| 1. |
- Boij, Susann, et al.
(författare)
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Reflection of sound at area expansions in a flow duct
- 2003
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Ingår i: Journal of Sound and Vibration. - 0022-460X .- 1095-8568. ; 260:3, s. 477-498
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Tidskriftsartikel (refereegranskat)abstract
- An analytical model for scattering at area discontinuities and sharp edges in flow ducts and pipes is presented. The application we have in mind is large industrial duct systems, where sound attenuation by reactive and absorptive baffle silencers is of great importance. Such devices commonly have a rectangular cross-section, so the model is chosen as two-dimensional. Earlier solutions to this problem are reviewed in the paper. The modelling of the flow conditions downstream of the area expansion, with and without extended edges, and its implications for the resulting acoustic modes are discussed. Here, the scattering problem is solved with the Wiener–Hopf technique, and a Kutta condition is applied at the edge. The solution of the wave equation downstream of the expansion includes hydrodynamic waves, of which one is a growing wave. Theoretical results are compared with experimental data for the reflection coefficient for the plane wave, at frequencies below the cut-on for higher order modes. Influence of the interaction between the sound field and the flow field is discussed. A region where the reflection coefficient is strongly Strouhal number dependent is found.
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| 2. |
- Byström, Berth-Ove, et al.
(författare)
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Development of artificial hands for use in chain saw vibration measurement
- 1982
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Ingår i: Journal of Sound and Vibration. - 0022-460X .- 1095-8568. ; 82:1, s. 111-117
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Tidskriftsartikel (refereegranskat)abstract
- The dynamic properties of the human hand were measured in the laboratory. The results were compared with those obtained by others and used to test three different hand model ideas. One of these was further developed and designed to fit in a test rig. Measurements were made on chain saws in the rig during cutting and with the chain running free. The results are compared to similar measurements on hand held chain saws. The hand model test results show good agreement with the hand held measurements but have much better repeatability.
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| 3. |
- Edlund, G., et al.
(författare)
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The visualization of modes in a circular cochlear model by hologram interferometry
- 1978
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Ingår i: Journal of Sound and Vibration. - 0022-460X .- 1095-8568. ; 59:2, s. 299-303
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Tidskriftsartikel (refereegranskat)abstract
- This work has been carried out to study the possibilities of using hologram interferometry to examine the mechanical behavior of the inner ear. The purpose was to make a model of the cochlea with a curved and stiff basilar membrane and to look for both travelling wave and standing wave patterns. The level of excitation is approximately the same as found in actual hearing when scaled to model dimensions and hence much lower than in most previous model studies. Also in contrast to previous studies, curvature effects are investigated
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| 4. |
- Gupta, R.B., et al.
(författare)
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Elastic impact between a finite conical rod and a long cylindrical rod
- 1978
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Ingår i: Journal of Sound and Vibration. - 0022-460X .- 1095-8568. ; 60:4, s. 555-563
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Tidskriftsartikel (refereegranskat)abstract
- Elastic impact between a truncated finite conical rod and a long cylindrical rod is studied (i) experimentally, (ii) analytically, by using one-dimensional wave theory to obtain a closed-form solution, and (iii) numerically, by using a three-dimensional axisymmetric finite element model. The results are compared for cones of different lengths but with the same end diameters. The agreement between the results from studies (i) and (iii) is very good in general. As expected, the deviation of the results of study (ii) from those of studies (i) and (iii) becomes increasingly apparent as the slenderness of the cones decreases.
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| 5. |
- Gupta, R. B.
(författare)
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On optimum hammers and anvils
- 1982
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Ingår i: Journal of Sound and Vibration. - 0022-460X .- 1095-8568. ; 80:2, s. 223-231
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Tidskriftsartikel (refereegranskat)abstract
- Longitudinal elastic impact between a hammer and an anvil is studied with regard to maximizing the peak value of the impact force. For a given hammer, an appropriately chosen elastic anvil can generate a "maximax" impact force which is greater than the corresponding value for a rigid anvil. The improvements can be up to 50% for a class of hammer-anvil combinations. Such optimum combinations are determined for long, cylindrical hammers and finite conical anvils.
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| 6. |
- Gustafsson, Göran
(författare)
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Focusing of weak shock waves in a slightly elliptical cavity
- 1987
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Ingår i: Journal of Sound and Vibration. - 0022-460X .- 1095-8568. ; 116:1, s. 137-148
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents theoretical work on the wave motion in an elliptical water jet generator. Such a device consists of a water filled elliptical cavity in which a shock wave is induced at one focus by a spark discharge. The shock converges to the other focus and via a convergent duct is allowed to reflect off a free surface of the liquid at the front of a nozzle, whereby a jet is emitted. The initial value problem of how a weak shock develops and how it is reflected from the walls of a cavity with small eccentricity is studied by using acoustic theory and a perturbation technique. In order to account for the distensibility of the wall material its admittance is introduced as a parameter. The validity of the results is extended to larger eccentricities by use of Padé approximants and by comparison with a geometrical acoustics solution to the same problem. The implications of the results on the design of the water jet generator are indicated.
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| 7. |
- Knudsen, Jacob, et al.
(författare)
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Dynamic stability of weakly damped oscillators with elastic impacts and wear
- 2003
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Ingår i: Journal of Sound and Vibration. - : Academic Press. - 0022-460X .- 1095-8568. ; 263:1, s. 175-204
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Tidskriftsartikel (refereegranskat)abstract
- The dynamics of non-linear oscillators comprising of a single-degree-of-freedom system and beams with elastic two-sided amplitude constraints subject to harmonic loads is analyzed. The beams are clamped at one end, and constrained against unilateral contact sites near the other end. The structures are modelled by a Bernoulli-type beam supported by springs using the finite element method. Rayleigh damping is assumed. Symmetric and elastic double-impact motions, both harmonic and sub-harmonic, are studied by way of a Poincaré mapping that relates the states at subsequent impacts. Stability and bifurcation analyses are performed for these motions, and domains of instability are delineated. Impact work rate, which is the rate of energy dissipation to the impacting surfaces, is evaluated and discussed. In addition, an experiment conducted by Moon and Shaw on the vibration of a cantilevered beam with one-sided amplitude constraining stop is modelled. Bifurcation observed in the experiment could be captured
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| 8. |
- Lagerkvist, L., et al.
(författare)
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Experimental determination of mechanical impedance through strain measurement on a conical rod
- 1982
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Ingår i: Journal of Sound and Vibration. - 0022-460X .- 1095-8568. ; 85:4, s. 473-481
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Tidskriftsartikel (refereegranskat)abstract
- An impedance gauge based on measurement of strains at two different cross-sections of a conical gauge rod is tested. The gauge rod is in contact with the object at its narrow end while its wide end is driven by a harmonic vibrator. The length of the gauge rod is 260 mm and its end diameters are 9·8 mm and 20·1 mm. For cylindrical test objects a fair agreement is generally obtained between experimental and theoretical point impedances in the frequency range 50 Hz to 5 kHz. Further improvements in accuracy are expected to be feasible
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| 9. |
- Lagerkvist, L., et al.
(författare)
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Mechanical impedance gauge based on measurement of strains on a vibrating rod
- 1982
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Ingår i: Journal of Sound and Vibration. - 0022-460X .- 1095-8568. ; 80:3, s. 389-399
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Tidskriftsartikel (refereegranskat)abstract
- An impedance gage based on measurement of strains at two different cross-sections of a vibrating rod is analyzed and tested. The gage rod, which may have variable characteristic impedance, is in contact with the object at one end and is driven by a harmonic vibrator at the other end. For conical and cylindrical rods explicit relations between point impedance and measured strains are derived. For a cylindrical gage rod of steel with length 800 mm, diameter 10 mm, and distance between strain gages 250 mm a fair agreement was generally obtained between experimental and theoretical point impedances of cylindrical test objects in the frequency range 50 Hz to 1. 7 kHz. Significant improvements in accuracy over that of the tested prototype are expected to be feasible
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| 10. |
- Lagerkvist, L., et al.
(författare)
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Mechanical impedance gauge based on measurement of strains on an impacted rod
- 1983
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Ingår i: Journal of Sound and Vibration. - 0022-460X .- 1095-8568. ; 88:2, s. 225-231
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Tidskriftsartikel (refereegranskat)abstract
- An impedance gauge based on measurement of strains at two cross-sections of a slender rod is studied. The gauge rod is in contact with the object at one end while it is impacted at the other end. The impedance is evaluated from the two strain signals by means of a two-channel FFT-analyzer and a desk-top computer. Gauge prototypes with cylindrical and conical geometries are tested in the frequency range 50 Hz to 5 kHz for cylindrical objects with known theoretical point impedances. Satisfactory agreement between experimental and theoretical impedances is obtained for both prototypes.
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