Geometry effects and statistical analysis of mode I fracture in guiting limestone

Influence of thermal treatment on mode I fracture toughness of certain Indian rocks

“…In past few years, the semi-circular bend (SCB) specimen proposed by Chong et al (1987) has gained the attention of many researchers including Lim et al (1993Lim et al ( , 1994; Kuruppu (1997Kuruppu ( , 1998Kuruppu ( , 2000; Kuruppu and Chong (2012); Kuruppu et al (2014) and Ayatollahi (2015) for the measurement of fracture toughness, because of factors such as convenient sample preparation, simple geometry, minimal requirement of machining, loading configuration and the convenience of the experimental set-up that can be achieved by applying three-point compressive loading using a common laboratory load frame and low requirement of materials (Aliha et al, 2012;Ayatollahi and Aliha, 2007;Ayatollahi, 2015;Chong and Kuruppu, 1984;Kuruppu et al, 2014). Normally, geo-materials are weak under extensional force and, hence, the applied force for the measurement of fracture toughness should be such that it promotes tensile fracturing.…”

Mixed mode fracture analysis using extended maximum tangential strain criterion

“…Looking through the literature reveals that although the GMTS criterion successfully predicts the fracture toughness as well as the size effects under mixed mode conditions [34 -36], it fails to provide an acceptable predictions in pure mode II (or predominantly pure mode II) condition for many brittle materials, such as ceramics, resins and rocks [37 -39]. In many cases, the second nonsingular stress term and even first five terms of the tangential stress field are used to predict the test results and the GMTS criterion could not estimate the experimental data in a good accuracy [40,41]. In these cases, considering a large number of tangential stress terms will lead to a complex formulation of the tangential stress based fracture criteria.…”

ISRM-Suggested Method for Determining the Mode I Static Fracture Toughness Using Semi-Circular Bend Specimen

“…They include those based on short rod (SR) specimen, chevron bend (CB) specimen and cracked chevron-notched Brazilian disk (CCNBD) specimen (ISRM 2007). The semi-circular bend (SCB) specimen has been widely used for fracture toughness determination of geomaterials owing to inherent favourable properties such as its simplicity, minimal requirement of machining and the convenience of testing that can be accomplished by applying 3-point compressive loading using a common laboratory load frame (Chong and Kuruppu 1984;Chong et al 1987;Lim et al 1993Lim et al , 1994Ayatollahi and Aliha 2007;Aliha et al 2012;Karfakis and Akram 1993;Obara et al 2006Obara et al , 2007aObara et al , 2007bObara et al , 2009Molenar et al 2002). As geomaterials are weak in tension, fracture tests should preferably be conducted with compressive loading in such a way that tensile fractures are induced.…”