The Effect of Structural Damping on the Forced Vibrations of Cylindrical Sandwich Shells

1966 ◽  
Vol 88 (3) ◽  
pp. 318-323 ◽  
Author(s):  
I. W. Jones ◽  
V. L. Salerno
Keyword(s):  
Approximate Formula ◽  
Forced Vibrations ◽  
Radial Vibration ◽  
Radial Load ◽  
Resonant Response ◽  
Damping Properties ◽  
Structural Damping ◽  
Resonant Vibrations ◽  
Cylindrical Sandwich Shell ◽  
Time Harmonic

This paper presents an examination of the effects of structural damping on the axisymmetric vibrations of a cylindrical sandwich shell. It is shown that the use of core materials with high damping properties can result in large reductions in resonant response over conventional materials. The radial vibration of the shell resulting from a time harmonic radial load is first calculated by an exact method. The radial vibration is then calculated by an approximate formula, which requires only a knowledge of the damping properties and the natural (undamped) modes. In numerical examples the resonant vibrations of two steel-faced cylinders are compared. One has a polymeric, the other an elastomeric core. The results indicate that for the assumed conditions they are both effective for suppressing resonant vibration, the polymeric core being generally more effective than the elastomeric core.

Structural Damping Enhancement of Nanocomposites With Engineered Vapor Grown Carbon Nanofiber Paper

2006 ◽  
Author(s):  
Jihua Gou ◽  
Haichang Gu ◽  
Gangbing Song
Keyword(s):  
Carbon Nanotubes ◽  
Energy Dissipation ◽  
Carbon Nanofibers ◽  
Composite Laminates ◽  
Carbon Nanofiber ◽  
Glass Fibers ◽  
Hybrid Nanocomposites ◽  
Structural Vibration ◽  
Damping Properties ◽  
Structural Damping

Due to their nanometer size and low density, the surface area to mass ratio of carbon nanotubes and carbon nanofibers is extremely large. In addition, the large aspect ratio and high elastic modulus of carbon nanotubes and carbon nanofibers allow for large differences in strain between the constituents in the nanocomposites, which could enhance the interfacial energy dissipation ability. While there are many reported benefits of carbon nanotubes and carbon nanofibers in the nanocomposites, the potential of carbon nanotubes and carbon nanofibers to enhance the structural damping properties of nanocomposites has not been fully explored. This paper presents a novel process to manufacture multifunctional and cost-effective hybrid nanocomposites through integrating engineered carbon nanofiber paper into traditional fiber reinforced composites to improve the structural damping properties. The vacuum-assisted resin transfer molding (VARTM) process was employed to fabricate the nanocomposites by using engineered carbon nanofiber papers as inter-layers or surface layers of traditional composite laminates. To characterize the structural damping properties, the influence of frequency dependence was analyzed through the experiments conducted using the nanocomposite beams. It was found that there is up to 200–700% increase of the damping ratios at higher frequencies. It was found that the connectivities between carbon nanofibers and short glass fibers within the carbon nanofiber paper were responsible for the significant energy dissipation in the nanocomposites during structural vibration applications.

Damping Performance of Polychloroprene Rubber for Unconstrained Damping Applications

2021 ◽  
Vol 106 ◽  
pp. 131-136
Author(s):  
Prasanth Kumar Mallipudi ◽  
Padala Jyothi ◽  
N. Ramanaiah ◽  
V.V.S. Bhaskara Raju
Keyword(s):  
Vibration Control ◽  
Layer Thickness ◽  
Dynamic Characteristics ◽  
Loss Factor ◽  
Structural Response ◽  
Experimental Results ◽  
Viscoelastic Layer ◽  
Damping Properties ◽  
Structural Damping ◽  
Static And Dynamic Characteristics

Damping properties are crucial in determining the dynamic structural response. In this paper, the experimental results for Neoprene rubber of 40, 50 and 60 shore A hardness are reported in view of improving structural damping to control noise and vibrations. Additionally, the system loss factors of the unconstrained layer damped structures of same material were predicted by Ross-Kerwin-Ungar equation to validate the obtained experimental results. The results showed that Neoprene rubber (also known as Polychloroprene) of 60 shore A showed better static and dynamic characteristics than those of the 40 and 50 shore A hardness. The system loss factor results reached the saturation when the applied viscoelastic layer thickness was increased from 40 mm to 50 mm in unconstrained damping. As such, the proposed method can help to build a database of the properties of various materials which are applicable in the design of noise and vibration control.

The Vibration of an Internally Damped Sandwich Plate Radiating Into a Fluid Medium

1965 ◽  
Vol 87 (3) ◽  
pp. 379-384 ◽  
Author(s):  
I. W. Jones ◽  
V. L. Salerno
Keyword(s):  
Sandwich Plate ◽  
Internal Damping ◽  
Damping Properties ◽  
Pressure Loading ◽  
Honeycomb Core ◽  
Fluid Medium ◽  
At Resonance ◽  
Time Harmonic ◽  
Honeycomb Sandwich ◽  
Aluminum Honeycomb

An analysis is given for the vibration of a long sandwich plate with linear internal damping properties. The plate is subjected to a time-harmonic pressure loading of constant amplitude and is considered vibrating both in vacuo and in an environment consisting of vacuum on one side and a fluid medium on the other. Numerical results are presented for both a conventional and a highly damped sandwich plate. The conventional (aluminum honeycomb) sandwich plate produces only a small amount of damping, but when the honeycomb core is replaced by a highly dissipative thermoplastic, the maximum deflection and stress at resonance are reduced theoretically by about two orders of magnitude.

FLEXURAL VIBRATION SUPPRESSION OF GLASS FIBER/CuZnAl SMA COMPOSITE

2012 ◽  
Vol 05 (01) ◽  
pp. 1250014 ◽  
Author(s):  
CARLO ALBERTO BIFFI ◽  
PAOLA BASSANI ◽  
AUSONIO TUISSI ◽  
MARCO CARNEVALE ◽  
NORA LECIS ◽  
...  
Keyword(s):  
Glass Fiber ◽  
Vibration Suppression ◽  
Functional Characterization ◽  
Flexural Vibration ◽  
Thin Sheets ◽  
Damping Properties ◽  
Structural Damping ◽  
Laser Technology ◽  
Martensitic State

This work proposes the functional characterization of a composite material, suitable for passive suppression of flexural vibration of beams and shells. Two patterned thin sheets of CuZnAl Shape Memory Alloy (SMA) are embedded into a layered beam of glass fiber. The composite combines the density and stiffness of the glass fiber with high damping properties of SMA in martensitic state. Properly shaped patterning of the SMA sheets, for improving adhesion between the SMA and glass fiber, is performed by means of laser technology. The effect of the laser micromachining on transformation temperatures and internal friction properties of the SMA elements are analyzed. Finally, measurements of the structural damping of the layered glass fiber/SMA composite are reported and the flexural vibration suppression, due to the embedded CuZnAl sheets, is shown.

scholarly journals PASSIVE VIBRATION SUPPRESSION OF STRUCTURES IN THE VICINITY OF NATURAL FREQUENCIES USING PIEZOEFFECT

2019 ◽  
Vol 15 (2) ◽  
pp. 125-134
Author(s):  
Nelly Rogacheva
Keyword(s):  
Boundary Value Problem ◽  
Resonant Frequency ◽  
Natural Frequencies ◽  
Vibration Suppression ◽  
Mechanical Load ◽  
Electrical Energy ◽  
Forced Vibrations ◽  
Resonant Vibrations ◽  
Laminated Beam ◽  
Piezoelectric Layers

The proposed method of passive vibration suppression of structures is based on the use of the piezoe­lectric effect, which consists in the ability of the piezoelectric material to convert electrical energy into mechani­cal energy, and conversely. As it is known if the frequency of forced vibrations tends to the resonant frequency, all the desired quantities (forcers, moments, displacements and deformations) grow indefinitely. A new idea is that as we approach the resonant frequency, we change the electrical conditions on the electrodes of piezoelectric layers, thereby obtaining a different boundary value problem and a different spectrum of natural frequencies. Thus, we manage to get away from the resonant vibrations of the structure. Using the example of a laminated beam with elastic and piezoelectric layers the possibility of damping vibrations caused by mechanical load is studied. In this paper, a mathematically based model is used to solve the problem in question. The calculations are performed and the results are presented in the form of graphs. It is shown that forcers, moments, displace­ments and deformations of beam in the vicinity of the natural frequency can be significantly reduced by as a re­sult of changes in the electrical conditions on the electrodes of the piezoelectric layers.

scholarly journals Моделирование демпферов из вязкоупругих материалов

2021 ◽  
Vol 91 (3) ◽  
pp. 388
Author(s):  
Ю.В. Максимов ◽  
Ю.С. Легович ◽  
Д.Ю. Максимов
Keyword(s):  
Forced Vibrations ◽  
Frequency Characteristics ◽  
Point Of View ◽  
Damping Properties ◽  
Viscoelastic Materials ◽  
Linear Region ◽  
Elastic Deformations ◽  
Materials Used ◽  
Dynamics Problems ◽  
Correct Data

The consideration of damping in structural dynamics problems is an important and non-trivial problem. Its complexity, not least, is due to the need to set the correct data for the materials used and to select a model suitable for analysis. In this paper, we consider some models of viscoelastic materials from the point of view of the possibilities of using these models for the harmonic analysis of the damping properties of various materials in the linear region of elastic deformations. The proposed analysis is based on the use of parameters of viscoelastic materials specified in the form of coefficients of the differential equation of small forced vibrations. It is shown that the considered models are characterized by a different frequency dependence of the parameters of the simulated materials. This opens up the possibility of combining the model with the frequency characteristics of its parameters, approaching the frequency characteristics of the parameters of the studied viscoelastic materials.

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