Two-parameter fracture mechanics: Evaluation of T-stress for a general three-point-bend specimen

0454459 - ÚFM 2016 RIV ES eng C - Konferenční příspěvek (zahraniční konf.)
Seitl, Stanislav - Viszlay, Viliam - Cifuentes, H. - Canteli, A.
Two-parameter fracture mechanics: Evaluation of T-stress for a general three-point-bend specimen.
Anales de Mecanica de la Fractura. Zamora: Grupo Espanol de Fractura, 2015, s. 310-315. ISSN 0213-3725.
[32 SCFSI/32 GEF Spanish Conference on Fracture and Structural Integrity Encuentro del Grupo Espanol de Fractura /32./. Zamora (ES), 27.04.2015-29.04.2015]
Institucionální podpora: RVO:68081723
Klíčová slova: Fracture * stress intensity factor * T-stress * constraint * three point bending test * FEM
Kód oboru RIV: JL - Únava materiálu a lomová mechanika

Fracture properties of structural materials are very often determined by using the geometry three-point bending of notched beams. For cement-based composites it is standardized according to the RILEM [1] recommendations. The proportions of the specimen characterization dimension (depth or width, W) and the span between supports (S) are usually kept at a certain standardized value (S/W=3), at least in the field of the fracture testing of metals, where test specimens are manufactured with precision using machine tools. For these cases the given span-to-depth ratio of S/W = 4 and 8 is used according to the standards for testing metals (ASTM). However, in the case of cementitious composites, the situation is often different and only specimens with non-standard proportions (different S/W values) are available. Thus, for evaluation of the stress intensity factor of a general three-point bending specimen the expression for pure bending postulated by Guinea et al. [2] can be employed with convenience. However, no general expression evaluating the level of constraint is available in literature. It is obvious that various specimen proportions, in this case ruled by the S/W ratio, are characterized by various constraint levels. The aim of this contribution is to introduce an expression for estimation of the first and second terms of the Williams series for general three-point bending specimens for both cases (pure bending and three-point bending). This expression can be used to obtain the level of constraint easily, which is then applied in fracture analysis. The expressions should be valid for any crack length and for any span-to-depth ratio (larger than 2). The accuracy of the expression for stress intensity factors is verified by comparing its values to the results of conducted finite element computations and to available expressions proposed by other authors. The influence of boundary conditions on the constraint level for both configurations is discussed.
Trvalý link: http://hdl.handle.net/11104/0255412