The Damping Effects of Viscoelastic Materials: Part 2—Transverse Vibrations of Plates With Viscoelastic Coatings

1971 ◽  
Vol 93 (2) ◽  
pp. 651-655 ◽  
Author(s):  
Britt K. Pearce ◽  
Joseph R. Baumgarten
Keyword(s):  
Composite Plate ◽  
Metal Layer ◽  
Thin Plates ◽  
Viscoelastic Layer ◽  
Experimental Measurements ◽  
Transverse Vibrations ◽  
Theoretical Predictions ◽  
Rate Of Decay ◽  
Damping Effects ◽  
Viscoelastic Coatings

An energy method is employed to analyze a nonhomogeneous, damped plate composed of an elastic (metal) layer and an unconstrained viscoelastic layer. This analysis is limited to the case of thin plates subject to no constraints and vibrating freely in the fundamental mode. The theory developed enables one to predict the damped natural frequency and the rate of decay (in terms of logarithmic decrement) of the transverse vibrations of a composite plate of given dimensions and composed of two particular materials. Experimental measurements bear out the fact that theoretical predictions are indeed accurate. Plates with two symmetric viscoelastic coatings are also considered and their damping effects are compared to those of coatings applied to one side only.

The Damping Effects of Viscoelastic Materials: Part 1—Transverse Vibrations of Beams With Viscoelastic Coatings

1971 ◽  
Vol 93 (2) ◽  
pp. 645-650 ◽  
Author(s):  
Joseph R. Baumgarten ◽  
Britt K. Pearce
Keyword(s):  
Energy Method ◽  
Composite Beam ◽  
Metal Layer ◽  
Viscoelastic Layer ◽  
Experimental Measurements ◽  
Transverse Vibrations ◽  
Theoretical Predictions ◽  
Rate Of Decay ◽  
Damping Effects ◽  
Viscoelastic Coatings

An energy method similar to Rayleigh’s method is employed to analyze a nonhomogeneous, damped beam composed of an elastic (metal) layer and an unconstrained viscoelastic layer. This analysis is limited to the case of thin free-free beams vibrating freely in the fundamental mode. The theory developed enables one to predict the damped natural frequency and the rate of decay (in terms of logarithmic decrement) of the transverse vibrations of a composite beam of given dimensions and composed of two particular materials. Experimental measurements bear out the fact that theoretical predictions are indeed accurate. Beams with two symmetric elastic coatings are also considered and their damping effects are compared to those of coating applied to one side only.

scholarly journals Optical Analysis of Ball Bearing Starvation

1971 ◽  
Vol 93 (3) ◽  
pp. 349-361 ◽  
Author(s):  
L. D. Wedeven ◽  
D. Evans ◽  
A. Cameron
Keyword(s):  
Film Thickness ◽  
Ball Bearing ◽  
Point Contact ◽  
Experimental Measurements ◽  
Line Contact ◽  
Optical Analysis ◽  
Grease Lubrication ◽  
Theoretical Predictions ◽  
Pressure Stress ◽  
Starvation Conditions

Elastohydrodynamic oil film measurements for rolling point contact under starvation conditions are obtained using optical interferometry. The experimental measurements present a reasonably clear picture of the starvation phenomenon and are shown to agree with theoretical predictions. Starvation inhibits the generation of pressure and, therefore, reduces film thickness. It also causes the overall pressure, stress, and elastic deformation to become more Hertzian. Additional experiments using interferometry illustrate: the cavitation pattern, lubricant entrapment, grease lubrication, ball spin, and edge effects in line contact.

Flexural Vibrations of an Elastic Plate With Two Symmetric Viscoelastic Coatings

1967 ◽  
Vol 34 (1) ◽  
pp. 187-194
Author(s):  
Paul Hertelendy ◽  
Werner Goldsmith
Keyword(s):  
Composite Plate ◽  
Flexural Vibration ◽  
Complex Shear Modulus ◽  
Viscous Effects ◽  
Approximate Methods ◽  
Linear Viscoelastic Material ◽  
Complex Shear ◽  
Linear Viscoelastic ◽  
Modal Behavior ◽  
Viscoelastic Coatings

The flexural-vibration characteristics of a symmetric, doubly infinite composite plate consisting of two outer layers of a linear viscoelastic material bonded to an elastic core have been examined, the viscous effects in the coating being represented by a complex shear modulus. Calculations of the dispersive and damping effects have been obtained for the lowest three modes by an extension of the exact Rayleigh-Lamb equations. Loss factors of the lowest modes have also been evaluated by two readily computed approximate methods; the results have been compared with those from the exact solution. The material constants were chosen to be representative of a high-polymer coating and an aluminum core. The modal behavior of the systems and coupling effects are discussed.

scholarly journals The Effect of Attenuation from Fish on Passive Detection of Sound Sources in Ocean Waveguide Environments

2021 ◽  
Vol 13 (21) ◽  
pp. 4369
Author(s):  
Daniel Duane ◽  
Chenyang Zhu ◽  
Felix Piavsky ◽  
Olav Rune Godø ◽  
Nicholas C. Makris
Keyword(s):  
Remote Sensing ◽  
Propagation Path ◽  
Experimental Measurements ◽  
Sound Sources ◽  
Detection Range ◽  
Acoustic Waveguide ◽  
Passive Sensing ◽  
Surface Vessels ◽  
Theoretical Predictions ◽  
Radiated Sound

Attenuation from fish can reduce the intensity of acoustic signals and significantly decrease detection range for long-range passive sensing of manmade vehicles, geophysical phenomena, and vocalizing marine life. The effect of attenuation from herring shoals on the Passive Ocean Acoustic Waveguide Remote Sensing (POAWRS) of surface vessels is investigated here, where concurrent wide-area active Ocean Acoustic Waveguide Remote Sensing (OAWRS) is used to confirm that herring shoals occluding the propagation path are responsible for measured reductions in ship radiated sound and corresponding detection losses. Reductions in the intensity of ship-radiated sound are predicted using a formulation for acoustic attenuation through inhomogeneities in an ocean waveguide that has been previously shown to be consistent with experimental measurements of attenuation from fish in active OAWRS transmissions. The predictions of the waveguide attenuation formulation are in agreement with measured reductions from attenuation, where the position, size, and population density of the fish groups are characterized using OAWRS imagery as well as in situ echosounder measurements of the specific shoals occluding the propagation path. Experimental measurements of attenuation presented here confirm previous theoretical predictions that common heuristic formulations employing free space scattering assumptions can be in significant error. Waveguide scattering and propagation theory is found to be necessary for accurate predictions.

Thickness Deformation of Constrained Layer Damping: An Experimental and Theoretical Evaluation

2000 ◽  
Vol 123 (2) ◽  
pp. 213-221 ◽  
Author(s):  
Peter Y. H. Huang ◽  
Per G. Reinhall ◽  
I. Y. Shen ◽  
Jessica M. Yellin
Keyword(s):  
Mathematical Model ◽  
Transfer Functions ◽  
Viscoelastic Layer ◽  
Experimental Setup ◽  
Experimental Measurements ◽  
Constrained Layer Damping ◽  
Response Functions ◽  
Theoretical Evaluation ◽  
Calculated Frequency ◽  
Direct Measurements

This paper presents a study of thickness deformation of the viscoelastic material in constrained layer damping (CLD) treatments. The first goal of the study is to demonstrate the feasibility of using direct measurement to investigate thickness deformation in CLD treatments. The experimental setup consisted of a constrained layer beam cantilevered to a shaker, an accelerometer mounted at the cantilevered end, and two laser vibrometers that simultaneously measured the responses of the base beam and the constraining layer, respectively, at the free end. A spectrum analyzer calculated frequency response functions (FRFs) between the accelerometer inputs and the vibrometer outputs. Measured FRFs of the base beam and the constraining layer were compared to detect thickness deformation. Experimental results showed that direct measurements can detect thickness deformation as low as 0.5 percent. The second goal is to evaluate the accuracy of a mathematical model developed by Miles and Reinhall [7] that accounts for thickness deformation. FRFs were calculated by using the method of distributed transfer functions by Yang and Tan [13]. Comparison of the numerical results with the experimental measurements indicated that consideration of thickness deformation can improve the accuracy of existing constrained layer damping models when the viscoelastic layer is thick.

scholarly journals Bioinspired aerofoil adaptations: the next steps for theoretical models

2019 ◽  
Vol 377 (2159) ◽  
pp. 20190070 ◽  
Author(s):  
Lorna J. Ayton
Keyword(s):  
Experimental Data ◽  
Theoretical Models ◽  
Theoretical Modelling ◽  
Experimental Measurements ◽  
Far Field ◽  
Acoustic Analogy ◽  
Trailing Edge ◽  
Trailing Edge Noise ◽  
Theoretical Predictions ◽  
Field Noise

The extended introduction in this paper reviews the theoretical modelling of leading- and trailing-edge noise, various bioinspired aerofoil adaptations to both the leading and trailing edges of blades, and how these adaptations aid in the reduction of aerofoil–turbulence interaction noise. Attention is given to the agreement between current theoretical predictions and experimental measurements, in particular, for turbulent interactions at the trailing edge of an aerofoil. Where there is a poor agreement between theoretical models and experimental data the features neglected from the theoretical models are discussed. Notably, it is known that theoretical predictions for porous trailing-edge adaptations do not agree well with experimental measurements. Previous works propose the reason for this: theoretical models do not account for surface roughness due to the porous material and thus omit a key noise source. The remainder of this paper, therefore, presents an analytical model, based upon the acoustic analogy, to predict the far-field noise due to a rough surface at the trailing edge of an aerofoil. Unlike previous roughness noise models which focus on roughness over an infinite wall, the model presented here includes diffraction by a sharp edge. The new results are seen to be in better agreement with experimental data than previous models which neglect diffraction by an edge. This new model could then be used to improve theoretical predictions for far-field noise generated by turbulent interactions with a (rough) porous trailing edge. This article is part of the theme issue ‘Frontiers of aeroacoustics research: theory, computation and experiment’.

Analytic Calculations of the Branching Ratio and CP Violation in Bs0 → Ds+Ds− Decay

2020 ◽  
Vol 35 (15) ◽  
pp. 2050122
Author(s):  
H. R. Khan ◽  
E. H. Raslan ◽  
R. A. Reem
Keyword(s):  
Cp Violation ◽  
Decay Width ◽  
Branching Ratio ◽  
Gluon Condensate ◽  
Analytic Calculation ◽  
Experimental Measurements ◽  
Meson Decays ◽  
First Order ◽  
Theoretical Predictions ◽  
Charge Parity

We present an analytic calculation of Branching Ratio (BR) and Charge-Parity (CP) violating asymmetries of the [Formula: see text] meson decays to [Formula: see text] by calculating the amplitude and the decay width of the process including the chiral loop and gluon condensate to first-order. We find the BR of [Formula: see text] which is in agreement with other experimental measurements and theoretical predictions. We also calculate the direct CP violation, CP violation in mixing and CP violation due to interference which are [Formula: see text], [Formula: see text] and [Formula: see text], respectively.

Holographic measurement of the elastic–plastic boundary surrounding cold-expanded holes

1989 ◽  
Vol 24 (2) ◽  
pp. 103-106 ◽  
Author(s):  
R J Sanford ◽  
R E Link
Keyword(s):  
Holographic Interferometry ◽  
Experimental Results ◽  
Similar Process ◽  
Experimental Measurements ◽  
Cold Expansion ◽  
Elastic Plastic ◽  
Theoretical Predictions ◽  
Holographic Measurement

Experimental measurements of the elastic—plastic boundary surrounding split-sleeve cold-expanded holes in 7075-T651 aluminum were made using the technique of holographic interferometry. The levels of expansion investigated ranged from 1.5 per cent to 8.4 per cent. The experimentally determined elastic—plastic boundaries were compared with several theoretical predictions. The experimental results were also compared with the experimental results from another investigation of a similar process. Predictions of the elastic—plastic boundary based on the Hoffman—Sachs theory agreed with the experimental results for levels of cold expansion over the range 1.5—3 per cent expansion. The experimental results of this investigation predicted larger elastic—plastic boundaries than those measured in a separate investigation. Possible explanations for the differences are discussed.

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