Development of specimen geometries for mode i fracture toughness testing with disc type rock specimens

Download
index.pdf
2010
Alkılıçgil, Çiğdem
Show full item record
296
views
141
downloads
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 bending method tests (0.94 MPa√m for andesite and 0.56 MPa√m for marble) and the cracked chevron notched Brazilian disc method tests (1.45 MPa√m for andesite and 1.08 MPa√m for marble), proper geometrical parameters were investigated by changing diameter, central-hole diameter, and loading angle of Ankara andesite and Afyon marble specimens. Semicircular bending method results were lower than the cracked chevron notched Brazilian disc method results. With flattened Brazilian disc method, the closest results (1.45 MPa√m for andesite and 1.12 MPa√m for marble) to the suggested method was obtained by 54 mm diameter discs with loading angles between 32.5° and 38.0° and with thicknesses between 19 mm and 34 mm. With modified ring test on andesite, the closest results to the suggested method was obtained by 75 mm diameter discs with 8 mm central-hole diameter and 25° loading angle (1.47 MPa√m for andesite and 1.07 MPa√m for marble), and with 14 mm central-hole diameter and 16° loading angle (1.50 MPa√m for andesite and 1.05 MPa√m for marble).
Mining engineering.
http://etd.lib.metu.edu.tr/upload/12611985/index.pdf
https://hdl.handle.net/11511/19779
Graduate School of Natural and Applied Sciences, Thesis

Suggestions

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 ...
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...
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...
Computer modeling of the initial cavern for Beypazari Trona ore on the basis of leaching rates, insoluble contents and thickness of trona layer
Tunçay Saygun, İlkay; Arol, Ali İhsan; Department of Mining Engineering (2008)
Trona ore located in Beypazarı is extracted by solution mining method with well pair connected by directional drilling technology. This thesis covers the determination of the dimensions of the initial (vertical) caverns formed in underground by use of a computer modeling (trademark: WinUbro/Poland) on the basis of horizontal and vertical leaching rates. The leaching rates were determined using the trona core samples from the ore deposit. The effect of insoluble content and the thickness of trona layer and s...
Citation Formats
Ç. Alkılıçgil, “Development of specimen geometries for mode i fracture toughness testing with disc type rock specimens,” Ph.D. - Doctoral Program, Middle East Technical University, 2010.
METU IIS - Integrated Information Service open@metu.edu.tr