Mode I fracture toughness determination with straight notched disk bending method

A new method called the straight notched disk bending method is developed for mode I fracture toughness determination using rock cores. Disk specimens of andesite and marble having a single straight edge notch were subjected to three-point bending loads. Dimensionless stress intensity factor estimations and fracture toughness tests were conducted for different notch lengths, span lengths, thicknesses and diameters of the cylindrical rock specimens. Stress intensity factors were computed by three-dimensional finite element modeling and the results were presented for a wide range of specimen geometrical parameters. Results of experiments were compared to the results of well-known mode I fracture toughness testing methods. For specimens having thickness equal to the radius, mode I fracture toughness was lower and close to the results obtained by semi-circular bending method. When thickness was increased and doubled, mode I fracture toughness increased and approached to the value found by the suggested cracked chevron notched Brazilian disk method. Advantages of the new method included easy specimen preparation and testing procedure, stiffer specimen geometry, smaller fracture process zone, and flexibility of the specimen geometry for the investigation of the size effect behavior.


Investigation of proper specimen geometry for mode I fracture toughness testing with flattened Brazilian disc method
KELES, Cigdem; Tutluoğlu, Levend (2011-05-01)
Investigation of geometrical parameters for flattened Brazilian disc method is important, since this is a simple and attractive method for mode I fracture toughness testing on rock cores. Evaluating numerical modeling results, a parametric equation in terms of principal stresses at the center of the disc and the loading angle of the flattened end was developed. An equation was proposed for maximum stress intensity factors at critical crack lengths around stable to unstable crack propagation. Comparing fract...
Effects of geometric factors on mode I fracture toughness for modified ring tests
Tutluoğlu, Levend (2012-04-01)
Stress intensity factors of specimen models with various external diameters, inner hole diameters, and extents of flattened loading boundaries for the modified ring testing method for mode I fracture are computed by finite element modeling. Effects of boundary conditions and geometric factors on stress intensity factor computation are analyzed. Parametric expressions are proposed to estimate critical crack length position and corresponding maximum stress intensity factor. An expression in terms of inner hol...
Effect of loading span on tensile mode fracture toughness for three-point bend specimen geometries
Karataş Batan, Ceren; Tutluoğlu, Levend; Department of Mining Engineering (2020)
Straight notched disk bending specimen geometry has a potential to find size independent mode I fracture toughness, since the thickness of the disk loaded by threepoint bending can be increased. Increasing the thickness and decreasing the loading span of bending reduces the severe bending action at the notch tip and a pure tensile mode stress state can be achieved at and ahead of the crack tip. 3D finite element program (ABAQUS) was used for computing the stress intensity factors by numerical modeling of ci...
Development of specimen geometries for mode i fracture toughness testing with disc type rock specimens
Alkılıçgil, Çiğdem; Tutluoğlu, Levent; Department of Mining Engineering (2010)
Flattened Brazilian disc and modified ring test methods are attractive methods being simpler compared to the other mode I fracture toughness testing methods on rock cores. The aim of this study is to improve these simple methods to yield fracture toughness values that are close to the ones determined by the suggested methods. ABAQUS finite element program was used to determine stress intensity factors of models with various dimensions. Comparing fracture toughness to the results obtained by semicircular ben...
Shear mode fracture toughness of rock with different core-based specimen geometries
Het, Kıvanç; Tutluoğlu, Levend; Department of Mining Engineering (2014)
Shear mode fracture toughness tests on core specimens of gabbro rock were conducted. Tests were conducted under three-point bending and Brazilian type indirect compression load. In order to investigate the reasons for having different fracture toughness values with the different testing methods and geometries, modeling with ABAQUS software was conducted. Stress distributions around the mode II notches were analyzed. In order to assess which specimen geometry results in similar stress distributions as in the...
Citation Formats
L. Tutluoğlu, “Mode I fracture toughness determination with straight notched disk bending method,” INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES, pp. 1248–1261, 2011, Accessed: 00, 2020. [Online]. Available: