Isogeometric Shape Optimization for Compliant Mechanisms With Prescribed Load Paths

2014 ◽  
Author(s):  
Giuseppe Radaelli ◽  
Just L. Herder
Keyword(s):  
Shape Optimization ◽  
Degrees Of Freedom ◽  
Compliant Mechanisms ◽  
Fiber Composite ◽  
Optimization Procedure ◽  
Linear Analysis ◽  
Carbon Fiber Composite ◽  
Shape Accuracy ◽  
Initial Shape ◽  
Load Paths

This paper presents a method for the design of compliant mechanisms with large deflections and prescribed load paths. While the approach is general, this paper treats the shape optimization for two dimensional beams. Due to the geometric non-linearity of the problem the non-linear analysis is nested into the optimization procedure. This requires accurate and efficient analysis of the structural problem. The analysis of the beam is based on the Isogeometric Analysis formulation, an alternative for conventional FEA especially appreciated for its shape-accuracy and efficiency. The method is applied to the synthesis of a balancer for a pendulum, which involves a two step load case: first a prestressing phase and subsequently a motion phase under the influence of gravity. To this end, a prestressed compliant beam was optimized with respect to its initial shape and the preload conditions. The rotationless character of the degrees of freedom of the Isogeometric beam requested the formulation of specific boundary conditions in order to apply rotations on the beam. The results of the shape optimization have been validated with a prototype out of carbon fiber composite material, which has been successfully tested. The experimental results are in agreement with the simulation results, with an error of 3%.

An Energy Formulation for Parametric Size and Shape Optimization of Compliant Mechanisms

1999 ◽  
Vol 121 (2) ◽  
pp. 229-234 ◽  
Author(s):  
J. A. Hetrick ◽  
S. Kota
Keyword(s):  
Shape Optimization ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Optimization Procedure ◽  
Stress Constraints ◽  
Optimization Techniques ◽  
Mechanical Transmission ◽  
Dimensional Synthesis ◽  
Size And Shape ◽  
Mechanical Devices

Compliant mechanisms are jointless mechanical devices that take advantage of elastic deformation to achieve a force or motion transformation. An important step toward automated design of compliant mechanisms has been the development of topology optimization techniques. The next logical step is to incorporate size and shape optimization to perform dimensional synthesis of the mechanism while simultaneously considering practical design specifications such as kinematic and stress constraints. An improved objective formulation based on maximizing the energy throughput of a linear static compliant mechanism is developed considering specific force and displacement operational requirements. Parametric finite element beam models are used to perform the size and shape optimization. This technique allows stress constraints to limit the maximum stress in the mechanism. In addition, constraints which restrict the kinematics of the mechanism are successfully applied to the optimization problem. Resulting optimized mechanisms exhibit efficient mechanical transmission and meet kinematic and stress requirements. Several examples are given to demonstrate the effectiveness of the optimization procedure.

Design and Fabrication of an Arm Exoskeleton for Aim Stabilization

2013 ◽  
Author(s):  
Daniel M. Baechle ◽  
Eric D. Wetzel ◽  
Sunil K. Agrawal
Keyword(s):  
Composite Materials ◽  
Carbon Fiber ◽  
Adaptive Algorithm ◽  
Degrees Of Freedom ◽  
Fiber Composite ◽  
Carbon Fiber Composite ◽  
Aiming Movements ◽  
Voluntary Motion ◽  
Fiber Composite Materials

Accurately aiming and firing a pistol requires a steady hand. While many devices can steady a shooter’s arm or hand by restricting movement or degrees-of-freedom, few devices actively reduce involuntary tremors while allowing larger voluntary aiming movements. This paper details the design and fabrication of an arm exoskeleton that can actively damp arm tremors while allowing voluntary aiming movements. The device allows five degrees-of-freedom and is very lightweight due to its cable-driven architecture and use of carbon fiber composite materials. Tremorous movement is filtered out from voluntary motion, and an adaptive algorithm provides a tremor-cancelling signal to the cable control motors.

scholarly journals Design and Optimization of a Composite Canard Control Surface of an Advanced Fighter Aircraft under Static Loading

2015 ◽  
Vol 2 (1) ◽  
Author(s):  
Sachin Shrivastava ◽  
P.M. Mohite
Keyword(s):  
Static Loading ◽  
Fiber Composite ◽  
Design Procedure ◽  
Optimization Procedure ◽  
High Strength ◽  
Control Surface ◽  
Carbon Fiber Composite ◽  
Ferrous Alloys ◽  
Fighter Aircraft ◽  
Elitist Strategy

AbstractThe minimization of weight and maximization of payload is an ever challenging design procedure for air vehicles. The present study has been carried out with an objective to redesign control surface of an advanced all-metallic fighter aircraft. In this study, the structure made up of high strength aluminum, titanium and ferrous alloys has been attempted to replace by carbon fiber composite (CFC) skin, ribs and stiffeners. This study presents an approach towards development of a methodology for optimization of first-ply failure index (FI) in unidirectional fibrous laminates using Genetic-Algorithms (GA) under quasi-static loading. The GAs, by the application of its operators like reproduction, cross-over, mutation and elitist strategy, optimize the ply-orientations in laminates so as to have minimum FI of Tsai-Wu first-ply failure criterion. The GA optimization procedure has been implemented in MATLAB and interfaced with commercial software ABAQUS using python scripting. FI calculations have been carried out in ABAQUS with user material subroutine (UMAT). The GA's application gave reasonably well-optimized ply-orientations combination at a faster convergence rate. However, the final optimized sequence of ply-orientations is obtained by tweaking the sequences given by GA's based on industrial practices and experience, whenever needed. The present study of conversion of an all metallic structure to partial CFC structure has led to 12% of weight reduction. Therefore, the approach proposed here motivates designer to use CFC with a confidence.

Size and Shape Optimization of Compliant Mechanisms: An Efficiency Formulation

1998 ◽  
Author(s):  
Joel A. Hetrick ◽  
Sridhar Kota
Keyword(s):  
Shape Optimization ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Optimization Procedure ◽  
Stress Constraints ◽  
Mechanical Efficiency ◽  
Optimization Techniques ◽  
Mechanical Transmission ◽  
Dimensional Synthesis ◽  
Size And Shape

Abstract Compliant mechanisms are jointless mechanical devices that take advantage of elastic deformation to achieve a force or motion transformation. A milestone toward systematic design of compliant mechanisms has been the development of topology optimization techniques. The next logical step is to incorporate size and shape optimization to identify the exact dimensional form of the mechanism. A new objective formulation based on maximizing the mechanical efficiency of a compliant mechanism is developed in order to perform the size and shape optimization. An advantage of this formulation is that precise control over the mechanism’s mechanical or geometric advantage can be enforced during optimization. Finite element beam models are used to perform dimensional synthesis of planar compliant mechanisms. This technique allows stress constraints to limit the maximum stress in the mechanism which improves the mechanism’s durability and flexibility. Resulting optimized mechanisms exhibit efficient mechanical transmission and meet kinematic and stress requirements. Several examples are given to demonstrate the effectiveness of the optimization procedure.

Prestressed Carbon Fiber Composite Overwrapped Gun Tube

2008 ◽  
Author(s):  
Andrew Littlefield ◽  
Edward Hyland ◽  
Jack Keating
Keyword(s):  
Carbon Fiber ◽  
Fiber Composite ◽  
Carbon Fiber Composite
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