Measurement of the fracture energy using three-point bend tests: Part 3—influence of cutting theP-δ tail

Elices, M.; Guinea, Gustavo V.; Planãs, J.

doi:10.1007/bf02472591

Cited by 211 publications

(123 citation statements)

References 7 publications

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“…Guinea et al 2 identified several sources of energy dissipation that may influence the measurement of G F , for example the influence of curtailing the P-ä tail in a bend test. 3 They concluded that when all these sources are taken into account an almost size-independent specific fracture energy G F can be obtained. Hu and Wittmann 4 have addressed the possibility that the specific fracture energy itself may not be constant along the crack path in a test specimen.…”

Section: Introductionmentioning

confidence: 99%

Determination of size-independent specific fracture energy of concrete from three-point bend and wedge splitting tests

Abdalla

Karihaloo

2003

Magazine of Concrete Research

118

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Three-point bend (TPB) and wedge splitting (WS) tests have been conducted on three different concretes and the specific fracture energy G F determined on the basis of the concept of local fracture energy. The latter is influenced by the free back surface of a notched test specimen, as explained by Hu and Wittmann. Tests on three or four specimen sizes with four notch to depth ratios confirm the idea of Hu and Wittmann that the size-independent specific fracture energy G F can be determined from measured fracture energy values that vary with the size of the specimen, W, and notch to depth ratio, a=W . More importantly, it is shown that the same size-independent G F can also be obtained by testing a single size specimen with only two notch to depth ratios, provided they are well separated (a=W ¼ 0·05 and 0·50 in TPB, and 0·2 and 0·5 in WS), thus greatly simplifying the determination of the size-dependent fracture energy G F . IntroductionThe specific fracture energy G F is the most useful material parameter in the analysis of cracked concrete structures.1 The method of experimental determination of the fracture energy, G F , and even its definition has been a subject of debate among researchers because of its variability with the size and shape of the test specimen. Guinea et al. 2 identified several sources of energy dissipation that may influence the measurement of G F , for example the influence of curtailing the P-ä tail in a bend test. 3 They concluded that when all these sources are taken into account an almost size-independent specific fracture energy G F can be obtained. Hu and Wittmann 4 have addressed the possibility that the specific fracture energy itself may not be constant along the crack path in a test specimen.The recent model of Duan et al. 5 assumes that the fracture energy required to create a crack along the crack path is influenced by the size of the fracture process zone (FPZ) which in turn is influenced by the free boundary of the test specimen. To consider the boundary effect on the propagation of FPZ, they assumed a bilinear fracture energy distribution to explain the ligament effect on the fracture energy of concrete. When this effect is included, they obtain a size-independent fracture energy, which is needed for an accurate estimate of the load bearing capacity of cracked concrete structures. This is because only in this way can the spurious size dependency introduced by the size dependency of the fracture energy itself be avoided. The influence of curtailing the tail part of the loaddeflection (P-ä) diagram in a bend test studied by Elices et al.3 in fact gives an estimate of the energy dissipation when the load tends to zero i.e. the crack approaches the free surface of the test specimen. This is in principle similar to the boundary effect proposed by Duan et al. 5 which will be further explored below.In this paper, using the concept of 'boundary effect' and 'local fracture energy distribution', the boundary effect model of Duan et al.5 is subjected to additional verification using th...

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Section: Introductionmentioning

confidence: 99%

Determination of size-independent specific fracture energy of concrete from three-point bend and wedge splitting tests

Abdalla

Karihaloo

2003

Magazine of Concrete Research

118

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“…Stable three-point bending tests were carried out on the notched prismatic samples accounting for the recommendations of Elices, Planas and Guinea (7)(8)(9). During these tests, the beams were lying on two rigid cylinders that were able to roll without hardly any friction on an anti-torsion support (please, see the picture in Figure 2).…”

Section: Three-point Bending Testsmentioning

confidence: 99%

Estudio de caracterización mecánica de probetas cerámicas a partir de una adaptación del ensayo brasileño

Iglesias¹,

Acosta²,

Yu³

et al. 2011

Mater. construcc.

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RESUMENEl ensayo de compresión diametral (ensayo brasileño) es un ensayo fácil de realizar que da como resultado la resistencia a tracción del material siempre que se cumplan una serie de proporciones entre el diámetro de la probeta, el ancho de reparto de la carga y la longitud característica del material. En este artículo presentamos unos resultados sobre probetas cerámicas cilíndricas de 40 mm de diámetro y 8 mm de espesor, elaboradas por prensado a partir de arcillas comunes y cocidas a 900 ºC. Se ha realizado una caracterización mecánica de dichas probetas, que incluye sus propiedades en fractura, y una simulación numérica del ensayo brasileño basada en el modelo de fisura cohesiva. Los resultados numéricos confirman que el tamaño y condiciones de contorno elegidos para el ensayo son apropiados para obtener la resistencia a tracción de este tipo de material cerámico con lo que este ensayo se convierte en una herramienta útil que nos permite comparar la resistencia de diferentes materiales de manera sencilla y a partir de tan sólo una pequeña cantidad de muestra.Palabras clave: cerámica, resistencia a tracción, ensayo brasileño. SUMMARYThe Brazilian Test is easy to perform and its result is the tensile strength of the material provided certain ratios are fulfilled between the diameter of the sample, the load bearing width and the characteristic length of the material. In this paper we present experimental results obtained from 8 mm-thick ceramic cylinders whose diameter was 40 mm in length. The cylinders were obtained from a standard type of clay by pressing and subsequent baking at 900 ºC. We made a complete mechanical characterization of the material, which included obtaining fracture properties, and a numerical simulation of the Brazilian test based on the cohesive crack model. Numerical results confirm that the size and boundary conditions chosen for the test are adequate to get the actual tensile strength of construction ceramics, which prove that this type of test is useful to compare the strength of several types of construction ceramics in a simple and convenient way. Besides, it requires a very small amount of material to prepare the specimen. INTRODUCCIÓNLa industria de la cerámica de construcción suele utilizar ensayos tecnológicos para caracterizar mecánicamente las piezas que produce. Son ensayos sobre piezas enteras (ladrillos, tejas, bovedillas, etc.) que reúnen el imprescindible requisito de ser repetitivos y de ser comparables con otros ensayos realizados según el mismo procedimiento. Sin embargo, cuando se trata de estudiar la composición óptima de la mezcla o de comprobar el proceso de fabricación más adecuado, dichos ensayos son incómodos, ya que requieren poner en marcha todo el proceso industrial para obtener únicamente unas pocas probetas de ensayo. Por supuesto, en laboratorio se dispone de extrusoras, hornos, etc., a escala que simulan el proceso de fabricación industrial del material, pero los procedimientos de ensayo usados en laboratorio para obtener propiedades mecánicas no está...

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“…Specifically, the measurement of the specific fracture energy as indicated by RILEM recommendation (8) provides a value that is size-dependent and has to be properly corrected. The most common methods to obtain a sizeindependent fracture energy of concrete, G F , are the boundary effect method proposed by Hu and Wittmann (4) or the simplified version (SBE) proposed by Abdalla and Karihaloo (5) and the corrections to the RILEM test proposed by Guinea et al (9)(10)(11). Although the methods are different, they are interrelated since they deal with the treatment of the contribution to the fracture energy when the test is nearing the end and the crack is approaching the back free boundary of the specimen (tail of the P-δ curve).…”

Section: Introductionmentioning

confidence: 99%

“…This paper deals with the study of the influence of the components of twelve different self-compacting concrete mixes with compressive strength varying from 39 to 124 MPa on their fracture behavior. In particular, the influence of the coarse aggregate (CA) volume, compressive strength, water to binder (w/cm) and paste to solid (p/s) ratios on the sizeindependent fracture energy of concrete (G F ) will be studied using the SBE approach proposed by Abdalla and Karihaloo (5) and the approach proposed by Guinea et al (9)(10)(11). It is shown that the two methods give very similar values of G F of the SCC mixes.…”

Section: Introductionmentioning

confidence: 99%

Effect of mix design on the size-independent fracture energy of normal- and high-strength self-compacting concrete

Cifuentes¹,

Ríos²,

Gómez³

2018

Mater. construcc.

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Self-compacting concrete has a characteristic microstructure inherent to its specific composition. The higher content of fine particles in self-compacting concrete relative to the equivalent vibrated concrete produces a different fracture behavior that affects the main fracture parameters. In this work, a comprehensive experimental investigation of the fracture behavior of self-compacting concrete has been carried out. Twelve different self-compacting concrete mixes with compressive strength ranging from 39 to 124 MPa (wider range than in other studies) have been subjected to three-point bending tests in order to determine the specific fracture energy. The influence of the mix design and its composition (coarse aggregate fraction, the water to binder ratio and the paste to solids ratio) on its fracture behavior has been analyzed. Moreover, further evidence of the objectivity of the size-independent fracture energy results, obtained by the two most commonly used methods, has been provided on the self-compacting concrete mixes. RESUMEN:Influencia de la composición de la mezcla sobre la energía de fractura de hormigones autocompactantes de resistencias media y alta. Los hormigones autocompactantes tienen una microestructura interna inherente a su composición específica. Su mayor contenido de partículas finas, en comparación con hormigones vibrados equivalentes, provoca un comportamiento diferente en fractura que afecta a los principales parámetros de fractura. En este trabajo, se ha realizado una amplia investigación experimental del comportamiento en fractura de hormigones autocompactantes. Así, se han realizado ensayos de flexión en tres puntos para determinar sus propiedades de fractura sobre 12 hormigones autocompactantes de diferente composición, con resistencias a compresión que van desde 39 hasta 124 MPa (mayor que en otros estudios). De esta forma, se ha analizado la influencia de la dosificación del hormigón y su composición (contenido en árido grueso, relación agua-cemento y pasta-sólidos) sobre su comportamiento en fractura. Además, se ha validado, para hormigones autocompactantes, la objetividad de los resultados obtenidos mediante los dos métodos habitualmente empleados para la determinación de la energía de fractura.

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Measurement of the fracture energy using three-point bend tests: Part 3—influence of cutting theP-δ tail

Cited by 211 publications

References 7 publications

Determination of size-independent specific fracture energy of concrete from three-point bend and wedge splitting tests

Determination of size-independent specific fracture energy of concrete from three-point bend and wedge splitting tests

Estudio de caracterización mecánica de probetas cerámicas a partir de una adaptación del ensayo brasileño

Effect of mix design on the size-independent fracture energy of normal- and high-strength self-compacting concrete

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