Wave Propagation in Porous Materials

Fellah, Zine El Abiddine; Fellah, M.; Dépollier, Claude; Ogam, Erick; Mitri, F.G.

doi:10.5772/intechopen.72215

Cited by 5 publications

(3 citation statements)

References 32 publications

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“…While effective internally, lightweight materials are not suitable externally, so concrete is still preferred [ 18 ]. A balance between speed and density of sound and its effect on the acoustic properties of a porous material was studied by Kuczmarski et al [ 19 ], while the effect of tortuosity, porosity, and flow resistivity on reflection and transmission of acoustic waves in porous materials was the topic of [ 20 ]. Sun et al [ 21 ] demonstrated that the main reason for the difference in acoustic properties of materials produced via selective laser sintering is the difference in the unit structures.…”

Section: Introductionmentioning

confidence: 99%

Effect of 3D-Printed PLA Structure on Sound Reflection Properties

et al. 2022

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3D printing technique is currently one of the promising emerging technologies. It is used in many areas of human activity, including acoustic applications. This paper focuses on studying the sound reflection behavior of four different types of 3D-printed open-porous polylactic acid (PLA) material structures, namely cartesian, octagonal, rhomboid and starlit structures. Sound reflection properties were evaluated by means of the normal incidence sound reflection coefficient based on the transfer function method using an acoustic impedance tube. In this study, various factors affecting the sound reflection performance of the investigated PLA samples were evaluated. It can be concluded that the sound reflection behavior of the tested PLA specimens was strongly affected by different factors. It was influenced, not only by the type of 3D-printed open-porous material structure, but also by the excitation frequency, the total volume porosity, the specimen thickness, and the air gap size behind the tested specimen inside the acoustic impedance tube.

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Section: Introductionmentioning

confidence: 99%

Effect of 3D-Printed PLA Structure on Sound Reflection Properties

et al. 2022

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“…When a pressure gradient exists in a two-phasic porous material, there is relative motion between the fluid and the skeleton. According to the different research focus, porous material models are classified into various models such as heat transfer model [ 9 ], percolation model [ 10 ], and wave model [ 11 ].…”

Section: Introductionmentioning

confidence: 99%

Numerical Simulation of Elastic Wave Field in Viscoelastic Two-Phasic Porous Materials Based on Constant Q Fractional-Order BISQ Model

Wang

Qiu

et al. 2022

Materials

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The fractional-order differential operator describes history dependence and global correlation. In this paper, we use this trait to describe the viscoelastic characteristics of the solid skeleton of a viscoelastic two-phasic porous material. Combining Kjartansson constant Q fractional order theory with the BISQ theory, a new BISQ model is proposed to simulate elastic wave propagation in a viscoelastic two-phasic porous material. The corresponding time-domain wave propagation equations are derived, and then the elastic waves are numerically simulated in different cases. The integer-order derivatives are discretised using higher-order staggered-grid finite differences, and the fractional-order time derivatives are discretised using short-time memory central differences. Numerical simulations and analysis of the wave field characterisation in different phase boundaries, different quality factor groups, and multilayered materials containing buried bodies are carried out. The simulation results show that it is feasible to combine the constant Q fractional-order derivative theory with the BISQ theory to simulate elastic waves in viscoelastic two-phasic porous materials. The combination can better describe the viscoelastic characteristics of the viscoelastic two-phasic porous materials, which is of great significance for further understanding the propagation mechanism of elastic waves in viscoelastic two-phasic porous materials and viscoelastic two-phasic porous materials containing buried bodies. This paper provides a theoretical forward simulation for fine inversion and reconstruction of layer information and buried body structure in viscoelastic two-phasic porous materials.

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“…Tseng et al [ 10 ] proposed an analytical model to estimate the thermal conductivity of PU foam via heat transfer mechanisms. Erick et al [ 11 ], and Fellah et al [ 12 ], from a wave propagation aspect, provided different models of transmission of acoustic waves for porous materials with physical parameters. Placido et al [ 13 ], and Wu [ 14 ] analyzed different foam insulation morphological structures and established a geometrical cell model which was applied to predict foam insulation properties.…”

Section: Introductionmentioning

confidence: 99%

Modeling of Flexible Polyurethane Foam Shrinkage for Bra Cup Moulding Process Control

Yick

2018

Polymers

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Nowadays, moulding technology has become a remarkable manufacturing process in the intimate apparel industry. Polyurethane (PU) foam sheets are used to mould three-dimensional (3D) seamless bra cups of various softness and shapes, which eliminate bulky seams and reduce production costs. However, it has been challenging to accurately and effectively control the moulding process and bra cup thickness. In this study, the theoretical mechanism of heat transfer and the thermal conductivity of PU foams are first examined. Experimental studies are carried out to investigate the changes in foam materials at various moulding conditions (viz., temperatures, and lengths of dwell time) in terms of surface morphology and thickness by using electron and optical microscopy. Based on the theoretical and experimental investigations of the thermal conductivity of the foam materials, empirical equations of shrinkage ratio and thermal conduction of foam materials were established. A regression model to predict flexible PU foam shrinkage during the bra cup moulding process was formulated by using the Levenberg-Marquardt method of nonlinear least squares algorithm and verified for accuracy. This study therefore provides an effective approach that optimizes control of the bra cup moulding process and assures the ultimate quality and thickness of moulded foam cups.

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Wave Propagation in Porous Materials

Cited by 5 publications

References 32 publications

Effect of 3D-Printed PLA Structure on Sound Reflection Properties

Effect of 3D-Printed PLA Structure on Sound Reflection Properties

Numerical Simulation of Elastic Wave Field in Viscoelastic Two-Phasic Porous Materials Based on Constant Q Fractional-Order BISQ Model

Modeling of Flexible Polyurethane Foam Shrinkage for Bra Cup Moulding Process Control

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