This paper deals with a control problem of a thermal stress in a composite circular disk consisting of a structural layer onto which multiple piezoceramic layers with concentrically arranged electrodes are bonded. When a heating temperature distribution acts on the bottom surface of the structural layer, the maximum thermal stress in the structural layer is minimized by applying appropriate voltages to the electrodes. The stepwise voltage applied to each electrode is obtained by solving a linear programming problem when constrains are imposed on stresses in the piezoceramic layers. In order to decrease design variables such as the layer thicknesses and the number and dimensions of electrodes, an efficient method for the optimum design is developed. The structure of the composite disk as well as the electrode arrangement on each piezoceramic layer has been optimally designed so that performance of the stress control is maximized. Finally, it is seen from numerical results that the maximum thermal stress in the structure layer is reduced by 38.3% which is 4.6% higher than that obtained in the previous paper.

抄録全体を表示

To investigate the effect of liquid water saturation on the efficiency of polymer electrolyte fuel cells, it is important to determine the exact relationship between the liquid water saturation profile and other parameters. In this paper, the pore size distribution (PSD) is used to calculate the liquid water saturation in a fuel cell. Using the PSD, liquid water saturation is calculated from experimental data for the capillary pressure on a porous media. Numerical analysis is used to analyze and evaluate the liquid water pressure and temperature profiles in a fuel cell. This paper uses two-phase, three-dimensional analysis to determine the effects of using the PSD.

抄録全体を表示

Many attempts were made in the past to investigate numerically the metal-hydrogen interactions at macro-scale but the actual microstructure was generally not introduced into the analyses. The objective of this work is to simulate, on an artificial polycrystal, the effect of the microstructure-induced stress-strain field heterogeneity on the internal hydrogen evolution. Finite element method is used to take into account explicitly the grain morphologies and their crystalline orientations into the description of the mechanical deformation. A one-way coupled crystal plasticity-transient hydrogen diffusion analysis is developed and applied to solve the boundary value problem. The analysis of the computed hydrogen content field shows that a segregation of hydrogen is observed mainly at the grain boundaries. It is also shown that grain size has a significant effect not only on the amount of hydrogen segregated at the grain boundaries but also on the relative size of concentration gradients.

抄録全体を表示

Numerical solutions for large scale models face the problem of poor convergence and for non-stationary problems the situation becomes worse. To speed up the convergence, an algorithm to perform the Balancing Domain Decomposition (BDD) preconditioning for non-stationary incompressible flow problems is constructed. The problem caused by the presence of nonlinear convection term in the non-stationary Navier-Stokes equations, which complicates the solving of the equations numerically, is solved by a characteristic-curve method. The method is advantageous as it renders the matrix for linear equations symmetric, thus enabling the Conjugate Gradient (CG) method to be used to solve the interface problem of the Domain Decomposition Method (DDM). The related algorithms are all implemented in parallel by the Hierarchical Domain Decomposition Method (HDDM) and the program has the capability of solving non-stationary problems with up to 10 million degrees of freedom (DOF). The BDD algorithm together with characteristic-curve method is applied to a benchmark problem, a three-dimensional driven cavity flow model, and the results are compared with available solutions.

抄録全体を表示

With the rapid growth of the WAN infrastructures and enhancement of MPI libraries for WAN environment, Grid computing is expected to be a practical methodology for performing very large finite element analyses. In particular, the utilization of Grid enhanced MPI libraries allows one to execute legacy programs on WAN environments, which is very attractive for finite element application users. However, the high communication cost associated with WANs has discouraged its use as a parallel environment for finite element analysis. In this study, we focus on the utilization of Grid environments, in particular on cluster-of-clusters environments for the execution of FEA, and propose a hierarchical communication pattern to reduce the communication cost. By analytically estimating the communication cost, based on the decomposed FE mesh, we assess the effectiveness of the hierarchical communication pattern. We then show the obtained communication cost reduction by numerical experiments performed on cluster-of-clusters on WAN.

抄録全体を表示