Changes In Elastic Properties Research Articles

Non-destructive degradation assessment of GFRP beams subjected to hygrothermal ageing

This work used free vibration tests based on impulse excitation technique and experimental modal analysis using an impact hammer and an accelerometer to assess the local and global effects of the hygrothermal ageing of GFRP specimens exposed to salt-spray environment at 35°C and 60°C over a period of 136 days. Through the change in elastic properties, fifteen natural frequencies and damping ratios, the effects of degradation are associated with reductions in elastic properties and natural frequencies and an increase in damping ratios. In turn, the increase in elastic properties and natural frequencies – associated with a reduction in damping ratios – is mainly attributed to the post-curing effect.

Effect of impurities on elastic properties and grain boundary strength of vanadium：A first principles study

During the processing of vanadium, the inevitable incorporation of impurities can exert a significant influence on the mechanical properties. In this work, the effects of common impurity elements (H, C, N, O, Al, Cr and Fe) on elastic properties and V ∑3(111) grain boundary strength were studied by first-principles calculations. The results show that the H, C, N, O and Al elements can improve the deformation resistance but reduce the ductility of vanadium, whereas Fe exhibit the opposite effect. Electronic structure analysis provided a reasonable explanation for the observed changes in elastic properties. Then, first-principles-based tensile tests were carried out on vanadium grain boundary with impurities. The findings demonstrate that C enhances the tensile strength of vanadium grain boundary by improving the weakest bonds between adjacent V atoms. Conversely, the detrimental effect of O was attributed to the reduction of interaction between V atoms. This study contributes to a better knowledge of the potential positive and negative impacts of impurities on the mechanical properties of vanadium and provides valuable insights for future research in materials processing.

Effect of degradation in polymer scaffolds on mechanical properties: Surface vs. bulk erosion

Porous polymeric scaffolds are used in tissue engineering to maintain or replace damaged biological tissues. Once embedded in body, they are involved into different physical and biological processes, among which their degradation and dissolution of their material can be singled out as one of the most important ones. Degradation parameters depend mostly on the properties of both the material and surrounding native tissues, which can substantially alter the original mechanical parameters of the scaffolds. The aim of this study is to examine the change in the effective mechanical properties of functionally graded additively manufactured polylactide scaffolds with a linear porosity gradient and morphology based on triply periodic minimal surfaces during simultaneous degradation and compressive loading. Two main types of scaffold-degradation processes, bulk and surface erosions are simulated with two suggested modelling methods. The fundamental differences in the proposed approaches are identified and the influence of different types of scaffold morphology on the change in effective elastic properties is evaluated. The results of this study can be useful for design of optimal scaffolds taking into account the effect of the degradation process on their structural integrity.

Random processes in modeling durability of building and structure

The problem of buildings and structures durability during their long-term operation in aggressive environments is discussed. It is closely connected with the problem of destruction of composite materials as a random process of birth, development, and death of defects at chemical corrosion. The content of the study is to analyze the influence of non-stationary chemical reactions occurring in real conditions on these processes. The analysis is carried out taking into account the incidental physical phenomena affecting corrosion, the most important of which is the diffusion of initial substances and reaction products occurring under different hydrodynamic conditions, i.e., the nature of fluid motion and its pressure which stimulates corrosion. The synthesis of three processes – chemical kinetics, diffusion, and hydrodynamics – allows us to study one of the possible scenarios of corrosion process development as a Markov process based on the statistical theory of the “weakest” link and the joint distribution of the random material and geometric parameters. Numerical analysis of changes in elastic and electrical properties of composite materials under these conditions allows us to substantiate the technology of non-destructive control of changes in the state of the structure. The research results are based on mathematical and statistical modeling.

P‐Wave Velocities Across the α → β Quartz Transition at Lower Continental Crust Pressure and Temperature Conditions

AbstractThe quartz α → β transition is a displacive phase transition associated with a significant change in elastic properties. However, the elastic properties of quartz at high‐pressure and temperature remain poorly constrained experimentally, particularly within the field of β‐quartz. Here, we conducted an experimental study on the quartz α → β transition during which P‐wave velocities were measured in‐situ at pressure (from 0.5 to 1.25 GPa) and temperature (200–900°C) conditions of the continental lower crust. Experiments were carried out on samples of microcrystalline material (grain size of 3–6 μm) and single‐crystals. In all these, the transition was observed as a minimum in P‐wave velocities, preceded by an important softening while P‐wave velocities measured in the β‐quartz field were systematically lower than that predicted by thermodynamic databases. Additional experiments during which acoustic emission (AE) were monitored showed no significant peak of AEs near or at the transition temperature. Microstructural analysis nevertheless revealed the importance of microcracking while Electron Back‐Scatter Diffraction (EBSD) imaging on polycrystalline samples revealed a prevalence of Dauphiné twinning in samples that underwent the transition. Our results suggest that the velocity change due to the transition known at low pressure might be less important at higher pressure, implying a change in the relative compressibilities of α and β quartz. If true, the velocity changes related to the α → β quartz transition at lower crustal conditions might be lower than that expected in thickened continental crust.

Sanding phenomena vulnerability observations due to CO2 injection at the Air Benakat reservoir in South Sumatera

Carbon sequestration using carbon capture storage (CCS) is one of the most important operational activities in the oil and gas industry to reduce greenhouse gas emissions and increase hydrocarbon production. Carbon Capture Utilization & Storage (CCUS) can be utilized for both enhancing oil recovery (CO2-EOR), as well as gas recovery (CO2-EGR) by injecting CO2 into the reservoir. However, the CO2 injection into reservoir rock can raise potential sanding problems in both injection and production wells. The phenomena of sanding may be induced dominantly due to carbonic acid injection in the reservoir. The reaction between CO2 and water will form carbonic acid in the reservoir, which can cause the dissolution of rock minerals, especially carbonate cementation (such as calcite and dolomite). We have investigated the sanding effect when CO2 was injected into the reservoir using several laboratory-scale measurements and observations on the Air Benakat reservoir sample in South Sumatera. The sanding vulnerability was measured by observing pore structure, changes in elastic properties, and rock strength through Rock Physics and Rock Mechanics measurements. XRD analysis showed the presence of CaMg(CO3)2 (dolomite) minerals in the Air Benakat sandstone sample, which resulted in the possibility of a chemical reaction of the sample, either matrix or pores. The pore structure dissolution was detected from microscale images when the rock was injected with CO2 dissolved in brine water. The changes in rock’s pores due to the dissolution process were also clearly observed from measurements of the changes in rock mass during the injection process of carbonic acid fluid into rock samples from time-to-time measurement.

Demonstrating resonant ultrasound spectroscopy as a viable technique to characterize thermally conditioned high explosive materials

We present results of resonant ultrasound spectroscopy (RUS) measurements applied to granular high explosive materials at different bulk pressing densities and degree of thermal conditioning. The material chosen in this study is a ubiquitously used explosive material known as pentaerythritol tetranitrate (PETN), which is used commercially in civil and defense applications both as a binderized plastic bonded explosive material and an unbinderized neat material. However, changes in granular PETN bulk elastic properties due to thermal conditioning, which could have implications for better understanding environmental aging-related effects, have not been well studied even though it is believed that elasticity may play an important role in explosive material initiation mechanisms. Furthermore, monitoring elastic property changes in granular explosive pressings has not yet been demonstrated using RUS, which is an appealing non-destructive characterization tool that requires only dry point contact with the explosive material. To this end, we report the first study using RUS to quantify the elastic properties of binderized and neat PETN pressings as well as to quantify changes in elastic properties as a function of both thermal conditioning and bulk pressing density. Elastic stiffness coefficients, sometimes more commonly referred to as elastic constants, calculated from the RUS measurements on the different PETN-based materials show a significant increase for the post-conditioned samples compared to the pre-conditioned samples. This trend of increasing elastic properties with thermal conditioning was consistent for different density pressings, different thermal exposure conditions, and even different neat PETN pressings of differing average crystal sizes and/or specific surface areas.

Investigating the electronic, optical, elastic, and mechanical properties of cubic CsPbI3 under varying stress conditions: A computational analysis using density functional theory

This research investigates the electronic, optical, elastic, and mechanical characteristics of cubic Cesium Lead Iodide CsPbI3 perovskite by utilizing the Generalized Gradient Approximation method under varying stress conditions ranging from 0 to 13[Formula: see text]GPa. Using the Density Functional Theory, the research demonstrates that electronic parameters, such as the electronic band gap, the partial density of states, and the total density of states, are impacted by applied stress. The band gap becomes zero at 14[Formula: see text]GPa. Significant changes are also noted in optical parameters, such as absorption, conductivity, reflectivity, dielectric function, loss function, and refractive index. The study also identifies changes in elastic properties, including elastic constants as well as an exponential rise in mechanical properties, such as Young’s modulus, bulk modulus, and shear modulus. Furthermore, the study finds that Poisson’s ratio, Cauchy pressure, Pugh’s ratio, and Frantsevich’s ratio experience irregular changes. These discoveries provide valuable insights into the properties of CsPbI3, which could aid in the development of semiconducting devices, transparent coatings, and lenses.

Computational homogenization of linear elastic properties in porous non-woven fibrous materials

Porous non-woven fibrous media are widely used in various industrial applications such as filtration, insulation, and medical textiles due to their unique structural and functional properties. However, predicting the mechanical behavior of these materials is challenging due to their complex microstructure and anisotropic nature. In this study, a computational model is developed to simulate the mechanical response of porous non-woven fibrous media under external loading. The model is based on the finite element method and takes into account the geometric and material properties of the fibers and the void spaces between them. The effects of various factors such as fiber size, porosity, and fibers’ intersection ratio on the mechanical behavior of the material are investigated. The results reveal that the material’s porosity and fibers’ intersection ratio are the most significant factors influencing its mechanical properties. Additionally, the increase in fiber diameter has a relatively minor effect on the material’s elastic properties. However, such changes in elastic properties are primarily attributed to the increase in randomness within the fibrous network, which is directly related to the fiber diameter for the investigated structure. The proposed computational model predicts the mechanical properties of porous non-woven fibrous media and can provide invaluable insights into the design and optimization of porous non-woven fibrous media for various scientific and engineering applications.

Characterizing and Quantifying Material Fatigue of the Artificial Urinary Sphincter Pressure Regulating Balloon

ObjectiveTo characterize and quantify changes in elastic properties and in vivo pressure characteristics of pressure regulating balloons (PRB) over time, we conducted an analysis of the mechanical characteristics of the PRB after removal from patients for revision surgery. MethodsPressure and elasticity characteristics of new and used 61-70cmH20 PRBs were analyzed. Pressure-volume curves were generated using commercially available urodynamics equipment. PRB pressures were measured at a standard fill volume (23cc). Elastance was calculated by the slope of the tangent line at the inflection point of the pressure-volume curve. Tests were repeated 5 times per PRB and intraclass correlations were used to gauge test-retest reliability. Regression models were used for continuous variables based on data distribution. ResultsTwenty-seven used PRBs were analyzed after excluding three for alternative pressure ratings and two for occult pinpoint leaks. Time from AUS placement to removal ranged from 0.02 to 17.6 years (median 8.4, IQR 5.7-10.0). The mean pressure of all extracted PRBs: 58.8cmH2O (±7.4), 17 (62.9%) below the standard operating range. Each year of use in-vivo was associated with 1.09cmH20 pressure loss on linear regression (p<0.01 CI -1.52 to -0.65). PRB pressures were not significantly different according to indication for removal (one-way ANOVA p=0.11). Loss of elastance was non-linear, decreasing by 1.9% per year on Poisson regression (p<0.01, CI -0.03 to -0.01). When accounting for PRB age, PRB pressure was independently associated with detrusor overactivity. ConclusionsIn PRBs tested for pressure-volume characteristics, increasing PRB age was associated with decreased pressure and elasticity.

Risk assessment of reactive local sand use in aggregate mixtures for structural concrete

Potential use of marginal fine aggregate in concrete is hindered by prescriptive quality requirements for concrete constituents. Experimental tests were performed on eleven mixtures of coarse and fine aggregates of variable susceptibility to alkali silica reaction (ASR). The miniature concrete prism test was applied for evaluation of ASR-induced expansion and associated changes of elastic properties were evaluated using the resonance modulus testing. Substitution of nonreactive sand with sands of moderate reactivity resulted in a relative increase in concrete expansion by 19–112% and substantial reduction of its elastic properties during the exposure to accelerated ASR environment. The Kolmogorov-Avrami-Mehl-Johnson model, modified to incorporate separately the effects of moderate reactivity of coarse and fine aggregate fractions, successfully described the kinetics of ASR-induced expansion. Beneficial effects of blastfurnace slag used for partial replacement of Portland clinker in blended cements were captured for aggregate combinations.

A novel anisotropy template for an improved interpretation of elastic anisotropy data

Tight unconventional rocks are characterized by the presence of laminations, preferentially oriented cracks, and an interconnected network of compliant minerals. Such anisotropic features can mechanically deform due to pressure depletion during production, leading to a human-induced change of elastic and fluid transport properties. Rock physics models allow us to better predict and assess stress- and direction-dependent elastic moduli of the rock, useful for horizontal stress estimates. However, elastic anisotropy can be challenging to measure and interpret. We have developed an anisotropy template that can be used to assess stress-dependent changes in elastic moduli and investigate rock textures. We present here the template construction using an effective medium model consisting of stiff and compliant layers and crack inclusions and evaluate the origin of stress-dependent stiffness changes in acoustic data from Berea, Bakken, Three Forks, and Mancos formations.

Molecular Dynamics Simulation of Forsterite and Magnesite Mechanical Properties: Does Mineral Carbonation Reduce Comminution Energy?

This work compares the mechanical properties of two geomaterials: forsterite and magnesite. Various physical conditions are considered to investigate the evolution of stress–strain relationships for these two polycrystals. A molecular-scale study is performed on three-dimensional models of forsterite and magnesite. Three different temperatures (300 K, 500 K, and 700 K) and strain rates (0.001, 0.01, and 0.05 ps−1) are considered to initiate deformation in the polycrystals under tensile and compressive forces. The polycrystalline structures face deformation at lower peaks at high temperatures. The Young’s modulus values of forsterite and magnesite are found to be approximately 154.7451 GPa and 92.84 GPa under tensile forces and these values are found to be around 120.457 GPa (forsterite) and 77.04 GPa (magnesite) for compressive forces. Increasing temperature reduces the maximum strength of the polycrystalline structures, but forsterite shows higher ductility compared to magnesite. Strain rate sensitivity and the effect of grain size are also studied. The yield strengths of the forsterite and magnesite drop by 7.89% and 9.09% when the grain size is reduced by 20% and 15%, respectively. This study also focuses on the changes in elastic properties for different pressures and temperatures. In addition, from the radial distribution function (RDF) results, it was observed that the peak intensity of pairwise interaction of Si–O is higher than that of Mg–O. Finally, it is found that the formation of magnesite, which is the product of mineral carbonation of forsterite, is favorable in terms of mechanical properties for the comminution process.

Fault Rheology Control on Rupture Propagation and Aftershocks Distribution during the 2016–2017 Central Italy Earthquakes

Abstract The stress released by the large coseismic ruptures and related aftershock sequences is strongly a heterogeneous process. We show highly resolved images of the normal fault system ruptured during the 2016–2017 central Italy earthquake sequence, as obtained by the high-resolution local earthquake tomography allowing relocation of a massive set of aftershocks. We get evidence that lateral changes of elastic properties on the fault planes account for the complexity in the rupture processes during the two Mw &amp;gt; 6 earthquakes. We observe an emergent phase in the first part of the Mw 6.5 rupture, and the coseismic slip becomes large when the rupture breaks through high Poisson ratio portions of the fault. Mainshocks break the fault portions that, although limited and segmented by inherited structural complexity, were dynamically interfering during the faulting episodes. The close repetition of slip on the same relatively high Poisson ratio patch suggests a dynamic weakening of the fault and/or an incomplete stress release during the first mainshock.

In vivo measurement of the elastic properties of pelvic floor muscles in pregnancy using shear wave elastography.

We aimed to investigate changes in the elastic properties of levator ani muscle (LAM) and external anal sphincter (EAS) during pregnancy using shear wave elastography (SWE). Our secondary objective was to examine the association between the elastic properties of pelvic floor muscles (PFM) and perineal tears at childbirth. This was a prospective monocentric study, including nulliparous women. Three visits were planned (14-18, 24-28, and 34-38weeks) with a SWE assessment of the LAM and EAS at rest and during Valsalva maneuver. Then, we collected data about the delivery's characteristics. Assessments were performed using an Aixplorer V12® device (SL 18-5 linear probe) using a transperineal approach, reporting the shear modulus in kPa. We looked for changes in PFM's elastic properties during pregnancy using one-way ANOVA for repeated measures. We compared the mean shear modulus in late pregnancy for each muscle and condition between women with an intact perineum at delivery and those with a perineal tear using Student's t test. Forty-seven women were considered. Forty-five women had vaginal delivery of which 38 (84.4%) had perineal tears. We did not report any significant changes in the elastic properties of PFM during pregnancy. Women with an intact perineum at delivery had a stiffer EAS at Valsalva maneuver in late pregnancy (27.0kPa vs. 18.2kPa; p < 0.005). There were no significant changes in the elastic properties of the PFM in pregnancy. Stiffer EAS in late pregnancy appears to be associated with a lower incidence of perineal tears.

Laboratory acousto-mechanical study into moisture-induced changes of elastic properties in intact granite

The water adsorption into pore spaces in brittle rocks affects wave velocity and transmitted amplitude of elastic waves. Experimental and theoretical studies have been performed to characterize moisture-induced elastodynamic variations due to macroporous effects; however, little attention has been paid to the manner in which wetting of nanopores affects elastic wave transmission. In this work, we extend our understanding of moisture-induced elastic changes in a microcracked nanopore-dominated medium where 80 % of the surface area exhibits pore diameters (also include microcrack widths) below 10 nm. We study acousto-mechanical response resulting from a gradual wetting on a free-standing intact Herrnholz granite specimen over 98 h using time-lapse ultrasonic and digital imaging techniques. Linkages between ultrasonic attributes and adsorption-induced stress/strain are established during the approach of the wetting front. We find that Gassmann theory, previously validated in channel-like nanoporous media, does not work properly in predicting the P-wave velocity increase of microcracked nanopore-dominated media at ultrasonic frequency. However, squirt flow – a theory recognized to characterize wave velocity increase and attenuation in microcracked macropore-dominated media at the pore scale – also accounts for the observed increase of P-wave velocity in microcracked nanopore-dominated media. The transmitted amplitude changes in direct P waves are explained and predicted by the elastic wave propagation within P-wave first Fresnel zone and reflection/refraction on the wetting front.

Observation of discrepancy between the degradation of polymer scaffolds in vitro and in vivo according to high-resolution ultrasound technique

Biocompatible, biodegradable polymers are actively used as drug delivery systems and as tissue engineering scaffolds. The hydrothermal aging of polymers, including degradation of the microstructure and changes of mechanical properties directly depends on environmental conditions. In vitro studies in a model media cannot contain and describe all the factors influencing the polymer degradation in a living organism. It seems promising to study the processes of changes in the microstructure and elastic properties of polymer implants invivo in dynamics. Here, we present data from the application of new experimental equipment for high-resolution ultrasound imaging of polymer degradation in vivo. Ultrasonic results include images of the transformation of volumetric microstructure and changes in elastic properties in dynamics. The method was verified on a rapidly degradable polymer poly(D,L-lactide-co-glycolide). We assess and compare the evolution of volume microstructure, elastic properties and molecular weight of the polymer weekly for 1.5 months of incubation in vitro and in vivo. We found that the in vivo degradation process occurs with a delay of 2 weeks compared to the hydrothermal aging invitro.

Acoustic Micro-Tapping Optical Coherence Elastography to Quantify Corneal Collagen Cross-Linking

To evaluate changes in the anisotropic elastic properties of exvivo human cornea treated with ultraviolet cross-linking (CXL) using noncontact acoustic micro-tapping optical coherence elastography (AμT-OCE). Acoustic micro-tapping OCE was performed on normal and CXL human donor cornea in an exvivo laboratory study. Normal human donor cornea (n=22) divided into 4 subgroups. All samples were stored in optisol. Elastic properties (in-plane Young's, E, and out-of-plane, G, shear modulus) of normal and ultraviolet CXL-treated human corneas were quantified using noncontact AμT-OCE. A nearly incompressible transverse isotropic model was used to reconstruct moduli from AμT-OCE data. Independently, cornea elastic moduli were also measured with destructive mechanical tests (tensile extensometry and shear rheometry). Corneal elastic moduli (in-plane Young's modulus, E, in-plane, μ, and out-of-plane, G, shear moduli) can be evaluated in both normal and CXL treated tissues, as well as monitored during the CXL procedure using noncontact AμT-OCE. Cross-linking induced a significant increase in both in-plane and out-of-plane elastic moduli in human cornea. The statistical mean in the paired study (presurgery and postsurgery, n=7) of the in-plane Young's modulus, , increased from 19 MPa to 43 MPa, while the out-of-plane shear modulus, G, increased from 188 kPa to 673 kPa. Mechanical tests in a separate subgroup support CXL-induced cornea moduli changes and generally agree with noncontact AμT-OCE measurements. The human cornea is a highly anisotropic material where in-plane mechanical properties are very different from those out-of-plane. Noncontact AμT-OCE can measure changes in the anisotropic elastic properties in human cornea as a result of ultraviolet CXL.

Alloying Effect on Elastic and Mechanical Properties of Refractory Medium-Entropy Alloys from First-Principles Calculations

There is still a challenge to rapidly and accurately acquire the composition dependence of mechanical properties of multi-principal element alloys due to their huge composition space and complex electronic structures. Aiming to straightforwardly tune the mechanical properties through alloying, we systematically calculate the elastic and mechanical properties for four selected body-centered-cubic (bcc) Ti–Nb–M (M = Zr, Mo, Sn, Ta) refractory medium-entropy alloys (RMEAs) using a first-principles method. It is shown that the elastic stability of the bcc RMEAs can be significantly (weakly) improved with the increase in Nb, Mo, and Ta (Sn) content, but it is insensitive to Zr. The elastic stability, elastic modulus, hardness, and strength generally enhance, whereas Pugh’s ratio and Zener anisotropy (AZ) decrease with the increase in valence electron concentration. Additionally, there is a correlation between the magnitude of the AZ and the shape of the single-crystal Young’s modulus (E[hkl]). The largest (smallest) E[hkl] appears in the <111> (<100>) direction. Particularly, the most isotropic Ti60Nb20Mo20 has the highest hardness and strength among all the Ti–Nb–M alloys. Moreover, the change of elastic properties induced by alloying is related to the change of density of states. This work sheds deep light on the design of high-performance Ti-based multi-principal element alloys.

Monitoring fluid saturation in reservoirs using time‐lapse full‐waveform inversion

AbstractMonitoring the rock physics properties of the subsurface is of great importance for reservoir management. For either oil and gas applications or CO2 storage, seismic data are a valuable source of information for tracking changes in elastic properties which can be related to fluids saturation and pressure changes within the reservoir. Changes in elastic properties can be estimated with time‐lapse full‐waveform inversion. Monitoring rock physics properties, such as saturation, with time‐lapse full‐waveform inversion is usually a two‐step process: first, elastic properties are estimated with full‐waveform inversion, then the rock physics properties are estimated with rock physics inversion. However, multiparameter time‐lapse full‐waveform inversion is prone to crosstalk between parameter classes across different vintages. This leads to leakage from one parameter class to another, which, in turn, can introduce large errors in the estimated rock physics parameters. To avoid inaccuracies caused by crosstalk and the two‐step inversion strategy, we reformulate time‐lapse full‐waveform inversion to estimate directly the changes in the rock physics properties. Using Gassmann's model, we adopt a new parameterization containing porosity, clay content and water saturation. In the context of reservoir monitoring, changes are assumed to be induced by fluid substitution only. The porosity and clay content can thus be kept constant during time‐lapse inversion. We compare this parameterization with the usual density–velocity parameterization for different benchmark models. Results indicate that the proposed parameterization eliminates crosstalk between parameters of different vintages, leading to a more accurate estimation of saturation changes. We also show that using the parameterization based on porosity, clay content and water saturation, the elastic changes can be monitored more accurately.