Issue 48

D. Alexiane et alii, Frattura ed Integrità Strutturale, 48 (2019) 70-76; DOI: 10.3221/IGF-ESIS.48.09 75 This paper is a first attempt of the authors to investigate the relationship between the energy registered by acoustic emission and by thermographic technology [29, 30  , related to fatigue behavior under ultrasonic fatigue testing. Further investigation in this field are expected in the next future. C ONCLUSIONS he following conclusions may be drawn from the present work:  Ultrasonic fatigue tests are carried out on the granite rock, under the three point bending;  Ultrasonic loading is applied by an aluminum awl, which is calculated by finite element method to fit the resonance condition;  Higher temperature is observed by thermographic images at fracture;  Ultrasonic fatigue endurance of this granite prism follows the S-N curve in the narrow range of applied load: 15.5 to 19 MPa;  Fracture surfaces are perpendicular to the axe of specimens and present higher irregularities when the applied load increases;  Acoustic emission techniques are used to register the events during the ultrasonic fatigue tests on the granite, showing that four stages (phases) are present along the time of testing;  Acoustic emission and thermographic technology may be used to investigate the endurance under ultrasonic fatigue testing. A CKNOWLEDGEMENTS he authors express their special mention of gratitude to CONACYT (The National Council for Science and Technology, Mexico), for the financial support destined to this study by the program grant: CB- 241117- 2014. An additional mention of gratitude to the University of Michoacán in Mexico, for the received support in the development of this work. R EFERENCES [1] Li, H.B., Zhao, J., Li, T.J. (1999). Triaxial compression tests of a granite at different strain rates and confining pressures, Int. J. of Rocks Mech. and Min. Sci., 36(8), pp 1057-1063. DOI: 10.1016/S1365-1609(99)00120-3. [2] Zhou, T., Dong, S. L., Zhao, G. F., Zhang, R., Wu, S. Y., Zhu, J. B. (2018). An experimental study of fatigue behavior of granite under low-cycle repetitive compressive impacts, Rock Mech. and Rock Eng., 51(10), pp. 3157–3166. DOI: 10.1007/s00603-018-1515-0. [3] Basu, A., Mishra, D.A., Roychowdhury, K. (2013). Rock failure modes under uniaxial compression, Brazilian, and point load tests, Bull. of Eng. Geol. and the Env., 72(3-4), pp. 457–475. DOI: 10.1007/s10064-013-0505-4. [4] Oda, M., Katsube, T., Takemura, T. (2002). Microcrack evolution and brittle failure of Inada granite in triaxial compression tests at 140 MPa, J. of Geoph. Res., 107(B10), pp. ECV 9 1-17. DOI: 10.1029/2001JB000272. [5] Zhao, J., Li, H.B., Wu, M.B., Li, T.J. (1999). Dynamic uniaxial compression tests on a granite, Int. J. of Rocks Mech. and Min. Sci., 36(2), pp. 273-277. DOI: 10.1016/S0148-9062(99)00008-X. [6] Li, H.B., Zhao, J., Li, T.J. (2000). Micromechanical modelling of the mechanical properties of a granite under dynamic uniaxial compressive loads, Int. J. of Rocks Mech. and Mining Sci., 37(6), pp. 923-935. DOI: 10.1016/S1365-1609(00)00025-3. [7] Sun, J., Hu, Y.Y. (1997). Time-dependent effects on the tensile strength of saturated granite at Three Gorges Project in China, Int. J. of Rocks Mech. and Min. Sci., 34(3-4), pp. 306.e1-306.e13, DOI: 10.1016/S1365-1609(97)00222-0. [8] Noor-E-Khuda, S., Albermani, F., Veidt, M. (2017). Flexural strength of weathered granites: Influence of freeze and thaw cycles, Const. and Build. Materials, 156, pp. 891-901. DOI: 10.1016/j.conbuildmat.2017.09.049. [9] Dai, F., Xia, K. (2010). Loading rate dependence of tensile strength anisotropy of barre granite, Pure and Appl. Geophysics, 167(11), pp. 1419–1432. DOI: 10.1007/s00024-010-0103-3}. T T