Issue 43

P. Zampieri et alii, Frattura ed Integrità Strutturale, 43 (2018) 191-204; DOI: 10.3221/IGF-ESIS.43.15 195 The inertia properties are automatically considered in the developed model by introducing the density in the material properties. The multibody model (Fig. 4.a) has been developed in order to reproduce the landing gear schematically shown in Fig. 4.b. According to Fig. 4.b, the model is characterized by two tyres, two wheels, a wheel axle, a shock absorber, a main fitting, a trailing arm, an actuating cylinder, an upper folding side brace and a lower folding side brace. Different joint types have been introduced in the model: revolute joints, allowing the motion between the trailing arm, the main fitting and the shock absorber (Fig. 4.b); revolute joints modelled between the folding side brace, the main fitting and the support fixture (not visible in Fig. 4 - modelled at the left end of the upper folding slide brace) (Fig. 5.a); prismatic joints, allowing the sliding between the piston and the cylinder tube of the shock absorber. a) b) Figure 5 : Revolute joints between: a) main fitting and the support fixture; b) main fitting, trailing arm and shock absorber. The considered loading conditions are characterized by two vertical forces of 78800 N applied to the wheels, by assuming a shock absorber stroke of 75% of total mechanical stroke. The results, in terms of reaction forces, have been compared with those achieved by the stick model under the same loading conditions. Tabs. 2.a and 2.b show the reaction forces achieved by the multibody and the stick (FE) model, respectively. a) Node 52 b) Node 52 Rx Ry Rz Mx My Mz Rx Ry Rz Mx My Mz [N] [N] [N] [Nmm] [Nmm] [Nmm] [N] [N] [N] [Nmm] [Nmm] [Nmm] 25293 3453 -16000.3 0 0 0 25290 3463 -16000 0 0 0 Node 55 Node 55 Rx Ry Rz Mx My Mz Rx Ry Rz Mx My Mz [N] [N] [N] [Nmm] [Nmm] [Nmm] [N] [N] [N] [Nmm] [Nmm] [Nmm] 17395 -261989 54479 0 0 0 17390 -262000 54490 0 0 0 Node 66 Node 66 Rx Ry Rz Mx My Mz Rx Ry Rz Mx My Mz [N] [N] [N] [Nmm] [Nmm] [Nmm] [N] [N] [N] [Nmm] [Nmm] [Nmm] -42688 258536 -52077 0 0 0 -42690 258500 -52080 0 0 0 Table 2 : Reaction forces achieved for the main landing gear by the a) multibody and b) stick models. According to Tabs. 2.a and 2.b, a good agreement has been achieved.