Calculation of Vibration Resistance of Chemical Reactor High-Speed Shaft Undergoing Torsional Vibrations. Part III. Calculation of Multi-Mass System Vibrations

2021 ◽  
pp. 780-786
Author(s):  
N. A. Merentsov ◽  
N. S. Sokolov-Dobrev ◽  
A. V. Persidskiy
Keyword(s):  
High Speed ◽  
Chemical Reactor ◽  
Torsional Vibrations ◽  
Mass System ◽  
Vibration Resistance

scholarly journals Estimation of leg stiffness using an approximation to the planar spring–mass system in high-speed running

2020 ◽  
Vol 17 (1) ◽  
pp. 172988141989071
Author(s):  
Wei Guo ◽  
Changrong Cai ◽  
Mantian Li ◽  
Fusheng Zha ◽  
Pengfei Wang ◽  
...  
Keyword(s):  
Analytical Solution ◽  
High Speed ◽  
Stance Phase ◽  
Center Of Mass ◽  
Critical Role ◽  
Line Center ◽  
Motion Model ◽  
Mass System ◽  
Leg Stiffness ◽  
Wide Range

Leg stiffness plays a critical role in legged robots’ speed regulation. However, the analytic solutions to the differential equations of the stance phase do not exist, of course not for the exact analytical solution of stiffness. In view of the challenge in dealing with every circumstance by numerical methods, which have been adopted to tabulate approximate answers, the “harmonic motion model” was used as approximation of the stance phase. However, the wide range leg sweep angles and small fluctuations of the “center of mass” in fast movement were overlooked. In this article, we raise a “triangle motion model” with uniform forward speed, symmetric movement, and straight-line center of mass trajectory. The characters are then shifted to a quadratic equation by Taylor expansion and obtain an approximate analytical solution. Both the numerical simulation and ADAMS-Matlab co-simulation of the control system show the accuracy of the triangle motion model method in predicting leg stiffness even in the ultra-high-speed case, and it is also adaptable to low-speed cases. The study illuminates the relationship between leg stiffness and speed, and the approximation model of the planar spring–mass system may serve as an analytical tool for leg stiffness estimation in high-speed locomotion.

Application of Experimental Modal Analysis Method in Researching of Mechanical Structure Dynamic Characteristics

2013 ◽  
Vol 694-697 ◽  
pp. 370-373
Author(s):  
Zhang Yu ◽  
Wen Zheng Cai
Keyword(s):  
Modal Analysis ◽  
Natural Frequency ◽  
Dynamic Characteristics ◽  
High Speed ◽  
Experimental Modal Analysis ◽  
Analysis Method ◽  
Mechanical Structure ◽  
Vibration Resistance ◽  
Structural Rigidity ◽  
Structure Dynamic

With the purpose of realizing the analysis of mechanical structure dynamic characteristics and inhibit vibration and noise, combined with the analysis of a certain type of high speed sewing machines vibration characteristics, we carry on the concrete experimental modal analysis, and compare the results of the experimental modal analysis with the results of spectrum analysis. The analysis results show that the second order natural frequency of the shell is close to two octaves under the normal working speed of sewing machine and it will lead to resonance. Enhancing the structural rigidity and the natural frequency under this modal to avoid resonance frequency is the key to improve vibration resistance of the structure.

Paper 4: Opening, Carding and Spinning Preparation Machines

1966 ◽  
Vol 181 (12) ◽  
pp. 1-7
Author(s):  
H. Catling
Keyword(s):  
High Speed ◽  
Unit Length ◽  
High Amplitude ◽  
Torsional Vibrations ◽  
Stick Slip ◽  
Periodic Disturbance ◽  
The Past ◽  
Machine Utilization ◽  
Lubrication Conditions ◽  
New Machine

There are no serious bearing problems in opening and carding machines. Except for the high-speed beaters and cylinders, occasionally-oiled plain journals were long regarded as adequate despite the fact that many of them operated under boundary lubrication conditions. Stable hydrodynamic film conditions were maintained in beater and cylinder bearings and some simple form of lubricant reservoir was usually provided. In recent years the introduction of shift working and high machine utilization factors have led to a demand for machines requiring a minimum of attention. This demand is being met by the use of prepacked, sealed ball or roller bearings at all points. Perhaps the most serious and intractable bearing problem in the whole field of textile machinery manufacture is encountered in drawframes and speedframes. For uniformity of the drawing action by which the fibres are straightened and finally attenuated to form a roving, it is necessary for all the drafting rollers to rotate perfectly smoothly. Unfortunately the loading conditions and the rotational speeds of some of the rollers are such that there is often a high liability to the occurrence of spontaneous stick–slip torsional vibrations. In other cases there is an incipient liability to stick–slip vibration and quite small gearing faults, of the appropriate frequency, are sufficient to precipitate high amplitude oscillations. At the frequencies commonly observed the non-uniformity of the drawing action introduces into the sliver or roving a periodic disturbance of a wavelength so short that it is not readily apparent in the delivery from the affected machine. Subsequent drafting, however, increases the wavelength and the ultimate yarn exhibits appreciable variations in mass per unit length and in twist distribution. As these variations are strictly periodic they form objectionable interference patterns when used as weft in either woven or knitted cloths. New machine designs and the use of new types of bearings have largely solved these problems and at the same time greatly increased operating speeds. The comber, too, has been intensively developed during the past ten years and a number of lubrication and wear problems have required attention.

Moving element analysis of discretely supported high-speed rail systems

2017 ◽  
Vol 232 (3) ◽  
pp. 783-797 ◽  
Author(s):  
Jian Dai ◽  
Kok Keng Ang ◽  
Minh Thi Tran ◽  
Van Hai Luong ◽  
Dongqi Jiang
Keyword(s):  
High Speed ◽  
Railway Track ◽  
High Speed Train ◽  
Element Analysis ◽  
High Speed Rail ◽  
Mass System ◽  
Rail System ◽  
Rail Systems ◽  
Track System ◽  
The Difference

In this paper, a computational scheme in conjunction with the moving element method has been proposed to investigate the dynamic response of a high-speed rail system in which the discrete sleepers on the subgrade support the railway track. The track foundation is modeled as a beam supported by uniformly spaced discrete spring-damper units. The high-speed train is modeled as a moving sprung-mass system that travels over the track. The effect of the stiffness of the discrete supports, train speed, and railhead roughness on the dynamic behavior of the train–track system has been investigated. As a comparison, the response of a continuously supported high-speed rail system that uses a foundation stiffness equivalent to that of a discretely supported track has been obtained. The difference in results between the “equivalent” continuously supported and the discretely supported high-speed rails has been compared and discussed. In general, the study found that a high-speed train that travels over a discretely supported track produces more severe vibrations than that travels over a continuously supported track of equivalent foundation stiffness.

Performance of Air-Lubricated Hydrodynamic Bearing Spindles for Laser Scanners

1991 ◽  
Vol 113 (3) ◽  
pp. 609-614 ◽  
Author(s):  
K. Tanaka ◽  
H. Muraki
Keyword(s):  
High Speed ◽  
High Performance ◽  
Experimental Results ◽  
Hydrodynamic Bearing ◽  
Vibration Resistance ◽  
High Speeds ◽  
Laser Printers ◽  
Laser Scanners

This paper reports on the performance of air-lubricated bearing spindles for high-speed laser scanners using newly developed bearings. Experimental results confirmed that these spindles have adequate performance including floating stability, endurance, vibration-resistance at high-speeds, and start-stop endurance for laser scanners. These spindles are already mass-produced and used in laser printers and digital color copiers, so their high performance and endurance are proven.

Torsional Vibrations of the Steam Turbine Shaft Line and Estimation of the Residual Life of Its Elements

2020 ◽  
Vol 63 (6) ◽  
pp. 91-98
Author(s):  
Vladimir Grabovskii ◽  
Keyword(s):  
Steam Turbine ◽  
High Speed ◽  
Residual Life ◽  
Operating Time ◽  
Electromagnetic Transients ◽  
Torsional Vibrations ◽  
Steam Turbines ◽  
Shaft Line ◽  
Operating Modes ◽  
Design Life

A comparative quantitative assessment of the damage and residual life of the shaft line elements for differ-ent types of high-power steam turbines at the end of their design life is made by mathematical modeling. The analysis covers all elements of the shaft line: from the steam turbine Central pump to the turbine generator ex-citer. The simulated circuit includes turbo generators, transformers, gate converters, AC and DC power lines. When modeling, an approach is used from the position of proper coordinates, which provides maximum meth-odological consistency of the models of the listed devices and allows you to directly reproduce electromagnetic and mechanical transients with the determination of instantaneous values of currents, voltages, electromagnet-ic and torsional moments. To estimate damage, we used the deformation criterion for soft and hard loads in the zone of low-cycle and force criterion in the zone of multi-cycle fatigue. The influence of the number of starts and running time of a steam turbine on the damage and residual life of its shaft elements is studied. When de-termining the remaining life, in addition to starts, other abnormal operating modes of the turbo generator were taken into account during the turbine operating time: short circuits and their disconnections, unsuccessful high-speed automatic re-activation, subsynchronous resonance due to both the operation of the control system of the PPT and the automatic generator excitation regulator. The influence of attenuation of electromagnetic transients in the generator and damping of torsional vibrations on the degree of reduction of the residual life of the shaft elements is analyzed. The results obtained can be used for a comprehensive solution of the issue of further operation of steam turbines that have spent their design life.

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