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The present paper discusses a parameterized PSpice model of a full-bridge resonant inverter operating above the resonant frequency and an analog behavioral model of a control system with automatic regulation of the root-mean-square value of the output current. The control system is self-oscillating and allows for regulating the output power of the inverter by changing the transistors' turn-on time. Functional dependencies for designing a resonant inverter operating above its resonant frequency are defined, and parameterized descriptions of resonant circuit elements are performed. The theoretical studies are proved by computer simulation using PSpice for TI. [ABSTRACT FROM AUTHOR]

The artery of the induction coil (IC) in coreless induction furnaces is the water-cooling system. The IC conductor is a hollow tube of high electrical and thermal conductivity copper. This coil must be water-cooled to maintain its temperature at less than 75℃ during the heating process. The goal of this work is applying a proposed approach to reach the minimum required velocity of the coolant inside the IC tube, able to perform the required limit. The IC under study is designed to melt 25 kg of a scrap copper charge in a carbon crucible. Two sources of heat affect the IC, the crucible enclosing the melt and that due to the high current of high frequency passing through it. Then, this research is intended to avoid the rise of IC temperature and its damage during the process, by considering the electromagnetic-thermal analysis to determine the surrounding temperature at the charge's melting point without cooling, then the obtained data is used as an input to the thermal-fluid analysis step to calculate the required cooling time and the required velocity of the coolant. The calculations based on the difference in temperature between the outlet hot water and the inlet cold water. The mass flow rate and the required water velocity through the induction coil are mostly computed by both, the traditional analytical method and by numerical method. A comparison between them is discussed and suggestions of the required cooling arrangements are mentioned. Since, the cooling time is less than that of the melting process, then the cooling system can be adopted. The finite element method (FEM) is considered in this study by using the ANSYS computer package to model and simulate such a problem. [ABSTRACT FROM AUTHOR]

The article proposes a mathematical apparatus for modeling thermal processes occurring during induction heating of equipment elements during their soldering, in order to improve the quality of control of such a technological process. This work is devoted to the development of a software system module for modeling the assembly of a pipe-flange of rectangular section using the mathematical models developed by the authors. The application of the approach proposed in the article makes it possible to significantly reduce the labor and material costs for working out the technological process of induction soldering, both when correcting existing processes and when introducing new standard sizes and materials of products into production. The use of the proposed system in the complex solution of the problem of automation of the technological process of induction soldering will significantly improve both the quality of control of such a process and, as a consequence, the quality of the final product. [ABSTRACT FROM AUTHOR]

Design of autonomous inverters and estimation of their reliability is a complex task and requires a detailed analysis of parameters and operating modes. An autonomous inverters (AI) with energy dosing (ED) provide a constant power into load and are used in wide range of applications such as induction mass heating, induction melting, induction hardening, battery charging stations etc. In this case one conversion system has many various application, wide range of output changes and different environmental conditions. To estimate the reliability parameters of that type of converters is need to be defined electrical modes (or make detailed electromagnetic analysis), to define the all of the influencing factors (electrical and thermal modes, environmental conditions) into reliability parameters and build a probability modes to calculate the parameters such as: expected failures, expected repairs, reliability and availability and total down/up time. In presented paper is presented a reliability analysis of AI with ED with wide range of load changes used for various applications. As a result are presented reliability parameters and dependencies between load changes and reliability parameters. [ABSTRACT FROM AUTHOR]

Numerical simulation of thermophysical processes is carried out when the surface layer of a two-component metal (Fe-C) substrate is modified by refractory nanoscale particles when heated by a moving inductor in a non- stationary three-dimensional setting. Heating and melting of metal occurs when an induction high-frequency electromagnetic field (1200 kHz) is applied to its surface through a rectangular area. The distribution of electromagnetic energy on the surface of the substrate is uniform, and inside it is described by empirical formulas. We postulate in the model that the metal nanoscale particles are uniformly distributed in the melt. The boundary of the melting region is determined in the Stefan approximation, and the boundaries of the solidification region are defined according to Kolmogorov's theory of metal crystallization. The growth of the solid phase occurs on the surface of nanoparticles when the melt is undercooled. The model of non-equilibrium crystallization of the basic component of the alloy includes accounting for the dependence of the liquidus temperature on the concentration of dissolved carbon in the melt up to the eutectic point according to the non-equilibrium lever rule. In the simulation process, the temperature field distributions close to quasi-stationary, the size of the melting and crystallization zones, the kinetics of solid phase growth, and the change in the concentration of the alloying component in the solidifying metal were determined, consistent with the value of undercooling of the melt in the two-phase zone. The influence of the initial temperature of the substrate material on the shape of the molten pool and crystallization zones is considered. It is shown that an increase in the initial temperature of the substrate, which leads to a decrease in temperature gradients in the processing zone and, as a result, to a slowdown in the crystallization process, can serve as one of the ways to regulate the structure of the surface layer. [ABSTRACT FROM AUTHOR]

The article discusses a new type of induction installations for heating and electrophysical treatment of liquids with ionic electrical conductivity in electromagnetic fields. Methods of their calculation and optimization are proposed due to creation of local areas with large gradients of strength of electric and magnetic fields. Mathematical dependencies describing processes of phase transformation and mass transfer of scale-forming agents in gap of magnetic apparatus and in heat exchange device are derived. Calculated and experimental dependencies on effect on anti- scale efficiency of magnetic devices are determined. [ABSTRACT FROM AUTHOR]

With the use of numerical simulation, thermophysical processes are considered when modifying the surface layer of a metal in a moving substrate. The material is heated and melted under the influence of a continuous induction high-frequency electromagnetic field on the substrate surface through a rectangular region. The distribution of electromagnetic energy on the surface of the substrate is uniform, and within it is described by empirical formulas. It is assumed that nanoscale particles of the refractory compound penetrate, evenly distributed, into the melt during melting of the metal and act as active centers of crystallization. The boundary of the melting range is determined in the Stefan approximation, and the boundaries of the solid phase growth region are within the framework of Kolmogorov's theory of the crystallization of metals. Based on the results of calculations, the temperature field distribution, the size of the melting and crystallization zones, and the growth kinetics of the solid phase are estimated in the quasi-stationary approximation. The characteristics of induction heating have been determined, which make it possible to shorten the surface treatment time. The values of the specific power are obtained depending on the speed of the substrate in the range 1-3 cm/s, which make it possible to preserve the dimensions of the melting and modifying region unchanged. [ABSTRACT FROM AUTHOR]

Induction heating is a process of heat generation which uses metal conductors and the Joule effect. The induction heating process has many applications in industry, such as metal melting, preheating for forging operations, hardening, and welding. A model of induction heating is given by a coupled system of partial differential equations relating temperature field and magnetic potential. Precisely, a coupled system of Maxwell and heat equations is given in the workpiece, while in the exterior domain the Laplace equation for the magnetic potential is formulated. Finally, nonlinear boundary condition for the heat equation, transmission conditions and asymptotic condition for the magnetic potential are given. Solution of such coupled multifield problems requires advanced coupled numerical methods. Therefore, in this paper we present a coupled numerical approach connecting Finite Difference Method and discrete potential theory. The use of discrete potential theory is motivated by the fact that asymptotic conditions are satisfied exactly on the discrete level. Thus, a general scheme for the coupled numerical method is presented in this paper. [ABSTRACT FROM AUTHOR]

With the development of modern induction heating power sources in the direction of high frequency and large capacity, the design and production of induction heating power supplies are increasingly demanding for switching devices. The soft switch technology keeps the voltage or current at zero during the switching process, which can weaken or even eliminate the switching loss. Its research and design are concerned by researchers in related fields. This paper introduces the related principle of soft-switching technology. Based on diode-rectified voltage-type induction heating power supply, a soft-start control circuit for induction heating power supply is designed, and the simulation model is built for the whole power supply system. Then it is studied in MATLAB/Simulink simulation environment. The simulation results were analyzed and compared with the theoretical values. [ABSTRACT FROM AUTHOR]

The phenol resins have been used in a wide range of field because of low cost, good mechanical properties and good heat resistance. However, since the impact strength is lower than other resins, they are often used as fiber reinforced composites. A way of improving the impact strength and the mechanical properties is to leave long fibers in a product. There are several molding methods of forming products using long fibers, but their cycle times are relatively long. Therefore, they are not suitable for mass production. The purpose of this study is to establish a new molding system which can leave long fibers in a product and whose cycle time is short. The new molding system is based on transfer molding. Unlike general transfer molding, there is an injection unit for supplying a melted material into the transfer pot. Furthermore, in the injection unit, induction heating is used as a heating device and there is no nozzle at the tip of the cylinder. In the molding process, the cylinder in the injection unit is rapidly heated by induction heating and long-fiber pellets are melted by a screw within the cylinder. The resin tends to be curing because the temperature of the cylinder is high by induction heating, so there is no nozzle in order to prevent curing. The melted material is injected into the transfer pot in the mold and molded by pushing the material into a cavity with a plunger like general transfer molding. By using induction heating, the cylinder is heated and resin is melted rapidly. Thus, metering time is short and the fiber length is left long. Generally, a band heater is wrapped around the cylinder, so it takes time to cool the cylinder. On the other hand, the cylinder of the new molding system is uncovered the band heater, so the cylinder can be cooled quickly and it can immediately shift to the next cycle. Because of short time to heat and cool the cylinder, the new molding system can continuously mold a longfiber product within 3 minutes. [ABSTRACT FROM AUTHOR]

A single high magnetic field pulse of 60 T can be used to initiate chemical reactions between Bisphenol-A based Polycarbonate and Octadecylamine. Therefore, susceptor structures are needed for a localized heating of the interphase between the reactive polymer materials. As susceptors, stable gold structures were developed and produced by physical vapor deposition. The gold structures were characterized morphologically and electrically to optimize their heating efficiency. [ABSTRACT FROM AUTHOR]

In the present work, different graphene derivatives were prepared and characterized envisaging their use as susceptors for magnetic high-field induction heating at polymer interfaces. For optimization of this new kind of polymer bonding method, first graphene oxide (GO) with different degrees of oxidation were synthetized from graphite through a modified Hummers method. Then, the reduction of GO was achieved using dopamine hydrochloride to obtain polydopamine-coated graphene oxide (PDA-GO). Finally, these graphene derivatives were characterized by X-Ray Photoelectron Spectroscopy (XPS) and Raman Spectroscopy. [ABSTRACT FROM AUTHOR]

The paper suggests a mathematical model of high-temperature synthesis of an intermetallic in the regime of dynamic thermal explosion in combination with mechanical loading. The flow of the powder mixture is described by the model of viscous liquid. The problem of steel cylindrical mold heating includes heat conductivity equations for involved materials: reactive mixture and mold walls. The model accounts for heat release from external heating and chemical reactions. It is assumed that additional external mechanical load can accelerate the synthesis. The chemical reactions comprise the combined scheme that corresponds to the synthesis of Ni3Al intermetallic from the stoichiometric mixture of Ni + Al. The kinetic law takes into account an appreciable reduction in the reaction rate caused by the layer of synthesized product. [ABSTRACT FROM AUTHOR]

Some numerical calculations of eddy current heating (with using induction plate) were carried out for different layered materials. The 3D finite element method (FEM) was used. The calculations were made with using the eddy current module of a Maxwell/ANSYS software. In order to accelerate the calculations, some simplified numerical models, including symmetries, were tested and compared with a more complex FEM model. Thanks to some symmetries of the analyzed object, it was possible to decrease the calculation time significantly (more than 10 times). With using the simplified model, it was possible to improve the discretization mesh, which decreased the calculation error. Three different materials were analyzed: stainless steel, copper+stainless steel and aluminium+stainless steel. For all materials the eddy current losses, eddy current and magnetic flux density distribution were determined. [ABSTRACT FROM AUTHOR]

One of the perspective ways to improve the operational properties of parts of machines during induction treatment of their surfaces is the modification of the melt by specially prepared nanoscale particles of refractory compounds (carbides, nitrides, carbonitrides, etc.). This approach allows us to increase the number of crystallization centers and to refine the structural components of the solidified metal. The resulting high dispersity and homogeneity of crystalline grains favorably affect the quality of the treated surfaces. 3D numerical simulation of thermophysical processes in the modification of the surface layer of metal in a moving substrate was carried out. It is assumed that the surface of the substrate is covered with a layer of specially prepared nanoscale particles of a refractory compound, which, upon penetration into the melt, are uniformly distributed in it. The possibility of applying a high-frequency electromagnetic field of high power for heating and melting of a metal (iron) for the purpose of its subsequent modification is investigated. The distribution of electromagnetic energy in the metal is described by empirical formulas. Melting of the metal is considered in the Stefan approximation, and upon solidification it is assumed that all nanoparticles serve as centers for volume-sequential crystallization. Calculations were carried out with the following parameters: specific power p0= 35 and 40 kW/cm2 at frequency f = 440 and 1200 kHz, the substrate velocity V = 0.5-2.5 cm/s, the nanoparticles' size is 50 nm and concentration Np = 2.0·109 cm-3. Based on the results obtained in a quasistationary formulation, the distribution of the temperature field, the dimensions of the melting and crystallization zones, the change in the solid fraction in the two-phase zone, the area of the treated substrate surface, depending on the speed of its movement and induction heating characteristics were estimated. [ABSTRACT FROM AUTHOR]

2D numerical modeling of the processes during the alloying of the substrate surface metal layer is carried out. Heating, phase transition, heat and mass transfer in the molten metal, solidification of the melt are considered with the aid the proposed mathematical model. Under study is the applicability of the high-frequency electromagnetic field impulse for metal heating and melting. The distribution of the electromagnetic energy in the metal is described by empirical formulas. According to the results of numerical experiments, the flow structure in the melt and distribution of the alloying substances is evaluated. [ABSTRACT FROM AUTHOR]

Gear forming by cross rolling with local induction heating process is an alternative method to manufacturing large diameter gear parts, and the distribution of the temperature has a great influence on the subsequently gear forming process. To get a satisfied temperature distribution of the heated workpiece, the model of induction heating process by coupling the electromagnetic and thermal field combing the rotational motion is established and the heating rate and temperature distribution along the axial and circumferential has been investigated. Moreover, corresponding experiment was carried out and the heating parameter and temperature distribution were measured by multi meter and infrared thermographic imaging. According to the comparison of the experimental and simulation results, the established model was verified and the simulation results are reliable. [ABSTRACT FROM AUTHOR]

Current research activities at the Institute for Metal Forming Technology (IFU) of the University of Stuttgart are focusing on the manufacturing of hybrid components using semi-solid forming strategies. As part of the research project "Hybrid interaction during and after thixoforging of multi-material systems", which is founded by the German Research Foundation (DFG), a thixoforging process for producing hybrid components with cohesive metal-to-metal connections is developed. In this context, this paper deals with the numerical simulation of the inductive heating process of hybrid semi-finished materials, consisting of two different aluminium alloys. By reason of the skin effect that leads to inhomogeneous temperature distributions during inductive heating processes, the aluminium alloy with the higher melting point is thereby assembled in the outer side and the alloy with the lower melting point is assembled in the core of the semi-finished material. In this way, the graded heat distribution can be adapted to the used materials' flow properties that are heavily heat dependent. Without this graded heat distribution a proper forming process in the semi-solid state will not be possible. For numerically modelling the inductive heating system of the institute, a coupling of the magnetostatic and the thermal solver was realized by using Ansys Workbench. While the electromagnetic field and its associated heat production rate were solved in a frequency domain, the temperature development was solved in the time based domain. The numerical analysis showed that because of the high thermal conductivity of the aluminium, which leads to a rapid temperature equalization in the semi-finished material, the heating process has to be fast and with a high frequency for produce most heat in the outer region of the material. Finally, the obtained numerical results were validated with experimental heating tests. [ABSTRACT FROM AUTHOR]

One of the perspective ways to improve the operational properties of parts of machines during induction treatment of their surfaces is the modification of the melt by specially prepared nanoscale particles of refractory compounds (carbides, nitrides, carbonitrides, etc.). This approach allows us to increase the number of crystallization centers and to refine the structural components of the solidified metal. The resulting high dispersity and homogeneity of crystalline grains favorably affect the quality of the treated surfaces. 3D numerical simulation of thermophysical processes in the modification of the surface layer of metal in a moving substrate was carried out. It is assumed that the surface of the substrate is covered with a layer of specially prepared nanoscale particles of a refractory compound, which, upon penetration into the melt, are uniformly distributed in it. The possibility of applying a high-frequency electromagnetic field of high power for heating and melting of a metal (iron) for the purpose of its subsequent modification is investigated. The distribution of electromagnetic energy in the metal is described by empirical formulas. Melting of the metal is considered in the Stefan approximation, and upon solidification it is assumed that all nanoparticles serve as centers for volume-sequential crystallization. Calculations were carried out with the following parameters: specific power p0= 35 and 40 kW/cm2 at frequency f = 440 and 1200 kHz, the substrate velocity V = 0.5-2.5 cm/s, the nanoparticles' size is 50 nm and concentration Np = 2.0.109 cm-3. Based on the results obtained in a quasistationary formulation, the distribution of the temperature field, the dimensions of the melting and crystallization zones, the change in the solid fraction in the two-phase zone, the area of the treated substrate surface, depending on the speed of its movement and induction heating characteristics were estimated. [ABSTRACT FROM AUTHOR]

2D numerical modeling of the processes during the alloying of the substrate surface metal layer is carried out. Heating, phase transition, heat and mass transfer in the molten metal, solidification of the melt are considered with the aid the proposed mathematical model. Under study is the applicability of the high-frequency electromagnetic field impulse for metal heating and melting. The distribution of the electromagnetic energy in the metal is described by empirical formulas. According to the results of numerical experiments, the flow structure in the melt and distribution of the alloying substances is evaluated. [ABSTRACT FROM AUTHOR]

This paper presents our proposed frequency sweeping excitation and spectrogram method (FSES method) by a magnetic sensor for non-destructive testing of hardened low carbon steels. This method can evaluate the magnetic properties of low carbon steels which were changed after induction heating treatment. It was examined by our proposed method that the degrees of yield strength of low carbon steels were varied depending on hardened conditions. Moreover, it was made clear that the maximum magnetic field strength, Hmax, derived from the measured B-H loops was very sensitive to the hardening if the surface of the samples were flat. [ABSTRACT FROM AUTHOR]

In this article the reinforced concrete non-destructive evaluation using active thermography is discussed. There are several aspects of possible non-destructive testing of mentioned structures. One of them is the detection and assessment of the reinforcement itself. In case of active thermography, the external energy source has to be used to induce the thermal response of the inspected specimen. Here, authors propose two different techniques: microwave heating and induction heating. In this article authors will present several experimental results which will allow to compare mentioned two techniques of heating. suitability of each one to assess the reinforced concrete by using the active thermography will be discussed. [ABSTRACT FROM AUTHOR]

In this article the reinforced concrete non-destructive evaluation using active thermography is discussed. There are several aspects of possible non-destructive testing of mentioned structures. One of them is the detection and assessment of the reinforcement itself. In case of active thermography, the external energy source has to be used to induce the thermal response of the inspected specimen. Here, authors propose two different techniques: microwave heating and induction heating. In this article authors will present several experimental results which will allow to compare mentioned two techniques of heating. suitability of each one to assess the reinforced concrete by using the active thermography will be discussed. [ABSTRACT FROM AUTHOR]

The article addresses results of tests of performance characteristics of a tube bend made of the 15NiCuMoNb5-6-4 steel, the latter being for manufacture of feed water pipelines used in power engineering systems. The tube bend was developed by bending with local induction heating, and the optimum tube bending parameters were established based on numerical simulations of the bending process. The mechanical properties of the tube bend were attained through quenching and tempering. Tests of mechanical properties were conducted using samples collected at different zones of the tube bend (the straight one as well as those subject to tension and compression), and compared with properties of the as-delivered tube material. The established basic mechanical properties of the tube bend, required under the applicable standards, were supplemented with results of low-cycle fatigue and creep tests, the purpose of which was to acquire information on the tube bend material service life under conditions of steady and unsteady operation of a power unit. [ABSTRACT FROM AUTHOR]

Induction or eddy current thermography is used to detect surface cracks in ferritic steel. The technique is applied to detect surface cracks in rails from a moving test car. Cracks were detected at a train speed between 2 and 15 km/h. An automated demonstrator system for testing railway wheels after production is described. While the wheel is rotated, a robot guides the detection unit consisting of inductor and infrared camera over the surface. [ABSTRACT FROM AUTHOR]

In this paper we present a high performance protection circuit designed for the power electronics applications where the load currents can increase rapidly and exceed the maximum allowed values, like in the case of high frequency induction heating inverters or high frequency plasma generators. The protection circuit is based on a microcontroller and can be adapted for use on single-phase or three-phase power systems. Its versatility comes from the fact that the circuit can communicate with the protected system, having the role of a "sensor" or it can interrupt the power supply for protection, in this case functioning as an external, independent protection circuit. [ABSTRACT FROM AUTHOR]

In this paper the method of identification of the parameters of the volumetric heat source simulating the induction heating is presented. The presented method allows one to estimate the power and radius of the heat source for the superficial hardening process with the moving heat source. The solution described in this paper can successfully support the work of the specialist on improvement of numerical simulation and also significantly reduce the time required to estimate the parameters of the boundary conditions. The accuracy of the solution of the presented method is independent from the empirical models of boundary conditions during heating process. It is also much more universal. In the paper the analysis of learning process for artificial neural network (ANN) is described. The error of estimated values by ANN is presented. The precision of presented model is tested for a different tasks. [ABSTRACT FROM AUTHOR]

Hot-roller warm rolling process is expected to achieve a breakthrough in solving the problem of high quality rolling for difficult deformed metals. In this paper roll surface induction heating was studied based on the finite element theory of electromagnetic-thermal coupling and experiment. The law of temperature field for a static roll in induction heating process was analyzed by FEM. The results show that roll surface temperature can achieve 721°C at 48s under 20000Hz power frequency, 350×104A/m2 current density, due to the skin effect on roll surface. Using a special induction coil in the laboratory, an experiment of roll induction heating was carried out with the same process parameters. The calculated results of temperature on roll surface agree well with the measured value. [ABSTRACT FROM AUTHOR]

Multiply charged ions to be used prospectively are produced from solid pure material in an electron cyclotron resonance ion source (ECRIS). Recently a pure iron source is also required for the production of caged iron ions in the fullerene in order to control cells in vivo in bio-nano science and technology. We adopt directly heating iron rod by induction heating (IH) because it has non-contact with insulated materials which are impurity gas sources. We choose molybdenum wire for the IH coils because it doesn't need water cooling. To improve power efficiency and temperature control, we propose to the new circuit without previously using the serial and parallel dummy coils (SPD) for matching and safety. We made the circuit consisted of inductively coupled coils which are thin-flat and helix shape, and which insulates the IH power source from the evaporator. This coupling coils circuit, i.e. insulated induction heating coil transformer (IHCT), can be move mechanically. The secondary current can be adjusted precisely and continuously. Heating efficiency by using the IHCT is much higher than those of previous experiments by using the SPD, because leakage flux is decreased and matching is improved simultaneously. We are able to adjust the temperature in heating the vapor source around melting point. And then the vapor pressure can be controlled precisely by using the IHCT. We can control ±10K around 1500°C by this method, and also recognize to controlling iron vapor flux experimentally in the extreme low pressures. Now we come into next stage of developing induction heating vapor source for materials with furthermore high temperature melting points above 2000K with the IHCT, and then apply it in our ECRIS. [ABSTRACT FROM AUTHOR]

During inductive-thermographic inspection, an eddy current of high intensity is induced into the inspected material and the thermal response is detected by an infrared camera. Anomalies in the surface temperature during and after inductive heating correspond to inhomogeneities in the material. A finite element simulation of the surface crack detection process using active thermography with inductive heating has been developed. The simulation model is based on the finite element software ANSYS. The simulation tool was tested and used for investigations on steel components with different longitudinal orientated cracks, varying in shape, width and height. This paper focuses on surface connected longitudinal orientated cracks in austenitic steel. The results show that depending on the excitation frequency the temperature distribution of the material under test are different and a possible way to measure the depth of the crack will be discussed. [ABSTRACT FROM AUTHOR]

An increasing number of problems in mechanics and physics involves multiphysics coupled problems. Among these problems, we can often find electromagnetic coupled problems. Electromagnetic couplings may be involved through the use of direct or induced currents for thermal purposes-in order to generate heat inside a work piece in order to get either a prescribed temperature field or some given mechanical or metallurgical properties through an accurate control of temperature evolution with respect to time-, or for solid or fluid mechanics purposes-in order to create magnetic forces such as in fluid mechanics (electromagnetic stirring,...) or solid mechanics (magnetoforming,...). Induction heat treatment processes is therefore quite difficult to control; trying for instance to minimize distortions generated by such a process is not easy. In order to achieve these objectives, we have developed a computational tool which includes an optimsation stage. A 3D finite element modeling tool for local quenching after induction heating processes has already been developed in our laboratory. The modeling of such a multiphysics coupled process needs taking into account electromagnetic, thermal, mechanical and metallurgical phenomenon-as well as their mutual interactions during the whole process: heating and quenching. The model developed is based on Maxwell equations, heat transfer equation, mechanical equilibrium computations, Johnson-Mehl-Avrami and Koistinen-Marburger laws. All these equations and laws may be coupled but some coupling may be neglected. In our study, we will also focus on induction heating process aiming at optimising the Heat Affected Zone (HAZ). Thus problem is formalized as an optimization problem-minimizing a cost function which measures the difference between computed and optimal temperatures-along with some constraints on process parameters. The optimization algorithms may be of two kinds-either zero-order or first-order algorithms. First-order algorithms have proved their efficiency for induction heating processes. However, zero-order algorithms-such as evolution strategy algorithms-are better at reaching global minimal values for cost functions. We use here a method based on Efficient Global Optimization algorithm developed by Jones which is an optimization procedure assisted by a meta model. We will present some results obtained with our numerical tool on the preheating of a part before forging. We will focus on the control of temperature profile at the end of induction heating stage. [ABSTRACT FROM AUTHOR]

A new moulding process for manufacturing micro parts made from high viscosity polymers has been developed as a result of a feasibility study. The process basically involves compression moulding of a polymeric preform by heating it up to its semi-solid state, i.e. between its glass transition temperature and melting temperature. The apparatus is made up of three main parts: a forming device, a single cavity micro mould and an induction heating system. The processing technique was successfully tested in the manufacturing of 10 mm round discs with a flange and inner bore using high viscosity polymers such as polyphenylene sulfide (PPS), polyetheretherketone (PEEK), ultra-high molecular weight polyethylene (UHMW PE) and polytetrafluoroethylene (PTFE). In a further miniaturization study, U-shaped micro seals with an outer diameter up to 2.5 mm were also successfully manufactured from non-injection mouldable PTFE. Thus, the new process is a realistic alternative technique to the existing micro moulding processes with respect to its capability to process a huge variety of polymers, even ultra high viscosity materials and the possibility to create micro parts with non-uniform wall thickness distributions. [ABSTRACT FROM AUTHOR]

The design and optimization of the parameters of heating coil is very important for the analytical analysis of high frequency inverter fed induction cooker. Moreover, accurate prediction of high frequency winding loss (i.e., losses due to skin and proximity effects) is necessary as the induction cooker used in power electronics applications. At high frequency current penetration in the induction coil circuit is very difficult for conducting wire due to skin-effect. To eradicate the skin effect heating coil is made up of bundle conductor i.e., litz wire. In this paper inductances and AC resistances of a litz-wire are calculated and optimized by considering the input parameters like wire type, shape, number of strand, number of spiral turn, number of twist per feet of heating coil and operating frequency. A high frequency half bridge series resonant mirror inverter circuit is used in this paper and taking the optimum values of inductance and ac resistance the circuit is simulated through PSPICE simulations. It has been noticed that the results are feasible enough for real implementation. [ABSTRACT FROM AUTHOR]

Eddy current thermography is a relatively new inspection technique that takes advantage of the electromagnetic induction phenomenon to generate heat in electro conductive materials during inspection. An interesting advantage of eddy current heating compared to classical optical or ultrasonic heating is that the excitation source is smaller and can be conveniently shaped in order to provide energy efficient localized heating. Such excitation source is more suitable for the development of portable instruments and to perform field inspections. In this paper, finite element modeling (FEM) is used to optimize the eddy current coil configuration in terms of heating power efficiency. The performances of air-core coils, normally used in eddy current thermography, and a new field concentrator coil are compared and discussed. FEM results demonstrate that the proposed field concentrator coil improves the magnetic coupling with the inspected material and requires less energy than air-core coils to generate the same temperature variation. [ABSTRACT FROM AUTHOR]

The article presents a research study which presents mathematical model and robust controller that provides a uniform heating of a body, subjected to induction heating. The mathematical model includes solving the electromagnetic and heating problems. Under the study, the FE method is utilized and the entire model is reduced to a system of ODEs.

Multiply charged iron ions are produced from solid pure material in an electron cyclotron resonance (ECR) ion source. We develop an evaporator by using induction heating with the induction coil which is made from bare molybdenum wire and surrounding the pure iron rod. We optimize the shape of induction heating coil and operation of rf power supply. We conduct experiment to investigate reproducibility and stability in the operation and heating efficiency. Induction heating evaporator produces pure material vapor, because materials directly heated by eddy currents have non-contact with insulated materials which are impurity gas sources. The power and the frequency of the induction currents range from 100 to 900 W and from 48 to 23 kHz, respectively. The working pressure is about 10-4 to 10-3 Pa. We measure temperature of iron rod and film deposition rate by depositing iron vapor to crystal oscillator. We confirm stability and reproducibility of evaporator enough to conduct experiment in ECR ion source. We can obtain required temperature of iron under maximum power of power supply. We are aiming the evaporator higher melting point material than iron. [ABSTRACT FROM AUTHOR]

This paper presents a mathematical model of inductor electromagnetic and heating processes. There is introduced a controller as well, designed to provide a uniform heating supply. The mathematical model is used for a coupled electromagnetic-thermal analysis, since the electromagnetic analysis calculates the density of the heating source and the thermal analysis, that follows, utilizes the obtained heating source density to calculate a bounded heat transfer problem. The finite element method (FEM or FE method) is applied to reduce the problem to a linear system of ODEs and then, by the use of the control theory and the Glover-Doyle algorithm, it is demonstrated how to design a controller to establish a min temperature gradient change in the radial direction (a uniform heating mode). It is well-known that processes, such as the semi-solid forming and hot casting, require the max achievable uniform heating for a min period of time. [ABSTRACT FROM AUTHOR]

This paper examines the transient processes at turning on of the hybrid (series-parallel) current source inverter, using the program MatLab and Internet technologies. The obtained results allow the transient process to be assessed and its design to be done to obtain favourable turn on transient process. [ABSTRACT FROM AUTHOR]

This paper reports on a Tone Burst Eddycurrent Thermography (TBET) technique that uses short-time bursts of eddy-currents induced in conducting media to generate local heating inside the material. The transient diffusion of the heat inside the material, induced by pulsed/short-time induction heating, is imaged by measuring the transient temperature profiles on the surface of the material. The presence and characteristics of the defects inside the materials changes the surface temperature transients and thus can be used for the nondestructive evaluation (NDE) of conducting materials. Axisymmetric numerical models of the conventional transient thermography technique are used to benchmark the TBET technique. From the temperature profile data, temperature contrast information is obtained for the different defect depths. Temperature contrast data obtained for TBET, in this process, was compared with that obtained from conventional transient thermography data. It was found that the frequency of the eddy-current and, consequently, the skin-depth of the induced field play an important role in the effective utilization of this technique. Simulation details and the experimental results are presented in the paper. Possible advantages of TBET over conventional flash thermography are also discussed and supported by experimental data. [ABSTRACT FROM AUTHOR]

This paper presents the modeling of electromagnetic and heating processes in an inductor, where cylindrical ferromagnetic material has been placed. In the first part the electromagnetic mathematical problem is solved, as a result the power density is obtained. The power density takes part in the heat conduction equation. In the second part the thermal mathematical problem is solved, as a result the alteration of the temperature of the ferromagnetic material during the heating process is obtained. The parameters in both mathematical problems depend on the temperature. Because of that the stitching method is used for their finding. In [3, 4] the same mathematical problems are solved by the finite elements method. Comparing our results to those from [3] shows that they are similar. In contrast to [3, 4] our method allows the continuation of the analysis with the finding of the load power during the heating process. Thus result permits the determination of the load power alteration in the supplying inverter [1]. It is well-known that during the induction hardening it is necessary to maintain constant current amplitude in the load circuit of the inverter. So the next aim of this research is to build up a controller, based on the developed model, which will procure the necessary mode. [ABSTRACT FROM AUTHOR]

The different stages of metal forming processes often involve — beyond the mechanical deformations processes — other physical coupled problems, such as heat transfer, electromagnetism or metallurgy. The purpose of this paper is to focus on problems involving electromagnetic couplings. After a brief recall on electromagnetic modeling, we shall then focus on induction heating processes and present some results regarding heat transfer, as well as mechanical couplings. A case showing coupling for metallurgic microstructure evolution will conclude this paper. © 2007 American Institute of Physics [ABSTRACT FROM AUTHOR]

This report is a review of various initiation mechanisms in shock-melted explosives. This paper focuses on pre-ignition phenomena which cause a local temperature rise when a single void in HMX collapses under the action of a shock wave. Working in the melting regime, a timeline can be associated with the collapse of a single void, through a consideration of the time scales on which these mechanisms are activated. We have studied the hydrodynamic mechanism, in which the shock driven incident side of the void impinges on the shadow side of the void, and is brought to rest, causing a considerable temperature rise in the HMX. Clearly this mechanism comes into consideration after the void collapses completely. Another mechanism we studied is that of shear heating. It is important for extremely small voids, or for large voids after the void has been compressed to a sufficiently small scale. This mechanism comes into play after the void has collapsed, and a remnants of the void have been spun off into a vortex. The phenomenon of gas compression as the gas-filled void collapses is difficult to ignore, in view of the fact that large temperatures are generated by this mechanism. We speculate that this mechanism could be important if the initial, endothermic induction step in a reaction scheme is shorter than the time of collapse. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

Nanoparticles of Li0.35Zn0.30Co0.05Fe2.3O4 are prepared by sol-gel method and integrated in the non-magnetic matrix of multi-walled carbon nanotubes (MWCNT). Structural and microstructure analyses of the prepared samples are investigated by X-ray diffraction, high resolution transmission electron microscopy and Raman spectroscopy. To study the magnetic behavior, dynamic and static hysteresis loops are recorded. The microwave absorption properties of the nanoparticle integrated in MWCNT matrix are observed and analyzed. The ac induction heating efficiency of the nanoparticles is estimated by calculating specific absorption rate. [ABSTRACT FROM AUTHOR]

Traditionally, a dilatometer exploits dimensional change as a function of temperature/time to study phase transformations in materials. This limits its application where transition temperatures of two transformations overlaps. In this work, an inductively heated dilatometer has been used to delineate the magnetic transition occurring simultaneously with a structural transformation in a Fe-5.93at% Ni alloy by exploiting the fundamental principle of induction heating. [ABSTRACT FROM AUTHOR]