Parameter Study of a Multi-Field Actuated, Multilayered, Segmented Flexible Composite Beam

2018 ◽  
Author(s):  
Anil Erol ◽  
Paris von Lockette ◽  
Mary Frecker
Keyword(s):  
Magnetic Material ◽  
Electric Fields ◽  
Parameter Study ◽  
Flexible Beam ◽  
Large Displacements ◽  
Objective Functions ◽  
Active Materials ◽  
Input Variables ◽  
Characteristic Features ◽  
Single Field

Multi-layered, self-actuated devices have been the focus of recent studies due to their ability to exhibit large displacements and achieve complex shapes. Such devices have been constructed using active materials responsive to varying stimuli including electro-active and magneto-active materials to perform useful functions or satisfy objective functions related to target shapes. In this work, the authors seek to study the utility of employing materials responsive to magnetic and electric fields in combination with passive materials, and with varied placement in discrete layers and segments through a flexible beam, to design structures capable of satisfying a variety of objective functions simultaneously. These multi-field responsive composite devices, with greater complexity of the embedded combined actuation mechanisms, are able to achieve a wider variety of target shapes compared to traditional unimorph/bimorph structures actuated by a single-field. Additionally, the increased actuation design space facilitates consideration of a wider range of possible objective functions including those related to power consumption, materials’ cost, and work performed. Fabrication of these devices for experimentation is both time-consuming and expensive. As a result, this study will utilize an existing one-dimensional model for electromagnetically-actuated composites and expand its features to include segmentation: the arbitrary placement of any active or passive material type in any layer of a given arbitrarily-sized section of the beam. Ultimately, the goal of this study is to analyze the model by varying characteristic features of multi-field actuated, multi-layered, and segmented devices undergoing large displacements under simultaneously applied fields. Although the model is written arbitrarily for any number of segments, layers within segments, and material types, this study focuses on a base model comprising three material types: electroactive polymer, magneto-active elastomer, and a passive substrate. The initial parameters chosen for the study are the relative lengths (length ratio) of segments, volume of magnetic material, and stiffness of passive material. Two objective functions are chosen. The first is a target shape approximation function, dependent on the errors between the displacements of the computed and the desired shapes. The second calculates a cost based on volume of magnetic material. The effects of the parameters on the objective functions are analyzed by evaluating an array of combinations of parameters; results indicate that each parameter significantly influences the multi-field actuation of the beam, and these correlations are quantitatively analyzed and compared. Concurrently, metrics of power required, structure mass, and other important factors are quantified. As a result, this analysis serves as a precursor to a formal optimization algorithm by determining the usefulness of the chosen objective functions and corresponding input variables for these devices, while also identifying other possible metrics for the design optimization of a multi-field beam.

Multi-Objective Binary Fish School Search

2018 ◽  
pp. 53-72
Author(s):  
Mariana Gomes da Motta Macedo ◽  
Carmelo J. A. Bastos-Filho ◽  
Susana M. Vieira ◽  
João M. C. Sousa
Keyword(s):  
Feature Selection ◽  
Optimization Problems ◽  
Objective Functions ◽  
Binary Decision ◽  
Fish School ◽  
Multi Objective ◽  
Selection For ◽  
Input Variables ◽  
Threshold Technique ◽  
State Of Art

Fish school search (FSS) algorithm has inspired several adaptations for multi-objective problems or binary optimization. However, there is no particular proposition to solve both problems simultaneously. The proposed multi-objective approach binary fish school search (MOBFSS) aims to solve optimization problems with two or three conflicting objective functions with binary decision input variables. MOBFSS is based on the dominance concept used in the multi-objective fish school search (MOFSS) and the threshold technique deployed in the binary fish school search (BFSS). Additionally, the authors evaluate the proposal for feature selection for classification in well-known datasets. Moreover, the authors compare the performance of the proposal with a state-of-art algorithm called BMOPSO-CDR. MOBFSS presents better results than BMOPSO-CDR, especially for datasets with higher complexity.

Control Strategy for the Optimal Operation of a Solar Cooling Installation

2012 ◽  
Author(s):  
Vittorio Verda ◽  
Giorgia Baccino ◽  
Stefano Pizzuti
Keyword(s):  
Energy Consumption ◽  
Solar Radiation ◽  
Control Strategy ◽  
Primary Energy ◽  
Optimal Operation ◽  
Hot Water ◽  
Objective Functions ◽  
Solar Cooling ◽  
Partial Load ◽  
Input Variables

In this paper, a solar cooling installation is analyzed with the aim of optimizing its performances. The system consists of vacuum solar collectors, which supply hot water to a LiBr absorption chiller. A boiler can be used to supply an additional amount of hot water in the case of insufficient solar radiation. In addition, a vapor compression chiller operates as a backup system and integrates the solar driven system in the case of large cooling request. Such system gives multiple operating options, especially at partial load. A model of the system is presented and applied to the real plant. It is shown that if a multi-objective optimization is performed, considering minimum primary energy consumption from fossil fuel and maximum utilization of the absorption system, a Pareto front is obtained. This occurs because the two objective functions are competing. A control strategy based on the use of neural networks is presented. Input variables are the solar radiation, ambient temperature and the cooling request. In this work the control strategy is adjusted in order to reach the minimum fossil energy consumption, but the same approach can be applied with other objective functions.

Investigation of Zinc-Silver Oxide-Thermoplastic Composite for Application in a Biofilm Retardant Urinary Catheter

2019 ◽  
Author(s):  
Oren Gotlib ◽  
Karcher Morris ◽  
Frederick E. Spada ◽  
Madhu Alagiri ◽  
Katy Patras ◽  
...  
Keyword(s):  
Electric Fields ◽  
Silver Oxide ◽  
Urinary Catheter ◽  
Interdisciplinary Teams ◽  
Thermoplastic Composite ◽  
Medical Community ◽  
Active Materials ◽  
E Coli ◽  
Oxide Powders ◽  
Electrochemically Active

Abstract Catheter acquired urinary tract infection (CAUTI) is a significant problem in the medical community. Interdisciplinary teams have coordinated to address this problem, yet there is still a need for an adequate solution. In this study, we investigate an electricidal solution by adopting electrochemically active materials that can be incorporated into a urinary catheter. Zinc and silver oxide powders deposited in the form of patterned electrodes on a thermoplastic substrate are shown to illustrate electricidal properties in urine, including the ability to produce electric fields, pH increases, as well as, formation of hydrogen peroxide. The newly developed samples show promising results for killing planktonic E. coli in a controlled setting.

scholarly journals Direct current resistivity with steel-cased wells

2019 ◽  
Vol 219 (1) ◽  
pp. 1-26
Author(s):  
Lindsey J Heagy ◽  
Douglas W Oldenburg
Keyword(s):  
Electric Fields ◽  
Direct Current ◽  
Carbon Capture ◽  
Survey Design ◽  
Carbon Capture And Storage ◽  
Parameter Study ◽  
Dc Resistivity ◽  
Cross Sectional ◽  
Resistivity Survey ◽  
The Impact

SUMMARY The work in this paper is motivated by the increasing use of electrical and electromagnetic methods in geoscience problems where steel-cased wells are present. Applications of interest include monitoring carbon capture and storage and hydraulic fracturing operations. Also of interest is detecting flaws or breaks in degrading steel-casings—such wells pose serious environmental hazards. The general principles of electrical methods with steel-cased wells are understood and several authors have demonstrated that the presence of steel-cased wells can be beneficial for detecting signal due to targets at depth. However, the success of a direct current (DC) resistivity survey lies in the details. Secondary signals might only be a few per cent of the primary signal. In designing a survey, the geometry of the source and receivers, and whether the source is at the top of the casing, inside of it, or beneath the casing will impact measured responses. Also the physical properties and geometry of the background geology, target and casing will have a large impact on the measured data. Because of the small values of the diagnostic signals, it is important to understand the detailed physics of the problem and also to be able to carry out accurate simulations. This latter task is computationally challenging because of the extreme geometry of the wells, which extend kilometers in depth but have millimeter variations in the radial direction, and the extreme variation in the electrical conductivity which is typically 5–7 orders of magnitude larger than that of the background geology. In this paper, we adopt a cylindrical discretization for numerical simulations to investigate three important aspects of DC resistivity in settings with steel-cased wells. (1) We examine the feasibility of using a surface-based DC resistivity survey for diagnosing impairments along a well in a casing integrity experiment. This parameter study demonstrates the impact of the background conductivity, the conductivity of the casing, the depth of the flaw, and the proportion of the casing circumference that is compromised on amplitude of the secondary electric fields measured at the surface. (2) Next, we consider elements of survey design for exciting a conductive or resistive target at depth. We show that conductive targets generate stronger secondary responses than resistive targets, and that having an electrical connection between the target and well can significantly increase the measured secondary responses. (3) Finally, we examine common strategies for approximating the fine-scale structure of a steel cased well with a coarse-scale representation to reduce computational load. We show that for DC resistivity experiments, the product of the conductivity and the cross-sectional area of the casing is the important quantity for controlling the distribution of currents and charges along its length. To promote insight into the physics, we present results by plotting the currents, charges, and electric fields in each of the scenarios examined. All of the examples shown in this paper are built on open-source software and are available as Jupyter notebooks.

scholarly journals Characteristic Features of Electric Fields Radiated by Cloud Flashes in Himalayan Region

2020 ◽  
Vol 2020 ◽  
pp. 1-8 ◽  
Author(s):  
Pitri Bhakta Adhikari ◽  
Shriram Sharma
Keyword(s):  
Electric Fields ◽  
Late Stage ◽  
Total Duration ◽  
Himalayan Region ◽  
Rugged Terrain ◽  
Geographical Regions ◽  
Time Gap ◽  
Characteristic Features ◽  
Two Stages ◽  
Mountainous Country

Electric fields radiated by cloud flashes that occurred over the rugged terrain of mountainous country Nepal were recorded, analysed, and compared with those from different geographical regions. The total duration of the flash varies from 80 to 469.5 ms. The majority of the cloud flashes were of two stages: the first stage of the majority of the flashes was found to consist of large microsecond scale bipolar pulses having negative initial polarity and the late stage consists of submicrosecond scale pulses having both positive and negative initial polarities. The average durations of the first and second stages are 11.23 and 66.79 ms, respectively, and the time gap between them is 53.57 ms. The cloud pulses led by the negative initial polarity pulses are more compactly distributed and are higher in mountainous countries as compared to those of flashes lead by positive initial polarity pulses, with the average values of interpulse interval being 211.42 and 309.79 μs, respectively.

Origami-Inspired Folding and Unfolding of Structures: Fundamental Investigations of Dielectric Elastomer-Based Active Materials

2013 ◽  
Author(s):  
Saad Ahmed ◽  
Kevin McGough ◽  
Zoubeida Ounaies ◽  
Mary Frecker
Keyword(s):  
Electric Fields ◽  
Breakdown Strength ◽  
Geometric Approach ◽  
Active Materials ◽  
Current Availability ◽  
Low Modulus ◽  
Exhaustive Study ◽  
High Electric Fields ◽  
Mechanical Actuation ◽  
Bending Response

We are investigating the use of dielectric elastomers (DE) to realize origami-inspired folding and unfolding of structures. DEs are compliant materials where the coupled electro-mechanical actuation takes advantage of the low modulus and high breakdown strength of the elastomer. Until recently, pre-straining of relatively thick DE materials was necessary in order to achieve the high electric fields required to trigger electrostatic actuation. However, the current availability of thinner DE materials (ex: VHB 9469PC-130μm, VHB 9473 PC −260 μm) has enabled their actuation at achievable electric fields without the need to pre-strain. In this work, an exhaustive study on the fundamentals of DE actuation is done by exploring thickness actuation mechanism and studying the change in dielectric permittivity; we also take advantage of the thin DEs to build actuators with very large bending angles. In particular, we relate the electrostatically-induced thickness contraction in a DE monomorph to the resulting bending once an inactive substrate is added. Both statically and dynamically induced electromechanical thickness strains are measured, and the experimental data is used as an input to a bender model to predict and optimize bending response; variables such as type of inactive material, number of DE layers, and type of electrodes are examined. We will also experimentally track the changes in the dielectric constant as a function of strain, electrode type, and applied electric field; the measured behavior will be used to model thickness and bending actuation. These fundamental studies are necessary to determine ability and limitation of DE materials in a bender configuration. Finally, bending of the DE actuator is transformed into folding by a novel geometric approach, where different shaped notches are introduced in the inactive substrate. The folding configuration is a step towards realizing active origami structure.

scholarly journals Stability Analysis of an Assembly Process Using Simulation

2020 ◽  
Vol 13 (1) ◽  
pp. 14-24
Author(s):  
László Rónai ◽  
Tamás Szabó
Keyword(s):  
Stability Analysis ◽  
Boundary Point ◽  
Stability Problem ◽  
Mechanical Stability ◽  
Flexible Beam ◽  
Large Displacements ◽  
Assembly Process ◽  
Frictional Contacts ◽  
Beam Elements ◽  
The Stability

This paper deals with an assembly process of batteries with cell holder. The operation involves snap-fitting phenomenon, which is a mechanical stability problem. The structure of the cell holder is modelled with 2D flexible beam elements assuming large displacements. The stability of the equilibrium is investigated taking into consideration non-frictional and Coulomb frictional contacts. The goal of the analysis to determine the boundary point of the feed-motion from which the battery snaps-in to the final assembled position autonomously. The effect of the velocity of the battery feed-motion is also considered with energy approach.

Aerogels Utilizations in Batteries

2021 ◽  
pp. 99-120
Keyword(s):  
Metal Oxides ◽  
Radiation Detector ◽  
Potential Candidate ◽  
Active Materials ◽  
Electrochemically Active ◽  
Composite Aerogels ◽  
Characteristic Features ◽  
Accessible Surface ◽  
Set Up ◽  
Enhanced Surface

Aerogels, a nanoscale 3D mesoporous spongy sample of enhanced surface area, was usually considered as insulator for thermal application, catalyst, and as radiation detector. Presently, it is investigated as potential candidate for electrochemistry due to its inborn capacity to enhance the characteristic features of the surfaces of commercial active materials in batteries and ultracapacitors. Recently composite aerogels which is blended with metal oxides, metal sulphides and so on have been set up as low thickness, profoundly permeable, and large amount of accessible surface and examined as active electrodes. This type of aerogel-based composites challenges the standard manners by that electrochemically active materials are considered, examined, and employed.

Non Linear Active Control of the Dynamic Behavior of Bi-Articulated Flexible Structures

2002 ◽  
Author(s):  
Ste´phane Bochard ◽  
Luc Gaudiller ◽  
Johan Der Hagopian
Keyword(s):  
Nonlinear Control ◽  
Dynamic Behavior ◽  
Control Strategy ◽  
Flexible Structures ◽  
Linear Control ◽  
Multivariable Control ◽  
Flexible Beam ◽  
Large Displacements ◽  
Linear Quadratic ◽  
Non Linear

When vibrating structures are subjected to large displacements, coupling may occur between the vibrations and the displacements inducing possibly strongly non-linear behavior. In this case, linear control algorithms and independent control strategy are no longer suitable. This study deals with the nonlinear control of Bi-articulated structures. A model that combines both finite element (FE) discretization, taking into account strains/electric field coupling, and global behavior is carried out. Multivariable control is carried out by electromechanical and piezoelectric actuators. The control strategy developed consists in weighting the output of parallel state controllers, calculated for the p discretized operating points crossed during the progression of the structure’s dynamic behavior. The multivariable control u is obtained by weighting interpolation functions fi of the linear quadratic control gains Ki of each controller optimized according to large displacements. The first application to Bi-articulated rigid beam systems shows, in comparison with a stable linear control, that non-linear control is by far the better of the two. This is mainly due to increased efficiency of motor torque use. The second application of the proposed nonlinear control algorithm concerns a Bi-articulated flexible beam system modeled by two rigid body modes and five flexible modes. The control obtained is robust regarding both stability and performance. Quasi-steady controlled dynamic behavior is obtained during movement.

Material Orientations and Geometric Effects in Piezoelectric Actuators

Aerospace ◽  
2006 ◽  
Author(s):  
Stephanie A. Wimmer ◽  
Virginia G. DeGiorgi
Keyword(s):  
Electric Fields ◽  
Complex Geometry ◽  
Computational Study ◽  
Piezoelectric Materials ◽  
Complex Loading ◽  
Piezoelectric Actuators ◽  
Tensile Specimen ◽  
Active Materials ◽  
Element Analysis ◽  
Geometric Effects

Piezoelectric materials are active materials that deform in response to both electrical and mechanical loadings. Traditional piezoelectric actuators are designed to exploit this deformation by aligning the material poling axes with the loading axes. However for complex loading or complex geometry this alignment may not maximize the desired actuation due to the anisotropic piezoelectric and elastic properties. A computational study of material and loading axes misalignment was completed to examine the performance of piezoelectric components. The study used finite element analysis to model difference geometries; a simple cylinder, an ASTM E8 tensile specimen, and a customized ASTM E8 tensile specimen. This study looked at electrical only and mechanical only loading. The material axes for each component is rotated from being aligned with the loading axes to various angles. The effect of rotating the material axes is discussed. Variations in stress, electric fields and deformations are noted.

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