Rotary actuator control based on tensile force elements made of shape memory Cu-Al-Ni crystals when operated in a cyclic modeA.I. Priadko, S.A. Pulnev, O.O. Kovalev & I.A. Ilin
An actuator design and a function scheme are developed. A control algorithm of a cyclic actuator is considered. We provide experimental results on the control algorithm and the actuator. The actuator operating range is 60°. The actuator sped is ~ 1 degree/second. The actuator operating is stable in any rotation angle in operating range.
This paper considers positioning algorithms for rotary actuators based on shape memory Cu-Al-Ni crystals. The actuator function scheme is provided. An algorithm for positioning of the actuator based on an actual rotary angle has been developed. Experimental results on the control algorithm and the actuator are presented. The functional characteristics of the actuator (rotation speed and positioning accuracy) are considered.
Mechanical wear resistance of the α- and β- Ga2O3 polymorphs is experimentally studied. We report about tribological cyclic tests of these wide-band-gap semiconductor crystals. To the best of our knowledge, this is the first attempt at considering these crystals as protective coatings. The crystalline layers were deposited on sapphire substrates by vapour-phase epitaxy. This method allows applying coatings on large areas and surfaces of complex shapes, including the surfaces of a number of metals. It...
The characteristics of terahertz (THz) irradiation generated by a silicon nanosandwich structure under the conditions of a stabilized drain-source current are demonstrated. The frequency of irradiation arising from the quantum Faraday effect is determined by the parameters of microcavities embedded in the edge channels of a silicon nanosandwich structure confined by the negative-U centers. The obtained characteristics of a compact THz irradiation source determine the basis for highly effective medical applications.
Burst-like shape memory recovery and calorimetric effect in Cu-Al-Ni alloy single crystals at cyclic testL.I. Guzilova, V.I. Nikolaev, P.N. Yakushev, S.I. Stepanov, R.B. Timashov, A.V. Chikiryaka & S.A. Pulnev
Here we report on compressive stress-strain behavior, ordinary and burst-like shape memory (SM) strain recovery, and associated caloric effects in Cu – 14.02% wt. Al – 4.0% wt. Ni single crystals which have multiphase martensitic structure at room temperature. The effect of repetitive thermo-mechanical cycling on the recovery of the shape memory deformation is investigated. The stress-strain curves of the specimens are smooth in all tests. Immediately after quenching, crystals exhibited burst-like strain recovery accompanied...
Self-organization mechanisms promoting elimination of cracks in thick GaN layers grown on sapphire substrates are considered on the basis of the experimental results on the fabrication of the layers by Hydride Vapor-Phase Epitaxy on MOCVD-grown GaN/Al2O3 templates. The obtained data support the supposition on the closure of tensile stress-related cracks via diffusion processes and demonstrate the strong contribution of bulk diffusion in addition to surface diffusion discussed earlier.
It is shown that a single-walled carbon nanotube based on a carbon monolayer (graphene) rolled up into a cylinder is a nanoscale quantum system characterized by the presence of electron crystals, like graphene. In contrast to the extremely unstable graphene quantum system, the nanotube quantum system is stable at a certain curvature of the carbon skeleton. The curvature causes the redistribution of π electrons between internal and external electron crystals accompanied by the formation of...
Изучена возможность снижения плазменной частоты благодаря химическим процессам в газе. Химические процессы запускаются с помощью инжектирования веществ, которые через химические процессы снижают уровень концентрации заряженной компоненты. Предложены вещества и проведены расчеты, показывающие необходимые концентрации этих веществ для появления эффекта.
Gallium oxide films were grown by HVPE on (0001) sapphire substrates with and without α-Cr2O3 buffer produced by RF magnetron sputtering. Deposition on bare sapphire substrates resulted in a mixture of α-Ga2O3 and ε-Ga2O3 phases with a dislocation density of about 2∙1010 cm-2. The insertion of α-Cr2O3 buffer layers resulted in phase-pure α-Ga2O3 films and a fourfold reduction of the dislocation density to 5∙109 cm-2.
Results of structural characterization of (AlxGa1-x)2O3 single crystals grown from the melt with Al content x up to 0.04 are presented. Bulk (AlxGa1-x)2O3 crystals were grown by exploring the Czochralski method . Transmission electron microscopy (TEM) was used to investigate defect structure of the material with various composition, X-ray diffractometry was used to measure Al content x, to inspect crystallography of the growth facets and to characterize the structure quality of the samples. Possible types...
Axial misfit stress relaxation in core-shell nanowires with hexagonal core via nucleation of rectangular prismatic dislocation loopsS.A. Krasnitckii, A.M. Smirnov, K.D. Mynbaev, L.V. Zhigilei & M.Yu. Gutkin
A theoretical model of axial misfit stress relaxation in core-shell nanowires with hexagonal cross section of the core through the nucleation of prismatic dislocation loops is suggested. Different nucleation sites of the loops in core-shell nanowires are considered. The energy change caused by the loop nucleation is calculated. The critical condition for the onset of the loops is given and analyzed in detail. The most favorable sites in nanowires and the optimal loop shape are...
We propose a technuque of liquid-phase growth of (AlxGa1-x)2O3 crystals with variable and controlled Al content in them. When using the Czochralski growth process Ga2O3 melt was dosed by sapphire seed. By applying of the special growth zone and the regulating the process parameters, a series of crystal samples with Al content varying from 0.51 to 4.68 % at. was obtained. In addition to the standard setting of the geometry and weight of the crystals...
Quantum effects occurring during current filamentation in a chalcogenide glass are considered. Under the conditions considered, the current filament appears as a set of concentric tubes with different temperatures. In every tube, the electron has a specific wave function and a specific energy level. The radii of the tubes appear to be proportional to natural numbers n. The dependence of maximal temperature on the electrical field is obtained. The Schroedinger equation is reduced to the...
Shape memory Cu-Al-Ni single crystals of two alloy compositions Cu 82.5 wt.% - Al 13.5 wt.% - Ni 4.0 wt.% and Cu 81.98 wt.% - Al 14.02 wt.% - Ni 4.0 wt.% have been studied in view of their ability to undergo spontaneous jumping during reverse martensitic transformation. Crystals of both alloys were compressively deformed up to a full shape memory strain (8%) at room temperature. It was found that specimens of the first alloy...
Теоретически исследуется возможность электромагнитного излучения ударной волны в столкновительной плазме, излучения, которое стимулировано именно движением самой ударной волны. Излучение происходит поперек движению ударной волны и для экспериментов в холодной плазме — на частоте высокочастотного излучения.
Peter the Great St. Petersburg Polytechnic University6
Institute of Problems of Mechanical Engineering2
Tomsk Polytechnic University1
University of Virginia1
National University of Science and Technology1
Federal Almazov North-West Medical Research Centre1
The Turner Scientific Research Institute for Children's Orthopedics1