磁弹噪讯技术无损检测铁磁材料疲劳损伤

铁磁材料加工制造的机械构件，在服役的过程中，受外力作用、在其内部会产生应力集中与松驰，引起构件局部或全部的扭曲、变形，造成构件的疲劳，使设备运行不安全或破损，对铁磁构件内部应力和疲劳寿命检测一直是人们重视的检测难题。从工程应用的角度，迫切需要一种既能检测构件应力大小，分布以及构件的疲劳，而不需要通过测量应变而测应力，并能瞬间、定点、在线的检测方法，铁磁构件在交变磁场的作用下，磁畴壁的不连续运动在其表面释放一种磁弹波--巴克毫森噪讯。该巴氏噪讯对材料所受外加载荷及材料的微观结构的变化十分敏感。采用该技术可开展在线无损检测铁磁构件服役应力及疲劳损伤。本文介绍该技术的原理及对平板构件疲劳损伤无损检测的实验结果。     

二维磁等离子体目标FDTD分析的移位算子方法

采用移位算子(SO)方法把时域有限差分(FDTD)法推广应用于二维磁化等离子体中.证明电磁波横向入射二维轴向磁化等离子体目标情形下,电磁波可按目标的轴向分解为横电波(TE波)和横磁波(TM波),而且TM波的散射特性与外磁场无关,而TE波的散射特性与介质电磁参数密切相关,同时对其物理原因进行了分析.采用SO方法处理磁化等离子体频域本构关系,得到该情形下目标电磁散射的SO-FDTD迭代计算公式.计算了轴向磁化等离子体涂敷Von Karm an型导体柱的TE波双站雷达散射截面(RCS),分析了涂层厚度以及等离子体参数对其双站RCS的影响.结果表明,恰当地选择等离子体参数能有效地减少目标在一定散射角范围内的RCS.     

工业场景电磁噪声测量及建模分析

工厂环境的电磁噪声会对以低功耗无线传感设备为核心的工业物联网技术产生巨大的影响.为此,应用对数周期天线与频谱仪,从时域和频域2个角度在某汽车厂的焊接车间和办公区测量电磁噪声.频域测量得到了0.3~3 GHz频段工厂中电磁噪声的频点、功率等信息,噪声频谱呈现尖峰形状,可运用截断拉普拉斯分布进行建模分析.时域测量采集了315、779、916 MHz几个频点的噪声数据,提取了噪声的幅度概率分布、脉冲持续时间分布、脉冲间隔时间分布3个参数.测量结果表明,天线水平、垂直极化方式测得噪声信号相近;办公区受噪声影响比焊接车间内部小.     

电子回旋波在等离子体中的传播

研究了电子回旋波在均匀磁等离子体的传播和吸收,讨论了不同的入射波垂直进入均匀磁等离子体的吸收衰减情况.计算表明,当波的频率接近等离子体中的电子回旋频率时,磁等离子体对波的吸收达到最大值.当入射波的频率增加时,均匀磁等离子体对波的衰减随入射波频率的增加而减小,并伴随着等离子体密度的增大,磁等离子体对波的衰减在增大.     

摆动磁场条件下的焊接接头组织研究

为了优化不锈钢焊接工艺,提高焊接质量,进行了外加电磁场条件下的304不锈钢钨极氩弧焊(TIG),磁场施加方式分别为横向磁场和旋转磁场.焊后采用电子显微镜对焊接接头进行显微组织观察,研究了不同外加磁场类型和不同焊接速度对不锈钢焊接接头组织的作用规律.试验结果表明,外加磁场改变了熔池的流动形态,使金属液由四周向中心流动并伴有搅拌,也使焊缝熔深增大的同时,抑制柱状晶的形成,细化组织.     

矿集区强噪声对大地电磁测深三个采样率的影响规律

天然大地电磁场信号微弱,极化方向随机,极易受电磁噪声污染.矿集区人烟稠密、工业发达,区内强烈的工业、通讯、矿山、民用等电磁干扰严重污染了大地电磁测深数据.本文利用数学形态学从受严重污染的电磁场时间序列中提取出类方波、三角波、阶跃、脉冲和充放电5种典型噪声的波形,以不同的方式将这些噪声波形与区内基本未受噪声污染的测点（D1139）的电磁场波形叠加,对比分析了不同采样率加噪后D1139点的测深曲线的变化.结果表明：24Hz采样率,方波噪声、三角波噪声、阶跃噪声、允放电噪声等会使得视电阻率、相位曲线出现类似近源干扰特征,脉冲噪声使测深曲线出现畸变;320Hz采样率,方波没有明显影响,三角波、阶跃噪声、脉冲噪声使曲线部分频点出现跳变,而充放电噪声会使曲线出现类似近源干扰特征;2560Hz采样率,方波、充放电噪声没有明显影响,三角波、阶跃噪声、脉冲噪声则使曲线出现了不同程度的畸变.     

逆焊接处理对不同材料抗应力腐蚀性能的影响

介绍了采用逆焊接加热处理的方法对Q235、16MnR、20g钢等不同材料在酸性和碱性溶液中抗应力腐蚀性能的影响及机理。将每种材料的试件进行加热处理,再用冷却介质只对焊缝处进行快速冷却,从而获得与焊接温度场相反的负温差,降低焊接过程中产生的残余应力。经过350℃处理后的Q235和16MnR钢,在酸性溶液中的腐蚀速率比未处理时分别降低了66.1%和67.9%。实验结果表明,逆焊接加热处理有效的降低了焊接残余应力,并且减缓了应力腐蚀速率,适用于有防止应力腐蚀要求的焊接结构使用。     

基于多向电磁力的永磁同步电机电磁噪声分析

针对电机电磁噪声分析中主要关注径向电磁力而忽略电磁力分量,造成分析精度不准确的问题,对某8极24槽车用永磁同步驱动电机进行电磁仿真分析,得到电机磁场以及电磁力分布. 在电机定子模型上分别单独加载径向电磁力和综合加载径向、切向及轴向三向电磁力,对比分析电磁噪声. 采用边界元法计算电机电磁噪声,通过试验验证仿真分析的准确性. 建立电机参数化结构模型,分析不同定子槽口宽度和磁体圆角半径对径向和切向电磁力以及电磁噪声的影响. 结果表明,切向电磁力对电磁噪声有一定程度的影响,且加载径向、切向及轴向电磁力的电机定子模型更加真实可靠;合理减小定子槽宽和磁铁圆角半径可以有效降低电机电磁噪声.     

Analysis and evaluation of electromagnetic vibration and noise in permanent magnet synchronous motor with rotor step skewing

In this paper, a multi-physics simulation model capable of electromagnetic noise prediction is established, and the effectiveness of the established simulation model in predicting and evaluating electromagnetic noise is verified. Based on the verified motor model, a rotor step skewing model which can affect electromagnetic noise is proposed, and the influence of the skewing angle on electromagnetic noise is investigated in detail. By studying the spectral characteristics of the low-order radial magnetic force which has a great influence on electromagnetic noise, the distribution of electromagnetic noise characteristics of the permanent magnet synchronous motor(PMSM) with or without the rotor step skewing is compared and analyzed. Therefore, it lays a technological foundation for predicting and suppressing the electromagnetic vibration noise of electric vehicle(EV) driving motor in the electromagnetic design.     

单相开关磁阻电机径向力的研究

针对开关磁阻电机特殊双凸极结构和非线性磁饱和产生较大电磁噪声的问题,设计一台相数最少的新型结构单相开关磁阻电机。对引起电磁噪声的径向力进行计算,分析径向力的产生原理和分布情况,采用有限元仿真软件Ansoft对其进行静态和动态磁场的仿真,并从结构参数出发对定子所受径向力进行优化,从而减少单相开关磁阻电机的电磁噪声和转矩脉动。     

Effects of electromagnetic induction and noise on the regulation of sleep wake cycle

As an exploration of electromagnetic induction effects on homeostatic regulation of sleep wake cycle, a magnetic flux term coupled with membrane current is proposed as an equivalent induction current act on a physiologically-motivated mathematical model, to study the effects of electromagnetic induction and its noise on the sleep wake cycle. The basic model includes 2 simplified Hodgkin-Huxley type neurons connected via glutamate(Glu) synapses, one of which additionally contains hypocretin/orexin(Hcrt/ox) as the functionally relevant co-transmitter. The numerical results suggest that when a constant current(DC) stimulus is applied to the model, the average fire frequency of the Hcrt/ox neuron could be modified from gamma to delta frequency with increased the intensity of electromagnetic induction, but the local Glu neuron transforms active into sleep state.Additionally, the homeostatic regulation function has better robustness to electromagnetic induction and its noise than the current or conductance noise, even there is a similar stochastic resonance phenomenon. For the circadian current input case, the time of wake up is delayed and fall asleep is advanced when the electromagnetic induction and its noise is considered. Furthermore, the effects of electromagnetic noise on the regulation is not significant, but only to inhibit the neuronal discharge activities and change the time of wake up and fall asleep of the Glu neuron, characterized by the sleep duration is slightly prolonged with increasing the strength of noise intensity.     

边界元辅助焊接残余应力计测的研究

提出了边界元辅助焊接残余应力的无损测试方法,该方法将焊接变形作为已知边界条件,通过边界积分方程及其离散形式──边界元法来求解焊接残余应力,推导出了计算公式,构造了算法和步骤,编制了相应的计算机程序,通过用应力释放法对几块典型焊接试板中的二维焊接残余应力进行实测,验证了该方法的合理性与可行性。     

纤维复合材料构件的受力分析原理

纤维复合材料与钢筋混凝土有本质上的一致性,即在一种连续介质中镶嵌另一种连续介质组成。为了揭示这种材料组织的构件受力后的内产应,建立起这类年的分析模型,采用两种介质的力学特性分阶段赋予的方法并找出了两种介质均处于弹性阶段时材料相间界面上的相互牵连作用,界面上的相互作用实质上是界面约束。     

窄带滤波微流量电磁流量计的相关技术

微流量信号是叠加着多种噪声干扰的弱信号,为了准确提取流速信号,在电磁流量计中采用窄带滤波信号调理技术,滤除高次谐波,取出信号基波,再经相敏解调、低通滤波消除微分噪声和同相噪声,提高微流量信号的信噪比.根据窄带滤波对交变磁场的要求,提出并制作每个周期内激磁电流平均值恒定的恒均值电流源.对其在环境温度、电网电压发生变化时的稳定性进行了理论分析和实测验证.实际应用证明,可将电磁流量计测量下限扩展到0.002m3/h,实现微流量准确测量.     

A novel absolute displacement detecting magnetic sensor

A novel magnetic grating based on calibration was proposed.Two tracks,look-up track and index track,were used to realize absolute output.Magnets of look-up track were magnetized according to N-S-N-S,and magnetic field was sensed by 6 linear Hall sensors.Three signals whose phase shift is 120° were obtained through difference,and the offset of magnetic head in a signal period could be obtained by look-up table;Magnets of index track were magnetized according to pseudorandom binary sequence.Hall sensors were used to get the absolute offset of the signal period to which the magnetic head is belonged.The magnetic grating was calibrated using a higher resolution optical grating:output of optical grating and signals from magnetic grating were sampled at the same time and transmitted to computer,the relation between them could be got and stored in MCU for looking-up.The displacement was got according to Hall signals while in working state.A magnetic grating prototype was made,and it could realize absolute detecting in 2048 mm and the resolution could achieve to 0.001 mm.Its structure is simple,cost is very low and it is suitable for mass production.     

基于三重相关的电磁检测信号处理

本文把三重相关技术应用于电磁检测中的磁信号分析处理。通过试验研究表明,三重相关技术可以有效地从噪声中恢复磁信号波形,特别是在低信噪比的情况下尤其明显,为电磁检测实际磁信号分析提供一种可供选择的方法。     

复合左/右手传输线的电磁特性及其潜在应用

复合左/右手传输线是右手材料和左手材料复合而成的新型传输线,它较一般传输线可以在不同的频率范围内表现出不同的电磁特性。当等效介电常数和等效磁导率同时为负值时表现出＂左手特性＂,而在其它频率范围内表现出＂右手特性＂,同时,复合左/右手传输线还可以进行相位调整。分析了复合左/右手传输线的电磁特性,并指出复合传输线的潜在应用。     

逆变TIG焊电源控制特性及其新型变压器的研究

介绍了一种新型逆变ＴＩＧ焊电源，该电源的变压器选用了非晶态磁性材料作为磁芯，并采用了新型的输出外特性控制电路和引弧控制电路，为提高逆变弧焊电源的可靠性作了有益的探索．     

Electrical activities of neural systems exposed to sinusoidal induced electric field with random phase

The brain neural system is often disturbed by electromagnetic and noise environments, and research on dynamic response of its interaction has received extensive attention. This paper investigates electrical activity of Morris-Lecar neural systems exposed to sinusoidal induced electric field(IEF) with random phase generated by electromagnetic effect. By introducing a membrane depolarization model under the effect of random IEF, transition state of firing patterns, including mixed-mode oscillations(MMOs) with layered inter-spike intervals(ISI) and intermittency with a power law distribution in probability density function of ISI, is obtained in a single neuron. Considering the synergistic effects of frequency and noise, coherence resonance is performed by phase noise of IEF under certain parameter conditions. For the neural network without any internal coupling, we demonstrate that synchronous oscillations can be induced by IEF coupling, and suppression of synchronous spiking is achieved effectively by phase noise of IEF. Results of the study enrich the dynamical response to electromagnetic induction and provide insights into mechanisms of noise affecting information coding and transmission in neural systems.     

外加纵向磁场对MAG焊焊缝成形的影响机理

将纵向磁场引入到Ar+2%O2保护的射流过渡MAG焊中,借助高速摄像手段研究了外加纵向磁场对MAG焊电弧形态及运动行为的作用特点,并且分析了励磁电流的大小及其极性对焊缝成形的影响规律,分别从旋转电弧加热工件的特点和电磁搅拌2个方面揭示了外加纵向磁场对MAG焊焊缝成形的作用机理.