Arc Plasma Behavior Research Articles

Atomic-scale insight into arc plasma radiation-induced gassing materials ablation: photothermal decomposition behavior

In this study, we present a novel computational atomistic study of the photothermal decomposition behavior of arc plasma on radiation-induced gassing materials ablation, studying a polyamide 66 (PA66) system using reactive force field (ReaxFF) molecular dynamics (MD). We determine the infrared (IR) vibrational frequency of the PA66 permanent molecular dipole using MD and then computationally impose an electric field at the same frequency to simulate photothermal decomposition by IR, verifying our observations with gas chromatography-mass spectrometry (GCMS) of experimental decomposition. MD indicates that photothermal decomposition reaction is dominated by either cleavage at low temperature or cyclization at high temperature. At low temperature, initial chain scission takes place at the two amide C–N, and the remaining chains break down into a variety of molecular fragments and free radicals. Further increasing the temperature stabilizes a variety of branched chain structures via cyclization, debranching and polymerization, with further cleavage forming hydrocarbons and volatile small molecule gases. Overall, H2, CO, H2O, alkanes and alkenes are the main gaseous products and cyclic structures (especially nitrogen-containing three-membered ring) are the main solid products during the photothermal decomposition of PA66, and their formation results from a variety of complex chemical reactions. The results of MD cover the experimental observations of GCMS, demonstrating that this computational methodology helps us understand the molecular breakdown mechanisms of arc plasma radiation-induced gassing materials. We also discuss the physical mechanism by which the main gas can accelerate arc quenching, and the importance and necessity of using electric fields to simulate IR photothermal decomposition of arc-induced ablation.

Progress in the arc plasma temperature measurement and its finite element analysis in pulsed MIG welding process

The article focuses on the state of the art review of progress in the arc plasma temperature measurement, a lesser-explored area of pulsed metal inert gas welding because of technological and economic constraints. However, investigation of the arc plasma temperature is paramount for precise prediction in welding process simulation models. The dynamic behavior of arc plasma in the pulsed MIG welding process is a multifaceted heat mass transfer phenomenon involving chemical, electro-magnetic, and fluid dynamics.In the pulsed MIG welding process thermal, mechanical, and electrical phenomenon co-exists and results in the formation of all four states of matter in a very small fusion sphere. The paper throws light on the latest investigations on the importance of precise measurement of arc plasma temperature, techniques used for measurement of the arc plasma, and challenges associated with pulsed MIG welding. Moreover, unanswered characteristics of the welding fusion sphere with future directions are discussed in the challenges section. It will serve as a guide to researchers and industry for developing better insight for performing pulsed MIG welding, developing accurate numerical models of pulsed MIG welding, and will also provide sufficient base to focus on thrust area of pulsed MIG welding.

Visualization of arc plasma and molten wire behavior in CO2 arc welding process by three-dimensional numerical simulation

In the CO2 welding process, a consumable wire electrode is used and metal transfer phenomena are involved. However, when the arc current is high, the molten wire behavior becomes unstable, and it leads to a large degree of spattering. In this study, a three-dimensional unified model comprising both the arc plasma and the molten wire was constructed, and the behavior of them was visualized using numerical simulations. The transfer mode is regarded as globular transfer in the numerical simulation with an arc current of 300 A. In addition, when the molten metal droplet becomes asymmetrical, the molten wire is pushed up by the arc plasma, and the transfer mode becomes repelled transfer. The temperature distribution and the metal vapor concentration distributions in the symmetrical and asymmetrical cases are significantly different. When the droplet shape is close to symmetrical, the metal vapor concentrates at the center of the arc plasma and the overall temperature of the arc plasma decreases. In contrast, when the droplet shape is asymmetrical, the high-temperature region and metal vapor region are separated. The numerical results showed that the properties of the arc plasma are significantly changed depending on the molten wire behavior.

Numerical simulations of arc plasma under external magnetic field-assisted gas metal arc welding

The arc plasma behavior for gas metal arc welding (GMAW) with an external compound magnetic field was numerically investigated. A three-dimensional finite element model for the external magnetic field (EMF) and a three-dimensional finite volume model for the arc plasma were established. The effects of the EMF on the redistribution of the temperature, fluid flow, pressure, and electromagnetic force in the arc plasma were compared with traditional GMAW under the same welding parameters. The control mechanism of the external compound magnetic field on the arc plasma behavior was analyzed. The results show that the magnitude of the additional electromagnetic force was much lower than that of the self-induced electromagnetic force, but it caused forward inclination and periodic swinging of the arc plasma. When an EMF was applied, the peak temperature decreased, and the temperature distribution was more uniform. The peak pressure was also much smaller than that without an applied EMF.

Lyapunov exponent analysis for the evaluation of hybrid laser double-arc welding process stability.

Hybrid laser double-arc welding is a complicated process with many random and uncertain influencing factors because of the interactions of energy, forces, and fields. The wire spacing is one of the main factors affecting the coupling behavior of laser and arc plasma and the stability of welding process. However, it is difficult to establish a precise mathematical model for evaluation of welding stability. In this paper, the largest Lyapunov exponent (LLE) of characteristic currents during the welding process under different wire-wire distances were numerically evaluated by the phase space reconstruction technique. Synchronous high-speed photography was adopted to observe arc shape and droplet transfer. The experimental and calculated results indicate that hybrid laser double-pulsed arc welding is a complex process of chaos. The LLE can provide a criterion for welding stability and can agree well with the observation of electrical signal, arc shape, and droplet transfer. Research results are needed to understand the welding process and to guarantee a stable and safe joining.

Numerical simulation of arc plasma and molten metal behavior in gas metal arc welding process

Numerical simulation of arc plasma and molten metal behavior in gas metal arc welding process

Numerical simulation of metal transfer in pulsed-MIG welding

Pulsed currents of various shapes have been employed to control the metal transfer phenomena. In the present study, a simulation model including both the arc plasma and the metal transfer is constructed, and their behaviors in pulsed-MIG arc welding are numerically investigated. When the peak current is set to 450 A and the peak time is set to 1.5 ms, only a single droplet is transferred per pulse. The numerical model can indicate the metal transfer and arc plasma behavior depending on the pulse shape. The temperature of the arc plasma increases rapidly at the early phase of the peak time, and consequently, the temperature of the wire electrode increases. After that, a large amount of the metal vapor generates from the wire tip, and the arc temperature decreases. These behaviors are periodic and can be controlled through the pulse shape. In addition, the appropriate pulse frequency depends on the surface tension of the wire electrode. This result shows that balance of the surface tension and the electromagnetic force is important to determine the droplet behavior. Therefore, in controlling the welding process, it is important to consider the properties of both the welding power source and the welding material.

Effect of arc distance on back appearance of root welding without backing plate by PMAG-TIG twin-arc welding

A novel pulsed metal active gas-tungsten inert gas (PMAG-TIG) twin-arc tandem welding process is applied to make stable back beads in the first layer weld during one-side multilayer welding without backing plate. The effect of different arc distances on the arc plasma behavior, molten pool flow pattern, and back appearance of root welding during the twin-arc tandem welding was studied. Results indicated that when arc distance is about 22 mm during the welding process, about 30% heat energy of the arc heat is utilized to melt the root face of base metal, and the rest heat energy acts on the molten pool. In this condition, the temperature distribution of the molten pool is appropriate, the flow of the front edge of the molten pool is suitable, the back appearance is continuous, stable, and uniform, and the back reinforcement and weld width is moderate. When arc distance is about 17 mm, more arc heat energy is utilized to melt the root face, the fluidity of the front edge of the molten pool is stronger, which leading to the back reinforcement is relatively larger. While arc distance is about 27 mm, less arc heat acts on the root face, the fluidity of the front edge of the weld pool is weak, resulting that in the back reinforcement is relatively small. This twin-arc tandem welding process is a new welding process giving high quality and efficiency in root welding for medium or thick plates.

Effect of external longitudinal magnetic field on arc plasma characteristics and droplet transfer during laser-MIG hybrid welding

The arc plasma behavior and droplet transfer are investigated using laser-MIG (metal insert gas) hybrid welding assisted by an external longitudinal magnetic field. The characteristic of arc plasma and droplet transfer can be recorded via combining sensing of the welding current and arc voltage with a high-speed imaging. Results indicated that the external longitudinal magnetic field had a significant impact on the arc shape, droplet formation, droplet size, and detaching. Under the magnetic field, the arc shape became a triangle gradually, and the off-axis arc and droplet gradually pointed to the axis of the filler wire. In addition, it has been found that with increasing the magnetic induction intensity, the droplet diameter and cycle time can be reduced. The mechanism of these phenomena was also further analyzed.

Numerical analysis of arc plasma behavior in double-wire GMAW

A three-dimensional mathematical model is developed describing arc plasma behavior in double-wire gas metal arc welding (DW-GMAW). The distribution of some physical quantities are completely investigated including arc temperature, arc pressure, velocity, current density, heat flux, magnetic flux density and electromagnetic force by solving conservation equations of mass, momentum, and energy, as well as part of Maxwell's equations. Meanwhile, a comparison study of arc plasma behavior between single-wire gas metal arc welding (SW-GMAW) and DW-GMAW is studied. It is found that due to the inter-attraction of double arcs, the arc plasma deflects to the middle of double welding wires, the maximum arc pressure decreases and the occurrence of welding defects such as undercut and humping is less in DW-GMAW than that in SW-GMAW. In addition, the effect of welding current on inclined angle, maximum temperature of arc plasma and heat flux on workpiece is investigated. The numerical results show good agreement with experimental ones and published literature, which proves that our model has relatively high reliability. The paper lays a foundation for true three-dimensional comprehensive modeling of DW-GMAW including arc plasma, metal transfer and weld pool.

Numerical Estimation of Arc Plasma Thermodynamic Parameters of Electromagnetic Macroparticles Launcher

An approach that allows estimation of the nonideal thermodynamic plasma parameters of the arc-driven electromagnetic launcher is proposed. Plasma is considered to be incompressible quasi-neutral gas with properties that vary only through the direction of motion. The 2-D distribution of the magnetic field in the vicinity of the arc plasma is studied. It is assumed that atoms are ionized once, and electrons, ions, and neutral atoms have the same temperature. The degree of ionization is calculated by the Saha equation, and the electrical conductivity of the arc plasma is calculated in the approximation of Spitzer. The resulting system of equations is complemented by the experimental data (current in the circuit of the launcher, the voltage drop at the launcher muzzle, the arc plasma length defined on the basis of B-dot probe traces). Arc plasma behavior is defined by the parameter of nonideality and temperature iteratively. The experimental arc plasma length is compared with the arc plasma length calculated by obtained relations. Statistical weights of atoms and ions are determined by interpolation of data given in the table which depend on the pressure and temperature. Processing of experimental data was done to estimate nonideal arc plasma parameters. It is shown that: 1) at a current density of about 80 kA/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , the character of temperature and conductivity dependence on the plasma current density is changed and 2) the electrical conductivity of arc plasma is described by the approximate dependence of σ(T) = σ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (T/T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> ) <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">n</sup> , where σ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> = 1.556 Ω <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> ; n = 1.988, T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> = 1000 K.

Three-dimensional numerical analysis of interaction between arc and pool by considering the behavior of the metal vapor in tungsten inert gas welding

A three-dimensional (3D) numerical analysis model of tungsten inert gas welding arc interacting with an anode material is presented based on the local thermodynamic equilibrium assumption and taking the behavior of metal vapor into account. The thermodynamic parameters and transport coefficients of plasma arc are dependent on the local temperature and metal vapor concentration. A second viscosity approximation is used to express the diffusion coefficient which describes the metal vapor diffuse in the argon plasma. The weld pool dynamic is described by taking into account the buoyancy, Lorentz force, surface tension, and plasma drag force. The temperature coefficient of the surface tension at the weld pool surface is considered in two ways: one is taken as a function of temperature with only oxygen being the active component, and the other is taken as a constant value. The distributions of temperature field and velocity field of arc plasma and weld pool, metal vapor concentration and current density in the arc plasma are investigated by solving the Maxwell equations, continuity equation, momentum conservation equation, energy conservation equation and the components of the transport equation. The influence of metal vapor on arc plasma behavior and that of arc plasma on the weld pool are studied and compared with the non-metal vapor results. It is shown that the distribution of Fe vapor concentrates around the weld pool surface. Metal vapor has obvious shrinkage effect on arc plasma, and weak influences on velocity and potential of the arc plasma. In addition, the metal vapor has a weak effect on the distributions of velocity and shear force on the weld pool surface and no obvious influence on the molten pool shape. We test two different methods to illustrate this point in the case with or without metal vapor. The method used for a variable temperature coefficient of surface tension allows the prediction of a depth-to-width ratio and weld pool shape in agreement with experimental result when taking the behavior of metal vapor into account. The results in this paper, obtained by simulation are in good agreement with experimental results and also with the simulation results by some other authors.

Numerical Study of the Arc Behavior in an Air DC Circuit Breaker Considering Turbulence

Arc plasma behavior plays an important role on the performance of the low voltage air dc circuit breakers (DCCB). A 3-D arc model considering the turbulence effect for a large arc chamber of an air DCCB is built. The arc evolution is described in detail by the temperature distribution.

Experimental Investigation on Breaking Characteristic of Load Switch in Medium High Voltage Ring Network Cabinet

This paper focuses on an experimental investigation of the arc plasma behavior in current breaking process of a certain type of 12kV ring network cabinet’s SF6 load switch. From the frames obtained by high-speed photography, the characteristic of the arc movement was revealed. According to analysis, the structure of load switch was optimized and its breaking capacity about transfer current was improved. This study may provide a reference for design and optimization of load switches.

Numerical Simulation of the Eddy Current Effects on the Arc Splitting Process

This paper focuses on a numerical simulation of the arc plasma behavior in the arc splitting process, considering the eddy currents in the electrodes and the splitter plate. Based on three-dimensional (3D) magneto-hydrodynamic (MHD) theory, a thin layer of nonlinear electrical resistance elements is used in the model to represent the voltage drop of plasma sheath and the formation of new arc root in order to include the arc splitting process in the simulation. In the arcing process, eddy currents in metal parts are generated by a time-varying magnetic field. The arc model is calculated with the time-varying magnetic field term, so that the eddy current effects can be considered. The effect of nonlinear permeability of a ferromagnetic material is also involved in the calculation. Using the simulation results for the temperature, velocity and current density distribution, the arc splitting process is analyzed in detail. The calculated results are compared with the simulation neglecting eddy currents.

3D Numerical Analysis of the Arc Plasma Behavior in a Submerged DC Electric Arc Furnace for the Production of Fused MgO

A three dimensional steady-state magnetohydrodynamic model is developed for the arc plasma in a DC submerged electric arc furnace for the production of fused MgO. The arc is generated in a small semi-enclosed space formed by the graphite electrode, the molten bath and unmelted raw materials. The model is first used to solve a similar problem in a steel making furnace, and the calculated results are found to be in good agreement with the published measurements. The behavior of arcs with different arc lengths is also studied in the furnace for MgO production. From the distribution of the arc pressure on the bath surface it is shown that the arc plasma impingement is large enough to cause a crater-like depression on the surface of the MgO bath. The circulation of the high temperature air under the electrode may enhance the arc efficiency, especially for a shorter arc.

Numerical Study on Arc Plasma Behavior During Arc Commutation Process in Direct Current Circuit Breaker

This paper focuses on the numerical investigation of arc plasma behavior during arc commutation process in a medium-voltage direct current circuit breaker (DCCB) contact system. A three-dimensional magneto-hydrodynamic (MHD) model of air arc plasma in the contact system of a DCCB is developed, based on commercial software FLUENT. Coupled electromagnetic and gas dynamic interactions are considered as usual, and a thin layer of nonlinear electrical resistance elements is used to represent the voltage drop of plasma sheath and the formation of new arc root. The distributions of pressure, temperature, gas flow and current density of arc plasma in arc region are calculated. The simulation results indicate that the pressure distribution related to the contact system has a strong effect on the arc commutation process, arising from the change of electrical conductivity in the arc root region. In DCCB contact system, the pressure of arc root region will be concentrated and higher if the space above the moving contact is enclosed, which is not good for arc root commutation. However, when the region is opened, the pressure distribution would be lower and more evenly, which is favorable for the arc root commutation.

Three-dimensional Time-dependent Numerical Analysis of SF6 Arc Plasma under Externally Applied Magnetic Field

Three-dimensional and time-dependent numerical analysis is carried out to understand the behavior of SF6 arc plasma under an externally applied magnetic field and to clarify the influence of the applied magnetic field on the electrical resistance of arc plasma and the pressure in a simple chamber. Numerical analysis takes into account the radiative heat loss, the Lorentz force, the Joule heating, and variations of thermodynamic properties and transport coefficients of SF6. Numerical results show that the arc plasma rotates and the length of arc column increases by the Lorentz force. The electrical resistance of arc plasma is increased by applying the magnetic field because of the following two factors: the increase in the length of arc column and the promotion of heat transfer attributed to the rotation of arc plasma. The promotion of heat transfer also causes an increase in the pressure in the chamber.

Numerical Analysis of Arc Characteristics of Splitting Process Considering Ferromagnetic Plate in Low-Voltage Arc Chamber

This paper focuses on the numerical investigation of arc plasma behavior during the arc motion and splitting process in a low-voltage quenching chamber. The 3-D mathematical model of air arc plasma considering the ferromagnetic splitter plate is built based on the magnetic hydrodynamics theory. The effect of the plasma sheath region, which is not in a state of local thermal equilibrium, is considered by an approximate method. The energy flux equations are introduced to describe the energy balance of the arc-metal interface. The arc motion is described in detail by the distributions of the temperature field and gas flow field in the arc chamber. The arc voltage is also calculated. The phenomenon that the arc root moving of the anode is faster than that of the cathode is observed in the calculation. Moreover, the arc-root formation on the splitter plate is analyzed according to the simulation results. Except for the numerical investigation, the experiment work is also carried out to support the simulation work.

Simulation of Arc Characteristics in Miniature Circuit Breaker

This paper focuses on the numerical investigation of arc plasma behavior in low-voltage circuit breaker with arc-splitting process included. A 3-D simulation model of a certain type miniature circuit breaker product is built and calculated, which is based on magnetohydrodynamics theory. Aside from coupled electromagnetic and gas dynamic interactions being considered as usual, a thin layer of nonlinear electrical resistance elements is used to represent the voltage drop of plasma sheath and the formation of new arc roots. Thus, the arc-splitting process with ferromagnetic plates can be included. Arc motion is described in detail by the temperature distribution. Some interesting phenomena are observed in the simulation, such as the arc root jumping from contact to arc runner, the arc back commutation before splitting into series arcs by metallic plates, new arc root formation in splitting process, and, finally, the arc go across the splitter plates in the chamber. Moreover, the simulation result is compared with experimental result, which shows good agreement.