scholarly journals Influence of hinged device parameters on negative resonance oscillations during the operation of machine-tractor unit in transport mode

2020 ◽  
pp. 129-136
Author(s):  
V. M. Тretyak ◽  
V. V. Sheban ◽  
R. V. Oliadnichuk ◽  
O. F. Govorov ◽  
R. V. Melnik
Keyword(s):  
Oscillation Theory ◽  
Forced Oscillations ◽  
Structural Elements ◽  
Supporting Surface ◽  
Analytical Geometry ◽  
Transport Mode ◽  
Resonance Phenomena ◽  
Instantaneous Center ◽  
Strain Gauge Measurements ◽  
Kinematic Diagram

Annotation Purpose. Reducing the influence of resonance phenomena on the structural elements of a tractor of the KIY 14102 type when driving with an attached implement in transport mode. Methods. To solve this problem means of graph-analytical constructions, analytical geometry, oscillation theory and theoretical mechanics were used. Results. On the basis of the graphic-analytical analysis of the kinematic diagram of the tractor attachment of the KIY 14102 type, it was found that the position of the instantaneous center of its rotation significantly depends on the change in the angle between the tractor frame and the levers, which are united by the CA-1 automatic connection device. The frequency range of forced oscillations of the tractor frame, which occur when driving in a certain speed range, can coincide with the relative natural frequency of the tractors, which leads to resonance phenomena. Resonant longitudinal-angular vibrations of the tractor frame reduce the normal reactions of the steered wheels with the supporting surface, which worsens controllability. Changing the frequency of the natural resonance of the elements connecting the tractor with the implement can be done by changing the kinematic stiffness of the mounted system. Conclusions 1. The kinematic diagram of the hinged device of tractors significantly affects the dependence of the position of the instantaneous center of rotation of the hinged device relative to the mass of the implement that is aggregated. 2. The existing parameters of the mounted systems of tractors of the KIY 14102 type can lead to the occurrence of resonance phenomena when driving in transport mode on unpaved field roads, which negatively affects the controllability of the MTA. 3. Reducing the resonant frequency of natural vibrations of the attachment system with the tool, by reducing the kinematic stiffness, improves the dynamics of the interaction of the elements of the machine-tractor unit with each other and with the supporting surface. Keywords: machine-tractor unit, clutch system, tests, dynamic loads, strain gauge measurements, air pressure in tires.

scholarly journals North-south asymmetry of ultra-low-frequency oscillations of Earth’s electromagnetic field

2017 ◽  
Vol 3 (4) ◽  
pp. 26-31 ◽  
Author(s):  
Анатолий Гульельми ◽  
Anatol Guglielmi ◽  
Борис Клайн ◽  
Boris Klain ◽  
Александр Потапов ◽  
...  
Keyword(s):  
Nonlinear Dynamical System ◽  
Low Frequency ◽  
Auroral Oval ◽  
Forced Oscillations ◽  
Structural Elements ◽  
Nonlinear Dynamical ◽  
Ultralow Frequency ◽  
Low Frequency Oscillations ◽  
Electromagnetic Oscillations ◽  
South Asymmetry

In the paper, we present the result of an experimental study of north-south asymmetry of ultralow-frequency electromagnetic oscillations IPCL. This study is based on observations made at Mirny Observatory (Antarctica). IPCLs are excited in the dayside sector of the auroral oval in the range 3–10 min periods and represent one of the most powerful types of oscillations of Earth's magnetosphere. These oscillations were discovered in the 1970s during IPhE AS USSR polar expeditions organized by Prof. V.A. Troitskaya. We have shown that IPCL activity in Mirny depends on the inclination (north-south asymmetry) of interplanetary magnetic field (IMF) lines to the plane of the geomagnetic equator before the front of the magnetosphere. The result suggests a controlling exposure of IMF on the magnetospheric oscillations and gives rise to the hypothesis that IPCL are forced oscillations of a nonlinear dynamical system whose major structural elements are dayside polar cusps. The paper is dedicated to the memory of Professor V.A. Troitskaya (1917–2010).

scholarly journals OPTIONS FOR PLANE-PARALLEL MOVEMENT OF GRAINS IN A SCRAPER CONVEYOR

2020 ◽  
Vol 14 (4) ◽  
pp. 96-99
Author(s):  
Sergey Yakhin ◽  
Il'gam Masalimov ◽  
Marat Nafikov ◽  
Ramis Mardanov
Keyword(s):  
Complex Motion ◽  
Sliding Speed ◽  
Friction Forces ◽  
Plane Parallel ◽  
Parallel Movement ◽  
Parallel Motion ◽  
Touch Point ◽  
Scraper Conveyor ◽  
Instantaneous Center ◽  
Kinematic Diagram

The kinematics of plane-parallel motion of a wheat or rye grain when moving in an inclined position in a scraper conveyor is considered. A kinematic diagram of the plane-parallel motion of the grain in the scraper conveyor was compiled, the position of the instantaneous center of the flat figure was determined, and options for the movement of grain in an inclined position at various possible positions of instantaneous center were considered. The profile of the grains is outlined by an elliptical curve. The point of contact of the elliptical profile of the caryopsis with the scraper makes a complex motion, while the horizontal speed of the scraper is portable for it, the sliding speed on the surface of the scraper is relative. The speed of the touch point of the grain with the pan is horizontal. For six possible positions of the instantaneous center, the directions of the velocities of the points of contact of the grains and the friction forces acting in them are determined. Grains of wheat or rye, moved in a scraper conveyor, in some cases can make plane-parallel movement. The point of contact of the elliptical profile of the caryopsis with the scraper makes a complex motion, while the horizontal speed of the scraper is portable for it, the sliding speed on the surface of the scraper is relative. The speed of the touch point 2 of the grain with the pan is horizontal.

Forced Oscillations of a Continuous Rotor With Geometric Nonlinearity: Internal Resonance Phenomena at Harmonic and Subharmonic Resonances

1997 ◽  
Author(s):  
Yukio Ishida ◽  
Imao Nagasaka ◽  
Seongwoo Lee
Keyword(s):  
Geometric Nonlinearity ◽  
Internal Resonance ◽  
Forced Oscillations ◽  
Center Line ◽  
Rotating Shaft ◽  
Restoring Force ◽  
Resonance Phenomena ◽  
Geometric Stiffening ◽  
Resonance Curves ◽  
Subharmonic Resonances

Abstract Harmonic resonances and subharmonic resonances of order 1/2 and order 1/3 in a continuous rotating shaft with distributed mass are discussed. The restoring force of the shaft has geometric stiffening nonlinearity due to the extension of the shaft center line. It is supposed that a distributed bias force, such as the gravity, works. The possibility of their occurrences, the shapes of resonance curves, and internal resonance phenomena are investigated.

Local Strain Distribution Produced by Warping: The Case of a Tail Rotor Blade of a Helicopter

2004 ◽  
Vol 1-2 ◽  
pp. 261-0
Author(s):  
Mario Chiarelli
Keyword(s):  
Rotor Blade ◽  
Elementary Theory ◽  
Experimental Studies ◽  
Local Strain ◽  
Variable Stiffness ◽  
Local Geometry ◽  
Loading Conditions ◽  
Structural Elements ◽  
Research Activity ◽  
Strain Gauge Measurements

Aircraft engineers in the design phase often use practical solutions and results of the elementary theory of structures under the classical hypotheses assumed for shear, torsion and bending behaviour of structural elements that can be studied as "beams". This assumption, very powerful in general, under particular situations (for example: the modification of loading conditions in the development of new aircraft versions) can be inadequate to represent real distributions of stress and strain. This is particularly true when local behaviour of structures depends on secondary phenomena such as warping produced by non-uniform bending and torsion acting on structural elements with variable stiffness along their flexural axis. In this paper the results of analytical and experimental studies carried out for a metallic tail rotor blade of a helicopter are summarised; this research activity was born during a collaboration between the Department of Aerospace Engineering of Pisa and an aeronautical industry. Local strain distributions under real loading conditions have been obtained by means of finite element analyses and by means of strain gauge measurements. To describe warping mechanisms accurately, also caused by the presence of a reinforcing plate of the blade structure, sub-modelling technique has been used and during a fatigue test, the blade was instrumented with an appropriate number of rosettes. Numerical and experimental results show, with a good agreement, that local geometry of the blade and the severe loading condition produce a considerable increase of strains that elementary theory can not predict; moreover, numerical results and above all strain measurements have proved that local yielding of the material can occur during the service life with detrimental effects on the fatigue endurance of the tail rotor blade.

scholarly journals North-south asymmetry of ultra-low-frequency oscillations of Earth’s electromagnetic field

2017 ◽  
Vol 3 (4) ◽  
pp. 27-33
Author(s):  
Анатолий Гульельми ◽  
Anatol Guglielmi ◽  
Борис Клайн ◽  
Boris Klain ◽  
Александр Потапов ◽  
...  
Keyword(s):  
Nonlinear Dynamical System ◽  
Low Frequency ◽  
Auroral Oval ◽  
Forced Oscillations ◽  
Structural Elements ◽  
Geomagnetic Equator ◽  
Nonlinear Dynamical ◽  
Low Frequency Oscillations ◽  
Electromagnetic Oscillations ◽  
South Asymmetry

In the paper, we present the result of an experimental study of north-south asymmetry of ultra-low-frequency electromagnetic oscillations IPCL. This study is based on observations made at obs. Mirny (Antarctica). IPCL are excited in the dayside sector of the auroral oval in the range of 3–10 min periods and represent one of the most powerful types of oscillations of Earth’s magnetosphere. These oscillations were discovered in the 1970s during IPhE AS USSR polar expeditions organized by Prof. V.A. Troitskaya. We have shown that IPCL activity in Mirny depends on the inclination (north-south asymmetry) of interplanetary magnetic field (IMF) lines to the plane of the geomagnetic equator before the front of the magnetosphere. The result suggests a controlling exposure of IMF on the magnetospheric oscillations and gives rise to the hypothesis that IPCL are forced oscillations of a nonlinear dynamical system whose major structural elements are dayside polar cusps. The paper is dedicated to the memory of Professor V.A. Troitskaya (1917–2010).

scholarly journals A Study of the Occurrence of Resonance under the Influence of Dynamic Forces on the Structural Elements of Electrical Installations

2021 ◽  
Vol 64 (3) ◽  
pp. 228-238
Author(s):  
Ya. V. Potachits
Keyword(s):  
Short Circuit ◽  
Dynamic Loads ◽  
Forced Oscillations ◽  
Structural Elements ◽  
Destructive Effect ◽  
Reliable Determination ◽  
Dynamic Task ◽  
Electrical Devices ◽  
Dynamic Forces ◽  
The Republic

The increase in the levels of short-circuit currents in the power system of the Republic of Belarus requires the study of the parameters of the electrodynamic stability of the main structural elements of electrical installations with flexible conductors. In case of a short circuit in the network, currents tenfold exceeding the rated one hundreds of times can flow through the current-carrying part of the device. When the magnetic fields formed by these currents interact, significant electromagnetic forces arise, which have a destructive effect both on the current-carrying parts themselves and on the structural elements of electrical installations, viz. support insulators, switching devices, measuring equipment. The movement of the wires in a short-circuit mode leads to the appearance of significant dynamic loads in them, which, in turn, are transmitted to the portals, support insulators and electrical devices. A topical problem is the occurrence of unacceptable mechanical forces in the main structural elements that can cause their destruction. Thus, the analysis of the physical and mechanical parameters and geometric dimensions of the flexible busbar of switchgear shows that a violation of the condition of electrodynamic resistance to tension is unlikely due to the high mechanical strength of the large-section steel-aluminum wires used. At the same time, span-limiting portals, support insulators and other electrical devices have significantly lower permissible bending loads. When exposed to dynamic forces, the conductors bend and transfer the load to the structural elements which have certain elasticity. Thus, a reliable determination of dynamic loads, taking into account the current-carrying parts acting on the supporting structures, is possible only if a dynamic task is set. The article describes the methods of mathematical modeling and computational experiment for analyzing the parameters of the electro-dynamic stability of the main structural elements which are determined using coefficients that depend on the natural frequencies of oscillations and the nature of changes in dynamic forces over time. To solve these problems, mathematical models are compiled and boundary value problems are formulated for calculating the electrodynamic stability of structural elements, taking into account the possible coincidence of the frequencies of natural and forced oscillations of structural elements taking into account the probable coincidence of the frequencies of forced and natural vibrations of structural elements.

Structural phenomena in the growth of carbon nanotubes

1993 ◽  
Vol 51 ◽  
pp. 750-751
Author(s):  
Jun Jiao
Keyword(s):  
Carbon Nanotubes ◽  
Growth Mechanism ◽  
Carbonaceous Material ◽  
Cluster Growth ◽  
Structural Elements ◽  
Rich Variety ◽  
Different Shapes ◽  
Point To Point

HREM studies of the carbonaceous material deposited on the cathode of a Huffman-Krätschmer arc reactor have shown a rich variety of multiple-walled nano-clusters of different shapes and forms. The preparation of the samples, as well as the variety of cluster shapes, including triangular, rhombohedral and pentagonal projections, are described elsewhere.The close registry imposed on the nanotubes, focuses attention on the cluster growth mechanism. The strict parallelism in the graphitic separation of the tube walls is maintained through changes of form and size, often leading to 180° turns, and accommodating neighboring clusters and defects. Iijima et. al. have proposed a growth scheme in terms of pentagonal and heptagonal defects and their combinations in a hexagonal graphitic matrix, the first bending the surface inward, and the second outward. We report here HREM observations that support Iijima’s suggestions, and add some new features that refine the interpretation of the growth mechanism. The structural elements of our observations are briefly summarized in the following four micrographs, taken in a Hitachi H-8100 TEM operating at an accelerating voltage of 200 kV and with a point-to-point resolution of 0.20 nm.

Designing TIMP (tissue inhibitor of metalloproteinases) variants that are selective metalloproteinase inhibitors

2003 ◽  
Vol 70 ◽  
pp. 201-212 ◽  
Author(s):  
Hideaki Nagase ◽  
Keith Brew
Keyword(s):  
Three Dimensional ◽  
Therapeutic Interventions ◽  
Tissue Inhibitors Of Metalloproteinases ◽  
Structural Basis ◽  
Structural Elements ◽  
Ridge Structure ◽  
Extracellular Matrix Components ◽  
Metalloproteinase Inhibitors ◽  
The Matrix ◽  
A Disintegrin And Metalloproteinase

The tissue inhibitors of metalloproteinases (TIMPs) are endogenous inhibitors of the matrix metalloproteinases (MMPs), enzymes that play central roles in the degradation of extracellular matrix components. The balance between MMPs and TIMPs is important in the maintenance of tissues, and its disruption affects tissue homoeostasis. Four related TIMPs (TIMP-1 to TIMP-4) can each form a complex with MMPs in a 1:1 stoichiometry with high affinity, but their inhibitory activities towards different MMPs are not particularly selective. The three-dimensional structures of TIMP-MMP complexes reveal that TIMPs have an extended ridge structure that slots into the active site of MMPs. Mutation of three separate residues in the ridge, at positions 2, 4 and 68 in the amino acid sequence of the N-terminal inhibitory domain of TIMP-1 (N-TIMP-1), separately and in combination has produced N-TIMP-1 variants with higher binding affinity and specificity for individual MMPs. TIMP-3 is unique in that it inhibits not only MMPs, but also several ADAM (a disintegrin and metalloproteinase) and ADAMTS (ADAM with thrombospondin motifs) metalloproteinases. Inhibition of the latter groups of metalloproteinases, as exemplified with ADAMTS-4 (aggrecanase 1), requires additional structural elements in TIMP-3 that have not yet been identified. Knowledge of the structural basis of the inhibitory action of TIMPs will facilitate the design of selective TIMP variants for investigating the biological roles of specific MMPs and for developing therapeutic interventions for MMP-associated diseases.

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