On the relationship of reversible and irreversible processes during magnetization and magnetization reversal of ferromagnetic materials

Curves corresponding to the normal magnetization curve and the back of the hysteresis loop and separately reproducing reversible and irreversible processes of magnetization and reversibly irreversible changes in the magnetization during maximum minor hysteresis cycles were constructed. For specimens of steel 75Γ hardened and tempered to 300°C, generalized expressions for curves that reproduce relationships between different components for the demagnetization portion of the hysteresis loop were obtained; for specimens hardened and tempered to 600°C, individual expressions for portions of the magnetization-reversal curve of the steel in fields from 0 to ?2H _c were obtained. The dependences of the relative irreversible and reversible fractions of saturation magnetization on the tempering temperature were analyzed. The maximum reversible component of the saturation magnetization, i.e., the difference M _s-M _r, was shown to be a suitable parameter for quality control of tempering.     

超磁致伸缩电—机转换器位移感知模型及滞环分析

超磁致伸缩电—机转换器响应快、可靠性高,但动态驱动时,因受磁滞、涡流等因素影响,输出位移的滞环较大。需要以准确的数学模型为基础,通过控制算法来补偿滞环,或通过优化其结构参数来降低滞环。通过实时测量超磁致伸缩棒上所绕线圈两端的感应电压和推导此感应电压与超磁致伸缩电—机转换器输出位移的关系,建立实时反映超磁致伸缩棒磁化状态的超磁致伸缩电—机转换器动态位移感知模型,并进一步推导出了超磁致伸缩电—机转换器输出位移的滞环与其结构参数的关系。通过与试验结果对比,当驱动频率小于300 Hz时,由所建模型计算出的位移峰—峰值的相对误差小于5.8%;通过仿真研究超磁致伸缩电—机转换器结构参数对输出位移滞环的影响,得出增加预压弹簧的刚度,可以降低动态驱动时的滞环。     

Effect of Deviation from Coaxiality between the Directions of Magnetization and Mechanical Strain on the Results of Magnetic Testing of Elastic Strain in Steels

The magnetoelastic effect in steels that are in the states of coercive force and residual magnetization in the saturation hysteresis loop is studied. The regularities of changes in the residual magnetization and coercive force under uniaxial tensioning and compression of specimens of 30KhGSA steel magnetized along the direction of strain application are established. It is shown that a variation in the direction of magnetization and complication of the strain pattern result in considerable deviations in the character of changes in the magnetic forces determined by a ferroprobe-type coercive force meter for elastically strained plates from St3 and R6M5 steels and for an St3 beam.     

M—H回线可变时间常数的测量方法

针对光调制直接重写磁光薄膜磁滞回线的测量,提出一种简单的自动变积分时间常数的测量方法,既能有效地抑制噪声,确保幅度和相位的不失真,又能保证M－H矩形度的不失真,以及矫顽力Hc的一定精度。并给出一个比较例子,结果表明该方法更合理。     

基于Preisach模型的永磁同步轮毂电机损耗及温度场建模与分析

针对永磁同步轮毂电机运行过程中发热明显,严重影响永磁体性能和电机寿命的问题。开展电机铁心材料磁滞特性试验,测试一维磁化条件下的磁滞回线,考虑不同磁场强度和磁场高频特性对磁滞特性的影响。考虑到经典Preisach理论无法解释磁场频率过高的现象,基于对称小回环（Symmetric minor loops, SML）的密度函数离散化方法建立高频磁场强度变化的磁滞特性模型,通过与试验结果的对比发现该方法预测结果准确,对于在不同频率下的磁化特性有很好的模拟效果。根据铁心损耗的影响因素分析,提出考虑旋转磁化影响、磁密谐波影响的铁心损耗旋-交系数计算铁心损耗。最后建立电机三维温度场模型,仿真计算不同工况下各个部件的温升情况及危险点,并在试验台上进行电机温升试验,与仿真结果进行对比验证。仿真结果电机温度最大值为73.2℃,试验最高温度为72.6℃,证明电机损耗计算以及温度场仿真的准确性。研究结果表明,考虑磁场强度和磁场频率对铁心磁化特性的影响,能有效改善电机电磁计算中的缺陷,提高电机电磁场、损耗及温度预测的准确性。     

磁滞回线测量方法与Simulink仿真分析研究

针对变压器磁滞回线间接测量存在的电路参数复杂和测量结果准确性难以评价等问题,通过对RC积分器测量方法的电路时域微分方程求解和Simulink仿真结果的分析,提出了一种确定电路参数的方法。借助Simulink饱和变压器的模型,仿真测量了在不同电压下饱和变压器磁滞回线图像,进一步画出了基本磁化曲线;通过对比基本磁化曲线测量值与Simulink中模型值的差异,结果显示利用该方法能仿真得到饱和变压器的磁滞回线,其测量误差可用电路参数估算和控制。根据该方法设计了测量电路,得到了实际变压器的磁滞回线,验证了该方法的正确性。研究结果表明,该方法揭示了RC积分法测量的电路参数,并能预测测量误差,具有准确性高的特点,为非线性饱和变压器磁滞回线测量电路参数设计提供了参考依据。     

Studying Field Dependence of Reversible Magnetic Permeability in Plastically Deformed Low-Carbon Steels

The field dependences of the signal U^~ (Н) across the measuring winding of an induction transducer, which are proportional to reversible magnetic permeability, have been measured in lowcarbon St3 steel plastically deformed by stretching under reversal of its magnetization along the major hysteresis loop both when unloaded and under an elastic tensile load. A method is proposed for isolating the contribution rendered to the measured signal by the irreversible displacement of only 90-degree domain walls. The method consists in subtracting the curve U^~ (Н) measured under the elastic tensile load of a magnitude sufficient to compensate for internal compressive residual stresses in the sample from the no-load U^~ (Н) curve. It has been established that the induced magnetic anisotropy field obtained with this method is virtually no different from that produced by the method in which no-load U^~ (Н) curves are approximated.

     

Influence of uniaxial tension on magnetic characteristics of the 12ΓБ pipe steel exposed to hydrogen sulfide

The results of measurements of the magnetic characteristics of specimens of the 12ΓБ pipe steel subjected to treatment with hydrogen sulfide for 96–384 h and also in the initial state, which were performed directly under the conditions of applied uniaxial tensile stresses to the point of specimen failure, are presented. The influence of hydrogen sulfide for 96 h has almost no effect on the mechanical and magnetic properties of the 12ΓБ steel, whereas a longer exposure leads to an appreciable decrease in the metal plasticity and an increase in its strength characteristics and the coercive force. The dependences of the magnetic characteristics on the degree of deformation are qualitatively similar to the stress-strain diagram except for the initial region of loading, where the effect of induced magnetoelastic anisotropy is displayed. At the stage of elastic strains, an unambiguous correlation between the coercive force measured on a minor hysteresis loop in weak fields and tensile stresses was discovered, thereby allowing the use of this parameter for evaluating the elastic stresses in articles from the 12ΓБ pipe steel, including in conditions of the influence of a hydrogen sulfide medium on this steel.     

基于材料磁特性的结构疲劳损伤磁测方法研究

结构疲劳损伤测量和评估方法的研究是一个难点。由于疲劳损伤伴随材料磁特性的变化,且磁测法测量简单方便,所以利用材料磁特性测量和评估结构的疲劳损伤具有实际意义。以Q235钢为试件,通过构建疲劳损伤磁测试验平台,研究了循环应力下,基于磁滞回线的结构疲劳损伤磁测法。结果表明,疲劳损伤不同,磁滞回线也不同。提取磁滞回线的矫顽力H_c和剩磁B_r作为特征量进行分析,结果显示,试件失效前的疲劳过程大致分为两个阶段:首先是H_c和B_r的快速增大阶段,该阶段的H_c和B_r对疲劳损伤的灵敏度较高;然后是H_c和B_r的变化缓慢阶段,该阶段的H_c和B_r对疲劳损伤的灵敏度较低。最后分析了H_c和B_r与疲劳累积损伤D的变化关系,能够为结构疲劳损伤的定量评估及在线监测技术的研究提供基础。     

Inspection of the Strength Characteristics and Heat-Treatment Quality of Ferromagnetic Articles Based on Parameters of the Residual-Magnetization Hysteresis Loop upon Their Local Magnetization and Magnetization Reversal in a Pulsed Magnetic Field with a Variable Amplitude: I. Parameters of the Hysteresis Loop

Results of an experimental study of the anomalous behavior of the residual-magnetization hysteresis of ferromagnetic articles that, under local magnetization and magnetization reversal in a pulsed magnetic field with a variable amplitude, were subjected to heat treatment under different conditions are reported. Parameters of the hysteresis and their dependence on the magnetization and magnetization-reversal conditions, as well as on the magnetic properties of a material, are considered.__________Translated from Defektoskopiya, Vol. 41, No. 5, 2005, pp. 3–13.Original Russian Text Copyright © 2005 by Matyuk, Mel’gui, Pinchukov, Lyubarets.All papers in this issue are devoted to the 100th anniversary of the birth of the late M.N. Mikheev, corresponding member of the Russian Academy of Sciences and one of the founders of magnetic structural analysis.     

Coercive-force hysteresis of carbon steels during elastic cyclic tensile deformation

Dependences of the coercive force and mechanical stresses on cyclic tensile in the region of elastic deformation of steel samples with various carbon contents (Armco iron, 3, 8) are investigated. It is shown that the dependence of the coercive force on cyclic elastic tensile deformation is reversible for well-annealed samples. The dependence for plastically deformed steels has a hysteresis loop that is significantly determined by the carbon content and increases with an increasing degree of plastic deformation. It is assumed that the hysteresis of the coercive force as a function of elastic cyclic tensile deformations in plastically deformed carbon steels is caused generally by the appearance “free” carbon atoms, i.e., those not bound in carbide phases, which act as interstitial impurity atoms in the lattice of α-iron.     

Hall-effect hysteresigraph for amorphous bubble-domain materials

A hysteresigraph is described which provides a much more rapid measurement of the coercivity of amorphous bubble films than any previously used method. This device utilizes the Hall effect to sense the film magnetization and has sufficient sensitivity and stability that coercivities as low as approximately 1 Oe can be readily measured. Although this device cannot provide an absolute measurement of saturation magnetization, approximate values of this quantity can be inferred from the saturation field indicated by the hysteresis loop. A probe-contact arrangement is employed which permits measurements to be made even on films having an insulating passivation layer.     

Magnetization and magnetoresistance of common alloy wires used in cryogenic instrumentation

We present magnetization and magnetoresistance data at liquid-helium and liquid-nitrogen temperatures for wire materials commonly used for instrumentation wiring of specimens, sensors, and heaters in cryogenic probes. The magnetic susceptibilities in Systeme International units at 4.2 K were found to be: Manganin 1.25x10(-2), Nichrome 5.6x10(-3), and phosphor bronze -3.3x10(-5), indicating that phosphor bronze is the most suitable for high-field applications. We also show the ferromagnetic hysteresis loop of Constantan wire at liquid-helium temperature. The magnetoresistance of these four wires was relatively small: the changes in resistance at 4 K due to a 10 T transverse magnetic field are -2.56% for Constantan, -2.83% for Manganin, +0.69% for Nichrome, and +4.5% for phosphor bronze, compared to about +188% for a typical copper wire under the same conditions.     

基于PI迟滞模型的单压电变形镜开环控制

压电非线性迟滞导致压电变形镜的开环控制精度及闭环工作带宽降低,限制了其在自适应光学系统中的应用。为克服迟滞影响,提出采用PI迟滞模型描述单压电变形镜的迟滞非线性特性,实现单压电变形镜的高精度开环控制。首先建立PI迟滞数学模型,利用最小二乘法辨识PI迟滞模型的权值,计算出PI逆模型的权值和阈值,从而获得消除迟滞后的变形镜控制电压;接着搭建了基于哈特曼波前传感器的自适应光学测试平台,采用单压电变形镜的环形致动器进行离焦面形的开环控制实验。实验结果表明,经过迟滞消除后变形镜的电压-变形迟滞由9.3%降低到1.2%,离焦面形的开环重构精度提高70%以上,证明该迟滞模型可有效应用于单压电变形镜的开环控制。     

Effect of Magnetic Parameters and Dimensions of Uniformly Magnetized Bodies on Inductive Coercive Force

From the Fröhlich approximation of changes in the magnetization of a ferromagnetic material on the descending branch of the hysteresis loop, an analytical expression for the inductive coercive force H _B of a homogeneously magnetized body has been derived. Effects of magnetic parameters of the material and demagnetizing factor on H _B have been studied.     

Magnetization Distribution over Long Ferromagnetic Steel Pipes in a Weak External Magnetic Field under Elastic and Plastic Bending

The magnetization distributions over ferromagnetic pipes under both elastic and plastic exural stresses are studied. For this purposes the corresponding distributions of these stresses and the residual stresses developing in plastically deformed pipe zones after unloading are calculated. Experimental and theoretical data on the magnetoelastic increments of magnetization induced under tensile and compressive stress are used to find the magnetization distributions.     

Recording of single-particle hysteresis loops with differential phase contrast microscopy

The magnetic behaviour of laterally patterned structures on a micrometer or nanometer scale in external magnetic fields can be described by their hysteresis loops. However, it is very difficult to record the hysteresis loop of a single (sub-) micron-sized particle. Furthermore, extensive calculations are necessary in order to interpret the shape of the loop and to conclude the micromagnetic domain configuration in the sample from the hysteresis loop only. We have developed a technique which yields both the hysteresis loop and the magnetic domain structure simultaneously. This method uses differential phase contrast microscopy and a microscope with remote control capability for the automatic recording of a single-particle hysteresis loop.     

Analysis of the strengthening mechanism based on stress-strain hysteresis loop in short fiber reinforced metal matrix composites

The strengthening mechanism of short fiber or whisker reinforced metal matrix composites has been studied by a continuum mechanics treatment utilizing finite element analysis (FEA). To assess the tensile and compressive constitutive responses, a constraint-unconstraint comparative study based on stress-strain hysteresis loop has been performed. For analysis procedures, the aligned axisymmetric single fiber model and the stress grouping technique have been implemented to evaluate the domain-based field quantities. Results indicate that the development of significant triaxial stresses within the matrix both for the tensile and compressive loading, due to the constraint imposed by reinforcements, provide an significant contribution to strengthening. It was also found that fiber stresses are not only sensitive to the fiber/fiber interaction effects but also substantially contribute to the composite strengthening both for the tensile and compressive loading.     

磁化状态对力磁耦合关系的影响分析

从宏观和微观两方面分析了磁化状态对力磁耦合关系的影响。从微观角度,在不同的磁化状态下,分析了铁磁构件磁畴结构在外加应力作用下的变化规律;从宏观角度,基于接近原理解释了外加应力是使初始磁化状态不断向无滞后磁化状态靠近的过程,而靠近的方向由无滞后磁化强度与初始磁化强度的差值决定,如果差值大于零,则磁化强度随应力的增大而增大,如果差值小于零,则反之,但无滞后磁化强度又随应力的变化时刻发生变化。为了验证理论分析结果,对三种不同初始磁化状态下的Q235钢进行静载拉伸试验,试验结果与理论分析具有一致性。     

O型钢丝绳隔振器的三向动态特性

采用周期动态加载试验方法,分别获得了O型钢丝绳隔振器在剪切、横滚和拉压方向上随激励振幅和频率变化的动态迟滞特性。在剪切和横滚方向,试验迟滞环呈现对称特性;在拉压方向上,试验迟滞环呈现非对称迟滞特性,并随着激励幅值的增加,迟滞环面积增大而且非对称迟滞特性表现的更加明显;在拉伸方向上拥有硬化刚度;压缩方向上刚度明显软化。在测试频率段,隔振器3个承载方向的滞回性能与频率无关。针对隔振器的三向动态特性,提出一种改进的归一化Bouc-Wen模型和一种简单有效的参数识别方法,并基于试验数据验证该模型和参数识别方法的有效性。结果表明,试验曲线和理论模型预测曲线吻合较好,该模型和方法能够分别有效描述隔振器的三向动态特性。