The Mechanic-Magneto-Thermal Nonlinear Constitutive Theory Of Giant Magnetostrictive Materials And Its Application

Giant magnetostrictive material is a kind of functional material that can realize the conversion between magnetic energy and mechanical energy,and the giant magnetostrictive materials have been widely used in the fields of ordnance,electronics,aviation,and so on.At present,there are a large number of studies on giant magnetostrictive materials,such as the mechanical-magneto-thermo coupling effect,the magnetic hysteresis characteristic,magnetoelectric composite materials and the functional device,and so on.It is found that the theoretical research on the nonlinear multi-physics fields coupling effect of the giant magnetostrictive material is still insufficient,and the theoretical research work on the hysteresis characteristic of the electric field regulation has not been found,and the theoretical research work on the magnetoelectric effect of the three-layer asymmetric magnetoelectric laminate material has also not been found.Therefore,for the above-mentioned problems,this paper has carried on the following work:Firstly,using continuum mechanics theory and thermodynamic equation,the Gibbs free energy of the giant magnetostrictive material is subjected to Taylor expansion and derivation operations to obtain the polynomial expressions of strain and magnetic field.And then the polynomial expressions are simplified.So the nonlinear mechanical-magneto-thermo multi-physics fields coupling constitutive model has been established,and then three material parameters have also been deduced.The model not only has a concise form,but also introduces the saturation magnetization at different temperatures.It accurately describes the magnetostrictive curves and magnetization curves under the joint action of different temperatures and prestresses.Moreover,the validity of the model is verified by the existing experimental results.The content of this chapter can provide the relevant theoretical basis for the experimental study in the temperature stability region.Secondly,based on the above established model and the experimental study of the magnetic properties of magnetoelectric composite in the electric field regulation,the theoretical expression with the magnetic hysteresis characteristic of the magnetic layer under electric field regulation is proposed.And the magnetoelectric coupling coefficient expression with the magnetic hysteresis characteristic is also deduced.Inthe same way,the validity of the two expressions is verified by the existing experimental results.Then,the magnetostrictive strain,magnetization,piezomagnetic coefficient,magnetoelectric coupling coefficient changing with the magnetic field are predicted at a given electric field and at different temperatures,which have the magnetic hysteresis characteristic.The content of this chapter can provide theoretical guidance for the research work of the storage devices under the action of electric field and multi physics field.Finally,from the perspective of enhancing magnetoelectric coupling effect and based on the composition of magnetostrictive layer of composite material,a theoretical model is established for the non-symmetric magnetoelectric laminate.The research method of the model is different from the previous equivalent circuit method,which avoids the introduction of some complex physical parameters and reduces the computational difficulty.In the same way,the validity of the model is verified by the existing experimental results.Then,the magnetoelectric coupling coefficient changing with the thickness ratio of the piezoelectric material,the pre-stress and the temperature are respectively analyzed.From the above analysis,we can see that the magnetoelectric composite will produce strong magnetoelectric effect under the appropriate pre-stress and suitable environment temperature.