13th International Conference on Fracture June 16–21, 2013, Beijing, China -10- (1) Molecular dynamics simulations under a special configuration have been performed to study the mechanism of Fe3C-Fe interface under Mode I loading condition at different temperatures, and the FS-EAM potential used in LAMMPS is certified by melting point verification. (2) The elastic modulus and maximum stress as a function of the simulated temperature for both with and without crack models, and the maximum values of modulus and maximum stress for no crack model at roomtemperature are seen to be 332.67GPa, 12.17GPa, 86.94GPa and 6.04GPa for crack model. The traction-separation relation of X70 pipeline steel with crack is characterized by MD simulations, the peak traction value of 13.15GPa for tensile model at room temperature. (3) The parameterized cohesive traction-separation relation for Mode I failure at room temperature to simulate the crack propagation behavior of X70 pipeline steel in a FEA. The curve obtained through our simulation is agreement with predictions from linear elastic fracture mechanics, showing the expected linear relationship between loading-pin displacement and reaction force. (4) The fracture toughness gained from our simulations is close to the experimental result. It shows our methodology is feasible. Our study may provide several novel ideas for simulating complex fracture problems based cohesive laws used in FE analysis. Acknowledgements Project supported by the Fundamental Research Funds for the Central Universities (Grant No. 2010SCU21014) and the Project of West-East Gas Pipeline Company at PetroChina Company Limited (Grant No. XQSGL01423). References [1] Yu. Ivanisenko, I. MacLaren, X. Sauvage, R.Z. Valiev,. H.J. Fecht, Shear-induced transformation in nanoscale Fe–C composite. Acta Mater., 54 (2006) 1659–1669. [2] C.R. Dandekar, Y.C. Shin, Molecular dynamics based cohesive zone law for describing Al-SiC interface mechanics. Composites: Part A, 42 (2011) 355–363. [3] V.Yamakova, E. Saether, D.R. Phillipsc, E.H. Glaessgen, Molecular-dynamics simulation-based cohesive zone representation of intergranular fracture processes in aluminum. Journal of the Mechanics and Physics of Solids, 54 (2006) 1899–1928. [4] D.S. Dugdale, Yielding of steel sheets containing slits. J. Mech. Phys. Solids, 8 (1960) 100–104. [5] G.I. Barrenblatt, The mathematical theory of equilibrium of cracks in brittle fracture. Adv. Appl. Mech., 7 (1962) 55–129. [6] X.P. Xu, A. Needleman, Numerical simulations of fast crack growth in brittle solids. J. Mech. Phys. Solids, 42 (1994) 1397–1434. [7] X.W. Zeng, S.F. Li, A multiscale cohesive zone model and simulations of fractures. Comput. Methods Appl. Mech. Engrg., 199 (2010) 547–556. [8] X.W. Zhou, J.A. Zimmerman, E.D. Reedy, N.R. Moody, Molecular dynamics simulation based cohesive surface representation of mixed mode fracture. Mechanics of Materials, 40 (2008) 832–845. [9] X.W. Zhou, N.R. Moody, R.E. Jonesa, J.A. Zimmermana, E.D. Reedyc, Molecular-dynamics-based cohesive zone law for brittle interfacial fracture under mixed loading conditions: Effects of elastic constant mismatch. Acta Materialia, 57 (2009) 4671–4686. [10] Y.J. Wei, L. Anand, Grain-boundary sliding and separation in polycrystalline metals:application to nanocrystalline fcc metals. J Mech Phys Solids, 52 (2004) 2587–616. [11] J.T. Lloyd, J.A. Zimmerman, R.E. Jones, X.W. Zhou, D.L. McDowell, Finite element analysis of an atomistically derived cohesive model for brittle fracture. Modelling Simul. Mater. Sci. Eng., 19 (2011) 065007. [12] M.W. Finnis，J.E. Sinclair, A simple empirical N-body potential for transition metals. Phil.
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