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Rayleigh waves in generalized continua
In this thesis we consider wave propagation phenomena in generalized continuum models. The classical linear continuum theory is inadequate to explain new effects of microstructural motion; for example, in an unbounded elastic medium, the propagation of plane waves is non-dispersive. On the contrary, experiments with real solids show that waves propagation is dispersive, i.e., the wave speed is depending on the frequency. To incorporate better the microstructure of the matter into the classical theory, generalized continuum models may be employed. The higher gradient elasticity theories and micromorprhic models are the most familiar models. The mechanical behaviour of isotropic Eringen-Mindlin micromorphic media is generally defined by means of 18 elastic constants. However, the huge set of parameters cannot unveil the main characteristics of the micromorphic media due to inevitable computational difficulties. To counter this situation, Neff recently presented the relaxed micromorphic model, featuring six parameters and having the capability to characterize the crucial feature of the micromorphic continua comprehensively. It is a well-documented fact that the relaxed micromorphic model includes various classical models as special cases, e.g., the microstretch model, the linear Cosserat model, microvoids model and the classical linear model. Traveling waves can exist within a small depth from a free surface of an elastic continuum, while the bulk of the continuum remains almost at rest. Such waves are called Rayleigh waves, named after the English physicist Lord Rayleigh, who carried out pioneering work in studies of wave propagations in isotropic elastic media. The studies of Rayleigh waves captivated the attention of many scientists owing to its industrial application such as material characterization, nondestructive evaluation, acoustic microscopy and geophysical exploration. These waves are also employed to detect cracks and other defects in the material. Recently, Mielke and Fu have devised a new method to ...
Rayleigh waves in generalized continua
In this thesis we consider wave propagation phenomena in generalized continuum models. The classical linear continuum theory is inadequate to explain new effects of microstructural motion; for example, in an unbounded elastic medium, the propagation of plane waves is non-dispersive. On the contrary, experiments with real solids show that waves propagation is dispersive, i.e., the wave speed is depending on the frequency. To incorporate better the microstructure of the matter into the classical theory, generalized continuum models may be employed. The higher gradient elasticity theories and micromorprhic models are the most familiar models. The mechanical behaviour of isotropic Eringen-Mindlin micromorphic media is generally defined by means of 18 elastic constants. However, the huge set of parameters cannot unveil the main characteristics of the micromorphic media due to inevitable computational difficulties. To counter this situation, Neff recently presented the relaxed micromorphic model, featuring six parameters and having the capability to characterize the crucial feature of the micromorphic continua comprehensively. It is a well-documented fact that the relaxed micromorphic model includes various classical models as special cases, e.g., the microstretch model, the linear Cosserat model, microvoids model and the classical linear model. Traveling waves can exist within a small depth from a free surface of an elastic continuum, while the bulk of the continuum remains almost at rest. Such waves are called Rayleigh waves, named after the English physicist Lord Rayleigh, who carried out pioneering work in studies of wave propagations in isotropic elastic media. The studies of Rayleigh waves captivated the attention of many scientists owing to its industrial application such as material characterization, nondestructive evaluation, acoustic microscopy and geophysical exploration. These waves are also employed to detect cracks and other defects in the material. Recently, Mielke and Fu have devised a new method to ...
Rayleigh waves in generalized continua
Khan, Hassam (author) / Neff, Patrizio
2022-02-22
Theses
Electronic Resource
English
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