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Journal Articles

Experimental and analytical studies on the effect of excessive loading on fatigue crack propagation in piping materials

Yamaguchi, Yoshihito; Katsuyama, Jinya; Onizawa, Kunio; Li, Y.*; Yagawa, Genki*

Journal of Pressure Vessel Technology, 135(4), p.041406_1 - 041406_9, 2013/08

 Times Cited Count:7 Percentile:62.1(Engineering, Mechanical)

Since the seismic regulatory guide was revised and the Niigata-ken Chuetsu-oki earthquake occurred, attention is being drawn to the evaluation of the effects of large scale earthquakes for piping systems in which cracks may potentially occur. In this work, crack growth behaviors after excessive loading were experimentally and analytically evaluated for carbon steel and austenitic stainless steel. Increase and decrease pattern of load amplitude and maximum load of cyclic loading were applied to fatigue crack growth test. According to these results, retardation effect of crack growth was confirmed after excessive loading. In addition, applicability to the retardation effect of the modified Wheeler model was elucidated. We confirmed the retardation effect hardly influence the failure probability based on seismic loading by the probabilistic fracture mechanics (PFM) analyses with the Wheeler model.

Journal Articles

Experimental and analytical studies on the effect of excessive loading on fatigue crack propagation in piping materials

Yamaguchi, Yoshihito; Katsuyama, Jinya; Onizawa, Kunio; Sugino, Hideharu*; Li, Y.*; Yagawa, Genki*

Proceedings of 2009 ASME Pressure Vessels and Piping Division Conference (PVP 2009) (CD-ROM), 9 Pages, 2009/07

Niigata-ken Chuetsu-oki earthquake was actually happened, whose magnitude was beyond the assumed one provided in seismic design, in July 2007. Through these events, it is becoming the focus of attention to evaluate an effect of large scale earthquake while the SCC and/or fatigue-crack are assumed to piping. Many previous papers have been already published about the retardation effect on fatigue crack growth by excessive loading. The retardation effect is treated qualitatively relating to plastic strain generated by excessive loading. In this work, the crack growth after the excessive loading is evaluated for carbon steel and austenitic stainless steel. Some cyclic excessive loading patterns such as stepwise increase or decrease were applied to fatigue-crack-growth experiments. The FEM analyses were conducted to evaluate the plastic region size during such loading conditions. The PFM analyses were conducted to evaluate the retardation of crack growth influence the probability of failure.

Journal Articles

Application and accuracy of basis functions implemented in a patch-by-patch approximation of mixed-type finite element

Matsubara, Hitoshi; Yagawa, Genki

Oyo Rikigaku Rombunshu, 10, p.201 - 209, 2007/08

The present paper discusses the accuracy of patch-by-patch approximation of mixed-type finite element scheme. In the approximation, not only a displacement field for each element but also stress and strain fields for each patch are defined. In order to determine unknown parameters of stress/strain fields of a patch, the Hu-Washizu principle is employed. In this paper, the accuracy of the generalized finite element functions implemented in the proposed approximation is shown. Furthermore, to show the effectiveness of the approximation in the fracture mechanics that have singular stress fields, the approximation is applied to linear fracture problem.

Journal Articles

Non-matching mesh gluing by meshless interpolation; An Alternative to Lagrange multipliers

Tian, R.; Yagawa, Genki

International Journal for Numerical Methods in Engineering, 71(4), p.473 - 503, 2007/07

 Times Cited Count:15 Percentile:28.27(Engineering, Multidisciplinary)

Rewards of using non-matching meshes are great in many aspects: sub-meshing a complex structure in a sub-structure-wise manner separately; selective local refinement; unlimited scalability guarantee for generating meshes, etc. However, when meshes do not match, a gluing algorithm is required to enforce inter-domain continuity. The non-matching mesh issue is avoidable or does not exist in a node-based or meshless discretization in meshless methods. Motivated by this, a gluing algorithm is developed based on meshless interpolation. The gluing is accomplished by continuous trial and test functions across non-matching meshes constructed using nodes only. Compared with Lagrange multiplier gluing - one of the most common approaches - the current algorithm has two significant benefits: (1) easier implementation in any dimension and (2) positive definite banded system matrices, not acting against equation solvers, and hence better suited for large-scale finite element analysis.

Journal Articles

An Adaptive control system using the fuzzy theory for transient multi-physics numerical simulations

Muramatsu, Toshiharu; Yagawa, Genki*

International Journal for Numerical Methods in Fluids, 54(6-8), p.805 - 830, 2007/07

 Times Cited Count:0 Percentile:100(Computer Science, Interdisciplinary Applications)

An adaptive control system to yield optimum time step sizes was developed using the fuzzy theory for transient multi-physics numerical simulations. Applications of the control system reveals considerable amount of the computing time savings, typically by 50 % to 75 % of the computing time required when the time step size was not controlled by the system. The result obtained in this work is very encouraging in the sense that the adaptive control system would be used as one of the efficient measures for saving computing time when one wishes to perform extremely large-scale computations in transient multi-physics numerical simulations.

Journal Articles

Allman's triangle, rotational DOF and partition of unity

Tian, R.; Yagawa, Genki

International Journal for Numerical Methods in Engineering, 69(4), p.837 - 858, 2007/01

 Times Cited Count:17 Percentile:25.45(Engineering, Multidisciplinary)

A simplification of the 1984 Allman triangle is presented. It is found that this old element takes a typical form of the partition of unity approximation. The Allman's rotation presented in the partition of unity form offers merits and convenience in formulation and practical applications. The stiffness matrix of the 1984 Allman triangle, which is originally computed from the linear strain triangular element, can be obtained instead in a cheaper way from that of the constant strain triangular element. The constraint of the rotational terms during essential boundary treatment, which remains equivocal and ambiguous, is understood to be mandatory. The partition of unity notion enables a straightforward extension of the Allman's rotational dof to meshfree approximations.

Journal Articles

Advanced 4-node tetrahedrons

Tian, R.; Matsubara, Hitoshi; Yagawa, Genki

International Journal for Numerical Methods in Engineering, 68(12), p.1209 - 1231, 2006/12

 Times Cited Count:29 Percentile:17.7(Engineering, Multidisciplinary)

Tetrahedral elements are indispensable to complex finite element structural analysis. Two existing and two newly developed advanced 4-node tetrahedrons are studied in this paper. The existing elements that use complicated displacement fields are significantly simplified. The spurious zero-energy modes typical of all these elements are identified to be rigid-body-alike modes and are found to be naturally suppressible, making it possible to avoid any stabilization techniques and unknown parameters in formulation. Through the simplified form, we connect these four tetrahedrons and view them in a general framework of the partition-of-unity-based approximation. This general view allows us to reveal many promising features of the newly developed tetrahedrons by comparing them with their existing counterparts: the newly developed tetrahedrons have straightforward formulation.

Journal Articles

Numerical investigation into the linear dependence problem of partition of unity based generalized finite element methods

Tian, R.; Nakajima, Norihiro; Yagawa, Genki

Keisan Kogaku Koenkai Rombunshu, 10(1), p.393 - 396, 2005/05

A known problem of partition of unity-based generalized finite element methods (referred to as GFEM) is the linear dependence problem, which leads to singular global (stiffness) matrices. Thus far, attempts to eliminate the linear dependence problem have been unsuccessful. Numerical experiments are carried out among several GFEMs to investigate the problem. Based on the numerical experiments, simple but effective approaches to eliminating the linear dependence problem are suggested.

Journal Articles

Nodal arrangements for boundary treatment in EFGM

Tian, R.; Nakajima, Norihiro; Yagawa, Genki

Keisan Kogaku Koenkai Rombunshu, 10(1), p.397 - 400, 2005/05

An attempt is made to treat boundary conditions in EFGM through only nodal arrangements. One of major merits of the proposed nodal arrangement scheme is its straightforwardness in implementation. The accuracy of this nodal arrangement boundary treatment and its influence on convergence are assessed by comparing with the Lagrange multiplier and penalty methods using one- and two- dimensional problems. The nodal arrangement scheme shows a same performance as the Lagrange multiplier and penalty methods in the one-dimensional tests, but it evidently outperforms the penalty method in the two-dimensional tests.

Journal Articles

Towards to realize a quake-proof information control and management system for nuclear power plant

Nakajima, Norihiro; Kimura, Hideo; Higuchi, Kenji; Aoyagi, Tetsuo; Suzuki, Yoshio; Hirayama, Toshio; Yagawa, Genki

Dai-23-Kai Nippon Shimyureshon Gakkai Taikai Happyo Rombunshu, p.117 - 120, 2004/06

The pablic acceptance of nuclear power plants operations requests information of status for the safety and ease. Previous technology in computational scinece is generarlly carried out the analysis as an uniform structure, although the plants are assembled by thousand of parts. The proposed approach is to develope assembled structural analysis and fluid/heat analyis in assembled structures under the natural and actual environmnet such as daily operation, small quakeing which does not induce shut down procedure, and so on.

Journal Articles

Seismic simulations for performance based monitoring of frame structures

Atanasiu, G. M.*; Hazama, Osamu; Guo, Z.; Yagawa, Genki*

Proceedings of 2nd International Conference Lifetime Oriented Design Concepts (ICLODC 2004), p.449 - 458, 2004/03

Some strategies in monitoring the structural seismic performance for a class of RC multistory buildings using linear and nonlinear dynamic analysis. New concepts and visions, considering the seismic input models based on probabilistic hazard level, will be presented. Numerical simulations of RC structures with different topologies are carried out as case studies, to search for a suitable strategy of seismic monitoring based on structural performance. For comparison, equivalent single degree of freedom models are also taken into account. The seismic input is based on the 1994 Northridge earthquake acceleration time histories. For comparison, the unscaled Kobe ground motion were also considered as input.

Journal Articles

Recent Japanese PFM researches related to failure probability of aged RPV

Shibata, Katsuyuki; Kanto, Yasuhiro*; Yoshimura, Shinobu*; Yagawa, Genki*

Proceedings of 5th International Workshop on the Integrity of Nuclear Components, p.99 - 117, 2004/00

no abstracts in English

Journal Articles

Application of ITBL basic software for virtual organizations

Higuchi, Kenji; Otani, Takayuki; Hasegawa, Yukihiro*; Suzuki, Yoshio; Yamagishi, Nobuhiro*; Kimura, Kazuyuki*; Maesako, Hiroshi*; Fukuda, Masahiro; Yagawa, Genki

Keisan Kogaku Koenkai Rombunshu, 8(2), p.797 - 800, 2003/05

no abstracts in English

Journal Articles

Grid computing supporting system on ITBL project

Higuchi, Kenji; Imamura, Toshiyuki*; Suzuki, Yoshio; Shimizu, Futoshi; Machida, Masahiko; Otani, Takayuki; Hasegawa, Yukihiro*; Yamagishi, Nobuhiro*; Kimura, Kazuyuki*; Aoyagi, Tetsuo; et al.

Lecture Notes in Computer Science 2858, p.245 - 257, 2003/00

Prototype of the middleware for Grid project promoted by national institutes in Japan has been developed. Key technologies that are indispensable for construction of virtual organization were already implemented onto the prototype of middleware and examined in practical computer/network system from a view point of availability. In addition several kinds of scientific applications are being executed on the prototype system. It seems that successful result in the implementation of those technologies such as security infrastructure, component programming and collaborative visualization in practical computer/network systems means significant progress in Science Grid in Japan.

Journal Articles

Development of a virtual research environment in ITBL project

Higuchi, Kenji; Otani, Takayuki; Hasegawa, Yukihiro*; Suzuki, Yoshio; Yamagishi, Nobuhiro*; Kimura, Kazuyuki*; Aoyagi, Tetsuo; Nakajima, Norihiro; Fukuda, Masahiro; Imamura, Toshiyuki*; et al.

Proceedings of International Conference on Supercomputing in Nuclear Applications (SNA 2003) (CD-ROM), 11 Pages, 2003/00

An experimental application of Grid computing was executed in ITBL project promoted by six member institutes of MEXT. Key technologies that are indispensable for construction of virtual organization were implemented onto ITBL Middleware and examined in the experiment from a view point of availability. It seems that successful result in the implementation and examination of those technologies such as security infrastructure, component programming and collaborative visualization in practical computer/network systems means significant progress in Science Grid in Japan.

Journal Articles

The Contribution of computational science & engineering

Yagawa, Genki

Enerugi Rebyu, 22(1), p.52 - 53, 2002/01

no abstracts in English

JAEA Reports

Automated identification of material constants in complex constitutive equations by an evolutionary algorithm and massively parallel processors

Kawasaki, Nobuchika; Felix, S.; Kasahara, Naoto; Furukawa, Tomonori*; Komura, Shinobu*; Yagawa, Genki*

PNC-TY9602 97-001, 26 Pages, 1997/04

PNC-TY9602-97-001.pdf:0.52MB

None

Journal Articles

Probabilistic fracture mechanics analyses of nuclear pressure vessels under PTS events

Yagawa, Genki*; Yoshimura, Shinobu*; *; Hirano, Masashi

Nucl. Eng. Des., 174(1), p.91 - 100, 1997/00

 Times Cited Count:9 Percentile:38.58(Nuclear Science & Technology)

no abstracts in English

JAEA Reports

Investigation on structgural analysis computer program of spent nuclear fuel shipping cask,II

Yagawa, Genki*;

JAERI-M 87-165, 168 Pages, 1987/10

JAERI-M-87-165.pdf:4.04MB

no abstracts in English

JAEA Reports

Investigation on structural analysis computer program of spent nuclear fuel shipping cask

Yagawa, Genki*;

JAERI-M 87-156, 312 Pages, 1987/10

JAERI-M-87-156.pdf:6.95MB

no abstracts in English

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