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Computational study of nonlinear thermoelastic behavior in axisymmetric plates under rapid cooling Babaee, Alireza


In this thesis, a comprehensive computational study is presented on the nonlinear thermoelastic behavior of axisymmetric plates subjected to low-temperature and cryogenic thermal loading conditions. This research addresses a gap in existing literature by exploring the effects of such thermal loads, which are particularly relevant for engineering components, such as ship decks that may come into contact with liquefied natural gas (LNG) spills. This thesis aims to improve understanding of flexural structures thermoelastic behavior under extreme thermal conditions, providing insights for their safe design and operation in cryogenic environments. Theoretical models are developed in this thesis to investigate the nonlinear transient and dynamic thermoelastic response of axisymmetric plates when subjected to sudden low-temperature and cryogenic loads. The plates are made of 304 grade stainless steel (SUS 304), low-carbon steel (AISI 1020) or a functionally graded composite with properties graded through the thickness direction. These plates are modeled using first-order shear deformation theory (FSDT), incorporating von Kármán geometrical nonlinearity. To solve the governing equations, the Generalized Differential Quadrature Method (GDQM), Newmark and Newton-Raphson techniques are employed. Additionally, a transient Fourier heat transfer equation is applied to assess temperature distribution over time, employing both GDQM and the Crank-Nicolson method. The research findings reveal that the transient thermoelastic response of plates to sudden cryogenic cooling can significantly differ from steady-state responses, resulting in substantial deflections and stresses within a very short timeframe. Also, the results provide a novel comparison of large amplitude thermally induced vibration (TIV) between rapid cooling and heating thermal shocks. This reveals that the importance of the inertia effect is greater under sudden cooling than under sudden heating, for the same thermal load magnitude. Additionally, the study addresses localized thermal loading to effectively model cryogenic spills, subsequently exploring the transient thermoelastic response of plates under these conditions. It employs a two-dimensional transient heat conduction equation to capture the effects of localized cooling. The findings underscore the impact of localized thermal loads, demonstrating that even minor localized cooling can cause significant stress, especially at the intersection of thermally affected and unaffected zones.

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