Reseach On The Model Of Magnetomechanical Coupling And Its Self-sensing Application On Giant Magnetostrictive Actuator

As a new kinds of smart material, Giant magnetostrictive material (GMM) canmake energy conversion between magnetic and mechanical reversible, has bothactuator and sensor function. The giant magnetostrictive actuator (GMA) based onGMM has many merits, such as quick response, large strain, heavy load, and highprecision, etc. It has good application in the field of precision drive, flow control,valve control, damping, energy converter. The angle deflection of magnetic domain,magnetization, magnetostriction of GMM is studied in this paper, optimization andsensing relation of effective magnetic field in GMA is analyzed, then sensingrelation of GMM and application theory of GMA suit for self-sensing application isestabilished. A small structure GMA is manufactured, and the test platform isconstructed. Application characteristics of GMA are calculated in experiment, usedto prove the self-sensing model of GMA. The research results could be adopted inconsummating the constitutive model of GMM magnetomechanical coupling andmagnetostriction. The GMA constructed in this paper would have good applicationvalue in micro flow control valve, and the works also have theoretical significancefor the self-sensing application of GMA.Firstly, magnetization of the constitutive model in GMM is studied in thispaper. Based on the minimum principle of free energy and theory of magneticdomain deflection, the angle rotation and jump effects of magnetic domain in GMMwith input loads are analyzed, used technology of coordinate conversion andgeometry solution. Then a simple numerical analysis method of the magneticdomain deflection is established for self-sensing application, which can directlyreveal magnetostricitive effects of GMM with different input loads. Based on thosetheories, the parameter dependence of numerical method in magnetic domaindeflection is studied, used to perfect magnetic domain deflection numercial methodof GMM. The research results indicate that piezomagnetic effect of GMM is helpfulfor domain accumulation in90°direction, not advantage for moment rotation andmagnetization in magnetostriction. Magnetic domain deflection of [110] orientationcrystal would be simplify to plane rotation, and jump effect happened betweenplanes of reversible domain rotation, in which the rotation and jump effects of35.3°angle domain is the key factor of GMM in piezomagnetic effect andmagnetostriction. Different anisotropy constant K1and K2could influence thecritical load value of angle jump effect in magnetic domain rotation, and numericalmethod of magnetic domain deflection has obvious dependence on the anisotropy constant and energy distribution factors.Based on the analysis of magetic domain deflection, the magnetostriction ofGMM in the magnetomechanical coupling process is studied. The constitutiveparameters identification of GMM in domain deflection numerical method arefinished by experimental result, that could consummate the domain deflectionmodel. Then, the magnetomechanical coupling theory and strain outputcharacteristic based on domain rotation are researched with input loads. The energyconversion are analyzed in the process of magnetomechanical coupling, andtwo-port equivalent circuit of energy conversion is established. The feasibility ofself-sensing application of GMM based on domain deflection numerical method isanalyzed, used to support the theoretical guiding for actuator self-sensingapplication. More that, correctional domain deflection numerical method coulddescribe magnetization and magnetostriction characteristic of GMM, prove effectthat large pressive stress could increase the effective output strain inmagnetostriction, and need larger magnetic field loads for domain rotation and itsmagnetization. The research result consummates the magnetomechanical couplingtheory, and it would support the theorical guiding for actutor self-sensing designand application.Thirdly, the magnetic and thermal problem in GMA are also studied,mathematics function between the magnetic field and magnetic sensing in actuatorsensing application are constructed. Structure of driving coil and space magneticfield in the GMA are optimized. The effective magnetic field distribution in thecondition of GMM permeability is analyzed, axial magnetic field anisotropy ofmaterial is revised, used to establish the function between driving current andmagnetic field with consideration of GMM permeability. Magnetic loss and heattransformation in GMA are studied, and thermal characteristics with differentcurrent conditions are simulated. The function of magnetic sensing in GMA isestablished, used to consummate self-sensing model for the GMA application. Theresearch results describe that different GMM permeability value would influencedistribution of axial magnetic field in material, special the magnetic field interminal part is larger than the center part, and large GMM permeability valuewould increase the uniformity of axial magnetic field and decrease the averagemagnetic field in the material.Finally, the GMA prototype is designed and manufactured, the test platform isestablished. The output strain, output impact force, temperature characteristics aretested in this platform, the dynamic characteristic with different frequency isstudied. Experiments prove the validity of GMM sensing relation and GMA self-sensing application model. Results indicate that the GMA has3.6MPa impactstress and45μm output mechanical characteristic in the condition of15MPa pressstress, and it would has maximum12.5MPa output stress. The GMA designed in thispaper is suitable for the large strain load in actuator and damping field application.GMA has hysteresis with static and dynamic driving current, and has goodrepetition hysteresis curves. Its first dynamic syntony frequency is1200Hz, andmagnetomechanical coefficient could up to0.572. Specially, below the syntonyfrequency, the strain should have the positive frequency coefficient, the straindecreases against increasing frequency under larger syntony frequency. In thevalidation of GMM self-sensing, the deviation of pressive stress could reach0.5~0.6, and the maximum error between the self-sensing and test value is below2.5μm, the repeated test error of experimentals is approximately1μm. Those resultscould prove the validity of numerical method in domain deflection and feasibility ofself-sensing application in GMA.