Investigation of geometrical factors for determining fracture toughness with the modified ring test

Alpay, Ceyda
Modified Ring specimens are of the shape of discs having a hole inside and flattened ends. These specimens are used for determination of Mode I fracture toughness. Finite element program, named ABAQUS, is used for numerical modeling for finding stress intensity factors. Varying disc geometries were used for the experiments and numerical modeling in which size of the flat ends, radius of the hole inside, and external radius of the specimen were varied. Experiments were done by using pink Ankara andesite. Effects of internal hole radius, external disc radius and size of the flat ends on both stress intensity factor and fracture toughness were studied. In order to compare the results, fracture tests with semi-circular specimens under three point bending (SCB) were also performed. From a similar previous study, fracture toughness values of gray andesite were recalculated and compared to the fracture toughness values of pink andesite for varying geometrical factors. Size effect studies were performed as well for varying diameter of core specimens.Fracture toughness values of andesite were found to increase with increasing specimen size. Fracture toughness of 100 mm specimens was determined as 1.11±0.07 MPa√m, whereas fracture toughness of 75 mm specimens was 0.96±0.08 MPa√m. 100 mm or larger diameter specimens were suggested for the fracture toughness determination with the modified ring tests.


Effects of geometrical factors on fracture toughness using semi-circular bending type specimens
Het, Kıvanç; Tutluoğlu, Levent; Department of Mining Engineering (2008)
Semi-circular specimens (SCB) under three point-bending which are commonly used for fracture testing of rocks were used here for fracture mechanics tests. A total of 65 specimens were tested by using Ankara andesite rock. Investigations including the effects of initial notch thickness, different loading span ratios (S/R), flattened loading end, and little dimensional variations when preparing the specimens were carried out. Stress intensity factors for specimens with different geometries were computed indiv...
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....
Development of a new method for mode I fracture toughness test on disc type rock specimens
Alkılıçgil, Çiğdem; Tutluoğlu, Tevfik Levent; Department of Mining Engineering (2006)
A new testing method was introduced and developed to determine Mode I fracture toughness of disc type rock specimens. The new method was named as Straight Notched Disc Bending and it uses disc specimens under three-point bending. 3D Numerical modeling was carried out with a finite element program ABAQUS to find stress intensity factors for both well-known Semi-circular Bending specimen models and Straight Notched Disc Bending specimen models for varying disc geometries. Both specimen types included notches ...
Electrical potential response of the quartz bearing rocks under uniaxial loading
İnal, Hikmet Sinan; Bilgin, Hasan Aydın; Department of Mining Engineering (2004)
The electric potential changes under uniaxial loading in some minerals and rocks have long been recognized. To daylight the electrical response of some minerals and rocks against applied stress, both theoretical studies and laboratory experiments are conducted. Some theories are also proposed by different researchers, in order to explain the electric potential variations. However, the mechanisms leading to electrical potential generation have not been fully explained yet. In the explanation of electric pote...
A computer simulator for ball mill grinding
Yeşilay, Yasemin; Hoşten, Çetin; Department of Mining Engineering (2004)
Ball mill grinding is an important operation in the processing of most minerals, in that it may be used to produce particles of the required size and shape, to liberate minerals from each other for concentration purposes, and to increase the powder surface area. Grinding of minerals is probably the most energy consuming task and optimization of this operation has vital importance in processing plant operations to achieve the lowest operating costs. Predicting the complete product size distribution, mill spe...
Citation Formats
C. Alpay, “Investigation of geometrical factors for determining fracture toughness with the modified ring test,” M.S. - Master of Science, Middle East Technical University, 2008.