Hiroyuki Kuramae

Multiscale finite element simulations of piezoelectric materials based on two- and three-dimensional electron backscatter diffraction–measured microstructures

This article presents a computational procedure for evaluating effective homogenized material properties of polycrystalline piezoelectric materials and constructing two- and three-dimensional realistic microstructure models based on electron backscatter diffraction crystal orientation measurement. Microstructural features of a polycrystalline piezoelectric material, barium titanate, were investigated through electron backscatter diffraction measurements using an amorphous osmium coating to prevent charging. Realistic crystal orientations obtained from the electron backscatter diffraction measurements were introduced into multiscale finite element simulations based on homogenization theory to reveal the relationship between the macrostructure and the microstructure. First, a two-dimensional microstructural model was constructed, and the effect of the sampling area of the electron backscatter diffraction–measured crystal orientations was analyzed. We discuss the representative volume element determined from two points of view: the macroscopic homogenized material properties and the microscopic localized material behavior in response to external loads. Second, the surface of specimen was ground and polished at regular intervals and was measured by electron backscatter diffraction iteratively. Then a three-dimensional microstructural model was constructed by stacking in-plane crystal orientations in series along the out-of-plane direction, and the influence of the microstructural thickness, which indicates the stacking dimension in the out-of-plane direction, was investigated. We compare the macrostructural homogenized material properties between the two- and three-dimensional microstructures.

A multiscale finite element simulation of piezoelectric materials using realistic crystal morphology

This paper presents the full components of macroscopic homogenized material properties and the microscopic localized response obtained through a multiscale finite element simulation using realistic crystal morphology. Crystal morphology analysis was performed to reveal microstructure and texture of a polycrystalline piezoelectric material. The insulative specimen of piezoelectric material was coated with a conductive layer of amorphous osmium to remove an electric charge, and crystal orientations were measured by means of electron backscatter diffraction. Then the obtained crystal orientations were applied to a multiscale finite element simulation based on homogenization theory.

Multi-scale finite element analyses for stress and strain evaluations of braid fibril artificial blood vessel and smooth muscle cell

In this study, we developed a multi-scale finite element (FE) analysis code to obtain the stress and strain that occurred in the smooth muscle cell (SMC) at micro-scale, which was seeded in the real fabricated braid fibril artificial blood vessel. This FE code can predict the dynamic response of stress under the blood pressure loading. We try to establish a computer-aided engineering (CAE)-driven scaffold design technique for the blood vessel regeneration. Until now, there occurred the great progresses for the endothelial cell activation and intima layer regeneration in the blood vessel regeneration study. However, there remains the difficulty of the SMC activation and media layer regeneration. Therefore, many researchers are now studying to elucidate the fundamental mechanism of SMC activation and media layer regeneration by using the biomechanical technique. As the numerical tool, we used the dynamic-explicit FE code PAM-CRASH, ESI Ltd. For the material models, the nonlinear viscoelastic constitutive law was adapted for the human blood vessel, SMC and the extra-cellular matrix, and the elastic law for the polyglycolic acid (PGA) fiber. Through macro-FE and micro-FE analyses of fabricated braid fibril tubes by using PGA fiber under the combined conditions of the orientation angle and the pitch of fiber, we searched an appropriate structure for the stress stimulation for SMC functionalization. Objectives of this study are indicated as follows: 1. to analyze the stress and strain of the human blood vessel and SMC, and 2. to calculate stress and strain of the real fabricated braid fibril artificial blood vessel and SMC to search an appropriate PGA fiber structure under combined conditions of PGA fiber numbers, 12 and 24, and the helical orientation angles of fiber, 15, 30, 45, 60, and 75 degrees. Finally, we found a braid fibril tube, which has an angle of 15 degree and 12 PGA fibers, as a most appropriate artificial blood vessel for SMC functionalization.

Electron Backscatter Diffraction Crystal Morphology Analysis And Multiscale Simulation Of Piezoelectric Materials

A computational approach based on electron backscatter diffraction (EBSD) measurement was proposed to estimate the effects of crystal morphology on the overall response of polycrystalline piezoelectric ceramics. EBSD-measured crystal orientations of a polycrystalline piezoelectric ceramic, barium titanate, were applied to a multiscale fi nite element simulation based on asymptotic homogenization theory. First, the orientation dependence of material properties, such as elastic compliance constants, dielectric and piezoelectric strain constants, was discussed for a single-domain crystal of tetragonal perovskite structure. The computation indicated that piezoelectric strain constants are more sensitive to crystal orientation compared with other properties. Then the single-crystalline material properties were introduced into multidirectionally oriented grains in the polycrystalline microstructure, the multiscale fi nite element analysis between macrostructure and EBSD-measured microstructure was performed. In this paper emphasis was placed on the diminution of microstructure. The authors discussed about the adverse effect on each component of macrostructural homogenized material properties, which is useful for micromechanics approaches.

Deep Drawing Formability Analysis of AZ31 Mg-Alloy

Light and highly resistant, magnesium has been more and more included into alloys composition, especially in automotive and electronic devices. Usual automotive applications for magnesium alloys are gearbox, cylinder head covers and other types of covers, when electronic industry uses this alloys for mobile computers and mobile phones frames (chassis). However casting is still the first production process for magnesium application, press forming is considered as having significant potential. Yet, influences of many key parameters are not clearly known. In this report, sheets of AZ31 magnesium alloy were submit to deep drawing tests to investigate the influence of temperature, lubricant, blank holding pressure and speed. As a result, an appropriate lubricant was selected out of a set of potentially interesting lubricants selected with respect to their announced properties. Deep drawing tests also enlighten the poor formability of AZ31 even at 160°C and an apparent optimum formability temperature at 200°C. Other tests and controls, like thickness profile, were also performed to complete knowledge of AZ31 properties.

Parallel iterative partitioned coupling procedure for multi-scale piezoelectric finite element analysis

This paper presents parallel multi-scale piezoelectric finite element (FE) analyses of piezoelectric ceramics by using the scanning electron microscope (SEM) and the electron backscatter diffraction (EBSD) measured crystal morphology model based on the crystallographic homogenization method. Since coefficient matrix of FE equation for the electromechanical coupling problem is not positive definite and strongly ill-condition, a parallel iterative partitioned coupling procedure based on the block Gauss-Seidel (BGS) method with the conjugate gradient (CG) solver is applied to the multi-scale analysis. 3-dimensional micro polycrystal morphology of a barium titanate ceramic is measured by using the SEM-EBSD apparatus and introduced to the parallel multi-scale analysis. We investigate on micro FE modeling with crystal orientation distribution and convergences of both the BGS method and the CG solver.

Development of Multi‐Scale Finite Element Analysis Codes for High Formability Sheet Metal Generation

In this study, the dynamic‐ and static‐explicit multi‐scale finite element (F.E.) codes are developed by employing the homogenization method, the crystalplasticity constitutive equation and SEM‐EBSD measurement based polycrystal model. These can predict the crystal morphological change and the hardening evolution at the micro level, and the macroscopic plastic anisotropy evolution. These codes are applied to analyze the asymmetrical rolling process, which is introduced to control the crystal texture of the sheet metal for generating a high formability sheet metal. These codes can predict the yield surface and the sheet formability by analyzing the strain path dependent yield, the simple sheet forming process, such as the limit dome height test and the cylindrical deep drawing problems. It shows that the shear dominant rolling process, such as the asymmetric rolling, generates “high formability” textures and eventually the high formability sheet. The texture evolution and the high formability of the newly ...

Parallel Computing of Multi‐scale Finite Element Sheet Forming Analyses Based on Crystallographic Homogenization Method

Since the multi-scale finite element analysis (FEA) requires large computation time, development of the parallel computing technique for the multi-scale analysis is inevitable. A parallel elastic/crystalline viscoplastic FEA code based on a crystallographic homogenization method has been developed using PC cluster. The homogenization scheme is introduced to compute macro-continuum plastic deformations and material properties by considering a poly- crystal texture. Since the dynamic explicit method is applied to this method, the analysis using micro crystal structures computes the homogenized stresses in parallel based on domain partitioning of macro-continuum without solving simultaneous linear equations. The micro-structure is defined by the Scanning Electron Microscope (SEM) and the Electron Back Scan Diffraction (EBSD) measurement based crystal orientations. In order to improve parallel performance of elastoplasticity analysis, which dynamically and partially increases computational costs during the analysis, a dynamic workload balancing technique is introduced to the parallel analysis. The technique, which is an automatic task distribution method, is realized by adaptation of subdomain size for macro-continuum to maintain the computational load balancing among cluster nodes. The analysis code is applied to estimate the polycrystalline sheet metal formability.

PERFORMANCE ENHANCEMENT OF A VALVELESS PUMP DRIVEN BY A NOBLE PIEZOELECTRIC COMPOSITE ACTUATOR

This paper presents a computational and experimental study of a valveless pump driven by a noble piezoelectric composite actuator consisting of a bimorph piezoelectric plate and a metal cap. The superiority of deformation performance of the proposed composite actuator was demonstrated computationally through fi nite element simulation and was then verifi ed experimentally by defl ection measurements of a disc-shaped prototype under an alternating electric fi eld. The proposed composite actuator was applied to a valveless pump in a Y-shaped fl uid channel. The pump’s performance was estimated using a piezoelectric-fl uid interaction fi nite element simulation. The effect of the fl uid channel confi guration was investigated, and the liquid feed volume is discussed and compared with that of conventional actuators.

Scanning removal of ion-implanted novolak resist by using a laser irradiation

Novolak resists which are implanted with B, P, and As ions, respectively, were irradiated with a pulsed 532nm laser. Regardless of the implanted ion species and density, more than 74 % of the laser power was found to absorb into the Si wafer surface. For the laser irradiation of 1 pulse, the ion-implanted resist with a density of 5.0x1013 atoms/cm2 was completely stripped in the same way as that of a non-implanted resist. The optical absorption of the resist surface increased as the density of the ion-implantation increased. In case of the ion-implanted resist with a density of 5.0x1015 atoms/cm2, the resist was stripped by 20 pulses irradiation without occurring laser-induced surface damage. A scanning removal of the highly ion-implanted resist was also successfully stripped by using an optimized irradiation condition. A highly ion-implanted resist was continuously stripped by the scanning laser irradiation with 20 pulses.