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.

scholarly journals Loads of road vehicles during piggyback transportation

2019 ◽  
Vol 298 ◽  
pp. 00109 ◽  
Author(s):  
Aleksandr Tsyganov
Keyword(s):  
Technical Condition ◽  
Dynamic Loads ◽  
Rolling Stock ◽  
Rail Transportation ◽  
Structural Elements ◽  
Road Vehicles ◽  
Dynamic Forces ◽  
The Impact ◽  
Railway Rolling Stock

The impact of rail transportation on road vehicles that are placed in flatcars is considered in the article. The features of piggyback transportation and the dynamic forces acting on road vehicles in railway rolling stock are determined. The change dependences of the values of dynamic forces for different masses of road vehicles in the longitudinal and transverse directions are established. It is concluded that road vehicles that are used in regular piggyback transportation will experience significant dynamic loads of structural elements, which requires monitoring of their technical condition. Consequently, the infrastructure of piggyback terminals that load and unload road vehicles onto railway rolling stock should include the availability of automobile service facilities.

Study of the dynamics of ТПА 350 automatic mill working stand elements

2020 ◽  
Vol 76 (8) ◽  
pp. 830-840
Author(s):  
S. R. Rakhmanov ◽  
V. V. Povorotnii
Keyword(s):  
Mechanical System ◽  
Dynamic Model ◽  
Maximum Amplitude ◽  
Calculation Scheme ◽  
Dynamic Loads ◽  
Forced Oscillations ◽  
Mass Model ◽  
Automatic Mill ◽  
Hollow Billet ◽  
Oscillation Movement

To form a necessary geometry of a hollow billet to be rolled at a pipe rolling line, stable dynamics of the base equipment of the automatic mill working stand has a practical meaning. Among the forces, acting on its parts and elements, significant by value short-time dynamic loads are the least studied phenomena. These dynamic loads arise during transient interaction of the hollow billet, rollers, mandrel and other mill parts at the forced grip of the hollow billet. Basing of the calculation scheme and dynamic model of the mechanical system of the ТПА 350 automatic mill working stand was accomplished. A mathematical model of dynamics of the system “hollow billet (pipe) – working stand” within accepted calculation scheme and dynamic model of the mechanical system elaborated. Influence of technological load of the rolled hollow billet variation in time was accounted, as well as variation of the mechanical system mass, and rigidity of the ТПА 350 automatic mill working stand. Differential equations of oscillation movement for four-mass model of forked sub-systems of the automatic mill working stand were made up, results of their digital calculation quoted. Dynamic displacement of the stand elements in the inter-roller gap obtained, which enabled to estimate the results of amplitude and frequency characteristics of the branches of the mill rollers setting. It was defined by calculation, that the maximum amplitude of the forced oscillations of elements of the ТПА 350 automatic mill working stand within the inter-roller gap does not exceed 2 mm. It is much higher than the accepted value of adjusting parameters of the deformation center of the ТПА 350 automatic mill. A scheme of comprehensive modernization of the rollers setting in the ТПА 350 automatic mill working stand was proposed. It was shown, that increase of rigidity of rollers setting in the ТПА 350 automatic mill working stand enables to stabilize the amplitude of forced oscillations of the working stand elements within the inter-rollers gap and considerably decrease the induced nonuniform hollow billet wall thickness and increase quality of the rolled pipes at ТПА 350.

scholarly journals Structural vehicle impact loading

2013 ◽  
Vol 11 (3) ◽  
pp. 285-292
Author(s):  
Dragoslav Stojic ◽  
Stefan Conic
Keyword(s):  
Impact Analysis ◽  
Impact Loads ◽  
Structural Elements ◽  
Structural Element ◽  
Static Loads ◽  
Equivalent Static Loads ◽  
Vehicle Impact ◽  
Dynamic Forces ◽  
Force Intensity

In contemporary design, vehicle impact into the structures is paid great attention since they can be dominant, depending on the type of structure. The key issue in the vehicle impact analysis is the proper determination of intensity and way of action of dynamic forces on the structural element and its behavior after the imparted load. The Eurocodes, in the annexes provide recommendations for determination of force intensity depending on mass and velocity of the colliding vehicle. Equivalent static loads causing approximate effects on the structural elements are used as quite approximate and efficient methods. The paper comprises the analysis of deformation of columns having the same characteristics, exposed to impact loads via the equivalent static loads, depending on the stress state in columns, and a comparative analysis has been done.

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 Control system for electrohydraulic drive of a mobile sinking hoisting plant

2018 ◽  
Vol 224 ◽  
pp. 02009
Author(s):  
Anton Kurochkin ◽  
Vladimir Vagin ◽  
Anton Karpesh ◽  
Natalja Dyorina
Keyword(s):  
Control System ◽  
System Development ◽  
Hydraulic Drive ◽  
Dynamic Loads ◽  
Effective Control ◽  
Damping Properties ◽  
Technical Performance ◽  
Dynamic Forces ◽  
Electrohydraulic Drive ◽  
Increase In Productivity

The article presents the results of the control system development for the electro hydraulic drive of a mobile sinking hoisting plant. Increasing the technical performance of mobile sinking hoisting plants is possible by increasing their productivity, reducing their massiveness and increasing the durability of tractional organs and a number of units and parts of lifting machines. However, the increase in productivity, in its turn, causes the need to increase the suspended load on the traction organs, which causes a significant increase of the dynamic loads in the elastic elements in the transient operation modes of the hoisting plant. One of the ways to reduce constantly acting dynamic loads of vibration character is the use of a gearless hydraulic drive with damping properties. But, nevertheless, the hydraulic drive possibilities are limited for large vibration amplitudes of dynamic forces. The damping properties of the hydraulic drive can be increased by using control system, which allows realizing effective control of the electro hydraulic drive of the hoisting plant.

Analysis and Comparison of Safety of Children and Adult Passenger in Car Based on Crash Tests Results

2013 ◽  
Vol 597 ◽  
pp. 199-205
Author(s):  
Bartosz Zdunek ◽  
Michał Landowski ◽  
Stanislaw Taryma ◽  
Ryszard Woźniak ◽  
Krystyna Imielińska ◽  
...  
Keyword(s):  
Dynamic Test ◽  
Occipital Bone ◽  
The Other ◽  
Dynamic Loads ◽  
Impact System ◽  
Dynamic Forces ◽  
Good Energy ◽  
Energy Absorbing ◽  
Crash Tests

Most important features of the child seat were presented. There was made analysis of selected dynamic loads acting on mannequins heads during a collision. Comparison of loads acting on the kid in a child seat and the other passengers in a car is presented. In analysis of the results particular attention has been paid on the children's secure in a car. The phenomena of collision child's occipital bone with seat backrest was described. There were presented results of dynamic test of chosen kind of materials, which were expected for having good energy absorbing characteristic. Selected courses of dynamic forces, values of peak forces and time of dynamic forces acting for tested materials were shown. The tests were made on dynamic droptower impact system Instron CEAST 9310.

scholarly journals Discrete model of chain conveyor movement dynamics

2020 ◽  
Vol 11 (4) ◽  
pp. 89-94
Author(s):  
M. M. Korobko ◽  
Keyword(s):  
Metal Content ◽  
Degrees Of Freedom ◽  
Dynamic Loads ◽  
Transport Mechanisms ◽  
Movement Dynamics ◽  
Start Up ◽  
Dynamic Forces ◽  
Steady Rotation ◽  
Chain Conveyor ◽  
Basic Movement

Improving the reliability of structures of transport mechanisms and other elements, reducing metal content, improving performance, expanding functionality and technical capabilities is a priority area of work to improve existing and develop new machines for beet growing. The dynamic model of the chain conveyor which considers the basic movement and fluctuations of elements of the drive and a working cloth is developed in work. The model is represented by a system of discrete masses with eight degrees of freedom. The operation of chain conveyors is characterized by the presence of dynamic forces arising from the pulsating movement of the chain at a steady rotation of the drive sprocket. At the start-up site, dynamic forces from increasing the speed from zero to a certain constant value are added to these forces. Under such conditions, significant alternating dynamic loads can occur in the chain, which as a result of the accumulation of fatigue phenomena can lead to its premature destruction.

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