scholarly journals An Electrostatic Self-Excited Resonator with Pre-Tension/Pre-Compression Constraint for Active Rotation Control

Micromachines ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 650
Author(s):  
Ruide Yun ◽  
Yangsheng Zhu ◽  
Zhiwei Liu ◽  
Jianmei Huang ◽  
Xiaojun Yan ◽  
...  
Keyword(s):  
Maximum Velocity ◽  
Flapping Wings ◽  
Variable Velocity ◽  
Beam Length ◽  
Dc Voltage ◽  
Middle Position ◽  
Simply Supported ◽  
Maximum Value ◽  
Constraint Structure

We report a novel electrostatic self-excited resonator driven by DC voltage that achieves variable velocity-position characteristics via applying the pre-tension/pre-compression constraint. The resonator consists of a simply supported micro-beam, two plate electrodes, and two adjustable constraint bases, and it can be under pre-compression or pre-tension constraint by adjusting the distance L between two constraint bases (when beam length l > L, the resonator is under pre-compression and when l < L, it is under pre-tension). The oscillating velocity of the beam reaches the maximum value in the position around electrodes under the pre-compression constraint and reaches the maximum value in the middle position between two electrodes under the pre-tension condition. By changing the constraint of the microbeam, the position of the maximum velocity output of the oscillating beam can be controlled. The electrostatic self-excited resonator with a simple constraint structure under DC voltage has great potential in the field of propulsion of micro-robots, such as active rotation control of flapping wings.

scholarly journals Flexural Capacity of Steel-Concrete Composite Beams under Hogging Moment

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Jing Liu ◽  
Fa-xing Ding ◽  
Xue-mei Liu ◽  
Zhi-wu Yu ◽  
Zhe Tan ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Flexural Strength ◽  
Composite Beams ◽  
The Other ◽  
Transverse Reinforcement ◽  
Beam Length ◽  
Simply Supported ◽  
Shear Connection ◽  
Abaqus Software

This study investigates the flexural strength of simply supported steel-concrete composite beams under hogging moment. A total of 24 composite beams are included in the experiments, and ABAQUS software is used to establish finite element (FE) models that can simulate the mechanical properties of composite beams. In a parametric study, the influences of several major parameters, such as shear connection degree, stud arrangement and diameter, longitudinal and transverse reinforcement ratios, loading manner, and beam length, on flexural strength were investigated. Thereafter, three standards, namely, GB 50017, Eurocode 4, and BS 5950, were used to estimate the flexural strength of the composite beams. These codes were also compared with experimental and numerical results. Results indicate that GB 50017 may provide better estimations than the other two codes.

scholarly journals Analysis of Longitudinal Force of Beam and Rail of Continuously Welded Rails (CWR) on Railway Bridge

2022 ◽  
Vol 2148 (1) ◽  
pp. 012065
Author(s):  
Zhiping Zeng ◽  
Ji Hu ◽  
Qiang Zeng ◽  
Zhibin Huang ◽  
Huatuo Yin ◽  
...  
Keyword(s):  
Element Model ◽  
Longitudinal Force ◽  
Relative Displacement ◽  
Railway Bridge ◽  
Simply Supported ◽  
Maximum Value ◽  
Constant Resistance ◽  
Left And Right ◽  
The Right ◽  
Track Bridge

Abstract To study the longitudinal force of CWR on viaduct, a track-bridge-pier finite element model is established. Taking a multi-span simply supported beam with a maximum span of 32.7m of an elevated CWR as an example, the additional expansion and contraction forces, displacement between rail and beam and the force of pier are calculated, and whether the rail stress meets the requirements when setting constant resistance fasteners is checked. The results show that: (1) For the left and right lines, the maximum additional expansion forces of single strand rail are both 211.13kN, and the maximum relative displacements between beam and rail are both 6.572mm. (2) The maximum value of the additional expansion and contraction forces and the relative displacement between beam and rail of the same line occur at the same position. The left line is at ZFZ29 pier and the right line is at ZFS31 pier. (3) The maximum force of pier in this section is 500.80kN, and the pier numbers are ZFZ27 and ZFS29. (4) The rail stress is less than the allowable stress of 352MPa, and the rail strength meets the requirements.

An Experimental Investigation of Beam Stresses Produced by Oblique Impact of a Steel Sphere

1956 ◽  
Vol 23 (4) ◽  
pp. 606-611
Author(s):  
D. M. Cunningham ◽  
Werner Goldsmith
Keyword(s):  
Experimental Investigation ◽  
Normal Incidence ◽  
Oblique Impact ◽  
Angle Of Incidence ◽  
Bending Stress ◽  
Beam Size ◽  
Beam Length ◽  
Oblique Collision ◽  
Steel Sphere ◽  
Simply Supported

Abstract An experimental investigation designed to study the phenomenaincident to the oblique collision of 1/2-in-diam steel spheres with mild-steel and annealed drill-rod beams at oblique angles of incidence has been undertaken. Initial ball velocities ranged from 30 ft/sec to 150 ft/sec, beam sizes varied from 1/4 in. × 1/4 in. to 3/4 in. × 3/4 in., angles of incidence were chosen from 85 deg to normal incidence, and simply supported, clamped, and free beams were employed. Information is reported concerning the values of maximum bending stress at various positions along the beam as function of the angle of incidence and as a function of beam size for various angles of incidence. The progressive dispersion of the initial transient has been examined in detail. The effect of end supports, effective beam length, and repetitive shots into the same hole upon stress are described.

scholarly journals Vibrational energy harvesting device with magnetic tip mass

2018 ◽  
Vol 211 ◽  
pp. 05001
Author(s):  
Fedor Fedulov ◽  
Leonid Fetisov
Keyword(s):  
Magnetic Field ◽  
Energy Harvesting ◽  
Vibrational Energy ◽  
Voltage Level ◽  
Dc Voltage ◽  
Ac Magnetic Field ◽  
Charging Time ◽  
Maximum Value ◽  
Tip Mass ◽  
Vibrational Energy Harvesting

In this paper, the energy-harvesting device based on vibrational piezoelectric transducer for AC magnetic field conversion is presented. The harvester consists of the transducer and an AC/DC-converter. The load dependencies of the transducer showed that the maximal rms power reached a peak of Prms = 37 μW at f = 50 Hz and Prms = 200 μW at f = 48 Hz. If the harvester is placed into an external AC magnetic field h(t) of the frequency f = 48 Hz and constant amplitude of h = 5 Oe, DC voltage of fixed level (1.8 V, 2.5 V, 3.3 V or 3.6 V) is available on the output. Charging time depends on the voltage level and has a maximum value of t ≈ 11 s for 3.6 V and minimum value t ≈ 6 s for 1.8 V.

scholarly journals Explosion waves and shock waves. VII.The velocity of detonation in cast T.N.T

1949 ◽  
Vol 197 (1048) ◽  
pp. 51-72 ◽  
Keyword(s):  
Cross Section ◽  
Crystal Size ◽  
Maximum Velocity ◽  
Precise Determination ◽  
Direct Measure ◽  
And Shock Waves ◽  
Maximum Value ◽  
Full Cross Section ◽  
Velocity Of Detonation

The Buxton rotating-mirror camera has been used for the precise determination of velocities of detonation in cylinders of cast T.N.T. The method has an advantage over the indirect Dautriche method in that it affords a direct measure of the velocity. The effects on the velocity of detonation of the following variables have been studied in so far as each can be independently varied: ( a ) the purity and crystal size, ( b ) the diameter and ( c ) the degree of confinement. Correlation of the observations with those of the velocity of detonation shows that cast T.N.T. may undergo stable or unstable detonation according as the crystals are small or large respectively. The unstable regime is characterized by the failure of the detonation wave to be propagated uniformly over the full cross-section of the cylinder of explosive. The velocity of detonation of T.N.T. rises as the diameter of the cylinder is increased from a ‘boundary diameter’, below which there is no propagation, to a ‘limiting diameter’ at which the velocity reaches a maximum value. In castings of density 1.625 the maximum velocity is 6950 m./sec. The value of the boundary diameter is a measure of the sensitivity to propagation. The effect of heavy confinement Is to reduce the boundary and limiting diameters; the maximum velocity, however, remains unaltered and confinement has therefore the same effect as an increase in diameter in an unconfined charge.

scholarly journals Neutrally stable wave motions in thermally stratified Poiseuille-Couette flow

1998 ◽  
Vol 40 (1) ◽  
pp. 123-144 ◽  
Author(s):  
James P. Denier ◽  
Andrew P. Bassom
Keyword(s):  
Boundary Layer ◽  
Couette Flow ◽  
Flow Structure ◽  
Maximum Velocity ◽  
Streamwise Velocity ◽  
Asymptotic Structure ◽  
Thermal Buoyancy ◽  
Maximum Value ◽  
Limiting Behaviour ◽  
Wave Modes

AbstractThe influence of thermal buoyancy on neutral wave modes in Poiseuille-Couette flow is considered. We examine the modifications to the asymptotic structure first described by Mureithi, Denier & Stott [16], who demonstrated that neutral wave modes in a strongly thermally stratified boundary layer are localized at the position where the streamwise velocity attains its maximum value. The present work demonstrates that such a flow structure also holds for Poiseuille-Couette flow but that a new flow structure emerges as the position of maximum velocity approaches the wall (and which occurs as the level of shear, present as a consequence of the Couette component of the flow, is increased). The limiting behaviour of these wave modes is discussed thereby allowing us to identify the parameter regime appropriate to the eventual restabilization of the flow at moderate levels of shear.

scholarly journals Prestress Losses in Concrete Rafters with Openings

2020 ◽  
Vol 10 (2) ◽  
pp. 5512-5519
Author(s):  
F. J. Alkhafaji ◽  
A. F. Izzet
Keyword(s):  
Cross Section ◽  
Prestressed Concrete ◽  
Beam Length ◽  
Prestress Loss ◽  
Prestress Losses ◽  
Simply Supported ◽  
Prestressing Force ◽  
Size Number ◽  
The Cross ◽  
Code Provisions

In this paper, experimental work was conducted to evaluate the losses in prestressing force of 13 (12 perforated and 1 solid) simply supported prestressed concrete rafters. All beams had the same dimensions and reinforcements. The tested beams were divided into four main groups and three additional subgroups were driven. These groups were classified according to size, number, and configuration of the openings, and the orientation of the posts (vertical or inclined). Regarding the prestress losses that have been affected by the cross-section properties, the provision of the codes is applicable only to prismatic solid beams, so non-prismatic or moreover perforated beams also need to be studied. This paper aims to propose a method based on the same code provisions but taking into consideration the cross-section variation along the beam length. The proposed method divides the overall length of the rafter into a number of assumed prismatic segments with heights measured at centers. Then, the overall prestress loss is found as the sum of these segments weighed by the ratios of the length of each beam segment to the overall length. The experimental results of the proposed method ranged from 84.749% to 95.607% denoting its validity.

Design and Simulation of a Bending Actuator Based on Super-Aligned Carbon Nanotube/Polymer Composites

2015 ◽  
Vol 814 ◽  
pp. 107-112
Author(s):  
Wei Zhang ◽  
Ming Cen Weng ◽  
Lu Zhuo Chen
Keyword(s):  
Carbon Nanotube ◽  
Polymer Composites ◽  
Coefficient Of Thermal Expansion ◽  
Thickness Ratio ◽  
Dc Voltage ◽  
Maximum Value ◽  
Bending Actuator ◽  
Carbon Nanotube Composite ◽  
Mathematica Software ◽  
The Relationship

Super-aligned carbon nanotube films are carbon nanotube macrostructures which have excellent orientations. The bending actuator based on super-aligned carbon nanotube/polymer composites can make a significant controllable bending deformation under a very low DC voltage (< 700 V/m). In this paper, we explored how to make the thermal induced actuator reach maximal deformation. By theoretical modeling and simulation through Mathematica software, the relationship between free-end displacement of the actuator and actuator length, thickness (or thickness ratio) of two layers, difference of coefficient of thermal expansion between two layers, temperature variation and other parameters were studied. Simulation results showed that the deformation is greatly influenced by the thickness ratio of the two layers of the actuator. The deformation displacement reaches a maximum value with a specified thickness ratio. This study may provide valuable theoretical references for the experimental design of carbon nanotube composite actuators.

scholarly journals Evolution of the flow field in decaying active regions

2018 ◽  
Vol 620 ◽  
pp. A122 ◽  
Author(s):  
H. Strecker ◽  
N. Bello González
Keyword(s):  
Flow Field ◽  
Velocity Profile ◽  
Maximum Velocity ◽  
Active Regions ◽  
Horizontal Velocity ◽  
Radial Dependence ◽  
Analysis Method ◽  
Maximum Value ◽  
Flow Changes ◽  
Radial Outflow

Context. Fully fledged sunspots are known to be surrounded by a radial outflow called the moat flow. Aims. We investigate the evolution of the horizontal flow field around sunspots during their decay, that is, from fully fledged to naked spots, after they loose the penumbra, to the remnant region after the spot has fully dissolved. Methods. We analysed the extension and horizontal velocity of the flow field around eight sunspots using SDO/HMI Doppler maps. By assuming a radially symmetrical flow field, the applied analysis method determines the radial dependence of the azimuthally averaged flow field. For comparison, we studied the flow in supergranules using the same technique. Results. All investigated, fully fledged sunspots are surrounded by a flow field whose horizontal velocity profile decreases continuously from 881 m s−1 at 1.1 Mm off the spot boundary, down to 199 m s−1 at a mean distance of 11.9 Mm to that boundary, in agreement with other studies. Once the penumbra is fully dissolved, however, the velocity profile of the flow changes: The horizontal velocity increases with increasing distance to the spot boundary until a maximum value of about 398 m s−1 is reached. Then, the horizontal velocity decreases for farther distances to the spot boundary. In supergranules, the horizontal velocity increases with increasing distance to their centre up to a mean maximum velocity of 355 m s−1. For larger distances, the horizontal velocity decreases. We thus find that the velocity profile of naked sunspots resembles that of supergranular flows. The evolution of the flow field around individual sunspots is influenced by the way the sunspot decays and by the interplay with the surrounding flow areas. Conclusions. Observations of the flow around eight decaying sunspots suggest that as long as penumbrae are present, sunspots with their moat cell are embedded in network cells. The disappearance of the penumbra (and consequently the moat flow) and the competing surrounding supergranular cells, both have a significant role in the evolution of the flow field: The moat cell transforms into a supergranule, which hosts the remaining naked spot.

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