考虑磁导率非线性的铁磁材料脉冲涡流检测仿真研究

长期以来,脉冲涡流检测中铁磁材料的磁导率多被视为常数,但这种简化的合理性及其影响尚缺乏充分的证明.本文基于有限元法,建立了探头置于Q235钢板上方的脉冲涡流检测模型,研究了钢板磁导率的空间分布和时间变化规律及其对探头信号的影响,并进行了实验验证.结果表明:钢板中瞬态磁场的工作点与激励电流幅值有关,增大激励电流,磁场可能超出磁化曲线的起始磁化区而进入到瑞利区甚至陡峭区;由于磁导率非线性的影响,激励方波高、低电平段的感应电压信号不成奇谐对称,高电平段的晚期感应电压比低电平段的大;钢板浅层磁导率的变化显著,不能简化为常数,而深层的磁导率变化很小,可视为常数.     

基于磁弹效应的单旁路激励钢缆索索力传感器

针对环式穿套结构磁弹效应索力传感器在使用中存在的实际问题,提出了一种单旁路结构的磁弹性索力传感器.从传感器的磁路结构、激励方式、外部磁化强度等几方面进行了深入的讨论,设计出了基于磁弹效应的单旁路激励钢缆索索力传感器原理样机,搭建了相应的实验系统,并对传感器样机进行了初步的拉力实验.实验结果表明,所提出的单旁路激励索力传感器原理可行,测量重复性误差小于0.2%.     

一种多提离值的金属磁记忆检测方法

金属磁记忆检测技术是一种新型的无损检测技术,它利用金属的磁记忆效应来确定构件的缺陷区域.检测中由于一些构件表面感应磁场信号不平滑,存在与缺陷信号相似的磁场特征和梯度表现,容易造成漏判或误判.为了区分这两种信号,通过建立磁偶极子模型,分析了缺陷在材料表面或近表面的情况下检测提离值对磁信号的影响,发现在提离值改变时感应磁场和缺陷漏磁场存在不同的表现.根据这一现象,提出多提离值检测方法进行精确定位.通过对钢板进行实验验证了该方法的有效性.     

浅述线圈磁芯全桥结构的读磁器

一种线圈磁芯全桥结构的读磁器,与防伪检测设备的主处理器连接的,读磁器包括外壳、在外壳内设置有坡莫合金屏蔽壳和差分放大模块、沿坡莫合金屏蔽壳的长度方向设有工作窗口,且在工作窗口中依次设置多个独立的检测通道,每个检测通道由4个磁感应单元组成的惠斯通全桥结构;惠斯通全桥结构用于感应磁场的变化输出差分电压信号到差分放大模块中,差分放大模块具有抑制共模输入信号,放大差模输入信号的功能,并输出待检物的磁特征防伪信号给防伪检测设备的主处理器,从而大大地提高了国产传统的线圈+磁芯式读磁传感器抗电磁干扰性能及输出信号的信噪比,达到了防伪检测设备对读磁传感器抗电磁干扰及信噪比的性能要求。     

磁性液体倾角传感器的实验研究

利用磁性液体二阶浮力原理设计出一种新型的一维倾角传感器,给出了传感器的电路结构方框图.实验研究了磁性液体倾角传感器的输出电压与倾斜角度、倾斜角度的正弦、激励信号峰值电压以及激励信号频率的关系.分析了由于永磁铁周围磁场的不均匀对磁性液体传感器稳定性的影响.     

新型双向流量计磁导率和几何参数对流量输出电压信号的影响

新型双向流量计外部磁线圈输出电压信号波形不平滑、杂波扰动明显的问题与部件磁导率、几何参数等密切相关,为了改善外部磁线圈输出电压信号质量及优化设计参数,首先对流量传感器的结构进行理论分析,得到了外部磁线圈输出电压信号的解析式,然后建立了二维Ansoft Maxwell仿真模型,对导磁体小球、永磁体、磁线圈、测量管、中轴等部件的磁导率和几何参数对线圈输出感应信号的影响进行仿真.结果表明,永磁体体积越大、导磁体小球的半径和磁导率越大、中轴的半径和磁导率越大,外部磁线圈输出感生电压信号幅值越大;测量管壁厚度和磁导率越大、永磁体与导磁性小球距离越大,外部磁线圈输出感生电压信号幅值越小.增加测量管壁的厚度对抑制基波扰动信号幅值、平滑输出波形具有较明显的作用.     

IPMC的力输出特性

IPMC(ion-exchange polymer metal composite)离子交换聚合物-金属复合材料)是一种人工肌肉材料,其较低的驱动电压能产生较大的位移变形,研究了IPMC这种智能材料的输出力特性.实验选取了不同电压幅值,不同频率的方波、三角波、正弦波3种波形作为电激励信号,通过力传感器实测了IPMC试样末端的输出力.结果表明,随着电压幅值的增大,其输出力也增大;随着电刺激信号频率的降低,其输出力也增大;而波形对其输出力影响不显著.     

交变磁场测量法在表面裂纹无损检测中的应用

为了分析交变磁场测量法在无损检测中的应用及检测金属表面裂纹长度和深度的影响因素,本文根据交变磁场测量法基本原理,设计了新型的传感器探头和相关硬件电路,可以实现全方位检测金属表面缺陷,抑制噪声并提取缺陷信号的微小变化量。结果表明:探头型号和激励频率对漏磁场的检测影响很大,正交矩形激励线圈方法更方便直观;当霍尔传感器扫过表面裂纹时脉冲漏磁信号急剧降为零后又剧增到最大时,各个深度的表面裂纹信号到峰时间近似呈线性关系,这两个特点能用来对表面缺陷进行定位和定量。     

新型推挽激励的谐振式微机械静电场传感器

为了提高传感器的信噪比(signal-to-noise ratio,SNR),降低器件的耦合干扰,基于表面微机械工艺设计制作了一种新型推挽激励方案的谐振式微型静电场传感器.该传感器敏感结构主要包括静电梳齿激励电极、屏蔽电极和感应电极3部分.工作时,在该传感器敏感结构同一侧梳齿的固定端上加入反相相等的激励信号,实现差分激励,使屏蔽电极在谐振频率处振动,从而在感应电极上感应出差分电流信号,通过相关检测方式检测出传感器该输出信号的二次谐波分量,即可获得被测静电场强度大小.该传感器的新型结构设计和激励检测方案可获得最大电场响应灵敏度,并有效抑制了同频耦合串扰和共模噪声.常压室温(约25℃)测试结果表明,在量程(-15 kV/m～15 kV/m)内,只需要5 Vpp激励电压,其中线性度(端基线性度)达到了1.03%,分辨率优于200 V/m.     

环境磁场对磁记忆检测信号的影响研究

针对磁记忆检测中环境磁场对检测信号影响问题,首先详细分析试件放置方向变化时,不同类型损伤区域的磁场变化情况。然后根据磁记忆检测信号组成,研究环境磁场对磁记忆检测信号的影响机理。最后得出环境磁场对磁记忆检测信号的影响是环境磁场、被测试件自身磁化状态以及试件材料的磁特性共同作用的结果。当被测试件放置方向不同时,测得的磁场信号不是简单地在幅值上整体漂移,整体形貌上也可能会发生一定变化。在工程检测过程中,被测试件的放置方向应尽量保持不变。     

绳锯线弓角静态测量方法的研究

金刚石绳锯在切割圆弧板材时,受到进给方向的阻力,形成"线弓角",使板材中部产生"过切",严重时导致材料报废.为解决这一问题,提出了线弓角的概念,从理论上提出了一种基于悬臂式力传感器的绳锯线弓角的静态测量方法,通过轴力传感器输出的电压值计算出线弓角度.试验在自行设计和搭建的绳锯线弓角测量平台上进行,用钢丝绳模拟串珠绳产生线弓角,并进行导轮受力与线弓角关系的静态测量试验分析,以验证该方法测量线弓角的可行性.试验结果表明:在一定范围内,串珠绳初始张紧力越大,线弓角的计算值越接近理论值.因此,采用所提出的测量方法,当装有轴力传感器的导轮处在刚好与钢丝绳接触的状态下,选择合适的初始张紧力,可以测得较准确的角度值.     

霍尔效应的地下位移三维测量方法研究

当霍尔传感器与磁钢之间的相对位置变化时,霍尔传感器感受到的磁感应强度也随之变化,从而导致传感器的输出电压改变.采用三个霍尔传感器组成传感器阵列,建立三维笛卡儿坐标系.通过测量传感器的输出电压并结合一定的算法,可计算出某一时刻磁钢的三维坐标.地下土体的变形会改变霍尔传感器与磁钢之间的相对位置.在得到磁钢新的三维坐标之后,通过几何运算得出位移的大小.     

Output Properties of Zero-Speed Sensors Using FeCoV Wire and NiFe/CoFe Multilayer Thin Film

Output properties of magnetic sensors generating pulse voltages are described. The sensors principally consisted of double magnetic layers with different coercive forces. Both of thin-film-based material and wire-based material were used for the double layers. When the magnetization of one of the layers was switched by an external magnetic field, a pulse voltage was induced in a pickup-coil wound around the materials. The magnetic sensor using a twisted FeCoV wire, the conventional material for the Wiegand effect, had the disadvantage of the asymmetric output voltage generated by the alternative magnetic field. It was found that a magnetic wire, whose ends were slightly etched, exhibited symmetric output voltage. The sensor element consisting of a patterned NiFe/CoFe multilayer thin film was also studied. Constant output voltage was obtained from this thin-film sensor using an excitation magnetic field at frequencies down to 0.1 Hz.     

The theoretical output of a ring core fluxgate sensor

This article proves that the output from a ring core sensor is directly proportional to the first time derivative of the product of dynamic permeability and magnetic intensity perturbation within the core caused by an external, uniform magnetic field. (Dynamic permeability is defined to be the slope of the hysteresis loop at a given point in time.) Assuming that ellipsoidal shells can approximate the core, the demagnetization factor can be "estimated" in the first order to be proportional to the first power of the quantity tape thickness (or number of wraps) divided by the core diameter. The constant of proportionality is determined from laboratory data. When an additional scale adjustment is applied to the resulting sensor output formula, the computed output tracks laboratory data for a range of sensor geometries.     

Characterization of a magnetic field sensor based on torquemeasuring [for fusion diagnostics application]

A sensor for low-frequency measurements of the magnetic field is presented in the paper. It is based on measurements of an electromagnetic torque. An output directly proportional to the unknown magnetic field is produced. This method has the main advantage of avoiding the drift present in the integration of signals from inductive sensors. The design and construction criteria, aiming at an uncertainty of a few milliteslas in field measuring, are described. The analysis of the sensor linearity is presented in the paper together with the test rig, able to guarantee reproducible conditions. The dynamic behavior of the torque-based sensor is considered. It is studied either on the basis of the coil and load cell characteristics or analyzing the response to an applied known electromagnetic torque     

一种新型霍尔式角度传感器的研究

设计了一种新型霍尔式角度传感器,详细阐述了传感器的机械结构和工作原理,根据磁路定律和霍尔效应推导了传感器的输出特性,表明传感器工作时能够直接输出与旋转角度成正比的霍尔电势。由于霍尔传感器的输出采用差动式连接,不存在零点剩余电压。建立了传感器的有限元模型,对其工作时的磁场情况进行了仿真,验证了传感器测量原理的正确性。最后对传感器样机进行了特性测定,实验结果表明传感器的灵敏度约为105 mV/(°),线性误差约为0.12%,重复性误差约为0.19%。     

张力退火感生各向异性对纳米晶合金磁性能的影响

对Fe_74.1Cu₁Nb₃Si₁₅B_6.9(%,原子分数)纳米晶合金进行连续张力退火,研究了张力退火感生各向异性对纳米晶合金磁性能的影响。结果表明,张力退火产生的感生各向异性常数(K_u)与退火张力(σ)满足线性关系。随着退火张力的增大合金在f =5 kHz和H=3 A/m测试点的有效磁导率(μ_e)先增大后减小,且随着磁场和频率的提高有效磁导率(μ_e)的衰减减小。退火张力为67 MPa时有效磁导率(μ_e)在磁场强度H为0~800 A/m和频率f为1 k~3 MHz范围内保持约800,表现出恒导磁特性。同时,合金的单位质量损耗(P_m)随着退火张力的增大而减小,当退火张力为67 MPa时损耗为68 W/kg (测试条件：B_m=300 mT,f =100 kHz),与无张力退火相比下降约67%。同时,通过磁光克尔效应观察到张力退火后合金内部形成垂直于张力方向的180°片形畴,随着退火张力的增大磁畴宽度减小且趋于一致,退火张力为67 MPa时片形畴的宽度约为85 μm。     

On a new principle of a smart multisensor based on magnetic effects

In this paper, a new principle of a smart sensor is proposed, based on three different magnetic effects or operational modes, using the same sensor topology, which consists of a magnetic wire as sensing core, two coils as excitation or search means, and two electric contacts at the ends of the magnetic wire. The magnetic effects currently involved are magnetostriction, magneto-impedance and re-entrant flux reversal. Operating the sensor in these three different modes separately and sequentially, one can obtain the response of the sensor related to three different physical quantities, such as stress, temperature, and field. This paper refers to the first experimental results based on this principle, thus initiating the research work in this field. It has been experimentally observed that the total output of the sensor in each one of the three different modes is equal to the product of each corresponding physical quantity function concerned, provided that a given threshold of the ambient field and preloaded stress is used to bias the sensing element. Therefore, the three unknown parameters of stress, temperature, and field can be determined from a 3/spl times/3 matrix equation. Other magnetic effects may also be involved. Furthermore, other physical quantities may also be determined, such as position, pressure, load, etc.     

Factors affecting the sensitivity of gamma-level ring-core magnetometers

A theoretical and experimental analysis has been made of the geometrical and magnetic factors affecting the sensitivity of the ring-core magnetometer first introduced by Geyger in 1961. Using a drive-to-pickup transfer function derived from an assumed dynamic hysteresis loop and a given dc input signal, the second-harmonic output voltage was derived for both current-source and voltage-source driving conditions. Results of the analysis, which were confirmed by experiment, show the following. 1) When a single, diametrically wound (solenoid-type) pickup winding is used with a ring-core sensor, simultaneous minimization of both fundamental and second-harmonic feedthrough can be achieved by a simple rotational adjustment. This optimization is possible only with a circular core. 2) Sensitivity can be increased by increasing frequency, number of pickup turns, dynamic differential permeability, cross-sectional area, and effective sensor length, and by decreasing the dc initial permeability (μ0). 3) The dominant factor affecting the sensitivity is the demagnetizing termmu_{0}K = mu_{0}l^{-1.72} (4A/pi)^{0.86}, which determines the entrance attenuation of the dc signal to be measured. Highest sensitivity is obtained whenmu_{0}Kis small, which requires a low initial permeability, since a large dimensional ratiol/A^{1/2}is usually not attainable. When the demagnetizing term is not small, the sensitivity advantages of the other factors are negated by the input signal attenuation. Power considerations show that increasing sensitivity by raising area, length, or frequency results in increased power consumption. However, increasing sensitivity by using a pickup coil with a larger number of turns or by a sensor core with lower initial permeability can be achieved without additional power.     

用于应力监测的新型平面柔性涡流传感器

针对直升机旋翼轴应力监测的需求和轴部安装空间有限的实际情况,研制了一种新型平面柔性涡流传感器,并提出了相应的应力监测方法.该方法利用磁弹效应,通过建立平面涡流传感器和铁磁性被测对象的有限元仿真模型,得到传感器阻抗变化与对象磁导率的测量网格数据,可实现铁磁性被测对象的非接触或接触应力监测.搭建了拉应力实验平台,通过实验,验证了该方法的可行性,并得到了磁导率与拉应力的线性关系式,测量了增加的残余应力值.