Assessment of Natural Oscillation Frequencies of Rotor for Development of Hard-Bearing Balancing Machine

2019 ◽  
pp. 249-257
Author(s):  
S. O. Gaponenko ◽  
A. E. Kondratiev ◽  
I. R. Tazeev
Keyword(s):  
Natural Oscillation ◽  
Oscillation Frequencies

scholarly journals Analysis of the natural frequencies of oscillations of a planar truss with an arbitrary number of panels

Vestnik MGSU ◽  
2019 ◽  
pp. 284-292
Author(s):  
Mikhail N. Kirsanov ◽  
Dmitriy V. Tinkov
Keyword(s):  
Analytical Solutions ◽  
Natural Frequencies ◽  
Average Frequency ◽  
Natural Oscillation ◽  
Frequency Function ◽  
Compliance Matrix ◽  
Frequency Spectra ◽  
Alternative Approach ◽  
Inertia Properties ◽  
Oscillation Frequencies

Introduction. Analytical solutions for problems of structural mechanics are not only an alternative approach to solving problems of strength, reliability and dynamics of structures, but also the possibility for simple performance evaluations and optimization of structures. Frequency analysis of planar trusses, most often used in construction and engineering, is an important part of the study of structures. Objectives - development of a three-parameter induction algorithm for deriving the analytical dependence of the natural oscillation frequencies of the truss on the number of panels. Materials and methods. A flat, statically definable truss with one additional external link and double braces has been considered. The inertia properties of the truss are modeled by point masses located in the nodes of the lower straight truss belt. Each mass is assumed to have only one vertical degree of freedom. The stiffness of all truss rods is assumed to be the same. The task is to obtain analytical dependences of the oscillation frequencies of the proposed truss model on the number of panels. The derivation of the desired formulas is performed by the method of induction in three stages - according to the numbers of rows and columns of the compliance matrix, calculated using the Maxwell - Mohr formula and the number of panels. To find common members of the obtained sequences of coefficients, an apparatus was used to compile and solve the recurrent equations of the Maple computer mathematics system. The task of determining frequencies has been reduced to the eigenvalue problem of a bisymmetric matrix. Results. For the elements of the compliance matrix, general formulas have been found, according to which the frequency equations are compiled and solved. It is shown that in the frequency spectra of trusses with different numbers of panels there is always one common frequency (middle frequency) located in the middle of the spectrum. An expression is found for the maximum value of the average oscillation frequency as a function of the height of the truss. Conclusions. The proposed truss scheme, despite its external static indeterminacy and the lattice, which does not allow for the calculation of forces by such methods as the method of cutting nodes and the cross section method, allows analytical solutions for the natural frequencies of loads in the nodes. The obtained formulas have a rather simple form, and some general properties, such as frequency coincidences for different numbers of panels and the presence of an analytically calculated maximum of the average frequency function of the truss height, make this solution convenient for practical structural evaluations.

scholarly journals AN ELECTROMAGNETIC METHOD FOR FREQUENCY ANALYSIS OF TRANSVERSE VIBRATIONS OF A BEAM

2020 ◽  
pp. 112-120
Author(s):  
F.Yu. Kuznetsov ◽  
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Frequency Analysis ◽  
Natural Oscillation ◽  
Theoretical Description ◽  
Natural Oscillations ◽  
Technical Procedure ◽  
Transverse Vibrations ◽  
Sample Testing ◽  
Oscillation Frequencies

Vibration-based diagnostics of constructions is an obligatory technical procedure in mechanical engineering. In this regard, there is a problem of an adequate theoretical description of vibration processes in various structures with account for end fixity conditions, as well as the creation of experimental facilities for non-contact testing. The paper presents a theoretical basis and experimental verification results for a method of electromagnetic frequency analysis of rod systems. The essence of the method is the experimental determination of natural oscillation frequencies and their comparison with reference values. The main attention is paid to a theoretical description of transverse vibrations of a cantilever conductive rod in an external magnetic field in order to determine reference frequencies of a defect-free sample. The presence of the external magnetic field gives rise to the distributed electromagnetic force exerted on the rod. In the case of natural oscillations, the magnetic force is damping, which leads to a change in damping factors of partial oscillations. The electromagnetic effect is selective towards vibrational modes; hence, the damping factors of various partial oscillations of the rod vary to different degrees. This fact allows one to determine an optimal location of the area with acting magnetic field, as well as its width when measuring a given frequency of sample testing. The proposed method has several advantages: indestructibility of the sample, non-contact measurements, invariability of mechanical properties of the sample during the tests.

scholarly journals Investigation of the Influence of a Cavity Type Defect on the Frequencies of the Natural Rail Oscillations by the Radar Method

2019 ◽  
pp. 1006-1012
Author(s):  
Vadim S. Potylitsyn ◽  
Danil S. Kudinov ◽  
Ekaterina A. Kokhonkova
Keyword(s):  
Doppler Radar ◽  
Natural Oscillation ◽  
Rolling Stock ◽  
Destructive Testing ◽  
Natural Oscillations ◽  
Type Defect ◽  
Radar Method ◽  
Impulse Load ◽  
Oscillation Frequencies ◽  
Non Destructive

Currently, the problem of non-destructive testing of rail lashes or rolling stock is quite acute, as the demands of both speed characteristics and vehicle safety increase every year. Thus, the purpose of this study was to determine the possibility of recording frequencies of natural oscillations by the radar method for rail lashes and the influence of the dimensions of the cavity-type defect. For this purpose, a laboratory bench was created with a standard rail, the length of 1.19 m of the P-65 brand, in which free oscillations were excited using a shock impulse load. Measurements of natural oscillation frequencies of the rail were recorded on a 24-bit ADC and a specialized accelerometer ZETLAB BC110. To register the oscillations, a Doppler radar with a frequency of 10 GHz was used, which was installed at the focus of a parabolic mirror offset antenna with a 1.6-meter diameter. It was found that a “field” defect shifts the frequency mode of oscillation 750 Hz upwards. It is shown that the hole in the rail neck with a diameter of 10 mm makes a change in the frequency of about 14 Hz

Evaluation of the Composite Barrier Natural Oscillations Influence on the Generated Shock Loading

2021 ◽  
pp. 103-113
Author(s):  
A.S. Borozenets ◽  
A.V. Proskurin ◽  
A.V. Shlishevskiy
Keyword(s):  
Test Object ◽  
Shock Loading ◽  
Natural Oscillation ◽  
Operating Conditions ◽  
Signal Spectrum ◽  
Natural Oscillations ◽  
Shock Loads ◽  
Frequency Determination ◽  
Prefabricated Structure ◽  
Oscillation Frequencies

The problem of studying behavior of various structures under the influence of intense impulsive (shock) loads arising during operation of many modern facilities, machines and devices remains relevant for many years. Shock loading in laboratory conditions is generated due to interaction between the test object and the braking device (barrier). In this case, braking device or barrier could be a one-piece or a prefabricated structure. If the braking device (barrier) dimensions commensurate with the test object, the braking device natural oscillation frequencies excited during interaction between the test object and the braking device (barrier) could be found in the range of the test object natural oscillation frequencies. Frequency determination within the signal spectrum registered on the test object and caused by oscillations of the braking device (barrier) or test equipment, would assist in better assessing the test object shock loading and its compliance with real operating conditions

scholarly journals Natural oscillation frequencies in the two lateral prefrontal cortices induced by Transcranial Magnetic Stimulation

NeuroImage ◽  
2021 ◽  
Vol 227 ◽  
pp. 117655
Author(s):  
Antonino Vallesi ◽  
Alessandra Del Felice ◽  
Mariagrazia Capizzi ◽  
Alessandra Tafuro ◽  
Emanuela Formaggio ◽  
...  
Keyword(s):  
Transcranial Magnetic Stimulation ◽  
Magnetic Stimulation ◽  
Natural Oscillation ◽  
Oscillation Frequencies ◽  
Prefrontal Cortices

scholarly journals INVESTIGATIONS OF VIBRO-OSCILLATORY PROVESSES OF THE SUPPORTS OF OFFSHORE STATIONARY PLATFORMS UNDER CONDITIONS OF ALTERNATING VORTEX FORMATION CAUSED BY THE INFLUENCE OF SEA CURRENTS

Akustika ◽  
2019 ◽  
Vol 32 ◽  
pp. 262-266
Author(s):  
Ivan Starokon ◽  
Y.M. Ovsannikov ◽  
A.O. Golovachev
Keyword(s):  
Frequency Spectrum ◽  
Characteristic Frequency ◽  
Natural Frequencies ◽  
Vortex Formation ◽  
Natural Oscillation ◽  
Hydrodynamic Forces ◽  
Offshore Platforms ◽  
Wide Range ◽  
Sea Currents ◽  
Oscillation Frequencies

Offshore platforms are exposed to hydrodynamic forces of a non-stationary nature and a wide range of frequencies. At present, hydrodynamic forces arising under conditions of alternating vortex formation have been poorly studied. These vortices are caused by the sea currents flowing around the supports of the platform, and due to their periodic occurrence and disruption, they lead to oscillations of the supports of the offshore platforms. Of particular danger are the cases of resonance of the characteristic frequency spectrum of hydrodynamic forces from the "occurrence-stalling" of vortices and natural frequencies of elements of the platform supports, which can cause fatigue damages in the platform supports. The article developed a method for determining the natural oscillation frequencies of marine supports and described the conditions under which the occurrence of alternating vortex formation is possible.

scholarly journals Study on Short-Circuiting GMAW Pool Behavior and Microstructure of the Weld with Different Waveform Control Methods

Metals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1326 ◽  
Author(s):  
Tao Chen ◽  
Songbai Xue ◽  
Bo Wang ◽  
Peizhuo Zhai ◽  
Weimin Long
Keyword(s):  
Weld Pool ◽  
Liquid Bridge ◽  
High Speed ◽  
Gas Metal Arc Welding ◽  
Oscillation Mode ◽  
Natural Oscillation ◽  
Control Methods ◽  
Waveform Control ◽  
Weld Pools ◽  
Oscillation Frequencies

In order to study internal relation among the behavior of the weld pool, the microstructure of weld bead and the waveform of short-circuiting gas metal arc welding (S-GMAW), a high speed photograph-images analysis system was formed to extract characteristics of weld pool behavior. Three representative waveform control methods were used to provide partly and fully penetrated weld pools and beads. It was found that the behavior of the weld pool was related to the instantaneous power density of the liquid bridge at the break-up time. Weld pool oscillation was triggered by the explosion of the liquid bridge, the natural oscillation frequencies were derived by the continuous wavelet transform. The change of weld pool state caused the transition of oscillation mode, and it led to different nature oscillation frequencies between partial and full penetration. Slags flow pattern could be an indication of the weld pool flow. Compared with the scattered slags on fully penetrated weld pool, slag particles accumulated on partially penetrated weld pools. The oscillating promoted the convection of the welding pool and resulted in larger melting width and depth, the grain size, and the content of pro-eutectoid ferrite in the weld microstructure of S235JR increased, the content of acicular ferrite decreased.

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