This paper presents an analytical method for electromagnetic acoustic transducers （EMATs） under voltage excitation and considers the non-uniform distribution of the biased magnetic field. A complete model of EMATs i...This paper presents an analytical method for electromagnetic acoustic transducers （EMATs） under voltage excitation and considers the non-uniform distribution of the biased magnetic field. A complete model of EMATs including the non-uniform biased magnetic field, a pulsed eddy current field and the acoustic field is built up. The pulsed voltage excitation is transformed to the frequency domain by fast Fourier transformation （FFT）. In terms of the time harmonic field equations of the EMAT system, the impedances of the coils under different frequencies are calculated according to the circuit-field coupling method and Poynting＇s theorem. Then the currents under different frequencies are calculated according to Ohm＇s law and the pulsed current excitation is obtained by inverse fast Fourier transformation （IFFT）. Lastly, the sequentially coupled finite element method （FEM） is used to calculate the Lorentz force in the EMATs under the current excitation. An actual EMAT with a two-layer two-bundle printed circuit board （PCB） coil, a rectangular permanent magnet and an aluminium specimen is analysed. The coil impedances and the pulsed current are calculated and compared with the experimental results. Their agreement verified the validity of the proposed method. Furthermore, the influences of lift-off distances and the non-uniform static magnetic field on the Lorentz force under pulsed voltage excitation are studied.展开更多
There are the application scope limits for single differential-mode current injection test method, so in order to carry out injection susceptibility test for two-pieces equipment interconnected with both ends of a cab...There are the application scope limits for single differential-mode current injection test method, so in order to carry out injection susceptibility test for two-pieces equipment interconnected with both ends of a cable simultaneously, a double differential-mode current in- jection test method (DDMCI) is proposed. The method adopted the equivalence source wave theorem and Baum-Liu-Tesche(BLT) equation as its theory foundation. The equivalent corresponding relation between injection voltage and radiation electric field intensity is derived, and the phase relation between the two injection voltage sources is confirmed. The results indicate that the amplitude and phase of the equivalent injection voltage source is closely related to the S parameter of directional coupling device, the transmission line length, and the source vector in BLT equation, but has nothing to do with the reflection coefficient between the two equipment pieces. Therefore, by choosing the right amplitude and phase of the double injection voltage sources, the DDMCI test is equivalent to the radiation test for two interconnected equipment of a system.展开更多
在悬浮磁偶极场约束装置中,姿态控制系线圈(Tilt-Slide-Rotate,TSR)或者由高能量的粒子共振(Resonant Line Field,RLF)激发磁场会破坏背景磁场的拓扑结构,进而影响粒子约束。由于α粒子是DD-3He催化核反应产物之一,能否在TSR线圈和RLF...在悬浮磁偶极场约束装置中,姿态控制系线圈(Tilt-Slide-Rotate,TSR)或者由高能量的粒子共振(Resonant Line Field,RLF)激发磁场会破坏背景磁场的拓扑结构,进而影响粒子约束。由于α粒子是DD-3He催化核反应产物之一,能否在TSR线圈和RLF效应产生的磁场扰动中稳定约束高能量α粒子,对于加热背景等离子体的研究具有非常重要的意义。本研究中背景磁偶极场是通过偶极场平衡代码求解一个交换稳定的平衡得到的,在TSR线圈倾斜和偏移的工作模式下,对粒子投掷位置和TSR线圈工作电流α粒子约束时间和空间特性进行统计,同时在背景磁偶极场中叠加环向磁场方法模拟低极向扰动模数的磁场。由于TSR线圈产生磁场会破坏背景磁偶极场闭合磁场线的结构,使得投掷位置靠近TSR线圈侧的α粒子迅速损失。在RLF效应引发的模数n=0和n=1的极向扰动磁场中,在10μs内,n=0极向扰动磁场比n=1的磁扰动约束粒子份额更高,且当α粒子飞行时间大于10μs后,n=0模式下约束粒子份额迅速减少。展开更多
为深入研究螺纹钻压灌桩的抗拔承载特性,开展了3组现场竖向抗拔静载试验,建立了三维有限元模型,分析了抗拔承载力的影响因素,并建立基于灰狼优化(grey wolf optimizer,GWO)算法的数据分组处理方法(group method of data handling,GMDH)...为深入研究螺纹钻压灌桩的抗拔承载特性,开展了3组现场竖向抗拔静载试验,建立了三维有限元模型,分析了抗拔承载力的影响因素,并建立基于灰狼优化(grey wolf optimizer,GWO)算法的数据分组处理方法(group method of data handling,GMDH)模型,对螺纹钻压灌桩抗拔承载力进行预测。结果表明:桩周岩土体物理力学性质越好,螺纹钻压灌桩的抗拔力越强;桩土界面参数对螺纹钻压灌桩抗拔力的影响较小;随着螺纹间距与螺牙宽度的不断增大,螺纹钻压灌桩抗拔承载力呈现先增大后减小的趋势;所建立的GWO-GMDH模型可用于螺纹钻压灌桩抗拔承载力预测。展开更多
基金Project supported by the National Natural Science Foundation of China (Grant No. 10974115)
文摘This paper presents an analytical method for electromagnetic acoustic transducers （EMATs） under voltage excitation and considers the non-uniform distribution of the biased magnetic field. A complete model of EMATs including the non-uniform biased magnetic field, a pulsed eddy current field and the acoustic field is built up. The pulsed voltage excitation is transformed to the frequency domain by fast Fourier transformation （FFT）. In terms of the time harmonic field equations of the EMAT system, the impedances of the coils under different frequencies are calculated according to the circuit-field coupling method and Poynting＇s theorem. Then the currents under different frequencies are calculated according to Ohm＇s law and the pulsed current excitation is obtained by inverse fast Fourier transformation （IFFT）. Lastly, the sequentially coupled finite element method （FEM） is used to calculate the Lorentz force in the EMATs under the current excitation. An actual EMAT with a two-layer two-bundle printed circuit board （PCB） coil, a rectangular permanent magnet and an aluminium specimen is analysed. The coil impedances and the pulsed current are calculated and compared with the experimental results. Their agreement verified the validity of the proposed method. Furthermore, the influences of lift-off distances and the non-uniform static magnetic field on the Lorentz force under pulsed voltage excitation are studied.
基金Project supported by Arm Pre-research Program （51333040101）, National Defense 973 Program （6131380301 ）, National Natural Science Foundation of China （61040003）.
文摘There are the application scope limits for single differential-mode current injection test method, so in order to carry out injection susceptibility test for two-pieces equipment interconnected with both ends of a cable simultaneously, a double differential-mode current in- jection test method (DDMCI) is proposed. The method adopted the equivalence source wave theorem and Baum-Liu-Tesche(BLT) equation as its theory foundation. The equivalent corresponding relation between injection voltage and radiation electric field intensity is derived, and the phase relation between the two injection voltage sources is confirmed. The results indicate that the amplitude and phase of the equivalent injection voltage source is closely related to the S parameter of directional coupling device, the transmission line length, and the source vector in BLT equation, but has nothing to do with the reflection coefficient between the two equipment pieces. Therefore, by choosing the right amplitude and phase of the double injection voltage sources, the DDMCI test is equivalent to the radiation test for two interconnected equipment of a system.
文摘在悬浮磁偶极场约束装置中,姿态控制系线圈(Tilt-Slide-Rotate,TSR)或者由高能量的粒子共振(Resonant Line Field,RLF)激发磁场会破坏背景磁场的拓扑结构,进而影响粒子约束。由于α粒子是DD-3He催化核反应产物之一,能否在TSR线圈和RLF效应产生的磁场扰动中稳定约束高能量α粒子,对于加热背景等离子体的研究具有非常重要的意义。本研究中背景磁偶极场是通过偶极场平衡代码求解一个交换稳定的平衡得到的,在TSR线圈倾斜和偏移的工作模式下,对粒子投掷位置和TSR线圈工作电流α粒子约束时间和空间特性进行统计,同时在背景磁偶极场中叠加环向磁场方法模拟低极向扰动模数的磁场。由于TSR线圈产生磁场会破坏背景磁偶极场闭合磁场线的结构,使得投掷位置靠近TSR线圈侧的α粒子迅速损失。在RLF效应引发的模数n=0和n=1的极向扰动磁场中,在10μs内,n=0极向扰动磁场比n=1的磁扰动约束粒子份额更高,且当α粒子飞行时间大于10μs后,n=0模式下约束粒子份额迅速减少。
文摘为深入研究螺纹钻压灌桩的抗拔承载特性,开展了3组现场竖向抗拔静载试验,建立了三维有限元模型,分析了抗拔承载力的影响因素,并建立基于灰狼优化(grey wolf optimizer,GWO)算法的数据分组处理方法(group method of data handling,GMDH)模型,对螺纹钻压灌桩抗拔承载力进行预测。结果表明:桩周岩土体物理力学性质越好,螺纹钻压灌桩的抗拔力越强;桩土界面参数对螺纹钻压灌桩抗拔力的影响较小;随着螺纹间距与螺牙宽度的不断增大,螺纹钻压灌桩抗拔承载力呈现先增大后减小的趋势;所建立的GWO-GMDH模型可用于螺纹钻压灌桩抗拔承载力预测。
