Abstract
Fracture-toughness measurements were made on standard three-point-bend fracture specimens of Indiana limestone. Specimen dimensions, experimental techniques, and methods of data reduction were chosen to comply as closely as possible to the Tentative Method of Test for Plane Strain Fracture Toughness of Metallic Materials (ASTM Designation: E399-72T). Typical strain-gage-type clip-in displacement gages were found to lack the necessary sensitivity for measuring the crack-opening displacement while an LVDT displacement transducer having a linear range of ±0.25 mm (±0.010 in.) was found to be ideal.
Fatigue cracks were successfully introduced by repeated cycling to 85 percent of the fracture load. Load vs. crack opening-displacement records indicated that crack closure occurred in these tests. Effective crack lengths were determined using an experimental compliance calibration that was checked analytically. Final fracture was stable when using displacement control in a stiff load frame. Some size effects were noted, with toughness increasing with specimen size. Values ofK c, fracture toughness, were found to approach 990 kNm−3/2 (900\(psi\sqrt {in} \).) for the largest specimens.
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Work was supported by the U.S. Energy Research and Development Administration.
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Schmidt, R.A. Fracture-toughness testing of limestone. Experimental Mechanics 16, 161–167 (1976). https://doi.org/10.1007/BF02327993
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DOI: https://doi.org/10.1007/BF02327993