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The paper presents the results of modeling and testing of a heavy weight part made of Cr-Mo, which was V-modified ultrahigh strength steel grade AISI 4140, processed through a novel open-die forging program and two alternative routes of twostage heat treatment cycles designed to meet requirements of high-duty components for energy sector. By using unconventional forging conditions based on the assumption of large feed and reduction ratio and modifying the chemical composition, better control of the austenite grain was achieved to minimize abnormal grain growth and/or strain uniformity problems. Using the Finite Element Modeling, the multi-stage sequence of upsetting and the cogging strain distribution were optimized to minimize the strain variation along the length to a range 2.2÷2.7, and correlated with the microstructure generated at each main stage on the large cross-sections of the shaft. Mechanical and thermal processing cycles designed using the finite element method were fully verified physical modeling using a 16 ton forging block, including two alternative quenching strategies: oil vs. water spray and air. The material was studied in the as-forged, normalized and heat-treated states to observe the behavior of the hot-formed material and the effects of cooling conditions on the microstructure during the final heat treatment. It was found that the use of large feed ratios on cogging and varied cooling allowed to suppress the adverse effects of the inevitable abnormal grain growth, resulting in 1-2 ASTM in forged condition and reaching 6 ASTM and 8/9 ASTM after quenching in oil and water spray, respectively, which allowed a corresponding notched impact strength of 44÷48 and 85÷122 J/cm2 in the critical region of the forged shaft after tempering. [ABSTRACT FROM AUTHOR]

In this paper, a hybrid approach is proposed for Multiphase Halbach Array Permanent Magnet Generator (MHAPMG) in the direct driven wind turbine. The proposed approach is the consolidation of Archimedes optimization algorithm (AOA) and Radial Basis Function Neural Network (RBFNN) named AOA-RBFNN approach. The proposed approach achieves higher efficiency at low speed and it is utilized to improve the lesser Cogging torque with torque ripple and fault tolerance. The proposed generator is compared with Multiphase Surface Mount conventional Permanent Magnet Generator (MSMPMG) for its improved outputs. The proposed generator is used to chose the turbine design and to estimate the output of 1000 W with a speed of 440 RPM and the wind speed of 9 m/s. The proposed approach optimizes the electromagnetic performance of Cogging and back electromotive force. The performance of the proposed Halbach array is analyzed with the regular sequence with multiphase topology based on the induced electromotive force, Cogging Torque, Air gap Flux density, and Harmonic Components. The proposed generator is investigated by finite element analysis (FEA). By then, the performance of the proposed system is activated on MATLAB/Simulink platform. The efficiency of WT using proposed technique, HS, TS, and PSO becomes 98%, 80%, 77%, and 82%, respectively. [ABSTRACT FROM AUTHOR]

To create a rational technology of cogging process and to determinate the optimal values of the angles of tilt and single reduction the stress-strain state (SSS) of the blank during cogging in the flat dies was analyzed. By using the finite element method and program MSC.SuperForge quantitative data are obtained and the basic patterns of distribution of SSS, the temperature during the simulation of tilting in flat dies with different angles of tilting and the amount of reduction were established. Sustainable experimental-industrial technology of forging of two-phase titanium alloys was developed and tested. [ABSTRACT FROM AUTHOR]

SUMMARY This paper presents a method for reducing cogging thrust in permanent-magnet-type linear synchronous motors. A phase shift method and supplement tooth method are proposed. The methods do not affect the original thrust performance of the linear motor, nor do they greatly modify its basic shape. The methods are confirmed through experiments and FEM analysis. This paper also discusses the effect of construction errors on cogging thrust. [ABSTRACT FROM AUTHOR]

This paper presents the optimal design of a surface mounted permanent-magnet (PM) Brushless direct-current (BLDC) motor meant for spacecraft applications. The spacecraft applications requires the choice of a motor with high torque density, minimum cogging torque, better positional stability and high torque to inertia ratio. Performance of two types of machine configurations designed viz Slotted PMBLDC and Slotless PMBLDC with Halbach array and radial magnetization are compared with the help of analytical and finite-element (FE) methods. It is found that unlike a Slotted PMBLDC motor, the Slotless type with Halbach array develops zero cogging torque without reduction in the developed torque, suiting spacecraft applications. Moreover, the machine being coreless provides high torque to inertia ratio and zero magnetic stiction confirming to the requirements of spacecraft applications. [ABSTRACT FROM AUTHOR]

Abstract: Microstructural changes during the cogging of an Alloy 718 ignot processed by (vacuum induction melting)/(vacuum arc re-melting) were predicted using the combined approach of three-dimensional finite element simulation and modeling for the recrystallization and grain growth. In order to establish recrystallization and grain growth models for Alloy 718 ingot, hot compression and isothermal heat treatment tests were carried out at different temperatures and strain rates. The constitutive equations for metadynamic and static-recrystallization behavior were generated using the experimental data collected from various references. From the experimental results, it was found that the dissolution temperature of δ-phase (Ni3Nb) played an important role in the microstructural refinement of Alloy 718 ingot. The predicted grain size and its distribution were compared with the microstructures of the cogged billet, and the reliability of the prediction was discussed. [Copyright &y& Elsevier]

For the calculation of torque in synchronous motors a local method is analysed, based on the Maxwell stress theory and the filtered contributions due to the harmonics of the magnetic vector potential in the motor air-gap. By considering the space fundamental field only, the method can efficiently estimate the average synchronous torque for a variety or motor topologies, including concentrated winding designs. This approach employs an analytical filter for the Maxwell stress tensor and `frozen permeability' technique. The proposed method is validated by comparison with FE results for several synchronous motor types: interior permanent magnet motors, wound field motor, synchronous reluctance motor. [ABSTRACT FROM AUTHOR]

Three-phase permanent magnet brushless dc motors are widely used. As a function of the rotor position, the torque produced by these machines has a pulsating component in addition to the de component. This pulsating torque has a fundamental frequency corresponding to six pulses per electrical revolution of the motor. The shape of the torque waveform and, thus, the frequency content of the waveform can be influenced by several factors in the motor design, and construction. This paper addresses the various factors that influence the torque waveshape. It is shown that in addition to the basic induced electromotive force (EMF) waveshape, the magnetic saturation in the stator core, and the accuracy in the skewing are also key factors in determining the torque waveshape. Computer simulation using finite element technique has been conducted to study the torque waveform. Simulation results successfully duplicated the torque waveforms measured in experiments under different excitation currents. [ABSTRACT FROM AUTHOR]