Takayuki Masunaga

Stabilization and smoothing of pressure in MPS method by Quasi-Compressibility

In this paper, a method to stabilize simulations and suppress the pressure oscillation in Moving Particle Semi-implicit method for an incompressible fluid is presented. To make the pressure smooth in terms of both of space and time, a new representation of the incompressible condition is proposed. The incompressible condition consists of two parts: the Divergence-Free condition and the Particle Number Density condition. The Divergence-Free condition has the effect of making the pressure smooth in terms of both space and time. The Particle Number Density condition is necessary to keep the fluid volume constant. In this work, the Quasi-Compressibility is also introduced for stabilization. A dam break is simulated more stably and the space distribution and the time variation of pressure are evaluated more smoothly than the traditional method. Moreover, surface particles are detected more accurately. Nevertheless the proposed method is computationally cheaper. Some simulations such as a Fluid-Structure Interaction are supposed to be more accurate using this method.

A high power-handling RF MEMS tunable capacitor using quadruple series capacitor structure

This paper presents an RF MEMS tunable capacitor that achieves an excellent power-handling property with relatively low actuation voltage. The tunable capacitor consists of two fixed MIM (Metal-Insulator-Metal) capacitors and two MEMS capacitor elements, all connected in series. This quadruple series capacitor (QSC) structure enables reduction of the actuation voltage without sacrificing the power-handling capability, since the MIM capacitor reduces the RF voltage amplitude applied to the MEMS capacitors. The measured result demonstrates +36dBm hot-switching at 85°C with 21V pull-in voltage.

Accurate extraction of the mechanical properties of thin films by nanoindentation for the design of reliable MEMS

Traditional procedures for the extraction of mechanical properties of thin films by nanoindentation measurements have shown problems in terms of accuracy and in the ability to support sophisticated constitutive models. In this paper, an inverse modeling procedure based on finite element analysis is presented to solve these limitations. Finite element simulation is used to predict the relationships between the indentation load and depth. The developed approach is applied to extract the viscoplastic properties of aluminum single grain, the viscoelastic properties of acrylic resin films, and the residual strain in stainless steel.

Multiscale simulation of aluminum thin films for the design of highly-reliable MEMS devices

Abstract A multiscale simulation methodology is presented to predict the macroscopic mechanical properties of aluminum thin films with a columnar grain structure from the morphology at microscopic scale. The elasto–plastic characteristics of the thin films are calculated as a function of the grain size, temperature, and strain rate by taking into account creep phenomena. The simulated data are validated by experimental stress–strain curves measured by dedicated microstructures in conjunction with a nanoindentation test equipment.