Issue 42

A. Campagnolo et alii, Frattura ed Integrità Strutturale, 42 (2017) 181-188; DOI: 10.3221/IGF-ESIS.42.19 187 The experimental results relevant to the PMMA V-notched components are shown in Fig. 3 in terms of the critical NSIF K 2 c , along with the theoretical predictions based on the fracture approaches under consideration. It can be observed from Fig. 3 that the agreement between theoretical predictions and experimental results, in terms of critical Mode II NSIF K 2 c , is very good for all considered criteria. Some recent developments dealing with creep stresses are reported in [25]. C ONCLUSIONS hree different fracture criteria for brittle and quasi-brittle materials weakened by sharp V-notches have been considered in the present contribution. The attention has been focused on in-plane shear loading conditions (Mode II). The averaged strain energy density (SED) criterion and two different formulations of the Finite Fracture Mechanics (FFM) theory, according to Leguillon et al. and to Carpinteri et al. respectively, have been accurately compared. With reference to the criterion based on the averaged SED, a new expression for estimating the control radius R c under pure Mode II loading has been proposed. First, the criteria have been compared analytically by providing the expressions of the critical value of the Notch Stress Intensity Factor K 2 c . The same proportionality relation has been found to exist between K 2 c and two key material properties: the Mode I fracture toughness K Ic and the ultimate tensile stress σ c . The only difference between the analysed criteria is represented by the proportionality factor. Finally, the approaches taken into consideration in the present contribution have been adopted for the fracture assessment of brittle V-notched components subjected to pure Mode II loading. This has allowed to investigate the assessment capability of each approach under in-plane shear loading. A set of experimental data reported in the literature has been employed for the comparison. The agreement between experimental data and theoretical predictions has been found very good for all criteria considered in the present investigation. R EFERENCES [1] Berto, F., Local approaches for the fracture assessment of notched components: The research work developed by Professor Paolo Lazzarin, Frattura ed Integrita Strutturale, 9(34) (2015) 11-26. [2] Knesl, Z., A criterion of V-notch stability, Int. J. Fract., 48 (1991) R79–R83. [3] Seweryn, A., Brittle fracture criterion for structures with sharp notches, Eng. Fract. Mech., 47 (1994) 673–681. [4] Lazzarin, P., Campagnolo, A., Berto, F., A comparison among some recent energy- and stress-based criteria for the fracture assessment of sharp V-notched components under Mode I loading, Theor. Appl. Fract. Mech., 71 (2014) 21– 30. [5] Lazzarin, P., Zambardi, R., A finite-volume-energy based approach to predict the static and fatigue behavior of components with sharp V-shaped notches, Int. J. Fract., 112 (2001) 275–298. [6] Leguillon, D., A criterion for crack nucleation at a notch in homogeneous materials, C. R. Acad. Sci. II B, 329 (2001) 97-102. [7] Leguillon, D., Strength or toughness? A criterion for crack onset at a notch, Eur. J. Mech. A Solids, 21 (2002) 61–72. [8] Carpinteri, A., Cornetti, P., Pugno, N., Sapora, A., Taylor, D., A finite fracture mechanics approach to structures with sharp V-notches, Eng. Fract. Mech., 75 (2008) 1736–1752. [9] Sapora, A., Cornetti, P., Carpinteri, A., A Finite Fracture Mechanics approach to V-notched elements subjected to mixed-mode loading, Eng. Fract. Mech., 97 (2013) 216–226. [10] Sapora, A., Cornetti, P., Carpinteri, A., V-notched elements under mode II loading conditions, Struct. Eng. Mech., 49 (2014) 499–508. [11] Yosibash, Z., Priel, E., Leguillon, D., A failure criterion for brittle elastic materials under mixed-mode loading, Int. J. Fract., 141 (2006) 291–312. [12] Berto, F., Ayatollahi, M.R., Fracture assessment of Brazilian disc specimens weakened by blunt V-notches under mixed mode loading by means of local energy, Mater. Des., 32 (5) (2011) 2858-2869. [13] Radaj, D., Berto, F., Lazzarin, P., Local fatigue strength parameters for welded joints based on strain energy density with inclusion of small-size notches, Eng. Fract. Mech., 76 (8) (2009) 1109-1130. [14] Lazzarin, P., Berto, F., Zappalorto, M., Rapid calculations of notch stress intensity factors based on averaged strain energy density from coarse meshes: Theoretical bases and applications, Int. J. Fatigue, 32 (2010) 1559–1567. T