Effect of loading span on tensile mode fracture toughness for three-point bend specimen geometries

Karataş Batan, Ceren
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 circular disk geometry (SNDB). Modeling procedure and stress intensity computation work were verified by 3D modeling of square plate and semi-circular bend geometries under three-point bending loads and comparing the SIF results to the relevant analytical solutions of these two geometries. Tensile mode fracture toughness tests were conducted on notched circular plate type disk and semi-circular disk andesite rock specimens. Tests were carried out under three-point bending loads. 0.5 mm wide notches providing a crack length/radius ratio of a/R=0.20 were machined to the specimens by a saw. Mode I fracture toughness tests were performed on straight notched disk bending (SNDB) disk specimens of thicknesses 50 mm and 60 mm. Loading spans were varied between 40 mm and 90 mm corresponding to span/radius ratios of S/R=0.40 to 0.90. Using the same a/R and S/R configurations, three-point bend tests were conducted with the ISRM suggested semi-circular bending (SCB) core specimen geometry for comparison purposes. SCB tests were conducted with 50 mm thickness as suggested. Ankara Gölbaşı Andesite rock type was used in both test series. Mode I fracture toughness values of Ankara Gölbaşı Andesite were found as KIc=1.39


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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...
Mode I fracture toughness determination with straight notched disk bending method
Tutluoğlu, Levend (2011-12-01)
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...
Effects of specimen height and loading span on the fracture toughness of disc type rock specimens under three point bending
Tez, Yaşar Burkay; Tutluoğlu, Levent; Department of Mining Engineering (2008)
A relatively new fracture toughness testing method called Straight Notched Disc Bending (SNDB) was used before for fracture testing of Ankara Andesite and Afyon Marble cores. In this work to investigate the applicability of the new method to other rock types. With a preliminary notch of 10 mm, straight notched disc type specimens with a diameter of 75 mm were loaded by three-point bending loads. Investigation of effect of specimen height on the stress intensity factor and fracture toughness was carried out....
Essari, A.; Sariuglo, F.; Petrovic, Z.; Sedmak, A.; Samardzic, I. (2016-01-01)
In this study, Al-8Fe-8Si-1.4V/SiCp composites fabricated by squeeze casting process were age-hardened to study the influence of heat treatment on mechanical properties, such as hardness, bending strength and modulus of elasticity. The cast samples were solid soluted at 540 degrees C for one hour, then quenched in water to room temperature, and finally aged at 190 degrees C for 2, 4, 6, 8 and 10 hours for hardness test and at 195 degrees C for 2, 6 and 10 hours for bending strength determination.
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...
Citation Formats
C. Karataş Batan, “Effect of loading span on tensile mode fracture toughness for three-point bend specimen geometries,” Thesis (M.S.) -- Graduate School of Natural and Applied Sciences. Mining Engineering., Middle East Technical University, 2020.