Showing papers on "Elasticity (economics) published in 2017"
TL;DR: In this paper, it is shown that the existence of a solution of nonlocal beam elastostatic problems is an exception, the rule being non-existence for problems of applicative interest.
405 citations
TL;DR: The authors quantitatively summarizes the recent, but sizeable, empirical evidence to facilitate a sounder economic assessment of (in some cases, policy-related) energy price changes, using meta-analysis to identify the main factors affecting short and long term elasticity results for energy, in general, as well as for specific products.
328 citations
TL;DR: It is clear from numerous in vitro and in vivo studies that particle elasticity is an important parameter that can be leveraged to improve blood circulation, tissue targeting, and specific interactions with cells.
284 citations
TL;DR: In this paper, a triaxial test was proposed for determining the deformation anisotropy of sedimentary and metamorphic rocks by using a single specimen sampled from an arbitrary direction.
Abstract: A novel method is proposed for determining the deformation anisotropy of rocks by a single triaxial test using a single specimen sampled from an arbitrary direction. Transversely isotropic elasticity is assumed for the purpose of application of the test method to sedimentary and metamorphic rocks, and the non-axial symmetric stress–strain relationships of anisotropic rocks are determined by triaxial testing by means of a simple improvement to the cap in the triaxial testing apparatus. Both the elastic parameters and the directions of the transversely isotropic elasticity can be obtained by measuring the shear deformations that occur under triaxial stress conditions. An overview of the method for determining transversely isotropic elasticity is presented in this paper, along with the results of a sensitivity analysis performed assuming simulated strains with random measurement errors. The results show that the directions of anisotropy can be determined precisely using the directions of the principal strains measured during isotropic compression and that the elastic parameters can be determined uniquely from the stress–strain relationships observed during both the isotropic and axial compression processes.
174 citations
TL;DR: A critical evaluation of the characterization techniques and methodologies for the characterization and understanding of the mechanical properties of nanowires, including elasticity, plasticity, anelasticity and strength were presented.
Abstract: Applications of nanowires into future generation nanodevices require a complete understanding of the mechanical properties of the nanowires. A great research effort has been made in the past two decades to understand the deformation physics and mechanical behaviors of nanowires, and to interpret the discrepancies between experimental measurements and theoretical predictions. This review focused on the characterization and understanding of the mechanical properties of nanowires, including elasticity, plasticity, anelasticity and strength. As the results from the previous literature in this area appear inconsistent, a critical evaluation of the characterization techniques and methodologies were presented. In particular, the size effects of nanowires on the mechanical properties and their deformation mechanisms were discussed.
140 citations
TL;DR: The behaviour of conventional pile groups (e.g. closely spaced) that are subjected to mechanical loads has been shown to be different from the behaviour of single isolated piles.
Abstract: The behaviour of conventional pile groups (e.g. closely spaced) that are subjected to mechanical loads has been shown to be different from the behaviour of single isolated piles. The so-called ‘gro...
116 citations
TL;DR: In this paper, the elastostatic problem of a Bernoulli-Euler functionally graded nanobeam is formulated by adopting stress-driven nonlocal elasticity theory, recently proposed by G. Romano and R. Barretta.
Abstract: The elastostatic problem of a Bernoulli-Euler functionally graded nanobeam is formulated by adopting stress-driven nonlocal elasticity theory, recently proposed by G. Romano and R. Barretta. According to this model, elastic bending curvature is got by convoluting bending moment interaction with an attenuation function. The stress-driven integral relation is equivalent to a differential problem with higher-order homogeneous constitutive boundary conditions, when the special bi-exponential kernel introduced by Helmholtz is considered. Simple solution procedures, based on integral and differential formulations, are illustrated in detail to establish the exact expressions of nonlocal transverse displacements of inflected nano-beams of technical interest. It is also shown that all the considered nano-beams have no solution if Eringen's strain-driven integral model is adopted. The solutions of the stress-driven integral method indicate that the stiffness of nanobeams increases at smaller scales due to size effects. Local solutions are obtained as limit of the nonlocal ones when the characteristic length tends to zero.
98 citations
TL;DR: A low-order Virtual Element Method with a priori symmetric stresses is proposed for 2D elasticity problems, in the framework of the small strain theory and in connection with the mixed Hellinger–Reissner variational formulation.
96 citations
TL;DR: In this article, a superhydrophobic graphene-based porous monolith with high elasticity was proposed for the absorption of oil contaminations from water and its fabrication was facile.
Abstract: Superhydrophobicity and high elasticity are the two key properties of oil-absorption porous materials. The hydrophobic graphene/carbon black coating on the skeleton of a melamine sponge facilitated the surface to form the micro/nanoscale roughness. The resulting sponge thus was superhydrophobic. Moreover, it inherited the extremely high elasticity of raw melamine sponge, which showed no plastic deformation even after 1000 compression/relaxing cycles. To our knowledge, this was the first superhydrophobic graphene-based porous monolith with such a high elasticity. Its absorbed oils could be recycled by simple squeezing and it was also regenerated by squeezing because of the high elasticity. In addition, it showed a high absorption capacity for common oil contaminations and its fabrication was facile. Therefore, it is really an excellent absorbent for the practical absorption of oil contaminations from water.
73 citations
TL;DR: In this paper, a general bi-Helmholtz nonlocal strain-gradient elasticity model is developed for wave dispersion analysis of porous double-nanobeam systems on elastic substrate.
70 citations
TL;DR: By using magnetic tweezers, it is found that the titin I27 domain unfolds in a surprising non-monotonic force-dependent manner at forces smaller than 100’pN, with the slowest unfolding rate occurring around 22 pN.
Abstract: The giant protein titin plays a critical role in regulating the passive elasticity of muscles, mainly through the stochastic unfolding and refolding of its numerous immunoglobulin domains in the I-band of sarcomeres. The unfolding dynamics of titin immunoglobulin domains at a force range greater than 100 pN has been studied by atomic force microscopy, while that at smaller physiological forces has not been measured before. By using magnetic tweezers, it is found that the titin I27 domain unfolds in a surprising non-monotonic force-dependent manner at forces smaller than 100 pN, with the slowest unfolding rate occurring around 22 pN. We further demonstrate that a model with single unfolding pathway taking into account the elasticity of the transition state can reproduce the experimental results. These results provide important novel insights into the regulation mechanism of the passive elasticity of muscle tissues.
TL;DR: In isogeometric analysis of higher-order strain gradient elasticity by user element implementations within a commercial finite element software Abaqus, the convergence properties of the method in the energy norm are shown to be optimal with respect to the NURBS order of the discretizations.
Abstract: This article is devoted to isogeometric analysis of higher-order strain gradient elasticity by user element implementations within a commercial finite element software Abaqus. The sixth-order boundary value problems of four parameter second strain gradient-elastic bar and plane strain/stress models are formulated in a variational form within an H 3 Sobolev space setting. These formulations can be reduced to two parameter first strain gradient-elastic problems of H 2 variational forms. The implementations of the isogeometric C 2 - and C 1 -continuous Galerkin methods, for the second and first strain gradient elasticity, respectively, are verified by a series of benchmark problems. With the first benchmark problem, a clamped bar in static tension, the convergence properties of the method in the energy norm are shown to be optimal with respect to the NURBS order of the discretizations. For the second benchmark, a clamped bar in extensional free vibrations, the analytical frequencies are captured by the numerical results within the classical and the first strain gradient elasticity. With three examples for the plane stress/strain elasticity, the convergence properties are shown to be optimal, the stress fields of different models are compared to each other, and the differences between the eigenfrequencies and eigenmodes of the models are analyzed. The last example, the Kraus problem, analyses the stress concentration factors within the different models.
TL;DR: In this article, it was shown that any well-behaved demand function can be represented by its demand manifold, a smooth curve that relates the elasticity and convexity of demand.
Abstract: We show that any well-behaved demand function can be represented by its “demand manifold,” a smooth curve that relates the elasticity and convexity of demand. This manifold is a sufficient...
TL;DR: Simplified isotropic models of strain gradient elasticity are presented, based on the mutual relationship between the inherent (dual) gradient directions (i.e. the gradient direction of any strain gradient source and the lever arm direction of the promoted double stress) as discussed by the authors.
Abstract: Simplified isotropic models of strain gradient elasticity are presented, based on the mutual relationship between the inherent (dual) gradient directions (i.e. the gradient direction of any strain gradient source and the lever arm direction of the promoted double stress). A class of gradient-symmetric materials featured by gradient directions obeying a reciprocity relation and by 4 independent h.o. (higher order) coefficients is envisioned, along with the sub-classes of hemi-collinear materials (3 h.o. coefficients, gradient directions in part coincident), collinear materials (2 h.o. coefficients, equal gradient directions) and micro-affine materials (1 h.o. coefficient, behavioral affinity at micro- and macro-scale, coincident with the Aifantis model). All models comply with the energy positive definiteness conditions. The boundary-value problem for the wide class of gradient-symmetric materials is governed by a set of Poisson–Helmholtz type differential equations almost unaffected by the number of independent h.o. coefficients; instead the boundary conditions carry in, in general, problem-dependent computational difficulties increasing with the number of these coefficients. As an application, gradient-symmetric beam models are discussed. A parallel hierarchy of simplified isotropic models with couple stresses is also presented, in which the novel concept of rotational volumetric strain gradient is exploited. A graphical overview on isotropic strain gradient elasticity models is reported. An Appendix is devoted to the concepts of extensional and rotational volumetric strain gradients and to the related pressure-like stresses.
TL;DR: In this paper, no field data referring to various operating energy piles over timescales of practical geothermal applications have been made available to investigate the thermally induced "group action" phenomenon.
Abstract: To date, no field data referring to various operating energy piles over timescales of practical geothermal applications have been made available to investigate the thermally induced ‘group action’....
TL;DR: In this paper, the relationship between drag reduction and fluid elasticity was explored by exploiting the mechanical degradation of polymer molecules to vary their rheological properties, and a plot of turbulent drag reduction against Weissenberg number was found to approximately collapse the data, with the onset of DR occurring at and the maximum drag reduction asymptote being approached for.
Abstract: In this study, we experimentally investigate the turbulent drag-reduction (DR) mechanism in flow through ducts of circular, rectangular and square cross-sections using two grades of polyacrylamide in aqueous solution having different molecular weights and various semidilute concentrations. Specifically, we explore the relationship between drag reduction and fluid elasticity, purposely exploiting the mechanical degradation of polymer molecules to vary their rheological properties. We also obtain time-resolved velocity data for various DR levels using particle image velocimetry and laser Doppler velocimetry. Elasticity is quantified via relaxation times determined from uniaxial extensional flow using a capillary breakup apparatus. A plot of DR against Weissenberg number ( ) is found to approximately collapse the data, with the onset of DR occurring at and the maximum drag-reduction asymptote being approached for . Thus quantitative predictions of DR in a range of shear flows can be made from a single measurable material property of a polymer solution, at least for this particular flexible linear polymer.
TL;DR: An actively deforming model of a jellyfish immersed in a viscous fluid is developed and numerical simulations are used to study the role of active muscle contraction, passive body elasticity and fluid forces in the medusan mechanospace to quantify how these active and passive properties affect swimming speed and cost of transport.
Abstract: In many swimming and flying animals, propulsion emerges from the interplay of active muscle contraction, passive body elasticity and fluid–body interaction. Changes in the active and passive body properties can influence performance and cost of transport across a broad range of scales; they specifically affect the vortex generation that is crucial for effective swimming at higher Reynolds numbers. Theoretical models that account for both active contraction and passive elasticity are needed to understand how animals tune both their active and passive properties to move efficiently through fluids. This is particularly significant when one considers the phylogenetic constraints on the jellyfish mechanospace, such as the presence of relatively weak muscles that are only one cell layer thick. In this work, we develop an actively deforming model of a jellyfish immersed in a viscous fluid and use numerical simulations to study the role of active muscle contraction, passive body elasticity and fluid forces in the medusan mechanospace. By varying the strength of contraction and the flexibility of the bell margin, we quantify how these active and passive properties affect swimming speed and cost of transport. We find that for fixed bell elasticity, swimming speed increases with the strength of contraction. For fixed force of contractility, swimming speed increases as margin elasticity decreases. Varying the strength of activation in proportion to the elasticity of the bell margin yields similar swimming speeds, with a cost of transport is substantially reduced for more flexible margins. A scaling study reveals that performance declines as the Reynolds number decreases. Circulation analysis of the starting and stopping vortex rings showed that their strengths were dependent on the relative strength of activation with respect to the bell margin flexibility. This work yields a computational framework for developing a quantitative understanding of the roles of active and passive body properties in swimming.
TL;DR: In this article, the authors studied the transition to turbulence in dilute polymeric channel flow using direct numerical simulations of a FENE-P fluid and compared it to a reference Newtonian configuration.
Abstract: Orderly, or natural, transition to turbulence in dilute polymeric channel flow is studied using direct numerical simulations of a FENE-P fluid. Three Weissenberg numbers are simulated and contrasted to a reference Newtonian configuration. The computations start from infinitesimally small Tollmien–Schlichting (TS) waves and track the development of the instability from the early linear stages through nonlinear amplification, secondary instability and full breakdown to turbulence. At the lowest elasticity, the primary TS wave is more unstable than the Newtonian counterpart, and its secondary instability involves the generation of -structures which are narrower in the span. These subsequently lead to the formation of hairpin packets and ultimately breakdown to turbulence. Despite the destabilizing influence of weak elasticity, and the resulting early transition to turbulence, the final state is a drag-reduced turbulent flow. At the intermediate elasticity, the growth rate of the primary TS wave matches the Newtonian value. However, unlike the Newtonian instability mode which reaches a saturated equilibrium condition, the instability in the polymeric flow reaches a periodic state where its energy undergoes cyclical amplification and decay. The spanwise size of the secondary instability in this case is commensurate with the Newtonian -structures, and the extent of drag reduction in the final turbulent state is enhanced relative to the lower elasticity condition. At the highest elasticity, the exponential growth rate of the TS wave is weaker than the Newtonian flow and, as a result, the early linear stage is prolonged. In addition, the magnitude of the saturated TS wave is appreciably lower than the other conditions. The secondary instability is also much wider in the span, with weaker ejection and without hairpin packets. Instead, streamwise-elongated streaks are formed and break down to turbulence via secondary instability. The final state is a high-drag-reduction flow, which approaches the Virk asymptote.
TL;DR: In this paper, a modified worm-like chain model incorporating an internal electrostatic tension was proposed to understand the conformational ensemble of flexible polyelectrolytes, such as single-stranded nucleic acids (ssNAs).
Abstract: Understanding of the conformational ensemble of flexible polyelectrolytes, such as single-stranded nucleic acids (ssNAs), is complicated by the interplay of chain backbone entropy and salt-dependent electrostatic repulsions. Molecular elasticity measurements are sensitive probes of the statistical conformation of polymers and have elucidated ssNA conformation at low force, where electrostatic repulsion leads to a strong excluded volume effect, and at high force, where details of the backbone structure become important. Here, we report measurements of ssDNA and ssRNA elasticity in the intermediate-force regime, corresponding to 5- to 100-pN forces and 50-85% extension. These data are explained by a modified wormlike chain model incorporating an internal electrostatic tension. Fits to the elastic data show that the internal tension decreases with salt, from [Formula: see text]5 pN under 5 mM ionic strength to near zero at 1 M. This decrease is quantitatively described by an analytical model of electrostatic screening that ascribes to the polymer an effective charge density that is independent of force and salt. Our results thus connect microscopic chain physics to elasticity and structure at intermediate scales and provide a framework for understanding flexible polyelectrolyte elasticity across a broad range of relative extensions.
TL;DR: In this article, the effects of V, Cr, and Mn on the magnetic, elastic, and thermal properties of FeCoNiCu high-entropy alloy were studied by using the exact muffin-tin orbitals method in combination with the coherent potential approximation.
Abstract: The effects of V, Cr, and Mn on the magnetic, elastic, and thermal properties of FeCoNiCu high-entropy alloy are studied by using the exact muffin-tin orbitals method in combination with the coherent potential approximation. The calculated lattice parameters and Curie temperatures in the face-centered-cubic structure are in line with the available experimental and theoretical data. A significant change in the magnetic behavior is revealed when adding equimolar V, Cr, and Mn to the host composition. The three independent single-crystal elastic constants are computed using a finite strain technique, and the polycrystalline elasticity parameters including shear modulus, Young’s modulus, Pugh ratio, Poisson’s ratio, and elastic anisotropy are derived and discussed. The effects of temperature on the structural parameters are determined by making use of the Debye–Gruneisen model. It is found that FeCoNiCuCr possesses a slightly larger thermal expansion coefficient than do the other alloys considered here.
TL;DR: In this article, the interaction between a spark-generated bubble and an elastic sphere is investigated, where the authors observe pronounced deformation and elongation of the elastic sphere when the spark-bubble is generated very close to a sphere.
TL;DR: In this article, the stabilizing effect of elasticity in the Rayleigh-Taylor (RT) problem of stratified immiscible viscoelastic fluids, separated by a free interface and in the presence of a uniform gravitational field, in a horizontally periodic domain where the velocities of the fluids are non-slip on both upper and lower fixed flat boundaries, was investigated.
TL;DR: In this article, the authors investigated the microscopic origin of twist-bend coupling between two versions of oxDNA, a coarse-grained model of nucleic acids, and showed that this interaction is negligible in the oxDNA version with symmetric grooves.
Abstract: It is well established that many physical properties of DNA at sufficiently long length scales can be understood by means of simple polymer models. One of the most widely used elasticity models for DNA is the twistable worm-like chain (TWLC), which describes the double helix as a continuous elastic rod with bending and torsional stiffness. An extension of the TWLC, which has recently received some attention, is the model by Marko and Siggia, who introduced an additional twist-bend coupling, expected to arise from the groove asymmetry. By performing computer simulations of two available versions of oxDNA, a coarse-grained model of nucleic acids, we investigate the microscopic origin of twist-bend coupling. We show that this interaction is negligible in the oxDNA version with symmetric grooves, while it appears in the oxDNA version with asymmetric grooves. Our analysis is based on the calculation of the covariance matrix of equilibrium deformations, from which the stiffness parameters are obtained. The estimated twist-bend coupling coefficient from oxDNA simulations is G=30±1 nm. The groove asymmetry induces a novel twist length scale and an associated renormalized twist stiffness κt≈80 nm, which is different from the intrinsic torsional stiffness C≈110 nm. This naturally explains the large variations on experimental estimates of the intrinsic stiffness performed in the past.
TL;DR: In this article, the authors present a simple theory of rubber mechanics which takes into account the length distribution of strands and its effect on the onset of bulk failure. But this theory is based on the assumption of entropic elasticity of networks whose constitutive strands are of uniform length.
TL;DR: In this article, a non-classical Bernoulli-Euler beam model for determining band gaps for elastic wave propagation in a periodic composite beam structure was developed using the Bloch theorem and transfer matrix method for periodic structures.
TL;DR: In this article, a multi-surface approach is proposed to describe nonlinear and hysteretic unloading-reloading behaviors of sheet metals, adopting the concept of multiple yield surfaces in the Mroz model.
TL;DR: The concept of a non-smooth viscosity solution is introduced which is described by generalized variational inequalities and coincides with the weak solution in the smooth case and is proved by the construction of an approximation problem using elliptic regularization and penalization techniques.
Abstract: A major drawback of the study of cracks within the context of the linearized theory of elasticity is the inconsistency that one obtains with regard to the strain at a crack tip, namely it becoming infinite. In this paper we consider the problem within the context of an elastic body that exhibits limiting small strain wherein we are not faced with such an inconsistency. We introduce the concept of a non-smooth viscosity solution which is described by generalized variational inequalities and coincides with the weak solution in the smooth case. The well-posedness is proved by the construction of an approximation problem using elliptic regularization and penalization techniques.
TL;DR: A numerical model for bubble dynamics in tissue-like, viscoelastic media is presented, in which full thermal effects are included inside and outside the bubble, as well as interdiffusion of vapor and non-condensible gas inside the bubble.
Abstract: In certain cavitation-based ultrasound techniques, the relative importance of thermally vs mechanically induced damage is unclear. As a first step to investigate this matter, a numerical model for bubble dynamics in tissue-like, viscoelastic media is presented in which full thermal effects are included inside and outside the bubble, as well as interdiffusion of vapor and non-condensible gas inside the bubble. Soft tissue is assumed to behave according to a Kelvin-Voigt model in which viscous and elastic contributions are additive. A neo-Hookean formulation, appropriate for finite-strain elasticity, accounts for the large deformations produced by cavitation. Numerical solutions to problems of relevance to therapeutic ultrasound are examined, and linear analysis is used to explain the underlying mechanisms. The dependence between the surrounding medium's elasticity (shear modulus) and the extent to which the effects of heat and mass transfer influence bubble dynamics is quantified. In particular, the oscillation properties are related to the eigenvalues determined from linear theory. Regimes under which a polytropic relation describes the heat transfer to sufficient accuracy are identified, for which the complexity and computational expense associated with solving full partial differential equations can be avoided.
TL;DR: In this paper, a finite element numerical method is adopted to calculate the effective Young's modulus, Poisson's ratio, and pure shear modulus of a homogenized plate.
Abstract: Microstructured plates, consisting of various conventional and re-entrant cells, are numerically constructed and analyzed for their effective elastic properties under in-plane deformation. The finite element numerical method is adopted. The calculated effective Poisson's ratios of the plates are found to be in the range between −1 and 1, in consistency with the theory of two-dimensional elasticity. Auxetic angles need to be greater than about 20° in order to obtain negative Poisson's ratio. Increasing the auxetic angles reduces the effective pure shear modulus. Elastically anisotropic characteristics of the homogenized plate are analyzed with the calculated effective Young's modulus, Poisson's ratio, and pure shear modulus.
TL;DR: In this paper, a strain gradient elasticity formulation for capturing the size effect in micro-scaled structures is presented to analyze the thermoelastic response of a functionally graded micro-rotating cylinder.
Abstract: In this paper, a strain gradient elasticity formulation for capturing the size effect in micro-scaled structures is presented to analyze the thermoelastic response of a functionally graded micro-rotating cylinder. The temperature distribution in the micro-rotating cylinder is analytically obtained by solving the steady-state, one-dimensional and axisymmetric Fourier heat conduction equation. For a functionally graded micro-rotating cylinder, except Poisson’s ratio, all mechanical and thermal properties such as elastic modulus, density and thermal expansion coefficient are assumed to vary through the thickness according to a power-law distribution. The thermomechanical governing differential equation is obtained as a fourth-order ordinary differential equation in terms of mechanical displacement. The generalized differential quadrature method is used for the solution of thermal stresses, strains and displacement in the micro-rotating cylinder under internal and external pressure. At first, numerical results are presented for the micro-rotating cylinder to validate the generalized differential quadrature method. Then, the results obtained from the strain gradient elasticity are compared to the classical elasticity solution. Furthermore, numerical results illustrate the effects of non-homogeneity constant, thermal field and rotation on the distribution of Von Mises stress, Von Mises strain and radial displacement. It is perceived that the mentioned parameters have considerable effects on the distribution of stress, strain and displacement.