| As a novel kind of intelligent material,Magnetoelectric(ME)composites can achieve magnetoelectricity conversion by mechanical coupling between magnetostrictive materials and piezoelectric materials,which have great potential applications in magnetic sensors,actuators.Amorphous alloy will be saturated under tens of oersted dc magnetic field,resulting in nonlinear magnetostrictive effect,thus amorphous alloy/piezoelectric composites will generate nonlinear magnetoelectric effect under the action of higher excitation magnetic field.The existing research shows that the induced ME voltage of odd harmonics is modulated by a weak dc/ac magenetic field to be measured without additional bias magnetic field.In this paper,the nonlinear magnetoelectric effects of amorphous alloys/piezoelectric composites are studied theoretically and experimentally.The ME dual-unit with small size based on two FeNiCoSiB/PZT/FeNiCoSiB is operated in 180 ° anti-phase modulated mode and differential output.In this design the ME voltage at even harmonics due to frequency doubling effect of magnetostriction is greatly attenuated.The performance of the ME dual-unit is improved.And its application in the field of geomagnetic detection and vehicle detection is explored.The specific work and main research are as follows:1)The mechanism of linear and nonlinear magnetoelectric effects is analyzed.According to the linear constitutive equations of magnetostrictive materials and piezoelectric materials,the model of linear magnetoelectric effect is analyzed.There is an optimal volume fraction for the magnetoelectric composite to make the magnetoelectric voltage maximum.Taking the influence of temperature and stress on magnetoelectric composite material into consideration,the theoretical model of nonlinear magnetoelectric effect is established.And the linear relationship between odd harmonics of magnetoelectric voltage and bias magnetic field is researched.2)The nonlinear magnetoelectric effect of amorphous alloy/piezoelectric composite is studied.With the increase of the amplitude of driving field,the ME voltage gradually changed from nonlinearity to linearity in the region around zero bias magnetic field.The sensitivity of the 1st harmonic to the bias magnetic field increases gradually.And an optimal driving field maximizes the sensitivity.No additional magnetic field is required to make the magnetoelectric compsite work in a linear region.3)The basic principle of sensitivity double and common mode noise suppression by differential 180° anti-phase-modulated nonlinear magnetoelectric effect is analyzed,and the correctness of the principle is verified by experiments.The experimental results show that the sensitivity of ME dual-unit is about twice that of a single ME unit.The minimum detection limits of differential magnetoelectric sensitive units placed parallel and coaxial to 1Hz magnetic field are 7×10-5Oe and 10-4Oe,respectively.The magnetoelectric sensor designed by differential 180° anti-phase-modulated nonlinear magnetoelectric effect has enhanced performance in the sensitivity,signal-to-noise ratio,stability and resolution.4)The coaxial configuration differential 180° anti-phase-modulated nonlinear magnetoelectric sensor is designed for geomagnetic detection and vehicle detection,and its detection performance is analyzed.The magnetoelectric sensor based on nonlinear magnetoelectric effect is comprised of differential 180° anti-phase modulation ME dual-unit,differential amplification and lock-in circuit.The sensitivity of the senor is 2.77V/Oe.The experimental results show that the magnetoelectric sensor can clearly determine the direction of geomagnetic field.By placing the magnetoelectric sensor in the middle of the parking space,the output of the sensor can reflect the details of the parking space occupied by the vehicle.In addition,magnetoelectric sensors can also be used to monitor the speed of vehicle. |
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