The intent of this paper is to propose an engineering approach to estimate the stress intensity factor of a micro crack emerging from an inclusion in relation with the morphology of the inclusion and its relative stiffness with the matrix. A micromechanical model, based on the FEA (finite element analysis) of the behavior of cracks initiated at micro structural features such as inclusions, has been developed using LEFM (Linear Elastic Fracture Mechanics) to predict the stress intensity factor of a micro crack emerging from an inclusion. Morphology of inclusions has important connotations in the development of the analysis. Stress intensity factor has been estimated from the FEA model for different crack geometries. Metallographic analysis of inclusions has been carried out to evaluate the typical inclusion geometry. It also suggests that micro cracks less than 1？μm behave differently than larger cracks.
References
[1]
Knott, J.F. (1973) Fundamentals of Fracture Mechanics. Butterworth, London.
[2]
Peterson, R.E. (1974) Stress Concentration Factors. John Wiley & Sons.
[3]
Rice, J.R. (1968) Fracture, an Advance Treatise. Academic Press.
[4]
Venkatasubramanian, T.V. and Baker, T.J. (1982) Role of Elongated MnS Inclusions in Hydrogen Embrittlement of High-Strength Steel. Metal Science, 16.
https://doi.org/10.1179/030634582790427154
[5]
Dahlberg, M. (1997) Micromechanical Modeling of Nodular Cast Iron, a Composite Material. International Journal of Cast Metals Research, 9, 319-330.
https://doi.org/10.1080/13640461.1997.11819673
[6]
Bank-Sills, L. and Bortman, Y. (1984) Reappraisal of the Quarter-Point Quadrilateral Element in Linear Elastic Fracture Mechanics. International Journal of Fracture, 25, 169-180. https://doi.org/10.1007/BF01140835
[7]
Brezhnitskii, L.T. (1966) Propagation of a Crack Terminating at the Edge of a Curvilinear Hole in a Plate. Soviet Materials Science, 2, 16-23.
https://doi.org/10.1007/BF00715159
[8]
Tweed, J. and Rooke, D.P. (1973) The Distribution of Stress near the Tip of a Radial Crack at the Edge of a Circular Hole. International Journal of Engineering Sciences, 11, 1185-1195. https://doi.org/10.1016/0020-7225(73)90084-0
[9]
Tada, I., Paris, P.C. and Irwin, G.R. (1973) The Stress Analysis of Cracks Handbook. Del Research Corporation, Hellertown.
[10]
Parks, D.M. (1974) A Stiffness Derivative Finite Element Technique for Determination of Crack Tip Stress Intensity Factors. International Journal of Fracture, 10, 487-502. https://doi.org/10.1007/BF00155252
