چكيده به لاتين
Vibration-induced noise is one of the unwanted phenomena that needs to be controlled and reduced in rolling stock systems. One of the most important research fields in railway industry, especially in high-speed trains, deals with studying the attenuation mechanisms of enegy caused by vibration-induced noise in the train structure. In numerous instances, the noise-inducing loads are applied in short periods of time and at high rates which lead to the propagation of elastic stress waves in the carbody structure. In order to study the energy attenuation mechanisms in the structure, two main approaches can be suggested: the first approach studies the energy attenution at the macro-scale which includes analyses in the actual catbody dimensions. The other one deals with micro- or nano-scale studies of energy attenuation mechanism which considers the wave propagation analysis in the structure and its attenuation due to damping properties of the carbody material.
This research aims to investigate the capabilities of nanocomposite materials in attenuating the two dimensional elastic stress waves in them using a nano-scale analytical approach. Two main sources of wave energy attenuation are discussed: attenuation due to wave scattering by nanofibers and attenuation due to viscoelastic properties of the material. Throughout this study, several important parameters affecting the propagation and attenuation processes are studied in detail, such as: surface elasticity, homogeneity or inhomogeneity of the interphase region, interfacial layer thickness, multiple scattering effects, etc. Several parameters reflecting upon the propagation and attenuation of the waves (including dynamic stress concentration, scattering cross section, phase velocity and attenuation) are calculated and interpreted to gain an insight regarding the problem at hand. As a main application of the findings of this research, one can refer to the design of noise dampers in the high-speed trains.
