Modelling the Axis Drift of Short Wire Flexures and Increasing Their Support Stiffness Using Polymers

2021 ◽  
Author(s):  
Boris Daan ◽  
Jelle Rommers ◽  
Just L. Herder
Keyword(s):  
Finite Element ◽  
Rigid Body ◽  
Finite Element Methods ◽  
Complex Geometries ◽  
Lower Error ◽  
Material Stiffness ◽  
Physical Tests ◽  
Novel Method ◽  
High Support ◽  
Modelling Approach

Abstract For steel flexures, complex geometries are required to reach high support stiffness and limit axis drift over large ranges of motion. These complex flexures are expensive and difficult to manufacture. This paper presents a method of designing short, polymer wire flexures with high support stiffness and modelling their axis drift using a novel method, the arc method. The arc method is validated against finite element methods (FEM) and physical tests, showing at least a factor 10 lower error than existing pseudo-rigid-body models (PRBM) at 70° deflection, while maintaining a simple modelling approach. The use of polymers increases support stiffness of wire flexures by a factor 7800 with respect to steel at 70° deflection, even though the material stiffness is substantially lower. This is due to the large allowed strain of polymers increasing the possible diameter by a factor 110.

A Novel Method for the Implementation of Contact Including Energy Dissipation in Finite Element Methods

2014 ◽  
Author(s):  
J. J. Grudzinski ◽  
M. Gosz
Keyword(s):  
Finite Element ◽  
Energy Dissipation ◽  
Finite Element Methods ◽  
Contact Friction ◽  
Element Formulation ◽  
Drag Forces ◽  
Contact Constraint ◽  
Fluid Drag ◽  
Novel Method ◽  
Contact Impact

A new method for implementing contact/impact in an implicit finite element formulation has recently been developed. The method uses the idea of buoyancy and fluid drag forces to enforce the contact constraint as well as provide a method of dissipating energy due to the contact. Additionally, the method provides a simplified means for accounting for contact friction. The method has potential usefulness in a certain class of problems such as contact with bodies having soft and viscous foundations as well as problems with sliding. In this work, we introduce the method and illustrate it with an example that shows the benefits and utility of the method.

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.

Equilibrium Profile of Modern Belted Radial Ply Tires: Its Determination and Performance Benefits

2013 ◽  
Vol 41 (2) ◽  
pp. 127-151
Author(s):  
Rudolf F. Bauer
Keyword(s):  
Finite Element ◽  
Aspect Ratio ◽  
Finite Element Methods ◽  
Mathematical Analysis ◽  
Internal Stresses ◽  
Stress Concentrations ◽  
Equilibrium Profiles ◽  
Equilibrium Profile ◽  
And Performance ◽  
Beneficial Property

ABSTRACT The benefits of a tire's equilibrium profile have been suggested by several authors in the published literature, and mathematical procedures were developed that represented well the behavior of bias ply tires. However, for modern belted radial ply tires, and particularly those with a lower aspect ratio, the tire constructions are much more complicated and pose new problems for a mathematical analysis. Solutions to these problems are presented in this paper, and for a modern radial touring tire the equilibrium profile was calculated together with the mold profile to produce such tires. Some construction modifications were then applied to these tires to render their profiles “nonequilibrium.” Finite element methods were used to analyze for stress concentrations and deformations within all tires that did or did not conform to equilibrium profiles. Finally, tires were built and tested to verify the predictions of these analyses. From the analysis of internal stresses and deformations on inflation and loading and from the actual tire tests, the superior durability of tires with an equilibrium profile was established, and hence it is concluded that an equilibrium profile is a beneficial property of modern belted radial ply tires.

Finite element methods for internal flow calculations

1983 ◽  
Author(s):  
W. HABASHI ◽  
M. HAFEZ ◽  
P. KOTIUGA
Keyword(s):  
Finite Element ◽  
Finite Element Methods ◽  
Internal Flow
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