Effect of organic solvent on the cold sintering processing of SrFe12O19 platelet-based permanent magnets

In this work we have investigated the effect of the solvent during the processing of SrFe₁₂O₁₉ platelet-based permanent magnets by cold sintering process (CSP) plus a post-thermal treatment. Several organic solvents: glacial acetic acid, oleic acid and oleylamine have been analyzed, optimizing the CSP temperatures at 190?270 °C, under pressures of 375?670 MPa and 6?50 wt% of solvent. Modifications in the morphological and structural properties are identified depending on the solvent, which impacts on the magnetic response. Independently of the solvent, the mechanical integrity of ferrite magnets obtained by CSP is improved by a post-annealing at 1100 °C for 2 h, resulting in relative densities around 92 % with an average grain size of 1 μm and a fraction of SrFe₁₂O₁₉ phase >91 %. H_C ≥ 2.1 kOe and M_S of 73 emu/g are obtained in the final sintered ceramic magnets, exhibiting the highest H_C value of 2.8 kOe for the magnet sintered using glacial acetic acid.     

Refinement of primary carbides in AISI DC 53 cold work tool steel by thin section copper permanent mould casting and water atomization

In this study, as alternative methods to conventional production methods involving thin section copper permanent mould casting (fast solidification) and water atomization (rapid solidification) of AISI DC 53 cold work tool steel have been investigated. Thin slabs obtained by copper mould casting was homogenized at 1150 °C for one hour and then hot rolling was be applied. After hot rolling, conventional heat treatment have been applied to thin slabs. The same heat treatment procedure have been performed for a commercially available AISI DC 53 which is manufactured by thick section ingot casting and rolling. In order to investigate also the effect of rapid solidification on AISI DC 53 tool steel, steel powder was produced by water atomization technique. Experiments have revealed that thin steel slabs in permanent copper mould and rapidly solidified tool steel powder by water atomization have a more refined primary M₇C₃ carbides than commercially available steel.     

电永磁吸盘在石油套管接箍切断机下料工序中的应用

针对石油套管生产过程中接箍切断岗位人员搬运接箍劳动强度大、存在安全隐患的问题，对生产工艺过程、电磁吸盘的原理和性能进行分析，采用电永磁吸盘设计了一种接箍自动下料装置。该装置可以根据设定进行电磁吸盘的充/退磁，实现整层接箍的抓取和卸料，整个过程实现一键自动下料，全程不需人工干预。现场生产应用表明，使用电永磁吸盘进行整层接箍下料，能大幅降低岗位员工的劳动强度，生产效率提高5%以上，减少了安全隐患，达到了预期目的。     

基于线性自抗扰控制技术的永磁同步电机控制策略研究

永磁同步电机(PMSM)具有体积小、高速度、高精度等优势,广泛应用于现代工程实际当中。在多数情况下其控制策略采用经典的PID控制,但较多的实际复杂环境当中,传统的PID所暴露的固有缺陷已经无法满足PMSM的控制高效性。采用先进的线性自抗扰控制策略,其具有不依赖具体对象模型,控制器自身可以估计补偿作用于被控对象的所有扰动的优势,实验仿真结果表明,该方案有效抑制了扰动,进而提高了系统的控制性能。     

Calculation of the Characteristics of Salient‐Pole Synchronous Machines Assisted by Permanent Magnets on the Basis of the Operating Principle

In this study we investigate a method for accurately calculating the characteristics of salient‐pole synchronous machines assisted by permanent magnets. First, the operating principle of the machines is investigated by using both finite element analysis and a simple magnetic circuit. Then, a theoretical representation of the assist effect on the permanent magnets is derived based on the magnetic circuit. Finally, the measured and calculated results are compared in order to confirm the validity of the proposed calculation method. We show that the load characteristics of the proposed machine can be accurately estimated from the no‐load and short‐circuit characteristics of the conventional machine without permanent magnets, and the size and magnetization of the inserted permanent magnets.     

A Restart Control Method for Position Sensorless PMSM Drive Systems Without Potential Transformer for Railway Vehicle Traction

This paper proposes a restart control method for position sensorless PMSM drive systems without a potential transformer for railway vehicle traction. This method can estimate the initial rotor speed and position under coasting conditions over the entire speed range. The method can also be used when the back‐EMF voltage is higher than the inverter DC link voltage. The proposed method is verified by experiments using a 200‐kW PMSM.     

A time integration algorithm for a 3D constitutive model for SMAs including permanent inelasticity and degradation effects

Components based on shape‐memory alloys are often subjected to several loading cycles that result in substantial alteration of material behavior. In such a framework, accurate models, as well as robust and efficient numerical approaches, become essential to allow for the simulation of complex devices. The present paper focuses on the numerical simulation of quasi‐static problems involving shape‐memory alloy structures or components subjected to multiple loading‐unloading cycles. A novel state‐update procedure for a three‐dimensional phenomenological model able to describe the saturation of permanent inelasticity, including degradation effects, is proposed here. The algorithm, being of the predictor‐corrector type and relying on an incremental energy minimization approach, is based on elastic checks, closed‐form solutions of polynomial equations, and nonlinear scalar equations solved through a combination of Newton‐Raphson and bisection methods. This allows for an easy implementation of model equations and to avoid the use of regularization parameters for the treatment of nonsmooth functions. Numerical results assess the good performances of the proposed approach in predicting both pseudoelastic and shape‐memory material behavior under cyclic loading as well as algorithm robustness.     

一种新颖的SPMSM驱动系统自适应死区补偿方法

逆变器死区效应将造成电机电流畸变,为提高表贴式永磁同步电机电流控制精度,提出一种自适应死区电压补偿策略。该方法利用参考电流建立d、q轴死区电压核函数,能够在表贴式永磁同步电机电阻、电感参数未知的情况下,对d、q轴死区电压的幅值进行辨识,将辨识的电压幅值与其核函数相乘得到所需补偿的死区电压。从而解决了输死区电压造成的相电流畸变难题。仿真结果表明,所提出的电流控制策略能够有效减少相电流谐波含量、提高电流控制精度。     

基于金属Gd的室温旋转式磁致冷演示样机的设计

磁致冷是利用磁介质在其居里温度Tc附近具有较大磁热效应的特性实现的一种物理现象.以稀土金属Gd为磁致冷材料,对室温旋转式磁致冷演示样机进行了结构设计,演示样机可达4.4K的制冷温跨,用于设计性实验教学,具有良好的示范作用.