Poroelastic Material Research Articles

Sizing optimization of microscopic structure of sound-absorbing poroelastic material

Sizing optimization of microscopic structure of sound-absorbing poroelastic material

Research on Sound Insulation Performance of Poroelastic Material in Complex Structure

A finite element model of the double-wall acoustic insulation structure with a air layer and an acoustic absorbent layer made of the poroelastic materials is set up, the responses of this acoustic-vibration system are calculated by using of the direct finite element method when having a diffuse incident acoustic field acting on the incident surface, the radiant acoustic power from the another surface are achieved, then the Transmission Loss(TL) are formulated using the incident acoustic power and the radiant acoustic power. The effects of the thicknesses, elastic modulus, flow resistivity and viscous lengths of the poroelastic materials on TL are analyzed. The results show that the thicknesses and elastic modulus have a significant effects on TL, TL are enhanced with the thicknesses increasing of the poroelastic materials layers, a 4.9dB addition of TL is achieved when thickness is added from 2cm to 3cm; TL are enhanced with the reduction of the elastic modulus in considered frequency range, and TL are reduced with the declining of viscous lengths and with the addition of the flow resistivity when the frequencies are higher than 600Hz.

Computational Investigation on the Biomechanical Responses of the Osteocytes to the Compressive Stimulus: A Poroelastic Model.

Osteocytes, the major type of bone cells embedded in the bone matrix and surrounded by the lacunar and canalicular system, can serve as biomechanosensors and biomechanotranducers of the bone. Theoretical analytical methods have been employed to investigate the biomechanical responses of osteocytes in vivo; the poroelastic properties have not been taken into consideration in the three-dimensional (3D) finite element model. In this study, a 3D poroelastic idealized finite element model was developed and was used to predict biomechanical behaviours (maximal principal strain, pore pressure, and fluid velocity) of the osteocyte-lacunar-canalicular system under 150-, 1000-, 3000-, and 5000-microstrain compressive loads, respectively, representing disuse, physiological, overuse, and pathological overload loading stimuli. The highest local strain, pore pressure, and fluid velocity were found to be highest at the proximal region of cell processes. These data suggest that the strain, pore pressure, and fluid velocity of the osteocyte-lacunar-canalicular system increase with the global loading and that the poroelastic material property affects the biomechanical responses to the compressive stimulus. This new model can be used to predict the mechanobiological behaviours of osteocytes under the four different compressive loadings and may provide an insight into the mechanisms of mechanosensation and mechanotransduction of the bone.

Sizing optimization of microstructure of sound-absorbing poroelastic material by homogenization method

Sizing optimization of microstructure of sound-absorbing poroelastic material by homogenization method

A novel flexible pressure sensor array for depth information of radial artery

Pulse wave collection from multi-points of radial artery under different static pressures is an essential method to diagnose diseases. However, there are some problems in the currently-used measuring instruments. Single-type sensor has limitations to pulse wave acquisition. It is not enough to set three sampling points to detect variation trend of radial artery pulse wave. Adaptation to different wrist surfaces and mutual interference of sensors are neglected. This paper proposes a novel flexible compound pressure sensor array for measuring radial artery pulse wave to overcome the problems mentioned above. Our compound pressure sensor consists of a piezoelectric sensor and a piezoresistive sensor which are used to measure pulse wave and static pressure separately. A bending structure of the sensor could guarantee the signal intensity and prevent the occurrence of inverted waveform. In this study, poroelastic materials are used to achieve flexible connection and decrease interference among sensors. In addition, the amplitude characteristics of pulse wave in radial artery are described and the arrangement and size of the sensor array is designed based on statistical data. Anti-interference, repeatability and validation experiments are carried out to evaluate the performance of the sensor array. The results show that the flexible compound pressure sensor array not only reflects depth information of radial artery pulse wave under a wide range of static pressures, but also has good repeatability and anti-interference performance.

A numerical investigation of damping in fuzzy oscillators with poroelastic coating attached to a host structure

This paper analyzes efficacy of fuzzy oscillators combined with poroelastic coatings to reduce low frequency vibrations. The authors had previously shown that the poroelastic interactions across contact interfaces are tunable for broadband rate-independent damping. As a follow-up to that work, dynamic analyses are conducted on a host structure interacting with multiple fuzzy oscillators through contact interfaces across poro/viscoelastic coatings. Contact interactions are modeled by Fractional Zener Models. As viscoelastic coating material, hevea rubber is chosen because of its exceptionally high damping characteristics (i.e., highest loss tangent). For the poroelastic coating, relaxed and unrelaxed compliances as well as maximum damping capacity are assumed as identical to the viscoelastic rubber coating. In the first step, the dominant vibration mode of a host structure is modeled as a single degree-of-freedom system. The modal frequency of the host structure is first assumed to match peak relaxation frequency of the viscoelastic coating (220 kHz). Then, the modal frequency is reduced to lower frequencies (20,100 and 200 Hz). In the next step of the analysis, the investigation is extended to a host structure modeled as a two degree of freedom system. Results show that, if relaxation frequencies of the viscoelastic and poroelastic materials are close to the modal frequency of the host structure, the vibration suppression performances of both coatings are similar. However, poroelastic coating outperforms the viscoelastic coating at lower modal frequencies due to its tunable dynamic relaxation properties. Viscoelastic coating, in contrast, responds as a spring, and loses its damping capacity away from its peak relaxation frequency. To explore the best possible performance of the poroelastic coatings for low frequency damping, an optimization routine is adopted, and optimal number of fuzzy oscillators with optimally distributed mass and frequency properties is found. Results promise up to ∼35 dB vibration reduction around the structural modes for the single degree of freedom systems. For two degree of freedom system, vibration reduction level is predicted up to ∼27 dB reduction for the first mode and ∼15 dB for the second mode.

Microstructural changes associated with osteoporosis negatively affect loading-induced fluid flow around osteocytes in cortical bone

Loading-induced interstitial fluid flow in the microporosities of bone is critical for osteocyte mechanotransduction and for the maintenance of tissue health, enhancing convective transport in the lacunar-canalicular system. In recent studies, our group has reported alterations of bone’s vascular porosity and lacunar-canalicular system microarchitecture in a rat model of postmenopausal osteoporosis. In this work, poroelastic finite element analysis was used to investigate whether these microstructural changes can affect interstitial fluid flow around osteocytes. Animal-specific finite element models were developed combining micro-CT reconstructions of bone microstructure and measures of the poroelastic material properties. These models were used to quantify and compare loading-induced fluid flow in the lacunar-canalicular system of ovariectomized and sham-operated rats. A parametric analysis was also used to quantify the influence of the lacunar-canalicular permeability and vascular porosity on the fluid velocity magnitude. Results show that mechanically-induced interstitial fluid velocity can be significantly reduced in the lacunar-canalicular system of ovariectomized rats. Interestingly, the vascular porosity is shown to have a major influence on interstitial fluid flow, while the lacunar-canalicular permeability influence is limited when larger than 10-20m2. Altogether our results suggest that microstructural changes associated with the osteoporotic condition can negatively affect interstitial fluid flow around osteocytes in the lacunar-canalicular system of cortical bone. This fluid flow reduction could impair mechanosensation of the osteocytic network, possibly playing a role in the initiation and progression of age-related bone loss and postmenopausal osteoporosis.

Stress behavior in the near fracture region between adjacent horizontal wells during multistage fracturing using a coupled stress-displacement to hydraulic diffusivity model

This work presents results for the application of finite element simulation to determine changes in stress orientation and magnitude during a multistage fracturing job in horizontal wellbores. A technique that couples stress-displacement with hydraulic diffusivity was used to account for effective in-situ stress and to estimate pore pressure distribution in the near fracture region. The results captured in this study aid understanding of propagation of induced fractures in a multistage fracturing job and in a multiple horizontal wellbore scenario. This study is a valid and reliable estimation of effective stresses in the near fracture area because effective stresses control strain in a saturated poroelastic material. Additionally, reorientation of in-situ stress in the same near region to the fracture was confirmed. The local reorientation of in-situ stresses will consequently cause the reorientation of subsequent fractures which will stop growing transverse to the horizontal wellbore. As a result, induced fractures do not propagate as expected, creating a non-efficient drainage pattern in the reservoir.

Inverse poroelasticity as a fundamental mechanism in biomechanics and mechanobiology

Understanding the mechanisms of deformation of biological materials is important for improved diagnosis and therapy, fundamental investigations in mechanobiology, and applications in tissue engineering. Here we demonstrate the essential role of interstitial fluid mobility in determining the mechanical properties of soft tissues. Opposite to the behavior expected for a poroelastic material, the tissue volume of different collagenous membranes is observed to strongly decrease with tensile loading. Inverse poroelasticity governs monotonic and cyclic responses of soft biomembranes, and induces chemo-mechanical coupling, such that tensile forces are modulated by the chemical potential of the interstitial fluid. Correspondingly, the osmotic pressure varies with mechanical loads, thus providing an effective mechanism for mechanotransduction. Water mobility determines the tissue’s ability to adapt to deformation through compaction and dilation of the collagen fiber network. In the near field of defects this mechanism activates the reversible formation of reinforcing collagen structures which effectively avoid propagation of cracks.

Simulation of guided waves in layered fluid/viscoelastic/poroelastic media using semi-analytical finite element method

Understanding of the ultrasound transmission in functionally graded structures materials is of great interest in many engineering applications such as geophysics, biomedical diagnostics, aircraft, and automobile. This paper will present a computational method and its implementation procedure to study the wave propagation problem in multilayer structures made from a combination of fluid, anisotropic viscoelastic, and poroelastic materials. The poroelastic material is described by using the Biot theory. The developed approach is based on the Semi-analytical Finite Element Method (SAFE), which only requires the discretization of the cross-section of the structure. For the finite element solver, high-order spectral element has been used, showing a significant improvement of the computational efficiency compared to the use of conventional high-order elements. Numeral validation in both time and frequency domains show that the proposed approach is efficient to investigate the transient response as well as the dispersion of layered media. Some results in the context of quantitative ultrasound axial transmission techniques for assessing properties of cortical long bones will also be presented.

A parametric model order reduction technique for poroelastic finite element models.

This research presents a parametric model order reduction approach for vibro-acoustic problems in the frequency domain of systems containing poroelastic materials (PEM). The method is applied to the Finite Element (FE) discretization of the weak u-p integral formulation based on the Biot-Allard theory and makes use of reduced basis (RB) methods typically employed for parametric problems. The parametric reduction is obtained rewriting the Biot-Allard FE equations for poroelastic materials using an affine representation of the frequency (therefore allowing for RB methods) and projecting the frequency-dependent PEM system on a global reduced order basis generated with the proper orthogonal decomposition instead of standard modal approaches. This has proven to be better suited to describe the nonlinear frequency dependence and the strong coupling introduced by damping. The methodology presented is tested on two three-dimensional systems: in the first experiment, the surface impedance of a PEM layer sample is calculated and compared with results of the literature; in the second, the reduced order model of a multilayer system coupled to an air cavity is assessed and the results are compared to those of the reference FE model.

On the numerical investigation of sound transmission through double-walled structures with membrane-type acoustic metamaterials.

Acoustic metamaterials appear to be of great help in the design of reliable and effective noise reduction measures in the low frequency range. The current contribution is concerned with the modeling of a low-frequency noise shield, based on a double wall arrangement, which includes membrane-type acoustic metamaterials (MAMs), considered as the most promising approach when it comes especially to the tonal noise at frequencies below 300 Hz. MAMs consist of small-sized membranes loaded with a mass. Due to their robustness and relatively simple production, MAMs have been proven to decrease the sound transmission in frequency ranges, for which poro-elastic materials have a rather negligible effect. A simulation model of a double wall panel, whose acoustic cavity is furnished with layers of metamaterials, has been developed and the sound transmission loss (STL) through the structure was calculated, using the finite element method. In order to validate the modelling approach, the STL estimation from the finite element analysis was compared to experimental measurements. The achieved results indicate a noise-decreasing possibility in tunable narrow bands as well as a broadband noise reduction for frequencies less than 300 Hz without significantly adding to the panel mass.

An investigation into the contact between soft elastic and poroelastic bodies rotating under load

This paper explores the contact of soft elastic and poroelastic bodies rotating under load and inspects the differences in load carrying capacity between the two types of material. Both materials have been widely used to describe the behaviour of biological systems such as articular cartilage in mammalian joints, however, we demonstrate here that there are fundamental differences between the responses generated in which the poroelastic response has an additional fluid contribution to the solid structural response. In order to produce the same load carrying capacity it is shown that the poroelastic material must deform more than an incompressible soft elastic material with the same stiffness and that the solid load generated by a poroelastic material is the same as a soft elastic material with a zero Poisson’s ratio.

Acoustics of permeo-elastic materials

In the dynamics of Biot poroelastic materials, the fluid flow is not affected by the deformation of the solid elastic frame. In contrast, in permeable materials whose solid stiff frames have flexible thin flat films attached, i.e. permeo-elastic materials, the fluid flow can be significantly modified by the presence of the films. As a consequence of the local fluid–film interaction, and in particular of the local resonances, the classical local physics is changed and departs from that leading to the Biot description. In this paper, the two-scale asymptotic homogenisation method is used to derive the macroscopic description of sound propagation in air-saturated permeo-elastic materials. This description is asymptotically analysed to determine the conditions for which the geometrical and mechanical properties of the films strongly affect the effective properties of the material. The developed theory is illustrated numerically and validated experimentally for a prototype material, evidencing the atypical acoustic behaviour.

Mechanical characterization of compressible chromatographic particles

During operation of packed-bed chromatography columns, the mechanical properties of the porous chromatographic particles determine the overall macroscopic compression behavior. The porous particles are biphasic materials consisting of a solid matrix and interstitial fluid. Mechanical characterization of selected arrays of two types of polymeric chromatographic particles made of agarose and methacrylate with a mean particle diameter of 60μm and 83μm, respectively, was carried out by applying a high-resolution micromanipulation technique. The effect of compression speed and displacement level was investigated. Both particle types showed pronounced time-dependent compression behavior and force relaxation. Long-time compression load relaxation experiments revealed that two different time-dependent mechanisms were involved. It was shown that the characteristic force relaxation times describing either mechanism differed by a factor of 13–31. Short-time quasistatic compression experiments were excellently described by a Maxwell-type standard linear solid model in which the force relaxation time matched the shorter relaxation time. It was assumed, that force relaxation occurring at short time is ascribed to poroelastic material behavior and at longer times to viscoelastic material behavior. This enabled the determination of fundamental particle properties, i.e. instantaneous and relaxed particle shear and Young's moduli, Poisson's ratio, and coefficient of restitution.

External mean flow influence on sound transmission through finite clamped double-wall sandwich panels

This paper studies the influence of an external mean flow on the sound transmission through finite clamped double-wall sandwich panels lined with poroelastic materials. Biot's theory is employed to describe wave propagation in poroelastic materials and various configurations of coupling the poroelastic layer to the facing plates are considered. The clamped boundary of finite panels are dealt with by the modal superposition theory and the weighted residual (Garlekin) method, leading to a matrix equation solution for the sound transmission loss (STL) through the structure. The theoretical model is validated against existing theories of infinite sandwich panels with and without an external flow. The numerical results of a single incident wave show that the external mean flow has significant effects on the STL which are coupled with the clamped boundary effect dominating in the low-frequency range. The external mean flow also influences considerably the limiting incidence angle of the panel system and the effect of the incidence angle on the STL. However, the influences of the azimuthal angle and the external flow orientation are negligible.

Acoustic properties of double-porosity granular polymers

Using an extension of the full elastodynamic layer-multiple-scattering method to structures of fluid-saturated poroelastic spherical bodies, a comprehensive theoretical study of the acoustic response of double-porosity submerged liquid-saturated granular polymeric materials of specific morphology consisting of touching porous polymer spheres arranged in a fcc lattice, beyond the long-wavelength effective-medium description, is presented. Calculated transmission and absorption spectra of finite slabs of these materials are analyzed by reference to the acoustic modes of the constituent porous spherical grains as well as to relevant dispersion diagrams of corresponding infinite crystals, and a consistent interpretation of the results is provided. In particular, it is shown that resonant modes with very long lifetime, localized in the spheres in the form of slow longitudinal waves, which are peculiar to poroelastic materials, are formed when the viscous length is much shorter than the radius of the inner pores of the spheres. These modes, which can be easily tuned in frequency by adjusting the intrinsic porosity of the spheres, induce some remarkable features in the acoustic behavior of these double-porosity materials, such as narrow dispersionless absorption bands and directional transmission gaps.

Influence of pore water in the seabed on dynamic response of offshore wind turbines on monopiles

The well-known p-y curve method provides soil-structure interaction that does not account for the pore pressure effect for dynamic analysis of offshore wind turbines (OWTs). In order to avoid overly conservative designs, reliable estimates of the dynamic response should be taken into account. The turbine is introduced using a simplified model to assess the eigenfrequencies and modal damping, accounting for pore water flow and excess pore pressure around the monopile. Thus the effect of pore pressure and load frequency are illustrated by implementing a poroelastic model to present more realistic dynamic properties and compare them with results obtained by the p-y curve method. A cyclic loading is considered and the soil stiffness based on the Winkler and Kelvin models is calculated and compared while the soil damping for the Kelvin model is computed. Developed finite element programs are employed to present the results for a two-phase system consisting of a solid skeleton and pore fluid, based on the u-P formulation. Here, u is grain displacement and P is pore water pressure. The developed codes have been validated with commercial software and are implemented to perform free vibration tests to evaluate the eigenfrequencies. A linear poroelastic material model is utilized. An equivalent masses-dashpots-springs system at the pile-cap level is calculated and compared by using Winkler and Kelvin models to highlight the effect of pore pressure and load seepage damping.

Tailoring broadband acoustic energy suppression characteristics of double porosity metamaterials with compression constraints and mass inclusions.

A metamaterial that capitalizes on a double porosity architecture is introduced for controlling broadband acoustic energy suppression properties. When the metamaterial is subjected to static compressive stress, a global rotation of the internal metamaterial architecture is induced that softens the effective stiffness and results in a considerable means to tailor wave transmission and absorption properties. The influences of mass inclusions and compression constraints are examined by computational and experimental efforts. The results indicate that the mass inclusions and applied constraints can significantly impact the absorption and transmission properties of double porosity metamaterials, while the appropriate utilization of the underlying poroelastic media can further magnify these parametric influences. Based on the widespread implementation of compressed poroelastic media in applications, the results of this research uncover how internal metamaterial architecture and constraints may be exploited to enhance engineering noise control properties while using less poroelastic material mass.

Closed-Form Analytical Solution for Vibrations from a Tunnel Embedded in a Saturated Poroelastic Half-Space

A closed-form analytical solution for ground-borne vibrations from a tunnel embedded in a saturated poroelastic half-space is proposed in this paper. The tunnel modeled as an elastic hollow cylinder is surrounded by the water-saturated poroelastic material. The total wave field in the poroelastic half-space with a cylindrical cavity consists of the outgoing cylindrical waves and the down-going plane waves. In addition to the traction-free condition on the ground surface and the continuous conditions of displacement and stress at the tunnel-soil interface, hydraulic boundary conditions on these two scattering surfaces are required to solve this multiple-scattering problem. The transformation properties between the plane and cylindrical wave functions are employed to apply the boundary conditions expressed in both the rectangular and cylindrical coordinate systems. Numerical results for the displacements of the solid on the ground surface and the pore pressure in the saturated soil attributable to a harmonic point load applied at the tunnel invert are presented. The influence of the soil permeability and the hydraulic boundary at the tunnel-soil interface on the free-field responses is investigated. The proposed solution can serve as a benchmark for other computational methods and as an efficient tool for predicting vibrations from a tunnel embedded in a saturated poroelastic half-space.