SIMULATION OF NARROW GAUGE RAILWAY VEHICLES AND EXPERIMENTAL VALIDATION BY MEAN OF SCALED TESTS ON ROLLER RIG

The dynamic design of railway vehicles is often supported by numerical simulation performed by means of Multibody codes. Such methodology allows to define vehicle suspensions characteristics so as to meet running safety requirements and, in the case of passenger vehicles, to achieve an adequate comfort level. However, the effectiveness of the numerical model in the prediction of actual vehicle behavior may fall short of requirements if the model is not sufficiently accurate. Experimental validation can help to ensure reliability of the numerical models. In order to solve the problem, this work proposes to use experimental tests on scaled prototypes on roller-rig for preliminary validation of the numerical mode

Effect of microstructure on the mechanical and damping behaviour of dragonfly wing veins

Insect wing veins are biological composites of chitin and protein arranged in a complex lamellar configuration. Although these hierarchical structures are found in many 'venous wings' of insects, very little is known about their physical and mechanical characteristics. For the first time, we carried out a systematic comparative study to gain a better understanding of the influence of microstructure on the mechanical characteristics and damping behaviour of the veins. Morphological data have been used to develop a series of three-dimensional numerical models with different material properties and geometries. Finite-element analysis has been employed to simulate the mechanical response of the models under different loading conditions. The modelling strategy used in this study enabled us to determine the effects selectively induced by resilin, friction between layers, shape of the cross section, material composition and layered structure on the stiffness and damping characteristics of wing veins. Numerical simulations suggest that although the presence of the resilin-dominated endocuticle layer results in a much higher flexibility of wing veins, the dumbbell-shaped cross section increases their bending rigidity. Our study further shows that the rubber-like cuticle, friction between layers and material gradient-based design contribute to the higher damping capacity of veins. The results of this study can serve as a reference for the design of novel bioinspired composite structures.1123