A 3‐D Spatial Electromagnetic Field Analytical Model for a Domestic Induction Heating System With the Finite Dimension of the Electromagnetic Medium

Binocular vertical rectus muscle recession has not been formally evaluated in the correction of comitant vertical strabismus. Eight patients with stable comitant vertical strabismus for at least 6 months were included. All underwent recession of the superior rectus muscle of the hypertropic eye combined with an equal or nearly equal recession of the inferior rectus muscle in the hypotropic eye. On the day before surgery, on one of the first three postoperative days, and at one year postoperatively, ocular alignment in vertical and horizontal gaze directions were measured with simultaneous and alternate cover test at a viewing distance of 5 meters, and with the two dimensional Hess screen test. The field of single binocular vision was determined with a Goldmann perimeter. The Lang stereopsis chart was presented at the last follow-up visit. All patients were orthotropic at the last postoperative follow-up visit. In primary gaze, the degree of vertical and horizontal phoria diminished significantly. Normal alignment was achieved in nearly all gaze directions and stereopsis was reestablished. The field of single binocular vision enlarged after the surgery. Binocular vertical rectus muscle recession is an effective surgical approach for patients with comitant vertical ocular misalignment.

Domestic induction heating systems are usually modelled as an electrical equivalent composed of the series or parallel connection of an equivalent resistor and inductor. This model allows obtaining useful time-domain results in order to extract design conclusions for the power electronic converter. However, this model neglects the dependence of the equivalent electrical parameters with frequency. This dependence becomes a key parameter when the induction system varies the excitation frequency with the purpose of adapting the output power. In order to overcome this limitation, this study proposes a modelling strategy to take into account the influence of frequency divided into two steps. First, the frequency-dependent impedance is obtained by means of a finite-element analysis tool. Afterwards, a passive network composed of several inductors and resistors in series and parallel connection are used to fit the frequency response of the induction load. The proposed strategy allows obtaining a more accurate model of the induction heating load. Moreover, as there is no need to build previous prototypes, the design process is optimised. The feasibility of this proposal has been tested by comparing time-domain simulations with oscilloscope measurements in a real domestic induction heating system.

The addition of a secondary inductor with resonant capacitor directly beneath and attached to the small ferromagnetic cookware allows to improve induction heating adaptation of loads of different sizes to the primary inductor, extending load distance while avoiding increased power losses and stress on electronic components. The extended distance can be used to implement the glassless induction concept, where the typical ceramic glass is substituted by the kitchen surface itself. Finite Element Analysis simulations are carried out to determine the system impedance. A design is chosen to develop as a prototype. The prototype is tested under working conditions up to 1500 W at several distances to validate the simulations and design.

A mechanical loading technique for reliability assessment of flip-chip BGA interconnects was developed as a rapid alternative to traditional temperature cycling methods. Sinusoidal shear loading was used to accelerate fatigue cracking within the solder interconnects of a chip-scale test while shear force and circuit resistance were monitored in situ with resistance increases of 30% considered the point of failure in tested devices. Test parameters were selected and optimized by leveraging finite element analysis (FEA) simulations of mechanical cycling and temperature cycling to select shear force, frequency, and test duration such that the inelastic strain energy density (plastic work density per cycle) achieved in the mechanical cycling test agreed closely with that predicted by FEA for more traditional temperature cycling tests. These FEA simulations were conducted using Anand's constitutive material model to make accurate predictions of the inelastic strain energy density, accumulation per cycle, and therefore fatigue lifetimes of chip-scale devices containing Sn63/Pb37 solder interconnects using energy based fatigue models. With optimized test parameters, this mechanical loading method was able to induce the same inelastic strain energy density into the flip-chip interconnects as traditional temperature cycling (as predicted by FEA simulations). By monitoring resistance in situ, determinations were made as to the affects this amount of damage had on the performance and reliability of the studied device. Failure localization and crack visualization was achieved using MicroCT imaging to study interconnect cross-sections. Thus, the total amount of damage predicted for a thermal cycling test by FEA simulation can be generated in flip-chip interconnects at a much higher rate by utilizing the mechanical loading technique, reducing overall test time duration and associated testing costs. Assessments can then be made as to the impact the fatigue damage has had on the electrical performance of the device. Additionally, inexpensive mechanically analogous Si test vehicles were used to make predictions about the reliability of more expensive SiC devices using this mechanical cycling technique.

Tong type mechanisms have been used in industry to lift many types of loads where the clamping force generated in the tong mechanism along with friction and indentation prevent the load from slipping out of the tongs. There are several types of tong designs, lifted load geometries and levels of hardness resulting in numerous variations of clamping forces and grip/load geometries which makes the design of the tong mechanisms extremely challenging. The purpose of this work is to develop a Finite Element Analysis (FEA) simulation of the grip behavior under the multitude of variables that occur in the practical use of tongs to lift loads. Variables include tong mechanism geometry and load size resulting in different tong grip angles relative to the lifted load and resulting clamping force. Other variables include the hardness of the lifted load and the style of grips. With an FEA simulation methodology developed, a multitude of different variables affecting tong effectiveness can be evaluated. To verify the FEA simulation, a series of actual laboratory tests were conducted. These tests measured the load slip force as a function of clamping force, grip geometry, and load and grip hardness. Also measured was the grip indentation into the load and deflection versus slip force. A comparison of the results of the FEA simulation and the experimental tests is given. In some cases the correlation is good and in others more work is needed. A plan for further improvement of the FEA simulation technique is given.

The induction heating process at a domestic level is getting attention nowadays as this power converting topology ensures clean, reliable, flexible, and fast operation. The low input frequency is converted to required regulated high output frequency with indirect and direct power converting approaches. The circuit and control complexity and high conversion losses associated with indirect power converting approaches lower their uses for domestic induction systems. The direct ac-ac power conversion approach is one of the viable solutions for low and medium power level loads, especially for domestic induction heating loads. The circuit complexity, cost, and conversion losses of the direct power converting systems depend on the number of the controlled switching devices as each controlled switch requires one gate driving circuit and one isolated dc supply. Simplified pulse width modulation (PWM) switching control also lower their control effort. Therefore, in this article, a simplified direct ac-ac power converting approach is introduced for a high-frequency domestic induction heating system. Here, the regulation of the high output frequency is achieved by simply cascading the single-phase full-bridge rectifier with a full-bridge inverter with a simple control strategy. The characteristics of the developed topology are validated through simulation results of the Simulink-based platform and practical results of the developed practical setup.

Power requirement to the induction heating system varies during the heating process. A closed loop control is required to have a smooth control over the power. In this work, a constant frequency pulse density modulation based power tracking control scheme for domestic induction heating system is developed using the Fuzzy Logic Controller. In the conventional power modulation schemes, the switching losses increase with the change in the load. The proposed pulse density modulation scheme maintains minimum switching losses for the entire load range. This scheme is implemented for the class-D series resonant inverter system. Fuzzy logic controller based power tracking control scheme is developed for domestic induction heating power supply for various power settings. The open loop and closed loop simulation studies are done using the MATLAB/Simulink simulation tool. The control logic is implemented in hardware using the PIC16F877A microcontroller. Fuzzy controller tracks the set power by changing the pulse density of the gate pulses applied to the inverter. The results obtained are used to know the effectiveness of the fuzzy logic controller to achieve the set power.

Premature failures of stator insulation account for a large percentage of repairs of marine generator systems. The failure mechanisms of such faults have been presented in many parts of the literature. Partial discharge activity, thermal degradation, thermal cycling, harmonics and transients are some examples of such failure mechanisms. Whilst there has been an insight into the failure mechanisms, there is still no definite answer to how these defects manifest in the first place. Most of the failures that have been identified within literature are on end windings, especially slot ends. Some failure mechanisms have also been linked with thermal cycling. Frequent and rigorous stop/start cycles stress coils by inducing mechanical forces between elements of the coil and housing owing to differential thermal expansion. This differential expansion is dependent on the rate of rise of temperature and also the different coefficients of thermal expansion of the materials. The present paper will evaluate the thermal degradation of insulation systems used on marine generators using Finite Element Analysis (FEA) methods. On board temperature measurements of stator coils during a high speed run are used as one of the parameters within the FEA simulations, to investigate if there is any risk of differential thermal expansions during such an operational cycle. Different ramp rates are also analyzed within the FEA simulations to understand the effect of uneven thermal expansions and the risk of material degradation of the insulation in coils on marine systems. A brief review of the standards available for thermal cycling and testing are also presented within the paper.

Design-oriented modeling approaches, such as finite element analyses (FEA), rely on accurate material data for the modeled hardware. In the case of cookware used in domestic induction heating (IH) systems, manufacturers rarely provide the necessary data. Therefore, this contribution presents results for the electromagnetic material properties of ferromagnetic stainless steel, typically used in cookware for domestic IH. The magnetic material properties are modeled using Jiles-Atherton hysteresis model. With the used measurement method, less effort in preparation of suited material specimen is needed compared to conventional measurement methods. The presented results for the magnetic material properties are validated using Epstein frame measurements. It is shown that the hysteresis curves are similar to each other for both measurement methods. Regarding the specific electrical resistance, the results are validated using a microhmmeter. The values determined for the specific resistance show good accordance for the different measurement methods.

Doped material-based nanofluids, as an extension of single-phase nanofluids, expand the performance of heat transfer fluids. In this study, a new type of diathermic oil (DO)-based alumina-doped zinc oxide (AZO) nanofluids was prepared, and the thermophysical characteristics of nanofluids were analyzed. It could be found that the addition of new doped nanoparticles made up for the deficiency in the performance of DO as heat transfer fluid (HTF). Compared with the pure DO, the thermal conductivity of the AZO nanofluids (0.08 mass%) was increased by 8.125%. And the viscosity of nanofluids was decreased by 70% as the temperature increased. So as to further determine the application of nanofluids in the domestic heating system, the parameters of forced convection heat transfer in the tube were analyzed in this article. The convective heat transfer coefficient of AZO nanofluids increased with the increase in temperature. At 50 ℃, the convective heat transfer coefficient of 0.08 mass% AZO nanofluid reached the maximum of 5.49% compared with pure DO. More importantly, this research investigated the heat transfer benefits of using nanofluids in domestic solar heating systems. These promising results indicated that AZO nanofluids showed excellent properties at higher temperatures. It shows DO-based AZO nanofluids application potential in domestic solar heating systems.

The cutting forces will generally suffer massive complex factors, such as material deformation, tool eccentricity and system vibration, which will inevitably induce many great difficulties in accurately modeling the cutting force predictions that are very significant to investigate cutting processes. Therefore, the genetic algorithm optimized back-propagation and particle swarm optimization neural networks will be adopted to effectively construct cutting force prediction models. In these two back-propagation prediction models, the main milling parameters will be defined into their input vectors, and the transient milling forces along three different directions will be selected as their output vectors, then the implicit relationships between input and output vectors can be directly generated through practically training and learning these two built back-propagation models with a set of experimental milling force data. Meanwhile, the finite element analysis method will be also used to predict milling forces through programming two easy-to-operate plug-ins that can efficiently construct finite element analysis models, conveniently define processing parameters, and automatically perform mesh generation. Subsequently, the milling forces predicted by the established genetic algorithm optimized back-propagation and particle swarm optimization back-propagation models will be analytically compared with finite element analysis simulations and experiments; also the stress distribution and chip formations of finite element analysis and experiments will be comparatively investigated. Finally, the obtained results clearly indicate that these two back-propagation models built by artificial neural networks can well agree with finite element analysis simulations and experiments, but the particle swarm optimization back-propagation model is superior to the genetic algorithm optimized back-propagation model, which clearly demonstrate the particle swarm optimization back-propagation model has higher efficiencies and accuracies in predicting the average and transient cutting forces for different milling processes on aluminum alloy 7050.

This article presents the investigations on the constant frequency asymmetric voltage cancellation control in the AC–AC resonant converter-fed domestic induction heating system. Conventional fixed frequency control techniques used in the high frequency converters lead to non-zero voltage switching operation and reduced output power. The proposed control technique produces higher output power than the conventional fixed-frequency control strategies. In this control technique, zero-voltage-switching operation is maintained during different duty cycle operation for reduction in the switching losses. Complete analysis of the induction heating power supply system with asymmetric voltage cancellation control is discussed in this article. Simulation and experimental study on constant frequency asymmetric voltage cancellation (CFAVC)-controlled full bridge series resonant inverter is performed. Time domain simulation results for the open and closed loop of the system are obtained using MATLAB simulation tool. The simulation results prove the control of voltage and power in a wide range. PID controller-based closed loop control system achieves the voltage regulation of the proposed system for the step change in load. Hardware implementation of the system under CFAVC control is done using the embedded controller. The simulation and experimental results validate the performance of the CFAVC control technique for series resonant-based induction cooking system.

A finite element (FE) analysis with three-dimensional solid elements has been performed for estimating the structural behaviors of single shear bolted connections fabricated with cold-formed austenitic stainless steel by utilizing the existing test data for calibration. Failure and curling (out-of-plane deformation perpendicular to the direction of loading) criteria were proposed. Therefore, the failure mode and ultimate strength, predicted by FE analysis method, showed good agreements with those of experimental results. In this study, FE analyses for 10 test specimens fabricated with cold-formed carbon steel as well as stainless steel including failure mode of bolt shear fracture are carried out and the validity of numerical prediction for ultimate behaviors in cold-formed carbon steel bolted connections is also verified, based on the applicability of FE method for predicting the mechanical behaviors of bolted connections in cold-formed stainless steel. It is known from the coupon test results of steel materials that austenitic stainless (SUS304) steel has a higher tensile strength of material due to the effect of strength enhancements (considerable strain hardening) by means of cold-working process and much lower yield stress when compared to carbon steel. The influence of curling on the strength reduction of bolted connections is estimated quantitatively. In addition, characteristics of mechanical behaviors and the influence of curling in bolted connections between two different steel materials are compared through detailed investigation of FE analysis results.

This paper investigates the thermal impacts of electromagnetic proximity effects among the coils of domestic induction heating system (DIHS) with distributed planar spiral multicoils. A combined coordinates system is developed in the computation, consisting of a master Cartesian coordinate system and multiple slave cylindrical coordinate systems. The proposed computing method is implemented with different effecting parameters so as to analyze the impacts of proximity effects and eddy currents distribution in the DIHS. Computation results are validated through comparing against those from the finite element method (FEM). Furthermore, the temperature field is calculated to study the thermal impacts of proximity effects on the thermal distribution in the induction plate.

The evaluation of torque transmission capacity for centrifugal compressor impellers can be complicated due to the unique geometric characteristics of the impeller wheels. The existing analytical method for keyless interference fit only works for simple geometries like cylinders. In general, finite element analysis (FEA) simulations are needed to obtain the torque capacity of centrifugal compressor impellers for a specific setup (rotational speed/geometric scale/interference fit rate). However, when the torque capacity needs to be evaluated in multiple working conditions, the time cost of FEA simulations can be an issue if each case is evaluated individually. In this study, a methodology is provided to obtain the torque capacity of centrifugal compressor impellers instantly for any given working conditions with pre-generated data from FEA simulations, especially with scaling of the interference fit rate. If the interference fit rate (ratio of interference fit to diameter) is kept the same as the pre-generated FEA data, the results can be directly scaled by rotational speed and geometric scale factor which is covered by the existing method and not the focus of this study. If the given interference fit rate is different than the setup in pre-generated FEA simulations, then an engineering approximation is used to calculate the contact pressure and torque capacity based on impeller bore deformation. In this methodology, the FEA simulations are performed before knowing the working conditions which can be very useful in many time-sensitive industrial applications.