scholarly journals Multistable Morphing Mechanisms of Nonlinear Springs

2019 ◽  
Vol 11 (5) ◽  
Author(s):  
Chrysoula Aza ◽  
Alberto Pirrera ◽  
Mark Schenk
Keyword(s):  
Design Space ◽  
Large Deformations ◽  
Compliant Mechanisms ◽  
Helical Structures ◽  
Nonlinear Springs ◽  
Structural Assembly ◽  
Stiffness Characteristics ◽  
Nonlinear Components ◽  
Type Of Behavior ◽  
Initial Geometry

Compliant mechanisms find use in numerous applications in both microscale and macroscale devices. Most of the current compliant mechanisms base their behavior on beam flexures. Their range of motion is thus limited by the stresses developed upon deflection. Conversely, the proposed mechanism relies on elastically nonlinear components to achieve large deformations. These nonlinear elements are composite morphing double-helical structures that are able to extend and coil like springs, yet, with nonlinear stiffness characteristics. A mechanism consisting of such structures, assembled in a simple truss configuration, is explored. A variety of behaviors is unveiled that could be exploited to expand the design space of current compliant mechanisms. The type of behavior is found to depend on the initial geometry of the structural assembly, the lay-up, and other characteristics specific of the composite components.

Spatial Kinematic Analysis of Threaded Fastener Assembly

2005 ◽  
Vol 128 (1) ◽  
pp. 116-127 ◽  
Author(s):  
Stephen Wiedmann ◽  
Bob Sturges
Keyword(s):  
Design Space ◽  
Compliant Mechanisms ◽  
Contact Point ◽  
Three Dimensional ◽  
Vertical Movement ◽  
Initial Contact ◽  
Geometric Problem ◽  
Intelligent Sensor ◽  
Contact State ◽  
Contact Points

Compliant mechanisms for rigid part mating exist for prismatic geometries. A few instances are known of mechanisms to assemble screw threads. A comprehensive solution to this essentially geometric problem comprises at least three parts: parametric equations for nut and bolt contact in the critical starting phase of assembly, the possible space of motions between these parts during this phase, and the design space of compliant devices which accomplish the desired motions in the presence of friction and positional uncertainty. This work concentrates on the second part in which the threaded pair is modeled numerically, and contact tests are automated through software. Tessellated solid models were used during three-dimensional collision analysis to enumerate the approximate location of the initial contact point. The advent of a second contact point presented a more constrained contact state. Thus, the bolt is rotated about a vector defined by the initial two contact points until a third contact location was found. By analyzing the depth of intersection of the bolt into the nut as well as the vertical movement of the origin of the bolt reference frame, we determined that there are three types of contacts states present: unstable two-point, quasi-stable two-point, stable three point. The space of possible motions is bounded by these end conditions which will differ in detail depending upon the starting orientations. We investigated all potential orientations which obtain from a discretization of the roll, pitch, and yaw uncertainties, each of which has its own set of contact points. From this exhaustive examination, a full contact state history was determined, which lays the foundation for the design space of either compliant mechanisms or intelligent sensor-rich controls.

scholarly journals Bistable composite helices with thermal effects

2019 ◽  
Vol 475 (2229) ◽  
pp. 20190295 ◽  
Author(s):  
Seán Carey ◽  
Robert Telford ◽  
Vincenzo Oliveri ◽  
Ciaran McHale ◽  
Paul Weaver
Keyword(s):  
Thermal Effects ◽  
Design Space ◽  
Analytical Description ◽  
Analytical Models ◽  
Fatigue Properties ◽  
Finite Element Models ◽  
Helical Structures ◽  
Industrial Sectors ◽  
Strength And Stiffness ◽  
Increased Strength

Morphing technologies use large, seamless changes in the shape of a structure to enable multi-functionality and reconfigurability. Several industrial sectors could benefit from morphing structures, including medical, energy and aerospace which require lightweight, simple and reliable solutions. Composite materials are key to lightweight morphing technologies due to their increased strength- and stiffness-to-mass ratios, stiffness tailorability and excellent fatigue properties, all of which reduce the mass and complexity of these types of structures. By accounting for thermal effects in their analytical description, we enhance the viability of multi-stable composite helical structures. This consideration improves predictions of existing analytical models in comparison with experiments, while also vastly expanding the design space to include antisymmetric and non-symmetric flange lay-up sequences. The developed analytical model is presented and verified using both finite-element models and experiments. By including thermal effects, we show that beneficial new morphing behaviours can be obtained.

An Improved Method for Designing Flexure-Based Nonlinear Springs

2012 ◽  
Author(s):  
Qiaoling Meng ◽  
Giovanni Berselli ◽  
Rocco Vertechy ◽  
Vincenzo Parenti Castelli
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Compliant Mechanisms ◽  
Empirical Equations ◽  
Element Analysis ◽  
Closed Form Solutions ◽  
Nonlinear Springs ◽  
Aspect Ratios ◽  
Analytical Relations ◽  
Flexural Hinges

Monolithic Flexure-based Compliant Mechanisms (MFCM) can functionally act as nonlinear springs by providing a desired load-displacement profile at one point on their structure. Once the MFCM topology is chosen, these particular springs can be conveniently synthesized by resorting to the well-known Pseudo-Rigid-Body approximation, whose accuracy strongly depends on the modeling precision of the flexures’ principal compliance. For various types of flexures, closed-form solutions have been proposed which express the compliance factors as functions of the flexure dimensions. Nonetheless, the reliability of these analytical relations is limited to slender, beam-like, hinges undergoing small deflections. In order to overcome such limitations, this paper provides empirical equations, derived from finite element analysis, that can be used for the optimal design of circular, elliptical, and corner-filleted flexural hinges with general aspect ratios on the basis of both principal compliance and maximum bearable stress. As a case study, a nonlinear spring conceived as a four-bar linkage MFCM is synthesized and simulated by means of finite element analysis. Numerical results confirm that the aforementioned empirical equations outperform their analytical counterparts when modeling thick cross-section hinges undergoing large deflections.

Design of Crashworthy Structures With Controlled Energy Absorption in the Hybrid Cellular Automaton Framework

2013 ◽  
Vol 135 (9) ◽  
Author(s):  
Punit Bandi ◽  
James P. Schmiedeler ◽  
Andrés Tovar
Keyword(s):  
Energy Absorption ◽  
Design Space ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Mechanism Synthesis ◽  
Load Paths ◽  
Fully Stressed Design ◽  
Novel Method ◽  
The Given ◽  
Synthesis Approach

This work presents a novel method for designing crashworthy structures with controlled energy absorption based on the use of compliant mechanisms. This method helps in introducing flexibility at desired locations within the structure, which in turn reduces the peak force at the expense of a reasonable increase in intrusion. For this purpose, the given design domain is divided into two subdomains: flexible (FSD) and stiff (SSD) subdomains. The design in the flexible subdomain is governed by the compliant mechanism synthesis approach for which output ports are defined at the interface between the two subdomains. These output ports aid in defining potential load paths and help the user make better use of a given design space. The design in the stiff subdomain is governed by the principle of a fully stressed design for which material is distributed to achieve uniform energy distribution within the design space. Together, FSD and SSD provide for a combination of flexibility and stiffness in the structure, which is desirable for most crash applications.

Evaluating Compliant Hinge Geometries for Origami-Inspired Mechanisms

2015 ◽  
Vol 7 (1) ◽  
Author(s):  
Isaac L. Delimont ◽  
Spencer P. Magleby ◽  
Larry L. Howell
Keyword(s):  
Closed Form ◽  
Design Space ◽  
Compliant Mechanisms ◽  
Large Deflections ◽  
Center Of Rotation ◽  
Closed Form Solutions ◽  
Potential Development ◽  
Design Guide

Origami-inspired design is an emerging field capable of producing compact and efficient designs. Compliant hinges are proposed as a way to replicate the folding motion of paper when using nonpaper materials. Compliant hinges function as surrogate folds and can be defined as localized reduction of stiffness. The purpose of this paper is to organize and evaluate selected surrogate folds for use in compliant mechanisms. These surrogate folds are characterized based on the desired motion as well as motions typically considered parasitic. Additionally, the surrogate folds' ability to rotate through large deflections and their stability of center of rotation are evaluated. Existing surrogate folds are reviewed and closed-form solutions presented. A diagram intended as a straightforward design guide is presented. Areas for potential development in the surrogate fold design space are noted.

scholarly journals From arteries to boreholes: transient response of a poroelastic cylinder to fluid injection

2018 ◽  
Vol 474 (2216) ◽  
pp. 20180284 ◽  
Author(s):  
L. C. Auton ◽  
C. W. MacMinn
Keyword(s):  
Transient Response ◽  
Large Deformations ◽  
Fluid Pressure ◽  
Soft Materials ◽  
Fluid Injection ◽  
Solid Skeleton ◽  
Fluid Flux ◽  
Vascular Walls ◽  
Initial Geometry

The radially outward flow of fluid through a porous medium occurs in many practical problems, from transport across vascular walls to the pressurization of boreholes in the subsurface. When the driving pressure is non-negligible relative to the stiffness of the solid structure, the poromechanical coupling between the fluid and the solid can control both the steady state and the transient mechanics of the system. Very large pressures or very soft materials lead to large deformations of the solid skeleton, which introduce kinematic and constitutive nonlinearity that can have a non-trivial impact on these mechanics. Here, we study the transient response of a poroelastic cylinder to sudden fluid injection. We consider the impacts of kinematic and constitutive nonlinearity, both separately and in combination, and we highlight the central role of driving method in the evolution of the response. We show that the various facets of nonlinearity may either accelerate or decelerate the transient response relative to linear poroelasticity, depending on the boundary conditions and the initial geometry, and that an imposed fluid pressure leads to a much faster response than an imposed fluid flux.

Preliminary Concepts for Deployable Wings on Small UAVs Using Compliance

Aerospace ◽  
2005 ◽  
Author(s):  
Steven D. Landon ◽  
Spencer P. Magleby ◽  
Larry L. Howell
Keyword(s):  
Law Enforcement ◽  
Design Space ◽  
Compliant Mechanisms ◽  
Development Project ◽  
Aerial Surveillance ◽  
New Concepts ◽  
Product Development Project ◽  
Wing Structures ◽  
Single User ◽  
Selection Of

Advances in technology for Unmanned Air Vehicles (UAVs) have given rise to increasingly smaller UAVs and a growing need for adaptable UAV wing structures. Deployable, or collapsible, wings offer space savings and broaden the number of possible applications for UAVs. Aerial surveillance applications, such as military reconnaissance, law enforcement, forestry, map making, pipeline surveillance, and border patrol typically demand a UAV that can be carried and deployed by a single user in an isolated field. This paper provides a framework of deployable wing concepts using compliant mechanisms. Compliant mechanisms offer reduced part count, decreased need for lubrication, efficient manufacturability, and space savings compared to traditional joint systems. The design space for compliant deployable wings is explored, concepts are categorized into classes based on motion type, and opportunities are identified for creating new concepts. A method is presented for selecting and evaluating concepts for specific applications. A product development project illustrates selection of a deployable wing design for a particular application, and the paper concludes with suggestions for further work.

scholarly journals Load–Displacement Characterization in Three Degrees-of-Freedom for General Lamina Emergent Torsion Arrays

2020 ◽  
Vol 142 (9) ◽  
Author(s):  
Nathan A. Pehrson ◽  
Pietro Bilancia ◽  
Spencer Magleby ◽  
Larry Howell
Keyword(s):  
Degrees Of Freedom ◽  
Design Space ◽  
Element Analysis ◽  
Array Design ◽  
Elastic Load ◽  
In Series ◽  
Load Displacement ◽  
Stiffness Characteristics ◽  
Tunable Stiffness ◽  
Three Degrees Of Freedom

Abstract Lamina emergent torsion (LET) joints for use in origami-based applications enables folding of panels. Placing LET joints in series and parallel (formulating LET arrays) opens the design space to provide for tunable stiffness characteristics in other directions while maintaining the ability to fold. Analytical equations characterizing the elastic load–displacement for general serial–parallel formulations of LET arrays for three degrees-of-freedom are presented: rotation about the desired axis, in-plane rotation, and extension/compression. These equations enable the design of LET arrays for a variety of applications, including origami-based mechanisms. These general equations are verified using finite element analysis, and to show variability of the LET array design space, several verification plots over a range of parameters are provided.

scholarly journals Optimization of a ducted fan propulsion system for a single engine aircraft

2021 ◽  
Author(s):  
Adam Jasudavisius
Keyword(s):  
Line Search ◽  
Design Space ◽  
Propulsion System ◽  
Optimization Approach ◽  
Control Points ◽  
Ducted Fan ◽  
Optimization Methodology ◽  
High Degree ◽  
Cruise Flight ◽  
Initial Geometry

The objective of this study was to perform a 3D aerodynamic shape optimization on a ducted fan propulsion system configured for cruise flight on an aircraft. The initial shapes of the duct and hub were determined using a basic grid searching optimization approach. An efficient optimization algorithm was created that utilized the BFGS searching technique with a QuasiNewton line search to refine the initial geometry. The ducted fan was chosen to be controlled by 13 control points connected using a combination of splines, ellipses and conics. The optimum design resulted in a 33.54% and 36.45% reduction in drag for the duct and hub respectively. The propeller thrust was also increased by 141.49%. The optimization methodology used throughout this study proved to be an efficient technique in finding the optimal design to within a high degree of resolution based on the entire design space considered.

Large Deformation Analysis and Experiments With Double Parallelogram Compliant Mechanisms

2018 ◽  
Author(s):  
Abhijit A. Tanksale ◽  
Prasanna S. Gandhi
Keyword(s):  
Large Deformation ◽  
High Precision ◽  
Large Deformations ◽  
Compliant Mechanisms ◽  
Compliant Mechanism ◽  
Vertical Plane ◽  
Coupled Analysis ◽  
Deformation Analysis ◽  
Flexible Beams ◽  
Straight Line

Compliant mechanisms are highly preferred in applications demanding motion with high precision. These mechanisms provide friction-less, backlash-free precise motion obtained through deformation of flexible members. The double parallelogram compliant mechanism (DPCM) is one the most important compliant mechanisms to obtain highly precise straight-line motion. DPCM when operated in horizontal plane yield high precision straight-line motion (even with large deformations) useful in several engineering applications. However, constraints such as space, dead loads, etc. may demand DPCMs to be used in the vertical plane. For DPCMs operating in a vertical plane, the axial load due to gravity causes tension and compression in flexible beams which get coupled to bending under large deformations. This ultimately affects the parasitic error of straight-line motion. This paper presents a coupled analysis, along with experimental validation, of DPCM operating in vertical plane considering gravity effects with large deformation.

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