Bending of lightweight circular tubes

2017 ◽  
Vol 232 (7) ◽  
pp. 1165-1178 ◽  
Author(s):  
G Mastinu ◽  
G Previati ◽  
M Gobbi
Keyword(s):  
Lightweight Design ◽  
Analytical Form ◽  
Upper And Lower Bounds ◽  
Concept Design ◽  
Optimal Solutions ◽  
Lightweight Construction ◽  
Linear Elastic ◽  
Design Variables ◽  
Maximum Stiffness ◽  
Linear Elastic Theory

The concept design (sizing) of thin-walled tubes subject to bending is dealt by resorting to rigorous design principles pertaining to engineering science. Multi-objective optimization is the proper theory that has been exploited. Minimum mass and maximum stiffness (minimum compliance) are the optimization objectives. Safety (admissible stress), stability (buckling), available room (external radius of the tube), and thickness of the tube (arising from technological issues) are introduced as constraints. Linear elastic theory is used. Optimal solutions are given in analytical form for a prompt use by designers. Such optimal solutions refer both to the objectives (mass and compliance) and to the design variables (radius and thickness of the tube). The best attainable lightweight design is discussed as a function of the constraints. In particular, given the upper and lower bounds for radius and thickness respectively, three candidate optimal solutions are addressed in the paper for concept design purposes. The comparative lightweight design of tubes made from different materials is presented. Contrary with respect to the reputation of aluminum for effective lightweight construction, steel can be the best choice, when the available room has to be saturated.

scholarly journals Thermal-Structural Design of Actively-Cooled Panels Reinforced by Light-Weight Truss Cores

2013 ◽  
Author(s):  
Hongwei Song ◽  
Mingjun Li ◽  
Chenguang Huang ◽  
Xi Wang
Keyword(s):  
Heat Transfer ◽  
Structural Analysis ◽  
Convective Heat Transfer ◽  
Convective Heat ◽  
Thermal Environment ◽  
Numerical Models ◽  
Lightweight Design ◽  
Optimization Procedure ◽  
Combustion Gas ◽  
Design Variables

This paper focuses on thermal-structural analysis and lightweight design of actively-cooled panels reinforced by low density lattice-framed material (LFM) truss cores. Numerical models for actively-cooled panels are built up with parametric codes to perform the coupled thermal-structural analysis, considering the internal thermal environment of convective heat transfer in the combustor and convective heat transfer in the cooling channel, and internal pressures from the combustion gas and the coolant. A preliminary comparison of the LFM truss reinforced actively-cooled panel and the non-reinforced panel demonstrates that the thermal-structural behavior is significantly improved. Then, an optimization procedure is carried out to find the lightest design while satisfying thermal deformation and plastic strain constraints, with thicknesses of face sheets and topology parameters of LFM truss as design variables. The optimization result demonstrates that, compared with the non-reinforced actively-cooled panels, weight reduction for the panel reinforced by LFM truss may reach 19.6%. We have also fabricated this type of actively-cooled panel in the laboratory level, and the specimen shows good mechanical behaviors.

Multi Objective Design Optimization of Two Bar Truss Using NSGA II and TOPSIS

2014 ◽  
Vol 984-985 ◽  
pp. 419-424
Author(s):  
P. Sabarinath ◽  
M.R. Thansekhar ◽  
R. Saravanan
Keyword(s):  
Design Optimization ◽  
Optimization Problems ◽  
Optimization Methods ◽  
Optimal Solutions ◽  
Objective Functions ◽  
Nsga Ii ◽  
Multi Objective ◽  
Total Displacement ◽  
Design Variables ◽  
Conflicting Objectives

Arriving optimal solutions is one of the important tasks in engineering design. Many real-world design optimization problems involve multiple conflicting objectives. The design variables are of continuous or discrete in nature. In general, for solving Multi Objective Optimization methods weight method is preferred. In this method, all the objective functions are converted into a single objective function by assigning suitable weights to each objective functions. The main drawback lies in the selection of proper weights. Recently, evolutionary algorithms are used to find the nondominated optimal solutions called as Pareto optimal front in a single run. In recent years, Non-dominated Sorting Genetic Algorithm II (NSGA-II) finds increasing applications in solving multi objective problems comprising of conflicting objectives because of low computational requirements, elitism and parameter-less sharing approach. In this work, we propose a methodology which integrates NSGA-II and Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) for solving a two bar truss problem. NSGA-II searches for the Pareto set where two bar truss is evaluated in terms of minimizing the weight of the truss and minimizing the total displacement of the joint under the given load. Subsequently, TOPSIS selects the best compromise solution.

A New Dynamic Basis Algorithm for Solving Linear Programming Problems for Engineering Design

1988 ◽  
Author(s):  
Y. Wang ◽  
E. Sandgren
Keyword(s):  
Linear Programming ◽  
Simplex Method ◽  
Inequality Constraints ◽  
Upper And Lower Bounds ◽  
Programming Algorithm ◽  
Active Constraint ◽  
Design Variables ◽  
Artificial Variable ◽  
Linear Programming Problems ◽  
Revised Simplex Method

Abstract A new linear programming algorithm is proposed which has significant advantages compared to the traditional simplex method. The search direction generated which is always along a common edge of the active constraint set, is used to locate candidate constraints, and can be used to modify the current basis. The dimension of the basis begins at one and dynamically increases but remains less than or equal to the number of design variables. This is true regardless of the number of inequality constraints present including upper and lower bounds. The proposed method can operate equally well from a feasible or infeasible point. The pivot operation and artificial variable strategy of the simplex method are not used. Examples are presented and results are compared with a traditional revised simplex method.

Multiobjective Weighting Selection for Optimization-Based Control Design

1997 ◽  
Vol 122 (3) ◽  
pp. 567-569 ◽  
Author(s):  
Ricardo H. C. Takahashi ◽  
Juan F. Camino and ◽  
Douglas E. Zampieri ◽  
Pedro L. D. Peres
Keyword(s):  
Control Design ◽  
Active Suspension ◽  
Pareto Optimal ◽  
Pareto Optimal Solutions ◽  
Optimal Solutions ◽  
Cost Functional ◽  
Design Variables ◽  
Optimal Controllers ◽  
Selection For ◽  
Multiobjective Design

A methodology for the multiobjective design of controllers is presented, motivated by the problem of designing an active suspension controller. This problem has, as a particular feature, the possibility of being defined with two design variables only. The multiobjective controller is searched inside the space of “optimal controllers” defined by a weighted cost functional. The weightings are taken as the optimization variables for the multiobjective design. The method leads to (local) Pareto-optimal solutions and allows the direct specification of controller constraints in terms of some primary objectives which are taken into account in the multiobjective search. [S0022-0434(00)01403-9]

Lightweight Design of the Welded Beam of Machining Center Based on Topology Optimization

2016 ◽  
Vol 836-837 ◽  
pp. 326-332
Author(s):  
Qin Sun ◽  
Zuo Li Li ◽  
Hui Yu ◽  
Yang Liu ◽  
Jin Sheng Zhang
Keyword(s):  
Topology Optimization ◽  
Natural Frequencies ◽  
Lightweight Design ◽  
Element Model ◽  
Machining Process ◽  
Mode Shapes ◽  
Cutting Condition ◽  
Machining Center ◽  
Maximum Stiffness ◽  
Stiffness Design

From the perspective of statics, the deformation of welded beam under the action of gravity and cutting force was studied in the paper. During the actual machining process, vibration of welded beam and even the machine can be caused due to the change of cutting condition and interference from the outside. To avoid the natural frequency, and prevent the occurrence of resonance phenomena, welded beam modal was further analyzed; the first six natural frequencies and mode shapes of the beam were achieved. Statics and modal analysis are the basis of lightweight design of the welded beam based on topology optimization. The topology optimization model of maximum stiffness design and eigenvalue problem structural dynamics was established. Finite element model of beam and its components was established in hypermesh, and the optimization objective function, constraint function and boundary conditions were also set. Compared with the structure before optimization, the weight of the beam was reduced 10%, the lightweight design of the welded beam was achieved and the comprehensive performance of the beam was significantly improved.

A New Dynamic Basis Algorithm for Solving Linear Programming Problems for Engineering Design

1990 ◽  
Vol 112 (2) ◽  
pp. 208-214 ◽  
Author(s):  
Y. Wang ◽  
E. Sandgren
Keyword(s):  
Linear Programming ◽  
Simplex Method ◽  
Inequality Constraints ◽  
Simplex Algorithm ◽  
Upper And Lower Bounds ◽  
Programming Algorithm ◽  
Single Element ◽  
Basis Matrix ◽  
Active Constraint ◽  
Design Variables

A new linear programming algorithm is proposed which has significant advantages compared to a traditional simplex method. A search direction is generated along a common edge of the active constraint set. This direction is followed in order to identify candidate constraints and to modify the current basis. The dimension of the basis matrix begins with a single element and dynamically increases but remains less than or equal to the number of design variables. This is true regardless of the number of inequality constraints present including upper and lower bounds. The proposed method can operate equally well from a feasible or infeasible point. The pivot operation and artificial variable strategy of the simplex method are not used. Examples are presented and results are compared to those generated by a traditional revised simplex algorithm. Extensions are presented for both exterior and interior versions of the approach.

scholarly journals An Automated Structural Optimisation Methodology for Scissor Structures Using a Genetic Algorithm

2017 ◽  
Vol 2017 ◽  
pp. 1-13 ◽  
Author(s):  
Aushim Koumar ◽  
Tine Tysmans ◽  
Rajan Filomeno Coelho ◽  
Niels De Temmerman
Keyword(s):  
Genetic Algorithms ◽  
Search Space ◽  
Optimal Solutions ◽  
Multiobjective Optimisation ◽  
Nsga Ii ◽  
Design Variables ◽  
Depth Analysis ◽  
Making Choices ◽  
Optimisation Methods ◽  
Number Of Individuals

We developed a fully automated multiobjective optimisation framework using genetic algorithms to generate a range of optimal barrel vault scissor structures. Compared to other optimisation methods, genetic algorithms are more robust and efficient when dealing with multiobjective optimisation problems and provide a better view of the search space while reducing the chance to be stuck in a local minimum. The novelty of this work is the application and validation (using metrics) of genetic algorithms for the shape and size optimisation of scissor structures, which has not been done so far for two objectives. We tested the feasibility and capacity of the methodology by optimising a 6 m span barrel vault to weight and compactness and by obtaining optimal solutions in an efficient way using NSGA-II. This paper presents the framework and the results of the case study. The in-depth analysis of the influence of the optimisation variables on the results yields new insights which can help in making choices with regard to the design variables, the constraints, and the number of individuals and generations in order to obtain efficiently a trade-off of optimal solutions.

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