Fatigue crack propagation viscoelastic

Work by Schapery, Saxena, Wilhams, and others details the analysis of cracks in creeping, strain rate dependent materials, and provides a predictive basis for the apparently brittle nature of FCP in UHMWPE [43-48]. Particularly usefid are the models developed by Schapery and Wilhams, which directly link the intrinsic, constitutive viscoelastic relaxation behavior of the material to the advance of a stable crack tip [46,48]. The power of these models is the predictive nature of the mechanics in relating ECP dynamics to the material s viscoelastic behavior that is eashy measured in a simple one-dimensional creep test The elementary consequences of the models result in the static mode fatigue crack propagation behavior that is observed in UHMWPE, and thus potentially provide a first-principles explanation of the fatigue and fracture behavior by the material. 

Material behavior have many classifications. Examples are (1) creep, and relaxation behavior with a primary load environment of high or moderate temperatures (2) fatigue, viscoelastic, and elastic range vibration or impact (3) fluidlike flow, as a solid to a gas, which is a very high velocity or hypervelocity impact and (4) crack propagation and environmental embrittlement, as well as ductile and brittle fractures. 

Earlier authors proposed theories which predict the speed of viscoelastic crack propagation, by assigning a detailed structure to the crack tip, both under unstable and subcritical or fatigue failure. We mention Knauss (1970, 1974), Knauss and Dietmann (1970), Mueller and Knauss (1971) and a review by Knauss (1973) also the work of Wnuk (1971-73b). Later, there was the work of Schapery (1974-79), McCartney (1977-79) and Golden and Graham (1984). See also Kanninen and Popelar (1985). Majidzadeh et al. (1976) discuss various models in the context of application to pavement design. McCartney (1987) is concerned with crack extension criteria for fibre-reinforced composites. 

Willis, J.R. (1967b) Crack propagation in viscoelastic media. J. Mech. Phys. Solids 15, 229- 240 Wnuk, M.P. (1971) Subcritical growth of fracture (inelastic fatigue). Int. J. Fract. Mech. 7, 383-407 Wnuk, M.P. (1973a) Slow growth of cracks in a rate sensitive Tresca solid. Eng. Fract. Mech. 5, 605-626... 

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