Topological and Geometric Synthesis of Compliant Mechanisms

2000 ◽  
Author(s):  
Joel A. Hetrick ◽  
Sridhar Kota
Keyword(s):  
Compliant Mechanisms ◽  
Programming Algorithm ◽  
Design Stage ◽  
Stable Convergence ◽  
Ground Structure ◽  
Element Analysis ◽  
Cross Section Area ◽  
Design Variables ◽  
Section Area ◽  
Geometric Variation

Abstract Structural optimization of compliant mechanisms is a systematic and automated approach for synthesizing the topology (layout) of mechanisms given the motion requirements. Here, two optimization approaches are presented: one employing a traditional full ground structure and one utilizing a modular ground structure whose nodes are allowed to wander within specified ranges. For problems discretized by many elements, the modular ground structure effectively reduces the number of design variables and speeds design convergence. In addition, relocation of node coordinates allows for geometric variation within the topology (layout) design stage. Linear finite element analysis using truss elements is utilized along with a sequential quadratic programming algorithm to optimize the mechanisms. Derivation of an efficiency based objective formulation is presented to determine the optimal mechanism design which satisfies motion requirements while maximizing the transfer of energy through the mechanism. Calculation of design derivatives with respect to element cross-section area and node position is performed using the adjoint variable method which provides faster and more stable convergence over finite difference approaches. Design examples are presented which directly compare the performance of topology optimized designs for the fixed node full ground structure to the floating node modular ground structure.

Adjoint-Based Multidisciplinary, Multipoint Optimization of a Radial Turbine Considering Aerodynamic and Structural Performances

2019 ◽  
Author(s):  
Lasse Mueller ◽  
Tom Verstraete ◽  
Marc Schwalbach
Keyword(s):  
Mechanical Stresses ◽  
Programming Algorithm ◽  
Navier Stokes ◽  
Analysis Tool ◽  
Element Analysis ◽  
Turbine Efficiency ◽  
Radial Turbine ◽  
Design Variables ◽  
Gradient Based ◽  
Adjoint Approach

Abstract This paper presents a multidisciplinary adjoint-based design optimization of a turbocharger radial turbine for automotive applications. The aim is to improve the total-to-static efficiency of the turbine while keeping mechanical stresses below a predefined limit. The search for the optimal design is accomplished using an efficient Sequential Quadratic Programming algorithm considering additional aerodynamic and manufacturing constraints. The aerodynamic performance of the wheel is evaluated by a Reynolds-Averaged Navier-Stokes solver, whereas the maximum stresses in the material are predicted by a Finite Element Analysis tool. The design gradients required by the optimizer are computed with the adjoint approach which provides sensitivity information largely independent of the number of design variables. The results presented in this paper show the clear need to take into account mechanical stresses during optimization, as they are the most restrictive design limitation. However, the gradient-based optimization algorithm is able to effectively keep the stress levels below the critical value while significantly improving the turbine efficiency in a few design cycles.

Optimal fiber orientation and topology design for compliant mechanisms with fiber-reinforced composites

2016 ◽  
Vol 231 (12) ◽  
pp. 2302-2312 ◽  
Author(s):  
Xinxing Tong ◽  
Wenjie Ge ◽  
Yonghong Zhang
Keyword(s):  
Fiber Orientation ◽  
Strain Energy ◽  
Compliant Mechanisms ◽  
Linear Optimization ◽  
Topology Design ◽  
Fiber Reinforced ◽  
Element Analysis ◽  
And Topology ◽  
Glass Fiber Reinforced ◽  
Design Variables

An approach for designing compliant mechanisms with glass fiber-reinforced epoxy materials is presented to obtain the optimum fiber orientation and topology structure simultaneously in this paper. Four-node hybrid stress elements and nodal design variables are adopted to suppress the islands and checkerboard phenomenon without additive filter technology and constraint. Taking fiber orientation and relative density as design variables, minimizing the weighted linear combination of the mutual strain energy and the strain energy is considered as objective function to achieve the desired deformation and enough load-carrying capacity of compliant mechanisms with the volume constraint. The displacement field of structure is obtained by the finite element analysis, and the non-linear optimization problem is solved via the well-known method of moving asymptotes. The numerical examples of designing compliant inverters and grippers with different weighted factors are investigated to demonstrate the effectiveness of the proposed method.

Size effects on compressive behaviors of three-dimensional braided composites under high strain rates

2018 ◽  
Vol 52 (28) ◽  
pp. 3895-3908 ◽  
Author(s):  
Tao Liu ◽  
Baozhong Sun ◽  
Bohong Gu
Keyword(s):  
Cross Section ◽  
Three Dimensional ◽  
Sample Length ◽  
Braided Composites ◽  
Element Analysis ◽  
Cross Section Area ◽  
Section Area ◽  
Unit Cells ◽  
Microstructure Model ◽  
The Cross

The compressive behaviors of three-dimensional braided composites with different cross sections and lengths along braided direction under high strain rates were reported from numerical simulations and experimental tests. The microstructure models with and without defects were established. The microstructure model with random distributed defects was to investigate the influence of sample length and random defects on the compressive properties. The microstructure model without defects is to reveal the effect of the cross section area on the compressive behavior. We found from finite element analysis that volume fractions of interior, surface, and corner unit cells vary with the cross section area. The strength and modulus were sensitive to the volume fractions of the unit cells and defects in the braided composites. The effect of the sample length on the compressive behaviors was not as significant as the cross section area and defects. The testing validated the finite element analysis results well.

Robust Mechanical Design Through Minimum Sensitivity

1989 ◽  
Author(s):  
A. D. Belegundu ◽  
S. Zhang
Keyword(s):  
Contact Pressure ◽  
Thermal Environment ◽  
Mechanical Design ◽  
Operating Temperature ◽  
Design Stage ◽  
Element Analysis ◽  
Uncertain Variables ◽  
Design Variables ◽  
Minimum Sensitivity ◽  
Selection Of

Abstract The problem of designing mechanical systems or components under uncertainty is considered. The basic idea is to ensure quality control at the design stage by minimizing sensitivity of the response to uncertain variables by proper selection of design variables. This formulation is applied to the design of a brass sleeve which is press fitted over a steel shaft in an uncertain thermal environment. The contact pressure is determined using finite element analysis. By optimizing the shape of the sleeve, the sensitivity of contact pressure with respect to operating temperature is reduced. The minimum sensitivity approach offers a straightforward procedure for robust design and can be implemented in a general manner. It is shown that reduction in sensitivity leads to increase in probability of safety.

Finite Element Modeling for Steel Cord Analysis in Radial Tires

2013 ◽  
Vol 41 (1) ◽  
pp. 60-79 ◽  
Author(s):  
Wei Yintao ◽  
Luo Yiwen ◽  
Miao Yiming ◽  
Chai Delong ◽  
Feng Xijin
Keyword(s):  
Finite Element ◽  
High Efficiency ◽  
Force Measurement ◽  
Three Dimensional ◽  
Local Stress ◽  
Tension Force ◽  
Center Line ◽  
Element Analysis ◽  
Design Variables ◽  
Steel Cord

ABSTRACT: This article focuses on steel cord deformation and force investigation within heavy-duty radial tires. Typical bending deformation and tension force distributions of steel reinforcement within a truck bus radial (TBR) tire have been obtained, and they provide useful input for the local scale modeling of the steel cord. The three-dimensional carpet plots of the cord force distribution within a TBR tire are presented. The carcass-bending curvature is derived from the deformation of the carcass center line. A high-efficiency modeling approach for layered multistrand cord structures has been developed that uses cord design variables such as lay angle, lay length, and radius of the strand center line as input. Several types of steel cord have been modeled using the developed method as an example. The pure tension for two cords and the combined tension bending under various loading conditions relevant to tire deformation have been simulated by a finite element analysis (FEA). Good agreement has been found between experimental and FEA-determined tension force-displacement curves, and the characteristic structural and plastic deformation phases have been revealed by the FE simulation. Furthermore, some interesting local stress and deformation patterns under combined tension and bending are found that have not been previously reported. In addition, an experimental cord force measurement approach is included in this article.

Multi-Objective Design Problem of Tire Wear and Visualization of Its Pareto Solutions2

2006 ◽  
Vol 34 (3) ◽  
pp. 170-194 ◽  
Author(s):  
M. Koishi ◽  
Z. Shida
Keyword(s):  
Inverse Problems ◽  
Conceptual Design ◽  
Dimensional Space ◽  
Design Stage ◽  
Objective Functions ◽  
Pareto Solutions ◽  
Design Problems ◽  
Multi Objective ◽  
Design Engineers ◽  
Design Variables

Abstract Since tires carry out many functions and many of them have tradeoffs, it is important to find the combination of design variables that satisfy well-balanced performance in conceptual design stage. To find a good design of tires is to solve the multi-objective design problems, i.e., inverse problems. However, due to the lack of suitable solution techniques, such problems are converted into a single-objective optimization problem before being solved. Therefore, it is difficult to find the Pareto solutions of multi-objective design problems of tires. Recently, multi-objective evolutionary algorithms have become popular in many fields to find the Pareto solutions. In this paper, we propose a design procedure to solve multi-objective design problems as the comprehensive solver of inverse problems. At first, a multi-objective genetic algorithm (MOGA) is employed to find the Pareto solutions of tire performance, which are in multi-dimensional space of objective functions. Response surface method is also used to evaluate objective functions in the optimization process and can reduce CPU time dramatically. In addition, a self-organizing map (SOM) proposed by Kohonen is used to map Pareto solutions from high-dimensional objective space onto two-dimensional space. Using SOM, design engineers see easily the Pareto solutions of tire performance and can find suitable design plans. The SOM can be considered as an inverse function that defines the relation between Pareto solutions and design variables. To demonstrate the procedure, tire tread design is conducted. The objective of design is to improve uneven wear and wear life for both the front tire and the rear tire of a passenger car. Wear performance is evaluated by finite element analysis (FEA). Response surface is obtained by the design of experiments and FEA. Using both MOGA and SOM, we obtain a map of Pareto solutions. We can find suitable design plans that satisfy well-balanced performance on the map called “multi-performance map.” It helps tire design engineers to make their decision in conceptual design stage.

EFFECT OF BEDLOAD SEDIMENT NATURAL COMPOSITION ON GEOMETRIC AND DINAMIC CHARACTERISTICS OF CHANNEL FORMS

2018 ◽  
pp. 36-39
Author(s):  
N Ikramov ◽  
T Majidov
Keyword(s):  
Research Work ◽  
Laboratory Data ◽  
Hydroelectric Station ◽  
Negative Consequences ◽  
Movement Velocity ◽  
Reservoir Volume ◽  
Pump Station ◽  
Cross Section Area ◽  
Section Area ◽  
Bedload Sediment

The article brings up data on sediment diversity at watercourse bed and on their movement in the form of ridges. The ridge form movement of sediment leads to the reduction of reservoir volume and canal cross section area, which has an effect on their carrying capacity, filling of pump station forechambers and hydroelectric station pressure basins with sediment. The presence of sediment in flow leads to abrasive deterioration of pumps, water motors and pressure pipes and to other negative consequences. Research work tasks on the study of these effects have been examined with the purpose of preventing such negative consequences. On the basis of laboratory data diagrams and relationships were obtained for ridge length, height and movement velocity vs. sediment hydraulic and geometric sizes.

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