scholarly journals A Statically Balanced Shape Shifting Surface

2012 ◽  
Author(s):  
Joseph E. Pishnery ◽  
Craig P. Lusk
Keyword(s):  
Compliant Mechanism ◽  
Tiling Array ◽  
Variable Stiffness ◽  
Parent Material ◽  
Thin Plates ◽  
Physical Barrier ◽  
Zero Force ◽  
Polygonal Cell ◽  
Wide Range ◽  
Macro Scale

This paper presents a concept for producing a Statically Balanced Shape-Shifting Surface (SB-SSS). In this context, an SB-SSS is a surface that can require near-zero magnitude force changes to accomplish a change in shape while retaining effectiveness as a physical barrier. This paper focuses on how to statically balance a specifically-designed compliant mechanism and how to incorporate this mechanism into a polygonal cell. The mechanism consists of a compliant Peaucellier-Lipkin linkage layered with a pre-stressed link as the balancer. Prior art is presented that can show how a polygonal cell can be incorporated into a surface via a tiling array. Specifically shaped overlapping thin plates are used to retain the physical barrier requirement. The demonstration of a virtually zero-force Shape-Shifting Surface (SSS) suggests that SSS’s can be designed with a wide range of force-displacement properties, i.e. ranging from that of a square of the parent material to the zero-force mechanism presented here. Applications for an SB-SSS may be macro-scale or micro-scale and may include sensors, biomedical applications, defense applications, and variable stiffness materials.

Design of a Compliant Mechanism to Generate an Arbitrary Nonlinear Force-Deflection Profile

2018 ◽  
Author(s):  
Kyle Buschkoetter ◽  
Ashok Midha
Keyword(s):  
Resistance Exercise ◽  
Case Studies ◽  
Compliant Mechanism ◽  
Synthesis Method ◽  
Variable Stiffness ◽  
Variable Resistance ◽  
Wide Range ◽  
Nonlinear Force ◽  
Exercise Equipment ◽  
Variable Stiffness Actuators

This paper presents a compliant mechanism that can generate a wide range of force-deflection profiles. This partially compliant mechanism is comprised of a wedge cam with a compliant follower. The designer specifies the material and geometric properties of the compliant segment, as well as a desired force-deflection profile. A cam surface is then synthesized that helps generate this profile. The synthesis method is validated experimentally with the help of two case studies. Some possible areas of application include robotics, variable stiffness actuators, electrical connectors, design for automotive crashworthiness, and variable resistance exercise equipment.

The Future of Plasma-Based Surface Engineering Techniques in Tribology (Keynote)

2005 ◽  
Author(s):  
Allan Matthews ◽  
Adrian Leyland
Keyword(s):  
Surface Engineering ◽  
Performance Enhancement ◽  
Bulk Material ◽  
Cost Savings ◽  
Cost Effective ◽  
Ceramic Coatings ◽  
Performance Improvements ◽  
Treatment Techniques ◽  
Wide Range ◽  
Macro Scale

Over the past twenty years or so, there have been major steps forward both in the understanding of tribological mechanisms and in the development of new coating and treatment techniques to better “engineer” surfaces to achieve reductions in wear and friction. Particularly in the coatings tribology field, improved techniques and theories which enable us to study and understand the mechanisms occurring at the “nano”, “micro” and “macro” scale have allowed considerable progress to be made in (for example) understanding contact mechanisms and the influence of “third bodies” [1–5]. Over the same period, we have seen the emergence of the discipline which we now call “Surface Engineering”, by which, ideally, a bulk material (the ‘substrate’) and a coating are combined in a way that provides a cost-effective performance enhancement of which neither would be capable without the presence of the other. It is probably fair to say that the emergence and recognition of Surface Engineering as a field in its own right has been driven largely by the availability of “plasma”-based coating and treatment processes, which can provide surface properties which were previously unachievable. In particular, plasma-assisted (PA) physical vapour deposition (PVD) techniques, allowing wear-resistant ceramic thin films such as titanium nitride (TiN) to be deposited on a wide range of industrial tooling, gave a step-change in industrial productivity and manufactured product quality, and caught the attention of engineers due to the remarkable cost savings and performance improvements obtained. Subsequently, so-called 2nd- and 3rd-generation ceramic coatings (with multilayered or nanocomposite structures) have recently been developed [6–9], to further extend tool performance — the objective typically being to increase coating hardness further, or extend hardness capabilities to higher temperatures.

A Geometric Parametric Analysis of a Magnetorheological Engine Mount

2010 ◽  
Author(s):  
Walter Anderson ◽  
Constantine Ciocanel ◽  
Mohammad Elahinia
Keyword(s):  
High Frequency ◽  
New Technology ◽  
Low Frequency ◽  
Variable Stiffness ◽  
Small Displacement ◽  
Element Analysis ◽  
Mr Fluid ◽  
Wide Range ◽  
Engine Mount ◽  
Vehicle Technology

Engine vibration has caused a great deal of research for isolation to be performed. Traditionally, isolation was achieved through the use of pure elastomeric (rubber) mounts. However, with advances in vehicle technology, these types of mounts have become inadequate. The inadequacy stems from the vibration profile associated with the engine, i.e. high displacement at low frequency and small displacement at high frequency. Ideal isolation would be achieved through a stiff mount for low frequency and a soft mount for high frequency. This is contradictory to the performance of the elastomeric mounts. Hydraulic mounts were then developed to address this problem. A hydraulic mount has variable stiffness and damping due to the use of a decoupler and an inertia track. However, further advances in vehicle technology have rendered these mounts inadequate as well. Examples of these advances are hybridization (electric and hydraulic) and cylinder on demand (VCM, MDS & ACC). With these technologies, the vibration excitation has a significantly different profile, occurs over a wide range of frequencies, and calls for a new technology that can address this need. Magnetorheological (MR) fluid is a smart material that is able to change viscosity in the presence of a magnetic field. With the use of MR fluid, variable damping and stiffness can be achieved. An MR mount has been developed and tested. The performance of the mount depends on the geometry of the rubber part as well as the behavior of the MR fluid. The rubber top of the mount is the topic of this study due to its major impact on the isolation characteristics of the MR mount. To develop a design methodology to address the isolation needs of different hybrid vehicles, a geometric parametric finite element analysis has been completed and presented in this paper.

A Compliant Transmission Mechanism With Intermittent Contacts for Cycle-Doubling

2006 ◽  
Vol 129 (1) ◽  
pp. 114-121 ◽  
Author(s):  
Nilesh D. Mankame ◽  
G. K. Ananthasuresh
Keyword(s):  
Finite Element ◽  
Conceptual Design ◽  
Finite Element Simulations ◽  
Nonlinear Finite Element ◽  
Transmission Mechanism ◽  
Input Frequency ◽  
Length Scales ◽  
Wide Range ◽  
Macro Scale ◽  
Functional Prototype

A novel compliant transmission mechanism that doubles the frequency of a cyclic input is presented in this paper. The compliant cycle-doubler is a contact-aided compliant mechanism that uses intermittent contact between itself and a rigid surface. The conceptual design for the cycle-doubler was obtained using topology optimization in our earlier work. In this paper, a detailed design procedure is presented for developing the topology solution into a functional prototype. The conceptual design obtained from the topology solution did not account for the effects of large displacements, friction, and manufacturing-induced features such as fillet radii. Detailed nonlinear finite element analyses and experimental results from quasi-static tests on a macro-scale prototype are used in this paper to understand the influence of the above factors and to guide the design of the functional prototype. Although the conceptual design is based on the assumption of quasi-static operation, the modified design is shown to work well in a dynamic setting for low operating frequencies via finite element simulations. The cycle-doubler design is a monolithic elastic body that can be manufactured from a variety of materials and over a range of length scales. This makes the design scalable and thus adaptable to a wide range of operating frequencies. Explicit dynamic nonlinear finite element simulations are used to verify the functionality of the design at two different length scales: macro (device footprint of a square of 170mm side) at an input frequency of 7.8Hz; and meso (device footprint of a square of 3.78mm side) at an input frequency of 1kHz.

scholarly journals Parametric structural modelling of fish bone active camber morphing aerofoils

2018 ◽  
Vol 29 (9) ◽  
pp. 2008-2026 ◽  
Author(s):  
Andres E Rivero ◽  
Paul M Weaver ◽  
Jonathan E Cooper ◽  
Benjamin KS Woods
Keyword(s):  
Analytical Model ◽  
Composite Laminates ◽  
Plate Theory ◽  
Ritz Method ◽  
Linear Equations ◽  
Variable Stiffness ◽  
Automated Analysis ◽  
Fish Bone ◽  
Two Dimensional ◽  
Wide Range

Camber morphing aerofoils have the potential to significantly improve the efficiency of fixed and rotary wing aircraft by providing significant lift control authority to a wing, at a lower drag penalty than traditional plain flaps. A rapid, mesh-independent and two-dimensional analytical model of the fish bone active camber concept is presented. Existing structural models of this concept are one-dimensional and isotropic and therefore unable to capture either material anisotropy or spanwise variations in loading/deformation. The proposed model addresses these shortcomings by being able to analyse composite laminates and solve for static two-dimensional displacement fields. Kirchhoff–Love plate theory, along with the Rayleigh–Ritz method, are used to capture the complex and variable stiffness nature of the fish bone active camber concept in a single system of linear equations. Results show errors between 0.5% and 8% for static deflections under representative uniform pressure loadings and applied actuation moments (except when transverse shear exists), compared to finite element method. The robustness, mesh-independence and analytical nature of this model, combined with a modular, parameter-driven geometry definition, facilitate a fast and automated analysis of a wide range of fish bone active camber concept configurations. This analytical model is therefore a powerful tool for use in trade studies, fluid–structure interaction and design optimisation.

A numerical investigation of fluid flows induced by the oscillations of thin plates and evaluation of the associated hydrodynamic forces

2019 ◽  
Vol 874 ◽  
pp. 1057-1095 ◽  
Author(s):  
Artem N. Nuriev ◽  
Airat M. Kamalutdinov ◽  
Andrey G. Egorov
Keyword(s):  
Stokes Equations ◽  
Experimental Studies ◽  
Flow Regimes ◽  
Hydrodynamic Forces ◽  
Thin Plates ◽  
Oscillatory Process ◽  
Dimensionless Frequency ◽  
Two Dimensional ◽  
Wide Range ◽  
Hydrodynamic Influence

The paper is devoted to the problem of harmonic oscillations of thin plates in a viscous incompressible fluid. The two-dimensional flows caused by the plate oscillations and their hydrodynamic influence on the plates are studied. The fluid motion is described by the non-stationary Navier–Stokes equations, which are solved numerically on the basis of the finite volume method. The simulation is carried out for plates with different thicknesses and shapes of edges in a wide range of control parameters of the oscillatory process: dimensionless frequency and amplitude of oscillations. For the first time in the framework of one model all two-dimensional flow regimes, which were found earlier in experimental studies, are described. Two new flow regimes emerging along the stability boundaries of symmetric flow regimes are localized. The map of flow regimes in the frequency–amplitude plane is constructed. The analysis of the hydrodynamic influence of flows on the plates allow us to establish new effects associated with the influence of the shape of the plates on the drag and inertia forces. Due to these effects, the values of hydrodynamic forces can differ by 90 % at the same parameters of the oscillation. The lower and upper estimates of hydrodynamic forces obtained in the work have a good agreement with the experimental data presented in the literature.

Environmental Variables Influencing Chironomid Assemblages (Diptera: Chironomidae) in Lowland Rivers of Central Poland

2019 ◽  
Vol 48 (4) ◽  
pp. 988-997 ◽  
Author(s):  
Joanna Leszczyńska ◽  
Maria Grzybkowska ◽  
Łukasz Głowacki ◽  
Małgorzata Dukowska
Keyword(s):  
Organic Matter ◽  
Species Richness ◽  
Dissolved Oxygen ◽  
Theoretic Approach ◽  
Lowland Rivers ◽  
Bottom Substrate ◽  
Central Poland ◽  
Wide Range ◽  
Macro Scale ◽  
Chironomid Assemblages

Abstract Chironomids (Diptera: Chironomidae) are a family of dipterans with a global distribution. Owing to their great functional diversity and ability to adapt to a wide range of environmental conditions, they often dominate in freshwater macroinvertebrate communities, playing a key role in the cycling of organic matter and the flow of energy in aquatic ecosystems. Our aim was to analyze the structure of chironomid assemblages and identify the environmental factors, including current velocity, river width, water depth, water temperature, dissolved oxygen, percentage of substrate covered by vascular plants, inorganic bottom substrate, and quantity of benthic (BPOM) and transported (TPOM) particulate organic matter, that underpin variation in species richness across a set of lowland rivers in central Poland, differing by stream order and abiotic parameters. Using an Information Theoretic Approach, we formulated a set of alternative models based on previously published work, with models fitted in a Bayesian framework using Integrated Nested Laplace Approximation. The species richness of chironomids increased with river order, achieving a maximum in third and fourth order rivers, but decreased at higher orders. The best-fitting models included a positive effect of inorganic substrate index and dissolved oxygen on chironomid species richness. The quality structure of chironomid assemblages reflected the assumptions of the River Continuum Concept showing that species richness was under the influence of factors operating at both a micro- (inorganic bottom substrate) and macro-scale (dissolved oxygen).

scholarly journals Digital laser micro- and nanoprinting

Nanophotonics ◽  
2018 ◽  
Vol 8 (1) ◽  
pp. 27-44 ◽  
Author(s):  
Qingfeng Li ◽  
David Grojo ◽  
Anne-Patricia Alloncle ◽  
Boris Chichkov ◽  
Philippe Delaporte
Keyword(s):  
Three Dimensional ◽  
Digital Fabrication ◽  
Two Dimensions ◽  
Minimum Size ◽  
Direct Writing ◽  
3D Objects ◽  
Wide Range ◽  
Macro Scale ◽  
Forward Transfer ◽  
Pros And Cons

AbstractLaser direct writing is a well-established ablation technology for high-resolution patterning of surfaces, and since the development of additive manufacturing, laser processes have also appeared very attractive for the digital fabrication of three-dimensional (3D) objects at the macro-scale, from few millimeters to meters. On the other hand, laser-induced forward transfer (LIFT) has demonstrated its ability to print a wide range of materials and to build functional micro-devices. For many years, the minimum size of laser-printed pixels was few tens of micrometers and is usually organized in two dimensions. Recently, new approaches have been investigated, and the potential of LIFT technology for printing 2D and 3D sub-micrometer structures has become real. After a brief description of the LIFT process, this review presents the pros and cons of the different digital laser printing technologies in the aim of the additive nanomanufacturing application. The transfer of micro- and nano-dots in the liquid phase from a solid donor film appears to be the most promising approach to reach the goal of 3D nanofabrication, and the latest achievements obtained with this method are presented and discussed.

scholarly journals Are there viable chemical and non-chemical alternatives to the use of conventional insecticides for the protection of young trees from damage by the large pine weevil Hylobius abietis L. in UK forestry?

2020 ◽  
Vol 93 (5) ◽  
pp. 694-712
Author(s):  
Ian H Willoughby ◽  
Roger Moore ◽  
Andrew J Moffat ◽  
Jack Forster ◽  
Imam Sayyed ◽  
...  
Keyword(s):  
Natural Product ◽  
Control Agent ◽  
Picea Sitchensis ◽  
Hylobius Abietis ◽  
Physical Barrier ◽  
Aquatic Life ◽  
Pyrethroid Insecticides ◽  
Pine Weevil ◽  
Wide Range ◽  
The Uk

Abstract In UK forestry, the synthetic pyrethroid insecticides alpha-cypermethrin and cypermethrin have been used for many years to provide protection for young trees planted on restock sites from damage by the large pine weevil, Hylobius abietis L. However, concerns over the toxicity of these insecticides to aquatic life if misused have led to a search for alternative forms of protection. This paper describes a detailed programme of efficacy experiments undertaken between 2009 and 2015 to find replacements for these products. Over 50 combinations of chemical and non-chemical approaches were tested on 16 different sites. Of the alternative synthetic insecticides tested, applications of 0.037 g a.i. stem−1 acetamiprid provided high levels of protection from Hylobius browsing damage on young Sitka spruce (Picea sitchensis (Bong.) Carrière) trees, without causing any phytotoxic symptoms, and gave comparable levels of protection to those achievable using alpha-cypermethrin or cypermethrin. Acetamiprid is less toxic to aquatic life than alpha-cypermethrin or cypermethrin and has not been linked to bee decline. Applications of 0.0129 g a.i. stem−1 chlorantraniliprole also showed promise, and this relatively low toxicity non-neonicotinoid insecticide merits further study. Although imidacloprid and thiacloprid also provided good levels of protection, their use in forests is not now permitted due to concerns over their potential impacts on bees and drinking water, respectively. Whilst the natural product insecticide spinosad, and the entomopathogenic fungal control agent Metarhizium anisopliae (Metschn.) Sorokin, gave only limited protection in our work, they may have some future potential if methods of deployment can be improved. Other chemical and non-chemical approaches tested, but found to be largely ineffective in UK conditions, included the natural product insecticides azadirachtin, maltodextrin and pyrethrins, the synthetic insecticides lambda-cyhalothrin and spirotetramat and a wide range of repellents, flexible stem coatings and physical barrier products. However, we conclude that physical barrier sleeves such as MultiPro® and BioSleeve® may have a limited role as a partial substitute for the use of insecticides in the UK in some circumstances, but only if on-site populations of Hylobius are predicted to be low.

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