scholarly journals A New Method for Field-Balancing of High-Speed Flexible Rotors without Trial Weights

2014 ◽  
Vol 2014 ◽  
pp. 1-11 ◽  
Author(s):  
Y. A. Khulief ◽  
M. A. Mohiuddin ◽  
M. El-Gebeily
Keyword(s):  
Finite Element ◽  
Finite Element Modeling ◽  
High Speed ◽  
Flexible Rotor ◽  
Analytical Technique ◽  
Flexible Rotors ◽  
Physical Insight ◽  
Benchmark Solutions ◽  
Rotor Balancing ◽  
Insight Into

Flexible rotor balancing, in general, relies to a great extent on physical insight into the modal nature of the unbalance response. The objective of this investigation is to develop a hybrid experimental/analytical technique for balancing high-speed flexible rotors. The developed technique adopts an approach that combines the finite element modeling, experimental modal analysis, vibration measurements, and mathematical identification. The modal imbalances are identified and then transformed to the nodal space, in order to determine a set of physical balancing masses at some selected correction planes. The developed method does not rely on trial runs. In addition, the method does not require operating the supercritical rotor in a high-speed balancing facility, while accounting for the contribution of higher significant modes. The developed scheme is applied to a multidisk, multibearing, high-speed flexible rotor, where the interaction between the rotor-bending operating deflections and the forces resulting from the residual unbalance are appreciable. Some new benchmark solutions and observations are reported. The applicability, reliability, and challenges that may be encountered in field applications are addressed.

Demonstration of a Unified Approach to the Balancing of Flexible Rotors

1981 ◽  
Vol 103 (1) ◽  
pp. 101-107 ◽  
Author(s):  
M. S. Darlow ◽  
A. J. Smalley ◽  
A. G. Parkinson
Keyword(s):  
Power Transmission ◽  
Substantial Reduction ◽  
Influence Coefficient ◽  
Flexible Rotor ◽  
Unified Approach ◽  
Test Rig ◽  
Multiple Mode ◽  
Flexible Rotors ◽  
Transmission Shaft ◽  
Rotor Balancing

A flexible rotor balancing procedure, which incorporates the advantages and eliminates the disadvantages of the modal and influence coefficient procedures, has been developed and implemented. This new procedure, referred to as the Unified Balancing Approach, has been demonstrated on a supercritical power transmission shaft test rig. The test rig was successfully balanced through four flexural critical speeds with a substantial reduction in effort as compared with the effort required in modal and influence coefficient balancing procedures. A brief discussion of the Unified Balancing Approach and its relationship to the modal and influence coefficient methods is presented. A series of tests which were performed to evaluate the effectiveness of various balancing techniques are described. The results of the Unified Balancing Approach tests are presented and discussed. These results confirm the superiority of this balancing procedure for the supercritical shaft test rig in particular and for multiple-mode balancing in general.

Friction Induced Vibration in Windscreen Wiper Contacts

2015 ◽  
Vol 137 (4) ◽  
Author(s):  
Tom Reddyhoff ◽  
Oana Dobre ◽  
Julian Le Rouzic ◽  
Nicolaas-Alexander Gotzen ◽  
Hilde Parton ◽  
...  
Keyword(s):  
Finite Element ◽  
Finite Element Modeling ◽  
High Speed ◽  
Contact Angles ◽  
Element Modeling ◽  
Friction Measurements ◽  
Mixed Lubrication Regime ◽  
Bending Modes ◽  
Intermediate Surface ◽  
Friction Induced Vibration

This research is aimed at understanding the mechanisms that give rise to friction induced noise in automotive windscreen wipers, with a focus on frequencies between 500 and 3500 Hz. To study this phenomenon, experimental friction, sound, and high-speed video measurements are combined with finite element modeling of a rubber wiper/glass contact. In agreement with previous research, simultaneous sound and friction measurements showed that wiper noise in this frequency range results from the negative damping effect caused by the dependence of friction on speed in the mixed lubrication regime. Furthermore, during sliding, the friction induced noise recorded by the microphone occurred in one of two frequency ranges (close to 1000 Hz and between 2000 and 2500 Hz). These coincided closely with the eigen-frequencies of first two bending modes, predicted by finite element modeling. Experimental observations also showed the wiper to be oscillating backward and forward without any torsional motion and that the thickness of the glass had no effect on the emitted noise. These observations highlight how friction induced noise—although caused by conditions within contact—has characteristics that are determined by the structure of the excited component. A number of additional findings are made. Most importantly, both experiment and finite element modeling showed that the presence of water in contact with the wiper modulates the frequency and amplitude of the emitted noise by effectively adding mass to the vibrating system. While this is occurring, Faraday-like standing waves are observed in the water. In addition to this, friction induced vibration is shown only to occur for glass surfaces with intermediate surface energies, which is possibly due to high contact angles preventing water reaching the contact. Based on the understanding gained, a number of suggestions are made regarding means of reducing windscreen wiper noise.

scholarly journals Finite element modeling of high-speed milling 7050-T7451 alloys

2020 ◽  
Vol 43 ◽  
pp. 471-478
Author(s):  
Xianghui Huang ◽  
Jinyang Xu ◽  
Ming Chen ◽  
Fei Ren
Keyword(s):  
Finite Element ◽  
Finite Element Modeling ◽  
High Speed ◽  
High Speed Milling ◽  
Element Modeling

Theoretical and Experimental Studies on Squeeze Film Stabilizers for Flexible Rotor-Bearing Systems Using Newtonian and Viscoelastic Lubricants

1990 ◽  
Vol 112 (4) ◽  
pp. 473-482 ◽  
Author(s):  
B. Halder ◽  
A. Mukherjee ◽  
R. Karmakar
Keyword(s):  
High Speed ◽  
Experimental Studies ◽  
Squeeze Film ◽  
Experimental Investigations ◽  
Flexible Rotor ◽  
Stability Range ◽  
High Speeds ◽  
Flexible Rotors ◽  
Rotor Bearing

A combination of a squeeze film damper and a plane journal bearing is studied as a stabilizing scheme. The damper is made to play the role of a stabilizer to postpone the instability threshold speeds of flexible rotors. Both Newtonian and viscoelastic fluids are used in the rotor-bearing system. Dynamics of the system is theoretically analyzed using bond graphs. Analysis reveals that the use of a Newtonian fluid in the stabilizer largely improves the high speed stability range. However, viscoelastic stabilizing fluid has a detrimental effect on highly flexible rotors. Experimental investigations, conducted on a flexible rotor (natural frequency, 30 Hz), confirm the theoretical findings. In addition, experiments indicate that though the use of viscoelastic stabilizing fluids leads to instability in flexible rotors, the growth of large amplitude whirl is postponed to very high speeds.

Modally Tuned Influence Coefficients for Low-Speed Balancing of Flexible Rotors

2013 ◽  
Vol 136 (2) ◽  
Author(s):  
Y. A. Khulief ◽  
Wasiu Oke ◽  
M. A. Mohiuddin
Keyword(s):  
Experimental Test ◽  
High Speed ◽  
Mode Shapes ◽  
Flexible Rotor ◽  
Test Rig ◽  
Low Speed ◽  
Modal Characteristics ◽  
Flexible Rotors ◽  
Influence Coefficients ◽  
Experimental Test Rig

The need to devise a low-speed balancing method for balancing high-speed rotors was recognized and addressed. In this paper, a scheme that combines both the influence coefficients and modal balancing techniques is presented. The scheme is developed for low-speed balancing of high-speed rotors, and relies on knowledge of the modal characteristics of the rotor. The conditions for applicability of the method were stated in the light of the experientially estimated rotor deflection mode shapes. An experimental test rig of a flexible rotor was constructed to verify the applicability and reliability of the low-speed balancing scheme.

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