Size effect and quasi-brittle fracture: the role of FPZ
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Fracture process zone (FPZ), or the crack-tip damage zone created by crack-bridging and micro-cracking activities, in a specimen of a concrete-like material is comparable to the crack size and un-cracked ligament, so fracture is typically quasi-brittle. Increasing or decreasing the specimen size, quasi-brittle fracture transition occurs towards the toughness-controlled or strength-controlled fracture, which is known as size effect (SE). In this study it is shown that the “size-dependent” quasi-brittle fracture transition is actually due to the interaction of FPZ with the nearest structure boundary rather than the size variation, and the widely-accepted SE for geometrically-similar specimens of different sizes is only a special case of quasi-brittle fracture controlled by the FPZ/boundary interaction. Relevant SE relations are critically reviewed and explained by emphasizing the key SE mechanism, FPZ/boundary interaction.
KeywordsFracture process zone (FPZ) Size effect (SE) Boundary effect (BE) Tensile strength Fracture toughness Scaling
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- ASTM (1990) E399-90, Standard test method for plane-strain fracture toughness testing of high strength metallic materials. Amer Soc Testing Mater, PhiladelphiaGoogle Scholar
- Duan K, Hu XZ (2004a) Specimen boundary induced size effect on quasi-brittle fracture. Strength Fract Complex 2(2): 47–68Google Scholar
- Duan K, Hu XZ (2004b) Asymptotic analysis of boundary-effect on strength of concrete, In: Li VC, Leung CKY, Willam KJ, Billington SL (eds) Fracture mechanics of concrete structures. In: Proceedings of FraMCoS-5, April 12–16, 2004, Vail, Colorado, USA, Ia-FraMCoS, vol 1, pp 197–204Google Scholar
- Hu XZ (1998) Size effects in toughness induced by crack close to free edge. In: Mihashi H, Rokugo K (eds) Fracture mechanics of concrete structures. Proceedings of FraMCoS-3, Japan. AEDIFICATIO Publishers, Freiburg, Germany, 1998, pp 2011–2020Google Scholar
- Hu XZ, Duan K (2005) Size effect on fracture of MEMS materials. J Mater Sci Tech 21(Suppl 1): 47–50Google Scholar