Abstract
An elastic-plastic finite element method (FEM) was used to calculate the stress and strain distributions ahead of notches with various root radii in a bending specimen of C-Mn steel with grain sizes of 10 and 30 μm. By accurately measuring the distance of the cleavage initiation site from the root of the notch, the local cleavage stress σ *ƒ was measured. When the notch radius increased from 0.25 to 1.0 mm, the distribution of high stress had a definite variation but the σ *ƒ remained relatively constant. In notch specimens with different root radii, the critical fracture event is identical,i.e., propagation of a ferrite grain-sized crack into the neighboring matrix. Therefore, the σ *ƒ is mainly determined by the length of the critical microcrack, here, the size of ferrite grain instead of the high stress volume for finding an eligible brittle particle. The critical strain for initiating a crack was about 1 pct. The cleavage site ahead of a notch was related to the relative distributions of stress and strain and the random distribution of the weakest grains. The higher fracture load of the fine-grain material can be attributed to its higher value of σ *ƒ /σo as compared with the coarse-grain. The σ *ƒ /σo is a potential engineering parameter for toughness assessment in notch specimens.
Similar content being viewed by others
References
J. Malkin and A.S. Tetelman:Eng. Fract. Mech, 1971, vol. 3, p. 131.
R.O. Ritchie, J.F. Knott, and J.R. Rice:J. Mech. Phys. Solids, 1973, vol. 21, p. 395.
J.G.D. Groom and J.F. Knott:Met. Sci., 1975, vol. 9, p. 330.
Robert O. Ritchie, Benjamin Francis, and William L. Server:Metall. Trans. A, 1976, vol. 7A, p. 831–38.
R.O. Ritchie and R.M. Horn:Metall. Trans. A, 1978, vol. 9A, p. 331.
R.O. Ritchie, W.L. Server, and R.A. Wullaert:Metall. Trans. A, 1979, vol. 10A, p. 1557–70.
D.A. Curry:Met. Sci., 1980, vol. 14, p. 319.
R.O. Ritchie and A.W. Thompson:Metall. Trans. A, 1985, vol. 16A, p. 233–48.
P. Bowen, S.G. Druce, and J.F. Knott:Acta Metall., 1986, vol. 34, p. 1121.
F.R.L. Kavishe and T.J. Baker:Mater. Sci. Technol., 1986, vol. 2, p. 583.
T. Lin, A.G. Evans, and R.O. Ritchie:Acta Metall., 1986, vol. 34, p. 2205.
J.J. Lewandowski and A.W. Thompson:Acta Metall., 1987, vol. 35, p. 1453.
T. Miyata, R.C. Yang, A. Otsuka, T. Haze, and S. Aihara:Proc. 7th Int. Conf. on Fracture, Houston, TX, 1989, Pergamon Press, Oxford, p. 2563.
J.H. Chen, H. Ma, and G.Z. Wang:Metall. Trans. A, 1990, vol. 21A, p. 313–20.
J.H. Chen, L. Zhu, and H. Ma:Acta Metall., 1990, vol. 38, p. 2527.
T. Miyata, T. Tagawa, A. Otsuka, K. Okamoto, and S. Aihara:Proc. 6th Int. Conf. on Mechanical Behaviour of Materials, Kyoto, Japan, 1991, Pergamon Press, Oxford, p. 183.
R. Hill:Mathematical Theory of Plasticity, Oxford, London, 1950.
J.F. Knott:J. Iron Steel Inst., 1968, vol. 204, p. 104.
T.R. Wilshaw, C.A. Rau, and A.S. Tetelman:Eng. Fract. Mech., 1968, vol. 1, p. 191.
J.R. Griffith and D.R.J. Owen:J. Mech. Phys. Solids, 1971, vol. 19, p. 419.
P. Bowen and J.F. Knott:Metall. Trans., 1986, vol. 17A, p. 231–41.
A.S. Tetelman, T.R. Wilshaw, and C.A. Rau:Int. J. Fract., 1971, vol. 4, p. 147.
A. Pineau:Proc. ICF5, Cannes, France, 1981, Pergamon Press, Oxford, p. 553.
F.M. Beremin:Metall. Trans. A, 1983, vol. 14A, p. 2277–87.
T. Lin, A.G. Evans, and R.O. Ritchie:Metall. Trans. A, 1987, vol. 18A, p. 641–51.
J.H. Chen and C. Yan:Mater. Sci. Technol., 1988, vol. 4, p. 732.
J.H. Chen, G.Z. Wang, and H. Ma:Metall. Trans. A, 1990, vol. 21A, p. 321–30.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Yan, C., Chen, J.H., Sun, J. et al. Critical assessment of the local cleavage stress σ *ƒ in notch specimens of C-Mn steel. Metall Trans A 24, 1381–1389 (1993). https://doi.org/10.1007/BF02668206
Received:
Published:
Issue Date:
DOI: https://doi.org/10.1007/BF02668206