Material Models for Accurate Simulation of Sheet Metal Forming and Springback

Fusahito YOSHIDA 한국소성가공학회 2010 기타자료 Vol.2010 No.6

For anisotropic sheet metals, modeling of anisotropy and the Bauschinger effect is discussed in the framework of Yoshida-Uemori kinematic hardening model incorporating with anisotropic yield functions. The performances of the models in predicting yield loci, cyclic stress-strain responses on several types of steel and aluminum sheets are demonstrated by comparing the numerical simulation results with the corresponding experimental observations. From some examples of FE simulation of sheet metal forming and springback, it is concluded that modeling of both the anisotropy and the Bauschinger effect is essential for the accurate numerical simulation.

Reduction of Springback of Sheet Metals by Bottoming

Takayuki Ogawa,Atsushi Hirahara,Fusahito Yoshida 한국소성가공학회 2010 기타자료 Vol.2010 No.6

The effect of bottoming on the reduction of springback is investigated by performing V-air-bending experiment on a high strength steel sheet of TS590MPa and the corresponding FE simulation. From the experiment, it was found that the springback is drastically decreased with increasing bottoming force. This is mainly due to the reduction of bending moment by compressive load acting normally to the sheet. At an early stage of bottoming, springback is also influenced by the change of geometrical rigidity of the bent sheet due to the straightening of ridge line warp. Since bottoming is a process of reverse deformation of tension-compression, the Bauschinger effect of materials should be taken into account for its accurate numerical simulation. 3D FE simulation using Yoshida-Uemori kinematic hardening model predicts well the bottoming effect.

Elasto-Plasticity Behavior of Type 5000 and 6000 Aluminum Alloy Sheets and Its Constitutive Modeling

Shohei TAMURA,Satoshi SUMIKAWA,Hiroshi HAMASAKI,Takeshi UEMORI,Fusahito YOSHIDA 한국소성가공학회 2010 기타자료 Vol.2010 No.6

To examine the deformation characteristic of type 5000 and 6000 aluminum alloy sheets, uniaxial tension, biaxial stretching and in-plane cyclic tension-compression experiments were performed, and from these, r-values (r?, r45 and r90), yield loci and cyclic stress-strain responses were obtained. For the accurate description of anisotropies of the materials, high-ordered anisotropic yield functions, such as Gotoh’s biquadratic yield function and Barlat’s Yld2000-2d, are necessary. Furthermore, for the simulation of cyclic behavior, an advanced kinematic hardening model, such as Yoshida-Uemori model (Y-U model), should be employed. The effect of the selection of material models on the accuracy of the springback prediction was discussed by performing hat bending FE simulation using several yield functions and two types of hardening laws (the isotropic hardening model and Y-U model)

MAGNETIC PROPERTIES OF FePt₃ ORDERED ALLOY

H.Yoshida,H.Fujimorl,T.Kaneko,S.Abe,K.Watanabe,M.Matsumoto,T.Yoshida,T.Kanomata 한국자기학회 1995 韓國磁氣學會誌 Vol.5 No.5

The magnetic properties for Fe₂₄Pt_(76) and Fe_(26)Pt_(74) have been investigated. The temperature vs. magnetic susceptibility curve for Fe₂₄Pt_(76) had no peak near the Neel temperature. The magnetization process at 4.2 K showed only a linear variation up to the high magnetic field of 240 kOe. That for Fe_(26)Pt_(74) at 77 K showed a metamagnetic transition at 100 kOe. These properties were discussed on the basis of a band picture.

Incremental Parsing in Conditionals and Relative Clauses in Korean

Masaya Yoshida,윤수원,신정아 한국생성문법학회 2022 생성문법연구 Vol.32 No.4

The strong head-finality of Korean raises many potential challenges to incremental parsing. In languages like Korean, there is normally no indication of clause structure before the parser encounters the verb or the relative head at the end of the clause. This uncertainty of clause structure can potentially give rise to processing difficulty of verbs in head-final languages. Developing our earlier studies in Japanese (Yoshida 2006), we present four series of experiments in Korean (offline and online) to show that there are, however, cases where the processing of clause-final verbs can indeed be predicted and facilitated.

Interrogative Feature Checking in Japanese and Korean

( Keiko Yoshida ),( Tomoyuki Yoshida ) 한국언어정보학회 1996 국제 워크샵 Vol.1996 No.-

This paper discusses the feature checking mechanism of interrogative sentences in Japanese and Korean. We first focus on a phenomenon of omitting question markers in informal speech in Japanese and attempt to provide an account for it within the framework of Principles and Parameters approach. We argue that question markers can be omitted only if interrogative features of the sentence can be properly checked. In particular we claim that I-to-C head-movement is one of the options for interrogative feature checking in Japanese as well as languages without question markers. A close examination of Korean reveals certain differences between Korean and Japanese. Some theoretical consequences from this analysis are also discussed.

Primary Study on Providing a Basic System for Uterine Cervical Screening in a Developing Country: Analysis of Acceptability of Self-sampling in Lao PDR

Yoshida, Tomomi,Nishijima, Yoshimi,Hando, Kiyomi,Vilayvong, Soulideth,Arounlangsy, Petsamone,Fukuda, Toshio Asian Pacific Journal of Cancer Prevention 2013 Asian Pacific journal of cancer prevention Vol.14 No.5

Background: Most developing countries have been unable to implement well-organized health care systems, especially comprehensive Pap smear screening-based programs. One of the reasons for this is regional differences in medical services, and a low-cost portable cervical screening system is necessary. To improve regional discrepancies in cervical screening systems, we investigated the usefulness and acceptability of cervical selfsampling by liquid-based cytology (LBC) for 290 volunteers in the Lao PDR. Materials and Methods: Following health education with comprehensive documents, cervical self-sampling kits by LBC were distributed in three provincial, district, and village areas to a total of 290 volunteers, who were asked to take cytology samples by themselves. Subsequently, the acceptability of self-sampling was evaluated using a questionnaire. Results: The documents were well understood in all three regions. Regarding the acceptability of self-sampling, the selections for subsequent screening were 62% self-sampling, 36% gynecologist-sampling, 1% either method, and 1% other methods. The acceptability rates were higher in the district and the village than in the province. For the relationship between acceptability and pregnancy, the self-sampling selection rate was higher in the pregnancy-experienced group (75%) than in the pregnancy-inexperienced group (60%). For the relationship between selection of self-sampling and experience of screening, the self-sampling selection rate was higher in the screening-inexperienced group (62%) than in the screening-experienced group (52%). Conclusions: Our data show that this new way forward, involving a combination of self-sampling and LBC, is highly acceptable regardless of age, educational background, and residence in rural areas in a developing country.

A Brief Overview of a Scale Independent Deformation Theory and Application to Diagnosis of Deformational Status of Solid-State Materials

Yoshida, Sanichiro The Korean Society for Nondestructive Testing 2012 한국비파괴검사학회지 Vol.32 No.2

A field theoretical approach to deformation and fracture of solid-state material is outlined, and its application to diagnosis of deformational status of metal specimens is discussed. Being based on a fundamental physical principle known as local symmetry, this approach is intrinsically scale independent, and capable of describing all stages of deformation on the same theoretical foundation. This capability enables us to derive criteria that can be used to diagnose transitions from the elastic to plastic regime, and the plastic to fracturing regime. For practical applications of these criteria, an optical interferometric technique known as electronic speckle-pattern interferometry is proved to be quite powerful; it is able to visualize the criteria as a whole image of the object on a real-time basis without numerical processing. It is demonstrated that this method is able to reveal loading hysteresis as well.

Resolution of Time and Worker Conflicts for a Single Project in a Max-Plus Linear Representation

Yoshida, Shotaro,Takahashi, Hirotaka,Goto, Hiroyuki Korean Institute of Industrial Engineers 2011 Industrial Engineeering & Management Systems Vol.10 No.4

This research develops a framework for resolving time and worker conflicts in the Critical Chain Project Management (CCPM) method, expressed in the form of a Max-Plus Linear (MPL) system. Our previous work proposed a method for resolving time conflicts. However, in practical cases, both time and worker conflicts may occur. Hence, we propose a method for resolving both time and worker conflicts for a single project. We first consider how to detect a resource conflict. Then, we define an adjacency matrix to resolve the detected conflicts. Using the proposed method, we confirm that the resource conflict can be resolved through a numerical example.

Field Measurement and Modal Identification of Various Structures for Structural Health Monitoring

Yoshida, Akihiko,Tamura, Yukio Council on Tall Building and Urban Habitat Korea 2015 International journal of high-rise buildings Vol.4 No.1

Field measurements of various structures have been conducted for many purposes. Measurement data obtained by field measurement is very useful to determine vibration characteristics including dynamic characteristics such as the damping ratio, natural frequency, and mode shape of a structure. In addition, results of field measurements and modal identification can be used for modal updating of FEM analysis, for checking the efficiency of damping devices and so on. This paper shows some examples of field measurements and modal identification for structural health monitoring. As the first example, changes of dynamic characteristics of a 15-story office building in four construction stages from the foundation stage to completion are described. The dynamic characteristics of each construction stage were modeled as accurately as possible by FEM, and the stiffness of the main structural frame was evaluated and the FEM results were compared with measurements performed on non-load-bearing elements. Simple FEM modal updating was also applied. As the next example, full-scale measurements were also carried out on a high-rise chimney, and the efficiency of the tuned mass damper was investigated by using two kinds of modal identification techniques. Good correspondence was shown with vibration characteristics obtained by the 2DOF-RD technique and the Frequency Domain Decomposition method. As the last example, the wind-induced response using RTK-GPS and the feasibility of hybrid use of FEM analysis and RTK-GPS for confirming the integrity of structures during strong typhoons were shown. The member stresses obtained by hybrid use of FEM analysis and RTK-GPS were close to the member stresses measured by strain gauges.