Optimization of stiffened panels under compression

1986 ◽  
Vol 21 (3) ◽  
pp. 153-158
Author(s):  
Li Weiji
Keyword(s):  
Design Process ◽  
Numerical Results ◽  
Stability And Convergence ◽  
Stiffened Panel ◽  
Feasible Direction ◽  
Stiffened Panels ◽  
Feasible Direction Method ◽  
Design Variables ◽  
Effectiveness And Efficiency

The optimization of the angle-stiffened panel under compression using the feasible direction method is studied in this paper. We could only take the most critical constraint into account for each iteration when using the feasible direction method, with the result that the process of calculation is greatly simplified. It is beneficial for stability and convergence of the design process that the design variables in each iteration are modified once by some experience formulae, if necessary. The illustrative examples and the comparison of the numerical results of this paper with those of another paper indicate the effectiveness and efficiency of the method presented here.

Effect of Pressure on Collapse Behaviour of Stiffened Panel

2014 ◽  
Author(s):  
Lei Jiang ◽  
Shengming Zhang
Keyword(s):  
Finite Element ◽  
Failure Modes ◽  
Lateral Pressure ◽  
Initial Pressure ◽  
Offshore Structures ◽  
Numerical Results ◽  
Stiffened Panel ◽  
Longitudinal Stress ◽  
Stiffened Panels ◽  
Hull Girder

During normal operations, ship and offshore structures, are subjected to combined lateral pressure and in-plane stresses. The effect of the lateral pressure is often ignored in hull girder ultimate assessments. This paper investigates the influence of the lateral pressures on the nonlinear collapse behavior of stiffened panels subjected to in-plane longitudinal stress. In this study, nonlinear finite element analyses were first conducted for the desired pressure alone; the longitudinal stress was then applied up to and beyond the collapse of the structures. Four representative stiffened panels taken from the bottoms of different double hull oil tankers were considered. The nonlinear analyses were performed using LR’s in-house finite element program VAST and following the procedure for nonlinear collapse analysis developed by LR. The numerical results indicated that the application of the initial pressure loads not only reduced the ultimate load carrying capacity of the panels significantly, but also changed the failure modes of the structures. The sensitivity of the ultimate strength to lateral pressure was dependent upon the panel geometry and whether the pressure was applied on the plate or the stiffener side. The numerical results and findings from this study are presented in this paper.

scholarly journals Procedures for Shape Optimization of Gas Turbine Disks

1990 ◽  
Author(s):  
Tsu-Chien Cheu
Keyword(s):  
Shape Optimization ◽  
Gas Turbine ◽  
Stress Constraints ◽  
Design Sensitivity ◽  
Optimal Designs ◽  
Sequential Linear Programming ◽  
Feasible Direction ◽  
Feasible Direction Method ◽  
Design Variables ◽  
Turbine Disks

Two procedures, the feasible direction method and sequential linear programming, for shape optimization of gas turbine disks are presented in this paper. The objective of these procedures is to obtain optimal designs of turbine disks with geometric and stress constraints. The coordinates of the selected points on the disk contours are used as the design variables. Structural weight, stress and their derivatives with respect to the design variables are calculated by an efficient finite element method for design sensitivity analysis. Numerical examples of the optimal designs of a disk subjected to thermo-mechanical loadings are presented to illustrate and compare the effectiveness of these two procedures.

A fast procedure for the design of composite stiffened panels

2015 ◽  
Vol 119 (1212) ◽  
pp. 185-201 ◽  
Author(s):  
C. Bisagni ◽  
R. Vescovini
Keyword(s):  
Minimum Weight ◽  
Buckling Load ◽  
Stiffened Panel ◽  
Preliminary Design ◽  
Stiffened Panels ◽  
Design Variables ◽  
Epoxy Material ◽  
Composite Stiffened Panel ◽  
Post Buckling ◽  
Fast Procedure

AbstractThis paper describes the analysis and the minimum weight optimisation of a fuselage composite stiffened panel made from carbon/epoxy material and stiffened by five omega stringers. The panel investigated inside the European project MAAXIMUS is studied using a fast tool, which relies on a semi-analytical procedure for the analysis and on genetic algorithms for the optimisation. The semi-analytical approach is used to compute the buckling load and to study the post-buckling response. Different design variables are considered during the optimisation, such as the stacking sequences of the skin and the stiffener, the geometry and the cross-section of the stiffener. The comparison between finite element and fast tool results reveals the ability of the formulation to predict the buckling load and the post-buckling response of the panel. The reduced CPU time necessary for the analysis and the optimisation makes the procedure an attractive strategy to improve the effectiveness of the preliminary design phases.

Application of advanced RANS turbulence models for the prediction of turbomachinery flows

2021 ◽  
pp. 1-13
Author(s):  
Ernesto Casartelli ◽  
Luca Mangani ◽  
David Roos Launchbury ◽  
Armando Del Rio
Keyword(s):  
Design Process ◽  
Current Trend ◽  
Turbulence Models ◽  
Stability Limit ◽  
Transport Equations ◽  
Stability And Convergence ◽  
Operating Characteristics ◽  
Convergence Behavior ◽  
Anisotropic Turbulence ◽  
Rans Models

Abstract The current trend in turbomachinery towards broader operating characteristics requires that operating points in the off-design region can be captured accordingly from the simulation models. Complex processes like separation and vortex formation/dissipation occur under these conditions. Linear two equation models are often not able to represent these effects correctly since their derivation is based on over-simplifications, such as the Boussinesq hypothesis, which makes it impossible to capture anisotropic turbulence. Advanced RANS models are usually not considered in the design process of turbomachines because (1) they are usually more delicate with regards to stability and convergence behavior and (2) require additional computational effort. To make the usage of advanced RANS models more applicable for complex turbomachinery simulations a selected group of models were implemented into a robust framework of a pressure-based fully coupled solver. To further enhance stability, coupling terms between the turbulent transport equations were derived for several models. Anisotropic turbulence is introduced by computing an algebraic expression or by solving the transport equations for the Reynolds stress components. The evaluation of the models is performed on the RWTH Aachen “Radiver” centrifugal compressor case with vaned diffuser. For design conditions and operation points near the stability limit, all investigated turbulence models predict the compressor characteristic. Operation points in the choking region on the other hand are only predicted well by anisotropic models. The good results and improved convergence behavior of the advanced RANS models clearly indicates their applicability in the design process of turbomachines.

scholarly journals Effects of plies orientations and initial geometric imperfections on buckling strength of a composite stiffened panel

2018 ◽  
Vol 191 ◽  
pp. 00008
Author(s):  
Ikram Feddal ◽  
Abdellatif Khamlichi ◽  
Koutaiba Ameziane
Keyword(s):  
Stiffened Panel ◽  
Buckling Mode ◽  
Element Analysis ◽  
Geometric Imperfections ◽  
Stiffened Panels ◽  
Specific Strength ◽  
Euler Buckling ◽  
Buckling Behavior ◽  
Composite Stiffened Panel ◽  
Strength And Stiffness

The use of composite stiffened panels is common in several activities such as aerospace, marine and civil engineering. The biggest advantage of the composite materials is their high specific strength and stiffness ratios, coupled with weight reduction compared to conventional materials. However, any structural system may reach its limit and buckle under extreme circumstances by a progressive local failure of components. Moreover, stiffened panels are usually assembled from elementary parts. This affects the geometric as well as the material properties resulting in a considerable sensitivity to buckling phenomenon. In this work, the buckling behavior of a composite stiffened panel made from carbon Epoxy Prepregs is studied by using the finite element analysis under Abaqus software package. Different plies orientations sets were considered. The initial distributed geometric imperfections were modeled by means of the first Euler buckling mode. The nonlinear Riks method of analysis provided by Abaqus was applied. This method enables to predict more consistently unstable geometrically nonlinear induced collapse of a structure by detecting potential limit points during the loading history. It was found that plies orientations of the composite and the presence of geometric imperfections have huge influence on the strength resistance.

scholarly journals Standardization and integration of the airport master plan design process

2018 ◽  
Vol 2018 (12) ◽  
pp. 77-86
Author(s):  
Michał Kozłowski
Keyword(s):  
Design Process ◽  
Dynamic Process ◽  
Practical Experience ◽  
Master Plan ◽  
Airport Management ◽  
Quality Of Results ◽  
The Subject ◽  
Effectiveness And Efficiency ◽  
Standard Documents

The article presents the conclusion of the practical experience as well as the results of the author's research in the field of airport management, formulated in the context of the implementation of the investment of the Central Polish Airport. The subject of the considerations and implications is the process of designing the Airport Master Plan – AMP, which in the current situation should be modified in order to ensure effectiveness and efficiency of implementation and quality of results. At the beginning, AMP was characterized on the basis of a study concerning legal acts and selected standard documents, and a study of the quality and risk issues of the AMP was carried out. On the basis of the results obtained, conclusions have been formulated regarding the need for standardization and integration of the dynamic process of AMP design.

scholarly journals The Prediction of Buckling Load of Laminated Composite Hat-Stiffened Panels Under Compressive Loading by Using of Neural Networks

2018 ◽  
Vol 12 (1) ◽  
pp. 468-480 ◽  
Author(s):  
Shashi Kumar ◽  
Rajesh Kumar ◽  
Sasankasekhar Mandal ◽  
Atul K. Rahul
Keyword(s):  
Neural Network ◽  
Finite Element ◽  
Network Architecture ◽  
Laminated Composite ◽  
Buckling Load ◽  
Stiffened Panel ◽  
Stiffness Ratio ◽  
Data Set ◽  
Stiffened Panels ◽  
Structural Problems

Background:Stiffened panels are being used as a lightweight structure in aerospace, marine engineering and retrofitting of building and bridge structure. In this paper, two efficient analytical computational tools, namely, Finite Element Analysis (FEA) and Artificial Neural Network (ANN) are used to analyze and compare the results of the laminated composite 750-hat-stiffened panels.Objective:Finite Element (FE) is an efficient and versatile method for the analysis of a complex problem. FE models have been used to generate data set of four different parameters. The four parameters are extensional stiffness ratio of skin in the longitudinal direction to the transverse direction, orthotropy ratio of the panel, the ratio of twisting stiffness to transverse flexural stiffness and smeared extensional stiffness ratio of stiffeners to that of the plate.Results and Conclusion:For training of ANN, multilayer feedforward back-propagation has been used as a network function with two-hidden layers in the neural network. The good network architecture is achieved after several iterations to predict the buckling load of the stiffened panel. ANN prediction for unknown new data set is in good agreement with FEA results of different cases, which show that ANN tool can be used for the design of complex structural problems in civil engineering and optimization of the laminated composite stiffened panel.

The Effective Use of Experimental and Numerical Data for Validating Simplified Expressions of Stiffened Steel Panel Ultimate Compressive Strength

2007 ◽  
Vol 44 (02) ◽  
pp. 93-105
Author(s):  
Jeom Kee Paik
Keyword(s):  
Experimental Data ◽  
Compressive Strength ◽  
Numerical Data ◽  
Numerical Results ◽  
Design Code ◽  
Stiffened Panels ◽  
Collapse Mode ◽  
Effective Use ◽  
Stiffened Steel ◽  
Sophisticated Analysis

To study the accuracy of simplified formulations for prediction of the ultimate strength of longitudinally stiffened panels under uniaxial compression, the preferred approach is to compare them with available experimental data or numerical results from more sophisticated analysis procedures. Such studies are necessary in the development of both design code calibrations and reliability analysis procedures. Existing experimental data and numerical results useful for this purpose are first collected. Salient features of existing design formulations for compressive strength are then reviewed. Selected formulations are compared with the experimental data/numerical results. It is illustrated that there can be a significant amount of scatter in strength estimates by any one formulation and among formulations. The reasons for such scatter are discussed, with the emphasis on the collapse mode(s) involved, the effective width of plating, initial imperfections, and rotational restraints due to stiffening. The experimental and numerical strength data collected are documented for convenience of future use by other investigators.

A Decomposition Method for Concurrent Design of Mixed Discrete/Continuous Systems

1993 ◽  
Author(s):  
Jeffrey M. Ford ◽  
Christina L. Bloebaum
Keyword(s):  
Design Process ◽  
Decomposition Method ◽  
Organizational Design ◽  
Method Development ◽  
Minimum Weight ◽  
Optimization Methods ◽  
Continuous Systems ◽  
Computationally Efficient ◽  
Subspace Optimization ◽  
Design Variables

Abstract Interest in Concurrent Engineering (CE) has increased as industry looks for more efficient means of product design. Design optimization methods that facilitate the CE approach are an important aspect of current research. Among the methods that have been proposed is the Concurrent Subspace Optimization (CSSO) method, which allows the optimization problem to be decomposed into coupled subproblems. These subproblems may correspond to the different disciplines involved in the design process or to participating organizational design or manufacturing groups. The decomposition allows each discipline to apply their own optimization criteria to the problem. While this method may not be as computationally efficient as other methods, it allows the design process to conform to the departmental divisions that already exist in industry. The method development to date has focused on continuous systems only. However, problems that can not be modeled as continuous systems, such as those involving the placement of active controllers in CSI applications, would benefit from a method that allows the use of discrete parameters. The paper presents a decomposition method (based on CSSO) for the optimal design of mixed discrete/continuous systems. The method is applied to the design of a composite plate for minimum weight, with design variables contributed from sizing variables (continuous) and material combinations (discrete).

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