Issue 43

P. Zampieri et alii, Frattura ed Integrità Strutturale, 43 (2018) 191-204; DOI: 10.3221/IGF-ESIS.43.15 200 After the numerical tyre characterization, the entire landing gear has been constrained in order to reproduce the drop-test described by the EASA CS25 regulations. Such regulations define all test requirements, included the calculation of the equivalent airplane mass resting on the landing gear to be implemented during the test. The modelled mass assumes a value of 10800 kg and it has been added to the rigid wall. In order to get simpler the numerical simulation, as aforementioned, the landing gear has been fully constrained, whilst the rigid wall has been constrained in a way to allow the motion along the z-axis (Fig. 17), representing the gear drop axis. A drop velocity of 3.05 m/s has been applied to the rigid wall. Moreover, a rotational speed of 44.64 m/s has been applied to the wheels. A pitch angle of 0° has been considered. The dynamic simulation has been carried out by setting an analysis time of 450 ms, by leaving the estimation of the time increment to the software. However, in complex simulations, the time increment can reach values too small that increase sharply the computational costs. In order to avoid such problems, an artificial mass can be added to the model in a way that the whole model mass does not reach the 8÷9 %. Figure 17 : Landing gear model. Figure 18. Added mass curve.