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S. Muralidhara - One of the best experts on this subject based on the ideXlab platform.
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Size independent Fracture Energy from Fracture Energy release rate in plain concrete beams
Engineering Fracture Mechanics, 2013Co-Authors: S. Muralidhara, B. K. Raghu Prasad, R. K. SinghAbstract:Size independent Fracture Energy and size effect on Fracture Energy are the key concerns for characterization of concrete Fracture. Although there have been inconsistencies in results, a consensual fact is that the Fracture Energy from a large specimen is size independent. The Fracture Energy is proportional to the size of the Fracture process zone (FPZ). FPZ size increases with size of the specimen, but the rate of increase of FPZ size decreases with increase in specimen size 1] implying that rate of increase of Fracture Energy decreases with increase in specimen size, more appropriately with increase in un-cracked ligament length. The ratio of Fracture Energy to the un-cracked ligament length almost becomes a constant at larger un-cracked ligament lengths. In the present study an attempt is made to obtain size independent Fracture Energy from Fracture Energy release rate. (C) 2012 Elsevier Ltd. All rights reserved.
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size independent Fracture Energy in plain concrete beams using tri linear model
Construction and Building Materials, 2011Co-Authors: S. Muralidhara, B Raghu K Prasad, Bhushan Lal Karihaloo, R. K. SinghAbstract:The boundary effect or the size effect on the Fracture properties of concrete has been studied assuming a bi-linear model for the distribution of local Fracture Energy concept. Boundary effect is observed not only near the back boundary but also near the notch tip, where a fictitious boundary seems to exist, separating the linear and non-linear Fracture zones. In this paper a tri-linear function is assumed for the local Fracture Energy distribution along the ligament and expressions relating RILEM Fracture Energy and the size-independent Fracture Energy are developed. Transition ligament length measurements based on the acoustic emission (AE) histogram of events are used to obtain size-independent Fracture Energy. Length of the Fracture process zone is identified in the AE histogram and compared with the value obtained from softening beam model. There seems to be a good agreement between the results.
R. K. Singh - One of the best experts on this subject based on the ideXlab platform.
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Size independent Fracture Energy evaluation for plain cement concrete
Fatigue & Fracture of Engineering Materials & Structures, 2015Co-Authors: N. Trivedi, R. K. Singh, Jayanta ChattopadhyayAbstract:The present work deals with the investigation of a robust analytical scheme to assess the size-independent Fracture Energy of concrete. The study involves the numerical modelling of three-point bend (TPB) concrete beams that are geometrically similar, having constant length to depth ratio with varying range of notch to depth (a/W) ratios. The unique nonlinear behaviour of concrete 1material is incorporated through Fracture Energy-based strain-softening model in the finite-element numerical simulation. The International Union of Laboratories and Experts in Construction Materials, Systems and Structures (RILEM) Fracture Energy values are evaluated through numerical simulation of several set of experimentally observed load-load line displacement response. The RILEM Fracture Energy values associated with geometrically similar beams have been utilised to develop a methodology for assessment of the size-independent Fracture Energy of concrete. The numerically predicted and experimentally evaluated size-independent Fracture Energy using the RILEM Fracture Energy values are found to be in close agreement.
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Size independent Fracture Energy from Fracture Energy release rate in plain concrete beams
Engineering Fracture Mechanics, 2013Co-Authors: S. Muralidhara, B. K. Raghu Prasad, R. K. SinghAbstract:Size independent Fracture Energy and size effect on Fracture Energy are the key concerns for characterization of concrete Fracture. Although there have been inconsistencies in results, a consensual fact is that the Fracture Energy from a large specimen is size independent. The Fracture Energy is proportional to the size of the Fracture process zone (FPZ). FPZ size increases with size of the specimen, but the rate of increase of FPZ size decreases with increase in specimen size 1] implying that rate of increase of Fracture Energy decreases with increase in specimen size, more appropriately with increase in un-cracked ligament length. The ratio of Fracture Energy to the un-cracked ligament length almost becomes a constant at larger un-cracked ligament lengths. In the present study an attempt is made to obtain size independent Fracture Energy from Fracture Energy release rate. (C) 2012 Elsevier Ltd. All rights reserved.
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size independent Fracture Energy in plain concrete beams using tri linear model
Construction and Building Materials, 2011Co-Authors: S. Muralidhara, B Raghu K Prasad, Bhushan Lal Karihaloo, R. K. SinghAbstract:The boundary effect or the size effect on the Fracture properties of concrete has been studied assuming a bi-linear model for the distribution of local Fracture Energy concept. Boundary effect is observed not only near the back boundary but also near the notch tip, where a fictitious boundary seems to exist, separating the linear and non-linear Fracture zones. In this paper a tri-linear function is assumed for the local Fracture Energy distribution along the ligament and expressions relating RILEM Fracture Energy and the size-independent Fracture Energy are developed. Transition ligament length measurements based on the acoustic emission (AE) histogram of events are used to obtain size-independent Fracture Energy. Length of the Fracture process zone is identified in the AE histogram and compared with the value obtained from softening beam model. There seems to be a good agreement between the results.
Tatsuki Ohji - One of the best experts on this subject based on the ideXlab platform.
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Fracture Energy of an Aligned Porous Silicon Nitride
Journal of the American Ceramic Society, 2004Co-Authors: Yoshiaki Inagaki, Tatsuki Ohji, Shuzo Kanzaki, Yasuhiro ShigegakiAbstract:The Fracture Energy of a porous silicon nitride with aligned fibrous grains was investigated, using a chevron-notched-beam technique. A crack was constrained to propagate normal to the grain alignment. The obtained Fracture Energy was ∼500 J/m2, which was ∼7 times larger than that of a dense silicon nitride with randomly oriented fibrous grains. The large Fracture Energy was attributable primarily to the sliding resistance associated with interlocking grains.
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High‐Temperature Fracture Energy of Superplastically Forged Silicon Nitride
Journal of the American Ceramic Society, 2004Co-Authors: Naoki Kondo, Yoshiaki Inagaki, Yoshikazu Suzuki, Tatsuki OhjiAbstract:The Fracture Energy of superplastically forged silicon nitride, where rodlike silicon nitride grains are aligned in one direction, was investigated at high temperatures from 1100° to 1300°C and at room temperature. Bending tests using chevron-notched beams were conducted at two displacement rates, 0.05 and 0.005 mm/min. The superplastically forged silicon nitride showed remarkably high Fracture energies, 200–630 J/m2. The Fracture Energy was largely dependent on the temperature and the displacement rate. The high Fracture Energy was attributed to grain pullout enhanced by the softened grain-boundary glassy phase and the aligned rodlike grains.
František Vodák - One of the best experts on this subject based on the ideXlab platform.
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Size independent Fracture Energy of concrete
Construction and Building Materials, 2012Co-Authors: Vítězslav Vydra, Karel Trtík, František VodákAbstract:Abstract It has been confirmed by many authors that the specific Fracture Energy of concrete determined by laboratory experiments depends on the shape and size of the specimen because the local Energy in the Fracture process zone is influenced by the free surface of the specimen. As the crack propagates towards the back face of the specimen the shape of the Fracture process zone changes having a direct impact on the local Fracture Energy. In this paper, the authors present an original local Fracture Energy concept within a framework of effective crack model. Within this model the crack is modeled as an “elastically equivalent notch” with a depth equal to the effective crack length a e . The local Fracture Energy can be – within this model – determined using three-point-bend tests as a derivative of Energy release rate with respect to the effective crack length a e . As long as the local Fracture Energy exhibits a plateau , size-independent Fracture Energy can be determined. The main advantage of suggested method is that it does not require (contrary to other methods) testing of many samples of different shapes, sizes or notch to depth ratios, thus greatly simplifying the determination of the size independent Fracture Energy.
Folker H. Wittmann - One of the best experts on this subject based on the ideXlab platform.
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Size effect on specific Fracture Energy of concrete
Engineering Fracture Mechanics, 2006Co-Authors: Kai Duan, Folker H. WittmannAbstract:Abstract Size effect on the specific Fracture Energy GF of concrete can be adequately modelled by an uneven Fracture Energy distribution along the crack path induced by the specimen boundary influence. The boundary influence on GF can be neglected only if a specimen is very large so that the boundary region is a very small portion of the total Fracture area. The underlying principle on the specimen boundary induced size effect provides a simple and logical explanation for the commonly observed size effect on GF. The boundary effect model recently proposed by the authors is used in this paper to quantitatively evaluate the specimen boundary influence so that the size-independent Fracture Energy is derived, which otherwise can only be measured with very large concrete specimens. New experimental results from a very different material system, polymer, are analysed together with concrete results by the simple boundary effect model.
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boundary effect on concrete Fracture and non constant Fracture Energy distribution
Engineering Fracture Mechanics, 2003Co-Authors: Kai Duan, Xiaozhi Hu, Folker H. WittmannAbstract:Abstract This paper extends the local Fracture Energy concept of Hu and Wittmann [29] , [30] , and proposes a bilinear model for boundary or size effect on the Fracture properties of cementitious materials. The bilinear function used to approximate the non-constant local Fracture Energy distribution along a ligament is based on the assumption of the proportionality of the local Fracture Energy to the Fracture process zone (FPZ) height and characterises the FPZ height reduction when approaching a specimen back boundary. The bilinear function consists of a horizontal straight line of the intrinsic Fracture Energy GF and a declining straight line that reduces to zero at the back boundary. It is demonstrated that using the bilinear model, the size-independent Fracture Energy GF can be estimated from the Fracture Energy data measured on laboratory-size specimens, and the intersection of these two linear functions, defined as the transition ligament, represents the influence of the back boundary on the Fracture properties. It is also demonstrated that the specimen size alone is not sufficient to characterise the size effect in the Fracture properties observed on laboratory-size specimens.
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Thickness Effect on Fracture Energy of Cementitious Materials
Cement and Concrete Research, 2003Co-Authors: Kai Duan, Folker H. WittmannAbstract:This paper studies the thickness effect on the Fracture Energy of cementitious materials based on a local Fracture Energy concept. Similar to the specimen back boundary, the presence of two free surfaces in the thickness direction also influences the local Fracture Energy dissipation, leading to the boundary or thickness effect. A bilinear local Fracture Energy model originally developed to characterise the ligament or back boundary effect on the Fracture Energy is further developed to consider variations of the local Fracture Energy in the thickness direction. The proposed model is used to analyse available experimental data from the literature. The predictions from the model are in a good agreement with the experiments.
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Probabilistic aspects of Fracture Energy of concrete
Materials and Structures, 1994Co-Authors: Folker H. Wittmann, V. Slowik, A. M. AlvaredoAbstract:A test method to determine Fracture Energy and strain-softening in direct tension is described. Experimental results on cylinders of equal diameter and varying length are reported. It is found that the tensile strength decreases with increasing volume while the Fracture Energy remains constant within the observed volume range. By means of numerical simulation, it is shown that in a direct tension test several Fracture process zones appear in the initial states of cracking and that final rupture is induced by the development of only one of these Fracture zones. This phenomenon has been observed experimentally by other authors. A comparatively large number (44) of identical samples were tested by using the wedge-splitting test. Half the specimens were grooved. The Fracture Energy of the grooved and ungrooved specimens turned out to be the same within the given range of accuracy. It was observed experimentally and simulated numerically that in grooved specimens the crack is forced to follow a ragged Fracture surface which is statistically not the weakest one. In an ungrooved specimen the crack path generally diverts from the centre line and advances through weaker zones. For the formation of these skew cracks, however, more Energy is consumed due to aggregate interlock. In addition, the Fracture process zone observed in ungrooved specimens is generally wider.
