Reliability Based Optimization of Submarine Pressure Hulls With Inelastic Interstiffener Buckling Failure

2006 ◽  
Author(s):  
P. Radha ◽  
K. Rajagopalan
Keyword(s):  
Unconstrained Minimization ◽  
Computer Code ◽  
Correction Method ◽  
Penalty Function Method ◽  
Simulation Design ◽  
Design Variables ◽  
Minimization Technique ◽  
Buckling Failure ◽  
Optimal Values ◽  
Reliability Based Optimization

Uncertainties that exist in modelling and simulation, design variables and parameters, manufacturing processes etc., may lead to large variations in the performance characteristics of the system. Optimized deterministic designs determined without considering uncertainties can be unreliable and may lead to catastrophic failure of the structure being designed. Reliability based optimization (RBO) is a methodology that addresses these problems. In this paper the reliability based optimization of submarine pressure hulls in which the failure gets governed by inelastic interstiffener buckling has been described. The problem has been formulated to minimize the ratio of weight of shell-stiffener geometry to the weight of liquid displaced, subjected to reliability based inelastic interstiffener buckling constraint. Since the methods of analysis of inelastic buckling failure of submarine pressure hulls are inadequate, in the present study the Johnson-Ostenfeld inelastic correction method has been adopted for formulating the constraint. By considering spacing of the stiffener, thickness of the plating and depth of the stiffener as the design variables, Sequential Unconstrained Minimization Technique (SUMT) has been used to solve the design problem. RBO has been carried out to get the optimal values of these design variables for a target reliability index using Interior Penalty Function Method for which an efficient computer code in C++ has been developed.

Optimum Design of I. C. Engine Pistons

1984 ◽  
Vol 106 (2) ◽  
pp. 209-213 ◽  
Author(s):  
S. S. Rao ◽  
S. S. Srinivasa Rao
Keyword(s):  
Function Method ◽  
Optimization Problems ◽  
Interpolation Method ◽  
Unconstrained Minimization ◽  
Penalty Function Method ◽  
Minimum Volume ◽  
Constrained Optimization Problems ◽  
One Dimensional ◽  
Design Variables ◽  
Powell Method

The minimum volume design of I. C. engine pistons is considered with constraints on temperature and stresses developed in the piston. The interior penalty function method, coupled with the Davidon-Fletcher-Powell method of unconstrained minimization and the cubic interpolation method of one-dimensional search, is used for solving the constrained optimization problems. The temperature and stresses developed in the piston are determined by using the classic as well as the finite element methods of analysis. A sensitivity analysis is conducted to find the influence of changes in design variables on the objective function and the response parameters.

Optimum Design of Axial Flow Gas Turbine Stage—Part I: Formulation and Analysis of Optimization Problem

1980 ◽  
Vol 102 (4) ◽  
pp. 782-789 ◽  
Author(s):  
S. S. Rao ◽  
R. S. Gupta
Keyword(s):  
Gas Turbines ◽  
Optimization Problem ◽  
Interpolation Method ◽  
Axial Flow ◽  
Unconstrained Minimization ◽  
Problem Formulation ◽  
Mathematical Programming Problem ◽  
Penalty Function Method ◽  
Variable Metric ◽  
Minimization Technique

The problem of stage design of axial flow gas turbines has been formulated as a nonlinear mathematical programming problem with the objective of minimizing aerodynamic losses and mass of the stage. The aerodynamic as well as mechanical constraints are considered in the problem formulation. A method of evaluating the objective function and constraints of the problem is presented in Part I of this paper. The optimization problem is solved by using the interior penalty function method in which the Davidon-Fletcher-Powell variable metric unconstrained minimization technique with cubic interpolation method of one-dimensional minimization is employed. Problems involving the optimization of efficiency and/or mass of the stage have been solved numerically in Part II of the paper. The results of a sensitivity analysis conducted about the optimum point have also been reported.

Optimum Design of Axial Flow Gas Turbine Stage—Part II: Solution of the Optimization Problem and Numerical Results

1980 ◽  
Vol 102 (4) ◽  
pp. 790-797 ◽  
Author(s):  
S. S. Rao ◽  
R. S. Gupta
Keyword(s):  
Gas Turbines ◽  
Optimization Problem ◽  
Interpolation Method ◽  
Axial Flow ◽  
Unconstrained Minimization ◽  
Problem Formulation ◽  
Mathematical Programming Problem ◽  
Penalty Function Method ◽  
Variable Metric ◽  
Minimization Technique

The problem of stage design of axial flow gas turbines has been formulated as a nonlinear mathematical programming problem with the objective of minimizing aerodynamic losses and mass of the stage. The aerodynamic as well as mechanical constraints are considered in the problem formulation. A method of evaluating the objective function and constraints of the problem is presented in Part I of this paper. The optimization problem is solved by using the interior penalty function method in which the Davidon-Fletcher-Powell variable metric unconstrained minimization technique with cubic interpolation method of one dimensional minimization is employed. Problems involving the optimization of efficiency and/or mass of the stage have been solved numerically in Part II of the paper. The results of sensitivity analysis conducted about the optimum point have also been reported.

Integrally-Stiffened Composite Damage Tolerance Evaluated by Computational Simulation

2001 ◽  
Author(s):  
Christos C. Chamis ◽  
Levon Minnetyan
Keyword(s):  
Material Properties ◽  
Composite Structures ◽  
Failure Modes ◽  
Damage Tolerance ◽  
Epoxy Composite ◽  
Computational Simulation ◽  
Computer Code ◽  
Simulation Design ◽  
Damage Initiation ◽  
Composite Damage

Abstract An integrally stiffened graphite/epoxy composite rotorcraft structure is evaluated via computational simulation. A computer code that scales up constituent micromechanics level material properties to the structure level and accounts for all possible failure modes is used for the simulation of composite degradation under loading. Damage initiation, growth, accumulation, and propagation to fracture are included in the simulation. Design implications with regard to defect and damage tolerance of integrally stiffened composite structures are examined. A procedure is outlined regarding the use of this type of information for setting quality acceptance criteria, design allowables, damage tolerance, and retirement-for-cause criteria.

Design Optimization of RML Glove for Improved Grasp Performance

2018 ◽  
Author(s):  
Teja Vanteddu ◽  
Bijo Sebastian ◽  
Pinhas Ben-Tzvi
Keyword(s):  
Design Optimization ◽  
Daily Living ◽  
Experimental Validation ◽  
Large Diameter ◽  
Future Research ◽  
Linkage Mechanism ◽  
Design Variables ◽  
Wide Range ◽  
Optimal Values ◽  
Optimal Set

This paper describes the design optimization of the RML Glove in order to improve its grasp performance. The existing design is limited to grasping objects of large diameter (> 110mm) due to its inability in attaining high bending angles. For an exoskeleton glove to be effective in its use as an assistive and rehabilitation device for Activities of Daily Living (ADL), it should be able to interact with objects over a wide range of sizes. Motivated by these limitations, the kinematics of the existing linkage mechanism was analyzed in detail and the design variables were identified. Two different cost functions were formulated and compared in their ability to yield optimal values for the design variables. The optimal set of design variables was chosen based on the grasp angles achieved and the resulting mechanism was simulated in CAD for feasibility testing. An exoskeleton mechanism corresponding to the index finger was manufactured with the chosen design variables and detailed experimental validation was performed to illustrate the improvement in grasp performance over the existing design. The paper ends with a summary of the experimental results and directions for future research.

STAEBL/General Composites With Hygrothermal Effects (STAEBL/GENCOM)

1988 ◽  
Vol 110 (2) ◽  
pp. 301-305
Author(s):  
R. Rubinstein
Keyword(s):  
Composite Laminates ◽  
Fiber Composite ◽  
Thickness Distribution ◽  
Turbine Blades ◽  
Material Design ◽  
Computer Code ◽  
Forced Response ◽  
General Description ◽  
Blade Thickness ◽  
Design Variables

A computer code has been developed to perform structural optimization of turbine blades made from angle ply fiber composite laminates. Design variables available for optimization include geometric parameters such as blade thickness distribution and root chord, and composite material parameters such as ply angles and numbers of plies of each constituent material. Design constraints include resonance margins, forced response margins, maximum stress, and maximum ply combined stress. A general description of this code is given. Design optimization studies for typical blades are presented.

Optimal Thermal Design of Fin-and-Tube Heat Exchangers by Integration of a SUMT and a SCGM

2016 ◽  
Author(s):  
Xinyi Li ◽  
Ting Ma ◽  
Qiuwang Wang
Keyword(s):  
Heat Exchangers ◽  
Optimization Technique ◽  
Unconstrained Minimization ◽  
Geometric Parameters ◽  
Thermal Design ◽  
Trial And Error ◽  
Heat Transfer Area ◽  
Compact Heat Exchangers ◽  
Minimization Technique ◽  
Combined Structure

It is a recognized hard task for the traditional thermal design of compact heat exchangers to obtain the optimal geometric parameters efficiently and effectively, owing to its complex trial-and-error process. In response to this issue, a simplified conjugate-gradient method (SCGM) combined with a sequential unconstrained minimization technique (SUMT) as a favorable optimization technique is incorporated with the traditional thermal design in this study, and then the key geometric parameters of fin-and-tube heat exchangers (FTHEs) are investigated and optimized successfully. In this method, the minimum total weight of FTHEs as the final objective is discussed, involving two geometric parameters, diameter of tube and height of shape as search variables. Aiming to minimize the objective function, SCGM is introduced to the SUMT to update the search variables continually with the fixed search steps and the search directions. Meanwhile, with the known geometric parameters from the SUMT, the log-mean temperature difference method (LMTD) is applied to determine the heat transfer area under the combined structure sizes for a given heat duty. Additionally, optimization results for three different heat duty is discussed in this work. The results show that it is effective to obtain the optimal sets of geometric parameters of FTHEs by the present method, and there are some guidance values for the thermal designs of compact heat exchangers.

Sign in / Sign up

Export Citation Format

Share Document