Brittle fracture investigation from disc specimen weakened by U- notch in mixed mode I + II

The influence of friction on the determination of rock fracture toughness

“…The numerical models of rock specimens with CSTBD configuration and NSCB configuration established in ABAQUS software. ABAQUS software has been widely used to solve the stress intensity factors of models under various complex conditions, and the simulation results of this software are consistent with that obtained by theoretical methods [43][44][45][46][47][48][49][50] . Table 1 shows the material parameters, load level and specimen size in the model.…”

On the use of different diametral compression cracked disc shape specimens for introducing mode III deformation

“…The testing equipment and loading setup for conducting in‐plane fracture tests (i.e., modes I and II) are relatively simple and such tests can be done by the conventional testing machines and common fixtures such as tensile/compression and three or four‐point bend test setup. Accordingly, a number of test specimens including circular samples (Brazilian disc and flatten Brazilian disc under compression, 1–10 semi‐circular bend, 6,11–17 center crack ring under compression, 18–21 edge notch disc bend (ENDB), 22–26 and circular edge crack wedge loading 27 ), beam samples (three‐point long beam, 28–31 three‐point short beam, 32–36 and four‐point bend beam 37–44 ), and thin plate shape samples (compact tension shear, 45–47 square plate in tension, 48,49 and triangular plate in bending 50–52 ) are among the frequently used test specimens employed in the past for mode I and mixed I/II fracture testing of different brittle and quasi brittle materials such as rock, geo‐materials, concrete, polymers, ceramics, and etc. However, for introducing out‐of‐plane or mode III deformation in a cracked specimen via a straightforward and direct manner, it is usually necessary to apply torsional‐type loads.…”

“…The testing equipment and loading setup for conducting in-plane fracture tests (i.e., modes I and II) are relatively simple and such tests can be done by the conventional testing machines and common fixtures such as tensile/compression and three or four-point bend test setup. Accordingly, a number of test specimens including circular samples (Brazilian disc and flatten Brazilian disc under compression, [1][2][3][4][5][6][7][8][9][10] semi-circular bend, 6,[11][12][13][14][15][16][17] center crack ring under compression, [18][19][20][21] edge notch disc bend (ENDB), [22][23][24][25][26] and circular edge crack wedge loading 27 ), beam samples (three-point long beam, [28][29][30][31] three-point short beam, [32][33][34][35][36] and four-point bend beam [37][38][39][40][41][42][43][44] ), and thin plate shape samples (compact tension shear,…”

Influence of testing method on mode II fracture toughness (KIIc) of hot mix asphalt mixtures

“…[8][9][10][11][12][13][14][15] This is because making laboratory test sample in the mentioned geometries is easier than other geometries and shapes for asphalt mixtures. Center cracked circular disc (CCCD) specimen subjected to compression diametral force (often known as Brazilian disc), 16,17 semi-circular bend (SCB) specimen containing either vertical or inclined edge crack, [18][19][20][21][22][23][24][25][26][27] edge notch disc bend (ENDB) specimen, [28][29][30][31][32][33][34][35][36] and disc specimen weakened by U-notch 37 are among the circular shape test samples in this regard that are able to introduce both mode I and mode II deformations in asphaltic samples. Other disc shape test samples such as edge notch compressed disc (ENDC), [38][39][40][41] edge notch disc double notch disc compression (DNDC), 42 wedge splitting (WS), 43,44 and disc shape compact tension (DCT) specimen [45][46][47] fail in producing mode II case, and they can be used mainly for mode I fracture testing.…”

“…Stewart et al 47 investigated the thickness effect on mode I fracture behavior of HMA material manufactured in the shape of DCT specimen. Using the ENDB and ENDC specimens, Aliha and coworkers [28][29][30][31][32][33][34][35][36][37] determined the mode I fracture toughness value at low temperature condition for different HMA, WMA, and stone mastic asphalt (SMA) materials containing different types of modifiers, additive, fibers, recycled asphalt pavement (RAP), and so forth. In addition, recently, two standard testing configurations, namely, (i) semi-circular bend (SCB) and (ii) circular compact tension (CCT) specimens, have also been suggested by ASTM for determining the fracture toughness of asphalt mixtures under pure mode I loading condition.…”