Issue 35

R. Sepe et alii, Frattura ed Integrità Strutturale, 35 (2015) 534-550; DOI: 10.3221/IGF-ESIS.35.59 549 C ONCLUSIONS he development of reliable methods to predict the damage tolerant behaviour is helpful for the designer to achieve more and more efficient structures. In this work static and fatigue tests on a full scale fuselage panel were carried out. After 177˙000 cycles the panel broke down at the middle-lower bay, near the third frame. The experimental results were useful in the assessment of the accuracy of the numerical FE model when determining the critical area. With reference to the static test, the correlation between numerical and experimental results is judged satisfactory, because the strain differences are comparable to the intrinsic error level inherent the strain gauge usage for most of strain gauges; numerical higher errors are expected in those zones where the allowance for geometry and stress field complexity is not provided due to the simplifications related to the two dimensional numerical approach. The results of the numerical analyses are in good agreement with the experimental analysis data collected by the tests on the full scale panel: the latter broke due to fatigue after 177˙000 cycles, while the model had predicted the initiation of the fatigue crisis at about 100˙000 cycles. At 177˙000 cycles the difference between numerical evaluation of the critical fatigue load and experimental data may be determined in terms of 3.3%. The position of the failure is predicted approximately in the same zone, located on the skin. Overall, these results show that the Sines criterion can be an effective method to rapidly evaluate the initiation of fatigue crisis. The method hereby proposed has the additional advantage of providing, with a single analysis, a description that is both qualitative and quantitative of the fatigue status of the structure. A rather good correlation was obtained between numerical results and experimental data in static loading conditions. R EFERENCES [1] Molent, L., Barter, S.A., A comparison of crack growth behaviour in several full-scale airframe fatigue tests, Int. J. Fatigue, 29 (6) (2007) 1090-1099. [2] Wang, S.S., Chu, R.C., Full scale fatigue crack growth test of advanced jet trainer AT-3, Theor. Appl. Fract. Mec., 11 (2) (1989) 71-91. [3] Sepe, R., Armentani, E., Caputo, F., Lamanna, G., Fatigue behaviour of full scale flat stiffened aeronautic panels, Key. Eng. Mat., 627 (2015) 97-100. [4] Giglio, M., Manes, A., Crack propagation on helicopter panel: Experimental test and analysis, Eng. Fracture Mechanics, 75 (3-4) (2008) 866-879. [5] Armentani, E., Citarella, R., Sepe, R., FML Full Scale Aeronautic Panel Under Multiaxial Fatigue: Experimental Test and DBEM Simulation, Eng. Fract. Mech., 78 (8) (2011) 1717-1728. [6] Cordes, J.A., Predicting the fatigue cycles on aluminum panels, Int. J. Fatigue, 23 (1) (2001) 5-12. [7] Grbovic, A., Rasuo, B., FEM based fatigue crack growth predictions for spar of light aircraft under variable amplitude loading, Eng. Fail. Anal., 26 (2012) 50-64. [8] Šedek, J., Růžek, R., Raška, J., Bĕhal, J., Comparative study of prediction methods for fatigue life evaluation of an integral skin-stringer panel under variable amplitude loading, Procedia Eng., 114 ( 2015 ) 124-131. [9] Furukawa, C.H., Bucalem, M.L., Mazella, I.J.G., On the finite element modeling of fatigue crack growth in pressurized cylindrical shells, Int. J. Fatigue, 31 (4) (2009) 629-635. [10] Citarella, R., Perrella, M., Multiple surface crack propagation: numerical simulations and experimental tests, Fatigue Fract. Eng. M., 28 (2005), 135-148. [11] Citarella, R., Cricrì, G., A two-parameter model for crack growth simulation by combined FEM-DBEM approach, Adv. Eng. Softw., 40 (5) (2009) 363-377. [12] Sepe, R., Armentani, E., Di Lascio, P., Citarella, R., Crack Growth Behavior of Welded Stiffened Panel, Procedia Engineering, 109 (2015) 473-483. [13] Citarella, R., Non Linear MSD crack growth by DBEM for a riveted aeronautic reinforcement, Adv. Eng. Softw., 40 (4) (2009) 253-259. [14] Citarella, R., MSD Crack propagation on a repaired aeronautic panel by DBEM, Adv. Eng. Softw., 42 (10) (2011) 887-901. [15] Armentani, E., Citarella, R., DBEM and FEM analysis on non-linear multiple crack propagation in an aeronautic doubler-skin assembly, Int. J. Fatigue, 28 (5-6) (2006) 598–608. [16] Romeo, G., Frulla, G., Buckling of simply supported and clamped anisotropic plates under combined loads, Spacecraft Structure and Mechanical Testing, Noordwijk, The Netherlands, (1991). T