Kotaro Mori

Characteristics of vibration energy harvesting using giant magnetostrictive cantilevers with resonant tuning

This work deals with the dynamic bending and energy harvesting characteristics of giant magnetostrictive cantilevers with resonant tuning both numerically and experimentally. The giant magnetostrictive cantilever is fabricated using a thin Terfenol-D layer, SUS layer, movable proof mass, etc, and, is designed to automatically adjust its own resonant frequency to match the external vibration frequency in real time. Three-dimensional finite element analysis was conducted, and the resonant frequency, induced voltage and stress in the magnetostrictive cantilevers were predicted. The resonant frequency and induced voltage were also measured, and comparison was made between simulation and experiment. The time-varying behavior and self-tuning ability are discussed in detail.

Dynamic electromagneto-mechanical behavior of clamped-free giant magnetostrictive/piezoelectric laminates under AC electric fields

This work deals with the dynamic electromagneto-mechanical behavior of clamped-free giant magnetostrictive/piezoelectric laminates under AC electric fields both numerically and experimentally. The laminate is fabricated using thin magnetostrictive Terfenol-d and piezoelectric PZT layers. The magnetic field-dependent magnetoelastic constant and domain wall motion effect were incorporated to describe the nonlinear behavior of Terfenol-d and PZT layers, respectively, and three-dimensional finite element analysis was employed to calculate the displacement, stress and induced magnetic field. Experiments were also conducted to measure the displacement and induced magnetic field for the magnetostrictive/piezoelectric laminates under AC electric fields. Comparison was then made between simulation and experiment.

Three-Point Bending Fracture Behavior of Cracked Giant Magnetostrictive Materials Under Magnetic Fields

This paper numerically and experimentally investigated the three-point bending fracture behavior of cracked giant magnetostrictive materials under magnetic fields. Three-point bending fracture tests were carried out using the single-edge precracked-beam (SEPB) specimens, and the fracture loads were measured under magnetic fields. The crack was created normal to the direction of easy magnetization. Plane strain finite element analysis (FEA) was also performed, and the effect of magnetic fields on the energy release rate and on the apparent fracture toughness (critical energy release rate obtained using the fracture load) was discussed in detail. To the authors knowledge, this work is the first attempt to study the effect of magnetic fields on the fracture behavior of giant magnetostrictive materials.

Electromagneto-mechanical fields of giant magnetostrictive/piezoelectric laminates under concentrated load

This paper presents the nonlinear electromagneto-mechanical behavior of magnetostrictive/piezoelectric laminates under three-point bending both numerically and experimentally. The laminates are fabricated using thin Terfenol-D and PZT layers. The three-point bending test was conducted on the Terfenol-D/PZT laminates, and the displacement, induced magnetic field and induced voltage due to mechanical loads were measured. Three-dimensional finite element analysis was also carried out, and the electromagneto-mechanical fields in the laminates were predicted by introducing a second-order magnetoelastic constant for Terfenol-D. Comparison was then made between simulation and experiment.

Detection and response characteristics of giant magnetostrictive/piezoelectric laminated cantilevers under cyclic bending

ABSTRACT We examine the detection and response characteristics of giant magnetostrictive/piezoelectric laminated cantilevers under cyclic bending in a combined numerical and experimental approach. The laminate is fabricated using thin Terfenol-D and PZT layers. Three-dimensional finite element analysis was conducted, and the dynamic electromagneto-mechanical fields in the two-layered magnetostrictive/piezoelectric laminate were predicted by introducing a second-order magnetoelastic constant of Terfenol-D. The tip deflection, induced voltage, and induced magnetic field were also measured, and experimental data were compared with numerical simulations to verify the model. The effects of load ratio and frequency on the dynamic electromagneto-mechanical fields were then discussed in detail. The finite element method is shown to be capable of estimating the dynamic electromagneto-mechanical fields in the giant magnetostrictive/piezoelectric laminated cantilevers, making it a useful tool for designing future electronic devices with self-sensing or energy harvesting capabilities.

Effect of Weight on the Resonant Tuning of Energy Harvesting Devices Using Giant Magnetostrictive Materials

This study deals with the numerical and experimental study of the effect of weight on the resonant tuning and energy harvesting characteristics of energy harvesting devices using giant magnetostrictive materials. The energy harvesting device is made in a cantilever shape using a thin Terfenol-D layer, stainless steel (SUS) layer and a movable proof mass, among other things. In this study, two types of movable proof mass were prepared, and the device was designed to adjust its own resonant frequency automatically to match external vibration frequency in real time. Three-dimensional finite element analysis (FEA) was performed, and the resonant frequency, tip displacement, and output voltage in the devices were predicted and measured, and the simulation and experiment results were compared. The effects of the weight of the proof mass on self-tuning ability and time-varying behavior were then considered in particular.

Characteristics of energy harvesting using BaTiO3/Cu laminates with changes in temperature

The energy harvesting characteristics of piezoelectric/copper (BaTiO3/Cu) laminates rising from sharp temperature changes were investigated both numerically and experimentally. First, a phase field simulation was performed to determine the temperature-dependent piezoelectric coefficient and permittivity values. Then, the output voltages of the BaTiO3/Cu laminates were calculated for variations from room temperature to either a cryogenic temperature (77 K) or a higher temperature (333 K) using a 3D finite element simulation with the properties calculated from the phase field simulation. Finally, the output voltages of the piezoelectric BaTiO3/Cu laminates were measured for the same temperature changes and were compared to the simulation results.

Effect of the Loading Rate on the Brittle Fracture of Terfenol-D Specimens in Magnetic Field: Strain Energy Density Approach

The aim of the present study is to characterize the fracture behavior of the giant magnetostrictive Terfenol-D alloy, both experimentally and numerically. Three-point bending tests have been carried out on single-edge precracked specimens, and fracture loads have been measured at different loading rates, in the presence or absence of a magnetic field. In recent years, it has been shown that the strain energy density (SED), averaged in a finite control volume, can successfully predict brittle failures of cracked, U- and V-notched specimens made of several materials. By performing coupled-field finite element analyses, the effects of the magnetic field and he loading rate on Terfenol-D failures have been analyzed, and the capability of SED criterion to capture these effects has been discussed. A relationship between the SED control volume size and the loading rate has been proposed, and failures have been quite accurately predicted in terms of the averaged SED.

Nonlinear bending response of Terfenol-D/PZT laminated devices under electromagnetic fields

This work presents the nonlinear bending response of magnetostrictive/piezoelectric laminated devices under electromagnetic fields both numerically and experimentally. The devices are fabricated using thin Terfenol-D and PZT layers. The magnetostriction of the Terfenol-D layer bonded to the PZT layer is measured, and a nonlinear finite element analysis is performed to evaluate the second-order magnetoelastic constants in Terfenol-D layer using measured data. The deflection, internal stresses and induced voltage/magnetic field for the laminated devices under magnetic/electric fields are then discussed in detail.

Effect of magnetic field on the bending response of magnetostrictive/piezoelectric laminated actuators

This work presents the nonlinear bending response of magnetostrictive/piezoelectric laminated actuators under magnetic fields both numerically and experimentally. The actuators are fabricated using thin Terfenol-D and PZT layers, and the magnetostriction of the actuators is measured. A nonlinear finite element analysis is also performed to evaluate the contribution of magnetic domain switching to the second-order magnetoelastic constants in Terfenol-D layer, and the effect of magnetic field on the deflection, internal stresses and induced voltage for the magnetostrictive/piezoelectric laminated actuators are discussed in detail.