Tadashi Horibe

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.

Computational simulation of vibration displacement on piezoelectric quartz crystal using finite element method

Recently, piezoelectric quartz crystals have found wide applications as chemical and biosensors. The quartz crystal microbalance (QCM) is a well-known technique for mass sensing using the mass-loading transduction property for frequency shift. The behavior of the vibration displacement of the electrode surface on the QCM for various applied voltages is an important problem for understanding the physical property of the QCM, but it is very difficult to detect the displacement. In this paper, the effects of resonant frequency of the QCM caused by the variation of the applied voltage are studied by using finite element method (FEM) software.

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.

Development of Plastic Collapse Assessment Procedure for Cylindrical Vessels With a Local Thin Area Near a Nozzle Under Internal Pressure

There are numerous cases where a local thin area has found near a nozzle attachment in cylindrical pressure vessels. Since the stress concentration due to a nozzle hole under internal pressure significantly affect to the stress state of the vessel near the nozzle, it must be taken into account in its plastic collapse assessment. In this paper, a new plastic collapse assessment procedure for cylindrical vessels with a local thin area near a nozzle attachment under internal pressure was proposed. This proposal utilizes the existing reference stresses to estimate the plastic collapse load under three-axial condition derived in accordance with the Tresca theory. The distribution of stress concentrations in vessel wall due to a nozzle attachment depends on its reinforcement condition for the nozzle hole, so the stress state should be computed by linear FEA in advance. The stress concentration factors are provided with normalizing of generated stresses in vessels near a nozzle attachment for the similar type of dimensions, orientations and projections of the nozzle attachment by the computed stresses with already-proposed equations for no reinforcement conditions.The plastic collapse loads predicted by the proposed reference stress are ascertained with the results of experiments and non-linear FEA.Copyright

J-Resistance Properties of Cr-Mo Steels With Internal Hydrogen Measured by Means of Potential Drop Method

The tearing resistance dJ/da of three kinds of 2.25Cr-1Mo steels and 2.25Cr-1Mo-0.3V steel with internal hydrogen was measured using the potential drop method. Internal hydrogen refers to test specimens that are precharged (thermally charged) prior to testing. In general, Cr-Mo steels used widely in the refining and petrochemical industry are susceptible to temper embrittlement. However, there are very few studies concerning the effects of hydrogen and temper embrittlement on J-resistance properties. The test specimens were prepared by subjecting them to normalizing, tempering and post-weld heat treatments which simulated actual conditions. Some specimens were embrittled by step cooling (Socal-1 treatment). Hydrogen substantially reduces the dJ/da of the steels other than the V-bearing steel and temper embrittlement additionally causes adverse effects on the dJ/da of the steels with internal hydrogen where the temper embrittlement parameter J-factor is larger than around 300.Copyright