Faculty Profiles - KATO Junji

Papers - KATO Junji

Division display 21 - 40 of about 92 ／ All the affair displays >>

Topology optimization for unsteady state thermal fluid problems

Takaara Keisuke, Hoshiba Hiroya, Takase Shinsuke, Nishiguchi Koji, Kato Junji

NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan Vol. 66 ( 0 ) page： 27 2022

Language：Japanese Publisher：National Committee for IUTAM

As regards thermal-fluid topology optimization research, only a few studies have considered the unsteady state thermal-fluid problem. In actual design problems, there are lots of cases in which temporal changes in temperature distribution are important rather than steady-state. In this study, the framework of a density-based topology optimization method for the unsteady thermal-fluid problem is proposed. The governing equations are unsteady-state incompressible Naiver-Stokes equation and thermal convection-diffusion equation, discretized with stabilized finite element method. The numerical analysis shows that the proposed framework captures the transient effect correctly and the results of optimization are physically reliable.

DOI： 10.11345/japannctam.66.0_27

CiNii Research

Coupled simulation of fluid and visco-hyperelastic solid with Eulerian finite volume method

Nishiguchi Koji, Takeuchi Shusuke, Shimada Tokimasa, Katsumata Ryohei, Hoshiba Hiroya, Kato Junji

NCTAM papers, National Congress of Theoretical and Applied Mechanics, Japan Vol. 66 ( 0 ) page： 15 2022

Language：Japanese Publisher：National Committee for IUTAM

Unified Eulerian structure-fluid formulation is suitable for massively parallel simulation of complex-shaped material. However, it has not been applied to the simulation of viscoelastic material, which has many internal variables in conventional studies. Numerical simulations of viscoelastic material are essential for a wide range of engineering fields, such as a shock-absorbing structure. Considering the background above, we propose a unified Eulerian structure-fluid formulation with a visco-hyperelastic model in this study. The proposed method is verified by simulating the uniaxial tension test and shock-absorbing structure.

DOI： 10.11345/japannctam.66.0_15

CiNii Research

Large-Scale Topology Optimization of Transient Incompressible Flow with Building-Cube Method

KATSUMATA Ryohei, NISHIGUCHI Koji, SHIMADA Tokimasa, HOSHIBA Hiroya, KATO Junji

The Proceedings of OPTIS Vol. 2022.14 ( 0 ) page： U00058 2022

Language：Japanese Publisher：The Japan Society of Mechanical Engineers

In recent years, topology optimization methods have been adopted not only for structural problems but also for fluid flow problems. Topology optimization for unsteady flows requires a fine mesh, which is computationally expensive. Therefore, we propose an transient incompressible flow topology optimization method based on the building cube method (BCM), which is suitable for massively parallel computing. BCM is a type of hierarchical Cartesian mesh method that has been reported to have very good scalability. The transient Navier-Stokes equations in the topology optimization procedure are solved by a finite volume discretization based on the BCM. The sensitivity of the objective function is obtained by continuous sensitivity analysis based on the adjoint variables method.

DOI： 10.1299/jsmeoptis.2022.14.u00058

CiNii Research

Multi-scale Topology Optimization Using FFT-based Homogenization with Elasto-plastic Material

MATSUI Masayoshi, HOSHIBA Hiroya, OGURA Hiroki, NISHIGUCHI Koji, KATO Junji

The Proceedings of OPTIS Vol. 2022.14 ( 0 ) page： U00052 2022

Language：Japanese Publisher：The Japan Society of Mechanical Engineers

Thanks to the development of additive manufacturing technology, it is becoming possible to produce materials with desired mechanical properties defined by their periodic microstructures. Multi-scale topology optimization has been paid attention to in many engineering fields to design optimal microstructures. However, its high computational cost prevents practical use, such as high-resolution 3D analysis for precision modeling and non-linear analysis assuming actual materials. In this study, to solve this problem, we focus on the homogenization approach using fast Fourier transform and develop a new optimization method with fast computing speed and low memory requirement. By performing sample analyses, we demonstrate the validity and efficiency of the proposed method.

DOI： 10.1299/jsmeoptis.2022.14.u00052

CiNii Research

Topology Optimization for Unsteady Coupled Thermal-Fluid Problems

TAKAARA Keisuke, HOSHIBA Hiroya, TAKASE Shinsuke, NISHIGUCHI Koji, KATO Junji

The Proceedings of OPTIS Vol. 2022.14 ( 0 ) page： U00045 2022

Language：Japanese Publisher：The Japan Society of Mechanical Engineers

As regards thermal-fluid topology optimization problems, many beneficial results have been reported. However, only a few studies have considered the unsteady state thermal-fluid problem. In actual design problems, there are lots of cases in which temporal changes in temperature distribution are important rather than steady-state. In this study, the framework of a density-based topology optimization method for the unsteady thermal-fluid problem is proposed. The governing equations are unsteady-state incompressible Naiver-Stokes equation and thermal convection-diffusion equation, discretized with stabilized finite element method. The design sensitivity is computed accurately based on the adjoint variable method. The numerical analysis shows that the proposed framework captures the transient effect correctly and the results of optimization are physically reliable.

DOI： 10.1299/jsmeoptis.2022.14.u00045

CiNii Research

A new constraint on principal stress direction variance to improve load bearing capacity

Kamada, H; Kato, J; Uozumi, H; Kikawa, K

STRUCTURAL AND MULTIDISCIPLINARY OPTIMIZATION Vol. 64 ( 5 ) page： 3209 - 3225 2021.11

Language：Japanese Publisher：Structural and Multidisciplinary Optimization

The present study addresses a simplified topology optimization method to improve load bearing capacity. Topology optimization taking account of structurally nonlinear and complex behavior is an important topic from the viewpoint of mechanics. However, most methodologies require complex analytical derivation of sensitivity analysis and high computational cost to obtain the optimal solution. In light of this, we propose a practical design method employing the principal direction of Cauchy stress and the directional statistics, to improve load bearing capacity indirectly with much lower computational cost than those based on complex nonlinear structural analysis. Finally, we discuss setting of optimization problems, and demonstrate the accuracy and performance of the proposed method with a series of numerical examples.

DOI： 10.1007/s00158-021-03079-8

Web of Science

Scopus

Robust topology optimization based on finite strain considering uncertain loading conditions

Nishino, T; Kato, J

INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING Vol. 122 ( 6 ) page： 1427 - 1455 2021.3

Language：Japanese Publisher：International Journal for Numerical Methods in Engineering

The present study proposes a method of robust topology optimization assuming uncertainties in the magnitude and direction of loads applied to a geometrically nonlinear structure. The objective function is the sum of the expected value and the standard deviation of end-compliance of a structure with a compressible Neo-Hookean hyperelasticity. In this study, quadratic approximation of the end-compliance with respect to random variables is employed to reduce computational cost. To ensure its accuracy, a complete analytical formulation is derived, and the performance and limitation of the proposed method are deeply discussed. The performance of the proposed method is verified and its numerical examples emphasize the importance of considering geometrical nonlinearity to obtain robust structures with respect to uncertainties of loading conditions. Finally, we have obtained a finding that the optimized network system consisting of thin members plays a significant role in the improvement of robustness of structures.

DOI： 10.1002/nme.6584

Web of Science

Scopus

Implicit Eulerian fluid-structure interaction method considering interfacial discontinuity of velocity field

NISHIGUCHI Koji, SHIMADA Tokimasa, HOSHIBA Hiroya, Kato Junji

The Proceedings of The Computational Mechanics Conference Vol. 2021.34 ( 0 ) page： 228 2021

Language：Japanese Publisher：The Japan Society of Mechanical Engineers

We propose an implicit Eulerian finite volume formulation using the reference map technique and Lagrangian maker particles to simulate deformable solid-fluid interaction problems. In this numerical framework, a set of Lagrangian maker particles represent the solid region and carry the initial position vector of solid (i.e., reference map), whereas basic equations and spatial derivatives are computed on the spatially fixed mesh. We will demonstrate several numerical examples in the presentation to validate the present approach.

DOI： 10.1299/jsmecmd.2021.34.228

CiNii Research

A new constraint of variance of principal stress direction for improving structural strength in Topology optimization Reviewed

KAMADA Hiroki, KATO Junji, KYOYA Takashi

Transactions of the Japan Society for Computational Engineering and Science Vol. 2020 ( 0 ) page： 20200006 - 20200006 2020.4

Language：Japanese Publisher：JAPAN SOCIETY FOR COMPUTATIONAL ENGINEERING AND SCIENCE

The present study proposes a simplified topology optimization method to improve structural strength. Topology optimization considering structurally nonlinear behavior is one of the important topics. However, most of those methodologies request the complicated analytical derivation of sensitivity analysis and also high computational costs to obtain the optimal solution. This is the reason why the optimal design method based on linear structural analysis is still common approach in practice. However, optimal layouts based on linear structural analysis may lose the structural stability under larger or uncertain load.From this background, we propose a method of practical and simplified topology optimization to improve structural buckling behavior with much lower computational costs than that of optimal design based on complicated nonlinear structural analysis. Finally, we discuss the setting of the optimization problem improving the structural strength and demonstrate the accuracy and performance of the proposed method by a series of numerical examples.

DOI： 10.11421/jsces.2020.20200006

CiNii Research

Finite thermo-elastic decoupled two-scale analysis Reviewed Open Access

Robert Fleischhauer,Tom Thomas, Junji Kato, Kenjiro Terada, Michael Kaliske

International Journal for Numerical Methods in Engineering Vol. 121 ( 3 ) page： 355 - 392 2020.2

数理的均質化法に基づく材料微視構造のトポロジー最適（特集：モルフォロジクス：形がつくる新しいセラミックスと機能）

加藤準治

日本セラミックス協会誌 ( 55 ) page： 377-382 2020

弾塑性挙動を考慮したトポロジー最適化における解析的感度導出法とその後の展開

加藤準治

計算工学 Vol. 25 ( 1 ) page： 3-7 2020

数理的均質化法に基づく材料微視構造のトポロジー最適

加藤準治

日本セラミックス協会誌 Vol. 55 page： 377 - 382 2020

Microscopic design and optimization of hydrodynamically lubricated dissipative interfaces Reviewed

B.A. Cakal, İ. Temizer, J. Kato, K. Terada

International Journal of Numerical Methods for Engineering Vol. 120 ( 2 ) page： 153 - 178 2019.10

Study on Optimal Design for Sandwich Beams Based on the Ground Structure Method Reviewed

KOIKE Yusuke, USHIJIMA Kuniharu, KATO Junji

Transactions of the Japan Society for Computational Engineering and Science Vol. 2019 ( 0 ) page： 20190006 - 20190006 2019.4

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：JAPAN SOCIETY FOR COMPUTATIONAL ENGINEERING AND SCIENCE

In this study, an optimal design of lattice sandwich panels based on the ground structure method has been investigated. In our calculation, the sandwich panels were assumed to be subjected to three-point bending load. The lattices discussed in this paper can be manufactured by using the selective laser metal melting machine. Based on the former experimental study on the manufacturable diameter of each strand, a new equation for controlling the cross-section of each strand was introduced, which is based on the multiphase material optimization approach. In this paper, three kinds of unit-cell models (BCC, f2BCC and half-BCC) were applied as an initial shape, and the effect of the micro-architecture on the optimized result was discussed. It is found that the lattice composed of f2BCC unit behaves the lowest compliance among three geometries. The optimized shape was manufactured with a good accuracy by SLM.

DOI： 10.11421/jsces.2019.20190006

CiNii Research

Topology optimization with geometrical nonlinearity considering uncertain loading condition Reviewed

NISHINO Takayuki, KATO Junji, KYOYA Takashi

Transactions of the Japan Society for Computational Engineering and Science Vol. 2019 ( 0 ) page： 20190004 - 20190004 2019.4

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：JAPAN SOCIETY FOR COMPUTATIONAL ENGINEERING AND SCIENCE

The present study proposes a topology optimization method considering finite deformation for loading uncertainty. The loading angle is assumed to be uncertain as a condition. The objective is to minimize expectation and standard deviation of end-compliance obtained by means of a Total Lagrangian finite element formulation. In this case, an analytical estimation of the expectation and the standard deviation is not allowed. In order to solve this problem, we approximate the end-compliance by a Taylor series expansion and derive the mathematical formulation. In this approach, the second derivative of the objective function is necessary to keep the accuracy in sensitivity. This phenomenon is investigated in terms of numerical validations. Finally, some numerical examples demonstrate the usefulness of the proposed method.

DOI： 10.11421/jsces.2019.20190004

CiNii Research

STRESS-CONSTRAINED TOPOLOGY OPTIMIZATION OF INFILL STRUCTURE

KAMADA Hiroki, HOSHIBA Hiroya, KATO Junji, KYOYA Takashi

Journal of Japan Society of Civil Engineers, Ser. A2 (Applied Mechanics (AM)) Vol. 75 ( 1 ) page： 68 - 85 2019

Language：Japanese Publisher：Japan Society of Civil Engineers

Recent development of Additive Manufacturing technology made it possible to manufacture the complex-shaped porous structures: this leads to further development and research for porous structures with special functions and characteristics. In particular, the so-called infill structure is paid attention for its high strength and robustness, and also the optimal design methods for infill structures have been reported. However, few studies has examined to extend to the practical design with stress constraint. With this reason, the present study addresses a topology optimization method for infill structures to avoid stress concentration by adding the local volume constraint and p-norm type stress constraint concept. In addition, we propose a new method, namely variable influence radius, to solve a specific problem which arises in infill optimization. Finally we discuss the setting of optimization problem and demonstrate the accuracy and performance of the proposed method by a series of numerical examples.

DOI： 10.2208/jscejam.75.68

CiNii Research

OPTIMAL DESIGN OF LATTICE STRUCTURE CONSIDERING CONSTRAINTS THROUGH ADDITIVE MANUFACTURING PROCESS

Koike, Y; Ushijima, K; Kato, J

SECOND INTERNATIONAL CONFERENCE ON SIMULATION FOR ADDITIVE MANUFACTURING (SIM-AM 2019) page： 205 - 214 2019

Optimal design of lattice structure considering constraints through additive manufacturing process Open Access

Koike Y., Ushijima K., Kato J.

2nd International Conference on Simulation for Additive Manufacturing, Sim-AM 2019 page： 205 - 214 2019

Publisher：2nd International Conference on Simulation for Additive Manufacturing, Sim-AM 2019

In this research, an optimization design of the lattice structure is investigated, which is based on the ground structure method. In recent years, as a result of rapid development of additional manufacturing technology, it has become possible to manufacture complicated shapes including periodic lattice structure. However, in real metal lattice samples, geometric imperfections may exist in every unit because of the stochastic influence of feasible processing path. In this study, a new ground structure method which does not leave elements with small cross sectional area was proposed. In particular, the effect of geometric constraints caused by additive manufacturing techniques on optimized results are discussed based on the robust topology optimization combining perturbation methods for quantifying uncertainty. In the end, a robust topology optimization was also discussed as a problem to minimize expected value and standard deviation of compliance.

Open Access

Scopus

Multi-scale topology optimization considering elastoplastic composite material Reviewed

Hoshiba Hiroya, OGAWA Shun, KATO Junji, KYOYA Takashi

Transactions of the Japan Society for Computational Engineering and Science Vol. 2018 ( 0 ) page： 20180015 - 20180015 2018.11

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：JAPAN SOCIETY FOR COMPUTATIONAL ENGINEERING AND SCIENCE

The present study proposes topology optimization of microstructure considering elastoplastic deformation based on a decoupling multi-scale analysis. Energy absorption capacity of macrostructure is maximized under a prescribed material volume of microstructure. It is assumed that microstructure consists of a two-phase material based on elastoplastic von Mises model and that macrostructure is modeled with anisotropic Hill’s elastoplasticity. In this study, we extend the analytical sensitivity method used for mono-scale analysis to the decoupling multi-scale analysis and propose a framework of new multi-scale topology optimization, which can reduce the computational costs with keeping sensitivities highly accurate. It is verified by a series of numerical examples that the proposed method provides reliable optimization results and has a great potential for advanced material design.

DOI： 10.11421/jsces.2018.20180015

CiNii Research

Other Link： https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-16J02523/

　 PREV - NEXT 　

<KATO Junji>

Papers - KATO Junji