This is the first research on the vibrational analysis of functionally graded graphene platelets reinforced composite (FG-GPLRC) viscoelastic annular plate within the framework of higher order shear ...deformation theory (HSDT). Hamilton's principle is employed to establish governing equations of motion within the framework of HSDT. In this article, viscoelastic properties are modeled according to Kelvin-Voigt viscoelasticity. The deflection as the function of time can be solved by the fourth-order Runge-Kutta numerical method. Generalized differential quadrature method is applied to obtain numerical solution. Numerical results are compared with those published in the literature to examine the accuracy and validity of the applied approach. A comprehensive parametric study is accomplished to reveal the influence of viscoelasticity coefficient, weight fraction, boundary conditions, and distribution patterns of GPLs on the frequency response of the structure. The results revealed that applying locating more square shaped GPLs in the vicinity of the top and bottom surface results into the highest natural frequency. Another important consequence is that FG-GPLRC structure with FG-V, FG-A, and UD patterns have similar effect on the natural frequency of the GPLRC annular plate while FG-X has the best stability and natural frequency. A useful suggestion of this research is that, increasing the value of the length to thickness ratio of GPL not only decreases the central deflection of the structure through time, but also causes to decrease real time domain changes for the FG-GPLRC viscoelastic annular plate.
Full text
Available for:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
This is the first research on the free vibration analysis of functionally graded graphene platelets reinforced composite (FG-GPLRC) viscoelastic annular plate resting on the visco-Pasternak ...foundation and subjected to the nonlinear temperature gradient and mechanical loading within the framework of higher-order shear deformation theory (HSDT). Hamilton's principle is employed to establish governing equations within the framework of HSDT. In this paper, viscoelastic properties are modeled according to Kelvin-Voigt viscoelasticity. The deflection as the function of time can be solved by the fourth-order Runge-Kutta numerical method. Generalized differential quadrature method (GDQM) is applied to obtain a numerical solution. Numerical results are compared with those published in the literature to examine the accuracy and validity of the applied approach. A comprehensive parametric study is accomplished to reveal the influence of the stiffness of the substrate, patterns of temperature rise, axial load, damper and viscoelasticity coefficient, weight fraction and distribution patterns of GPLs and geometric dimensions of GPLs on the frequency response of the structure. The results revealed that applying sinusoidal temperature rise and locating more square-shaped GPLs in the vicinity of the top and bottom surfaces have important effect of the highest natural frequency and buckling load of the FG-GPLRC viscoelastic structure.
•Free vibration analysis of FG-GPLRC viscoelastic annular plate is investigated.•The effects of the nonlinear temperature gradient and mechanical load is considered.•Hamilton's principle is employed to establish governing equations of motion within the framework of HSDT.•Viscoelastic properties are modeled according to Kelvin-Voigt viscoelasticity.•The deflection as the function of time can be solved by the fourth-order Runge-Kutta numerical method.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The mechanical properties of extracellular matrices can control the function of cells. Studies of cellular responses to biomimetic soft materials have been largely restricted to hydrogels and ...elastomers that have stiffness values independent of time and extent of deformation, so the substrate stiffness can be unambiguously related to its effect on cells. Real tissues, however, often have loss moduli that are 10 to 20% of their elastic moduli and behave as viscoelastic solids. The response of cells to a time-dependent viscous loss is largely uncharacterized because appropriate viscoelastic materials are lacking for quantitative studies. Here we report the synthesis of soft viscoelastic solids in which the elastic and viscous moduli can be independently tuned to produce gels with viscoelastic properties that closely resemble those of soft tissues. Systematic alteration of the hydrogel viscosity demonstrates the time dependence of cellular mechanosensing and the influence of viscous dissipation on cell phenotype.
There is growing interest in voxelated matter that is designed and fabricated voxel by voxel
. Currently, inkjet-based three-dimensional (3D) printing is the only widely adopted method that is ...capable of creating 3D voxelated materials with high precision
, but the physics of droplet formation requires the use of low-viscosity inks to ensure successful printing
. By contrast, direct ink writing, an extrusion-based 3D printing method, is capable of patterning a much broader range of materials
. However, it is difficult to generate multimaterial voxelated matter by extruding monolithic cylindrical filaments in a layer-by-layer manner. Here we report the design and fabrication of voxelated soft matter using multimaterial multinozzle 3D (MM3D) printing, in which the composition, function and structure of the materials are programmed at the voxel scale. Our MM3D printheads exploit the diode-like behaviour that arises when multiple viscoelastic materials converge at a junction to enable seamless, high-frequency switching between up to eight different materials to create voxels with a volume approaching that of the nozzle diameter cubed. As exemplars, we fabricate a Miura origami pattern
and a millipede-like soft robot that locomotes by co-printing multiple epoxy and silicone elastomer inks of stiffness varying by several orders of magnitude. Our method substantially broadens the palette of voxelated materials that can be designed and manufactured in complex motifs.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The Acoustic Black Hole (ABH) is a technique for passive vibration control that was recently developed within the Structural Dynamics and Vibroacoustics communities. From a general perspective, the ...ABH effect is achieved by embedding a local inhomogeneity in a thin-walled structure, typically a beam or a plate. This inhomogeneity is characterized by a variation of the geometric properties (although material variations are also possible) according to a spatial power law profile. The combination of a local stiffness reduction, due to the power law variation of the wall thickness, and of a local increase in damping, provided by the concurrent application of viscoelastic layers, gives rise to a significant reduction of the wave speed and to a remarkable enhancement of the attenuation properties. As an elastic wave travels within an ABH, its speed experiences a smooth and continuous decrease. In the ideal case, that is when the wall thickness vanishes at the ABH center, the wave speed decreases to zero. In the non-ideal case, that is when the ABH has a non-zero residual thickness at its center, the wave speed still decreases smoothly but it never vanishes. In this latter case, which is of great importance for practical applications, the ABH is typically combined with lossy media (e.g. viscoelastic layers) in order to achieve significantly enhanced structural loss factors. If the speed of an incoming wave can vanish inside the ABH, it follows that this object behaves as a wave trap that extracts elastic energy from the host medium without, in principle, ever releasing it. Several characteristic properties are generally observed in structures with embedded ABHs: significant reduction in vibration and acoustic radiation levels, low reflection coefficient at the ABH location, localized vibration and trapped modes, and existence of cut-on frequencies. Contrarily to passive vibration methods based on viscoelastic materials, the ABH was developed and applied to reduce vibrations and structure-radiated noise without increasing the total mass of the system. More recently, applications to other areas including elastic metastructures, energy harvesting, vibro-impact systems, and cochlear systems were also investigated. This review is intended to provide a comprehensive summary of the state-of-the-art of ABH technology, spanning from theoretical and numerical contributions to practical applications.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Living cells are viscoelastic materials, with the elastic response dominating at long timescales (≳1 ms)1. At shorter timescales, the dynamics of individual cytoskeleton filaments are expected to ...emerge, but active microrheology measurements on cells accessing this regime are scarce2. Here, we develop high-frequency microrheology (HF-MR) to probe the viscoelastic response of living cells from 1Hz to 100 kHz. We report the viscoelasticity of different cell types and upon cytoskeletal drug treatments. At previously inaccessible short timescales, cells exhibit rich viscoelastic responses that depend on the state of the cytoskeleton. Benign and malignant cancer cells revealed remarkably different scaling laws at high frequency, providing a univocal mechanical fingerprint. Microrheology over a wide dynamic range up to the frequency of action of the molecular components provides a mechanistic understanding of cell mechanics.
Full text
Available for:
IJS, NUK, SBMB, UL, UM, UPUK
We investigate a novel category of Caputo fractional Moreau's sweeping process, formulated in a real Hilbert space, by the inclusion below−Dtα0cu(t)∈NΞ(t)(A(Dtα0cu(t))+Bu(t)). Our primary focus is to ...develop a framework for proving the unique solvability of the fractional Moreau's sweeping processes, namely, we deliver a fractional version of the Moreau's type catching-up algorithm for the sweeping process being considered. Moreover, the established abstract results are applied to investigate a complicated dynamical viscoelastic contact problem with fractional constitutive laws.
•A novel category of Caputo fractional Moreau's sweeping process is considered.•The unique solvability of Caputo fractional Moreau's sweeping process is obtained.•A complicated dynamical viscoelastic contact problem with fractional constitutive laws is studied.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Living tissues are non-linearly elastic materials that exhibit viscoelasticity and plasticity. Man-made, implantable bioelectronic arrays mainly rely on rigid or elastic encapsulation materials and ...stiff films of ductile metals that can be manipulated with microscopic precision to offer reliable electrical properties. In this study, we have engineered a surface microelectrode array that replaces the traditional encapsulation and conductive components with viscoelastic materials. Our array overcomes previous limitations in matching the stiffness and relaxation behaviour of soft biological tissues by using hydrogels as the outer layers. We have introduced a hydrogel-based conductor made from an ionically conductive alginate matrix enhanced with carbon nanomaterials, which provide electrical percolation even at low loading fractions. Our combination of conducting and insulating viscoelastic materials, with top-down manufacturing, allows for the fabrication of electrode arrays compatible with standard electrophysiology platforms. Our arrays intimately conform to the convoluted surface of the heart or brain cortex and offer promising bioengineering applications for recording and stimulation.
Full text
Available for:
GEOZS, IJS, IMTLJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBMB, UL, UM, UPUK, ZAGLJ
The rapid development of additive manufacturing techniques, also known as three‐dimensional (3D) printing, is driving innovations in polymer chemistry, materials science, and engineering. Among ...current 3D printing techniques, direct ink writing (DIW) employs viscoelastic materials as inks, which are capable of constructing sophisticated 3D architectures at ambient conditions. In this perspective, polymer designs that meet the rheological requirements for direct ink writing are outlined and successful examples are summarized, which include the development of polymer micelles, co‐assembled hydrogels, supramolecularly cross‐linked systems, polymer liquids with microcrystalline domains, and hydrogels with dynamic covalent cross‐links. Furthermore, advanced polymer designs that reinforce the mechanical properties of these 3D printing materials, as well as the integration of functional moieties to these materials are discussed to inspire new polymer designs for direct ink writing and broadly 3D printing.
New ink: Polymer designs for direct ink writing are outlined, with emphasis on strategies aimed at fulfilling the rheological requirements, reinforcing the mechanical properties, and integrating functional moieties (see figure).
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
PDF
