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Nishi-Tokyo-shi, Japan

Ichinose N.,JSOL Corporation | Ishikawa M.,Yamagata University | Morimoto K.,Sekisui Seikei Ltd.
Polymer Composites | Year: 2011

Thanks to their lightweight properties, formability and low cost, polymers have become an essential material for manufactured products. To improve the mechanical properties, almost all polymers are blended with some kind of fiber made from glass, carbon, organic or natural material. The importance of interfacial strength between matrix and fiber is a well known requirement for effective mechanical properties and some experimental results indicate that low interfacial strength helps increase the toughness of composites. In this paper, models of composite reinforced by fiber aligned with maximum principal stress under uni-tensile loading are simulated. Based on the simulation result, we discuss the effect of interfacial strength, aspect ratio of fiber and friction force between matrix and fiber on stable deformation and provide the guidelines for establishing composites with high modulus and toughness. © 2011 Society of Plastics Engineers. Source

Takahashi Y.,JSOL Corporation | Tachi T.,University of Tokyo
Journal of the International Association for Shell and Spatial Structures | Year: 2015

In this paper, we propose a method to design a double-curved surface that is self-organized through the buckling of a thin material due to a controlled pattern of in-plane strain. We assume that the in-plane strain of a thin material is isotropic. Therefore, the intrinsic deformation is described by the distribution of the scalar value of a local scale factor, which can be obtained by calculating a conformal map from the initial state to the given 3D state. The construction of the pattern is as follows. We calculate the conformal map from the given shape to the original sheet. The map is calculated as the equilibrium state of a mass-spring (angular and length) model with defined rest angles and lengths to discretize a conformal map. We obtain the scale-factor distribution pattern from the conformal map. Using this pattern, we simulate the buckling deformation process and observe its behavior. We note additional geometric conditions needed to make the generated shape approximate the given 3D shape. © Copyright 2015 by Yusuke Takahashi and Tomohiro Tachi. Source

Ma N.,Osaka University | Ma N.,JSOL Corporation
International Journal of Advanced Manufacturing Technology | Year: 2016

To simulate welding induced transient thermal stress and deformation of large scale FE models, an accelerated explicit method (ACEXP) and graphical processing units (GPU) parallel computing program of the finite element method (FEM) were developed. In the accelerated explicit method, a two-stage computation scheme is employed. The first computation stage is based on a dynamic explicit method considering the characteristics of the welding mechanical process by controlling both the temperature increment and time scaling parameter. In the second computation stage, a static equilibrium computation scheme is implemented after dynamic thermal loading to obtain a static solution of transient thermal stress and welding deformation. It has been demonstrated that the developed GPU parallel computing program has a good scalability for large-scale models of more than 20 million degrees of freedom. The validity of the accelerated explicit method is verified by comparing the transient thermal stress and deformation with those computed by an implicit FEM. Finally, welding deformation and residual stress in a structure model assembled from nine high-strength steel plates and 26 weld lines were efficiently analyzed by ACEXP and GPU parallel computing within 45 h. The computed welding deformation agreed well with measured results, and a good accuracy was obtained. © 2016 Springer-Verlag London Source

Background and objective: The origin of frequency dependence of respiratory resistance has been explained by ventilation inhomogeneity; however, it is unclear which components in the respiratory system generate the frequency dependence. The author constructed a 4D pulmonary lobule model and analysed relationships between airflow rate, pressure and airway resistance by the use of computational fluid dynamics. Methods: The lobule model contained bifurcated bronchioles with two adjacent acini in which deformable inter-acinar septa and alveolar duct walls were designed. Constrictive conditions of respective bronchioles were designed, too. 4D finite element models for computational fluid dynamics were generated and airflow simulations were performed under moving boundary conditions of the arbitrary Lagrangean-Eulerean method. From the simulation results, airway resistances for various conditions were calculated. Results: Tissue resistance emerged under the condition of different acinar pressures caused by unequal airway resistances. If the inter-acinar septum was shifted so as to cancel the pressure difference, the acinar pressures were equal in spite of unequal airway resistances, and hence, tissue resistances did not emerge. Therefore, the tissue resistance in the former case is thought to be an index of alveolar pressure inequality (which could be cancelled by mechanical interaction of lung parenchyma), rather than a material property of the tissue itself. Conclusions: Inequality of alveolar pressure decreases as the input oscillatory frequency increases. Therefore, frequency dependence of the respiratory resistance should be regarded as a conditional index of the alveolar pressure inequality caused by heterogeneous changes in the intra-pulmonary airway and/or the lung parenchyma. © 2011 The Author Respirology © 2011 Asian Pacific Society of Respirology. Source

A simulation apparatus is provided with means for obtaining shape data expressing a simulation object, means for storing a constraint condition for a simulation in association with each type of object, means for storing, for each of one or more evaluation items for evaluating an object having an arbitrary shape satisfying the constraint condition, a procedure of a coupled analysis using one or more simulation means related to the evaluation item, means for accepting a type and an evaluation item for an object, means for reading out a procedure of a coupled analysis corresponding to the evaluation item based on the accepted evaluation item for the object, and means for reading out a constraint condition for an object corresponding to the accepted type and giving the constraint condition to the shape data to execute the coupled analysis in accordance with the procedure of the coupled analysis.

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