An approach for introducing damping to the flexural vibration of rotating shafts is presented. The idea of the approach is simple and the implementation is novel. The idea is to introduce viscoelastic angular spring at the boundaries. The spring would stiffen up and damp out the bending fluctuation, and therefore would increase the frequency range of operation and alleviate the vibration amplitudes in the vicinity of resonance of the shaft. The idea is implemented by introducing carbon/polyurethane composite hyperboloid couplings at the boundaries (ends) of the shaft. The mathematical model of the coupling is developed and solved, using finite element, for the fundamental flexural natural frequency and associated loss factor. From the results, the merits and feasibility of applying the flexible coupling to alleviate the flexural vibration of rotating shafts are addressed.
A mathematical model, based on Timoshenko beam assumption and the energy approach, for a rotating cylindrical
shaft with cylindrical constrained layer damping treatment is developed. The model is developed for a shaft made
from composite materials, and treated with a cylindrical constrained layer damping partially covering the length of
the shaft. The discrete equations of motion are developed using the assumed mode method. The developed equations
are applied to study the effect of the constraining cylinder's material and some geometric parameters on enhancing
the dynamic characteristic of the shaft; more specifically, on the bending stiffness and damping of the shaft. The
results, in general, indicate that the proposed treatment can be effective in enhancing the dynamic performance of
the shaft. Also, results indicate that for best (bending stiffness and damping) performance, optimized parameters
(length, thickness, material properties) are needed.
A new concept, the Passive Remote Electromechanical Dynamic Absorber (RDA) is investigated. The current design utilizes piezoelectric elements to convert the mechanical strain energy of a parent system into electrical energy, which is fed into the RDA. The RDA similarly uses piezoelectric elements to convert the applied electrical energy into mechanical self-excitation and vice versa. A lumped-system model of the coupled system is developed, accounting for the stiffness and mass of both the parent and RDA systems, along with a coupling stiffness term. Additionally, a three dimensional coupled-system finite element model is developed in ANSYS/Multiphysics. Experimental work is conducted to validate the concept of the lumped system model and to validate the finite element modeling technique. A reasonable correlation exists between the experimental results and the analytical predictions. Finite Element Analysis (FEA) provides a reasonable prediction of the RDA performance. Furthermore, analytical predictions of the RDA show a successful reduction of the parent response by up to ~30 db, in a narrow frequency band around its uncoupled resonant frequency. The overall qualitative agreement between the analytical and the experiment confirm the validity and potential of the proposed RDA for vibration suppression of dynamic systems.
Vibration suppression of a flexible four-bar mechanism is investigated. A generic four-bar mechanism, with flexible coupler, is considered for the investigation. Passive and active constrained layer damping techniques are adopted for the vibration suppression. The equations of motion are developed using the assumed mode method and the constrained Lagrange's equations, and are manipulated and solved using Maple and Matlab. Two types of responses are investigated: the free decay response due to an initial midpoint deflection of the flexible coupler, and the forced transient response due to an applied crank pulse torque. Effects of the application of passive and active constrained layer damping on the responses are discussed.
Electromechanical Surface Damping (EMSD) is a hybrid technique that incorporates constrained layer damping (CLD) and shunted piezoelectric element methods for the suppression of vibration in light beam-like or plate-like structures. The EMSD technique enhances the damping effectiveness (peak amplitude suppression) at targeted resonant frequencies, and may therefore be used to extend the damping effectiveness of the constrained layer damping technique over a broader temperature and frequency range than CLD alone. This performance enhancement was demonstrated experimentally by comparing the steady state frequency response of partially treated cantilever beams with that of an untreated beam. The experimental results also agreed with the results of a corresponding analytical model.
A fluid surface damping (FSD) element has been designed, produced and applied for the vibration suppression of a cantilever aluminum beam. The experimental steady-state frequency response of the treated beam, measured at the free end and subjected to a burst white noise excitation at the base, is determined and compared with the corresponding analytical results. The comparison shows a disagreement between the predicted and experimental results. Discussion of the potential sources of disagreement and of possible remedial measures is presented.
A fluid surface damping (FSD) technique proposed for vibration suppression of beam-like structures is applied to a generic simply supported aluminum beam. The steady-state frequency response of the FSD-treated beam at the vicinity of one end, due to an applied white noise displacement excitation at the other end, is determined using the finite element method. The response is found over a range of frequency covering the first four resonant frequencies and over a wide temperature range. Comparison of the results with the corresponding ones of a beam treated with the constrained layer damping method indicates that the FSD technique has a much greater potential for the vibration suppression of beam-like structures. Results also indicate that the FSD technique can provide a good vibration suppression over a wider temperature range.
The electromechanical surface damping technique (EMSD) is applied to suppress the bending and twisting peak vibration amplitudes of a cantilever plate. The technique is a combination of the constrained layer damping (CLD) and the shunted piezoelectric methods in which the constraining layer of the CLD is replaced by a shunted piezoelectric ceramic. The frequency responses, to a white noise random base excitation, of the EMSD-treated plate at the vicinity of the first and second bending and twisting resonant frequencies are determined and compared with the corresponding responses of the CLD-treatment. It is shown that, in general, the EMSD treatment provides more suppression of the bending and twisting peak vibration amplitudes than the conventional CLD treatment. The EMSD treatment, however, is more effective at higher frequencies and lower temperatures, which suggests that the EMSD method can be applied to extend the effective range of frequencies and/or temperatures of the conventional CLD method. The work presented is primarily analytical, however crude and preliminary experimental results are presented in order to demonstrate the feasibility of the EMSD technique.
The electromechanical surface damping (EMSD) technique, for controlling the peak vibration amplitudes of beam-like structures, is modified to extend the effective range of the approach. The technique is a combination of the constrained layer damping and the shunted piezoelectric methods, where the viscoelastic constrained layer attached to the vibrating surface is constrained by a shunted piezoelectric ceramic element. The mathematical model of the modified EMSD element is presented, implemented into a finite element algorithm and applied to demonstrate the ability of the technique to simultaneously and effectively suppress the first three resonant peaks of a generic aluminum cantilever beam.
An electromechanical surface damping (EMSD) technique is proposed. The technique is a combination of the constrained layer damping and the shunted piezoelectric methods, where the viscoelastic layer attached to the surface of the vibrating substructure is constrained by a shunted piezoelectric ceramic element. A mathematical model of the dynamic behavior of the coupled piezoelectric/constrained layer/substructure (EMSD element) is developed, implemented into a finite element algorithm, and used to investigate the effect of some of the system parameters on the dynamic characteristics (the first three natural frequencies and modal loss factors) of a generic cantilever beam. The effect of the following system parameters is considered: storage modulus ratios, material loss factors, thickness ratios, and the axial location of the EMSD element. The algorithm is also used to demonstrate the effectiveness of the proposed EMSD technique in controlling the peak vibration amplitudes at the first two natural frequencies of the cantilever beam.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.