On elasto-acoustics of buried and submerged shell structures

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Bahari, Ako
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Comprehensive elastoacoustics investigation of submerged and buried shell structures is the main objective. Analyses are carried out in frequency and time domains under a generalized loading condition and various material configurations for different constitutive rules. Major part of this study is performed analytically within the linear domain. The last chapter on cubature formulae, however, is a prelude to numerical analysis when nonlinearities of various types are introduced into the problem. Primarily, an exhaustive comparative study is carried out on the performance of the most popular shell theories in elastoacoustics modelling shell structures subjected to a transient excitation. These models approximate the exact local theory of linear elasticity. Consequently, a discontinuation in their application, under a general nonstationary excitation, is strongly recommended, henceforth. Subsequently the total responses are considered when a centrally symmetric excitation is applied. The corresponding numerical experiments convey practically significant implications. A more general situation for a buried shell structure, rather than a fluid submerged case, is considered next. The exact local theory of linear elasticity is applied to the both of elastic media whilst the linear acoustical theory for compressible fluids is utilized. Both of generalized traction forces and waves being incident upon a shell's either surfaces are considered as the excitation’s sources. Incident waves of shear and compressional nature are included. Origins of these sources are located within the encompassing elastic medium, shell's material or the contained fluid. Extensive sets of numerical examples are performed by using special visualization techniques after which different limiting situations are studied. A generalized Hook's law along with piezoelasticity for anisotropic materials, on the other hand, is considered subsequently for the shells submerged in an acoustical wedge medium rather than a full-space configuration. Analytical solutions are developed for linear domain in previous parts. The last chapter, however, is a prelude of numerical analysis dealing with nonlinearities associated with the kinematics of finite deformation or constitutive rule such as elasto-plasticity, super-elasticity or discontinuities due to a strong shock. Quadrature formulae are presented and implemented. These integration schemes can be used within a mixed finite element framework or a meshless approach.
Transient diffraction of elastic and acoustical waves, Shell theories, Focusing mechanism, Cavitation, Method of images, Addition theorems, Acoustical wedge, Composites, Anisotropy, Layered structures, Triclinic, spherical incident waves, Piezoelasticity, Generalized Hooke’s law, Quadrature integration, Cubature formulae, Degree of exactness, Computational complexity, Meshless method
Bahari, A., & Popplewell, N. (2015). Comment on “Transient response of an acoustic medium by an excited submerged spherical shell”[J. Acoust. Soc. Am. 109 (6), 2789–2796 (2001)]. The Journal of the Acoustical Society of America, 137(5), 2966-2969.
Bahari, A., Lefeuve-Mesgouez, G., Mesgouez, A., & Popplewell, N. (2016). Transient Response of a Fluid-Filled, Thick-Walled Spherical Shell Embedded in an Elastic Medium. In E3S Web of Conferences (Vol. 12, p. 06004). EDP Sciences.