Speeding Up Topology Optimization of Compliant Mechanisms With a Pseudorigid-Body Model

2017 ◽  
Vol 9 (4) ◽  
Author(s):  
Venkatasubramanian Kalpathy Venkiteswaran ◽  
Omer Anil Turkkan ◽  
Hai-Jun Su
Keyword(s):  
Finite Element ◽  
Topology Optimization ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Solution Process ◽  
Beam Theory ◽  
Algebraic Equations ◽  
Element Analysis ◽  
System Equations ◽  
Kinematic Loops

This paper seeks to speed up the topology optimization using a pseudorigid-body (PRB) model, which allows the kinetostatic equations to be explicitly represented in the form of nonlinear algebraic equations. PRB models can not only accommodate large deformations but more importantly reduce the number of variables compared to beam theory or finite element methods. A symmetric 3R model is developed and used to represent the beams in a compliant mechanism. The design space is divided into rectangular segments, while kinematic and static equations are derived using kinematic loops. The use of the gradient and hessian of the system equations leads to a faster solution process. Integer variables are used for developing the adjacency matrix, which is optimized by a genetic algorithm. Dynamic penalty functions describe the general and case-specific constraints. The effectiveness of the approach is demonstrated with the examples of a displacement inverter and a crimping mechanism. The approach outlined here is also capable of estimating the stress in the mechanism which was validated by comparing against finite element analysis. Future implementations of this method will incorporate other pseudorigid-body models for various types of compliant elements and also try to develop multimaterial designs.

Compliant Mechanism Design Through Topology Optimization Using Pseudo-Rigid-Body Models

2016 ◽  
Author(s):  
Venkatasubramanian Kalpathy Venkiteswaran ◽  
Omer Anil Turkkan ◽  
Hai-Jun Su
Keyword(s):  
Finite Element ◽  
Topology Optimization ◽  
Rigid Body ◽  
Finite Element Methods ◽  
Compliant Mechanism ◽  
Beam Theory ◽  
Deformation Analysis ◽  
Optimization Approach ◽  
Algebraic Equations ◽  
Kinematic Loops

The initial design of compliant mechanisms for a specific application can be a challenging task. This paper introduces a topology optimization approach for planar mechanisms based on graph theory. It utilizes pseudo-rigid-body models, which allow the kinetostatic equations to be represented as nonlinear algebraic equations. This reduces the complexity of the system compared to beam theory or finite element methods, and has the ability to incorporate large deformations. Integer variables are used for developing the adjacency matrix, which is optimized by a genetic algorithm. Dynamic penalty functions describe the general and case-specific constraints. A symmetric 3R model is used to represent the beams in the mechanism. The design space is divided into rectangular segments while kinematic and static equations are derived using kinematic loops. The effectiveness of the approach is demonstrated with the example of an inverter mechanism. The results are compared against finite element methods to prove the validity of the new model as well as the accuracy of the approach outlined here. Future implementations of this method will include stress and deformation analysis and also introduce multi-material designs using different pseudo-rigid-body models.

Bistable Compliant Four-Bar Mechanisms With a Single Torsional Spring

2006 ◽  
Author(s):  
Adarsh Mavanthoor ◽  
Ashok Midha
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Mechanism Design ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Stored Energy ◽  
Element Analysis ◽  
Bistable Behavior ◽  
Torsional Spring ◽  
Bistable Mechanism

Significant reduction in cost and time of bistable mechanism design can be achieved by understanding their bistable behavior. This paper presents bistable compliant mechanisms whose pseudo-rigid-body models (PRBM) are four-bar mechanisms with a torsional spring. Stable and unstable equilibrium positions are calculated for such four-bar mechanisms, defining their bistable behavior for all possible permutations of torsional spring locations. Finite Element Analysis (FEA) and simulation is used to illustrate the bistable behavior of a compliant mechanism with a straight compliant member, using stored energy plots. These results, along with the four-bar and the compliant mechanism information, can then be used to design a bistable compliant mechanism to meet specified requirements.

Mechanical Behaviour of Auxetic Microstructures Using Contact Mechanics and Elastoplasticity

2016 ◽  
Vol 681 ◽  
pp. 100-116
Author(s):  
Georgios A. Drosopoulos ◽  
Nikolaos Kaminakis ◽  
Nikoletta Papadogianni ◽  
Georgios E. Stavroulakis
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Topology Optimization ◽  
Contact Mechanics ◽  
Compliant Mechanisms ◽  
Nonlinear Finite Element Analysis ◽  
Nonlinear Finite Element ◽  
Numerical Homogenization ◽  
Element Analysis ◽  
Optimization Formulation

The design of novel mechanical microstructures having auxetic behaviour is proposed in this paper using techniques of topology optimization for compliant mechanisms. The resulting microstructure can be modified in order to cover additional needs, not included in the topology optimization formulation. Classical structural optimization, contact mechanics, homogenization and nonlinear finite element analysis are used for this step. Thus, the modified microstructure or composite is studied with numerical homogenization in order to verify that it still has the wished auxetic behaviour. Finally, nonlinear finite element analysis shows how the auxetic behaviour is influenced by unilateral contact between the constituent materials, large displacements and elastoplasticity.

scholarly journals Investigation of Circular Flexural Hinge Used in Compliant Mechanism Using FEA Tool.

2016 ◽  
Vol 3 (1) ◽  
pp. 34-42
Author(s):  
M. M. Sawant ◽  
P. R. Anerao
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Fatigue Life ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Flexure Hinge ◽  
Experimental Setup ◽  
Element Analysis ◽  
Flexural Hinges ◽  
Improve Fatigue

To reduce fatigue failure of compliant mechanism, it is necessary to design and analyze the flexure hinge parametrically. A methodology to design a flexural hinges for compliant mechanism is proposed in this paper to improve fatigue life. Results obtained by finite element analysis shows that used design equations are reliable and easier to be used in the design of such proportion flexural hinges. The proposed analytical model gives a new viewpoint on the design of circular flexure hinge based compliant mechanisms. Circular flexural joint was manufactured by using Al 6061 T6 material and experimental setup is developed to test this flexural hinge. Results obtained by FEA were found to be in good correlation with experimental results. The variation in the results can be attributed to variation in properties of material, actual dimensions of setup etc.

scholarly journals Multiresolution Topology Optimization of Large-Deformation Path-Generation Compliant Mechanisms with Stress Constraints

2021 ◽  
Vol 11 (6) ◽  
pp. 2479
Author(s):  
Joseph Reinisch ◽  
Erich Wehrle ◽  
Johannes Achleitner
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Topology Optimization ◽  
Compliant Mechanisms ◽  
Nonlinear Finite Element Analysis ◽  
Stress Constraints ◽  
Nonlinear Finite Element ◽  
Path Generation ◽  
Element Analysis ◽  
Multiresolution Topology Optimization

Topology optimization is a powerful numerical tool in the synthesis of lightweight structures and compliant mechanisms. Compliant mechanisms present challenges for topology optimization, as they typically exhibit large displacements and rotations. Path-generation mechanisms are a class of mechanisms that are designed to follow an exact path. The characteristics of compliant mechanisms therefore exclude the validity of linear finite-element analysis to ensure the proper modeling of deformation and stresses. As stresses can exceed the limit when neglected, stress constraints are needed in the synthesis of compliant mechanisms. Both nonlinear finite-element analysis as well as the consideration of stress constraints significantly increase computational cost of topology optimization. Multiresolution topology optimization, which employs different levels of discretization for the finite-element analysis and the representation of the material distribution, allows an important reduction of computational effort. A multiresolution topology optimization methodology is proposed integrating stress constraints based on nonlinear finite-element analysis for path-generation mechanisms. Two objective formulations are used to motivate and validate this methodology: maximum-displacement mechanisms and path-generation mechanisms. The formulation of the stress constraints and their sensitivities within nonlinear finite-element analysis and multiresolution topology optimization are explained. We introduce two academic benchmark examples to demonstrate the results for each of the objective formulations. To show the practical, large-scale application of this method, results for the compliant mechanism structure of a droop-nose morphing wing concept are shown.

Design of a Single-Acting Constant-Force Actuator Based on Dielectric Elastomers

2008 ◽  
Author(s):  
Giovanni Berselli ◽  
Rocco Vertechy ◽  
Gabriele Vassura ◽  
Vincenzo Parenti Castelli
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Compliant Mechanism ◽  
Structural Parameters ◽  
Dielectric Elastomer ◽  
Constant Force ◽  
Element Analysis ◽  
Body Model ◽  
Rigid Body Model ◽  
Supporting Frame

The interest in actuators based on dielectric elastomer films as a promising technology in robotic and mechatronic applications is increasing. The overall actuator performances are influenced by the design of both the active film and the film supporting frame. This paper presents a single-acting actuator which is capable of supplying a constant force over a given range of motion. The actuator is obtained by coupling a rectangular film of silicone dielectric elastomer with a monolithic frame designed to suitably modify the force generated by the dielectric elastomer film. The frame is a fully compliant mechanism whose main structural parameters are calculated using a pseudo-rigid-body model and then verified by finite element analysis. Simulations show promising performance of the proposed actuator.

Natural frequency analysis of a functionally graded rotor-bearing system with a slant crack subjected to thermal gradients

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Arnab Bose ◽  
Prabhakar Sathujoda ◽  
Giacomo Canale
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Power Law ◽  
Beam Theory ◽  
Functionally Graded ◽  
Thermal Gradients ◽  
Element Analysis ◽  
Rotor Bearing ◽  
Natural Frequency Analysis ◽  
Bearing System

Abstract The present work aims to analyze the natural and whirl frequencies of a slant-cracked functionally graded rotor-bearing system using finite element analysis for the flexural vibrations. The functionally graded shaft is modelled using two nodded beam elements formulated using the Timoshenko beam theory. The flexibility matrix of a slant-cracked functionally graded shaft element has been derived using fracture mechanics concepts, which is further used to develop the stiffness matrix of a cracked element. Material properties are temperature and position-dependent and graded in a radial direction following power-law gradation. A Python code has been developed to carry out the complete finite element analysis to determine the Eigenvalues and Eigenvectors of a slant-cracked rotor subjected to different thermal gradients. The analysis investigates and further reveals significant effect of the power-law index and thermal gradients on the local flexibility coefficients of slant-cracked element and whirl natural frequencies of the cracked functionally graded rotor system.

Piezoelectric Actuator Performance Metrics and Relation to Compliant Mechanism Design

2001 ◽  
Author(s):  
Hima Maddisetty ◽  
Mary Frecker
Keyword(s):  
Topology Optimization ◽  
Performance Metrics ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Mechanical Efficiency ◽  
High Energy ◽  
High Energy Density ◽  
High Bandwidth ◽  
Compliant Mechanism Design ◽  
Actuator Performance

Abstract Piezoceramic actuators have gained widespread use due to their desirable qualities of high force, high bandwidth, and high energy density. Compliant mechanisms can be designed for maximum stroke amplification of piezoceramic actuators using topology optimization. In this paper, the mechanical efficiency and other performance metrics of such compliant mechanism/actuator systems are studied. Various definitions of efficiency and other performance metrics of actuators with amplification mechanisms from the literature are reviewed. These metrics are then applied to two compliant mechanism example problems and the effect of the stiffness of the external load is investigated.

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