Issue 49

H. Chbani et alii, Frattura ed Integrità Strutturale, 49 (2019) 763-774; DOI: 10.3221/IGF-ESIS.49.68 773  The load / CMOD curve is a useful and effective technique for determining the length propagated crack during loading, thus the R curve plot with good accuracy.  The R curves give almost the same K IC and the same maximum crack length for the various notch lengths.  Our study confirms that the R curve is unique and independent of the notch length, this curve represents an intrinsic parameter of concrete material, it allows to determine the critical stress intensity factor and to describe the crack evolution in quasi-fragile materials cases, so the R curve is a mechanical characteristic. N OMENCLATURE a a 0 a C B E W S L SENB CMOD CMODc P P max crack length notch length critical crack length specimen thickness young’s modulus specimen width distance between supports specimen length specimen for three-point bending crack mouth opening displacement critical crack mouth opening displacement applied load maximal load σ N K R FPZ Δa Δa c Δa max α 0 α α c α max K I K IC nominal stress R-curve in function of stress intensity factor fracture process zone crack extension critical crack extension maximal crack extension α 0 = a 0 /W initial crack length ratio α= (a 0 +Δa)/W crack extension ratio α c = (a 0 +Δa c )/W critical crack extension ratio α max = (a 0 +Δa max )/W maximal crack extension ratio stress intensity factor in mode I critical stress intensity factor in mode I R EFERENCES [1] Sanz, G. (1974). La rupture des aciers – Première partie : la rupture fragile – Collection IRSID-OTUA. [2] Funari, M.F., Greco, F., Lonetti, P., Luciano, R., Penna, R. (2018) An interface approach based on moving mesh and cohesive modeling in Z-pinned composite laminates. Composites Part B: Engineering; 135, pp. 207-217, DOI: 10.1016/j.compositesb.2017.10.018. [3] Funari, M.F., Lonetti, P., Spadea, S. (2019) A crack growth strategy based on moving mesh method and fracture mechanics. Theoretical and Applied Fracture Mechanics; 102, pp. 103-115, DOI: 10.1016/j.tafmec.2019.03.007. [4] Funari, M.F., Greco, F., Lonetti, P. (2019) A numerical model based on ALE formulation to predict crack propagation in sandwich structures. Frattura ed Integrità Strutturale, 47, pp. 277-293. DOI: 10.3221/igf-esis.47.21. [5] Broek, D. (1984). Elementary engineering fracture mechanics. Boston: Kluwer Academic Publisher [6] Broek, D. (1988).The practical use of fracture mechanics. Boston: Kluwer Academic Publisher [7] Zhu, X.-K., Joyce, J.A. (2012) Review of fracture toughness (G, K, J, CTOD, CTOA) testing and standardization. Engng. Fract. Mech. 85, pp. 1–46. , DOI: 10.1016/j.engfracmech.2012.02.001. [8] Kailer, A. Marc, S. (2016). On the feasibility of the Chevron Notch Beam method to measure fracture toughness of fine-grained zirconia ceramics. 32(10), pp. 1256-1262 , DOI: 10.1016/j.dental.2016.07.011. [9] Graziani, L. (2014). Measurement of R-curve in clay brick blocks using optical measuring technique, Engineering fracture mechanics, 121, pp. 1-10. DOI: 10.1016/j.engfracmech.2014.04.007. [10] Yanhua, Z., Jianmei, C., Hangab, H.G. (2015). A three-parameter R-curve of concrete-like quasi-brittle materials, Construction and Building Materials. 78(1), pp. 243-249. DOI: 10.1016/j.conbuildmat.2015.01.029. [11] Alam, M.R. (2010). Fracture toughness of plain concrete specimens made with industry-brunt brick aggregates. 38(1), pp. 81-94. [12] Kumar, S., Rajendra, K.C. (2015). Further observations on the three-parameter R-curve of concrete-like quasi-brittle materials, Construction and Building Materials, 93, pp. 857-868. DOI: 10.1016/j.conbuildmat.2015.05.079. [13] Ferreiraa, L.E.T. Bittencourt, T.N. Sousa, J..L.A.O . Gettu.R. (2002). R-curve behavior in notched beam tests of rocks, Engineering Fracture Mechanics.69(17): 1845-1852 , DOI: 10.1016/S0013-7944(02)00064-4 [14] Jisun, C., Goangseup, Z., Shinichi, H., Kohei, Y., Soye, K. (2014). Influence of fiber reinforcement on strength and toughness of all-lightweight concrete, Construction and Building Materials. 69, pp. 381-389 DOI: 10.1016/j.conbuildmat.2014.07.074.