Effects of location and aspect ratio of a flexible disk on natural frequencies and critical speeds of a rotating shaft-disk system

2019 ◽  
Vol 152 ◽  
pp. 596-612 ◽  
Author(s):  
Hassan Heydari ◽  
Amir Khorram
Keyword(s):  
Aspect Ratio ◽  
Natural Frequencies ◽  
Rotating Shaft ◽  
Disk System ◽  
Critical Speeds ◽  
Flexible Disk

The Natural Frequencies and Critical Speeds of a Rotating, Flexible Shaft-Disk System

1975 ◽  
Vol 97 (3) ◽  
pp. 881-886 ◽  
Author(s):  
D. R. Chivens ◽  
H. D. Nelson
Keyword(s):  
Natural Frequencies ◽  
Numerical Solutions ◽  
Geometric Model ◽  
Analytical Investigation ◽  
Rotating Shaft ◽  
Disk System ◽  
Critical Speeds ◽  
Transverse Bending ◽  
Wide Range ◽  
Dimensional Parameters

An analytical investigation into the influence of disk flexibility on the transverse bending natural frequencies and critical speeds of a rotating shaft-disk system is presented. The geometric model considered consists of a flexible continuous shaft carrying a flexible continuous circular plate. The partial differential equations governing the system motion and the associated exact solution form are developed. Numerical solutions are presented covering a wide range of non-dimensional parameters and general conclusions are drawn.

Additional Investigations Into the Natural Frequencies and Critical Speeds of a Rotating, Flexible Shaft-Disk System

2007 ◽  
Author(s):  
Lyn M. Greenhill ◽  
Valerie J. Lease
Keyword(s):  
Natural Frequencies ◽  
Slenderness Ratio ◽  
Rotor Dynamics ◽  
Axial Position ◽  
Disk System ◽  
Apparent Contradiction ◽  
Critical Speeds ◽  
Shaft Flexibility ◽  
Gyroscopic Effects ◽  
Lumped Masses

Traditional rotor dynamics analysis programs make the assumption that disk components are rigid and can be treated as lumped masses. Several researchers have studied this assumption with specific analytical treatments designed to simulate disk flexibility. The general conclusions reached by these studies indicated disk flexibility has little effect on critical speeds but significantly influences natural frequencies. This apparent contradiction has been reexamined by using axisymmetric harmonic finite elements to directly represent both disk and shaft flexibility along with gyroscopic effects. Results from this improved analysis show that depending on the thickness-to-diameter (slenderness) ratio of the disk and the axial position of the disk on the shaft, there are significant differences in all natural frequencies, for both forward and backward modes, including synchronous crossings at critical speeds.

TUNING OF SIMULATED NATURAL FREQUENCIES FOR A FLEXIBLE SHAFT–MULTIPLE FLEXIBLE DISK SYSTEM

1997 ◽  
Vol 207 (4) ◽  
pp. 435-451 ◽  
Author(s):  
C.-W. Lee ◽  
H.S. Jia ◽  
C.-S. Kim ◽  
S.-B. Chun
Keyword(s):  
Natural Frequencies ◽  
Disk System ◽  
Flexible Shaft ◽  
Flexible Disk

Vibration Characteristics of a Rotor-Flexible Disk System: In Case of HDD Spindle-Motor System

1999 ◽  
Author(s):  
D. C. Han ◽  
S. H. Choi ◽  
K. B. Park ◽  
S. C. Jung
Keyword(s):  
Hard Disk Drive ◽  
Hard Disk ◽  
Disk Drive ◽  
Spindle Motor ◽  
Vibration Characteristics ◽  
Rotating Shaft ◽  
Disk System ◽  
Assumed Mode Method ◽  
Mode Method ◽  
Flexible Disk

Abstract In this paper we investigate the vibration characteristics of a rotor system with flexible disks. The coupled vibration mode between rotating shaft and the flexible disk are analyzed for lateral and axial vibrations respectively. Gyro and sheer effects are considered for the modeling of lateral vibrations. An assumed mode method was used for the disk modeling considering gyro effects. For a numerical example hard disk drive is considered. The natural frequencies of the motor-spindle system with flexible disk of hard disk drive was calculated and compared to the experimental data.

On the Unstable Vibrations of a Shaft Carrying an Unsymmetrical Rotor

1964 ◽  
Vol 31 (3) ◽  
pp. 515-522 ◽  
Author(s):  
Toshio Yamamoto ◽  
Hiroshi O¯ta
Keyword(s):  
Natural Frequencies ◽  
Rotating Shaft ◽  
Unstable Region ◽  
Critical Speeds ◽  
Rotating Speed ◽  
Lateral Vibrations ◽  
Shaft System

In a rotating shaft system carrying an unsymmetrical rotor, there is always one unstable region in the neighborhood of the rotating speed at which the sum of two natural frequencies of the system is equal to twice the rotating speed of the shaft. In this unstable region two unstable lateral vibrations with frequencies P1 and P2 take place simultaneously and grow up steadily. Generally, frequencies P1 and P2 are not equal to the rotating speed ω of the shaft and the sum of these P1 + P2 is always equal to 2ω. Of course there are other unstable regions which appear at the major critical speeds.

Vibration of Flexibly Mounted Gyroscopes

1973 ◽  
Vol 15 (3) ◽  
pp. 225-231
Author(s):  
L. Maunder
Keyword(s):  
Natural Frequencies ◽  
Critical Speeds ◽  
Supporting Structure ◽  
Vibrational Characteristics

Flexibility in the supporting structure of two-axis or single-axis gyroscopes is shown to have a radical effect on vibrational characteristics. The analysis determines the ensuing natural frequencies and critical speeds.

Determination of the Critical Operating Speeds of Planar Mechanisms by the Finite Element Method Using Planar Actual Line Elements and Lumped Mass Systems

1979 ◽  
Vol 101 (2) ◽  
pp. 210-223 ◽  
Author(s):  
S. Kalaycioglu ◽  
C. Bagci
Keyword(s):  
Dynamic Systems ◽  
Natural Frequencies ◽  
Dynamic Equilibrium ◽  
Large Error ◽  
Free Vibrations ◽  
Lumped Mass ◽  
Critical Speeds ◽  
Rotating Shafts ◽  
Line Elements ◽  
Kinematic Motion

It has been a well-established fact that dynamic systems in motion experience critical speeds, such as rotating shafts and geared systems whose undeformed reference geometry remain the same at all times. Their critical speeds are determined by their natural frequencies of considered type of free vibrations. Linkage mechanisms as dynamic systems in motion change their undeformed geometries as function of time during the cycle of kinematic motion. They do also experience critical operating speeds as rotating shafts and geared systems do, and their critical speeds are determined by the minima of their natural frequencies during a cycle of kinematic motion. Such a minimum occurs at the critical geometry of a mechanism, which is the position at which the maximum of the input power is required to maintain the instantaneous dynamic equilibrium of the mechanism. Actual finite line elements are used to form the global generalized coordinate flexibility matrix. The natural frequencies of the mechanism and the corresponding mode vectors (mode deflections) are determined as the eigen values and eigen vectors of the equations of instantaneous-position-free-motion of the mechanism. Method is formulated to include or exclude the link axial deformations, and apply to any number of loops having any type of planar pair. Critical speeds of planar four-bar, slider-crank, and Stephenson’s six-bar mechanisms are determined. Experimental results for the four-bar mechanism are given. Effect of axial deformations and link rotary inertias are investigated. Inclusion of link axial deformations in mechanisms having pairs with sliding freedoms is seen to predict critical speeds with large error.

NUMERICAL AND EXPERIMENTAL STUDY ON FREE VIBRATION OF DELAMINATED WOVEN FIBER GLASS/EPOXY COMPOSITE PLATES

2012 ◽  
Vol 12 (02) ◽  
pp. 377-394 ◽  
Author(s):  
J. MOHANTY ◽  
S. K. SAHU ◽  
P. K. PARHI
Keyword(s):  
Experimental Study ◽  
Aspect Ratio ◽  
Free Vibration ◽  
Boundary Conditions ◽  
Natural Frequencies ◽  
Numerical Study ◽  
Shear Deformation Theory ◽  
Composite Plates ◽  
Fiber Glass ◽  
Number Of Layers

This paper presents a combined experimental and numerical study of free vibration of industry-driven woven fiber glass/epoxy (G/E) composite plates with delamination. Using the first-order shear deformation theory, an eight-noded two-dimensional quadratic isoparametric element was developed, which has five degrees of freedom per node. In the experimental study, the influence of various parameters such as the delamination size, boundary conditions, fiber orientations, number of layers, and aspect ratio on the natural frequencies of delaminated composite plates are investigated. Comparison of the numerical results with experimental ones shows good agreement. Fundamental natural frequencies are found to decrease with the increase in the delamination size and fiber orientation and increases with the increase in the number of layers and aspect ratio of delaminated composite plates. The natural frequency of the delaminated composite plate varies significantly for different boundary conditions.

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