• Title/Summary/Keyword: Kim-Tuan hardening equation

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New Stress-Strain Model for Identifying Plastic Deformation Behavior of Sheet Materials (판재의 소성변형 거동을 동정하기 위한 새로운 응력-변형률 모델)

  • Kim, Young Suk;Pham, Quoc Tuan;Kim, Chan Il
    • Journal of the Korean Society for Precision Engineering
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    • v.34 no.4
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    • pp.273-279
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    • 2017
  • In sheet metal forming numerical analysis, the strain hardening equation has a significant effect on calculation results, especially in the field of spring-back. This study introduces the Kim-Tuan strain hardening model. This model represents sheet material behavior over the entire strain hardening range. The proposed model is compared to other well known strain hardening models using a series of uniaxial tensile tests. These tests are performed to determine the stress-strain relationship for Al6016-T4, DP980, and CP Ti sheets. In addition, the Kim-Tuan model is used to integrate the CP Ti sheet strain hardening equation in ABAQUS analysis to predict spring-back amount in a bending test. These tests highlight the improved accuracy of the proposed equation in the numerical field. Bending tests to evaluate prediction accuracy are also performed and compared with numerical analysis results.

Evaluation of plastic flow curve of pure titanium sheet using hydraulic bulge test (유압벌지실험을 이용한 순 티탄늄 판재의 소성유동곡선 평가(제2보))

  • Kim, Young-Suk;Kim, Jin-Jae
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.17 no.4
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    • pp.718-725
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    • 2016
  • In this study, the plastic flow curve of commercially pure titanium sheet (CP Ti) actively used in the plate heat exchanger etc., was evaluated. The plastic flow curve known as hardening curve is a key factor needed in conducting finite element analyses (FEA) for the forming process of a sheet material. A hydraulic bulge test was performed on the CP Ti sheet and the strain in this test was measured using the DIC method and ARAMIS system. The measured true stress-true strain curve from the hydraulic bulge test (HBT) was compared with that from the tensile test. The measured true stress-true strain curve from the hydraulic bulge test showed stable plastic flow curve over the strain range of 0.7 which cannot be obtained in the case of the uniaxial tensile test. The measured true stress-true strain curve from the hydraulic bulge test can be fitted well by the hardening equation known as the Kim-Tuan model.

Evaluation of press formability of pure titanium sheet (순 티탄늄 판재의 프레스 성형성 평가(제 1보))

  • Kim, Young-Suk;In, Jeong-Hun
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.17 no.3
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    • pp.380-388
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    • 2016
  • Commercially pure titanium (CP Ti) has been actively used in plate heat exchangers due to its light weight, high specific strength, and excellent corrosion resistance. However, compared with automotive steels and aluminum alloys, there has not been much research on the plastic deformation characteristics and press formability of CP Ti sheet. In this study, the mechanical properties of CP Ti sheet are clarified in relation to press formability, including anisotropic properties and the stress-strain relation. The flow curve of the true stress-true strain relation is fitted well by the Kim-Tuan hardening equation rather than the Voce and Swift models. The forming limit curve (FLC) of CP Ti sheet was experimentally evaluated as a criterion for press formability by punch stretching tests. Analytical predictions were also made via Hora's modified maximum force criterion. The predicted FLC with the Kim-Tuan hardening model and an appropriate yield function shows good correlation with the experimental results of the punch stretching test.