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

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2008
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.

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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.