Search results for "Perforated plate"

Damping performance of finite microperforated plates using multi-sized and spacial distributions of perforations

2023

In the context of structural dynamics, recent works by the authors showed that microperforations can be used to mitigate vibration. Microperforated plates (MPPs) have been shown to exhibit substantial added damping stemming from fluid-structure interactions and visco-thermal effect mechanisms in the boundary layers of the perforations during relative motion between the solid and the fluid contained in the perforations. The added damping reaches a maximum for a characteristic frequency, depending only on the perforation diameter. Choosing the perforation diameter so that the characteristic frequency coincides with the natural frequency of the plate reduces the mode contribution of the plate.…

Acoustic properties of plates with unevenly distributed macro perforations backed by woven meshes

2012

A hybrid model describing the acoustic properties of plates with macro-perforations that can be unevenly distributed on the plate surface and backed by woven or precision woven meshes with microscopic perforations is proposed. The plate perforations may be of circular or rectangular shapes. Since the perforated plate may not necessarily be considered as an equivalent fluid, its surface impedance is calculated by the Maa model [Noise Control Eng. J. 29, 77-84 (1987)], whereas the Johnson-Champoux-Allard model [J. Appl. Phys. 70, 1975-1979 (1991)] is used for the mesh. It is observed that the absorption of the carrying plate seems to depend on the hydraulic diameter of the perforations and no…

On the measurement and prediction of the sound absorption coefficient of air-cavity backed perforated plates considering the holes interaction effect…

2012

International audience; This paper deals with the measurement and prediction of air cavity backed perforated plates considering the holes interaction effect under relatively low sound excitation. A revised expression for the radiation contribution is proposed to properly account for the holes interaction effect. This expression is integrated in the characteristic impedance expression following Atalla and Sgard [J. Sound Vib. 303, 195-208 (2007)] model. Perforated plate specimens with different centre-to-centre holes distances (pitches) are built and tested using an impedance tube. The particular cases of holes interaction effect with constant low porosity and of holes interaction effect wit…

Sound absorption coefficient of a porous material covered with a low open area perforated plate under high sound excitation

2012

International audience; The sound absorption coefficient of porous materials covered with low open area perforated plate is studied under high sound intensities in the absence of mean flow. The theoretical considerations are based on the equivalent fluid following the Johnson-Champoux-Allard approach and the use of the transfer matrix method. To take into account the high sound levels effects, the air flow resistivity of each layer is modified following the Forchheimer law. Two specimens of perforated plate are built and tested when backed by a polymeric foam and a fibrous material. A specific impedance tube setup is developed for the measurement of the surface acoustic impedance for sound …

Stress and strain distribution in perforated plate loaded in median plane

2019

Iron Age craftworks in the southeast of the Iberian Peninsula. An approach based in Cultural Inheritance Theory

2021

Este trabajo tiene por objeto realizar una aproximación a las artesanías sobre materias duras de origen animal durante la Edad del Hierro en la PI y al estudio de los materiales como un medio para acercarnos a la sociedad que los produjo.  La problemática abordada contempla los procesos de la producción artesanal, la transmisión del conocimiento y la circulación de algunos de estos bienes. Hemos elegido dos tipos de piezas singulares: los peines de marfil y las placas de telar de hueso. Consideramos que este tipo de producciones constituye un fenómeno complejo y conforma una práctica cultural que recrea con códigos propios los gustos y la demanda de la época. A nivel metodológico, la Théori…