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In this work, the Common Model of Multi-phase Strength and Equation of State (CMMP) model was applied to tin. Specifically, calibrations of the strength-specific elements of the CMMP foundation were developed with a combination of experiments and theory, and then the model was validated experimentally. The first element of the foundation is a multi-phase analytic treatment of the melt temperature and the shear modulus for the solid phases. These models were parameterized for each phase based on ab initio calculations using the software VASP (Vienna Ab initio Simulations Package) based on density functional theory. The shear modulus model for the ambient β phase was validated with ultrasonic sound speed measurements as a function of pressure and temperature. The second element of the foundation is a viscoplastic strength model for the β phase, upon which strength for inaccessible higher-pressure phases can be scaled as necessary. The stress–strain response of tin was measured at strain rates of 10 − 3 to 3 × 10 3 s − 1 and temperatures ranging from 87 to 373 K. The Preston–Tonks–Wallace (PTW) strength model was fit to that data using Bayesian model calibration. For validation, six forward and two reverse Taylor impact experiments were performed at different velocities to measure large plastic deformation of tin at strain rates up to 10 5 s − 1 . The PTW model accurately predicted the deformed shapes of the cylinders, with modest discrepancies attributed to the inability of PTW to capture the effects of twinning and dynamic recrystallization. Some material in the simulations of higher velocity Taylor cylinders reached the melting temperature, thus testing the multiphase model because of the presence of a second phase, the liquid. In simulations using a traditional modeling approach, the abrupt reduction of strength upon melt resulted in poor predictions of the deformed shape and non-physical temperatures. With CMMP, the most deformed material points evolved gradually to a mixed solid–liquid but never a fully liquid state, never fully lost strength, stayed at the melt temperature as the latent heat of fusion was absorbed, and predicted the deformed shape well. [ABSTRACT FROM AUTHOR]

The boson peak (BP), a low-energy excess in the vibrational density of states over the Debye contribution, is often identified as a characteristic of amorphous solid materials. Despite decades of efforts, its microscopic origin still remains a mystery. Recently, it has been proposed, and corroborated with simulations, that the BP might stem from intrinsic localized modes involving one-dimensional (1D) string-like excitations ("stringlets"). We build on a theory originally proposed by Lund that describes the localized modes as 1D vibrating strings, but we specify the stringlet size distribution to be exponential, as observed in simulations. We provide an analytical prediction for the BP frequency ωBP in the temperature regime well below the observed glass transition temperature Tg. The prediction involves no free parameters and accords quantitatively with prior simulation observations in 2D and 3D model glasses based on inverse power law potentials. The comparison of the string model to observations is more uncertain when compared to simulations of an Al–Sm metallic glass material at temperatures well above Tg. Nonetheless, our stringlet model of the BP naturally reproduces the softening of the BP frequency upon heating and offers an analytical explanation for the experimentally observed scaling with the shear modulus in the glass state and changes in this scaling in simulations of glass-forming liquids. Finally, the theoretical analysis highlights the existence of a strong damping for the stringlet modes above Tg, which leads to a large low-frequency contribution to the 3D vibrational density of states, observed in both experiments and simulations. [ABSTRACT FROM AUTHOR]

Grafting polymer chains to the surface of nanoparticles overcomes the challenge of nanoparticle dispersion within nanocomposites and establishes high-volume fractions that are found to enable enhanced material mechanical properties. This study utilizes coarse-grained molecular dynamics simulations to quantify how the shear modulus of polymer-grafted nanoparticle (PGN) systems in their glassy state depends on parameters such as strain rate, nanoparticle size, grafting density, and chain length. The results are interpreted through further analysis of the dynamics of chain conformations and volume fraction arguments. The volume fraction of nanoparticles is found to be the most influential variable in deciding the shear modulus of PGN systems. A simple rule of mixture is utilized to express the monotonic dependence of shear modulus on the volume fraction of nanoparticles. Due to the reinforcing effect of nanoparticles, shortening the grafted chains results in a higher shear modulus in PGNs, which is not seen in linear systems. These results offer timely insight into calibrating molecular design parameters for achieving the desired mechanical properties in PGNs. [ABSTRACT FROM AUTHOR]

To develop special insulating paper is of great significance to promote the service life of transformers. Using molecular simulation to guide the development of special insulating paper can greatly reduce the trial-and-error rate and waste of resources in traditional experiments. The effect of different types of polysilsesquioxane (POSS) on cellulose insulating paper was investigated by using molecular simulation. This paper investigated the thermal stability and mechanical properties and electrical characteristics of caged POSS, semi-caged POSS, and ladder-like POSS doped cellulose insulating paper. The results show that POSS with all types can enhance the performance of cellulose insulating paper, and ladder-like POSS possess the best modification effect. The glass transition temperature was increased by 58 K, and the bulk modulus, shear modulus, and elastic modulus of cellulose insulating paper doped with ladder-like POSS can improve up to 27.07%, 45.67%, and 41.28%, respectively. Meanwhile, the dielectric properties of ladder-like POSS modified insulating paper are also significantly improved. The findings of this paper propose a method for the preparation of ladder-like POSS modified insulating paper, which provides theoretical guidance for the experimental preparation of special insulating paper. [ABSTRACT FROM AUTHOR]

Under decompression, disordered solids undergo an unjamming transition where they become under-coordinated and lose their structural rigidity. The mechanical and vibrational properties of these materials have been an object of theoretical, numerical, and experimental research for decades. In the study of low-coordination solids, understanding the behavior and physical interpretation of observables that diverge near the transition is of particular importance. Several such quantities are length scales (ξ or l) that characterize the size of excitations, the decay of spatial correlations, the response to perturbations, or the effect of physical constraints in the boundary or bulk of the material. Additionally, the spatial and sample-to-sample fluctuations of macroscopic observables such as contact statistics or elastic moduli diverge approaching unjamming. Here, we discuss important connections between all of these quantities and present numerical results that characterize the scaling properties of sample-to-sample contact and shear modulus fluctuations in ensembles of low-coordination disordered sphere packings and spring networks. Overall, we highlight three distinct scaling regimes and two crossovers in the disorder quantifiers χz and χμ as functions of system size N and proximity to unjamming δz. As we discuss, χX relates to the standard deviation σX of the sample-to-sample distribution of the quantity X (e.g., excess coordination δz or shear modulus μ) for an ensemble of systems. Importantly, χμ has been linked to experimentally accessible quantities that pertain to sound attenuation and the density of vibrational states in glasses. We investigate similarities and differences in the behaviors of χz and χμ near the transition and discuss the implications of our findings on current literature, unifying findings in previous studies. [ABSTRACT FROM AUTHOR]

We report results on the mechanical and structural response to shear deformation of nanodiamond superstructures in interlayer-bonded twisted bilayer graphene (IB-TBG) and interlayer-bonded graphene bilayers with randomly distributed individual interlayer C–C bonds (RD-IBGs) based on molecular-dynamics simulations. We find that IB-TBG nanodiamond superstructures subjected to shear deformation undergo a brittle-to-ductile transition (BDT) with increasing interlayer bond density (nanodiamond fraction). However, RD-IBG bilayer sheets upon shear deformation consistently undergo brittle failure without exhibiting a BDT. We identify, explain, and characterize in atomic-level detail the different failure mechanisms of the above bilayer structures. We also report the dependence of the mechanical properties, such as shear strength, crack initiation strain, toughness, and shear modulus, of these graphene bilayer sheets on their interlayer bond density and find that these properties differ significantly between IB-TBG nanodiamond superstructures and RD-IBG sheets. Our findings show that the mechanical properties of interlayer-bonded bilayer graphene sheets, including their ductility and the type of failure they undergo under shear deformation, can be systematically tailored by controlling interlayer bond density and distribution. These findings contribute significantly to our understanding of these 2D graphene-based materials as mechanical metamaterials. [ABSTRACT FROM AUTHOR]

We systematically examine the influence of varying temperature (T) over a large range in model poly(vinyl acetate) gels swollen in isopropyl alcohol. The theta temperature Θ, at which the second virial coefficient A2 vanishes, is found to be equal to within numerical uncertainty to the corresponding high molecular mass polymer solution value without cross-links, and we quantify the swelling and deswelling of our model gels relative to their size at T = Θ, as customary for individual flexible polymer chains in solutions. We also quantify the "solvent quality" dependence of the shear modulus G relative to G(T = Θ) and compare to the gel swelling factor, α. We find that all our network swelling and deswelling data can be reduced to a scaling equation of the same general form as derived from renormalization group theory for flexible linear polymer chains in solutions so that it is not necessary to invoke either the Flory–Huggins mean field theory or the Flory–Rehner hypothesis that the elastic and mixing contributions to the free energy of network swelling are separable to describe our data. We also find that changes of G relative to G(T = Θ) are directly related to α. At the same time, we find that classical rubber elasticity theory describes many aspects of these semi-dilute solution cross-linked networks, regardless of the solvent quality, although the prefactor clearly reflects the existence of network defects whose concentration depends on the initial polymer concentration of the polymer solution from which the networks were synthesized. [ABSTRACT FROM AUTHOR]

We present structural, electronic, magnetic, elastic and transport properties of tetragonal Mn2PtSn (MPS) bulk material in stannite (ST) phase, we will use a FP-LAPW method based on DFT under GGA, TB-mBJ and GGA+U as implemented in the WIEN2k code. From the ferromagnetic state, band structure (spin-down/spin-up channel) calculations reveal an indirect bandgap/zero-bandgap. Mn2PtSn shows inverse tetragonal crystal structures with ferromagnetic spin order at zero temperature. The elastic stability criterion shows that the MPS crystal satisfies the mechanical stability under applied at 0 GPa. The related mechanical properties such as bulk modulus (B), shear modulus (G), Young's modulus (E), and Poisson's ratio (ν) are also studied for polycrystalline of MPS; the calculated B/G value (B/ G = 2. 9 6) shows that MPS behaves in a ductile manner. Hence, this study of transport properties suggests their potential thermoelectric applications at high temperatures. To our knowledge, the results obtained show that this ternary alloy is advantageous for materials employed in spintronic devices. [ABSTRACT FROM AUTHOR]

In this paper, we will investigate the structural, electronic, mechanical, magnetic and optical properties of Heusler Mn2NiAl (MNA) compound using the Perdew–Burke–Ernzerhof generalized gradient approximation (PBE-GGA) of the full potential linearized augmented plane-wave method for exchange and use correlations, modified Becke–Johnson and GGA+U Hubbard parameter. The calculated band structure (BS) and density of states (DOS) of MNA showed a metallic (GGA), nearly half-metallic (mBJ) and half metallic (GGA+U) behavior. Moreover, the magnetic computed magnetic moments by GGA+U are higher compared to GGA and mBJ results. Bulk modulus, shear modulus, Voigt and Reuss polycrystalline elastic modulus, Debye temperature, sound velocities, the melting temperatures, B / G ratio, Young's modulus and Poisson's ratio were obtained. The elastic anisotropy of MNA alloy was analyzed using 2D and 3D figures of directional dependence of Poisson's ratio, shear modulus, linear compressibility and Young's modulus. Studies have shown that the Heusler material MNA has magnetic and anisotropic properties and is mechanically stable. [ABSTRACT FROM AUTHOR]

The scarcity of research on the shielding properties of spinel ferrites underscores the necessity for more rigorous investigations. Consequently, this study introduces a facile synthesis method for Co, Cu, and Sm spinel nanoferrites (referred to as CCS nanoferrites) using the citrate combustion technique. The investigation focuses on their mechanical, dielectric, and gamma-ray shielding parameters. Gamma-ray shielding features are obtained theoretically via the Phy-X database. The particle size, nature, and distribution of the present CCS nanoferrites were analyzed using HR-TEM microscopy. HR-TEM results reveal both the spherical shapes and the aggregation of nanoparticles. These observations can be attributed to the interplay of high surface energy and magnetic interactions among the components of the CCS nanoferrites. The Co 0.5 Cu 0.5 Sm 0.15 Fe 1.85 O 4 nanoferrite exhibits an optimal dielectric constant value of 4587, with an enhanced ratio of 1618% compared to the pristine CCS0 sample. Additionally, it demonstrates an optimal conductivity of 38.59 μ (Ω·m)−1, with an enhanced ratio of 1105%. Furthermore, the loss is reduced to 2.65, showing an improvement ratio of 54% compared to the pristine nanoferrite at room temperature and 50 Hz. Moreover, the longitudinal modulus, shear modulus, Young's modulus, and bulk modulus of the nanoferrite Co 0.5 Cu 0.5 Sm 0.15 Fe 1.85 O 4 were increased from 1.79 to 4.96 GPa, 0.32–0.93 GPa, 0.88–2.56 GPa, and 1.37–3.73 GPa, respectively, when compared to the pristine sample. The comparative study of half-value layers at 0.662 MeV revealed that CCS nanoferrites exhibit smaller half-value layers than common radiation shielding materials. Additionally, the study highlighted the enhanced radiation shielding performance of the nanoferrites. Concerning the dielectric, mechanical, and ionizing radiation shielding properties of the CCS spinel nanoferrites, the CCS5 (with the highest Sm content) has the optimum ionizing radiation shielding ability with the highest dielectric and mechanical parameters compared to the other samples. The implications of these findings extend to potential applications in biomedicine, radiation protection, and the optimization of electronic devices operating in radiation fields. [ABSTRACT FROM AUTHOR]

Acrylamides were shown to significantly improve bonding stability in adhesive restorations, but the reinforcement mechanism has not been fully elucidated. We tested the hypothesis that hydrogen bonding reinforcement of the collagen network (with secondary or tertiary acrylamides), as well as degree of crosslinking of the polymer network (with di- or tri-functional acrylamides), can be two of the factors at play. Two-step total etch adhesives comprising UDMA (60 wt%) and 40 wt% of: TAAEA, TMAAEA (secondary, tertiary tri-acrylamides), BAAP, DEBAAP (secondary, tertiary di-acrylamides) or HEMA (mono-methacrylate - control) were formulated. Simulated composite restorations (n = 5) were tested after cyclic mechanical and biological (S. mutans biofilm) challenges. Gap formation before and after aging was assessed with SEM imaging. Micro-tensile bond strength (μTBS, n = 6) was assessed after seven-day incubation in water or S. mutans -containing culture medium. Collagen reinforcement was assessed with hydroxyproline assay (n = 10) and rheology (n = 3). Data were analyzed with one-way/two-way ANOVA/Tukey's test (alpha=5%). Gap formation increased and bond strength decreased for all monomers after biofilm incubation (p < 0.001). Except for DEBAAP, secondary and tertiary di/tri-acrylamides showed lower occlusal gap width values, but no significant differences overall gap length compared to HEMA. μTBS increased for tri-acrylamides compared with HEMA. Samples treated with multi-acrylamides had lower concentration of hydroxyproline (by-product of collagen degradation) (p < 0.001), except for DEBAAP, which showed values close to HEMA (p > 0.05). Dentin shear modulus increased for all acrylamides after 72 h, especially TMAAEA. In general, multi-acrylamides promote collagen reinforcement, leading to reduced gap formation, and stabilize the bond strength under physiological conditions. [ABSTRACT FROM AUTHOR]

The first high damage resistant ultra-high temperature ceramic ScB 2 C 2 with excellent hydrolysis resistance was successfully prepared through boron carbon thermal reduction and hot pressing sintering using Sc 2 O 3 , B 4 C and graphite as raw materials. The Vickers hardness, flexural strength, fracture toughness, Young's modulus, shear modulus, bulk modulus and Poisson's ratio of as-prepared ScB 2 C 2 ceramic are 6.0 ± 0.2 GPa, 246 ± 17 MPa, 4.11 ± 0.18 MPa·m1/2, 240 GPa, 101 GPa, 127 GPa and 0.18, respectively. In the a - b plane (B 2 C 2 sheet) and along the c -axis direction, ScB 2 C 2 exhibits extremely strong anisotropy of chemical bonds and elastic properties. The high residual strength, damage tolerance factor D t and fracture toughness to strength ratio K Ic /σ f indicates that ScB 2 C 2 has excellent damage tolerance. In addition, ScB 2 C 2 displayed remarkable thermal shock resistance and hydrolysis resistance. These unique features endow ScB 2 C 2 with significant potential for future ultra-high temperature applications. [ABSTRACT FROM AUTHOR]

This study examines the physical, optical and mechanical characteristics of BWP glasses. The density and molar mass increase as the WO3 concentration rises, resulting in a denser and more substantial glass sample. However, the molar volume decreases, indicating a reduction in volume due to the increased density caused by WO3. The inclusion of WO3 also leads to a tighter spacing between atoms. The optical basicity of the glass increases with higher WO3 concentrations. The electronegativity decreases, suggesting the glass becomes more electron-donating. The electronic polarizability and cross-link density increase, resulting in a stiffer and more robust glass network. The mechanical moduli, including Young's modulus, bulk modulus, shear modulus, and longitudinal modulus, also increase with higher WO3 concentrations, indicating improved mechanical characteristics and reduced deformation. The Poisson's ratio shows a larger transverse deformation tendency with increasing WO3 concentration. Micro-hardness values increase with WO3 content, indicating enhanced durability and mechanical robustness. The mean free path values indicates that the higher WO3 content, or lower P2O5 content, improves the shielding ability. [ABSTRACT FROM AUTHOR]

The aim of this study was to develop a vibration pad suitable for renal MR elastography (MRE). Chronic kidney disease (CKD) is a progressive condition affecting >800 million people worldwide. Renal fibrosis is a common pathological feature of CKD that causes fibrotic regions to be much stiffer than those in normal renal tissues. Therefore, MRE can be used to diagnose CKD because it can image organ stiffness. In MRE, the shear modulus is obtained from the wavelength of the shear waves. Therefore, it is highly important to propagate shear waves with sufficient vibration strength in the tissue. By using a three-dimensional (3D) printer, we created a "Flexible Pad" suitable for renal MRE. The Flexible Pad was placed under the back of the participant in the supine position and deformed in response to the participant's weight, adhering closely to the body surface. Six healthy volunteers participated in this study. Our Flexible Pad allowed for coherent shear waves (clear waves with little scattering and interference) to be efficiently transmitted to the kidney deep-lying tissues in the abdomen. The shear moduli of the kidney (n = 6) were 8.95 ± 0.84 kPa in the right kidney and 9.70 ± 0.99 kPa in the left kidney. Our results indicate that using our Flexible Pad for renal MRE can provide a more reliable measurement of renal shear modulus. [ABSTRACT FROM AUTHOR]

Tissue susceptibility to histotripsy disintegration has been reported to depend on its elastic properties. This work was aimed at investigation of histotripsy efficiency for liquefaction of human hematomas, depending on their stiffness and degree of retraction over time (0–10 d). As an in vitro hematoma model, anticoagulated human blood samples (200 mL) were recalcified at different temperatures. In one set of samples, the shear modulus was measured by shear wave elastography during blood clotting at 10℃, 22℃ and 37℃, and then daily during further aging. The ultrastructure of the samples was analyzed daily with scanning electron microscopy (SEM). Another set of blood samples (50–200 mL) were recalcified at 37℃ for density and retraction measurements over aging and exposed to histotripsy at varying time points. Boiling histotripsy (2.5 ms pulses) and hybrid histotripsy (0.2 ms pulses) exposures (2 MHz, 1% dc, P +/ P –/ A s = 182/–27/207 MPa in situ) were used to produce either individual cigar-shaped or volumetric (0.8–3 mL) lesions in samples incubated for 3 h, 5 d and 10 d. The obtained lesions were sized, then the lysate aspirated under B-mode guidance was analyzed ultrastructurally and diluted in distilled water for sizing of residual fragments. It was found that clotting time decreased from 113 to 25 min with the increase in blood temperature from 10℃ to 37℃. The shear modulus increased to 0.53 ± 0.17 kPa during clotting and remained constant within 8 d of incubation at 2℃. Sample volumes decreased by 57% because of retraction within 10 d. SEM revealed significant echinocytosis but unchanged ultrastructure of the fibrin meshwork. Liquefaction rate and lesion dimensions produced with the same histotripsy protocols correlated with the increase in the degree of retraction and were lower in retracted samples versus freshly clotted samples. More than 80% of residual fibrin fragments after histotripsy treatment were shorter than 150 µm; the maximum length was 208 µm, allowing for unobstructed aspiration of the lysate with most clinically used needles. The results indicate that hematoma susceptibility to histotripsy liquefaction is not entirely determined by its stiffness, and correlates with the retraction degree. [ABSTRACT FROM AUTHOR]

The tight oil/gas reservoirs in China have showed the great exploration prospects and high production potential, with the characteristics of low porosity, low permeability, and significant heterogeneity in formation rocks. It remains a challenge to sort out the relations between reservoir wave responses and rock physical properties, and the further studies on the wave response patterns of tight reservoirs are in an urgent demand. The shear modulus and S- (shear) wave attenuation of rocks are affected by the properties of pore fluid and confining pressure. The ultrasonic wave experiments are performed on eight partially-saturated tight sandstone samples at different confining pressures, and we estimate S-wave attenuation with the spectral-ratio method. Results show that S-wave attenuation decreases with increasing confining pressure, and the water saturation case shows more loss compared to the oil saturation case, while the gas saturation case gives the lowest attenuation. We observe the S-wave relaxation peak at an intermediate water saturation for the gas-water partial-saturation case in general. S-wave attenuation increases with increasing porosity or permeability. Based on the measured rock physical properties, and combined with the Voigt–Reuss–Hill (VRH) average, differential effective medium (DEM) model and squirt-flow model, a tight rock attenuation model is proposed for analyzing the attenuation characteristics of fluid-saturated rocks at different confining pressures. The model reasonably describes the S-wave attenuation characteristics. The model predictions of S-wave attenuation show apparent pressure- and fluid-sensitivity at full saturation and partial saturation conditions. For sample TS1-19 at full saturation with different confining pressures, the S-wave peak attenuation predicted by the model ranges from 11.6 to 69.5, and decreases with confining pressure, while the relaxation frequency shifts to high frequency end. For the partial saturation condition of the sample, the predicted S-wave peak attenuation ranges from 15.5 to 39.8 at a confining pressure of 30 MPa and increases with water saturation, while the relaxation frequency shifts to low frequency end. For all the samples at 30MPa confining pressure, the predicted S-wave attenuation ranges from 5.6 to 38.6. At the full-saturation case, the predicted S-wave attenuation increases with porosity and decreases with confining pressure. For the partial saturation case, the S-wave attenuation predicted with the model and the Voigt and Reuss bounds generally increases with water saturation, whereas the experimentally-measured attenuation exhibits the peak attenuation at an intermediate saturation. [ABSTRACT FROM AUTHOR]

An analytical solution to the dynamic response of a functionally graded cylindrical tube embedded in a full homogeneous space subjected to elastic SH waves is presented using the wavefunction expansion method. The shear modulus of the functionally graded tube is assumed to have a power-law variation with radius. The wave fields in the tube and unbounded surrounding medium are derived in a form of wavefunction series with unknown coefficients. The wave field coefficients are obtained by satisfying the boundary conditions at the inner and outer tube surfaces. The influences of the inhomogeneity exponent, shear modulus and thickness of the functionally graded tube, and the frequency of the incident SH waves on the dynamic stress concentration factor (DSCF) of the tube are systematically discussed. It is concluded that the application of functionally graded materials (FGMs) with a positive inhomogeneity exponent tends to weaken the DSCF along the inner surface of the tube significantly but intensify that along the outer surface slightly, which is beneficial to the long-term use of the tube. [ABSTRACT FROM AUTHOR]

In recent days, the sandwich structure has created significant evolutionary changes in world technology, which are used in many sectors like automobile, aeronautical, defence, etc., The structural-based studies are evaluated and replaced with the sandwich structure, which contains three layers; a core layer, upper and lower face sheets. This article evaluates the transverse shear modulus of the sandwich core structure of 3D-printed materials. Henceforth the bioinspired structural design is adopted as core structure which is bio-mimicked from the microstructural layer design of the woodpecker's beak. Forming the wavy patterns is incorporated with the conventional honeycomb shape. The edges of the structure's waviness are modeled as champer edges with the required dimensions. The fused deposition modeling (FDM) process is carried out to bring out the expected sandwich core design. Here, the article speaks about the contest between the various types of materials like polylactic acid (PLA), acrylonitrile butadiene styrene (ABS), high impact polystyrene (HIPS), carbon fiber-polylactic acid (CF-PLA), carbon fiber - acrylonitrile butadiene styrene (CF-ABS), carbon fiber-polyethylene terephthalate glycol (CF-PETG). Each material contains specific properties; Henceforth, each material property is validated by ASTM E1876 standard. The objective is to find the good effectiveness of transverse shear modulus by the Nondestructive process called alternative dynamic method among the 3D-printed Bioinspired materials. In this study, CF-PLA stands ahead to give efficient transverse shear modulus property values. These results can be carried forward to structural development, enhancing the structure's performance as the futuristic pathway. [ABSTRACT FROM AUTHOR]

The strong sensitivity of velocity to stress observed in many sandstones originates from the response of stress‐sensitive discontinuities such as grain contacts and microcracks to a change in effective stress. If the change in stress is anisotropic, then the change in elastic wave velocities will also be anisotropic. Characterization of stress‐induced elastic anisotropy in sandstones may enable estimation of the in situ three dimensional stress tensor with important application in solving problems occurring during drilling, such as borehole instability, and during production, such as sanding and reservoir compaction. Other applications include designing hydraulic fracture stimulations and quantifying production‐induced stresses which may lead to rock failure. Current methods for estimating stress anisotropy from acoustic anisotropy rely on third‐order elasticity, which ignores rock microstructure and gives elastic moduli that vary linearly with strain. Elastic stiffnesses in sandstones vary non‐linearly with stress. Using P‐ and S‐wave velocities measured on Gulf of Mexico sandstones, this non‐linearity is found to be consistent with a micromechanical model in which the discontinuities are represented by stress‐dependent normal and shear compliances. Stress‐induced anisotropy increases with increasing stress anisotropy at small stress but then decreases at larger stresses as the discontinuities close and their compliance decreases. When the ratio of normal‐to‐shear compliance of the discontinuities is unity, the stress‐induced anisotropy is elliptical, but for values different from unity, the stress‐induced anisotropy becomes anelliptic. Although vertical stress can be obtained by integrating the formation's bulk density from the surface to the depth of interest, and minimum horizontal stress can be estimated using leak‐off tests or hydraulic fracture data, maximum horizontal stress is more difficult to estimate. Maximum horizontal stress is overpredicted based on third‐order elasticity using measured shear moduli, with estimates of pore pressure, vertical stress and minimum horizontal stress as input. The non‐linear response of grain contacts and microcracks to stress must be considered to improve such estimates. [ABSTRACT FROM AUTHOR]

Some soil characteristics, such as the shear wave velocity, the shear modulus, the Poisson ratio, and the porosity, affect how clay soils behave. The soil design parameters under loading, such as soil liquefaction induced by dynamic earthquake loading, employ the shear wave velocity and shear module with modest stress. In order to understand the pore saturation, the Poisson ratio and seismic velocity ratio are also utilized. Additionally, one of the most crucial physical characteristics for assessing permeability at the base of any engineering structure, resolving consolidation issues that may arise at the foundation of an engineering structure, and influencing the deformation behavior of soils is soil porosity. Predicting the porosity of clay soils is a crucial first step in tackling engineering and environmental issues that may arise in the soil after an earthquake or not. With the use of dynamic soil metrics such as seismic velocities, shear modules, bulk modules, seismic velocity ratios, and Poisson ratios, the current work aims to estimate soil porosity. Seismic refraction was used by various studies in the past to conduct in-situ geophysical research. The lithological characteristics of the soil (such as the grain size, shape, type, compaction, consolidation, and cementation of the grains) and the physical characteristics of the soil (such as porosity, permeability, density, anisotropy, saturation level, liquid–solid transition, pressure, and temperature), as well as the elasticity characteristics of the soil (such as shear modulus (G), bulk modulus (K), Young modulus (E), Poisson ratio (μ) and Lamé constants (λ )) all have an impact on seismic waves passing through a medium. [ABSTRACT FROM AUTHOR]

The rainy season in hot and humid areas can cause various diseases to weaken the performance of asphalt pavement. To determine the influence of rainfall on the viscoelastic properties of asphalt binder, a dry–wet cycle aging method was used to simulate the aging behavior of Gaotong base asphalt binder (GBA) and styrene–butadiene-styrene (SBS) modified asphalt binder (SBSMA), and the complex shear modulus, fatigue characteristics, and creep compliance of binders during dry–wet cycle aging were studied. The results show that the complex modulus of binders raised with the increase of dry–wet cycles time. Further, according to the simplified viscoelastic continuous damage (S-VECD) model, the damage of aged binders went up while the integrity went down sharply. Moreover, the fatigue life of SBSMA was greatly affected by aging, still far better than that of GBA. The fatigue parameters had a certain correlation with the complex modulus and they could predict the fatigue characteristics of aged binders. The creep recovery rate of GBA increased with the increase of the dry–wet cycle aging time, opposite to SBSMA. Furthermore, compared with thermal oxidative aging, the damage to the asphalt binder was worse in the later stage of dry–wet cycle aging because of the dissolution of the polar groups of binders and the continuous exposure of new surfaces. [ABSTRACT FROM AUTHOR]

The elastic properties, electronic structure, and optical properties of X (X = B , Al, Ga) atomic substitution for arsenene are calculated based on density functional theory. The results show that, at the same concentration, B-substituted arsenene shows the best structural stability, followed by Ga-substituted arsenene, with Al-substituted arsenene being the least. Arsenene and its substitution systems possess excellent mechanical stability. The substitution of X atoms leads to a reduction in the bulk modulus, shear modulus, and Young's modulus of arsenene systems, while simultaneously increasing the Poisson's ratio. For the substitution systems, the four parameters all gradually increase as the substitution concentration increases. The substitution of X (X = B , Al, Ga) atoms into arsenene can facilitate the transformation from an indirect to direct bandgap (except for Al and Ga substitution at a concentration of 3.13%) with a narrower bandgap for increasing substitution concentration. The B–As bond shows the strongest covalency, followed by the Ga–As bond, while the Al–As bond exhibits the strongest ionicity. Arsenene substituted with X atoms shows anisotropy of optical properties in both the xy-plane and along the z-axis direction. The static dielectric constant increases with higher substitution concentration. The imaginary part of the dielectric function shows the extent of excited electron transitions between bands. After X atom substitution, arsenene exhibits a redshift in its absorption edge, which is wider with the higher substitution concentrations. The peak reflectance and valley transmittance values of arsenene and its substitution systems are located in the ultraviolet region in both xy-plane and z-axis. [ABSTRACT FROM AUTHOR]

Shear strength of damage zone, representing the stress threshold for rupture initiation, is a critical parameter in faulting mechanics. Despite its significance, the damage‐zone's shear strength has not been estimated in natural earthquake ruptures. Here we employed coseismic deformation and strain, kinematic slip model, and finite element modeling to determine the elastic properties and peak shear stress of coseismic damage zones along the 2021 Mw 7.4 Maduo earthquake. Through the analysis of the lowest shear stress resulting in surface ruptures and the highest stress without surface rupture, we constrained the strength within a range of 7–17 MPa. Our result is consistent with strength (5–16 MPa) of sandstone samples from laboratory tests, demonstrating the validity of this estimation. Although factors such as fault maturity and confining pressure influence strength variation, the strength can directly reflect the stress threshold required for macroscopic surface rupture formation in fault damage zones dominated by sandstone. Plain Language Summary: Shear strength of a fault damage zone inform us its ability to withstand shear stress before surface rupture occurs. This information often provides insights into the earthquakes rupture hazards near the Earth's surface. Natural earthquakes provide a perfect opportunity for us to address the question of "what is the shear strength of a fault damage zone." To this end, we require a set of comparative references: the utmost shear stress that a damage zone can withstand without surface rupture and the minimal one necessary for the zone to generate surface rupture. In this investigation, we studied the 2021 Maduo earthquake because it had multiple distinct surface rupture segments in some places but not in others. By comparing shear stress in these segments, we could figure out how strong the damage zones were. We used real observations and numerical simulations to estimate how much stress these damage zones can withstand. Our results indicate that, for damage zones embedded in intact sandstone with a Young's modulus of 15 GPa, its strength ranges from 7 to 17 MPa. Significantly, our study is the first to reveal the shear strength of damage zone from a nutural earthquake using geodetic data. Key Points: Shear modulus and shear stress for coseismic damage zone were determined using coseismic deformation and finite element modelEstimated shear strength from overlap range of coseismic stress between surface rupture and non‐rupture parts ranges from 7 to 17 MPaShear strength exhibits positive and negative correlations with confining pressure and fault maturity, respectively [ABSTRACT FROM AUTHOR]

Novel halide double perovskites CsKAgSbX6 (X = Cl, Br) have been theoretically investigated in the current study to determine their optoelectronic, elastic, and thermoelectric properties. The Density Functional Theory based on the GGA-PBE and HSE functionals using the Quantum Espresso code was applied. The optimization of the cubic structure of the perovskites resulted in the optimized lattice constants of about 10.78 Å and 11.31 Å for CsKAgSbCl6 and CsKAgSbBr6, respectively. The results also revealed that both materials are stable in the cubic structure and are mechanically stable as well as ductile in nature. The anisotropy of CsKAgSbX6 (X = Cl, Br) has been investigated by evaluating the highest and lowest values of the shear modulus, Bulk modulus, and the Young's modulus. Moreover, the investigation of their electronic properties indicated that they are semiconductors with energy gap values found to be 1.36 eV for CsKAgSbCl6 and 0.87 eV for CsKAgSbBr6 using the GGA approximation and 2.49 eV and 1.81 eV for the respective perovskites using the HSE functional. Regarding their optical properties, these materials show an excellent UV light absorption, low reflectivity and high-power conversion efficiency, making them promising for solar cell applications. Finally, with a reasonably high figure of merit, CsKAgSbX6 (X = Cl, Br) double perovskites also have potential for thermoelectric devices. [ABSTRACT FROM AUTHOR]

The improvement of sandy soils with poor seismic properties to modify their dynamic characteristics is of great importance in seismic design for engineering sites. In this study, a series of dynamic tests on sandy soils sandy soils with poor seismic conditions were conducted using the GCTS resonant column system to investigate the improvements effects of different cement contents on dynamic characteristic parameters. The research findings are as follows: The cement content has certain influences on the dynamic shear modulus, dynamic shear modulus ratio, the maximum dynamic shear modulus, and the damping ratio of sandy soils with poor seismic properties. Among them, the influence on dynamic shear modulus is limited, while the damping ratio is significantly affected. The addition of cement to seismic-poor sandy soils significantly enhances their dynamic characteristics. The most noticeable improvement is observed when the cement content is 8%. Through curve fitting analysis, a relationship equation is established between the maximum dynamic shear modulus and the cement content, and the relevant parameters are provided. A comparative test between the improved soils and the remolded soils reveals that the addition of cement significantly improves the seismic performance of the poor soils. The recommended values for the range of variation of the dynamic shear modulus ratio and damping ratio are provided, considering the effect of improvement. These research findings provide reference guidelines for seismic design and engineering sites. [ABSTRACT FROM AUTHOR]

This study explored the structural stability, elastic properties, structural transformation, and critical concentration of Ni3Al and Ni3M (M = Ti, Ta, Nb) using L12, D024, and DO22 structures, along with three-dimensional supercells featuring stacking faults along [ 10 1 ¯ ] , [ 01 1 ¯ ] , [111] directions. First-principles calculations revealed that the most stable structures for Ni3Al, Ni3Ti, Ni3Ta, and Ni3Nb are L12, D024, DO22, and DO22, respectively. Notably, the bulk modulus, Young′s modulus, shear modulus, and isotropy of Ni3Ti, Ni3Ta, and Ni3Nb surpassed those of Ni3Al, with increased ductility, except for Ni3Ti. By substituting Al atoms with 0–8 Ti, Ta, and Nb atoms in a 32-atom Ni3Al structure, the critical concentration for the transformation from L12 to D024 or DO22 ranged between 18.75 at. % and 21.88 at. %, and between 15.63 at. % and 18.75 at. %, respectively. This critical concentration was influenced by the dynamic interplay among Ti, Ta, Nb, and Al atoms interacting with Ni atoms. The structural transformation from L12 to D024 or DO22 can be attributed to the reduction in the superlattice extrinsic stacking fault energies or the anti-phase boundary energies, respectively, a consequence of the redistribution of charge density between Ti, Ta, Nb atoms and Ni atoms. [ABSTRACT FROM AUTHOR]

[Display omitted] The droplet/bubble adhesion characteristics depend on the length of the droplet/bubble three-phase contact line. Since the deformation caused by the liquid–gas interfacial tension on the soft substrate, referred as to the wetting ridge, retards contact line spreading and retraction, we conjecture that the droplet/bubble adhesion characteristics depend also on the substrate softness. Soft substrates with various shear moduli are prepared and characterized by the spreading and receding dynamics of water droplets and underwater bubbles. Snap-in and normal adhesion forces of droplets/bubbles on such soft substrates are directly measured along with the visualized droplet/bubble shape profiles. The droplet/bubble snap-in force, which corresponds to the short-time spreading dynamics, decreases with a decrease in the substrate shear modulus because of the retarded contact line spreading. The droplet maximal adhesion force on a soft substrate can be counterintuitively either smaller or larger than its counterpart on the rigid substrate depending on different dwelling times, i.e., the droplet/bubble-substrate contact time before droplet/bubble-substrate separation. The former is attributed to the retarded contact line spreading, whereas the latter is attributed to the retarded contact line retraction. The substrate softness- and dwelling time-dependent droplet/bubble adhesion reported in this study will benefit various applications related to soft substrates. [ABSTRACT FROM AUTHOR]

This research aims to evaluate the impact of the initial cell configuration and the limit volume fraction on the generation of mechanical metamaterial cells. The procedure was developed using a methodology based on preprocessing, processing, and post processing to facilitate fast exploration of metamaterial cell space design. The initial cell consisted of a square or cube of material with a central circular or spherical void diameters of 10 mm, 20 mm, and 30 mm. Additionally, the generation process employed three volume fractions limits (30%, 40%, and 50%) and eleven objective functions. These functions intended to generate cells that maximize stiffness in one or multiple directions and cells with maximum compressibility or shear modulus. Some of the obtained cells with tailored mechanical properties exhibit novel geometrical configurations. The results highlight volume fraction as the most significant factor in the generation process, with well-defined metamaterial cells produced using an initial volume fraction of 50% and low to medium void diameters. [ABSTRACT FROM AUTHOR]

Experimental data describing the uniaxial compression and relaxation of brain tissue are compared to the predictions from a rheological model developed by Yarin and Kosmerl ["Rheology of brain tissue and hydrogels: A novel hyperelastic and viscoelastic model for forensic applications," Phys. Fluids 35, 101910 (2023)]. A qualitative agreement between the model and experiments with swine brain tissue is confirmed, and the uniformly valid values (i.e., valid in all rheometric experiments without any change) of the rheological parameters are established. These are the values of the following four parameters: G (the shear modulus), κ (the bulk modulus), α (the dimensionless degree of hyperelasticity), and θ (the viscoelastic relaxation time). In addition, the present rheological model with the established rheological parameters is incorporated into a dynamic model of bullet penetration into brain tissue after a short-range shooting, when muzzle gases and/or air fill the bullet channel leading to its widening, wave propagation, fragmentation, and backspatter of brain tissue. This problem is of significant interest in forensic science because there is an urgent need to provide physics-informed models to reconstruct and analyze crime scenes. [ABSTRACT FROM AUTHOR]

Micropillar compression experiments show size effect, σp/μ = A(d/b)n, where σp, is the flow stress, μ is the resolved shear modulus, d is the pillar diameter and b is Burgers' vector. With fcc metals n ≈ –0.67 and A ≈ 0.7; however, with bcc metals there is greater variation, with n closer to zero. Here we propose a different but similar empirical relation of σp/μ = σb/μ + A'(d/b)n', where σb is a size independent resistance stress. In which case there must be a strong correlation between the original constants, A and n. This hypothesis is found to be true for the published data from a large number of bcc metals, ionic solids that possess the rock salt crystal structure, and some covalent bonded semiconductors. This correlation is shown to predict a universal power law with the exponent in the range, −1.0 < n' < −0.5, and with A' close to 1. These values are very similar to the empirical relation that can be used to describe the behaviour of fcc metals tested in micropillar compression with σb = 0. This universality of the empirical relation provides strong evidence for a common mechanism for the micropillar size effect across a range of materials. [ABSTRACT FROM AUTHOR]

A new formulation of the bismuth-zinc-borate glass system has been fabricated using the conventional melt-quenching method. The amorphous phase of the glass sample has been confirmed by the nonexistent of any crystalline peak presented by X-ray diffraction patterns. The Fourier-transform infrared spectroscopy result displays several bands associated with the Zn–O and B–O–B bonding. The glass samples exhibited a density increase from 3.19 to 4.28 g/cm3 and the molar volume increased from 23.48 to 31.00 cm3/mol. The density of the glasses increases due to the addition of Bi2O3 which has a higher atomic mass compared to the other elements in glass compositions. The addition of Bi2O3 contributes more mass to the glass structure, leading to an increase in overall density. The incorporated Bi2O3 reduced the longitudinal (6134.41–5121.94 ms−1) and shear (3310.50–2848.15 ms−1) velocities. The elastic moduli resulted in a decreasing behavior when Bi2O3 concentration increased, and the values ranged from 120.04 to 112.21 GPa for longitudinal modulus, 34.96–34.69 GPa for shear modulus, 73.43–65.95 GPa for bulk modulus, and 90.52–88.56 GPa for Young's modulus. The Poisson's ratio presents the same trend as the modulus, while the microhardness shows an inversely proportional trend. The BiZnB4 sample demonstrates the lowest Poisson's ratio (0.276) and highest microhardness (5.18 GPa) values. These findings show that the physio-elastic properties are composition-dependent, suggesting potential applications as flexible glass panels for dynamic building glass design. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) magnetic resonance elastography (MRE) is more accurate than two-dimensional (2D) MRE; however, it requires long-term acquisition. This study aimed to reduce the acquisition time of abdominal 3D MRE using a new sample interval modulation (short-SLIM) approach that can acquire all three motions faster while reducing the prolongation of echo time and flow compensation. To this end, two types of phantom studies and an in vivo test of the liver in three healthy volunteers were performed to compare the performances of conventional spin-echo echo-planar (SE-EPI) MRE, conventional SLIM and short-SLIM. One phantom study measured the mean amplitude and shear modulus within the overall region of a homogeneous phantom by changing the mechanical vibration power to assess the robustness to the lowered phase-to-noise ratio in short-SLIM. The other measured the mean shear modulus in the stiff and background materials of a phantom with an embedded stiffer rod to assess the performance of short-SLIM for complex wave patterns with wave interference. The Spearman's rank correlation coefficient was used to assess similarity of elastograms in the rod-embedded phantom and liver between methods. The results of the phantom study changing the vibration power indicated that there was little difference between conventional MRE and short-SLIM. Moreover, the elastogram pattern and the mean shear modulus in the rod-embedded phantom in conventional SLIM and short-SLIM did not change for conventional MRE; the liver test also showed a small difference between the acquisition techniques. This study demonstrates that short-SLIM can provide MRE results comparable to those of conventional MRE. Short-SLIM can reduce the total acquisition time by a factor of 2.25 compared to conventional 3D MRE time, leading to an improvement in the accuracy of shear modulus estimation by suppressing the patient movements. • A new approach to MRE acquisition and processing for fast abdominal 3D elastic imaging. • Technique to reduce the acquisition time of 3D abdominal MRE by a factor of 2.25. • Improvement of accuracy of stiffness estimation by suppressing patient movement. [ABSTRACT FROM AUTHOR]

The structural, elastic, piezoelectric, and electronic properties of Li-doped K0.5Na0.5NbO3 (K0.5−xNa0.5−yLix+yNbO3, KNN-L) are calculated. The properties of KNN-L are related to the Li-doping content and the replaced K or Na atoms. The bulk modulus, the shear modulus, and Young's modulus of KNN-L are mostly higher than those of KNN, and the hardness value increases. The Poisson ratio of KNN-L is lower than that of most KNN, and the ductility is reduced. All doped structures are direct band gap semiconductors. K0.5Na0.375Li0.125NbO3 has the largest piezoelectric charge constant, d33 = 44.72 pC/N, in the respective structures, which is 1.5 fold that of K0.5Na0.5NbO3 (29.15 pC/N). The excellent piezoelectric performance of Li-doping KNN-L was analyzed from the insights of elastic and electronic properties. [ABSTRACT FROM AUTHOR]

• Size-dependent near-surface response of FG elastic layer is investigated. • Size effects induced by material microstructures are modeled by couple stress elasticity theory. • Solution of surface loaded layer is derived in closed-form via Fourier transform method. • Efficient numerical scheme is implemented for layer under frictionless contacts. • Effects of length scale and model's parameters on contact response are highlighted. This paper focuses on a theoretical examination of the mechanical behavior of elastic layers made of functionally graded (FG) materials. It particularly highlights the impact of material microstructures by utilizing the couple stress theory to introduce FG characteristics of the coating material across the thickness direction, along with size effects. The study distinctively addresses both surface loading and contact problems, employing various indenter shapes and eccentric indentation forces. The Fourier transform is utilized to solve for displacements and stress fields resulting from surface tractions. The method for approximating the pressure distribution under the indenter is based on a collocation method with a simple discretization of the contact pressure. Brent's method is applied to determine the unknown contact region when using indenters with non-sharp edges. The results demonstrate that the shear modulus ratio and the intrinsic material length scale significantly influence the pressure intensity, highlighting a substantial dependence on the mechanical properties of materials under indentation force. The research also shows that the effect of the length scale and shear modulus ratio affects the limit eccentricity and tilt angle. The results highlight the necessity of considering both the size effect and material gradation when analyzing FG materials under mechanical stress. [ABSTRACT FROM AUTHOR]

Numerical simulation of the glass molding process and analysis of material viscoelasticity are growing increasingly significant as the research on optical‐device glass molding intensifies. An accurate and efficient analytical algorithm for the shear relaxation modulus in the viscoelasticity characterization of glass was developed in this study. We measured the high‐temperature creep curve, friction coefficient, and elastic modulus of glass (D‐LaF50) according to the requirements for viscoelasticity characterization. The viscoelastic behavior of glass was characterized based on the analytical algorithm and test results. A finite element analysis model was developed to verify the accuracy of the analytical algorithm. The results show that the error of the proposed algorithm's numerical simulation compared to the test results is within 5%. [ABSTRACT FROM AUTHOR]

The transplantation of seedlings represents a pivotal stage in plug tray seedling cultivation. Conventional end effectors used in transplanters are primarily tailored for seedlings with well-established root systems and tightly bound substrates. However, when the substrate lacks sufficient root wrapping and remains loose, independent seedling removal devices utilising blowing or suction methods are often employed. This results in structural complexity and increased costs for the transplanter. To address the challenge of grasping loose substrate, this study advocates for a novel approach utilising a diagonal oblique-insertion type end effector. Through repose angle trials, discrete element simulation parameters were calibrated. Subsequently, leveraging these calibrated simulation parameters, the end effector was optimisation through orthogonal experiments. Findings reveal that the relative error between simulated and actual repose angles is minimised under specific conditions, with the shear modulus at 8.2 × 106 Pa, the particle-particle rolling friction coefficient at 0.234, the particle-steel static friction coefficient at 0.36, and the JKR surface energy at 0.347 J m−2. Employing these simulation parameters for end effector optimisation, it was determined that the average substrate integrity rate reaches 79.26% with an end effector featuring 5 tines, a gripper positioned 2.5 mm from the edge of the hole, and a gripper ascent speed of 0.056 m s−1. The average relative error between actual grasping experimental and simulation results was observed at 10.21%, indicating the suitability of these discrete element parameters for optimising simulations of end effectors for transplanters. Furthermore, the end effector devised in this study demonstrated efficacy in transplanting loose substrates. • A diagonal oblique-insertion type end effector was designed. • Calibration of discrete element parameters for substrate using repose angle test. • Optimisation of end effector using discrete element simulation. [ABSTRACT FROM AUTHOR]

This study aims to investigate the mechanical properties of paretic and healthy plantar flexor muscles and assesses the spatial distribution of stiffness between the gastrocnemius medialis (GM) and lateralis (GL) during active force generation. Shear wave elastography measurements were conducted on a control group (CNT, n=14; age=59.9±10.6 years; BMI=24.5±2.5 kg/m2) and a stroke survivor group (SSG, n=14; age=63.2±9.6 years; BMI=23.2±2.8 kg/m2). Shear modulus within the GM and GL was obtained during passive ankle mobilization at various angles of dorsiflexion (P0 =0°; P1=10°; P2=20°; P3=-20° and P4=-30°) and during different levels (30%, 50%, 70%, 100%) of maximal voluntary contraction (MVC). Muscle activations of GM, GL, soleus and tibialis anterior were also evaluated. The results revealed a significant increase in passive stiffness within the paretic plantar flexor muscles under high tension during passive mobilization (p <0.05). Yet, during submaximal and maximal MVC, the paretic plantar flexors exhibited decreased active stiffness levels (p <0.05). A notable discrepancy was found between the stiffness of the GM and GL, with the GM demonstrating greater stiffness from 0° of dorsiflexion in the SSG (p <0.05), and from 10° of dorsiflexion in the CNT (p <0.05). No significant difference in stiffness was observed between the GM and GL muscles during active condition. Stroke affects the mechanical properties differently depending on the state of muscle activation. Notably, the distribution of stiffness among synergistic plantar flexor muscles varied in passive condition, while remaining consistent in active condition. [ABSTRACT FROM AUTHOR]

A series of shaking table tests were performed on reduced-scale models of helical soil-nailed walls (HSNWs) to evaluate the effect of the nail arrangement and nail inclination on the failure mechanisms and dynamic characteristics of this type of retaining structures under seismic conditions. The results of particle image velocimetry (PIV) showed that the potential failure surfaces in the helical soil-nailed walls were parabolic ones with an inflection point and the dimensions of failure wedge increased as the length and inclination of the nails increased. A combination of overturning and base sliding was identified as the predominant deformation mode in the HSNWs and that base sliding faded with an increase in the nail inclination. It was found that horizontal helical nails located in the lower half of the wall played a more effective role in reducing lateral displacement, but the opposite was true for HSNWs with inclined nails. The use of inclined nails instead of horizontal ones was found to be an efficient solution for increasing the shear modulus in HSNWs. The efficiency of this solution decreased with the use of shorter nails in the upper half of the walls and was eventually minimized by increasing the length of the nails across the wall height. It was found that, although the use of helical nails instead of grouted ones reduced wall damping, it could be a good solution for increasing the stiffness of the soil-nailed walls. [ABSTRACT FROM AUTHOR]

The empirical expressions for predicting the small-strain shear modulus (G0) of granular soils in current engineering practice are established mainly on experimental data under isotropic stress conditions. In most geotechnical applications, however, soils are subjected to anisotropic stress conditions. The impact of stress anisotropy on G0 is a critical concern but is not yet fully understood. In this paper, we present a specifically designed experimental study to address the question. Various principal stress ratios were applied to isotropically consolidated sand specimens in a triaxial apparatus, and the elastic shear waves were generated by the bender elements installed in the apparatus such that the variations of G0 from isotropic stress states to anisotropic stress states were determined. Three quartz sands with different particle shapes were tested under a range of states in terms of void ratio, axial stress, and radial stress. The study shows that the impact of stress anisotropy is much more complicated than commonly thought. It depends on the magnitude of the stress ratio and the loading mode. A simple model that accounts for two primary mechanisms associated with the impact of stress anisotropy is proposed, and its performance is evaluated using various sources of data in the literature. [ABSTRACT FROM AUTHOR]

In recent years, several empirical and semiempirical relationships have been proposed to predict the small-strain shear modulus of unsaturated fine-grained soils along different hydraulic and mechanical loadings paths. However, a major deficiency of these relationships is the absence of a coupled linkage between hydraulic and mechanical processes that occur in unsaturated conditions. Specifically, the void ratio and effective stress are considered uncoupled, and changes in soil volume are rarely considered when implementing soil water retention curves in these equations. This study aims to address these deficiencies by discussing the coupled effect of hydraulic and mechanical processes in unsaturated soils and presenting a semiempirical model to predict the small-strain shear modulus, Gmax , of unsaturated low plasticity soils subjected to volume and effective stress changes along different mechanical and hydraulic stress paths. Predictions from this model and three other recently proposed models in the literature are compared with experimental results obtained from a series of suction-controlled bender element tests on silty soil specimens to validate the proposed model. The comparison reveals that the model proposed in this study provides more consistent predictions of the small-strain shear modulus during hydraulic hysteresis, as well as different paths of loading and unloading. [ABSTRACT FROM AUTHOR]

This study investigated the effect of gradation, especially of mean particle size and uniformity of gradation, on the shear modulus degradation of natural marine sands compared to regraded clean sands. A series of fixed-free resonant column tests were performed on graded clean sands and marine sands having similar uniformity coefficient values, Cu. It is observed that the modulus degradation of both clean sands and marine sands increased with the increase in Cu. However, the marine sands have degraded less than clean sands for the same Cu and effective confining stress. The reasons can be attributed to the nonlinearity in the grain size distribution of marine sands above 60% finer and mean particle size, D50 , compared to graded clean sands. The overestimation of the modulus degradation of marine sands by the existing empirical equations is demonstrated. Considering the effects of uniformity coefficient, Cu , and mean particle diameter, D50 , a generalized calibrated modulus degradation model for a wide range of clean sands and marine sands is proposed with a high coefficient of determination. Good agreement is demonstrated between the estimated and experimental data from the literature. [ABSTRACT FROM AUTHOR]

Context: Based on first principles, the structure, elasticity, mechanics, electronics, and optical properties of cubic K2Pb2O3 were studied. The structural parameters calculated by this method are close to the previous theoretical results. The elastic constant, bulk modulus, shear modulus, Young's modulus, Poisson's ratio, and mechanical stability are studied, and it is shown that cubic K2Pb2O3 is mechanically stable, isotropic, and brittleness. The electrical conductivity and chemical bonding of cubic K2Pb2O3 were analyzed based on the calculated band structure, density of states (DOS), and bond populations. The dispersion of optical functions, including the dielectric function, refractive index, extinction coefficient, reflectivity, absorption coefficient, and loss function, is displayed and analyzed. Methods: All computations have been carried out based on density functional theory (DFT) as implemented in the CASTEP code. The norm conservation pseudopotential method is used to exchange correlation functionals within the generalized gradient approximation (GGA). [ABSTRACT FROM AUTHOR]

A systematic analytical study of the mathematical properties of the previously constructed nonlinear model for shear flow of thixotropic viscoelastic-plastic media is continued. For arbitrary six material parameters and an (increasing) material function that control the model, the basic properties of the families of stress-strain curves at constant strain rates and relaxation curves generated by the model, and the features of the evolution of the structuredness under these types of loading are analytically studied. The dependences of these curves on time, shear rate, initial strain and initial structuredness of the material, as well as on the material parameters and function of the model, are studied. Several indicators of the applicability of the model are found which are convenient to check with experimental data. It was examined what effects typical for viscoelastic-plastic media can be described by the model and what unusual effects (unusual properties) are generated by a change in structuredness in comparison with typical stress-strain curves and relaxation curves of structurally stable materials. In particular, it has been proved that stress-strain curves can be both increasing functions and can have decreasing sections resembling a "yield tooth" or damped oscillations, that all stress-strain curves (SSCs) possess horizontal asymptotes (steady flow stress), monotonically dependent on shear rate, and flow stress increases with shear rate growth, that the instantaneous shear modulus, on the contrary, depends on the initial structuredness, but does not depend on shear rate. Under certain restrictions on the material parameters, the model is also capable of providing a bilinear form of stress-strain curves, which is typical for an ideal elastoplastic model, but with strain rate sensitivity. It has been established that the family of stress-strain curves does not have to be increasing either in initial structuredness or in shear rate: in a certain range of shear rates, in which the equilibrium position is a "mature" focus and pronounced oscillations of stress-strain curves are observed, it is possible to intertwine stress-strain curves with different shear rates. It is proved that for any material parameters and functions, all stress relaxation curves decrease and have a common zero asymptote as time tends to infinity. The analysis proved the ability of the model to describe behavior of not only liquid-like viscoelastoplastic media, but also solid-like (thickening, hardening, hardened) media: creep, relaxation, recovery, a number of typical properties of experimental relaxation curves, creep and stress-strain curves, strain rate and strain hardening, flow under constant stress and so on. [ABSTRACT FROM AUTHOR]

The asphalt binder is exposed to unfavorable coupling aging of UV radiation, high temperature, and moisture, which accelerates the deterioration of the binder's rheological properties. To investigate the effect of this coupled aging on the rheological properties of asphalt binder, an accelerated environmental aging oven considering ultraviolet (UV) radiation, temperature, and moisture was used in this paper to carry out multifactor coupling aging tests for the binder. The coupling aging test parameters are determined by the central composite design-response surface methodology (CCD-RSM). The rheological properties of asphalt binder before and after aging were examined by dynamic shear rheometer, and the effects of the coupling aging on the viscoelastic, high-temperature, fatigue, and low-temperature properties of the binders were evaluated by employing the complex shear modulus (G*); the aging index (GI), which was established with G* ; the rutting factor (G*/sinδ); the Glover–Rowe (G-R) parameter; and the ratio of asphalt binder creep rate to stiffness modulus (m/S), respectively. Further, the effect of the coupling aging on the chemical properties of the asphalt binder was evaluated with carbonyl index obtained from the Fourier transform infrared spectrometer. The results showed that the optimal values (temperature: 68.3°C; irradiation intensity: 2,221 W/m2 ; spraying interval: 250 min) of the coupled aging parameters were determined by the CCD-RSM, and the relationship between the coupled aging time and the carbonyl index was established by the Verhulst model with an R2 value larger than 0.98. As the coupling aging degree increases, the G* , GI , and G*/sinδ show an increasing trend, whereas the G-R parameter, m/S , shows a decreasing trend, indicating that the aging increases the stiffness and high-temperature resistance of the binder and decreases its fatigue properties and low-temperature properties. Based on the correlation analysis, the G-R parameter showed good correlation with the GI , G*/sinδ (45°C, 55°C, and 65°C), m/S (−6°C , −12°C , and −18°C), respectively, and the average R2 value is larger than 0.98. Therefore, the G-R parameter can be used as a comprehensive index for evaluating the rheological properties of binders. [ABSTRACT FROM AUTHOR]

This work deals with the damping and vibration characteristics evaluation of sandwich beams based on higher-order shear deformation theories (HSDT's). The studied sandwich beams are composed of composite materials at faces and homogeneous, isotropic viscoelastic material in the core layer. This latter (viscoelastic material) is described by complex Young's modulus in the frequency domain. Indeed, the real part represents the stiffness, and the imaginary one describes the damping property. Nonlinear damping parameters and frequency curves are obtained using the nonlinear equation of frequency amplitude governed by multiple complex coefficients. In conjunction with a one-mode Galerkin's procedure, the harmonic balance method is employed to obtain the nonlinear loss factor and the response frequency curves. The nonlinear frequency value and, in turn, the system loss factor ratio are obtained for various amplitudes to examine the impacts of the ply angle of fiber-reinforced composite faces, the viscoelastic shear modulus, the shear deformation model, for considering different geometric and material parameters. In the framework of this study, one attempt is to describe a better way to achieve satisfactory passive vibration control of the laminated beams. [ABSTRACT FROM AUTHOR]