• Title, Summary, Keyword: 미끄럼선장

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Interfacial Crack-tip Constraints and J-integrals in Plastically Hardening Bimaterials under Full Yielding (완전소성하 변형경화 이종접합재의 계면균열선단 구속상태 및 J-적분)

  • Lee, Hyung-Yil;Kim, Yong-Bom
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.27 no.7
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    • pp.1159-1169
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    • 2003
  • This paper investigates the effects of T-stress and plastic hardening mismatch on the interfacial crack-tip stress field via finite element analyses. Plane strain elastic-plastic crack-tip fields are modeled with both MBL formulation and a full SEC specimen under pure bending. Modified Prandtl slip line fields illustrate the effects of T-stress on crack-tip constraint in homogeneous material. Compressive T-stress substantially reduces the interfacial crack-tip constraint, but increases the J-contribution by lower hardening material, J$\_$L/. For bimaterials with two elastic-plastic materials, increasing plastic hardening mismatch increases both crack-tip stress constraint in the lower hardening material and J$\_$L/. The fracture toughness for bimaterial joints would consequently be much lower than that of lower hardening homogeneous material. The implication of unbalanced J-integral in bimaterials is also discussed.

Formability of Sheet Metal in Noncircular Cup Drawing (ll) - for Arbitrary Cross Sections - (비원형단면에 대한 판재 성형성(II) - 임의단면에 대하여 -)

  • 김민수;신재현;서대교
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.12
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    • pp.3094-3104
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    • 1993
  • The five punch and die sets are selected as the examples of arbitrary cross sections which have two opposite inclined sides. Two kinds of blank shapes are designed for all cross sections. One(h-b1.) is determined by slip-line theory and the other (G-b1.) is determined conventionally as the similar shapes with the cross sections which were used by Gopinathan. As a result of the experimental procedures, the superiority of the blank shapes designed by slip-line theory is verified in the limiting drawing ratio, the uniformity of cup height and the thickness distributions.

A Study of Friction in Microfoming Using Ring Compression Tests and Finite Element Analysis (링 압축시험과 유한요소해석을 이용한 미세성형 공정에서의 마찰특성에 관한 연구)

  • Kim, Hong-Seok;Kim, Geung-Rok
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.34 no.10
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    • pp.1471-1478
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    • 2010
  • Microforming processes have recently attracted considerable attention from industry and academia since they enable the production of microscale parts using various materials at a high production rate, minimize material loss, and provide parts with excellent mechanical properties. However, for successful development and applications of the microforming process it is critical to take the tribological size effect into consideration because previous studies have shown that traditional friction models for macroscale forming generate significantly erroneous results in the case of microforming. In this paper, we performed scaled ring compression experiments to investigate the tribological size effect of aluminum and brass materials in microforming. The sensitivity of the interfacial friction to the deformation characteristics of the ring was quantitatively analyzed by the finite element analysis. In addition, a friction model based on slip line field and upper boundary techniques was used to theoretically explain the friction mechanism in microforming.

Formability of Sheet Metal in Noncircular Cup Drawing(I) (for Rectangular Cross Section) (비원형 단면에 대한 판재 성형성(I) (직사각형 단면에 대하여))

  • Shin, J.H.;Kim, M.S.;Seo, D.K.
    • Transactions of the Korean Society of Automotive Engineers
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    • v.2 no.1
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    • pp.84-95
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    • 1994
  • The effects of punch and blank shapes in the rectangular cup drawing process are examined experimentally to improve the formabilities. For this purpose, three blank shapes which are h-bl., G-bl., and T-bl., and five punch shape factors which are the ratios of two adjacent side lengths in rectangular cross section are adopted. The constructing methods of the three blank shapes are as follows. The h-bl. is designed by slip-line theory, and the G-bl. is selected for the similar shape to the punch. The T-bl. is obtained by the drawing method which is introduced in the technical references. The five punch shape factors are selected for length/width=1, 1.25, 1.5, 1.75 and 2. The experimental procedures are performed for all the above forming conditions to investigate and compare the formabilities. As a result, it is verified experimentally that the rectangular cups drawn by the h-bl. are more ideal than those drawn by G-bl. and T-bl.. They have not only higher limiting drawing ratio, more uniformity in drawn cup heights and more ideal thickness distributions, but also need relatively less maximum drawing forces.

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