Issue 48

C. Santus, Frattura ed Integrità Strutturale, 48 (2019) 442-450; DOI: 10.3221/IGF-ESIS.48.42 449 literature value k = 0.44, Fig. 7 (c). Consequently, the role of the normal stress is less weighty with respect to the shear stress amplitude. Finally, the maximum normal stress is negative for any orientation angle of the Deep Rolling test, shown in Fig. 8 (b). The SWT parameter cannot be calculated, and the orientation of the maximum normal stress amplitude is inward but not in agreement with the evidently more inclined cracks. The maximum of the FS parameter is less affected by the normal stress, and thus can be found in the negative angle region, still with k = 0.44, and in quite good agreement with the actual overall orientation of the cracks. C ONCLUSIONS ype I (shear) crack fretting fatigue initiation was experimentally observed with SEM visualizations of sectioned shrink-fit connection specimens with increased strength, both by lubricating the contact surface and with Deep Rolling. The prediction analysis of the initial crack orientation angle was proposed in the paper. Despite the apparent agreement between the inward crack orientation and the direction of maximum shear stress amplitude, concern was raised regarding the correct prediction of this or the other (outward) orthogonal orientation, which experiences a more tensile normal stress. The value of the Fatemi-Socie material parameter can drive the predicted direction inward or outward by controlling the effect of the maximum normal stress. On the other hand, a type II (tensile) crack was only observed for the fretting configuration with no surface preparation, which underwent a lower fretting load and thus less of contact pressure decrease during the tensile load cycle, which instead promoted type I shallow cracks. R EFERENCES [1] Baietto-Duborg, M.-C., Lindley, T. (2013). Fretting Fatigue: Modeling and Applications. Fatigue of Materials and Structures, Hoboken, NJ, USA, John Wiley & Sons, Inc., pp. 195–230. [2] Hills, D.A., Nowell, D. (1994). Mechanics of Fretting Fatique, vol. 30, Dordrecht, Springer Netherlands. [3] De Pauw, J., De Baets, P., De Waele, W. (2011). Review and Classification of Fretting Fatigue Test Rigs, Sustain. Constr. Des., 2, pp. 41–52. [4] Azevedo, C.R.F., Henriques, A.M.D., Pulino Filho, A.R., Ferreira, J.L.A., Araújo, J.A. (2009). Fretting fatigue in overhead conductors: Rig design and failure analysis of a Grosbeak aluminium cable steel reinforced conductor, Eng. Fail. Anal., 16(1), pp. 136–151, DOI: 10.1016/j.engfailanal.2008.01.003. [5] Santus, C. (2008). Fretting fatigue of aluminum alloy in contact with steel in oil drill pipe connections, modeling to interpret test results, Int. J. Fatigue, 30(4), pp. 677–688, DOI: 10.1016/j.ijfatigue.2007.05.006. [6] Swalla, D.R., Neu, R.W. (2001). Influence of coefficient of friction on fretting fatigue crack nucleation prediction, Tribol. Int., 34(7), pp. 493–503, DOI: 10.1016/S0301-679X(01)00048-2. [7] Mutoh, Y., Xu, J.-Q. (2003). Fracture mechanics approach to fretting fatigue and problems to be solved, Tribol. Int., 36(2), pp. 99–107, DOI: 10.1016/S0301-679X(02)00136-6. [8] Liu, K.K., Hill, M.R. (2009). The effects of laser peening and shot peening on fretting fatigue in Ti–6Al–4V coupons, Tribol. Int., 42(9), pp. 1250–1262, DOI: 10.1016/j.triboint.2009.04.005. [9] Szolwinski, M.P., Farris, T.N. (1998). Observation, analysis and prediction of fretting fatigue in 2024-T351 aluminum alloy, Wear, 221(1), pp. 24–36, DOI: 10.1016/S0043-1648(98)00264-6. [10] Muñoz, S., Navarro, C., Domínguez, J. (2007). Application of fracture mechanics to estimate fretting fatigue endurance curves, Eng. Fract. Mech., 74(14), pp. 2168–2186, DOI: 10.1016/j.engfracmech.2006.10.010. [11] Araújo, J.A., Castro, F.C. (2012). A comparative analysis between multiaxial stress and ΔK-based short crack arrest models in fretting fatigue, Eng. Fract. Mech., 93, pp. 34–47, DOI: 10.1016/j.engfracmech.2012.06.007. [12] Baietto, M.C., Pierres, E., Gravouil, A., Berthel, B., Fouvry, S., Trolle, B. (2013). Fretting fatigue crack growth simulation based on a combined experimental and XFEM strategy, Int. J. Fatigue, 47, pp. 31–43, DOI: 10.1016/j.ijfatigue.2012.07.007. [13] De Pauw, J., De Waele, W., Hojjati-Talemi, R., De Baets, P. (2014). On the use of digital image correlation for slip measurement during coupon scale fretting fatigue experiments, Int. J. Solids Struct., 51(18), pp. 3058–3066, DOI: 10.1016/j.ijsolstr.2014.05.002. [14] Hojjati-Talemi, R., Abdel Wahab, M., De Pauw, J., De Baets, P. (2014). Prediction of fretting fatigue crack initiation and propagation lifetime for cylindrical contact configuration, Tribol. Int., 76, pp. 73–91, T