687 research outputs found
Research on sound insulation characteristics of the friction stir welding magnesium alloy sheet
The friction stir welding (FSW) on magnesium alloy has already been widely used. Therefore, the research on its sound insulation characteristics appears particularly significant, based on ALE (Arbitrary Lagrangian Eulerian) adaptive meshing technique of ABAQUS/Explicit, the FSW procedure was numerically simulated and the modal solution, just a little different from the experimental result, was finally obtained, which has verified the validity of the established model, and obtain the response result to be imported into professional acoustic software to calculate the sound insulation characteristics. Subsequently, the structure-acoustic coupling method was employed to calculate the noise reduction in FSW on magnesium alloy, and through comparison with the experimental result, this coupling method proved feasible to predict the sound insulation characteristics in FSW on magnesium alloy. Furthermore, the result has also revealed that FSW could increase the noise reduction at intermediate or low frequency, in addition, which was 2Â dB higher on the frontal welding surface than the reverse one. Consequently, at the installation of magnesium alloy welding parts, the frontal or reverse surface shall be reasonably selected to face the noise source in accordance with the practical situation, so as to improve the sound insulation performance to a greater extent. To some extent, the research achieves the combination of welding and acoustic
Simulation and experimental investigation of high-speed projectile impacting closed-cell aluminum foam
In order to analyze the impact acceleration of the projectile impacting the aluminum foam material, a dynamic non-linear finite element model of the projectile impacting the closed-cell aluminum foam experiment device was established and verified by the experiment. It is found that the numerical simulation results of projectile impact closed-cell aluminum foam are consistent with the change of experimental results. When the projectile impacts the homogeneous closed-cell aluminum foam, the impact acceleration is trapezoidal and the impact peak and pulse width are related to the density of the aluminum foam material. With the increase of the porosity of the aluminum foam, the peak value of the acceleration rises and the pulse width of acceleration decreases
Vortex Dynamics in Rotating Rayleigh-B\'enard Convection
We investigate the spatial distribution and dynamics of the vortices in
rotating Rayleigh-B\'enard convection in a reduced Rayleigh-number range
. Under slow rotations (), the
vortices are randomly distributed. The size-distribution of the Voronoi cells
of the vortex centers is well described by the standard distribution.
In this flow regime the vortices exhibit Brownian-type horizontal motion. The
probability density functions of the vortex displacements are, however,
non-Gaussian at short time scales. At modest rotating rates
() the centrifugal force leads to radial
vortex motions, i.e., warm cyclones (cold anticyclones) moving towards (outward
from) the rotation axis. The mean-square-displacements of the vortices increase
faster than linearly at large time. This super-diffusive behavior can be
satisfactorily explained by a Langevin model incorporating the centrifugal
force. In the rapidly rotating regime () the
vortices are densely distributed, with the size-distribution of their Voronoi
cells differing significantly from the standard distribution. The
hydrodynamic interaction of neighboring vortices results in formation of vortex
clusters. Inside clusters the correlation of the vortex velocity fluctuations
is scale free, with the correlation length being approximately of the
cluster length. We examine the influence of cluster forming on the dynamics of
individual vortex. Within clusters, cyclones exhibit inverse-centrifugal motion
as they submit to the motion of strong anticyclones, while the velocity for
outward motion of the anticyclones is increased. Our analysis show that the
mobility of isolated vortices, scaled by their vorticity strength, is a simple
power function of the Froude number
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