Elsayed Fathallah

Military Technical College

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Design Optimization of Composite Elliptical Deep-Submersible Pressure Hull for Minimizing the Buoyancy Factor

Advances in Mechanical Engineering (2014)

Elsayed Fathallah Hui Qi Lili Tong Mahmoud Helal

The design of deep submersible pressure hull's structural is one of the core technologies of submersible development of human history. Submersible pressure hulls with fiber-reinforced multilayer constructions have been developed in the recent years as substitutes for classical metallic ring-stiffened pressure hulls; strength and stability are its top priority. This paper investigates the optimum design of a composite elliptical deep-submerged pressure hull under hydrostatic pressure to minimize the buoyancy factor of the submersible pressure hull under constraints on the failure criteria and the buckling strength of the hulls to reach the maximum operating depth. The thickness and the fiber orientation angles in each layer, the radii of the ellipse, and stringers dimensions were taken as design variables and determined in the design process. The optimization procedures are 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.

Hydrostatic pressure

Ellipse

Hydrostatic test

Optimal design

Offshore geotechnical engineering

10.1155/2014/987903

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Citations (34)

Optimal Configuration for Stiffened Plates under the Effect of Underwater Explosion

Materials science forum (2015)

Elsayed Fathallah Hui Qi Li Li Tong Mahmoud Helal

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.

Underwater explosion

Shock response spectrum

10.4028/www.scientific.net/msf.813.161

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Citations (1)

Numerical Analysis for Critical Structures Protection against Blast Loading Using Metallic Panels

Applied Sciences (2020)

Ageel F. Alogla Mahmoud Helal Mohamed Mokbel Elshafey Elsayed Fathallah

The need for building protection against blast loads is a crucial issue nowadays due to the escalating threat of terrorist attacks, which affect people’s lives and critical structures. Consequently, design of protective panels to segregate building façades from the effect of a nearby explosion is required. Such design mainly depends on the ability of protective panels to mitigate and diffract the blast wave before reaching building façades. Five protective panel models with different designs, referred to as the Combined Protection System (CPS), are introduced in this paper. The main objective of this research was to achieve a design that could sustain a blast load with minimum plastic deformations. The introduced CPS designs included two steel plates linked by connector plates. The CPS dimensions were 3 m × 3 m × 0.35 m, representing length, width, and height, respectively. After that, the successful panel design was supported by placing these panels onto a masonry wall in different configurations. The protective panels were tested against 50 kg of trinitrotoluene (TNT) with a standoff distance of one meter. The final run of the optimum model was carried out using a blast load equivalent to 500 kg of TNT. The air–structure interactions were simulated using finite element analysis software called “ANSYS AUTODYN”, where the deformation of the panel was the governing parameter to evaluate the behavior of different designs. The analysis showed minimum deformation of the CPS design with vertical and horizontal connecting plates in a masonry wall distanced at 500 mm from the panel. However, the other designs showed promising results, which could make them suitable for critical structural protection on different scales.

10.3390/app10062121

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Citations (12)

Optimal Design Analysis of Composite Submersible Pressure Hull

Applied Mechanics and Materials (2014)

Elsayed Fathallah Hui Qi Li Li Tong Mahmoud Helal

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.

Hydrostatic test

Hydrostatic pressure

Ellipse

Hydrostatic equilibrium

10.4028/www.scientific.net/amm.578-579.89

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Citations (18)

Design Optimization of a Flexible Hinge Compliant Micro icro-Gripper ripper Mechanism with Parallel Movement Arms Using Pseudo-Rigid -Body Model

International Conference on Aerospace Sciences and Aviation Technology (2017)

Ageel F. Alogla Mahmoud Helal Abdal Allah Abdal Allah Elsayed Fathallah

Nano/Micro-electro-mechanical-system (NEMS/MEMS) consists of couplings of electrical and mechanical components within the micro-scale.Their nonlinear working state makes their analysis complex and complicated.Compliant mechanisms can (CMs) achieve a specified motion as a mechanism without relying on the use of joints and pins.They have broad application in precision mechanical devices and Nano/Micro-electro-mechanicalsystems.Compliant mechanisms are suggested as alternates for simplification of assembly and for miniaturization.The design synthesis of compliant mechanisms yields optimized topologies that combine several stiff parts with highly elastic flexural hinges.In this paper, Finite Element Analysis (FEA) analysis and design of a compliant micro-gripper compliant mechanism with parallel movement arm are presented by employing its Pseudo Rigid Body Model (PRBM), which leads to the establishment of high performance mechanism.This micro-gripper is capable of delivering high precision and fidelity manipulation of micro objects.The mechanism adopts a flexure-based concept on its joints to address the inherent nonlinearities associated with the application of conventional rigid hinges.

Compliant mechanism

Nanoelectromechanical systems

Multibody system

10.21608/asat.2017.22801

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Citations (1)

Numerical study on the rotation capacity of SIP-strengthened cold-formed steel beams

Engineering Structures (2021)

Hussein Shawki Osman Mohammed H. Serror Elsayed Fathallah

Flange

Cold-Formed Steel

Ductility (Earth science)

10.1016/j.engstruct.2021.113542

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Citations (5)

Numerical Analysis and Dynamic Response of Optimized Composite Cross Elliptical Pressure Hull Subject to Non-Contact Underwater Blast Loading

Applied Sciences (2019)

Mahmoud Helal Huinan Huang Elsayed Fathallah Defu Wang Mohamed Mokbel Elshafey

Among the most important problems confronted by designers of submarines is to minimize the weight, increase the payload, and enhance the strength of pressure hull in order to sustain the hydrostatic pressure and underwater explosions (UNDEX). In this study, a Multiple Intersecting Cross Elliptical Pressure Hull (MICEPH) subjected to hydrostatic pressure was first optimized to increase the payload according to the design requirements. Thereafter, according to the optimum design results, a numerical analysis for the fluid structure interaction (FSI) phenomena and UNDEX were implemented using nonlinear finite element code ABAQUS/Explicit. The propagation of shock waves through the MICEPH was analyzed and the response modes (breathing, accordion and whipping) were discussed. Furthermore, the acceleration, displacement and failure index time histories at different locations were presented. The results showed that the greatest acceleration occurred in the athwart direction, followed by the vertical and longitudinal directions. Additionally, the first bubble pulse has a major effect on athwart acceleration. Moreover, the analysis can be effectively used to predict and calculate the failure indices of pressure hull. Additionally, it provides an efficient method that reasonably captures the dynamic response of a pressure hull subjected to UNDEX.

Underwater explosion

Hydrostatic pressure

Dynamic pressure

Payload (computing)

10.3390/app9173489

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Citations (12)

Numerical Simulation and Response of Stiffened Plates Subjected to Noncontact Underwater Explosion

Advances in Materials Science and Engineering (2014)

Elsayed Fathallah Hui Qi Lili Tong Mahmoud Helal

A numerical simulation has been carried out to examine the response of steel plates with different arrangement of stiffeners and subjected to noncontact underwater explosion (UNDEX) with different shock loads. Numerical analysis of the underwater explosion phenomena is implemented in the nonlinear finite element code ABAQUS/Explicit. The aim of this work is to enhance the dynamic response to resist UNDEX. Special emphasis is focused on the evolution of mid-point displacements. Further investigations have been performed to study the effects of including material damping and the rate-dependant material properties at different shock loads. The results indicate that stiffeners configurations and shock loads affect greatly the overall performance of steel plates and sensitive to the materials data. Also, the numerical results can be used to obtain design guidelines of floating structures to enhance resistance of underwater shock damage, since explosive tests are costly and dangerous.

Underwater explosion

Shock response spectrum

10.1155/2014/752586

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Citations (13)

Dynamic behavior of stiffened plates under underwater shock loading

Materials Testing (2015)

Mahmoud Helal Elsayed Fathallah

Abstract A numerical investigation has been carried out to examine the behavior of stiffened steel plates subjected to different shock loads resulting from an underwater explosion (UNDEX). The aim of this work is to enhance the dynamic response to resist UNDEX and obtain the optimal configuration for stiffened plates 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 code. Special emphasis is focused on the evolution of mid-point displacements and velocity. Further investigations have been performed to study the effects of including material damping and the rate-dependent material properties at different shock loads. The results indicate that stiffeners configurations and shock loads affect greatly the overall performance of steel plates and are sensitive to the materials data. Also, the numerical results can be used to obtain design guidelines of floating structures to enhance resistance of underwater shock damage, since explosive tests are costly and dangerous.

Underwater explosion

Shock response spectrum

10.3139/120.110744

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Citations (9)

Optimum Structural Design of Deep Submarine Pressure hull to achieve Minimum Weight

The International Conference on Civil and Architecture Engineering (2016)

Elsayed Fathallah Mahmoud Helal

The pressure hull is a significant structural component of underwater vehicles, to enable them to withstand environmental loadings such as hydrostatical pressure.Geometric configurations such as hull shape, shell thickness, stiffener layout, and type of construction materials are the key factors influencing the structural performance of pressure hulls.This study aims 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 to achieve Minimum Weight, with constraints on factors such as general instability, buckling of shell between stiffeners, plate yielding, stiffeners yielding and operating depth.The shell thickness, the radii of the ellipse, the stiffeners offsets and the stiffeners dimensions are selected as design variables.Additionally, a sensitivity analysis is performed to study the influence of the design variables on the structural optimum design, the buoyancy factor ， strength and stability ． The Optimization results of this study provide a valuable reference for designers of underwater vehicles.

Hydrostatic pressure

Hydrostatic equilibrium

Ellipse

Hydrostatic test

10.21608/iccae.2016.43445

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Citations (5)