Sayed M. Metwalli

Computer aided optimization of natural gas pipe networks using genetic algorithm

This study is concerned to determine the optimum pipe size for networks used in natural gas applications. The genetic algorithm has been used in optimizing network parameters. The topology of the network is predefined. The study deals with the discrete nature of decision variables, namely, pipe diameters, as they are usually available in market in standard sizes. Hard constraints and soft constraints are considered. An imposed penalty factor is introduced to allow solutions that violate soft constraints to remain in the population during the solution progress guiding the algorithm convergence to a minimum network cost. In a case study, engineers with average experience of 6 years in the design office of a gas company performed the design of a gas network problem using their experience and judgment. The adopted method by engineers depends on a trial and error, time consuming, procedure. Their results are compared with the results obtained from the developed genetic algorithm optimization technique. The developed optimization technique has provided a distinctive reduction in the total cost of pipe networks over the existing heuristic approach which is based on human experience and judgment. A saving up to 12.1% has been achieved using the present analysis, in the special case studied.

Computer aided reliabilty for optimum maintenace planning

Computer aided Maintenance planning for mechanical equipment is presented in this work to implement the optimized extensive maintenance plan at a specific time horizon. The objective is to interchange the unscheduled corrective maintenance into scheduled preventive maintenance depending on historical data of equipment. This work is concerned with development of reliability analysis based on Weibull distribution. An optimization technique has been developed to provide the optimized preventive maintenance plan for the whole equipment during a required time horizon.

Stability of Y stiffeners in ship plating under uniaxial compressive loads

Abstract Ship plates are stiffened using different stiffeners. In this paper, a Y stiffener is considered and investigated. A Y stiffener–plate combination model is used to represent the stiffened panel. Our contribution includes characterizing the local instability (buckling) of Y stiffeners in stiffened panels under the action of uniaxial compressive loads. The mathematical derivations have been carried out to find the elastic buckling coefficient for the web of the T-part of the Y stiffener under suitable boundary conditions. Then, the critical value of the buckling stress has been calculated. Using the value of the critical stress and the assumption of uniform stress distribution, the buckling load is calculated for the Y stiffener–plate combination model. Using curve fitting of the analytically obtained results, approximate expressions for calculation of the elastic buckling coefficient of the T-part of the Y stiffener are obtained. These approximate expressions enable designers to calculate easily the elastic buckling coefficient from which the critical buckling stress of the T-part is obtained.

Optimum Design of Variable-Material Flywheels

This paper deals with design configurations that would maximize energy stored per unit mass of flywheel and would also lead to more uniform stress distribution within yield limits. A “shape factor” is herein used to relate inertia per unit mass to specific strength (viz., yield strength per unit density), the flywheel being equally stressed in both radial and tangential directions. A proposed “optimum design function” is shown to facilitate the search for an optimum design of an isotropic variable-material flywheel. Multimaterial flywheels, made up of suitable groups of materials may well provide higher inertia per unit mass than the corresponding constant-strength disk made of any material in the group. Examples of two-element alloy flywheels (lead-tin and aluminum-magnesium) with higher inertia per unit mass than the constant-strength disk are displayed.

Heuristic Gradient Projection for 3D Space Frame Optimization

The purpose of this work is to develop a novel optimization process for the design of space frames. The main objective is to minimize the space frame volume and consider stress constraints satisfaction. A finite element program is devised to synthesize 3D-space frames and aid in its topology optimization. The program is verified through different elementary problems with known analytical solutions as well as with commercial packages. A Midi-Bus frame is modeled with about 300 members and analyzed for a severe road model condition. The optimization effectively uses the devised Heuristic Gradient Projection (HGP) technique to synthesize the optimum Midi-Bus frame. Results indicate a marked improvement over available designs and remarkably faster convergence over other optimization techniques. This technique can thus be effectively applied to other large 3D space frame synthesis and optimization.© 2005 ASME

New optimum humanoid hand design for prosthetic applications.

To address the need for a commercially feasible prosthetic hand, the current work presents the design of a new humanoid hand actuated using shape memory alloy (SMA) artificial muscle wires. The hand has 3 compliant fingers and a thumb attached to the palm. The palm structure is a novel design, which is based on the natural arches of the human hand to provide better grasping capabilities. A compact actuator module is proposed to house and cool the SMA wires. Design parameters of the hand were selected to maximize the work density. The hand is lightweight, low cost, and operates silently. It has functional opening and closing speeds and fingertip force.

Topology Optimization of a Compliant Gripper Using Hybrid Simulated Annealing and Direct Search

The present work introduces a new methodology for solving the topology optimization problem of a compliant gripper. A hybrid optimization technique is developed using simulated annealing as a random search method, while the simplex method (Nelder-Mead) is used as a direct search method. A new modified technique of motion from one search point to another based on the discrete nature of adding and/or removing a structural member is proposed. The traditional continuous simulated annealing technique is used to find the members’ heights. A discrete uni-variant search method is adopted following the simulated annealing and before the simplex method. This corresponds to about 14% of the number used in the old method and in the previous work in the literature, and about 86% of the optimization time is saved. The optimum design of a compliant mechanism is conducted for maximum flexibility and stiffness using the developed hybrid optimization technique.Copyright

PRELIMINARY ASSESSMENT OF IMAGE PROCESSING, APPLICATION TO LARGE DEFORMATION MEASUREMENT

ABSTRACT This paper deals with a new method for measuring large plastic deformations. The method utilizes image processing and recognition techniques in the evaluation of the change in length of a grid laid on tensile test-pieces. True stress-true strain behaviour obtained by this method is found to be very close to those obtained by other methods. The process developed here, with some modifications, can present a viable and accurate means for large deformation measurement and can be utilized for other similar applications.

System frequency tuning for heaving buoy wave energy converters

In this paper, we propose a control technique that maximizes power absorption in point absorber wave energy converter systems. This technique involves the tuning of the Eigen-frequency of the converter system to meet the incident waves energy frequency, providing near-resonance operation. The system was modeled, where the effects of radiation forces due to oscillator-generated waves were considered. The radiation forces depend on the hydrodynamic coefficients, the added mass, and the hydrodynamic damping, which are calculated through solving the hydrodynamic boundary value problem for heaving bodies. The power absorbed through the power take-off system corresponds to the external damping of the system. The frequency tuning is performed by changing the effective stiffness of the system through the introduction of an external stiffness that is connected in parallel to the buoy stiffness. We propose changing the effect of this external stiffness by means of a stepless V-belt variable speed drive, which changes the speed ratio continuously. The effect of changing the drive speed ratio on the system Eigen-frequency was investigated. The effects of the power take-off system equivalent damping on both the absorbed power and the absorption efficiency for a frequency-tuned system are presented. Numerical results showed promising power absorption and efficiency values, compared with other control techniques.

Design Optimization of a Solar-Powered Reverse Osmosis Desalination System for Small Communities

Fresh water availability is essential for the economic development in small communities in remote areas. In desert climate, where naturally occurring fresh water is scarce, seawater or brackish water from wells is often more abundant. Since water desalination approaches are energy intensive, a strong motivation exists for the design of cost-effective desalination systems that utilize the abundant renewable energy resource; solar energy. This paper presents an optimization model of a solar-powered reverse osmosis (RO) desalination system. RO systems rely on pumping salty water at high pressure through semi-permeable membrane modules. Under sufficient pressure, water molecules will flow through the membranes, leaving salt ions behind, and are collected in a fresh water stream. Since RO system are primarily powered via electricity, the system model incorporates photovoltaic (PV) panels, and battery storage for smoothing out fluctuations in the PV power output, as well as allowing system operation for a number of hours after sunset. Design variables include sizing of the PV solar collectors, battery storage capacity, as well as the sizing of the RO system membrane module and power elements. The objective is to minimize the cost of unit volume produced fresh water, subject to constraints on production capacity. A genetic algorithm is used to generate and compare optimal designs for two different locations near the Red Sea and Sinai.Copyright