Dynamic Elasticity Research Articles

Nonlinear slow dynamic elasticity in metal systems

Nonlinear “slow dynamic elasticity” is found to be universal amongst geological materials and other materials with complex microstructures, such as cement and cracked glass blocks. The slow dynamic behavior is characterized by a log(time) recovery, after an initial drop of stiffness, induced by strain events as small as a microstrain. Slow dynamic behavior is also reported in unconsolidated aggregates of glass beads under pressure and in single glass beads confined between glass plates, systems that are probed by diffuse ultrasound and monitored for stiffness changes using coda-wave interferometry. At present, there is no consensus as to the microphysical basis for the behavior, though hypotheses include glassy dynamics at grain-grain interfaces, microcracking, thermal activation of a distribution of atomic-scale barriers, and moisture. Here we extend the materials known to exhibit slow dynamics to include metal structures: an aluminum bead pack under pressure, and individual aluminum and steel beads confined between aluminum and steel plates, respectively. We find that the strength of the slow dynamics is largely the same as it is for glass beads, suggesting that neither cracking nor glassy micro-structures are essential.

FORMULATION AND CHARACTERISATION OF MUCOADHESIVE DENTAL APPLICATIONS CONTAINING BENZYDAMINE HYDROCHLORIDE

The aim of this research was to develop a bioadhesive film based on benzydamine hydrochloride incorporated into natural bioadhesive polymers with different quantities of chitosan and guar gum but utilising a plasticiser. The obtained gels were deaerated by sonification, formed and evaporated by hot air drying; then, the properties were evaluated. Guar gum had a great influence on mechanical properties of the films – dynamic viscosity, texture, elasticity, stretching robustness, swelling and blur time. The formulations were used to obtain mucoadhesive films containing 0.3% benzydamine hydrochloride; they were tested for the release of the model drug. The amount of chitosan added to the formulation reduced the quantity of released substance and slowed down the release. Fouriertransform infrared spectroscopy did not reveal the creation of new chemical structures. In conclusion, the ratio of chitosan to guar gum in the medium impacts the mechanical properties and release parameters of the drug. These findings should enable researchers to match the parameter values to receive the most beneficial therapeutic outcome.

PySPH: A Python-based Framework for Smoothed Particle Hydrodynamics

PySPH is an open-source, Python-based, framework for particle methods in general and Smoothed Particle Hydrodynamics (SPH) in particular. PySPH allows a user to define a complete SPH simulation using pure Python. High-performance code is generated from this high-level Python code and executed on either multiple cores, or on GPUs, seamlessly. It also supports distributed execution using MPI. PySPH supports a wide variety of SPH schemes and formulations. These include, incompressible and compressible fluid flow, elastic dynamics, rigid body dynamics, shallow water equations, and other problems. PySPH supports a variety of boundary conditions including mirror, periodic, solid wall, and inlet/outlet boundary conditions. The package is written to facilitate reuse and reproducibility. This article discusses the overall design of PySPH and demonstrates many of its features. Several example results are shown to demonstrate the range of features that PySPH provides.

An adaptive demand response framework using price elasticity model in distribution networks

Price elasticity model (PEM) is an appealing and modest model for assessing the potential of flexible demand in demand response (DR). It measures the customer’s demand sensitivity through elasticity in relation to price variation. However, application of PEM is partially apprehensible on attributing the adaptability and adjustability along with intertemporal constraints in DR. Thus, this article presents an adaptive economic DR framework with its attributes via a dynamic elasticity approach to model customer’s demand sensitivity. This dynamic elasticity is modeled through the deterministic and stochastic approaches. Both approaches envision the notion of load recovery for shiftable/flexible loads to make the proposed framework adaptive and adjustable relative to price variation. In stochastic approach, a geometric Brownian motion is employed to emulate load recovery in addition to intertemporal constraint of load flexibility. The proposed mathematical model shows what should be the customers elasticity value to achieve the factual DR. The numerical study is carried out on standard IEEE 33 distribution system bus load data to assess its technical and socio-economic impact on customers and is also compared with the existing model.

Elastic Slow Dynamics in Polycrystalline Metal Alloys

Elastic slow dynamics, consisting in a reversible softening of materials when an external strain is applied, was experimentally observed in polycrystalline metals and presents analogies with the same phenomenon more widely observed in consolidated granular media. Since the effect is extremely small in metals, precise experimental techniques are needed. Reliable measurement of relative velocity variations of the order of 10−7 is crucial to perform the analysis. In addition, the grain structure and the nature of grain boundaries in metals is very different from that in rocks or concrete. Therefore, linking relaxation elastic effects to the microstructure is needed to understand the physical origin of slow dynamics in metals. Here, interpreting the relaxation phenomenon as a multirelaxation process, we show that it is sensitive to the spatial scale at the microstructural level, up to the point of allowing the identification of the existence of features at different spatial scales, particularly distinguishing damage from microstructural inhomogeneities.

Using 1,2 dimethylimidazole to improve gel thermalstability for wellbore plugging in ultra-high temperature fractured reservoirs

Working fluid loss as well as formation damage is usually encountered as a big challenge during well completion and workover for fossil-fuel production. Polymer gel is widely used for wellbore plugging to isolate the working fluid and the reservoir for controlling fluid loss and protecting the reservoir. However, with the increasing number of ultra-high temperature well (>180 °C) operations, the thermal stability of the gel plug is increasingly required. In this paper, 1,2 dimethylimidazole (C5H8N2) is first used to prepare a gel plug. The effects of C5H8N2 on gel gelation at dynamic heating mode, viscosity, elasticity, thermal stability and temporary plugging performances are evaluated at 190 °C. It is found that the addition of C5H8N2 does not affect the gelation, while a slightly viscosity-reducing effect is exhibited. At 190 °C, the gel without C5H8N2 broke down within 4 hours and lost its temporary plugging performance, while the gel with 20% imidazole remained unbroken after 60 hours. For the fractured core (5 cm in length) plugging experiments, the addition of 15% C5H8N2 significantly increased the breakthrough pressure of gels from 0.2 MPa to 1.9 MPa compared to pure gels (without C5H8N2). The enhancement mechanism of C5H8N2 is investigated. Recommendations for the application of gels with C5H8N2 are given in the paper. This paper provides an avenue for the development of gel plug to deal with wellbore temporary plugging jobs in ultra-high temperature fractured reservoirs.

Contractile behavior of the gastrocnemius medialis muscle during running in simulated hypogravity

Vigorous exercise countermeasures in microgravity can largely attenuate muscular degeneration, albeit the extent of applied loading is key for the extent of muscle wasting. Running on the International Space Station is usually performed with maximum loads of 70% body weight (0.7 g). However, it has not been investigated how the reduced musculoskeletal loading affects muscle and series elastic element dynamics, and thereby force and power generation. Therefore, this study examined the effects of running on the vertical treadmill facility, a ground-based analog, at simulated 0.7 g on gastrocnemius medialis contractile behavior. The results reveal that fascicle−series elastic element behavior differs between simulated hypogravity and 1 g running. Whilst shorter peak series elastic element lengths at simulated 0.7 g appear to be the result of lower muscular and gravitational forces acting on it, increased fascicle lengths and decreased velocities could not be anticipated, but may inform the development of optimized running training in hypogravity. However, whether the alterations in contractile behavior precipitate musculoskeletal degeneration warrants further study.

Predictive performance of dynamic arterial elastance for arterial pressure response to fluid expansion in mechanically ventilated hypotensive adults: a systematic review and meta-analysis of observational studies

BackgroundDynamic arterial elastance (Eadyn) has been extensively considered as a functional parameter of arterial load. However, conflicting evidence has been obtained on the ability of Eadyn to predict mean arterial pressure (MAP) changes after fluid expansion. This meta-analysis sought to assess the predictive performance of Eadyn for the MAP response to fluid expansion in mechanically ventilated hypotensive patients.MethodsWe systematically searched electronic databases through November 28, 2020, to retrieve studies that evaluated the association between Eadyn and fluid expansion-induced MAP increases in mechanically ventilated hypotensive adults. Given the diverse threshold value of Eadyn among the studies, we only reported the area under the hierarchical summary receiver operating characteristic curve (AUHSROC) as the primary measure of diagnostic accuracy.ResultsEight observational studies that included 323 patients with 361 fluid expansions met the eligibility criteria. The results showed that Eadyn was a good predictor of MAP increases in response to fluid expansion, with an AUHSROC of 0.92 [95% confidence interval (CI) 0.89 to 0.94]. Six studies reported the cut-off value of Eadyn, which ranged from 0.65 to 0.89. The cut-off value of Eadyn was nearly conically symmetrical, most data were centred between 0.7 and 0.8, and the mean and median values were 0.77 and 0.75, respectively. The subgroup analyses indicated that the AUHSROC was slightly higher in the intensive care unit (ICU) patients (0.96; 95% CI 0.94 to 0.98) but lower in the surgical patients in the operating room (0.72; 95% CI 0.67 to 0.75). The results indicated that the fluid type and measurement technique might not affect the diagnostic accuracy of Eadyn. Moreover, the AUHSROC for the sensitivity analysis of prospective studies was comparable to that in the primary analysis.ConclusionsEadyn exhibits good performance for predicting MAP increases in response to fluid expansion in mechanically ventilated hypotensive adults, especially in the ICU setting.

A resolvent criterion approach to strong decay of a multilayered Lamé-heat system

We consider a multilayer hyperbolic-parabolic PDE system which constitutes a coupling of 3D thermal – 2D elastic – 3D elastic dynamics, in which the boundary interface coupling between 3D fluid and 3D structure is realized via a 2D elastic equation. Our main result here is one of strong decay for the given multilayered – heat system. That is, the solution to this composite PDE system is stabilized asymptotically to the zero state. Our proof of strong stability takes place in the ‘frequency domain’ and ultimately appeals to the pointwise resolvent condition introduced by Tomilov [23]. This very useful result, however, requires that the semigroup associated with our multilayered FSI system be completely non-unitary (c.n.u). Accordingly, we firstly establish that the semigroup is indeed c.n.u., in part by invoking relatively recent results of global uniqueness for overdetermined Lamé systems on non-smooth domains. Although the entire proof also requires higher regularity results for some trace terms, this ‘resolvent criterion approach’ allows us to establish a ‘classially soft’ proof of strong decay. In particular, it avoids the sort of technical PDE multipliers invoked in [Avalos G, Geredeli PG, Muha B. Wellposedness, spectral analysis and asymptotic stability of a multilayered heat-wavewave system. J Differ Equ. 2020;269:7129–7156].

Pressure-induced two magnetic collapses in the ferromagnetic L12-Fe3Pd alloy and related elasticity and lattice dynamics anomalies

Pressure effect on the magnetic, mechanical and lattice dynamical properties of the ferromagnetic L12-Fe3Pd crystalline alloy was investigated by first-principles calculations. The calculated properties under ambient pressure are in good agreement with available theoretical results. A two-step pressure-induced collapse of magnetic moment was observed, accompanied by the collapse of the volume. The first one is at about 34.2 GPa, and the other is at about 67 GPa. While the magnetic moment disappears around 84 GPa. Thelattice dynamics calculations under high pressure revealed that the dynamically stable and unstable cases appear alternately. The system is dynamically unstable at low pressures due to the spontaneous magnetization of the system, and then the system is dynamically stable in the pressure range of 33.5 to 66.9 GPa, and this pressure range is between the first collapse pressure and second collapse pressure. The system becomes dynamically unstable again at pressure ranging from 67 to 83.7GPa, and afterwards becomes stable. Elastic constants and their dependence on pressure and related mechanical properties were investigated. Stability criteria show that ferromagnetic L12-Fe3Pd crystalline alloy is mechanically stable over the entire studied pressure range. The bulk modulus exhibits pronounced softening with pressure, and present minimum values at magnetic collapse pressures. The mechanism of elastic softening was analyzed with the magnetoelastic force. From Pugh’s ratio and Poisson’s ratio, the system exhibits brittleness at the vicinity of magnetic collapse pressures. The linear thermal expansion coefficient was calculated based on the quasi-harmonic approximation. The results reveal that the alloy does notexhibit thermal Invar behavior under zero pressure and high pressure. Finally, a high-anisotropy tetragonal structurewith space group symmetry P4/mbm was obtained by soft-mode phase transition theory, and this structure is dynamically and mechanically stable at zero pressure. Theoretical prediction suggested that the P4/mbm structure is energetically favorable than the previously reported structures at the pressure below 32 GPa and also showed that above 32 GPa the hexagonal D019 structure becomes the energetically most stable structure.

Prediction of hypotension after postural change in robot-assisted laparoscopic prostatectomy using esophageal Doppler monitoring: a prospective observational trial

Postural change from a steep Trendelenburg position to a supine position (T-off) during robot-assisted laparoscopic prostatectomy (RALP) induces a considerable abrupt decrease in the mean arterial pressure (MAP). We investigated the variables for predicting postural hypotension induced by T-off using esophageal Doppler monitoring (EDM). One hundred and twenty-five patients undergoing RALP were enrolled. Data on the MAP, heart rate, stroke volume index (SVI), cardiac index, peak velocity, corrected flow time, stroke volume variation, pulse pressure variation, arterial elastance (Ea), and dynamic arterial elastance were collected before T-off and at 1, 3, 5, 7, and 10 min after T-off using EDM. MAP < 60 mmHg within 10 min after T-off was considered to indicate hypotension, and 25 patients developed hypotension. The areas under the curves of the MAP, SVI, and Ea were 0.734 (95% confidence interval [CI] 0.623–0.846; P < 0.001), 0.712 (95% CI 0.598–0.825; P < 0.001), and 0.760 (95% CI 0.646–0.875; P < 0.001), respectively, with threshold values of ≤ 74 mmHg, ≥ 42.5 mL/m2, and ≤ 1.08 mmHg/mL, respectively. If patients have MAP < 75 mmHg with SVI ≥ 42.5 mL/m2 or Ea ≤ 1.08 mmHg/mL before postural change from T-off during RALP, prompt management for ensuing hypotension should be considered.Trial registration: NCT03882697 (ClinicalTrial.gov, March 20, 2019).

Comparison of dynamic elastisty modulus with different prediction approaches for Karaman – Konya highway pavement

In pavement design and analysis processes among mechanistic-empirical pavement design method, defining the Dynamic Elasticity Modulus(E*) of asphalt layers are very important. In analysis processes, predicting the deteriorations and E* requires some special devices and a lot of time. To simplify this process different prediction models and different approaches have been developed to predict E*. These prediction approaches prepared with huge amount of input data gathered both from construction site and laboratory tests to predict the binder and the volumetric properties of the HMA. In this paper four prediction equations have been applied to predict E* and compared the results with each other. The infrastructure model has chosen as an existing highway section with known HMA material properties. The analyses have done for five different temperatures (10⁰F, 40⁰F, 70⁰F, 100⁰F and 130⁰F) by using two different frequency values (4Hz and 10 Hz). The aim of this research study is doing a comparative assessment of four widely used E* prediction models. Results have shown a large bias between compared E*prediction results due to temperature, frequency, and material properties. Higher Frequency and newest models have shown higher E* values.

Regulation of bladder dynamic elasticity: a novel method to increase bladder capacity and reduce pressure using pulsatile external compressive exercises in a porcine model.

Dynamic elasticity is a biomechanical property of the bladder in which muscle compliance can be acutely adjusted through passive stretches and reversed with active contractions. The aim of this study was to determine if manipulating dynamic elasticity using external compression could be used as a novel method to acutely increase bladder capacity and reduce bladder pressure in a porcine model. Ex vivo experiment: bladders underwent continuous or pulsatile compression after establishing a reference pressure at bladder capacity. Bladders were then filled back to the reference pressure to determine if capacity could be acutely increased. In-vivo experiments: bladders underwent five cycles of pulsatile external compression with ultrasound confirmation. Pre and post-compression pressures were measured, and pressure was measured again 10min post-compression. Ex vivo experiment: pulsatile compression demonstrated increased bladder capacity by 16% (p = 0.01). Continuous compression demonstrated increased capacity by 9% (p < 0.03). Comparison of pulsatile to continuous compression showed that the pulsatile method was superior (p = 0.03). In-vivo experiments: pulsatile external compression reduced bladder pressure by 19% (p < 0.00001) with a return to baseline 10min post-compression. These results suggest that regulation of bladder dynamic elasticity achieved with external compression can acutely decrease bladder pressure and increase bladder capacity. Pulsatile compression was found to be more effective as compared to continuous compression. These results highlight the clinical potential for use of non-invasive pulsatile compression as a therapeutic technique to increase bladder capacity, decrease bladder pressure, and reduce the symptoms of urinary urgency.

Dynamic Elasticities Between Financial Performance and Determinants of Mining and Extractive Companies in Jordan

Dynamic Elasticities Between Financial Performance and Determinants of Mining and Extractive Companies in Jordan

Correlation between Macroscopic Elasticity and Chain Dynamics of Natural Rubber during Vulcanization as Determined by a Unique Rheo-NMR Combination

Correlation between Macroscopic Elasticity and Chain Dynamics of Natural Rubber during Vulcanization as Determined by a Unique Rheo-NMR Combination

On observability analysis and observer design for a class of nonlinear uncertain systems with general elastic vibration dynamics

AbstractThis paper focuses on the observability analysis for a general class of rigid‐flexible coupling systems constituted of rigid‐body mode and elastic vibration modes with uncertain dynamics and disturbances. And the measured output is a linear combination of rigid‐body mode and elastic vibration modes. Firstly, the necessary and sufficient condition of the observability for such system is given. Secondly, the general extended state observer design is proposed to estimate the states of both rigid‐body mode and elastic vibration modes as well as “total disturbance.” Next, the convergence of estimation errors of the general extended state observer is discussed. Then, under unobservable case, a compressed extended state observer is designed to estimate the states and the “total disturbance” acting on rigid‐body mode, and the corresponding estimation errors are studied. In addition, the theoretical results are demonstrated via the simulation on a rigid‐flexible coupling system.

A Concise and Geometrically Exact Planar Beam Model for Arbitrarily Large Elastic Deformation Dynamics.

The potential of large elastic deformations in control applications, e.g., robotic manipulation, is not yet fully exploited, especially in dynamic contexts. Mainly because essential geometrically exact continuum models are necessary to express these arbitrarily large deformation dynamics, they typically result in a set of nonlinear, coupled, partial differential equations that are unsuited for control applications. Due to this lack of appropriate models, current approaches that try to exploit elastic properties are limited to either small deflection assumptions or quasistatic considerations only. To promote further exploration of this exciting research field of large elastic deflection control, we propose a geometrically exact, but yet concise a beam model for a planar, shear-, and torsion-free case without elongation. The model is derived by reducing the general geometrically exact the 3D Simo–Reissner beam model to this special case, where the assumption of inextensibility allows expressing the couple of planar Cartesian parameters in terms of the curve tangent angle of the beam center line alone. We further elaborate on how the necessary coupling between position-related boundary conditions (i.e., clamped and hinged ends) and the tangent angle parametrization of the beam model can be incorporated in a finite element method formulation and verify all derived expressions by comparison to analytic initial value solutions and an energy analysis of a dynamic simulation result. The presented beam model opens the possibility of designing online feedback control structures for accessing the full potential that elasticity in planar beam dynamics has to offer.

STRENGTH CHANGE OF ROCKFILL DUMPS AT OPEN PIT MINES UNDER THE NATURAL CLIMATE IMPACT

The article discusses the change in the elastic properties of rockfill in the rims of an open pit dump during natural compaction under the climate impacts. Seismic survey records allowed determining limits of seasonal change in the dynamic elasticity modulus in freeze of the upper layer of dump rockfill. It is shown that dynamic Young’s modulus is exceeded 1.5 times. The results are reflective of activation of natural self-organization in rocks in the rims of an open pit dump under the natural climate impact as the strength increases in the surface layers of the dump.

Vibrations of Nonlinear Elastic Structure Excited by Compressible Flow

This study deals with the development of an accurate, efficient and robust method for the numerical solution of the interaction of compressible flow and nonlinear dynamic elasticity. This problem requires the reliable solution of flow in time-dependent domains and the solution of deformations of elastic bodies formed by several materials with complicated geometry depending on time. In this paper, the fluid–structure interaction (FSI) problem is solved numerically by the space-time discontinuous Galerkin method (STDGM). In the case of compressible flow, we use the compressible Navier–Stokes equations formulated by the arbitrary Lagrangian–Eulerian (ALE) method. The elasticity problem uses the non-stationary formulation of the dynamic system using the St. Venant–Kirchhoff and neo-Hookean models. The STDGM for the nonlinear elasticity is tested on the Hron–Turek benchmark. The main novelty of the study is the numerical simulation of the nonlinear vocal fold vibrations excited by the compressible airflow coming from the trachea to the simplified model of the vocal tract. The computations show that the nonlinear elasticity model of the vocal folds is needed in order to obtain substantially higher accuracy of the computed vocal folds deformation than for the linear elasticity model. Moreover, the numerical simulations showed that the differences between the two considered nonlinear material models are very small.

The elastic dynamics analysis of FGM using a meshless RRKPM

The radial basis reproducing kernel particle method (RRKPM) has been constructed by introducing the radial basis function (RBF) into the reproducing kernel particle method (RKPM). In this article, the RRKPM is extended to the elastic dynamic analysis of the functionally graded material (FGM), and the elastic dynamics governing equation of the FGM based on the RRKPM is obtained. Then, the influence of the penalty factor, the scaling parameter and the shaped parameter are discussed. Finally, numerical examples of the FGM verify that the RRKPM has a smaller calculation error than the RKPM, and prove the correctness of the RRKPM for solving the elastic dynamics problems of the FGM.