Mechanisms of Fatigue Crack Propagation in Metals, Ceramics and Composites: Role of Crack Tip Shielding*
نویسنده
چکیده
Crack tip shielding phenomena, whereby the "effective crack-driving force" actually experienced at the crack tip is locally reduced, are examined with reference to fatigue crack propagation behavior in metals, composites and ceramics. Sources of shielding are briefly described in terms of mechanisms relying on the production of elastically constrained zones which envelop the crack (zone shielding), on the generation of wedging, bridging or sliding forces between the crack surfaces (contact shielding) and on crack path deflection attd meandering. Examples are taken from the fatigue behavior of high strength lithium-containing aluminum alloys, aluminum alloy-aramid fiber-epoxy laminate composites, and zircon& ceramics. It is shown that, whereas crack tip shielding can provide a potent means of enhancing "resistance" to crack growth, such extrinsic toughening mechanisms can result in the apparently anomalous behavior of "small cracks" and to the susceptibili O' of brittle materials to fatigue faihtre.
منابع مشابه
Mechanics and mechanisms of fatigue damage and crack growth in advanced materials
The mechanisms of fatigue-crack propagation in ceramics and intermetallics are examined through a comparison of cyclic crack-growth behavior in ductile and brittle materials. Crack growth is considered to be a mutual competition between intrinsic mechanisms of crack advance ahead of the crack tip, which promote crack growth, and extrinsic mechanisms of crack-tip shielding behind the tip, which ...
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