilities have been extended with our newly calculated data. The ionization energy has been derived from the newly optimized energy levels with improved precision. Data on the isotope shifts and hyperfine structure have also been compiled.

Spectroscopic analysis of the arc plasma during activating flux tungsten inert gas welding process

A-TIG welding has been widely used in the manufacturing fields of aerospace, pressure vessels and ships as a highly efficient welding method. However, the mechanism of the effect of the activating flux on the arc behavior is still controversial. In this work, the spatial distribution of A-TIG welding arc spectra under the action of three types of active agents (fluorides, oxides and chloride) was studied using a spectral diagnostic method. The distribution characteristics of active agent particles, argon and iron particles in the arc were analyzed as well as the arc electron temperature was calculated using Boltzmann plot method. The experimental results shown that the distribution state of different active particles in the spatial of the arc is different. The influence of different active agents on the arc electron temperature in the spatial area of the arc is inconsistent. Chloride can cause a significant increase in the whole arc temperature. Fluoride can increase the arc electron temperature near the anode area. Oxide has less effect on the overall arc temperature.

Spectral Characteristics of GEO Satellite Arcing \u2013 300 To 350\xa0MHz

In a series of previous papers, the detection of arcing on GPS, Van Allen Probe, and GEO satellites with the Arecibo Observatory Wm. E. Gordon 305 m radiotelescope has been reported and elaborated. In this paper, characteristics of the radiofrequency spectra of two true GEO satellites are reported as they were measured with the Arecibo Mock spectrometer every 9.6 microseconds, and are contrasted with spectra of impulsive RFI (RadioFrequency Interference) events. It is shown that the arc spectra in the 300–350 MHz range are not continuous, but consist of a number of narrow spectral lines. These lines are consistent within the duration of single arcs, but change between arcs, so that when averaged over many arcs, the appearance of a continuous spectrum is approximated. This behavior is replicated in the laboratory within charging-induced vacuum arcing on small solar array samples. In contrast, the spectrum of impulsive RFI (including, but not limited to lightning strokes) is essentially random from one 9.6 microsecond sampling interval to the next. Since the spectrum of a true arc changes little throughout many samples, it cannot be due to the risetime of the arc current, which is much less than one sampling interval. Furthermore, in laboratory experiments done at very high time resolution (< 1 ns), there is little correlation between the arc current spectra and the arcing RFI spectra, indicating that even arc current fluctuations within each arc can have little to do with the UHF spectra observed.

Development of a methodology for the analysis of a fuel composition based on lithium and beryllium fluorides by atomic emission arc spectrometry

An atomic emission technique for the analysis of a fuel salt containing uranium and a coolant based on lithium and beryllium fluorides has been developed and tested. When developing the technique, the conditions accepted at Rosatom enterprises for the analysis of beryllium oxide and lithium carbonate were taken into account. The complexity of the structure of the arc spectrum of the matrix is noted. X-ray phase analysis of the sample residues in the electrodes revealed that the source of molecular bands in the spectra is lithium fluoroberillate. The analytical lines of Al, B, Ca, Cd, Cr, Cu, Fe, Mg, Ni, Pb, Si and Zn, free from overlap with the lines of the molecular spectrum and uranium were selected. A method of extreme experiment design is used to select optimal conditions for the arc excitation of the sample: the type and strength of the discharge current (alternating current 12 A), exposure time (20 sec), the shape of the electrode («glass») and the mass of the material (30 mg). Recommendations are given and implemented for the preparing samples for calibration using pure lithium fluoroberillate as a matrix material when introducing controlled elements in the form of certified reference materials of graphite (graphite collector of trace impurities). Calibration graphs in logarithmic coordinates are linear with angular coefficients close to unity. The metrological characteristics of the technique are evaluated in analysis of real samples: the repeatability, intermediate precision of the results and the limits of the element detection.

Comparison of the analytical capabilities of a facility with the arc double-jet argon plasmatron and a Grand-Potok complex in determination of the content of rare-earth elements in geological samples by atomic emission spectrometry

The method of atomic emission spectrometry with arc spectrum excitation provides determination of rare earth elements (REE) in geological samples by direct analysis of solid samples without a long-term preliminary sample preparation. Using the analysis of a rare-earth ore sample from the Tomtor niobium-rare-earth deposit as an example, we compared the analytical capabilities of a Grand Potok installation and a two-jet arc plasmatron (TJP) in combination with a DFS-458S spectrograph equipped with a multichannel emission spectrum analyzer (MAES). It is shown that a higher temperature of the TJP plasma (~7500 K) compared to that of the arc discharge (~5500 K) and the shift in the recording range of a DFS-458S spectrum to longer wavelengths (280 – 245 nm) provided a more reliable determination of REE using a larger number of analytical lines with lower detection limits. The correctness of the results of REE determination was confirmed by comparison with the data obtained by the ICP-MS method.

Quantifying the CaO and CaF2 Content of Industrial Ladle Furnace Slag with Optical Emissions Measured through the Casting Spout

CaO and CaF2 are important slag constituents and additive materials in secondary metallurgy. Optimization of the quantity of these compounds has a key role in adjusting the slag chemistry for optimal refining properties. Herein, the CaO and CaF2 content of the slag is analyzed with optical emissions from an industrial ladle furnace measured through the casting spout. Molecular optical emissions from CaO and CaF are observed directly from the molten bath and the arc, whereas atomic emission lines from the slag components are detected in the arc spectra. Optical emissions from CaO, CaF, and atomic calcium lines are correlated with the CaO and CaF2 content of the slag. The CaO and CaF2 content of the slag could be evaluated from the spectra ranging from 10 to 41 min before the X‐ray fluorescence (XRF) analysis is finished. The mean differences between the optical emission spectroscopy (OES) and XRF analysis are 0.59% and 0.61% for CaF2 and 2.19% and 0.67% for CaO when using the spectra from the molten bath and the arc, respectively. The method has the potential to work as an in situ online measurement system due to real‐time data acquisition and fast computation times.

The Thermal Properties of Gliding arc Plasma Produced by Laboratory Reverse Vortex Flow System

A low-cost reverse flow plasma system powered by argon gas pumping was built using homemade materials in this paper. The length of the resulting arc change was directly proportional to the flow rate, while using the thermal camera to examine the thermal intensity distribution and demonstrating that it is concentrated in the centre, away from the walls at various flow rates, the resulting arc's spectra were also measured. The results show that as the gas flow rate increased, so did the ambient temperature. The results show that the medium containing the arc has a maximum temperature of 34.1 ˚C at a flow rate of 14 L/min and a minimum temperature of 22.6 ˚C at a flow rate of 6 L/min.

Calculation of Arc Plasma Components in Underwater Wet Welding Based on Arc Spectrum Diagnosis

Calculation of Arc Plasma Components in Underwater Wet Welding Based on Arc Spectrum Diagnosis

Thermal Plasma of Electric Arc Discharge Between Composite Cu-Cr Electrsodes: Optical Emission and Electrode Surface Interaction

This work deals with investigations of thermal plasma of electric arc discharge between sintered composite Cu-Cr electrodes, which can be used in electrical contacts of vacuum circuit breakers. Breaking arcs between composite Cu-Cr as well as single-component copper electrodes were used to study the electrical properties, plasma optical emission and electrodes surface modification behavior. In particular, the temporal evolution of plasma emission spectra of electric breaking arcs in air atmosphere was investigated by Optical Emission Spectroscopy (OES). Scanning Electron Microscopy (SEM) with Energy-dispersive X-ray Spectroscopy (EDXS) were applied to analyze the cross-section of working layer of electrodes surface modified by the heat flux from the discharge.

High Speed Photography for Arc Welding Phenomenon Using 808 nm Diode Laser Illumination and Optical Filter

In this study, high-speed photography was performed for Gas Metal Arc Welding using an 808 nm diode laser and an optical filter. A Neutral Density(ND) filter and an 808 bandpass filter were used to an excluded arc light. We observed that the applied ND filter succeeded in capturing the drop transfer, but the arc image could not be excluded. When considering the spectral distribution of the arc, the 808 nm diode laser is suitable for recording a high speed camera sensor. The Full Width Half Maximum (FWHM) 3 nm of 808 nm bandpass filter is suitable for removing the arc spectrum signal. By combining an 808 nm diode laser and an 808 nm bandpass filter, we obtained a clear image of the drop transfer without the arc light. Key words: High speed photography, 808 nm diode laser, Neutral density filter, Band pass filter, GMAW, Drop transfer

Arc spectra of different solid reduced graphene oxide samples under microwave irradiation

It is often accompanied by an intense arc when solid-state graphene samples are irradiated by microwaves (MWs); however, arc spectra have not been studied. In this study, the arc spectra of reduced graphene oxide (RGO) powder, three-dimensional (3D) porous RGO, and RGO paper under MW irradiation were measured; these spectra exhibited diverse features. For the same reaction conditions and the same initial sample, the arc spectra should be the same if the reaction process and mechanisms are the same. Further analyses showed that the obtained RGO paper with an evident 2D band, a smaller D band, lower sheet resistance, and lower oxygen content was of higher quality than the RGO powder and 3D porous RGO obtained after MW irradiation. Based on these results, the diverse spectra may suggest different reaction processes and mechanisms. Overall, these findings provide novel insights into the preparation of graphene via MW reduction.

Molten image fusion and enhancement based on image decomposition in frequency domain

In this paper, we propose a novel molten image enhancement and fusion method based on image decomposition in frequency domain. The algorithm combines the guided filter to maintain the original edge and details and to make it show a more permeable visual effect. Firstly, the high-quality molten imaging band is obtained by analyzing the characteristic spectra of welding materials and arcs. We choose the bands with more spectra feature of materials and weaker arc interference as our optical path channels and collect color images at the same moment to obtain more molten information. Then, after a series of image preprocessing, we combine the details extraction strategy and the guided filter together to yield a novel fusion algorithm, which can make the fusion result to have rich information, clearer edge and higher contrast. Finally, the experimental results show that the proposed method has obvious advantages over some existing methods from the objective and the subjective view.

Experimental Study of Relationship Between Arc Light Intensity and Temperature in Low-Voltage Switching Devices

Arc motion in a quenching chamber has a significant influence on switching performance in a low-voltage switching device (LVSD). A high-speed optical arc imaging system (AIS) has been used to investigate the influence of the design parameters of a quenching chamber on arc motion. Arc light intensity is transmitted to the photodiodes of the AIS through optical fibers during the switching process. The AIS and associated software enable the detailed arc motion to be tracked inside the chamber at an image sampling rate of 1 MHz. Since higher arc temperature leads to greater radiation, it is assumed that the arc light intensity measured by the AIS is related to the arc temperature. However, there has been a little empirical study of the correlation between the arc temperature and light intensity measured by the AIS. In this article, the relationship between the arc temperature and light intensity is investigated by measuring arc spectra and arc images. Arc spectra are captured by a spectrometer when the arc is ignited by copper wire in a narrow enclosed chamber, and they are used to calculate the arc temperature by the Boltzmann plot method. At the same time, the AIS records the arc images from points adjacent to the fiber of the arc spectrometer. It is found that the arc light intensity measured by the AIS is directly related to the arc temperature; the correlation between the fourth power of temperature and the light intensity is an approximately linear trend.

Real-time monitoring and control of porosity defects during arc welding of aluminum alloys

Abstract The detection and control of the internal porosity have attracted increasing attention in the arc welding of aluminum alloys. In this paper, a spectrometer was utilized to realize the in-situ detection and processing of arc spectra. By performing improved locally linear embedding on the spectral band of interest, the mapping vectors characterizing porosity defects and the intrinsic structure of the spectra were obtained. To improve the identification accuracy of porosity defects, the ratio feature of specific spectral lines acquired by empirical mode decomposition was used as an evaluation index as well. Based on the above features, the rapid and high accuracy prediction of porosity defects was realized by extreme learning machine. A controller based on the Fuzzy-PID was designed to regulate and control the porosity defects evaluated by spectral features in real time. The closed-loop control experiments showed that the Fuzzy-PID control system achieved the porosity control under various welding assembly conditions by adjusting the welding current.

Optical Emission Spectroscopy as an Online Analysis Method in Industrial Electric Arc Furnaces

The development of online analysis methods for industrial electric arc furnaces (EAFs) has been a major research topic in recent years. Process control becomes even more important in the future due to the increase in both the usage of recycled metal as charge material and the metal recycling rate. For the industry to keep up with the pace, reliable chemical analysis of the slag together with online information about the furnace operation status is essential. Herein, optical emission spectroscopy is used to obtain the information about the electric arc together with radiative properties and surface temperature of the molten bath in an industrial EAF. The arc is visible for high alloyed steel grades within 5–30 min before tapping and the arc spectra are dominated by the optical emissions from the slag components. The plasma properties of the electric arc are determined with emission lines from atomic chromium, iron, and calcium. The time evolution of the spectra for high alloyed and carbon steel grades are compared with each other to provide a better understanding of the differences in the spectra between these two steel grades.

Detection of DC series arc in more electric aircraft power system based on optical spectrometry

Series arcing faults have been recognised as a hazardous phenomenon in the power system of more electric aircraft (MEA), especially with the increasing voltage level and power supply. Instead of the electrical method, the optical method can be used as an approach to detect arc fault with the advantages of fast response and immunity to electromagnetic interference. It is the basis of optical arc detection to determine the distribution spectrum range of direct current (DC) arc fault. Aiming at series arc optical detection in the MEA DC system, a DC series arc test platform was established to measure the series arc spectrum. The spectrum was disassembled though empirical mode decomposition to extract characteristic wavelengths of arc light and de-noised by means of wavelet decomposition and reconstruction (wavelet transformation) to reduce equipment noise. To resolve the baseline drift, the baseline of the arc spectrum measured was calculated and corrected based on Savitzky−Golay. The experimental results indicate that there are several series arc characteristic spectra of the MEA DC system, including 309.3 and 324.5 nm in the ultraviolet range. Moreover, the arc spectrum with different metals, copper and aluminium, were contrasted, indicating the arc spectral behaviour is related to the melting/boiling point and chemical properties of the anode material. The measurement of the series arc spectrum makes it more effective to apply optical detection in the MEA discharging faults diagnosis.

Pantograph Arc Detection of Urban Rail Based on Photoelectric Conversion Mechanism

According to the solar-blind characteristic of the pantograph arc spectrum distribution, an arc detection method based on the photoelectric conversion mechanism for urban rail was proposed, and the design of each part of the arcing detection system was completed. Through the analysis of arc spectral distribution, the 275-285 nm band was determined as the detection characteristic waveband. The optical acquisition system located on the roof of the train collects the arc characteristic light and transmits it to the photoelectric conversion module, which converts the received optical signal into the corresponding current signal linearly. After amplification, comparison and screening in this module, the optical signal is sent to the data processing module for output display. Finally, a field test conducted on an urban rail transit line shows that this arc detection system can effectively detect the pantograph arc phenomenon and reflect the arc intensity linearly avoiding the influence from natural light, train load and train running direction.