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Acquirement of True Stress-strain Curve Using True Fracture Strain Obtained by Tensile Test and FE Analysis

인장시험과 유한요소해석으로 구한 파단 진변형률을 이용한 진응력-진변형률 선도 획득

  • 이경윤 (서강대학교 기계공학과 대학원) ;
  • 김태형 (한국원자력연구원) ;
  • 이형일 (서강대학교 기계공학과)
  • Published : 2009.10.01

Abstract

In this work, we predict a true fracture strain using load-displacement curves from tensile test and finite element analysis (FEA), and suggest a method for acquiring true stress-strain (SS) curves by predicted fracture strain. We first derived the true SS curve up to necking point from load-displacement curve. As the beginning, the posterior necking part of true SS curve is linearly extrapolated with the slope at necking point. The whole SS curve is then adopted for FE simulation of tensile test. The Bridgman factor or suitable plate correction factors are applied to pre and post FEA. In the load-true strain curve from FEA, the true fracture strain is determined as the matching point to test fracture load. The determined true strain is validated by comparing with test fracture strain. Finally, we complete the true SS curve by combining the prior necking part and linear part, the latter of which connects necking and predicted fracture points.

본 연구에서는 인장시험 및 유한요소해석으로 재료의 파단 진변형률을 구하고, 궁극적으로 재료의 진응력-진변형률을 얻는 방법을 제안했다. 먼저 인장시험으로 얻은 응력-변형률 선도를 네킹점에서 선형 외삽해, 초기 진응력-진변형률 곡선을 설정하고, 이를 유한요소해석에 채택했다. 유한요소해석 후 Bridgman 계수 및 평판 수정계수들을 사용해, 단축 상태의 하중-진변형률 선도를 얻어 파단진변형률을 실험-해석적으로 구했다. 이 예측 파단진변형률의 실험치 대비 오차는 3% 미만이다. 이렇게 구한 파단 진변형률과 이에 상응하는 파단진응력을 구해 파단점을 결정한다. 이어 네킹점과 결정한 파단점을 연결하는 네킹 후 진응력-진변형률 선형선도를 확보하고, 이를 네킹 전의 실험선도와 결합해 최종적으로 재료의 진응력-진변형률 선도를 완성했다. 본 연구에서 제시한 실험-해석적 진응력-진변형률 곡선 획득 방법은 SS400 평판시편과 같이 파단면적 측정이 어려운 경우, 그 유용함이 배가된다.

Keywords

References

  1. Mirone, G., 2004, 'A New Model for the Elastoplastic Characterization and the Stress-Strain Deformation on the Necking Section of a Tensile Specimen,' International Journal of Solids and Structures, Vol. 41, No.13, pp. 3545 - 3564 https://doi.org/10.1016/j.ijsolstr.2004.02.011
  2. Cabezas, E. E. and Celentano, D. J., 2004, 'Experimental and Numerical Analysis of the Tensile Test Using Sheet Specimens,' Finite Element in Analysis and Design, Vol. 40, No. 5-6, pp. 555-575 https://doi.org/10.1016/S0168-874X(03)00096-9
  3. Dumoulin, S., Tabourot, L., Chappuis, C., Vacher, P. and Arrieux, R., 2003, 'Determination of the Equivalent Stress-Equivalent Strain Relationship of a Copper Sample under Tensile Loading,' Journal of Materials Processing Technology, Vol. 133, No.1-2, pp. 79-83 https://doi.org/10.1016/S0924-0136(02)00247-9
  4. Gelin, J. C. and Ghouati, O., 1995, 'The Inverse Approach for the Determination of Constitutive Equations in Metal Forming,' CIRP Annals - Manufacturing Technology, Vol. 44, No. 1, pp. 189 - 192 https://doi.org/10.1016/S0007-8506(07)62304-X
  5. Huber, N. and Tsakmakis, C., 1999, 'Determination of Constitutive Properties form Spherical Indentation Data Using Neural Networks. Part 2: Plasticity with Nonlinear Isotropic and Kinematic Hardening,' Journal of the Mechanics and Physics of Solids, Vol. 47, No.7, pp. 1589-1607 https://doi.org/10.1016/S0022-5096(98)00110-0
  6. Lee, H., Lee, J. H. and Pharr, G. M., 2005, 'A Numerical Approach to Spherical Indentation Techniques for Material Property Evaluation,' Journal of the Mechanics and Physics of Solids, Vol. 53, No.9, pp. 2037-2069 https://doi.org/10.1016/j.jmps.2005.04.007
  7. Bressan, J. D. and Unfer, R. K., 2006, 'Construction and Validation Tests of a Torsion Test Machine,' Journal of Materials Processing Technology, Vol. 179, No. 1-3, pp. 23-29 https://doi.org/10.1016/j.jmatprotec.2006.03.099
  8. Rice, J. R. and Rosengren, G. F., 1968, 'Plane Strain Deformation Near a Crack tip in a Power-Law Hardening Material,' Journal of the Mechanics and Physics of Solids, Vol. 16, No.1, pp. 1-12 https://doi.org/10.1016/0022-5096(68)90013-6
  9. Hyun, H. C., Lee, J. H. and Lee, H., 2008, 'Mathematical Expression for Stress-Strain Curve of Metallic Material,' Transactions of the KSME A, Vol. 32, No. 1, pp. 21-28 https://doi.org/10.3795/KSME-A.2008.32.1.021
  10. Bridgman, P. W., 1952, Studies in Large Plastic Flow and Fracture, McGraw Hill Book Company Inc., New York
  11. Joun, M. S., Choi, I. S., Eom, J. G. and Lee, M. C., 2007, Finite Element Analysis of Tensile Testing with Emphasis on Necking,' Computational Materials Science, Vol. 41, No.1, pp. 63-69 https://doi.org/10.1016/j.commatsci.2007.03.002
  12. Joun, M. S., Eom, J. G. and Lee, M. C., 2008, 'A New Method for Acquiring True Stress-strain Curves over a Large Range of Strains Using a Tensile Test and Finite Element Method,' Mechanics of Materials, Vol. 40, No.7, pp. 586-593 https://doi.org/10.1016/j.mechmat.2007.11.006
  13. Lee, C. H. and Kobayashi, S., 1973, 'New Solutions to Rigid-plastic Deformation Problems Using a Matrix Method,' Transactions of the ASME, Vol. 95, pp. 865 - 873 https://doi.org/10.1115/1.3438238
  14. ABAQUS User's Manual, 2004, Version 6.5, Hibbitt, Karlsson and Sorensen, Inc., Pawtucket, RI
  15. Dowling, N. E., 2006, Mechanical Behavior of Materials, Third Edition, Prentice Hall, Inc

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