A Dynamic CCNBD Method for Measuring Dynamic Fracture Parameters
The cracked chevron notch Brazilian disc (CCNBD) method is widely used in characterizing static rock fracture toughness. We explore here the possibility of extending the CCNBD method to characterizing the dynamic fracture parameters of rocks. The relevant fracture parameters are the initiation fracture toughness, fracture energy, propagation toughness, and fracture velocity. The dynamic load is applied with a split Hopkinson pressure bar (SHPB) apparatus. A strain gauge is mounted on the sample surface near the notch tip to detect the fracture-induced strain release on the sample surface, and a laser gap gauge (LGG) is used to monitor the crack surface opening distance (CSOD) during the test. With dynamic force balance achieved in the tests, the stableunstable transition of the crack propagation crack is observed and the initiation fracture toughness is obtained from the peak load. The dynamic fracture initiation toughness values obtained for the chosen rock (Laurentian granite) using this method are consistent with those reported in the literature. The fracture energy, propagation toughness and the fracture velocity are deduced using an approach based on energy conservation.
KeywordsStress Intensity Factor Dynamic Fracture Toughness Critical Crack Length Initiation Fracture Toughness Crack Chevron Notch Brazilian Disc
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- 1.Ouchterlony F. "Suggested methods for determining the fracture toughness of rock", International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts 25(2): 71-96 (1988).Google Scholar
- 14.Bertram A., Kalthoff J. F.,"Crack propagation toughness of rock for the range of low to very high crack speeds", in Advances in Fracture and Damage Mechanics Key engineering materials, Trans Tech Publications, Uetikon-Zurich, Vol. 251-252, pp. 423-430, (2003).Google Scholar
- 18.Kolsky H. "An investigation of the mechanical properties of materials at very high rates of loading", Proceedings of the Royal Society A-Mathematical Physical and Engineering Sciences B62: 676-700 (1949).Google Scholar
- 19.Kolsky H. "Stress waves in solids", Clarendon Press, Oxford, pp. 212 (1953).Google Scholar
- 21.Dai F., Xia K. W., Luo S. N. "Semi-circular bend testing with split Hopkinson pressure bar for measuring dynamic tensile strength of brittle solids", Review of Scientific Instruments 79(12) (2008).Google Scholar
- 23.Iqbal N., Mohanty B. "Experimental calibration of stress intensity factors of the ISRM suggested cracked chevron-notched Brazilian disc specimen used for determination of mode-I fracture toughness", International Journal of Rock Mechanics and Mining Sciences 43(8): 1270-1276 (2006).CrossRefGoogle Scholar
- 25.ANSYS Inc. Advanced Analysis Techniques Guide (1999).Google Scholar