Shape Optimized Heliostats Using a Tailored Stiffness Approach

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Li Meng ◽  
Zheng You ◽  
A. F. M. Arif ◽  
Steven Dubowsky
Keyword(s):  
Low Cost ◽  
Spot Size ◽  
Substantial Improvement ◽  
Analytical Models ◽  
Element Analysis ◽  
Optical Efficiency ◽  
Honeycomb Sandwich ◽  
Stiffness Profile ◽  
Optical Ray Tracing ◽  
The Ideal

In central receiver systems, the ideal reflective shape of a heliostat is a section of a paraboloid that adapting with the sun's angle and the mirror's location in the field. Deviation from this shape leads to optical astigmatism that increases the spot size on the receiver aperture, which eventually causes higher energy loss and lower conversion efficiency. However, it is challenging to implement the ideal shape by conventional design and manufacturing methods. In this paper, a novel compliant heliostat design methodology is proposed. By tailoring the two dimensional stiffness profile of a square plate, the paraboloid shape can be formed by a simple, low-cost mechanism with concentrated moment loads on the corners of the plate. The static optimized shapes, which can be easily realized by adjusting the loads according to the locations during heliostat assembly on the site, are suggested as approximations of the ideal shapes. Analytical models were developed in detail for the methodology. Numerical analysis consists of finite element analysis, optical ray tracing, and optimization. The numerical results illustrate that the performance of the shape optimized heliostats using tailored stiffness approach is close to the ideal shapes, providing substantial improvement in optical efficiency and reduction in spot size comparing to the flat mirrors. Furthermore, experiments on a prototype heliostat mechanism with a honeycomb-sandwich panel were conducted to validate the effectiveness of this low-cost shaping approach.

scholarly journals Design of a 3-RPR Flexure System for Optical Switch Assembly

2020 ◽  
Vol 2020 ◽  
pp. 1-9
Author(s):  
Guiyue Kou ◽  
Mouyou Lin ◽  
Changbao Chu
Keyword(s):  
Permanent Magnets ◽  
Optical Switch ◽  
Low Cost ◽  
Mechanical Vibration ◽  
Analytical Models ◽  
Assembly System ◽  
Sensors And Actuators ◽  
Damping Force ◽  
Element Analysis ◽  
Compact Size

In the MEMS optical switch assembly, the collision is likely to happen between the optical fiber and the U-groove of the chip due to the uncontrollable assembly errors. However, these errors can hardly be completely eliminated by the active control using high precision sensors and actuators. It will cause the large acting force and part damage, which further leads to the assembly failure. To solve this question, this paper presents a novel low-cost three-degree-of-freedom (three-DOF) passive flexure system to adaptively eliminate the planar assembly errors. The flexure system adopts three parallel kinematic chains with a novel 3-RPR structure and has a compact size with a diameter of 125 mm and thickness of 12 mm. A novel eddy current damper with the structure of Halbach array permanent magnets (PMs) is utilized to suppress the adverse mechanical vibration of the assembly system from the background disturbances. Analytical models are established to analyze the kinematic, static, and dynamic performances of the system in detail. Finally, finite element analysis is adopted to verify the established models for optimum design. The flexure system can generate a large deformation of 1.02 mm along the two translational directions and 0.02° along the rotational direction below the yield state of the material, and it has much higher natural frequencies than 200 Hz. Moreover, the large damping force means that the designed ECD can suppress the system vibration quickly. The above results indicate the excellent characteristics of the assembly system that will be applied into the optical switch assembly.

scholarly journals Matrix and reinforcement materials for low-cost building isolators: an overview of results from experimental tests and numerical simulations

2019 ◽  
Vol 17 (1) ◽  
Author(s):  
Ingrid E. Madera Sierra ◽  
Johannio Marulanda Casas ◽  
Peter Thomson
Keyword(s):  
Low Cost ◽  
Experimental Tests ◽  
Steel Plates ◽  
Analytical Models ◽  
Compression Tests ◽  
Horizontal Shear ◽  
Scrap Tire ◽  
Element Analysis ◽  
Isolation System ◽  
Scrap Tire Rubber

During the last years several options to replace the conventional steel-reinforced isolators have been investigated using different materials for the matrix and reinforcement to implement isolation system in buildings. As alternatives to natural rubber, recycled elastomers derived from tires and industrial leftover, scrap tire rubber pads and nanocomposite rubber, have been proposed. Furthermore, with the goal of replacing the inflexible, thick steel plates, a wide variety of fabric reinforcements, such as nylon, carbon, polyester, polyamide, glass and thin flexible steel plates, have been investigated. The manufacturing process and connections between the devices and the structure (bonded, unbonded and partially bonded) have also been studied. This paper presents an overview of the results from investigations where the mechanical properties of prototypes were determined through horizontal shear and vertical compression tests and, in certain cases, through finite element analysis with hyperelastic models. In order to facilitate the visualization and comparison between investigations, the results are tabulated and plotted. The organization and presentation of the results allows to identify important aspects implemented in different experimental programs and analytical models developed for low-cost isolators.

scholarly journals Efficient Estimation of CFO-Affected OFDM BER Floor in Small Cells with Resource-Limited IoT End-Points

Sensors ◽  
2020 ◽  
Vol 20 (13) ◽  
pp. 3747
Author(s):  
Adriana Lipovac ◽  
Vlatko Lipovac ◽  
Borivoj Modlic
Keyword(s):  
Orthogonal Frequency Division Multiplexing ◽  
Carrier Frequency Offset ◽  
Signal To Noise Ratio ◽  
Low Cost ◽  
Error Recovery ◽  
Efficient Estimation ◽  
Analytical Models ◽  
Small Cells ◽  
End Points ◽  
Power Delay Profile

Contemporary wireless networks dramatically enhance data rates and latency to become a key enabler of massive communication among various low-cost devices of limited computational power, standardized by the Long-Term Evolution (LTE) downscaled derivations LTE-M or narrowband Internet of Things (NB IoT), in particular. Specifically, assessment of the physical-layer transmission performance is important for higher-layer protocols determining the extent of the potential error recovery escalation upwards the protocol stack. Thereby, it is needed that the end-points of low processing capacity most efficiently estimate the residual bit error rate (BER) solely determined by the main orthogonal frequency-division multiplexing (OFDM) impairment–carrier frequency offset (CFO), specifically in small cells, where the signal-to-noise ratio is large enough, as well as the OFDM symbol cyclic prefix, preventing inter-symbol interference. However, in contrast to earlier analytical models with computationally demanding estimation of BER from the phase deviation caused by CFO, in this paper, after identifying the optimal sample instant in a power delay profile, we abstract the CFO by equivalent time dispersion (i.e., by additional spreading of the power delay profile that would produce the same BER degradation as the CFO). The proposed BER estimation is verified by means of the industry-standard LTE software simulator.

scholarly journals Mitigating the seismic pounding of multi-story buildings in series using linear and nonlinear fluid viscous dampers

2021 ◽  
Vol 21 (4) ◽  
Author(s):  
Hytham Elwardany ◽  
Robert Jankowski ◽  
Ayman Seleemah
Keyword(s):  
Substantial Improvement ◽  
Point Of View ◽  
Steel Buildings ◽  
Viscous Dampers ◽  
Element Analysis ◽  
Fluid Viscous Dampers ◽  
Adjacent Buildings ◽  
In Series ◽  
Linear And Nonlinear ◽  
Nonlinear Fluid

AbstractSeismic-induced pounding between adjacent buildings may have serious consequences, ranging from minor damage up to total collapse. Therefore, researchers try to mitigate the pounding problem using different methods, such as coupling the adjacent buildings with stiff beams, connecting them using viscoelastic links, and installing damping devices in each building individually. In the current paper, the effect of using linear and nonlinear fluid viscous dampers to mitigate the mutual pounding between a series of structures is investigated. Nonlinear finite-element analysis of a series of adjacent steel buildings equipped with damping devices was conducted. Contact surfaces with both contactor and target were used to model the mutual pounding. The results indicate that the use of linear or nonlinear dampers leads to the significant reduction in the response of adjacent buildings in series. Moreover, the substantial improvement of the performance of buildings has been observed for almost all stories. From the design point of view, it is concluded that dampers implemented in adjacent buildings should be designed to resist maximum force of 6.20 or 1.90 times the design independent force in the case of using linear or nonlinear fluid viscous dampers, respectively. Also, designers should pay attention to the design of the structural elements surrounding dampers, because considerable forces due to pounding may occur in the dampers at the maximum displaced position of the structure.

scholarly journals Dynamic Analysis of Honeycomb Sandwich Beam with Multiple Debonds

2012 ◽  
Vol 2012 ◽  
pp. 1-7 ◽  
Author(s):  
B. Saraswathy ◽  
R. Ramesh Kumar ◽  
Lalu Mangal
Keyword(s):  
Analytical Solution ◽  
Transient Analysis ◽  
Sandwich Beam ◽  
Beam Theory ◽  
Beam Length ◽  
Honeycomb Core ◽  
Element Analysis ◽  
Fast Fourier Transform Analysis ◽  
Honeycomb Sandwich ◽  
Nonlinear Transient

Analytical formulation for the evaluation of frequency of CFRP sandwich beam with debond, following the split beam theory, generally underestimates the stiffness, as the contact between the honeycomb core and the skin during vibration is not considered in the region of debond. The validation of the present analytical solution for multiple-debond size is established through 3D finite element analysis, wherein geometry of honeycomb core is modeled as it is, with contact element introduced in the debond region. Nonlinear transient analysis is followed by fast Fourier transform analysis to obtain the frequency response functions. Frequencies are obtained for two types of model having single debond and double debond, at different spacing between them, with debond size up to 40% of beam length. The analytical solution is validated for a debond length of 15% of the beam length, and with the presence of two debonds of same size, the reduction in frequency with respect to that of an intact beam is the same as that of a single-debond case, when the debonds are well separated by three times the size of debond. It is also observed that a single long debond can result in significant reduction in the frequencies of the beam than multiple debond of comparable length.

High-Frequency Vibration Response of Metal Honeycomb Sandwich Structure

2009 ◽  
Vol 79-82 ◽  
pp. 1727-1730 ◽  
Author(s):  
Xiao Dong He ◽  
Xiang Hao Kong ◽  
Li Ping Shi ◽  
Ming Wei Li
Keyword(s):  
High Frequency ◽  
Sandwich Structure ◽  
Dynamic Pressure ◽  
Vibration Response ◽  
Element Analysis ◽  
High Frequency Vibration ◽  
Honeycomb Sandwich ◽  
Vibration Experiment ◽  
Aerial Vehicle ◽  
Honeycomb Sandwich Structure

ARMOR TPS panel is above the whole ARMOR TPS, and the metal honeycomb sandwich structure is the surface of the ARMOR TPS panel. So the metal honeycomb sandwich structure plays an important role in the ARMOR TPS, while it bears the flight dynamic pressure and stands against the flight dynamic calefaction. So the active environment of metal honeycomb sandwich structure is very formidable. We have to discuss any extreme situation, for reason of making sure aerial vehicle is safe. And high-frequency vibration is one of active environment. In this paper we have analyzed high-frequency vibration response of metal honeycomb sandwich structure. We processed high-frequency vibration experiment by simulating true aerial environment. Sequentially we operated high-frequency vibration experiment of metal honeycomb sandwich structure with cracks, notches and holes. Then finite-element analysis was performed by way of validating the experiment results. Haynes214 is a good high temperature alloy material of both face sheet and core at present, so we choose it in this paper.

Performance of Low-Cost 3D Printer in Medical Application

2021 ◽  
Author(s):  
Nor Aiman Sukindar ◽  
Azib Azhari Awang Dahan ◽  
Sharifah Imihezri Syed Shaharuddin ◽  
Nor Farah Huda Abd Halim
Keyword(s):  
Low Cost ◽  
Medical Application ◽  
Fused Deposition Modelling ◽  
3D Printer ◽  
Layer By Layer ◽  
Total Deformation ◽  
Element Analysis ◽  
Porosity Level ◽  
Fused Deposition ◽  
Printing Parameters

Abstract Fused Deposition Modelling (FDM) is an additive manufacturing (AM) process that produces a physical object directly from a CAD design using layer-by-layer deposition of the filament material that is extruded via a nozzle. In industry, FDM has become one of the most used AM processes for the production of low batch quantity and functional prototypes, due to its safety, efficiency, reliability, low cost, and ability to process manufacturing-grade engineering thermoplastic. Recently, the market is flooded with the availability of low-cost printers produced by numerous companies. This research aims to investigate the effect of different porosity levels on a scaffold structure produced using a low-cost 3D printer. Comparisons of these porous structures were made in terms of Von-Mises strain, total deformation, as well as compressive stress. Various porosity levels were created by varying printing parameters, including layer height, infill density, and shell thickness by slicing the initial solid CAD file using Repetier Host 3D printing software. Finite Element Analysis (FEA) simulation was then performed on the created scaffold structures by using Ansys Workbench 19.2. The simulation result indicates that the greater porosity level will result in higher total deformation of the structure. Meanwhile, the compression test shows that the minimum strength value obtained was favourable at 22 MPa and had exceeded that of the trabecular femur (15 MPa). However, its porosity level (maximum at 52%) was still below that of the minimum threshold of porosity level of 70 percent. However, the printing parameters currently used can be adjusted in the future. Therefore, it was deduced that the low-cost 3D printer offers promising potential to fabricate different porosity structures with multiple outcomes.

Design of Microfabricated Mechanically Interlocking Metamaterials for Reworkable Heterogeneous Integration

2021 ◽  
Author(s):  
Geoffrey Garcia ◽  
Kody Wakumoto ◽  
Joseph Brown
Keyword(s):  
Analytical Models ◽  
Elastic Behavior ◽  
Heterogeneous Integration ◽  
Element Analysis ◽  
Microelectronic Devices ◽  
Mechanical Metamaterials ◽  
Dry Adhesives ◽  
Cantilever Array ◽  
Mechanical Bonding ◽  
Interconnect Technology

Abstract Next–generation interconnects utilizing mechanically interlocking structures enable permanent and reworkable joints between microelectronic devices. Mechanical metamaterials, specifically dry adhesives, are an active area of research which allows for the joining of objects without traditional fasteners or adhesives, and in the case of chip integration, without solder. This paper focuses on reworkable joints that enable chips to be removed from their substrates to support reusable device prototyping and packaging, creating the possibility for eventual pick-and-place mechanical bonding of chips with no additional bonding steps required. Analytical models are presented and are verified through Finite Element Analysis (FEA) assuming pure elastic behavior. Sliding contact conditions in FEA simplify consideration of several design variations but contribute ~10% uncertainty relative to experiment, analysis, and point-loaded FEA. Two designs are presented; arrays of flat cantilevers have a bond strength of 6.3 kPa, and non-flat cantilevers have a strength of 29 kPa. Interlocking designs present self-aligning in-plane forces that emerge from translational perturbation from perfect alignment. Stresses exceeding the material yield stress during adhesion operations present a greater concern for repeatable operation of compliant interlocking joints and will require further study quantifying and accommodating plastic deformation. Designs joining a rigid array with a complementary compliant cantilever array preserve the condition of reworkability for the surface presenting the rigid array. Eventual realization of interconnect technology based on this study will provide a great improvement of functionality and adaptability in heterogeneous integration and microdevice packaging.

Buckling analysis of natural fiber reinforced composites

2021 ◽  
Vol 7 (2) ◽  
pp. 58
Author(s):  
Celal Çakıroğlu ◽  
Gebrail Bekdaş
Keyword(s):  
Composite Plate ◽  
Natural Fiber ◽  
Low Cost ◽  
Natural Fibers ◽  
Experimental Studies ◽  
Fiber Reinforced Composites ◽  
Fiber Types ◽  
Reinforced Composites ◽  
Fiber Reinforced ◽  
Element Analysis

In the recent years natural fiber reinforced composites are increasingly receiving attention from the researchers and engineers due to their mechanical properties comparable to the conventional synthetic fibers and due to their ease of preparation, low cost and density, eco-friendliness and bio-degradability. Natural fibers such as kenaf or flux are being considered as a viable replacement for glass, aramid or carbon. Extensive experimental studies have been carried out to determine the mechanical behavior of different natural fiber types such as the elastic modulus, tensile strength, flexural strength and the Poisson’s ratio. This paper presents a review of the various experimental studies in the field of fiber reinforced composites while summarizing the research outcome about the elastic properties of the major types of natural fiber reinforced composites. Furthermore, the performance of a kenaf reinforced composite plate is demonstrated using finite element analysis and results are compared to a glass fiber reinforced laminated composite plate.

scholarly journals The Bending Responses of Sandwich Panels with Aluminium Honeycomb Core and CFRP Skins Used in Electric Vehicle Body

2018 ◽  
Vol 2018 ◽  
pp. 1-11 ◽  
Author(s):  
Yong Xiao ◽  
Yefa Hu ◽  
Jinguang Zhang ◽  
Chunsheng Song ◽  
Xiangyang Huang ◽  
...  
Keyword(s):  
Electric Vehicle ◽  
Failure Modes ◽  
Sandwich Panels ◽  
Vehicle Body ◽  
Stacking Sequence ◽  
Honeycomb Core ◽  
Fibre Direction ◽  
Element Analysis ◽  
Honeycomb Sandwich ◽  
Carbon Fibre Reinforced Plastic

The aim of this paper was to investigate bending responses of sandwich panels with aluminium honeycomb core and carbon fibre-reinforced plastic (CFRP) skins used in electric vehicle body subjected to quasistatic bending. The typical load-displacement curves, failure modes, and energy absorption are studied. The effects of fibre direction, stacking sequence, layer thickness, and loading velocity on the crashworthiness characteristics are discussed. The finite element analysis (FEA) results are compared with experimental measurements. It is observed that there are good agreements between the FEA and experimental results. Numerical simulations and experiment predict that the honeycomb sandwich panels with ±30° and ±45° fibre direction, asymmetrical stacking sequence (45°/−45°/45°/−45°), thicker panels (0.2 mm∼0.4 mm), and smaller loading velocity (5 mm/min∼30 mm/min) have better crashworthiness performance. The FEA prediction is also helpful in understanding the initiation and propagation of cracks within the honeycomb sandwich panels.

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