Papers by Author: Li Li Tong

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Authors: Fathallah Elsayed, Li Li Tong, Hui Qi, Mahmoud Helal
Abstract: Predicting the dynamic response of a floating and submerged structure subjected to underwater explosion is greatly complicated by the explosion of a high explosive, propagation of shock wave, bubble-pulse, complex fluid-structure interaction phenomena and the dynamic behavior of the floating structures. A numerical simulation has been carried out to examine the behavior of elliptical submersible pressure hull to non-contact underwater explosion (UNDEX) and take the effect of bubble-pulse. The finite element package ABAQUS was used to model the UNDEX and the fluid-structure interaction (FSI) phenomena. The pressure wave resulting from an UNDEX was assumed to be a spherical wave. Plastic strain and the time histories of the wet-surface displacement, velocity and von Mises stress are presented. The analytical results are valuable for designing underwater vehicles to resist UNDEX.
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Authors: Fathallah Elsayed, Hui Qi, Li Li Tong, Mahmoud Helal
Abstract: Due to the wide range of variables involved and sophisticated analysis techniques required, optimum structural design of composite submersible pressure hull is known to be a challenge for designers. The major challenge involved in the coupled design problem is to handle multiple conflicting objectives. The problem with its proper consideration through multi-objective optimization is studied in this paper. Minimize the buoyancy factor and maximize buckling load capacity of the submersible pressure hull under hydrostatic pressure is considered as the objective function to reach the operating depth equal to 6000m. Finite element analysis of composite elliptical submersible pressure hull is performed using ANSYS parametric design language (APDL). The constraints based on the failure strength of the hulls are considered. The fiber orientation angles and the thickness in each layer, the radii of the ellipse, the ring beams and the stringers dimensions are taken as design variables. Additionally, a sensitivity analysis is performed to study the influence of the design variables up on objectives and constraints functions. Results of this study provide a valuable reference for designers of composite underwater vehicles.
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Authors: Li Li Tong, Zhen Qing Wang, Bao Hua Sun
Abstract: Numerical simulation for unidirectional hoop composite laminates under flexural loads was finished. The change of tensile and compressive stresses, the position of local crush and delamination and stiffness degradation were analyzed with parametric program compiled by APDL language in ANSYS. The results showed that composite laminate could bear the load continually after local crush and delamination. Displacements of calculated result with stiffness degradation model matched test results well.
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Authors: Fathallah Elsayed, Hui Qi, Li Li Tong, Mahmoud Helal
Abstract: The dynamic response of a floating structure subjected to underwater explosion is greatly complicated by the explosion of a high explosive, propagation of shock wave, complex fluid–structure interaction phenomena, and the dynamic behavior of the floating structures. A numerical investigation has been carried out to examine the behavior of stiffened steel plates subjected to shock loads resulting from an Underwater Explosion (UNDEX). The aim of this work is to obtain the optimal configuration to resist underwater shock loading. A non-linear dynamic numerical analysis of the underwater explosion phenomena associated with different geometrical stiffened steel plates is performed using the ABAQUS/Explicit finite element program. Special emphasis is focused on the evolution of mid-point displacements. Further investigations have been performed to study the effect of including material damping and the rate-dependant material properties at different shock loads. The results indicate that stiffener configurations and shock loads affect greatly the overall performance of steel plates and sensitive to the material data.
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Authors: Fathallah Elsayed, Hui Qi, Li Li Tong, Mahmoud Helal
Abstract: Recently, submersible pressure hulls with fiber-reinforced multilayer constructions have been developed as substitutes for classical metallic ring-stiffened pressure hulls. The strength and stability is its top priority. In this paper, the optimum design of elliptical composite deep-submerged pressure hull under hydrostatic pressure is investigated based on the finite element analysis to minimize the buoyancy factor of the submersible pressure hull according to the design requirements. Minimize the buoyancy factor of a submarine pressure hull under hydrostatic pressure is proposed as an objective function and the constraints based on the failure strength and the buckling strength of the hulls are considered. The thickness and the fiber orientation angles in each layer, the radii of the ellipse, the stringers dimensions and the operating depth are taken as design variables. Additionally, a sensitivity analysis is performed to study the influence of the design variables up on the Tsai-Wu failure. Results of this study provide a valuable reference for designers of composite underwater vehicles.
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Authors: Fathallah Elsayed, Hui Qi, Li Li Tong, Mahmoud Helal
Abstract: Geometric configurations such as hull shape, shell thickness, stiffener layout, and type of materials are the key factors influencing the structural performance of pressure hulls. The aim of this study is to maximize the structural efficiency of elliptical deep-submerged pressure hull under hydrostatic pressure. Minimize the buoyancy factor of a submarine pressure hull under hydrostatic pressure was proposed as an objective function for both composite and steel models. The thickness and the orientation angle of each layer, the radii of the ellipse and the operating depth are taken as design variables. Also, the shell buckling strength and the angle-ply laminated failure strength are considered in the case of composite model. In the other hand, the shell thickness, the radii of the ellipse, the stiffeners offsets, the stiffeners dimensions, and the operating depth, are selected as design variables for steel model with shell buckling and materials yielding constraints. The analysis is performed using commercial finite element analysis software ANSYS. Additionally, a sensitivity analysis is performed to study the influence of the design variables on the structural optimum design. Results of this study provide a valuable reference for designers of underwater vehicles.
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Authors: Li Li Tong, Zhen Qing Wang, S.H. Chen, Bao Hua Sun
Abstract: The progressive failure analysis of composite pressure vessel under hydrostatic pressure has been carried out. The composite pressure vessel has been modeled by using layer structural shell element. After the failure of the weakest ply, the stiffness is reduced by either fiber failure or matrix failure. The stiffness of failed element has been totally discarded and other element are considered to remain unchanged after the weakest ply failure. The stress of the laminate at the same point is evaluated again to see if the laminate can carry additional load. This ply-by-ply analysis progresses until the ultimate strength of the pressure vessels is reached. A parametric study has been done on the progressive failure analysis.
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