Study on magneto-elastic-plastic deformation characteristics of ferromagnetic rectangular plate with simple supports

In this paper, the magnetic-elastic-plastic deformation behavior is studied for a ferromagnetic plate with simple supports. The perturbation formula of magnetic force is first derived based on the perturbation technique, and is then applied to the analysis of deformation characteristics with emphasis laid on the analyses of modes, symmetry of deformation and influences of incident angle of applied magnetic field on the plate deformation. The theoretical analyses offer explanations why the configuration offer- romagnetic rectangular plate with simple supports under an oblique magnetic field is in-wavy type along the x-direction, and why the largest deformation of the ferromagnetic plate occurs at the incident angle of 45°for the magnetic field. A numerical code based on the finite element method is developed to simulate quantitatively behaviors of the nonlinearly coupled multi-field problem. Some characteristic curves are plotted to illustrate the magneto--elastic-plastic deflections, and to reveal how the deflections can be influenced by the incident angle of applied magnetic field. The deformation characteristics obtained from the numerical simulations are found in good agreement with the theoretical analyses.

Tunability of Band Gaps in Two-Dimensional Phononic Crystals with Magnetorheological and Electrorheological Composites

The elastic wave propagation properties of phononic crystals(PnCs)composed of an elastic matrix embedded in magnetorheological and electrorheological elastomers are studied in this paper.The tunable band gaps and transmission spectra of these materials are calculated using the finite element method and supercell technology.The variations in the band gap characteristics with changes in the electric/magnetic fields are given.The numerical results show that the electric and magnetic fields can be used in combination to adjust the band gaps effectively.The start and stop frequencies of the band gap are obviously affected by the electric field,and the band gap width is regulated more significantly by the magnetic field.The widest and highest band gap can be obtained by combined application of the electric and magnetic fields.In addition,the band gaps can be moved to the low-frequency region by drilling holes in the PnC,which can also open or close new band gaps.These results indicate the possibility of multi-physical field regulation and design optimization of the elastic wave properties of intelligent PnCs.

The effects of interface scattering on thermoelectric properties of film thermoelectric materials

A theoretical model taking into consideration the interface effects is established to predict the Seebeck coefficient and the electrical conductivity for a polycrystalline thermoelectric(TE)thin film.The interface scattering mechanisms(including the film-surface scattering and grain-boundary scattering)of the transport electrons in the film materials are revealed.The relations between the Seebeck coefficient,the electrical conductivity and the interface parameters(the film-surface reflection coefficient and the grain-boundary transmission coefficient)are then discussed with respect to the proposed model.The differences in the TE properties between the films and bulk materials caused by size restriction are investigated.The results indicate that the higher grain number leads to stronger grain-boundary scattering and more distinct size effects of the TE properties.In contrast to the surface effect,the grain-boundary effect plays a main role in the TE properties of TE films with polycrystalline structures.

Tunability of Band Gaps of Programmable Hard-Magnetic Soft Material Phononic Crystals

In this paper,the elastic wave band gap characteristics of two-dimensional hard-magnetic soft material phononic crystals(HmSM-PnCs)under the applied magnetic field are studied.Firstly,the relevant material parameters of hard-magnetic soft materials(HmSMs)are obtained by the experimental measurement.Then the finite element model of the programmable HmSM-PnCs is established to calculate its band structure under the applied magnetic field.The effects of some factors such as magnetic field,structure thickness,structure porosity,and magnetic anisotropy encoding mode on the band gap are given.The results show that the start and stop frequencies and band gap width can be tunable by changing the magnetic field.The magnetic anisotropy encoding mode has a remarkable effect on the number of band gaps and the critical magnetic field of band gaps.In addition,the effect of geometric size on PnC structure is also discussed.With the increase of the structure thickness,the start and stop frequencies of the band gap increase.