Tensile mode fracture toughness experiments on andesite rock using disc and semi-disc bend geometries with varying loading spans


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Tutluoglu L., Karatas Batan C. , Aliha M.

Theoretical and Applied Fracture Mechanics, vol.119, 2022 (Journal Indexed in SCI Expanded) identifier

  • Publication Type: Article / Article
  • Volume: 119
  • Publication Date: 2022
  • Doi Number: 10.1016/j.tafmec.2022.103325
  • Title of Journal : Theoretical and Applied Fracture Mechanics
  • Keywords: Ankara andesite rock, Disc and semi-disc core-based specimens, Geometry and loading span effect, Maximum tangential strain criterion, Mode I fracture toughness, Three-Point bending

Abstract

© 2022 Elsevier LtdPurpose of this research is to investigate the effect of loading span on mode I fracture toughness for tests conducted by three-point bend geometries. Mode I fracture toughness tests were conducted on Ankara Golbasi Andesite with straight notched disc bending (SNDB) specimens of thicknesses 50 mm and 60 mm. Loading spans were varied in a wide range between 40 mm and 90 mm corresponding to span/radius ratios of S/R = 0.40 to 0.90. Three-point bend tests were conducted with the semi-circular bending (SCB) core specimen geometry for comparison purposes. Mode I fracture toughness results for tests with 60 mm and 50 mm thick SNDB specimens were about 30% greater than the results of SCB tests. It was found that mode I fracture toughness, KIc increases with decreasing the span length for both SNDB and SCB specimens. Mode I fracture toughness values was also increased with increasing the specimen thickness for the SNDB geometry. The differences in KIc results of different specimen geometries were explained by a mechanism employing maximum normal strain criterion. It was demonstrated that despite the dependency of critical stress intensity factor to the geometry and loading conditions of the tested specimen, the critical value of maximum tangential strain (εθθc) at the onset of fracture is a material constant and its value is nearly the same for all disc and semi-disc geometries tested with varying loading spans.