Vibration Analysis and Health Monitoring of Cracks in Composite Disk Rotor Systems

2005 ◽  
Author(s):  
Xin Hai ◽  
George Flowers ◽  
Roland Horvath ◽  
Jerry Fausz
Keyword(s):  
Health Monitoring ◽  
Natural Frequencies ◽  
Experimental Testing ◽  
Vibration Characteristics ◽  
Rotor Systems ◽  
Plane Vibration ◽  
Fea Model ◽  
Rotating Systems ◽  
Out Of Plane ◽  
Composite Disk

Cracks and voids are common defects in rotating systems and are a precursor to fatigue-induced failure. Identifying the presence and growth of cracks is a critical concept for the health monitoring and diagnostics of such systems. A combined computational and experimental study of the vibration characteristics of a composite hub flywheel rotor system with a cracked hub disk is presented. First, experimental testing of both in-plane and out-of-plane vibration characteristics using a rotor with a composite disk hub supporting a relatively massive rim was conducted. A crack was deliberately introduced into the hub disk during fabrication. Based upon these results, a finite element (FEA) model was developed to further explore the relationship between natural frequencies and crack properties. Finally, a simplified theoretical model for the primary in-plane vibration mode was developed and used in a series of parametric studies. Good agreement was found between the model predictions and the experimental results. It was observed that the presence of a crack tends to affect both the magnitudes and distribution of the rotor natural frequencies. Certain primary frequencies for rotors with a crack are smaller than for those without a crack. In addition, the frequency values of associated with the “in-crack” direction are generally smaller than those associated with the “off-crack” direction, introducing a non-symmetry into the rotordynamics which can serve as an indicator for rotor health monitoring.

Vibrations of an Intermediately Supported U-Bend Tube

1975 ◽  
Vol 97 (1) ◽  
pp. 23-32 ◽  
Author(s):  
L. S. S. Lee
Keyword(s):  
Natural Frequency ◽  
Natural Frequencies ◽  
Experimental Tests ◽  
Bending Stiffness ◽  
Stiffness Ratio ◽  
Plane Vibration ◽  
Straight Beam ◽  
Out Of Plane ◽  
Straight Segments ◽  
Good Agreement

Vibrations of an intermediately supported U-bend tube fall into two independent classes as an incomplete ring of single span does, namely, the in-plane vibration and the coupled twist-bending out-of-plane vibration. Natural frequencies may be expressed in terms of a coefficient p which depends on the stiffness ratio k, the ratio of lengths of spans, and the supporting conditions. The effect of the torsional flexibility of a curved bar acts to release the bending stiffness of a straight beam and hence decrease the natural frequency. Some conclusions for an incomplete ring of single span may not be equally well applicable to the U-tube case due to the effects of intermediate supports and the presence of the supporting straight segments. Results of the analytical predictions and the experimental tests of an intermediately supported U-tube are in good agreement.

Stability of Out-of-Plane Vibration of a Uniform Beam Carrying an End Body and Attached Radially to a Rotating Hub

1999 ◽  
Author(s):  
S. Naguleswaran
Keyword(s):  
Analytical Study ◽  
Natural Frequencies ◽  
Force Distribution ◽  
Sufficient Condition ◽  
Centre Of Mass ◽  
System Parameters ◽  
Plane Vibration ◽  
Uniform Beam ◽  
Out Of Plane ◽  
Zero Frequency

Abstract This paper reports an analytical study on the out-of-plane vibration and stability of a uniform beam attached to a rotating hub and carrying a rigid body at the other end. The parameters which govern the natural frequencies are the hub radius (root offset), speed of rotation of hub, the mass of the end body, its moment of inertia about an axis in the plane of rotation and through the centre of mass, the radial offset of the centre of mass from the beam end It is shown that for certain combinations of the system parameters a ‘tuned’ state (analogous to whirling of a shaft) is possible. It is also shown (hat for some combinations a natural frequency is zero (borderline of instability) even though the axial force distribution in the beam is tensile throughout. Negative centre of mass offset is a necessary but not sufficient condition for zero frequency to occur.

Triangular relationship between vibration modes of an elastically supported rigid body with a plane of symmetry

2011 ◽  
Vol 226 (5) ◽  
pp. 1254-1262 ◽  
Author(s):  
S-J Jang ◽  
J W Kim ◽  
Y J Choi
Keyword(s):  
Rigid Body ◽  
Natural Frequencies ◽  
Vibration Modes ◽  
Geometrical Properties ◽  
Plane Vibration ◽  
Numerical Example ◽  
Mass Centre ◽  
Out Of Plane ◽  
Triangular Relationship ◽  
Elastically Supported

The geometrical properties of vibration modes of a single rigid body with one plane of symmetry are presented. When in-plane vibration modes are represented by the axes normal to the plane of symmetry, three intersecting points of those axes and the plane of symmetry constitute two triangles whose orthocentres are coincident with the mass centre and planar couple point, while the induced wrenches of three out-of-plane modes are found to form two triangles whose orthocentres are lying on the mass centre and the perpendicular translation point. Examining these triangles reveals that the triangular areas are proportional to the distributions of the mass and stiffness in the vibrating system and the shapes of the triangles are related to the natural frequencies. A numerical example is provided to verify the proposed findings.

Free Out-of-Plane Vibration of a Ring Elastically Supported at Several Points

1982 ◽  
Vol 49 (4) ◽  
pp. 854-860 ◽  
Author(s):  
T. Irie ◽  
G. Yamada ◽  
H. Okada
Keyword(s):  
Differential Equation ◽  
Infinite Series ◽  
Natural Frequencies ◽  
Circular Ring ◽  
Mode Shapes ◽  
Matrix Differential Equation ◽  
Plane Vibration ◽  
Out Of Plane ◽  
Matrix Differential ◽  
Elastically Supported

An analysis is presented for the free out-of-plane vibration of a circular ring elastically supported against deflection, rotation, and torsion at several points located at equal angular intervals. The equations of out-of-plane vibration of the ring is expressed as a matrix differential equation by using the transfer matrix, the solution to which is conveniently given by infinite series. The vibrations arising in the ring are classified into several types, for each of which the natural frequencies and the mode shapes are calculated numerically up to higher modes.

Natural Frequencies of Out-of-Plane Vibration of Arcs

1982 ◽  
Vol 49 (4) ◽  
pp. 910-913 ◽  
Author(s):  
T. Irie ◽  
G. Yamada ◽  
K. Tanaka
Keyword(s):  
Boundary Conditions ◽  
Cross Section ◽  
Timoshenko Beam ◽  
Natural Frequencies ◽  
Circular Cross Section ◽  
Beam Theory ◽  
Timoshenko Beam Theory ◽  
Plane Vibration ◽  
Out Of Plane

The natural frequencies of out-of-plane vibration based on the Timoshenko beam theory are calculated numerically for uniform arcs of circular cross section under all combination of boundary conditions, and the results are presented in some figures.

The Effect of Thermal Prestress on the Free Vibration Characteristics of Clamped Rectangular Plates: Theory and Experiment

1997 ◽  
Vol 119 (2) ◽  
pp. 243-249 ◽  
Author(s):  
K. D. Murphy ◽  
L. N. Virgin ◽  
S. A. Rizzi
Keyword(s):  
Free Vibration ◽  
Experimental Approach ◽  
Natural Frequencies ◽  
Vibration Characteristics ◽  
Rectangular Plates ◽  
Modal Coupling ◽  
Out Of Plane ◽  
Post Buckling ◽  
Initial Geometric Imperfections ◽  
Theory And Experiment

In a combined theoretical and experimental approach, the free vibration characteristics of a uniformly heated, fully clamped (out-of-plane), rectangular plate are considered. Specifically, this work focuses on the behavior of the small amplitude natural frequencies as the temperature is increased from the ambient. The effects of initial geometric imperfections, modal coupling, imperfect clamping (in-plane) and post-buckling are addressed. Comparisons between theory and experiment show excellent agreement.

Reduction of structural vibrations with the piezoelectric stacks ring

2020 ◽  
Vol 64 (1-4) ◽  
pp. 729-736
Author(s):  
Jincheng He ◽  
Xing Tan ◽  
Wang Tao ◽  
Xinhai Wu ◽  
Huan He ◽  
...  
Keyword(s):  
Vibration Control ◽  
Mechanical Energy ◽  
Electrical Energy ◽  
Structural Vibrations ◽  
Rotor Systems ◽  
Fea Model ◽  
Piezoelectric Stacks ◽  
Shunt Damping ◽  
Reduction Effect ◽  
Euler Bernoulli Beam

It is known that piezoelectric material shunted with external circuits can convert mechanical energy to electrical energy, which is so called piezoelectric shunt damping technology. In this paper, a piezoelectric stacks ring (PSR) is designed for vibration control of beams and rotor systems. A relative simple electromechanical model of an Euler Bernoulli beam supported by two piezoelectric stacks shunted with resonant RL circuits is established. The equation of motion of such simplified system has been derived using Hamilton’s principle. A more realistic FEA model is developed. The numerical analysis is carried out using COMSOL® and the simulation results show a significant reduction of vibration amplitude at the specific natural frequencies. Using finite element method, the influence of circuit parameters on lateral vibration control is discussed. A preliminary experiment of a prototype PSR verifies the PSR’s vibration reduction effect.

Dynamic model for high-speed rotors based on their experimental characterization

2017 ◽  
Vol 2 (4) ◽  
pp. 25
Author(s):  
L. A. Montoya ◽  
E. E. Rodríguez ◽  
H. J. Zúñiga ◽  
I. Mejía
Keyword(s):  
Dynamic Model ◽  
High Speed ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Experimental Characterization ◽  
Rotating Systems ◽  
Computing Performance ◽  
The Impact ◽  
Stiffness Distribution ◽  
Good Agreement

Rotating systems components such as rotors, have dynamic characteristics that are of great importance to understand because they may cause failure of turbomachinery. Therefore, it is required to study a dynamic model to predict some vibration characteristics, in this case, the natural frequencies and mode shapes (both of free vibration) of a centrifugal compressor shaft. The peculiarity of the dynamic model proposed is that using frequency and displacements values obtained experimentally, it is possible to calculate the mass and stiffness distribution of the shaft, and then use these values to estimate the theoretical modal parameters. The natural frequencies and mode shapes of the shaft were obtained with experimental modal analysis by using the impact test. The results predicted by the model are in good agreement with the experimental test. The model is also flexible with other geometries and has a great time and computing performance, which can be evaluated with respect to other commercial software in the future.

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