Contact Voltage Research Articles

Stylus pen-based ambient ionization mass spectrometry for the analysis of volatiles and semivolatiles from liquid, viscous, and solid samples.

Ambient ionization mass spectrometry (MS) has attracted significant attention due to its simplicity and ease of operation. Contactless, or field-induced, ionization is one of the ambient ionization techniques. In this approach, no direct electrical contact or additional voltage is required on the ionization-assisted substrate. Instead, the electric field is induced by the high voltage applied to the orifice of the mass spectrometer. However, there remains a demand for exploring compact and readily available ionization substrates for use in field-induced ionization techniques. A stylus pen, typically used for touch screens, is used as an ion source for analyzing volatile and semivolatile organic compounds. Vapors originating from volatile and semivolatile compounds placed underneath the inlet of the mass spectrometer were ionized when the stylus pen was positioned near the inlet, which is applied with a high voltage. The limits of detection for semivolatiles and volatiles were in the range of mM to a few hundred nM, depending on the vapor pressure and chemical structures of these analytes. Additionally, semivolatile compounds found in real samples could be directly detected using our method. Moreover, we also demonstrated the feasibility of using the stylus pen as the sampling probe to pick up samples from the surface of a glass slide, followed by bringing the pen close to the inlet of the mass spectrometer for direct MS analysis using our approach. The developed method provides a straightforward approach for analyzing volatiles and semi-volatiles under ambient conditions. Ionization of the analyte vapor near the mass spectrometer inlet can readily occur by placing a stylus pen close to the inlet, highlighting simplicity as the main advantage of the developed method. Consequently, this method can be easily coupled with a mass spectrometer that has a high voltage applied to its orifice.

Clinical Importance of Tissue Proximity Indication During Pulsed Field Ablation for Atrial Fibrillation: Insights from Initial Experience.

Pulsed field ablation (PFA) for paroxysmal atrial fibrillation (AF) has been gaining worldwide acceptance due to its efficacy and safety. A variable loop circular catheter (VLCC, VARIPULSE, Biosense Webster, Inc.) for PFA, recently launched in Japan, includes a Tissue Proximity Indication (TPI) feature to monitor catheter-tissue contact via impedance. However, the role of TPI during pulmonary vein (PV) isolation (PVI) is unclear. This study aims to evaluate TPI feasibility during PVI and its relationship with acute PV reconnection. Twenty-one paroxysmal AF patients underwent PFA (four ablations per PV at least) using the VLCC. We evaluated the association between TPI-positive site percentages, voltage, left atrial wall thickness on ADAS 3D software, and acute PVI failure sites. Four of 21 patients (8 failure sites) experienced PVI failure after primary PFA. Failure sites had significantly lower TPI-positive site percentages (0±0% vs. 63±27%, p< .001) and higher voltage (3.57±1.35 mV vs. 2.06±1.42 mV, p= .003), but not PV wall thickness. We found that a left atrial bipolar voltage amplitude ≥2.24 mV was determinants of PV gaps with an area under the curve of 0.83 calculating receiver operating characteristic curves. TPI-positive site percentages increased significantly (58±29% to 64±26%, p= .009), while PV gaps decreased from 3/28 PVs (11%) to 2/54 PVs (4%, p= .332) between the first 7 and last 14 cases. Acute PVI failure was significantly associated with poor tissue contact and higher voltage. However, acute PVI failure can be prevented with improved TPI-based contact information.

A Degradation Model of Electrical Contact Performance for Copper Alloy Contacts with Tin Coatings Under Power Current-Carrying Fretting Conditions

The fretting degradation of coating materials is complicated when the Joule heating effect of the load current is non-negligible. In this work, the fretting degradation behavior of tin-coated copper alloy contacts was examined across the current range from 5 A to 30 A and the fretting amplitude range from 200 μm to 400 μm. The uniform degradation process and associated mechanisms, including the wear-dominated stage, softening-dominated stage, and oxidation-dominated stage were recognized and interpreted explicitly. An innovative fusion model for the degradation of electrical contact performance, data-driven and based on physics mechanism, was proposed. The contact voltage was selected as the characterization variable and pre-processed by the threshold-crossing filter method and the Levenberg–Marquardt algorithm. The optimal degradation model, considering the coupled effects of current and fretting amplitude, was presented with the use of the support vector regression method. Finally, the prediction accuracy of the model was validated by experiment results.

Enhanced methylene blue removal from aqueous solution by electrocoagulation technique using combined iron and copper electrode

The rapid advancement in the industrial sector, particularly within the textile industry, necessitates the use of colorants for fabric processing, with methylene blue being a predominant choice. However, the improper disposal of methylene blue dyes can lead to significant environmental hazards, underscoring the need for effective treatment methods before release into ecosystems. This study explores electrocoagulation, an innovative treatment technique powered by electrical energy, as a potential solution for mitigating the environmental impact of methylene blue in textile wastewater. The research investigates the efficiency of the electrocoagulation process using iron (Fe) and copper (Cu) electrodes under various operational conditions, including electrode spacing (1, 1.5, and 2 cm), applied voltage (15, 20, and 24 volts), and electrode contact time (5, 10, 15, 20, 30, and 60 minutes). The findings reveal that the electrocoagulation method achieves an optimal methylene blue removal efficiency of 99% under specific conditions: an electrode distance of 1.5 cm, an applied voltage of 24 volts, and a contact duration of 30 minutes. This research underscores the potential of electrocoagulation as an efficient and environmentally friendly approach for the treatment of textile wastewater, contributing to the sustainable management of industrial effluents.

Comparative Electrochemical Analysis of Lithium and Lithium-Indium Alloy in All-Solid-State Battery

Lithium-ion batteries (LIBs) are widely used in a variety of applications due to their high energy and power densities, and long cycle life. With the expanding use of LIBs in electric vehicles and energy storage systems, there is very active research into all-solid-state batteries (ASSBs), which offer greater energy density than traditional LIBs and eliminate the inherent fire hazards. Since most of the detailed reactions involved in the performance and degradation of a battery are temperature-sensitive, so-called thermal activation processes, it is very important to accurately assess whether a battery can have the high performance and low degradation characteristics required under different climatic conditions. To evaluate the electrochemical properties of electrode materials in LIBs, a half-cell is typically constructed with the electrode of interest as the working electrode (WE) and lithium metal as auxiliary electrode (AE). Here, lithium metal is close to an ideal non-polarizable material, has a large capacity, and maintains a constant potential during charge/discharge, so it is widely used as AE material in LIB research. However, several issues arise when lithium is used as AE in ASSBs: Lithium metal undergoes mechanical deformation due to the relatively high internal pressure required to ensure good contact between lithium and solid electrolyte; When in contact with sulfide-based solid electrolytes, which are currently of interest due to their high ionic conductivity, side reaction products can lead to an increase in interfacial resistance; the growth of lithium dendrites, often observed in conventional LIBs, is still unavoidable. These issues all affect the half-cell signal, potentially causing a distorted evaluation of the WE’s characteristics.Lithium-indium alloy is being utilized as AE for ASSB half-cells to replace lithium metal. It exhibits excellent mechanical ductility and maintains a constant reduction potential over a wide stoichiometric range, ensuring excellent contact property and voltage stability. Moreover, it is very easy to fabricate through simple compression at room temperature. Nevertheless, the limited study on its electrochemical properties leaves uncertainty regarding its full functionality as AE for accurate evaluation of WE, particularly in extreme operational conditions. For instance, lithium-indium alloy are primarily based on alloying/dealloying reactions involving solid-state diffusion of lithium, which is generally considered to be a relatively slow process kinetically, while lithium only involves a kinetically favorable plating/stripping process on the surface. Therefore, a comparative analysis of these different reaction mechanisms in terms of kinetics is necessary. This presentation presents a comparative analysis of the electrochemical properties of lithium metal and lithium-indium alloys used as AEs in ASSB half-cells. In particular, the electrochemical properties of lithium-indium alloys with different reaction mechanisms with lithium are investigated over a range of temperatures and current densities, and these differences are discussed from a kinetic point of view. For this purpose, first, using a three-electrode half-cell with lithium or lithium-indium alloy as AE, we compared the electrochemical properties of these two AEs during half-cell operation by interpreting their potential and over-potential changes, and quantifying their detailed resistances. Then, through dc experiments on lithium and lithium-indium symmetrical cells, we identified differences in overvoltage behavior due to differences in their reaction mechanism. In particular, we noted distinct differences in the overpotential behavior of these two electrodes at low temperatures and high current densities. Furthermore, based on the results of a combined dc/ac electrochemical analysis, we derived the overvoltage that dominates the overall overvoltage at each of the two electrodes. Based on these results, we analyzed how the kinetic differences between the two electrodes affect the cathode half-cell signal, in order to derive key considerations for reliable ASSB half-cell evaluation. In this presentation, the advantages and disadvantages of lithium-indium alloy compared to lithium metal as AE will be discussed from a kinetic perspective, focusing on interfacial and bulk resistance (overpotential). Furthermore, methods for utilizing AE to conduct accurate and reliable half-cell tests will be proposed.

Design of substation grounding grid in CFETR

This paper aims to propose a method for the design of the substation grounding grid in China Fusion Engineering Test Reactor (CFETR). In order to evaluate the safety of the grounding grid, Electrical Transient Analysis Program (ETAP) was used to simulate the fault current, contact voltage, and step voltage, and the results are compared with theoretical calculations to verify the correctness of the design. This will help reduce faults caused by the defects of grounding grid This method is special in that the designed grounding grid not only meets the requirements of relevant standards, but also reduces the number of conductors. During the design process, factors such as voltage level, fault location, and soil resistivity were fully considered to adapt to different occasions. This method can also guide the design and renovation of grounding grids for other buildings in CFETR.

Monitoring system for electrical load usage characteristics in electrical engineering building

Electrical energy is becoming increasingly essential for educational activities in electrical engineering facilities, as these activities include the use of electrical equipment. The quantity of electrical loads in buildings escalates annually, resulting in increased demand on existing lines and the original design of building construction. Nonetheless, the positioning and allocation of the load within the panel do not align with the augmentation of the load. Consequently, the load becomes uneven across all three stages. Phase T is experiencing an overload, while Phase R has a lesser burden compared to Phases S and T. The maximum current in Phase T is 36.3 A; the imbalance is excessive, leading to a neutral current of 25.2 A. This is perilous since the present value at the neutral point ought to be zero; if the load remains unregulated, it will lead to a contact voltage in electrical apparatus. The utilization of cables is unsuitable due to the substantial connected load, while the cable diameter is merely 2.5 mm², capable of conducting a maximum current of 21 A. Therefore, it is imperative to reassess the electrical installation in the engineering building to avert short circuit disruptions.

Reliable Determination of Contact Angle from the Liquid Fence.

Traditional methods of measuring contact angles often face difficulties in precisely defining the three-phase contact points. A novel method for accurately defining three-phase contact points based on liquid fences is proposed in this article. The tested liquid is placed in a cubic liquid fence composed of a pair of narrow strips of the tested solid and a pair of transparent wide strips. The transparent wide strip serves as the measurement window, and the surface tension of the liquid on it can be almost ignored. In experimental measurements, the horizontal coordinates of the end points of the liquid profile are fixed by the liquid fence, thus determining the horizontal coordinates of the three-phase contact points, which helps to accurately survey the contact angle. Additionally, since the parameters of the liquid fence are known, the size of the contact angle can also be calculated by measuring the height of the liquid level dome inside the liquid fence. Using the electric wetting effect as an example, we experimentally extracted a series of liquid contour maps with circular tops and square columns under varying voltages. The relationship curve between contact angle and voltage variation was obtained using the above methods, and a contact angle variation tendency seemed to agree well with the theoretical value.

Research and Investigation of High Frequency Profile of Step and Touch Voltages Due to Fragmentation of the Grounding Grid

The increasing demand and the benefits of electricity energy have led to the creation of huge power plants, so high voltage substations are necessary for electrical energy. Installing different small power plants to prevent consumption in different parts of a country requires reservation units and high costs for repairs, maintenance and fueling. The necessity of these substations can be searched in the lack of uniformity of different costs, the costs of generating electrical energy, the lack of consumption centers near power plants, and generally the existence of a national grid and the possibility of timely disconnection of the faulty parts of the power grid. The priority in the rehabilitating of a strong substation is to meet the system's operation needs. In all electrical installations, especially in industrial complexes, land connectivity is one of the most important and fundamental measures to protect individuals and equipment and improve the performance of the system. The purpose of ground equipment system is to potentialize the metal body of all electrical equipment with the ground to prevent electrocution and protect personnel. This type of connection is not normally a current carrier, but if one of the phases of the device is connected to the fuselage, the fault current enters the ground through this connection and closes its path through the trans neutral or the generator connected to the ground. Earth networks due to different structures of the earth in different regions may cause problems over time, one of them is the fragmentation of the earth's network due to rot of conductors or due to overvoltage. In this research at different and high frequencies, we use 3 frequencies of 50, 100 kilos and 1 MHz, to check the ground network factors and the security of equipment and people in high voltage substations, we use CDEGS software which is a specialized program for designing and investigating the earth network. Objetivo: Research and investigation of high frequency, profile of step and touch voltajes of grounding grid. Metodología: Design and modeling with Comsol software. Resultados: As the frequency increases, both the step voltage and the touch voltage at the corner points increase more. Conclusiones: By comparing the voltage profiles based on the simulation results, it was found that by increasing the frequency of the contact voltage in each profile and mesh, it is noticeably increased. The point to consider after reviewing the simulation results is that by increasing the frequency of both step voltage and touch voltage in the corner points, they are more increased than other parts.

Multi Electrode Differential Voltage Sensor Based on Electric Field Coupling

With the increasing demand for electricity, voltage measurement has been applied in various fields of the power grid, especially in low-voltage distribution networks and household appliances. However, in low-voltage distribution networks, traditional contact measurement cannot be used due to technical limitations such as the need to damage the insulation layer. Non contact voltage measurement is becoming the main voltage measurement method, A major technical challenge in non-contact measurement is the interference of external electric fields. In order to solve the above problems, this article develops a new type of non-contact low-voltage measurement equipment, which can overcome the interference of external electric fields on measurement and achieve high-precision non-contact voltage measurement. The experimental results indicate that the sensor designed in this paper has high measurement accuracy. The ratio error at power frequency is within ± 0.9%, and the phase error is within 3°. In addition, the sensor also has the advantages of low cost, small size, and convenient manufacturing.

Formation of ohmic contacts on heavily Al+-implanted p-type SiC without an alloying process

The current–voltage (I–V) characteristics and contact resistivity ( ρc ) of Ni electrodes formed on heavily Al+-implanted p-type SiC without an alloying process were investigated. A nearly ohmic I–V curve with a ρc of 9.3 × 10−2 Ωcm2 was demonstrated for non-alloyed Ni electrodes by very high-dose Al+ implantation (3.1 × 1020 cm−3). The dependence of the experimental ρc on net acceptor density (N A) can be described by a change in the contribution of direct tunneling and trap-assisted tunneling.

Research on Non-Invasive Voltage Measurement Method Based on Impedance Adaptation

Transformer-based contact voltage measurement requires electrically charged installation during use. Moreover, there are problems with large sizes and restricted installation locations. The current non-contact voltage measurement technology is based on the principle of capacitive coupling in measurement. The capacitance between the probe and the wire is affected by the diameter of the wire and the insulation material. This results in an unstable sensor gain relationship, which leads to low measurement accuracy. This paper proposes a non-contact multi-wire adaptive voltage measurement method, and self-calibration of the sensor gain is achieved through practical measurements. First, the basic principle of capacitively coupled voltage measurement is introduced, from which the existing problems are condensed. An impedance-based adaptive method is proposed, based on which a new sensor probe is developed. The accuracy test reveals that the maximum relative error of voltage amplitude is 0.89 percent, the relative error of phase is 0.38%, and the relative phase error is within 1 degree for a specified voltage range (100 V-300V). The scenario adaptability test shows that the maximum relative error is 1.7% when performing tests on different types of lines. This sensor has the advantages of compactness, convenience, low cost, and high practicality.

Dynamics of Tribofilm Formation in Boundary Lubrication Investigated Using In Situ Measurements of the Friction Force and Contact Voltage.

The complex dynamics of tribofilm formation on boundary-lubricated steel surfaces were investigated in real time by combining in situ measurements of the temporal variation of the coefficient of friction and contact voltage. Sliding experiments were performed with various blends consisting of base oil, zinc dialkyl dithiophosphate (ZDDP) additive, and two different dispersants at an elevated oil temperature for a wide range of normal load and fixed sliding speed. The evolution of the transient and steady-state coefficient of friction, contact voltage, and critical sliding distance (time) for stable tribofilm formation were used to evaluate the tribological performance of the tribofilms. The blend composition affected the load dependence of the critical sliding distance for stable tribofilm formation. Tribofilm friction was influenced by competing effects between the additive and the dispersants. Among various formulations examined, the tribofilm with the best friction characteristics was found to be the blend consisting of base oil, a small amount of ZDDP, and a bis-succinimide dispersant treated with ethylene carbonate. The results of this study demonstrate the effectiveness of the present experimental approach to track the formation and removal of protective tribofilms under boundary lubrication conditions in real time.

Assessing High-Voltage Shore Connection Safety: An In-Depth Study of Grounding Practices in Shore Power Systems

There is growing concern regarding air pollutants (NOx, SOx, and PM) and carbon emissions from ocean-going vessels in harbor areas and the role of high-voltage shore connection (HVSC) systems in mitigating these emissions during vessel berthing. The HVSC operates as a TN grounding system in humid environments, and it needs a proper grounding design to ensure safety when faults occur. This article intends to examine the overvoltage resulting from fault currents and its implications for the safety of operators when a single line-to-ground fault takes place within the design of HVSC grounding systems. The assessment is carried out by employing actual scenarios and parameters from a container berth at Kaohsiung Harbor in Taiwan. Considering site conditions, such as the wet ground surface, human body resistance, and electric shock duration, the tolerable safe voltage level is derived using IEEE Std. 80 and IEC 60479-1. Based on the shore power system grounding architecture specified in IEEE/IEC 80005-1, an equivalent circuit model is constructed to calculate the fault currents using symmetrical component analysis. The actual touch voltages generated in various locations are analyzed under scenarios of connecting or disconnecting the equipotential bonding between the ship and the shore using neutral grounding resistor (NGR) designs. This article delves into the scenarios of electric shock that may occur during the operation of an actual container ship’s shore power system. It evaluates whether various contact voltage values exceed current international standards and verifies the grounding design and safety voltage specifications of IEEE/IEC 80005-1. According to the results of this study, the use of NGR and protective earthed neutral (PEN) conductors in HVSC is crucial. This can limit fault currents, reduce touch voltage, and ensure the safety of personnel and equipment. Therefore, ensuring and monitoring equipment conductors and adopting NGRs of appropriate sizes are crucial elements in maintaining electrical safety in HVSC systems.

Low voltage cold and hot switching in nanoswitches cleaned by in situ oxygen plasma can achieve low stable contact resistance

Reliable nanoswitch operation requires low contact voltages and stable electrical contact resistance (ECR). Surface cleanliness is crucial to prevent nanomechanical switch failure, which can occur due to the presence of insulating adventitious hydrocarbon films. In situ O2 plasma cleaning is effective but oxidizes metal surfaces. Here, the noble metal Pt, which forms PtOx, is employed to form electrodes. Previous studies report on PtOx electrical resistivity, but the effects of PtOx evolution at contacting interfaces due to electrical and mechanical stimuli have not been explored. This study investigates the impact of PtOx on ECR at low contact voltages under hot switching, cold switching, and mechanical cycling conditions. An increase in ECR upon plasma cleaning indicates the presence of a resistive PtOx layer. After hot and cold switch cycling at applied voltages of 300 mV or less, a low stable ECR is achieved. A higher contact voltage accelerates ECR stabilization. The results are consistent with PtOx film volatilization, which is primarily due to Joule heating rather than mechanical rupture. This investigation advances the understanding of interface evolution in plasma-cleaned nanoswitches.

A workflow for predicting radiofrequency-induced heating around bilateral deep brain stimulation electrodes in MRI.

Heating around deep brain stimulation (DBS) in magnetic resonance imaging (MRI) occurs when the time-varying electromagnetic (EM) fields induce currents in the electrodes which can generate heat and potentially cause tissue damage. Predicting the heating around the electrode contacts is important to ensure the safety of patients with DBS implants undergoing an MRI scan. We previously proposed a workflow to predict heating around DBS contacts and introduced a parameter, equivalent transimpedance, that is independent of electrode trajectories, termination, and radiofrequency (RF) excitations. The workflow performance was validated in a unilateral DBS system. To predict RF heating around the contacts of bilateral (DBS) electrodes during an MRI scan in an anthropomorphic head phantom. Bilateral electrodes were fixed in a skull phantom filled with hydroxyethyl cellulose (HEC) gel. The electrode shafts were suspended extracranially, in a head and torso phantom filled with the same gel material. The current induced on the electrode shaft was experimentally measured using an MR-based technique 3cm above the tip. A transimpedance value determined in a previous offline calibration was used to scale the shaft current and calculate the contact voltage. The voltage was assigned as a boundary condition on the electrical contacts of the electrode in a quasi-static (EM) simulation. The resulting specific absorption rate (SAR) distribution became the input for a transient thermal simulation and was used to predict the heating around the contacts. RF heating experiments were performed for eight different lead trajectories using circularly polarized (CP) excitation and two linear excitations for one trajectory. The measured temperatures for all experiments were compared with the simulated temperatures and the root-mean-squared errors (RMSE) were calculated. The RF heating around the contacts of both bilateral electrodes was predicted with ≤ 0.29°C of RMSE for 20 heating scenarios. The workflow successfully predicted the heating for different bilateral DBS trajectories and excitation patterns in an anthropomorphic head phantom.

Study on the Applicability of Flexible Graphite Grounding Body and Grounding Module for 500kV Transmission Line in High Altitude Area

Sichuan-Tibet Railway Changdu-Linzhi section construction power supply project (Phase II) by Tibet Power Grid Co. 4900m), the mountain is treacherous, the foundation excavation is difficult (mostly rock foundation). Among them, 3 times across 35kV lines, 1 time across 220kV lines, 1 time across the Nujiang River, across the construction is more difficult. At present, China often use galvanized steel, galvanized copper and other traditional grounding materials, due to corrosion phenomenon caused by the increase in grounding resistance, affecting the frequency current, lightning current dispersion, but also cause local stride voltage and contact voltage does not meet the requirements of the regulations, generally in 8 years need to be replaced, which greatly increases the construction cost. In order to ensure the safe operation of power equipment and the safety of staff operation, stable and highly reliable grounding materials are needed. In recent years, flexible graphite material is widely used in grounding engineering, which has good electromagnetic characteristics and strong chemical stability, not easy to be eroded by the environment, and can operate in the grounding of power equipment in a long-term and stable manner. In this paper, the soil geological structure and typical line tower grounding resistance in Tibetan area are tested and analyzed, and the flexible graphite grounding material is applied to the grounding transformation of line tower in combination with local problems in Tibet, which can reduce the burial depth of grounding electrode, and compared with the solution of using traditional grounding material, it can reduce the cost and improve the project progress, and help the construction unit and construction unit to control the budget and construction period.

Lightning-strike induced acute injury: A case report

Lightning strike injury is a rare but a devastating lifethreatening condition affecting virtually all tissues and solid organs of the body. This can be attributed to the various energy transmission mechanisms from lightning strikes. This include ground strike, contact voltage, side flash, wire-mediated lightning, direct strike and weak upper streamer. Acute lung injury following lightning strike is an uncommon presentation which can manifest as pulmonary oedema, alveolar haemorrhage, pulmonary contusion and acute respiratory distress syndrome. This is a case report of a 15-year-old female, who presented to the Emergency CC –BY 4.0 unit following a lightning strike injury. She presented in coma from the referral centre, markedly dyspnoeic, and eventually admitted into the intensive care unit on account of respiratory failure. Chest radiograph findings showed features in-keeping with non- cardiogenic pulmonary oedema. She was mechanically ventilated, placed on steroids, hydrated, and given antibiotics. Following treatment, respiratory distress resolved and she regained full consciousness. She was discharged home after 11 days of admission.

Stray Currents in Livestock Farming: Electrical Diagnosis in Farms

For several years, farmers have been questioning the effects of electromagnetic fields and stray electrical currents on the health of their animals. Observing changes in behavior or a decline in livestock productivity, farmers suspect that electrical installations on or near the farm may be responsible. Indeed, these systems can generate fault currents or stray currents, some of which may pass through the animals, affecting their well-being and productivity. To identify the origin and address this issue, an electrical diagnosis can be performed. In this study, diagnostics were carried out in eleven bovine farms considered “healthy”. These measurements included earth resistance equipment insulation resistance, continuity, leakage currents, as well as contact and step voltages, with some farms presenting non-conformities. This study will better understand the potential links between electrical installations and animal well-being, correlate the results of this study with those obtained in diagnostics conducted on farms experiencing such concerns and implement appropriate preventative and corrective measures.

A novel strategy to improve melting efficiency and arc stability in underwater FCAW via contact tip air chamber

The conventional method of underwater flux-cored arc welding (UWW-FCAW) is characterized by water around the welding torch's electric parts, the tubular wire, the molten pool and the workpiece. In the present work, underwater FCAW was performed by keeping the contact tip dry, inside a specially developed torch, and as in conventional underwater welding. The welds were carried out in a flat position at simulated depths of 0.3 m, 10 m and 30 m using a hyperbaric chamber. Welding electrical signals of voltage and current and contact tip temperature were acquired and processed to determine process behavior. As a result, the welding current was reduced when the contact tip was kept dry inside the torch because of the higher temperature achieved by resistance heating when it was insulated from the water. The ambient surrounding the contact tip interfered with the coefficient of heat transfer and, consequently, with its temperature. Welds performed with the dry contact tip also presented slight variations in bead shape parameters in different water depths. Higher arc stability was achieved by welding with the contact tip inside the air chamber, as minor variations of electric signals and fewer arc extinction events were observed compared to conventional underwater welds. The combination of improved arc stability with higher electrode temperature may also have contributed to minor porosity and smaller variation of the reinforcement along the weld bead.