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.

Optimum Design of Radial Drilling Machine Structure to Satisfy Static Rigidity and Natural Frequency Requirements

1983 ◽  
Vol 105 (2) ◽  
pp. 236-241 ◽  
Author(s):  
S. S. Rao ◽  
Ramana V. Grandhi
Keyword(s):  
Natural Frequency ◽  
Optimum Design ◽  
Minimum Weight ◽  
Drilling Machine ◽  
Cross Sectional ◽  
Design Variables ◽  
Static Rigidity ◽  
Weight Design ◽  
Radial Drilling ◽  
Machine Structure

A computational capability is developed for the optimum design of radial drilling machine structure to satisfy static rigidity and natural frequency requirements using finite element idealization. The radial drilling machine structure is idealized with frame elements and is analyzed by using different combinations of cross sectional shapes for the radial arm and the column. From the results obtained, the best combination of cross sectional shapes is suggested for the structure. With this combination of cross sectional shapes, mathematical programming techniques are used to find the minimum weight design of the radial drilling machine structure. A sensitivity analysis is conducted about the optimum point to find the effects of changes in design variables on the structural weight and the response quantities.

A fast multiobjective optimization approach to S-duct scoop inlets design with both inflow and outflow

2018 ◽  
Vol 233 (9) ◽  
pp. 3381-3394
Author(s):  
Lifang Zeng ◽  
Dingyi Pan ◽  
Shangjun Ye ◽  
Xueming Shao
Keyword(s):  
Multiobjective Optimization ◽  
Total Pressure ◽  
Optimization Method ◽  
Navier Stokes ◽  
Integral Model ◽  
Optimization Approach ◽  
Navier Stokes Equation ◽  
Cross Sectional ◽  
Design Variables ◽  
Computational Fluid Dynamics Analysis

A fast multiobjective optimization method for S-duct scoop inlets considering both inflow and outflow is developed and validated. To reduce computation consumption of optimization, a simplified efficient model is proposed, in which only inflow region is simulated. Inlet pressure boundary condition of the efficient model is specified by solving an integral model with both inflow and outflow. An automated optimization system integrating the computational fluid dynamics analysis, nonuniform rational B-spline geometric representation technique, and nondominated sorting genetic algorithm II is developed to minimize the total pressure loss and distortion at the exit of diffuser. Flow field is numerically simulated by solving the Reynolds-averaged Navier–Stokes equation coupled with k–ω shear stress transport turbulence model, and results are validated to agree well with previous experiment. S-duct centreline shape and cross-sectional area distribution are parameterized as the design variables. By analyzing the results of a suggested optimal inlet chosen from the obtained Pareto front, total pressure recovery has increased from 97% to 97.4%, and total pressure distortion DC60 has decreased by 0.0477 (21.7% of the origin) at designed Mach number 0.7. The simplified efficient model has been validated to be reliable, and by which the time cost for the optimization project has been reduced by 70%.

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.

Analytic Treatment of Minimum Weight Design of Cantilevers

1974 ◽  
Vol 41 (2) ◽  
pp. 512-515
Author(s):  
J. E. Brock
Keyword(s):  
Analytic Solution ◽  
Minimum Weight ◽  
Practical Importance ◽  
Cantilever Beams ◽  
Minimum Weight Design ◽  
Concentrated Force ◽  
Cross Sectional ◽  
Section Modulus ◽  
End Conditions ◽  
Weight Design

Minimum weight design is considered for cantilever beams which must sustain a concentrated moment and a concentrated force at the tip as well as their own distributed weight. An analytic solution is obtained for the case where the variation of cross section is such that section modulus varies as a power of cross-sectional area. Three cases, having practical importance, are studied in detail; two of these lead to nonlinear differential or integral relationships. Cases having more complicated laws of variation and other end conditions are discussed.

Optimal design of nonlinear large-scale suspendome using cascade optimization

2017 ◽  
Vol 33 (1) ◽  
pp. 3-18 ◽  
Author(s):  
Ali Kaveh ◽  
Masoud Rezaei ◽  
MR Shiravand
Keyword(s):  
Optimal Design ◽  
Large Scale ◽  
Simple Procedure ◽  
Geometry Optimization ◽  
Steel Structures ◽  
Optimization Method ◽  
Scale Space ◽  
Cross Sectional ◽  
Colliding Bodies Optimization ◽  
Design Variables

Large-scale suspendomes are elegant architectural structures which cover a vast area with no interrupting columns in the middle. These domes have attractive shapes which are also economical. Domes are built in a wide variety of forms. In this article, an algorithm is developed for optimum design of domes considering the topology, geometry, and size of member section using the cascade-enhanced colliding bodies optimization method. In large-scale space steel structures, a large number of design variables are involved. The idea of cascade optimization allows a single optimization problem to be tackled in a number of successive autonomous optimization stages. The variables are the optimum height of crown and tubular sections of these domes, the initial strain, the length of the struts, and the cross-sectional areas of the cables in the tensegrity system of domes. The number of joints in each ring and the number of rings are considered for topology optimization of ribbed and Schwedler domes. Weight of the dome is taken as the objective function for minimization. A simple procedure is defined to determine the configuration of the domes. The design constraints are considered according to the provisions of Load and Resistance Factor Design–American Institute of Steel Constitution. In order to investigate the efficiency of the presented method, a large-scale suspendome with more than 2266 members is investigated. Numerical results show that the utilized method is an efficient tool for optimal design of large-scale domes. Additionally, in this article, a topology and geometry optimization for two common ribbed and Schwedler domes are performed to find their optimum graphs considering various spans.

Minimum Weight Design Problems of Fiber-Reinforced Beam Subjected to Uniform Bending

1985 ◽  
Vol 107 (1) ◽  
pp. 88-93 ◽  
Author(s):  
Juhachi Oda
Keyword(s):  
Minimum Weight ◽  
Bending Moment ◽  
Material Strength ◽  
Sequential Linear Programming ◽  
Volume Percent ◽  
Fiber Volume ◽  
Minimum Weight Design ◽  
Design Problems ◽  
Design Variables ◽  
Weight Design

Problems considered here are that of minimizing the weight of beams, which are subjected to a uniform bending moment and reinforced by the fibers distributed in the direction of beam axis. The beam is simplified as a multilaminate structure, of which the fiber volume percent Vfi of each lamina is considered as the design variables. To formulate this design problem the bending theory of multilaminate beam and the law of mixture for the composite material strength are applied. Furthermore, the sequential linear programming and the sequential unconstrianed minimization techniques are used to obtain the design solutions numerically.

scholarly journals Optimal Mass Design of 25 Bars Truss with Loading Conditions on Five Node Elements

2019 ◽  
Vol 4 (1) ◽  
pp. 1-16 ◽  
Author(s):  
Koumbe Mbock ◽  
Etoua Remy Magloire ◽  
Lezin Seba Minsili ◽  
Okpwe Mbarga Richard
Keyword(s):  
Minimum Weight ◽  
Elastic Model ◽  
Loading Conditions ◽  
Cross Sectional ◽  
Linear Elastic ◽  
Space Truss ◽  
Mass Minimization ◽  
Internal Forces ◽  
Minimum Displacement ◽  
Weight Design

The optimal design of a twenty-five bar space truss commonly involves multiple loading conditions acting on 4 node elements in the linear elastic model. In this paper, we describe the behavior of the truss system with our experimental loading conditions on five node elements subject to minimum displacement and stresses that are used to formulate the constrained nonlinear optimization problem. Numerical computations are developed with the objective of mass minimization and the best structural design is selected by applying the interior point method with the guidance of Matlab Optimization Toolbox. Our numerical results show the optimal values of cross-sectional areas, material densities, and internal forces which satisfy the minimum weight design. These results provide the appropriate mass to the experimental data and allow substantial changes in size, shape, and topology.

Minimum-Weight Design of Stiffened Cylinders Under Hydrostatic Pressure

1977 ◽  
Vol 21 (04) ◽  
pp. 217-224
Author(s):  
G. J. Simitses ◽  
M. Aswani
Keyword(s):  
Hydrostatic Pressure ◽  
Objective Function ◽  
Failure Modes ◽  
Minimum Weight ◽  
Minimum Weight Design ◽  
Design Charts ◽  
Design Variables ◽  
Weight Penalty ◽  
Weight Design ◽  
Two Stages

A methodology is developed by which one may design a stiffened cylinder of specified material, radius and length such that it can carry safely a given hydrostatic pressure with minimum weight. The solution is accomplished in two stages. First, design charts based on a simplified formulation of the objective function are obtained. Second, these design charts are used to evaluate the design variables. Such an approach enables the designer to introduce needed changes or avoid interaction of failure modes by paying the least weight penalty. Design examples are presented and the results are compared with those obtained by other investigators.

scholarly journals Design Optimization of Composite Laminated Tube Based on Improved Niching Evolutionary Algorithm

2017 ◽  
Vol 2017 ◽  
pp. 1-11 ◽  
Author(s):  
Sen Ma ◽  
Qilin Zhao ◽  
Darong Pan
Keyword(s):  
Optimal Design ◽  
Evolutionary Algorithms ◽  
Objective Function ◽  
Evolutionary Algorithm ◽  
Minimum Weight ◽  
Local Optimum ◽  
Optimal Result ◽  
Minimum Weight Design ◽  
Design Variables ◽  
Weight Design

A minimum weight design is developed for a composite laminated tube considering the number of plies as one of the design variables. The objective function is found to be complex, and more than one optimal design point may exist with different numbers of plies. Existing methods based on evolutionary algorithms tend to become trapped around a local optimum and can find no more than one optimal result per calculation. Aiming at the characteristics of the objective function, an improved evolutionary algorithm (INDE for short) is established based on niching technology. The formula for calculating the distance between individuals in the niching technology is improved to satisfy the minimum weight design for the composite laminated tube. As a result, the improved niching evolutionary algorithm offers better global search ability and can find more than one optimal result per calculation for different numbers of plies.

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