scholarly journals Bio-inspired origami metamaterials with metastable phases through mechanical phase transitions

2021 ◽  
pp. 1-13
Author(s):  
Ke Liu ◽  
Tomohiro Tachi ◽  
Glaucio H. Paulino
Keyword(s):  
Structural Instability ◽  
Two Dimensions ◽  
Important Application ◽  
Metastable Phases ◽  
Design Parameters ◽  
Local Geometry ◽  
Unit Cells ◽  
Geometric Origin ◽  
Wave Guides ◽  
Multi Phase

Abstract Structural instability, once a catastrophic phenomenon to be avoided in engineering applications, is being harnessed to improve functionality of structures and materials, and has catalyzed a substantial research in the field. One important application is to create functional metamaterials that deform their internal structure to adjust performance, resembling phase transformations in natural materials. In this paper, we propose a novel origami pattern, named the Shrimp pattern, with application to multi-phase architected metamaterials whose phase transition is achieve mechanically by snap-through. The Shrimp pattern consists of units that can be easily tessellated in two dimensions, either periodically with homogeneous local geometry, or non-periodically with heterogeneous local geometries. We can use a few design parameters to program the unit cell to become either monostable or bistable, and tune the energy barrier between the bistable states. By tessellating these unit cells into an architected metamaterial, we can create complex yet navigable energy landscape, leading to multiple metastable phases of the material. As each phase has different geometry, the metamaterial can switch between different mechanical properties and shapes. The geometric origin of the multi-stable behavior implies that our designs are scale-independent, making them candidates for a variety of innovative applications, including reprogrammable materials, reconfigurable acoustic wave guides, and microelectronic mechanical systems and energy storage systems.

Dynamics of the Flows in Micro-Channels of a Capillary Pumped Loop (CPL) Evaporator

2001 ◽  
Author(s):  
Hyoung-In Lee ◽  
Hye-Jung Cho ◽  
In-Seob Song ◽  
Ju-Hyeong Lee
Keyword(s):  
Viscous Force ◽  
Design Parameters ◽  
Pressure Jump ◽  
Nonlinear Feedback ◽  
Capillary Pumped Loop ◽  
Heating And Cooling ◽  
Micro Channels ◽  
Capillary Pumped Loops ◽  
Dry Out ◽  
Multi Phase

Abstract Cooling of electronic components is often limited by space availability and power consumption. Capillary-pumped loops (CPL) are utilized to achieve a coolant circulation via self-activated capillarity (Faghri, 1995). However, CPL is extremely unstable due to a nonlinear feedback among capillarity, viscous force, and heat transfer. Conventional refrigeration theories, which usually allow a larger pressure jump due to an external pumping, failed to explain the CPL cycle. The dynamics of a flow through a CPL cooling cycle is investigated with a particular attention to the flow in the micro-channels. Full numerical approaches, by which multi-component multi-phase flows are solved, tend to obscure the engineers from identifying outstanding design parameters. Instead, one here adopts several simplified semi-analyitic approaches, namely, models based on single-phase flows with discrete zones of heating and cooling. The analytical and numerical results could explain some general tendencies in the dynamical features like dry-out and flooding. However, the problem still requires closer and more realistic modeling.

A Two-Dimensional Adjustable Constant-Force Mechanism

2019 ◽  
Vol 142 (6) ◽  
Author(s):  
Yu-Ling Kuo ◽  
Chao-Chieh Lan
Keyword(s):  
Limited Range ◽  
Two Dimensions ◽  
Working Environment ◽  
Design Parameters ◽  
Constant Force ◽  
Two Dimensional ◽  
Output Force ◽  
Constant Output ◽  
Force Variation ◽  
Force Mechanism

Abstract Constant-force mechanisms (CFMs) can produce an almost invariant output force over a limited range of input displacement. Without using additional sensor and force controller, adjustable CFMs can passively produce an adjustable constant output force to interact with the working environment. In the literature, one-dimensional CFMs have been developed for various applications. This paper presents the design of a novel CFM that can produce adjustable constant force in two dimensions. Because an adjustable constant force can be produced in each radial direction, the proposed adjustable CFM can be used in applications that require two-dimensional force regulation. In this paper, the design formulation and simulation results are presented and discussed. Equations to minimize the output force variation are given to choose the design parameters optimally. A prototype of the two-dimensional CFM is tested to demonstrate the effectiveness and accuracy of adjustable force regulation. This novel CFM is expected to be used in machines or robots to interact friendly with the environment.

scholarly journals Sloshing response of partially filled rectangular tank under periodic horizontal ground motion.

2018 ◽  
Vol 172 ◽  
pp. 01005
Author(s):  
Amiya Pandit ◽  
Kishore Chandra Biswal
Keyword(s):  
Structural Damage ◽  
Hydrodynamic Pressure ◽  
Structural Instability ◽  
Liquid System ◽  
Two Dimensions ◽  
Point Of View ◽  
Base Shear ◽  
Rectangular Tank ◽  
Internal Objects ◽  
Forced Vibration Analysis

The event caused due to the movement of the unrestricted free surface liquid in container due to any external excitation is known as sloshing. The problem of liquid sloshing phenomenon in stationary or in moving container is a great matter of concern for many researchers and engineers. The containers may range from a cup of milk, ponds, and lakes to fuel tanks of launching vehicles and cargo ships carrying variety of liquids such as oil, liquefied natural gas, and chemical fluids. As a result of sloshing there is spillage of liquid from the containers and it causes structural instability and structural damage. Due to these reasons, liquid retaining structures which are special in construction and in function from an engineering point of view must be constructed well to be resistant against oscillation of the liquid due to external excitations. The amount of liquid participating in the sloshing motion depends on the shape of tank, the liquid depth, internal objects, if any, orientation, duration, amplitude, and frequency contents of external excitations. This present study focuses on the forced vibration analysis of partially filled two-dimensional rigid rectangular tank numerically. A Finite element (FE) code in two dimensions is developed to understand the behavior of sloshing. This method is competent enough of evaluating both impulsive and convective response of tank-liquid system in terms of base shear and hydrodynamic pressure distribution along the walls of the containers.

scholarly journals A review on integration of lightweight gradient lattice structures in additive manufacturing parts

2020 ◽  
Vol 12 (6) ◽  
pp. 168781402091695
Author(s):  
Asliah Seharing ◽  
Abdul Hadi Azman ◽  
Shahrum Abdullah
Keyword(s):  
Additive Manufacturing ◽  
Weight Ratio ◽  
Design Parameters ◽  
Layer By Layer ◽  
Lattice Structures ◽  
Unit Cells ◽  
Metallic Additive ◽  
Manufacturing Techniques ◽  
Future Work ◽  
Design Freedom

This review analyses the design, mechanical behaviors, manufacturability, and application of gradient lattice structures manufactured via metallic additive manufacturing technology. By varying the design parameters such as cell size, strut length, and strut diameter of the unit cells in lattice structures, a gradient property is obtained to achieve different levels of functionalities and optimize strength-to-weight ratio characteristics. Gradient lattice structures offer variable densification and porosities; and can combine more than one type of unit cells with different topologies which results in different performances in mechanical behavior layer-by-layer compared to non-gradient lattice structures. Additive manufacturing techniques are capable of manufacturing complex lightweight parts such as uniform and gradient lattice structures and hence offer design freedom for engineers. Despite these advantages, additive manufacturing has its own unique drawbacks in manufacturing lattice structures. The rules and strategies in overcoming the constraints are discussed and recommendations for future work were proposed.

Modelling of circular wave guides

1992 ◽  
Vol 70 (10-11) ◽  
pp. 1092-1098 ◽  
Author(s):  
A. Delage ◽  
K. A. McGreer ◽  
E. Rainville
Keyword(s):  
Integrated Circuit ◽  
Beam Propagation Method ◽  
Two Dimensions ◽  
Effective Index ◽  
Radius Of Curvature ◽  
Index Method ◽  
Photonic Integrated Circuit ◽  
Circular Arcs ◽  
Straight Line ◽  
Wave Guides

In many circumstances the design of interconnects in a photonic integrated circuit can be simplified by using low loss curved wave guides in the shapes of circular arcs. Radiative losses associated with the curvature have been computed as a function of the radius of curvature. The technique takes advantage of the effective index method to reduce the problem from two dimensions to one dimension (1D) and uses a change of coordinate that transforms an arc of circle into a straight line. This transformation results in a monotonous increase of the refractive index as function of r (the distance from the centre of the circle) for original constant index regions. The new system is solved by discretizing this varying effective index onto many small layers of constant index over a window large enough to contain the region where the field is not negligible. A multilayer algorithm in 1D is then used to find complex propagation constants in which the imaginary part is related to the fundamental energy loss owing to the curvature. The solution also gives the shape of the field necessary to match the mode profiles at the junction between the straight and curved part of the wave guide. The basic change of variable has been extended to the finite difference solution of the scalar wave equation and to the beam propagation method.

Rotor Design to Attenuate Flow Distortion—Part I: A Semiactuator Disk Analysis

1975 ◽  
Vol 97 (1) ◽  
pp. 11-20 ◽  
Author(s):  
C. T. Savell ◽  
W. R. Wells
Keyword(s):  
Wave Length ◽  
Design Parameters ◽  
Transmission Characteristics ◽  
Flow Distortion ◽  
One Dimensional ◽  
Inlet Distortion ◽  
Rotor Design ◽  
Blade Cascade ◽  
Wave Guides ◽  
Parametric Studies

The transfer of stationary circumferential inlet distortion through a rotor is analyzed using unsteady semiactuator disk cascade theory. This method models the blade cascade as one-dimensional wave guides and describes the transmission characteristics of a rotor to be a function of the distortion wave length and the length of the rotor chord, as well as the normal design parameters. Two parametric studies on the response of a loaded rotor to inlet distortions are done for a single rotor operating at off design conditions and a number of rotors operating at their design points. Fourier series representations of arbitrary distortion wave shapes are used for comparison with experimental data.

scholarly journals Optimal Design of Novel Electromagnetic-Ring Active Balancing Actuator with Radial Excitation

2021 ◽  
Vol 34 (1) ◽  
Author(s):  
Xin Pan ◽  
Xiaotian He ◽  
Haiqi Wu ◽  
Chuanlong Ju ◽  
Zhinong Jiang ◽  
...  
Keyword(s):  
Permanent Magnets ◽  
Element Model ◽  
Structural Instability ◽  
Design Parameters ◽  
Radial Excitation ◽  
Driving Voltage ◽  
Negative Effects ◽  
Compact Structure ◽  
Active Balancing ◽  
Torque Measurements

AbstractImbalance vibration is a typical failure mode of rotational machines and has significant negative effects on the efficiency, accuracy, and service life of equipment. To automatically reduce the imbalance vibration during the operational process, different types of active balancing actuators have been designed and widely applied in actual production. However, the existing electromagnetic-ring active balancing actuator is designed based on an axial excitation structure which can cause structural instability and has low electromagnetic driving efficiency. In this paper, a novel radial excitation structure and the working principle of an electromagnetic-ring active balancing actuator with a combined driving strategy are presented in detail. Then, based on a finite element model, the performance parameters of the actuator are analyzed, and reasonable design parameters are obtained. Self-locking torque measurements and comparative static and dynamic experiments are performed to validate the self-locking torque and driving efficiency of the actuator. The results indicate that this novel active balancing actuator has sufficient self-locking torque, achieves normal step rotation at 2000 r/min, and reduces the driving voltage by 12.5%. The proposed novel balancing actuator using radial excitation and a combination of permanent magnets and soft-iron blocks has improved electromagnetic efficiency and a more stable and compact structure.

scholarly journals Minimization of Mutual Coupling in Arrays using Cross-shape EBG

2019 ◽  
Vol 8 (11) ◽  
pp. 2599-2603
Keyword(s):  
Band Gap ◽  
Mutual Coupling ◽  
Unit Cell ◽  
Operating Frequency ◽  
Design Parameters ◽  
Substrate Thickness ◽  
Electromagnetic Band Gap ◽  
Area Reduction ◽  
Unit Cells ◽  
Current Scenario

In current scenario, the utilization of Electromagnetic Band Gap (EBG) has increased tremendously in microwave engineering. Mutual Coupling (MC) is a significant constraint to be measured in antennas specialization when used with arrays. Electromagnetic Band-Gap (EBG) is a well-known procedure applied in microwave and RF region due to its inherent bandgap feature at predefined frequency. MC arises due to surface currents excited on printed arrays whenever the substrate thickness ℇr > 1. By incorporating EBG in between array elements, various parameters like bandwidth, gain, radiation pattern, directivity, and current distribution can be improved based on the design parameters. Compactness and patch area reduction can be achieved through suitable unit cells of EBG structures. A patch performance is effective with better radiation characteristics and good return loss provided the operating frequency fall within the operating frequency of the unit-cell of the EBG. The unit cell can be constructed depending on the reflection phase, dispersion diagram. In this, a cross-EBG is used to enhance the MC between the arrays. The Cross EBG size is 6.3mm x 6.3mm. The antenna resonates at 5.8GHz WLAN range.

scholarly journals Super Unit Cells in Aperture-Based Metamaterials

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Dragan Tanasković ◽  
Zoran Jakšić ◽  
Marko Obradov ◽  
Olga Jakšić
Keyword(s):  
Refractive Index ◽  
Optical Transmission ◽  
Negative Refractive Index ◽  
Local Geometry ◽  
Important Class ◽  
Additional Degree ◽  
Spectral Dispersion ◽  
Unit Cells ◽  
Electromagnetic Metamaterials ◽  
Small Additive

An important class of electromagnetic metamaterials are aperture-based metasurfaces. Examples include extraordinary optical transmission arrays and double fishnets with negative refractive index. We analyze a generalization of such metamaterials where a simple aperture is now replaced by a compound object formed by superposition of two or more primitive objects (e.g., rectangles, circles, and ellipses). Thus obtained “super unit cell” shows far richer behavior than the subobjects that comprise it. We show that nonlocalities introduced by overlapping simple subobjects can be used to produce large deviations of spectral dispersion even for small additive modifications of the basic geometry. Technologically, some super cells may be fabricated by simple spatial shifting of the existing photolithographic masks. In our investigation we applied analytical calculations andab initiofinite element modeling to prove the possibility to tailor the dispersion including resonances for plasmonic nanocomposites by adjusting the local geometry and exploiting localized interactions at a subwavelength level. Any desired form could be defined using simple primitive objects, making the situation a geometrical analog of the case of series expansion of a function. Thus an additional degree of tunability of metamaterials is obtained. The obtained designer structures can be applied in different fields like waveguiding and sensing.

scholarly journals Strain and the optoelectronic properties of nonplanar phosphorene monolayers

2015 ◽  
Vol 112 (19) ◽  
pp. 5888-5892 ◽  
Author(s):  
Mehrshad Mehboudi ◽  
Kainen Utt ◽  
Humberto Terrones ◽  
Edmund O. Harriss ◽  
Alejandro A. Pacheco SanJuan ◽  
...  
Keyword(s):  
Material Properties ◽  
Optoelectronic Properties ◽  
Structural Defects ◽  
Local Geometry ◽  
2D Material ◽  
Unit Cells ◽  
Intimate Relation ◽  
Conical Structure ◽  
Geometrical Effect

Lattice kirigami, ultralight metamaterials, polydisperse aggregates, ceramic nanolattices, and 2D atomic materials share an inherent structural discreteness, and their material properties evolve with their shape. To exemplify the intimate relation among material properties and the local geometry, we explore the properties of phosphorene––a new 2D atomic material––in a conical structure, and document a decrease of the semiconducting gap that is directly linked to its nonplanar shape. This geometrical effect occurs regardless of phosphorene allotrope considered, and it provides a unique optical vehicle to single out local structural defects on this 2D material. We also classify other 2D atomic materials in terms of their crystalline unit cells, and propose means to obtain the local geometry directly from their diverse 2D structures while bypassing common descriptions of shape that are based from a parametric continuum.

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