Mechanism And Experimental Research Of Impact Force Detection Based On Galfenol Alloy

Fe-Ga alloys(Galfenol)are typical magnetostrictive materials,which undergo magnetization changes when subjected to external magnetic field or mechanical stresses.They are alloys with moderate magnetostrictive properties as well as good mechanical properties.Unlike intelligent materials such as piezoelectric materials,optical fiber materials,and memory alloys etc,Galfenol alloys are less fragile which can withstand large tensile and compressive stresses,leading to a great potential and advantage in application of impact force detection.In this dissertation,the Galfenol alloys are employed as the sensitive elements to develop the impact force sensors and a series of studies on the impact detection mechanism of Galfenol alloys have been carried out:(1)The impact force sensors based on magnetostrictive materials Galfenol are designed.Two configurations including rod based and beam based sensors are proposed according to the different forms of the sensitive elements.The force sensing principle is described based on the domain theory.The free energy formulas of Galfenol are derived.In this case,the magnetic susceptibility model of Galfenol is established and the relationship between sensor's sensitivity and stress is solved.Then the sensitivity relationship of the sensor is reflected via the strain relationship.(2)Considering the damping effect of sensitive elements,the kinetic models of sensitive elements are developed based on the continuous vibration theory.The models are solved via the mode superposition method and Duhamel integral.Then the model outputs of the two configurations are compared under the same input impulse force.(3)The uniform I beam and the non-uniform I beam are proposed and the kinetic models for these two configurations are developed.The structural dimensions of the two configurations are optimized by orthogonal design method to further improve the sensitivity of the sensors.Then the strain outputs of the four configurations(uniform rod,uniform beam,uniform I beam,and non-uniform I beam),which characterize sensitivities,are compared under the input impact with the same amplitude and pulse width.(4)The hysteresis phenomenon is described and explained.Based on the domain theory,micromagnetics and Weiss molecular field theory,a magneto-mechanical coupling model of Galfenol is established via the Jiles-Atherton model considering the effect of stress rate on magnetization process.Then the magneto-mechanical coupling model of Galfenol alloy is simulated via MATLAB software,and the magnetization curve is obtained by numerical method.The comparison between the simulation results and the experimental results shows good coincidence,which verifies the reliability and accuracy of the model.(5)To investigate the impact properties of Galfenol alloys,the rod based and nonuniform beam based sensors are fabricated and experimentally studied respectively.Then the sensor with non-uniform beam sensitive element is further experimentally investigated.A nonlinear Levenberg-Marquardt fitting method is used to calibrate the sensor and the accuracy of the calibration function is verified by experiments.The above research establishes a foundation for the research of Galfenol impact force detection.