Optimum Autofrettage and Shrink-Fit Combination in Multi-Layer Cylinders

2005 ◽  
Vol 128 (2) ◽  
pp. 196-200 ◽  
Author(s):  
Hamid Jahed ◽  
Behrooz Farshi ◽  
Morvarid Karimi
Keyword(s):  
Fatigue Life ◽  
Life Expectancy ◽  
Crack Depth ◽  
Optimization Procedure ◽  
Optimization Method ◽  
Stress Constraints ◽  
Simplex Search ◽  
Design Variables ◽  
Significant Life ◽  
Shrink Fit

The interest in the use of layered cylinders that combine autofrettage and shrink fit in order to extend fatigue lifetimes is increasing. As the number of layers increases, the sequential order of assembly and the size of each layer become more important. To achieve the most benefical result, a design optimization method is required. In this investigation, the optimum design of a three-layered vessel for maximum fatigue life expectancy under the combined effects of autofrettage and shrink fit has been considered. To obtain optimum size of each layer and to optimize the initial stress distribution, the numerical optimization procedure known as the Simplex search method is employed here. The thickness of each layer, shrink-fit pressures, and autofrettage percentages are treated as design variables. Under stress constraints, the operational sequences for assembly of a layered vessel have been formulated in order to lead to optimum results, defined as maximum life expectancy. The fatigue life consideration is based on ASME code provisions and standards for high pressure vessel technology, which define the allowable final crack depth for multilayer vessels. The proposed procedure has been carried out on a number of examples. The results show that, with proper combination of operations significant life enhancement can be achieved using the optimization procedure.

Optimum Design of Multi-Layered Vessels

2005 ◽  
Author(s):  
Hamid Jahed ◽  
Behrooz Farshi ◽  
Morvarid Karimi
Keyword(s):  
High Pressure ◽  
Optimum Design ◽  
Load Capacity ◽  
Crack Depth ◽  
Optimization Procedure ◽  
Stress Constraints ◽  
Pressure Vessels ◽  
Design Variables ◽  
Significant Life ◽  
Shrink Fit

Multi-layered pressure vessels are widely used in the field of high pressure technology. To enhance their load bearing capacity and life, different beneficial processes such as shrink-fit and autofrettage are usually employed. Shrink-fit process, increases load capacity but maximum interference is generally limited. Autofrettage, makes steep stress gradients moving away from bore but Bauschinger effect limits maximum feasible compression level. A combination of both, can conceivably give better stress distribution in layered vessels. The optimum design of a three-layer vessel for maximum life expectancy has been considered here, under the combined effects of autofrettage and shrink-fit. The numerical optimization procedure known as the Simplex search method is employed to get the optimum design. The layer thicknesses, shrink-fit pressures, and autofrettage percentages are treated as design variables. Under stress constraints, the operational sequences of the above processes, for assembly of the layered vessel have also been formulated so as to lead to best results. The fatigue life consideration is based on ASME code and standard for high pressure vessel technology defining the allowable final crack depth in multi-layered vessels. The proposed procedure is carried out on a number of examples. The results show that significant life enhancement can be achieved using the optimization procedure with proper combination of operations.

Structural Optimization of Composite Panel with Lamination Parameters and Equivalent Stiffness Laminate Method

2014 ◽  
Vol 496-500 ◽  
pp. 429-435
Author(s):  
Xiao Ping Zhong ◽  
Peng Jin
Keyword(s):  
Genetic Algorithm ◽  
Structural Optimization ◽  
Composite Structure ◽  
Optimization Procedure ◽  
Optimization Method ◽  
Composite Panel ◽  
Analysis Tool ◽  
Equivalent Stiffness ◽  
Lamination Parameters ◽  
Design Variables

Firstly, a two-level optimization procedure for composite structure is investigated with lamination parameters as design variables and MSC.Nastran as analysis tool. The details using lamination parameters as MSC.Nastran input parameters are presented. Secondly, with a proper equivalent stiffness laminate built to substitute for the lamination parameters, a two-level optimization method based on the equivalent stiffness laminate is proposed. Compared with the lamination parameters-based method, the layer thicknesses of the equivalent stiffness laminate are adopted as continuous design variables at the first level. The corresponding lamination parameters are calculated from the optimal layer thicknesses. At the second level, genetic algorithm (GA) is applied to identify an optimal laminate configuration to target the lamination parameters obtained. The numerical example shows that the proposed method without considering constraints of lamination parameters can obtain better optimal results.

Topology Optimization of Compliant Mechanisms Using Hybrid Discretization Model

2010 ◽  
Vol 132 (11) ◽  
Author(s):  
Hong Zhou
Keyword(s):  
Topology Optimization ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Optimization Procedure ◽  
Optimization Method ◽  
Diagonal Element ◽  
Initial Guess ◽  
Stress Constraint ◽  
Design Variables ◽  
Hybrid Discretization

The hybrid discretization model for topology optimization of compliant mechanisms is introduced in this paper. The design domain is discretized into quadrilateral design cells. Each design cell is further subdivided into triangular analysis cells. This hybrid discretization model allows any two contiguous design cells to be connected by four triangular analysis cells whether they are in the horizontal, vertical, or diagonal direction. Topological anomalies such as checkerboard patterns, diagonal element chains, and de facto hinges are completely eliminated. In the proposed topology optimization method, design variables are all binary, and every analysis cell is either solid or void to prevent the gray cell problem that is usually caused by intermediate material states. Stress constraint is directly imposed on each analysis cell to make the synthesized compliant mechanism safe. Genetic algorithm is used to search the optimum and to avoid the need to choose the initial guess solution and conduct sensitivity analysis. The obtained topology solutions have no point connection, unsmooth boundary, and zigzag member. No post-processing is needed for topology uncertainty caused by point connection or a gray cell. The introduced hybrid discretization model and the proposed topology optimization procedure are illustrated by two classical synthesis examples of compliant mechanisms.

scholarly journals Optimization of Grillage-like Continuum by Triangle Plate Element

2012 ◽  
Vol 6 (1) ◽  
pp. 8-14
Author(s):  
Kemin Zhou ◽  
Xia Li
Keyword(s):  
Optimization Procedure ◽  
Material Model ◽  
Stress Constraints ◽  
Design Domain ◽  
Material Distribution ◽  
Plate Element ◽  
Design Variables ◽  
Plate Elements ◽  
Discrete Structures ◽  
Optimal Material

The volume of grillages with stress constraints is minimized. An optimal beams system or plate with reinforced ribs is obtained to present the optimal structure. A grillage-like continuum material model is adapted. Structure is analyzed by finite element method with triangle plate elements. The geometric matrix of triangle plate element in explicit formulation about area coordinates is presented. The stiffness matrix of grillage-like continuum material model is derived. The material distribution field in design domain is optimized by fully-stressed criterion. The densities and orientations of the beam or reinforced ribs at nodes in grillages are taken as design variables. The densities and orientations vary in design domain continuously. The optimal distribution fields of bend moments, flexure displacement and material are obtained simultaneously. Subsequently the discrete structures are founded based on the optimal material distribution fields. The performances of different elements are compared. The optimization procedure is accomplished by computer program automatically.

The Modified Quadrilateral Discretization Model for the Topology Optimization of Compliant Mechanisms

2011 ◽  
Vol 133 (11) ◽  
Author(s):  
Hong Zhou ◽  
Pranjal P. Killekar
Keyword(s):  
Topology Optimization ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Optimization Procedure ◽  
Local Stress ◽  
Optimization Method ◽  
Stress Constraint ◽  
Cell Problem ◽  
Design Variables ◽  
Design Cell

The modified quadrilateral discretization model for the topology optimization of compliant mechanisms is introduced in this paper. The design domain is discretized into quadrilateral design cells. There is a certain location shift between two neighboring rows of quadrilateral design cells. This modified quadrilateral discretization model allows any two contiguous design cells to share an edge whether they are in the horizontal, vertical, or diagonal direction. Point connection is completely eliminated. In the proposed topology optimization method, design variables are all binary, and every design cell is either solid or void to prevent gray cell problem that is usually caused by intermediate material states. Local stress constraint is directly imposed on each analysis cell to make the synthesized compliant mechanism safe. Genetic algorithm is used to search the optimum. No postprocessing is required for topology uncertainty caused by either point connection or gray cell. The presented modified quadrilateral discretization model and the proposed topology optimization procedure are demonstrated by two synthesis examples of compliant mechanisms.

An Aerodynamic Optimization Procedure for the Preliminary Design of Centrifugal Compressor Stages

2008 ◽  
Author(s):  
Omar Elshamy ◽  
Nidal Ghizawi ◽  
Ce´line Yon ◽  
Simone Pazzi ◽  
Denis Guenard
Keyword(s):  
Centrifugal Compressor ◽  
Optimization Procedure ◽  
Optimization Method ◽  
Computational Time ◽  
Preliminary Design ◽  
Trial And Error ◽  
Aerodynamic Optimization ◽  
Peak Efficiency ◽  
Stage Design ◽  
Design Variables

This paper presents an automated aerodynamic optimization procedure for the preliminary design of centrifugal compressors. The proposed procedure interfaces a well-validated prediction tool with a GE in-house developed optimization code (PEZ). In GE Oil & Gas this tool is used to predict the performance of a single centrifugal compressor stage the outline of which requires more than thirty geometric parameters to be set. In the early phase of a new stage design, the designer manually varies all related parameters in the framework of a trial-and-error approach. The optimization procedure eliminates the inconvenience of a vast amount of manually launched simulations required by variations of the large number of design variables. Additionally, this procedure can perform trade-off studies and sensitivity analysis. In this case the optimization plan consists of a differential evolution (DE) genetic algorithm followed by a simplex-based optimization method (AMOEBA). The procedure was challenged with several existing designs by setting different objective/constraints combinations. The optimizer was often able to improve the predicted performance, as for an old 2D design where it was possible to increase the peak efficiency of approximately 2.6%. Also, the algorithm proved able to maximize the polytropic head (+12% with respect to baseline), while keeping unaltered both surge and choke limits. The computational time was about 40 hours per case on a Windows workstation (3.20 GHz, 3.5 GB RAM).

The Modified Quadrilateral Discretization Model for the Topology Optimization of Compliant Mechanisms

2011 ◽  
Author(s):  
Hong Zhou ◽  
Pranjal P. Killekar
Keyword(s):  
Topology Optimization ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Optimization Procedure ◽  
Local Stress ◽  
Optimization Method ◽  
Initial Guess ◽  
Stress Constraint ◽  
Design Variables ◽  
Conduct Sensitivity Analysis

The modified quadrilateral discretization model for the topology optimization of compliant mechanisms is introduced in this paper. The design domain is discretized into quadrilateral design cells. There is a certain location shift between two neighboring rows of quadrilateral design cells. This modified quadrilateral discretization model allows any two contiguous design cells to share an edge whether they are in the horizontal, vertical or diagonal direction. Point connection is completely eliminated. In the proposed topology optimization method, design variables are all binary and every design cell is either solid or void to prevent grey cell problem that is usually caused by intermediate material states. Local stress constraint is directly imposed on each analysis cell to make the synthesized compliant mechanism safe. Genetic algorithm is used to search the optimum and avoid the need to select the initial guess solution and conduct sensitivity analysis. No postprocessing is needed for topology uncertainty caused by point connection or grey cell. The presented modified quadrilateral discretization model and the proposed topology optimization procedure are demonstrated by two synthesis examples of compliant mechanisms.

Structural Synthesis by Method of Centers in Force Formulation under Size and Stress Constraints

2010 ◽  
Vol 26 (4) ◽  
pp. 513-524
Author(s):  
B. Farshi ◽  
A. Alinia-ziazi
Keyword(s):  
Minimum Weight ◽  
Load Condition ◽  
Optimization Method ◽  
Stress Constraints ◽  
Cross Sectional ◽  
Method Of Centers ◽  
Novel Approach ◽  
Design Variables ◽  
Weight Design ◽  
Optimization Routine

ABSTRACTThis paper studies a novel approach to optimize trusses and truss-like structures for minimum weight design. It is based on the force method of analysis which is incorporated inside the optimization routine. The design variables in force formulation are the member cross sectional areas and the redundant forces in each load condition. The optimization method used is the method of center points using the inscribed hyperspheres to the feasible-usable design space. By incorporating the analysis step as part of the optimization problem, a separate structural solution phase, which is necessary in all other methods, is avoided resulting in large computational savings. In this article the simplest form of structures i.e. trusses are treated to illustrate the efficacy of the method. Stress limits on the members as well as limitations on their sizes, and linking among them, under several load conditions have been considered. Combination of the method of center points and force formulation results in a viable routine for structural optimization. Comparison of the example results with those obtained by others clearly shows the effectiveness and novelty of the proposed method.

scholarly journals Optimization of Low-Power Line-Start PM Motor Using Gray Wolf Metaheuristic Algorithm

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1186 ◽  
Author(s):  
Łukasz Knypiński ◽  
Karol Pawełoszek ◽  
Yvonnick Le Menach
Keyword(s):  
Low Power ◽  
Induction Motor ◽  
Permanent Magnet Synchronous Motor ◽  
Computer Software ◽  
Optimization Procedure ◽  
Optimization Method ◽  
Power Line ◽  
Gray Wolf ◽  
Design Variables ◽  
Rotor Structure

The paper presents the optimization method and computer software for the design of a low-power line-start permanent magnet synchronous motor (LSPMSM). The in-house-developed computer software was created with two independent modules: (a) the optimization procedure and (b) the numerical model of the motor. The optimization procedure used was a metaheuristic optimization method based on the gray wolf algorithm. Four design variables linked to the rotor structure were selected. The optimization process was performed from the rotor of a low-power induction motor (IM). The prototype of the motor (LSPMSM) was then built. The experimental measurements were performed for base the IM and optimized LSPMSM. The results of the measurements were compared for both motors. The experimental results confirmed the better performance of the designed motor in comparison to the induction motor.

Application of a PSO algorithm for identification of the parameters of Jiles-Atherton hysteresis model

2012 ◽  
Vol 61 (2) ◽  
pp. 139-148 ◽  
Author(s):  
Łukasz Knypiński ◽  
Lech Nowak ◽  
Piotr Sujka ◽  
Kazimierz Radziuk
Keyword(s):  
Particle Swarm Optimization ◽  
Particle Swarm ◽  
Optimization Procedure ◽  
Computer Code ◽  
Pso Algorithm ◽  
Optimization Method ◽  
Hysteresis Model ◽  
Swarm Optimization ◽  
Design Variables ◽  
Particle Swarm Optimization Method

Application of a PSO algorithm for identification of the parameters of Jiles-Atherton hysteresis modelIn the paper an algorithm and computer code for the identification of the hysteresis parameters of the Jiles-Atherton model have been presented. For the identification the particle swarm optimization method (PSO) has been applied. In the optimization procedure five design variables has been assumed. The computer code has been elaborated using Delphi environment. Three types of material have been examined. The results of optimization have been compared to experimental ones. Selected results of the calculation for different material are presented and discussed.

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