13th International Conference on Fracture June 16–21, 2013, Beijing, China -10- of drawing or soon after completion of drawing results in a continuous CL growth. In contrast with that, a ductile behavior (creep) of drawn microfibers within AZ is the underlying cause of the discontinuous CL growth. A transition in the mechanism and kinetics of SCG takes place at certain combination of temperature and SIF. It suggests that commonly used extrapolation of data obtained at elevated temperature into service condition is limited by the requirement of similarity in the mechanisms and kinetics of fracture process. Therefore, the commonly used acceleration technique based on extrapolation of 1-1.5 years elevated temperature test data into 50 and 100-year life in service condition is a suspect. In addition, there is a hidden assumption that after decades of services the material retains the same properties as the one tested for a year or two. The material aging process (chemical degradation and/or physical aging) commonly takes place over time. It should be taken into consideration. An alternative approach to the lifetime assessment problem is a formulation of a sound physical model of initiation and SCG processes and numerical simulation of brittle fracture. References [1] A. Chudnovsky, Experimental and theoretical studies of slow crack growth in engineering polymers, Key Eng Mat, 345 (2007) 493–496. [2] A. Chudnovsky, A. Dolgopolsky and M. Kachanov: Elastic interaction of a crack with a microcrack array—I. Formulation of the problem and general form of the solution, Int J Solids Struct, 23 (1987) 1–10. [3] A. Chudnovsky, A. Dolgopolsky and M. Kachanov: Elastic interaction of a crack with a microcrack array—II. Elastic solution for two crack configurations (piecewise constant and linear approximations), Int J Solids Struct, 23 (1987) 11–21. [4] M. Ben Ouezdou and A. Chudnovsky, Semi-empirical crack tip analysis, Int J Fracture, 37 (1988) 3–11. [5] S. Wu and A. Chudnovsky, A., Elastic interaction of a crack with a random array of microcracks, Int J Fracture, 49 (1991) 123–140. [6] Z. Zhou, H. Zhang and A. Chudnovsky, Temperature effects on slow crack growth in pipe grade PE, Proceedings of the 68th Annual Technical Conference & Exhibition, ANTEC 2010, Society of Plastics Engineers, Orlando, FL, 2010, pp. 679–684. [7] A. Chudnovsky, Z. Zhou, and H. Zhang, Lifetime Assessment of Engineering Thermoplastics, Int J Eng Sci, 59 (2012) 108–139. [8] H. Zhang, Z. Zhou and A. Chudnovsky, Computational Method for CL Model, … [9] J. D. Eshelby, Energy relations and the energy-momentum tensor in continuum mechanics, in: M. F. Kannien, W. F. Adler, A. R. Rosenfeld, and R. I. Taffee (Eds.), Inelastic Behavior of Solids, McGraw-Hill, New York, 1970, pp. 77–115.
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