Elastic Shear Modulus Research Articles

New Insight into Elastic Mechanical Properties and Anisotropies of Crystal Defect α-Quartz from DFT Calculation.

To reveal the cleavage mechanism of α-quartz in the grinding process of nonferrous metal ores, mechanical and charge properties of α-quartz crystals are investigated using the density functional theory. Based on the elastic constant matrix, the bulk and shear moduli were calculated before and after the α-quartz with oxygen atom defects. The results show that the ratios of bulk and shear moduli (B/G) were 0.87 and 0.95, respectively, which indicated that at the same stress level, it was easier to fracture without O-vacancy defects than with O-vacancy defects. The mapping surfaces indicated that the O-vacancy defect increased the bulk-, shear-, and Young's moduli, and Poisson ratio while decreasing the hardness. The anisotropy index (AL and AU) was calculated which illustrated that the O-vacancy can result in an increased anisotropy; meanwhile, the bulk anisotropy index (AB) increased strongly about two times. The anisotropy analysis shows the dominance crystal cleavage of the (011) plane in the shear stress and the dominance crystal cleavage of the (111) plane in the normal stress. The electron localization function α-quartz show that the O-vacancy defect can decrease the Si-Si length from 3.703 to 2.442 Å, which indicated that the O-vacancy formed the new covalent bonds between silicon atoms. Our work provided a systematic approach containing the mechanical, anisotropic, and electronic properties of mineral crystals to explain the cleavage behavior of crystals.

Metamaterial design and continuously adjustable mechanical properties based on novel planetary gear trains

Mechanical metamaterials have been pursuing as valuable properties attribute to the unique internal architecture, but are generally limited to the predetermined properties after manufacturing, resulting in the inability to continuously change the properties during application. Aiming for the continuously adjustable property under environments with high reliability requirements, this research developed two types of mechanical metamaterials based on planetary gear train. The principle of continuously adjustable mechanical property and dynamic characteristics of metamaterial based on planetary gear train is researched though a theoretical model of curved beam under varying radial load. Further, mechanical metamaterials based on double-layers planetary gear (DLPG) train and Ravigneaux planetary gear (RPG) train are designed. The compressive elastic modulus, shear modulus, and amplitude-frequency response are calculated and investigated with finite element simulation. The results, with an adjustable range respectively within 9–15 times and 2–3 times in compressive elastic modulus of and shear modulus, show a good agreement between the theoretical and simulated results, and illustrate the adjustability and reliability of the mechanical metamaterials based on planetary gear train. Finally, the potential configurations and applications of metamaterial based on planetary gear train are presented.

Acute and Chronic Effects of Static Stretching on Neuromuscular Properties: A Meta-Analytical Review

The aim of this review was to provide an overview of the recent findings on the acute and chronic effects of static stretching on joint behaviors and neuromuscular responses and to discuss the overall effects of acute and chronic static stretching on selected outcomes via meta-analyses, using a total of 50 recent studies. The results of our meta-analyses demonstrated that acute static stretching results in increased range of motion (ROM), decreased passive resistive torque (PRT), increased maximum tolerable PRT (PRTmax), decreased maximum voluntary isometric torque, decreased muscle–tendon unit stiffness, decreased muscle stiffness, decreased tendon stiffness, and decreased shear elastic modulus. Moreover, the chronic effects of static stretching included increased ROM, increased PRTmax, decreased muscle stiffness, and decreased shear elastic modulus (or shear wave speed). These results suggest that static stretching interventions have the potential to increase ROM and reduce the mechanical properties of muscle–tendon tissue, but they may not change corticospinal excitability and spinal reflex excitability or muscle architecture parameters.

A Thermodynamic Strength Theoretical Model to Explain and Predict Pseudo-Ductility Behavior of SiCf/SiC Composite Material

In order to explain and predict the pseudo-ductility behavior and mechanical properties of [Formula: see text] composite material, a thermodynamic strength theoretical model based on fracture mechanics and thermodynamic method has been established. Compared with other theoretical models, the model proposed in this investigation unifies different cracks and defects based on energy method. Meanwhile, the stress–strain behavior of materials can be obtained with as few parameters as possible. Compared with previous experimental data, the correctness of this theoretical model has been verified. Some key material properties, such as elastic modulus, proportional limit stress (PLS) and yield stress (YS), have been investigated by calculating based on the theoretical model. The effect of the initial matrix porosity and the material properties of the matrix and fiber have been investigated. Results show that PLS and YS are almost not influenced by initial matrix porosity and can be seen as intrinsic parameters. Elastic modulus of the SiC reinforced fiber and the matrix can also affect material properties. Compared with the SiC matrix, PLS of the [Formula: see text] composite material is more sensitive to changes in elastic modulus of the SiC reinforced fiber. However, the improvement of elastic modulus and shear modulus of the [Formula: see text] composite material is much more difficult. For this purpose, the elastic modulus of both the SiC reinforced fiber and the matrix need to be enhanced. Results and conclusions in this investigation can provide guidance for predicting material properties of [Formula: see text] composite material and preparation in industry.

Rheological response of ferrofluids undergoing unsteady shear flows in the presence of a magnetic field

The rheological response of two commercial ferrofluids to transient shearing flows using a parallel disk rheometer device equipped with a magnetic cell is investigated. The basic difference between the ferrofluids is their volume fraction of magnetic particles. The first transient shear flow examined is a step-strain under the influence of a magnetic field, from which the stress relaxation functions for both magnetic fluids studied are obtained in terms of the magnetic field strength and the intensity of the step strain. The main relaxation times of both fluids are determined and shown to increase with the applied magnetic field parameter after some critical value. We also observed that the shear stress relaxes to a residual stress, which is strongly dependent on both magnetic field and strain strengths. This remarkable residual stress increases as the intensity of the magnetic field rises. In terms of the strain strength, this residual stress is found to have two interesting behaviors. First, for small values of strain, the residual stress increases linearly until a maximum is reached. Further increases in the strain strength lead to a nonlinear decrease in the residual stress. We conjecture that the linear regime is associated with a predominance of elastic deformation of the fluid microstructure while the nonlinear one to its plastic deformation or even to the structure breakup. The second experimental investigation of the magnetic fluids is carried out under the condition of oscillatory shear in a linear viscoelastic regime and in the presence of an applied magnetic field. The main viscoelastic moduli of the ferrofluids as functions of the non-dimensional frequency and the magnetic field intensity are presented. In addition, it is also shown, for both ferrofluids, that viscous and elastic characteristics are severely increased when the applied magnetic field intensity is enhanced. We also determine the shear elastic modulus for both magnetic fluids in the limit of low Deborah number as a function of the magnetic parameter. Compatibility checks between the viscous modulus and the apparent shear viscosity under conditions of the same frequency and shear rate are performed, and the first normal stress difference is calculated.

Load sharing between synergistic muscles characterized by a ligand-binding approach and elastography

The skeletal muscle contraction is determined by cross-bridge formation between the myosin heads and the actin active sites. When the muscle contracts, it shortens, increasing its longitudinal shear elastic modulus ({mu }_{L}). Structurally, skeletal muscle can be considered analogous to the molecular receptors that form receptor–ligand complexes and exhibit specific ligand-binding dynamics. In this context, this work aims to apply elastography and the ligand-binding framework to approach the possible intrinsic mechanisms behind muscle synergism. Based on the short-range stiffness principle and the acoustic–elasticity theory, we define the coefficient C, which is directly related to the fraction saturation of molecular receptors and links the relative longitudinal deformation of the muscle to its {mu }_{L}. We show that such a coefficient can be obtained directly from {mu }_{L} estimates, thus calculating it for the biceps brachii, brachioradialis, and brachialis muscles during isometric elbow flexion torque (τ) ramps. The resulting Cleft(tau right) curves were analyzed by conventional characterization methods of receptor–ligand systems to study the dynamical behavior of each muscle. The results showed that, depending on muscle, Cleft(tau right) exhibits typical ligand-binding dynamics during joint torque production. Therefore, the above indicates that these different behaviors describe the longitudinal shortening pattern of each muscle during load sharing. As a plausible interpretation, we suggested that this could be related to the binding kinetics of the cross-bridges during their synergistic action as torque increases. Likewise, it shows that elastography could be useful to assess contractile processes at different scales related to the change in the mechanical properties of skeletal muscle.

Impact Elastohydrodynamic Lubrication Analysis of Transversely Isotropic Materials in Point Contact

Abstract In the traditional elastohydrodynamic lubrication (EHL) field, surface elastic deformation is usually determined using an elastic half-space model for isotropic materials. However, this theory may be inefficient when applied to point contact problems involving inherently anisotropic materials, such as transversely isotropic (TI) materials. Accordingly, the present study proposes a method for solving the EHL point contact problem between a rigid ball and a TI substrate under impact loading using a direct-solving numerical method, in which the mechanical properties of the TI material are expressed in the form of a stiffness matrix. For comparison purposes, the TI material is also approximated as an isotropic material using Turner’s approximation method based on the equivalent modulus property of the material. It is found that the direct-solving method outperforms Turner’s approximation in interpreting the mechanical properties of the TI substrate. In addition, it is shown that the initial velocity of the rigid ball and the stiffness of the TI material (i.e., the transverse elastic modulus, longitudinal modulus, and shear modulus) have significant effects on the load, impact velocity, and acceleration of the ball; central pressure and film thickness of the lubricant; and deformation and von Mises stress of the TI substrate, during the impact process. Overall, the results show that the proposed EHL model provides a useful tool for solving impact-EHL problems involving TI materials.

Short-time frequency-domain method for truly nonlinear dynamic ground response analysis: The equivalent-nonlinear approach

Evaluating soil nonlinearity during cyclic loading is one of the most significant challenges in ground response analysis, especially when dealing with the inverse problem of deconvolution. Different schemes have already been developed for dynamic ground response analysis, both in the time and the frequency domain. The most accurate method to account for soil nonlinearity is the nonlinear dynamic analysis in the time domain. This approach is based on nonlinear constitutive models capable of accurately simulating highly nonlinear problems like soil liquefaction. However, the time-domain analysis is suitable only for the convolution analysis to define the ground motion at the free surface of a soil deposit from the bedrock motion. The frequency-domain analysis is the most common solution for the inverse problem called deconvolution, which is used to define the bedrock motion from the free surface ground motion. A well-known approach developed in the frequency domain for ground response analysis is the equivalent-linear method (EQL). This approach adopts an iterative procedure to define elastic shear modulus and damping ratio compatible with the induced strain level. Still, it presents some limitations, especially for highly nonlinear soil response, due to the use of strain-compatible but constant soil properties. This article presents a new scheme to conduct truly nonlinear dynamic analysis in the frequency domain based on the new concept of the short-time transfer function. Unlike the EQL method, which uses a constant transfer function, the proposed approach, called the “Equivalent-Nonlinear” method (EQNL), defines a soil transfer function evolving in time, depending on the shear stress and strain demands. The EQNL method approximates the response of a nonlinear system as an incrementally changing viscoelastic system and could represent a valuable tool for nonlinear deconvolution. This article shows the analytical formulation and the first set of validations of the EQNL approach, with detailed comparisons with the EQL and NL methods and vertical array data. These comparisons show the potentialities of the EQNL approach to reproduce the results of the nonlinear dynamic analysis. The EQNL approach has been implemented in MATLAB, and the source code is provided as supplementary material for this article. A more comprehensive validation is underway, aiming to better characterize the limitations and the capabilities of the method.

Molecular simulation on compatibility and mechanisms of SBS and PTW polymer modifiers in asphalt binder.

Ultrathin overlays are preventive maintenance measures; the tensile and shear stresses generated inside a structural layer under vehicle load are greater than those of conventional thickness asphalt pavement. Therefore, asphalt binders must use high-viscosity and elasticity unique cementing materials to ensure stability. To investigate the modification mechanism of styrene-butadiene-styrene (SBS)/ethylene-butyl acrylate-glycidyl methacrylate copolymer (PTW) high-viscosity modified asphalt binder suitable for ultrathin overlays, the compatibility and molecular behavior of SBS/PTW high-viscosity modified asphalt binder were analyzed by the molecular dynamics (MD) method. These research results provide a reference for preparing ultrathin overlay high-performance composite modified asphalt binder. SBS molecular models, PTW molecular models, asphalt binder molecular models, SBS/asphalt binder blend systems, and SBS/PTW/asphalt binder blend systems were sequentially constructed using Materials Studio (MS) software. The compatibility of SBS, PTW, and SBS/PTW with asphalt binder and the diffusion coefficients of SBS, PTW, and SBS/PTW in the asphalt binder were investigated separately using the MD method. The mechanical properties and molecular behavior of SBS, PTW, and SBS/PTW blended with asphalt binder were studied. The research results indicate that the compatibility of PTW with asphalt binder is better than that of SBS with asphalt binder. PTW can effectively decrease the solubility parameter of asphalt binder and improve the compatibility between SBS and asphalt binder. PTW effectively improves the diffusion coefficient and interaction energy of SBS in asphalt binder by up to 29% and 83%. In addition, SBS/PTW had a significant positive effect on the mechanical properties of the asphalt binders, increasing the elastic modulus (E), bulk modulus (K), and shear modulus (G) of the asphalt binder by 4.6%, 9.5%, and 3.5%, respectively, compared to SBS. The results indicate that the SBS/PTW modified asphalt binder composite can significantly improve the high-temperature shear resistance of asphalt binder. Meanwhile, SBS and PTW improve the self-aggregation behavior between asphalt binder component molecules. The distance between the center of mass of asphalt binder and resin system molecules is increased. PTW enhances the extensibility of the branched chains of asphalt binder component molecules and improves the interaction between asphalt binder components and the chains. This further enhances the density and stability of the asphalt binder molecular structure system, improving the physical properties of the asphalt binder.

Correlation between the shear modulus measured by elastography (SSI) and tangent modulus from tensile tests of in vitro fresh-frozen human tendons

Assessing the mechanical properties of tendons in vivo allows for quantifying the degree of pathology and tracking functional improvements. The Supersonic Shearwave Imaging (SSI) technique is a state-of-the-art method for analyzing musculoskeletal tissues in vivo. This technique estimates tissue stiffness as the shear elastic modulus µ [kPa]. However, only a few studies have validated the accuracy of SSI-estimated shear modulus against the gold standard for in vitro material testing, the tensile test. This study compared the SSI-measured shear elastic modulus (µ) with the tangent modulus (Etan) obtained from mechanical tensile tests for human Achilles (AT) and patellar tendons (PT). The sample comprised eleven fresh-frozen human Achilles tendons and five fresh-frozen human patellar tendons from cadavers that were not degraded by formalin or ionizing radiation. The tendons were tested in a tensile machine, and elastography videos were collected and segmented every 5% of the total experiment time. The absolute µ values estimated from both instruments presented an up to 20-fold difference. However, a strong significant positive correlation was found between µ and Etan for both tendons (range AT: R = 0.9765–0.9972 and PT: R = 0.8719–0.9782). The two resulting curves (µ and Etan) as a function of strain (ε) were normalized by their maxima for visually comparing stiffness × strain profiles. In conclusion, despite the inaccurate absolute values, SSI has been shown to measure relative changes in human Achilles and patellar tendon stiffness. This study endorses future clinical use of SSI to provide in vivo estimations of human tendons’ mechanical properties.

Dynamic test study of twelve elastic constants of larch timber

The elastic modulus, shear modulus, and Poisson’s ratio of timber are the elastic constants characterizing its material properties. In this paper, the transient excitation method was used to dynamically measure the 10 elastic constants of the falling larch wood under the condition of the free board and cantilever board, that is, 3 elastic moduli E, 3 shear moduli G, and 4 Poisson’s ratios μ. The other two Poisson’s ratios μ were derived using the principle of orthogonality. At the same time, the elastic modulus, shear modulus, and Poisson’s ratio under static conditions were tested and verified by symmetrical four-point bending, asymmetrical four-point bending, and tensile methods. This study is expected to have good application value and practical significance for timber as an engineering structural material, which is widely used in architecture, decoration, furniture, transportation, musical instruments, and in other fields.

A molecular dynamics study on the mechanical response of thermal-pressure rejuvenated CuxZr100−x metallic glasses

A molecular dynamics study was performed on the mechanical response of thermal-pressure rejuvenated CuxZr100−x metallic glasses. The effect of temperature (50, 300, 600 K) and pressure (0–50 GPa) on the rejuvenation process and the mechanical properties of CuxZr100−x including stress–strain response, shear localization formation and elastic modulus were investigated. The thermal-pressure rejuvenation process involves transitioning the system to a higher potential energy state and a lower atomic volume, demonstrating the significant influence of pressure on rejuvenation. Our findings reveal that increasing pressure at specific temperatures and material compositions results in reduced yield stress and stress drop. They also indicate that with increasing pressure, the system undergoes a transition towards homogeneity, resulting in enhanced ductility compared to its initial amorphous state. Additionally, high temperatures contribute to lower values of Young's, shear, and bulk moduli, as well as decreased yield stress and stress drop. Consequently, the system becomes more homogeneous, promoting rejuvenation. Furthermore, we observed that the final yield strength of the system increases with higher Cu content for all structures at specific pressures and temperatures. The level of rejuvenation is additionally impacted by the amount of Cu, and structures containing varying content of Cu demonstrate varying degrees of rejuvenation. To validate our findings, we utilized Voronoi analysis, which revealed a higher fraction of densely-packed clusters in the samples. Finally, a total of 10 materials properties were calculated and explored using statistical analysis which shows there are different correlations between pressure, temperature and atomic composition with mechanical properties.

Detection of formation and dissociation of CO2 hydrates in fine-sands through acoustic waves

Natural gas hydrates in oceanic and permafrost sediments are considered a future energy resource. Injecting CO2 into these sediments is believed to aid in the safe and efficient extraction of CH4 and the geological sequestration of carbon. The effectiveness of this strategy can be ensured by assessing the formation of CO2 hydrates in the pores of these sediments at in-situ stress conditions by investigating their elastic properties (viz., compressional and shear wave velocities, elastic modulus, and shear modulus) by resorting to a suitable method such as seismic and/or acoustic logging. However, conducting such a study in field is seldom opted due to the requirement of expensive paraphernalia such as seismic equipment, pressure coring tools, logging while drilling tools, modular dynamic tester, etc. With this in view, efforts were made to synthesize CO2 hydrates in partially saturated fine-sands under triaxial conditions by employing the excess gas method. Ultrasonic wave transducers were employed in tandem to measure the compressional (VP) and shear wave (VS) velocities of the sample, both under formation and dissociation processes. These results have been utilized to propose hydrate formation and dissociation models which encompass three phases each. The rapid reduction in VP and VS observed during thermal dissociation indicates loss of cementation between the sand grains and hydrates, and commencement of hydrate dissociation at their interface. It has been demonstrated that the induction time for CO2 hydrate formation increases, and the water-to-hydrate conversion ratio decreases, with an increase in the initial volumetric water content. Further, the results generated in the present study were compared vis-à-vis those available in the literature for CH4 and CO2 hydrate-bearing sediments (HBS) and it has been found that both VP and VS of the CO2- and CH4- HBS are comparable for a given hydrate saturation.

Neuromuscular and Metabolic Responses during Repeated Bouts of Loaded Downhill Walking.

The aim of this study was to compare vastus lateralis (VL) and rectus femoris (RF) muscles for their nervous and mechanical adaptations during two bouts of downhill walking (DW) with load carriage performed 2 wk apart. Moreover, we investigated cardiometabolic and perceived exertion responses during both DW bouts. Seventeen participants performed two 45-min sessions of loaded DW (30% of body mass; slope, -25%; speed, 4.5 km·h -1 ) separated by 2 wk. Rating of perceived exertion, cost of walking, heart rate, and EMG activity of thigh muscles were assessed during the DW. Muscle shear elastic modulus ( μ ) of RF and VL were assessed before each exercise bout. Maximal voluntary contraction torque was assessed before (PRE), immediately after (POST), and 24 and 48 h after the two exercise bouts. Maximal voluntary contraction torque decreased from POST (-23.7% ± 9.2%) to 48 h (-19.2% ± 11.9%) after the first exercise (Ex1), whereas it was significantly reduced only at POST (-14.6% ± 11.0%) after the second exercise (Ex2; P < 0.001). Rating of perceived exertion (Ex1: 12.3 ± 1.9; Ex2: 10.8 ± 2.0), heart rate (Ex1: 156 ± 23 bpm; Ex2: 145 ± 25 bpm), cost of walking (Ex1: 4.5 ± 0.9 J·m -1 ·kg -1 ; Ex2: 4.1 ± 0.7 J·m -1 ·kg -1 ), and RF EMG activity (Ex1: 0.071 ± 0.028 mV; Ex2: 0.041 ± 0.014 mV) were significantly decreased during Ex2 compared with Ex1 ( P < 0.01). RF μ was significantly greater in Ex2 (0.44 ± 0.18) compared with Ex1 (0.56 ± 0.27; P < 0.001). The RF muscle displayed specific mechanical and nervous adaptations to repeated DW bouts as compared with VL. Moreover, the muscle adaptations conferred by the first bout of DW could have induced greater exercise efficiency, inducing lesser perceived exertion and cardiometabolic demand when the same exercise was repeated 2 wk later.

Characterization of the viscoelastic properties of in vitro crystalline lens samples using ultrasound elastography

With aging, the stiffening of the crystalline lens [K. R. Heys et al., Mol. Vision 10, 956 (2004); R. F. Fisher, J. Physiol. 212(1), 147–180 (1971)] can hinder accommodation and reduce near-vision in more than 75% of individuals above 40 year old [T. R. Fricke et al., Ophthalmology 125(10), 1492–1499 (2018)], an impairment known as presbyopia. Mapping lens elasticity using shear wave elastography holds significant promise for monitoring potential treatments for presbyopia. However, because of the transparency of the lens to ultrasound, the tracking of waves can be performed only on its boundaries. The goal of this study is to characterize the viscoelastic properties of in vitro crystalline lens samples with a curvilinear harmonic method based on noise correlation algorithms. This procedure consists of precise measurements of the dispersion of surface waves across a large frequency range (0.1–3.5 kHz), thus allowing for clear identification of the wave properties needed to correctly estimate the elasticity. The proposed method was applied to gelatin phantoms and excised porcine lens samples. This enabled the observation of two regions in the dispersion curves: a sharp decrease in dispersion at low frequencies (&amp;lt;1 kHz), which was partly due to guided waves, and a smoother slope at high frequencies (&amp;gt;1 kHz), which was attributed to viscoelastic dispersion. In contrast to previous studies, shear elasticity and viscosity moduli were computed at higher frequencies with a Kelvin–Voigt model. If our approach confirms the shear viscosity of lenses, then the shear elastic moduli of lenses are almost an order of magnitude greater than the results of previous studies.

Molecular dynamics simulation of epoxy resin properties at different C=N contents

In response to the green development strategies of countries all over the world, research on degradable epoxy resins has attracted widespread attention. The introduction of reversible covalent bonds in the conventional cross-linked structure of epoxy resins is one of the methods to achieve degradation of epoxy resins, and most researchers use molecular dynamics simulations in their preliminary studies to investigate the feasibility of the introduction of reversible covalent bonding schemes. The purpose of this paper is to investigate the feasibility of introducing C=N into the cross-linked structure of epoxy resins. Four formulation schemes of vanillin-based monoepoxides with the curing agent 4,4′-methylenebis(cyclohexylamine) were designed, and the molecular dynamics simulation method was used to cross-link them. The changes in the cross-linking degree, structural parameters before and after cross-linking, free volume fraction, and C=N content before and after cross-linking were investigated. The effects of different C=N contents on the thermal properties such as glass transition temperature and thermal expansion coefficient, as well as the mechanical properties such as the elastic modulus and shear modulus of this epoxy resin, were investigated. The bond-breaking characteristics of C=N, C–N, and C–O were compared by density of states and differential charge density simulations. Then the degradation mechanism of epoxy resin after the introduction of C=N was illustrated. The results show that as the specific gravity of the curing agent molecule increases, the cross-linking degree tends to increase. The cross-linked model has reduced volume, increased density, decreased energy, and a more stable structure. After crosslinking, the gaps between the segments in the system become smaller, and the fraction of free volume decreases as the proportion of crosslinking agent molecules increases. The C=N content in epoxy resin shows an increasing trend first and then decreases with the increase in the proportion of the curing agent. The glass transition temperature of the material increases with the increase in C=N content, while the coefficient of thermal expansion decreases with the increase in C=N content. The elastic modulus and shear modulus of the material show an increasing trend with the increase in C=N content, with a relatively gradual change in magnitude. Compared with C–N and C–O bonds, the C=N bond is weaker in strength, has a greater polarity, and is more prone to cleavage and degradation.

Molecular simulation on the mechanical and thermal properties of modified insulating paper cellulose doped with trapezoidal polyphenylsesquisiloxane at different temperature

AbstractWith the further development of the transmission and distribution network, the requirements for the insulating system of power equipment are further deepened. As one of the important factors, insulating paper is of great value to improve its performance. The pure cellulose model and trapezoidal polyphenylsesquisiloxane (T‐PPSQ) composite model are established to analyze the mechanical and thermal properties of insulating paper cellulose. The effects of T‐PPSQ doping at different temperature on properties of cellulose are investigated by comparing the radial distribution function, mechanical parameters, glass transition temperature, mean square displacement (MSD), and free volume fraction (FVF) through molecular dynamics method. The results show that T‐PPSQ can improve the ability of cellulose to resist shear stress at different temperatures, showing good mechanical properties. When the temperature is 423 K, the mechanical performance parameters elastic modulus, bulk modulus and shear modulus can be increased by 47.2%, 18.2%, and 38.56% at most. The glass transition temperature of the insulating paper cellulose with T‐PPSQ increases by 64 K, the MSD and the FVF all decrease at different temperature which demonstrated it has improved thermal stability. The research in this paper is of great significance for improving the life of the insulating system of power equipment.

A Study of Molecular Dynamic Simulation and Experimental Performance of the Eucommia Ulmoides Gum-Modified Asphalt.

In recent years, eucommia ulmoides gum (EUG), also known as gutta-percha, has been extensively researched. Molecular dynamic simulations and experiments were used together to look at how well gutta-percha and asphalt work together and how gutta-percha-modified asphalt works. To investigate the gutta-percha and asphalt blending systems, the molecular models of asphalt and various dosages of gutta-percha-modified asphalt were set up using Materials Studio (MS), and the solubility parameters, intermolecular interaction energy, diffusion coefficient, and mechanical properties (including elastic modulus, bulk modulus, and shear modulus) of each system were calculated using molecular dynamic simulations at various temperatures. The findings indicate that EUG and asphalt are compatible, and sulfurized eucommia ulmoides gum (SEUG) and asphalt are more compatible than EUG. However, SEUG-modified asphalt has better mechanical properties than EUG, and the best preparation conditions are 10 wt% doping and 1 h of 180 °C shearing. Primarily, physical modifications are required for gutta-percha-modified asphalt.

Ladderlike Polyphenylsesquioxane‐Doped Cellulose Insulation Paper with Upgraded Mechanical Strength

Ladderlike polyphenylsesquioxane (L‐PPSQ) with special planar ladder structure is significant to upgrade the mechanical strength of cellulose insulation paper. In this study, the effect of different content of L‐PPSQ on mechanical properties and dielectric properties of cellulose is first investigated by molecular simulation, and then insulation paper doped with L‐PPSQ is prepared for experimental verification. It is indicated in the simulation results that the elastic modulus, bulk modulus, and shear modulus of the cellulose are enhanced up to 36.82%, 27.96%, and 41.80%, respectively, when L‐PPSQ is added at 3 wt%, and the cellulose model with 3 wt% L‐PPSQ possesses the lowest dielectric constant. The reason is that L‐PPSQ can enhance the hydrogen bonding network of cellulose, weaken the degree of molecular chain motion, and strengthen the strength of molecular chains, which in turn manifests as the enhancement of mechanical strength. It is shown in the experimental results that the tensile strength and elongation at break of the composite insulation paper can be enhanced by 16.7% and 35.09% when the L‐PPSQ content is 3 wt%, which is consistent with the simulation results. The short‐term aging test shows that L‐PPSQ can also upgrade the mechanical strength of the insulation paper at high temperatures.

Modelling of Inelastic Pentamode-Based Bridge Bearings Using Beam Elements

Metameterials have unique properties, which are mostly attributed to their geometrical configuration. Pentamodes, a subcategory of metamaterials, exhibit an almost zero shear elastic modulus while maintaining high compression stiffness, offering a behavior similar to that of a liquid, suggesting the potential application of pentamodes in seismic isolation. In this paper a real-life bridge bearing, composed of repetitive layers of pentamode unit cells in the horizontal and vertical axes is studied. The lattices are modelled using beam finite elements with an equivalent uniform diameter to ensuring a stiffness equal to that of the bi-cone rod. The importance of the chosen equivalent diameter is shown, as the assumption of an average diameter of the bi-cone may lead to significant discrepancies between the calculated stiffnesses. For small bi-cone diameters difference, and slender formulations, the error could grow up to 15% for the horizontal stiffness and up to 200% for vertical. For thick formulations the average diameter overestimates the horizontal stiffness by 3 times and the vertical by 4. These discrepancies grow exponentially as the bi-cone diameters difference increases. An elastoplastic material is selected. The bearing supporting the superstructure is subjected to a constant vertical weight load and a horizontal shear base load, due to seismic excitation. Under vertical loading plastic hinges are created in all the rods of the cell and bearing. However, under shear loading plastic hinges are rather initially created in the lowest nodes of the cell and the bearing.