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A semi-analytic model is presented universally for the elastic constants and moduli of solid phases in a wide range of temperatures and pressures. We derive in detail the model as a function of temperature and pressure, where the characteristic temperature is clearly associated with the Debye temperature. The abundant experiments of thermal elasticity for Cr–Mn–Fe–Co–Ni high entropy alloys are used to estimate the validity of the characteristic temperature of elasticity. The linear process of the analytical part significantly reduces the high computational and experimental cost of elasticity across a wide range of temperatures and pressures. We take the elastic property of beryllium within the range of up to 6000 K and 500 GPa as a prototype to investigate the accuracy, efficiency and extrapolation of this model. The application to Mg3Al2Si3O12-pyrope and CaSiO3-perovskite in the Earth's mantle further suggests that our model excellently describes the elasticity of different materials across a wide range of temperatures and pressures. [ABSTRACT FROM AUTHOR]

A new study explores the distinct roles of spontaneous polarization and piezoelectric polarization in piezo-phototronic coupling. This investigation focuses on differences in photocatalytic and piezo-photocatalytic performance using sodium bismuth titanate, a key ferroelectric material. The research aims to identify which type of polarization has a greater influence on piezo-phototronic effects. A theoretical assessment complements the experimental findings, providing additional insights. This study explores the enhanced piezo-phototronic performance of electrospun nanofibers compared to sol-gel particles under different illumination conditions (11 W UV, 250 W UV, and natural sunlight). Electrospun nanofibers exhibited a rate constant (k) improvement of 2.5 to 3.75 times, whereas sol-gel particles showed only 1.3 to 1.4 times higher performance when ultrasonication was added to photocatalysis. Analysis using first-principle methods revealed that nanofibers had an elastic modulus (C33) about 2.15 times lower than sol-gel particles, indicating greater flexibility. The elongation of the lattice along the z axis in the case of nanofibers reduced the covalency in the Bi–O and Ti–O bonds. These structural differences reduced spontaneous polarization and piezoelectric stress coefficients (e31 and e33). Despite having lower piezoelectric stress coefficients, higher flexibility in nanofibers led to a higher piezoelectric strain coefficient, 2.66 and 1.97 times greater than sol-gel particles, respectively. This improved the piezo-phototronic coupling for nanofibers. [ABSTRACT FROM AUTHOR]

We study experimentally and theoretically the dynamics of permanent paramagnetic chains and mixed clusters formed by permanent paramagnetic chains and paramagnetic particles under the influence of a time-varying magnetic field. First, we examine the dynamics of permanent chains at high frequencies (∼50 to 1000 Hz). These permanent chains exhibit continuous rotational motion with a frequency several orders of magnitude lower than that of the magnetic field. We develop a theoretical model that accurately describes the dependence of the rotational dynamics of chains on their length, as well as the amplitude and frequency of the external magnetic field in this high frequency regime. Next, we examine how cluster dynamics are affected by the presence of permanent chains. We show that the rotation of clusters composed of a high proportion of permanent chains is slowed down but remains qualitatively well described by the theoretical model we developed for homogeneous clusters of isotropic particles. We propose that the decrease in angular velocity for mixed clusters is due to the hardening of the cluster's 2D elastic modulus caused by the increase of the steric interaction parameter stemming from the presence of chemical links between particles in the chains. [ABSTRACT FROM AUTHOR]

We employed all-atom molecular dynamics simulations to explore the mechanical response of bending, twisting, and overwinding for double-stranded DNA (dsDNA). We analyzed the bending and twisting deformations, as well as their stiffnesses, using the tilt, roll, and twist modes under stretching force. Findings indicate that the roll and twist angles vary linearly with the stretching force but show opposite trends. The tilt, roll, and twist elastic moduli are considered constants, while the coupling between roll and twist modes slightly decreases under stretching force. The effect of the stretching force on the roll and twist modes, including both their deformations and elasticities, exhibits sequence-dependence, with symmetry around the base pair step. Furthermore, we examined the overwinding path and mechanism of dsDNA from the perspective of the stiffness matrix, based on the tilt, roll, and twist modes. The correlations among tilt, roll, and twist angles imply an alternative overwinding pathway via twist–roll coupling when dsDNA is stretched, wherein entropic contribution prevails. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the stress distribution along a premolar's root dentin, its post, and its post-luting agent when materials with different elastic moduli are used to fabricate one-piece post-and-cores in two different designs. Materials and Methods: Two 3D virtual models (for cylindrical and conical post designs) of a mandibular premolar restored with one-piece post-and-core restorations were obtained using a software. A total of eight post-and-core materials were tested: polyetheretherketone (PEEK), polyetherketoneketone (PEKK), glass fiber-reinforced polyetheretherketone (GFR-PEEK), carbon fiber-reinforced polyetheretherketone (CFR-PEEK), gold-palladium alloy (Au-Pd), titanium (Ti), zirconia (Zi), and chromium-nickel (Cr-Ni). Maximum principals stress (MPS) in the post, post-luting agent, and root dentin were determined. A load of 150 N was applied to the buccal cusp in the linguo-labial direction at an angle of 45 degrees oblique to the longitudinal axis of the crown. Results: The highest MPS value in post structure was observed with Cr-Ni material for both post designs. Similarly, the highest MPS value in the post-luting agent was observed for Cr-Ni, the material with the highest elastic modulus. However, in the root dentin, the highest value was observed in PEEK, the material with the lowest elastic modulus. Conclusions: Post material and design influenced the stress concentration in the post, post-luting agent, and root dentin. The stress at the root dentin was slightly higher for polymeric materials. Cylindrical post design revealed lower stresses than conical post design at root dentin for all post-and-core materials tested. [ABSTRACT FROM AUTHOR]

The lattice thermal conductivity stands as a pivotal thermos-physical parameter of high-entropy alloys; nonetheless, achieving precise predictions of the lattice thermal conductivity for high-entropy alloys poses a formidable challenge due to their complex composition and structure. In this study, machine learning models were built to predict the lattice thermal conductivity of AlCoCrNiFe high-entropy alloy based on molecular dynamic simulations. Our model shows high accuracy with R2, mean absolute percentage error, and root mean square error of the test set is 0.91, 0.031, and 1.128 W m−1 k−1, respectively. In addition, a high-entropy alloy with low a lattice thermal conductivity of 2.06 W m−1 k−1 (Al8Cr30Co19Ni20Fe23) and with a high lattice thermal conductivity of 5.29 W m−1 k−1 (Al0.5Cr28.5Co25Ni25.5Fe20.5) was successfully predicted, which shows good agreement with the results from molecular dynamics simulations. The mechanisms of the thermal conductivity divergence are further explained through their phonon density of states and elastic modulus. The established model provides a powerful tool for developing high-entropy alloys with the desired properties. [ABSTRACT FROM AUTHOR]

The motivation of the present study is to gain insights into the evolution of elastic properties of cemented tungsten carbides (WC) shock compressed to 100 GPa. Seven plate impact experiments—two front surface impact and five release wave overtake—are conducted to make simultaneous measurements of Hugoniot states and longitudinal sound speeds in shocked WC with 3.7wt.% cobalt binder. The sound speeds along with estimates for bulk sound speeds, obtained using the Birch–Murnaghan EoS, are analyzed to determine the elastic moduli—longitudinal, bulk, and shear—as a function of Hugoniot stress. The longitudinal and bulk sound speeds at Hugoniot states of interest are found to increase linearly with longitudinal stress. Consistent with the increase in sound speeds, the longitudinal and bulk moduli also increase with Hugoniot stress; however, the increase in longitudinal modulus is modest when compared to predictions of theoretical models that account for pressure and temperature dependence of elastic moduli, but with no damage. The shear moduli remain nearly constant at ∼ 318 GPa over the range of Hugoniot states investigated. These values are, however, much lower than those predicted by the Steinberg–Guinan model with no damage. Poisson's ratio decreases initially from its ambient value of 0.208 to ∼ 0.199 for Hugoniot stress ≤ 10 GPa indicating consolidation of the WC microstructure with low initial stress; however, with an increase in Hugoniot stress to ∼ 100 GPa, Poisson's ratio increases to ∼ 0.317, indicating degradation of shear moduli with increasing stress. The product of density and Grüneisen parameter (ρ Γ), after an initial spike, remains nearly constant for volumetric strains ≥ 0.07. The maximum average temperature rise is estimated to be ∼ 286 ° C at the highest Hugoniot stress employed in the study. [ABSTRACT FROM AUTHOR]

High-pressure treatment of oxide glasses can lead to significant alteration of various material properties such as increased density, ductility, and elastic moduli. In this study, a model of melt-quenched bulk silica glass was subject to high-pressure treatments (up to 16 GPa) using molecular dynamics simulations. The thermal conductivity of such prepared glass structures was determined using the equilibrium Green–Kubo method. We observed that, up to the pressure treatments of ∼ 6 GPa, the structure exhibits moderate density increase and a much steeper increase between 6 and 16 GPa, with associated density increase of fivefold silicon atoms. We also observed a noticeable increase (up to 20%) of the thermal conductivity in samples subjected to high-pressure treatments. The observed increases are somewhat, but not significantly, larger than those predicted by the minimum thermal conductivity model, accounting for density and elastic moduli increase. [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]

Alloying and site ordering play complementary roles in dictating a material's properties. However, deconvolving the impacts of these separate phenomena can be challenging. In this work, we simulate structures of Zn (Sn , Ge) N 2 with varied Sn content and site ordering to determine the impacts of order and composition on structural and electronic properties. We assess the formation enthalpy, lattice parameters, elastic constants, spontaneous polarization, and piezoelectric coefficients. In mostly disordered structures (order parameters ranging from 0.2 to 0.4), the formation enthalpy exhibits local extrema as a function of the order parameter, deviating from the more linear trends seen in both fully disordered and fully ordered systems. This anomalous deviation from the otherwise linear trend in formation enthalpy with order manifests in each of the other properties calculated. This range of order parameters of interest may be caused by a transition in the ordering of the quaternary material similar to phase changes seen in ternary compounds but stretched over a region inclduing 20% of the order parameter range. Most parameters calculated are more sensitive to order than to composition in the limited composition range tested; however, the lattice parameter c , piezoelectric coefficient e 33 , and elastic moduli C 12 , C 13 , and C 23 are more sensitive to composition. Of the properties compared, the piezoelectric coefficients are influenced most significantly by changes in both the composition and order parameter. Lattice parameters undergo the smallest changes with order and composition, but these small differences appear to impart large trends in the other properties. Better understanding the effects of disorder and group IV alloying in Zn (Sn , Ge) N 2 allows for more accurate modeling of characteristics of this material system for solid state lighting and other applications. [ABSTRACT FROM AUTHOR]

Many researchers observed enhanced water flow through carbon nanotubes (CNTs) and attributed the reason to large slips. Even after taking significant slip effects into account, there remain unaddressed observations of significant improvements in flow rates. As CNTS are deformable, we represent nanotubes with a deformable-wall using a linear pressure–area relationship. We assume lubrication assumption, and using the properties of nanoconfined water, we derive the model for deformable-nanotubes. We validated our derived model in its limiting cases with the previously reported results in the literature. We compare the predictions by our deformable-wall and rigid-wall model with the experimental results and the MD-simulation predictions by multiple literature studies. Many studies were well-predicted by the rigid-wall model with slips. However, we find that there are many studies with high porosity and thin wall tubes, where elasticity or deformability of the tube is essential in modeling, which is well-predicted by our deformable-wall model with slips. In our study, we focus on investigating the impact of two key factors: the deformability, and the slip length on the flow rate. We find that the flow rate inside the tube increases as the deformability increases or the thickness T and elastic modulus E of the tube-wall decrease). We also find that the flow rate in deformable tubes scales as m ˙ deformable ∼ 1 / α 0 for (Δ p / α A o ) ≪ 1 , m ˙ deformable ∼ 1 / α for (Δ p / α A o ) ∼ O (10 − 1) and m ˙ deformable ∼ α 2 for (Δ p / α A o ) ∼ O (1). Further, for a given deformability, the percentage change in flow rate in the smaller diameter of the tube is much larger than the larger diameter. As the tube diameter decreases for the given pressure, Δ m ˙ / m ˙ increases. We find that for rigid-tube, the flow rate varies m ˙ rigid ∼ Δ p , whereas for the deformable-tubes, the flow rate scales as m ˙ deformable ∼ Δ p 2 for (Δ p / α A o ) ∼ O (10 − 1) , and finally to m ˙ deformable ∼ Δ p 3 for (Δ p / α A o ) ∼ O (1). We further find that slip also significantly increases flow rate, but, deformability has more substantial effect. [ABSTRACT FROM AUTHOR]

This study uses molecular dynamics simulations to explore the mechanical behavior of a CoCrCuFeNi high-entropy alloy (HEA) with Σ5 and Σ13 grain boundaries (GBs) as well as without GBs and dislocation. The analysis focused on understanding the influence mechanisms of these grain boundaries on the mechanical behavior of the HEA. Our findings reveal that the atomic size disparity among the constituent elements induces lattice distortion, leading to deformation in HEAs. The determined elastic constants met Born stability requirements, ensuring mechanical stability across both the examined GBs. Higher elastic moduli were associated with increased strength and stiffness, particularly evident in HEAs with Σ5 GB, surpassing those of non-GB structures. Notably, GB Σ5 demonstrated enhanced strength and hardness, indicated by larger elastic moduli compared with those of non-GB structures. Conversely, GB Σ13 exhibited increased Cauchy pressure and Poisson and Pugh's ratios. The ductility of face-centered cubic HEAs was found to be significantly influenced by the GBs, affecting mechanical properties. The Kleinman parameter highlighted a bending-type bonding with reduced strength at the GBs. Machinability indices indicated high machinability of the CoCrCuFeNi alloy, further enhanced by the presence of the GBs. Direction-dependent parameters underscored the anisotropic nature of the HEA, mitigated by the GBs. Overall, this study elucidates the nuanced influence of different GBs on the mechanical properties of HEAs, offering valuable insights for materials design and applications. The results of this investigation shed light on HEAs with improved mechanical properties via GB engineering. [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]

OBJECTIVE: The purpose of this study was to determine the in vitro effects of a single exposure of bupivacaine on the mechanical properties of bovine cartilage explants at 3 weeks. DESIGN: Femoral condyle articular cartilage explants were aseptically harvested from juvenile bovine stifle joints before being exposed to chondrogenic medium containing 0.50% (wt/vol) bupivacaine, 0.25% (wt/vol) bupivacaine, or no medication (control) for 1 hour. Explants were then washed and maintained in culture in vitro for 3 weeks before testing. Cell viability, tensile and compressive mechanical properties, histological properties, and biochemical properties were then assessed. RESULTS: Explants exhibited a dose-dependent decrease in mean tensile Youngs modulus with increasing bupivacaine concentration (9.86 MPa in the controls, 6.48 MPa in the 0.25% bupivacaine group [P = 0.048], and 4.72 MPa in the 0.50% bupivacaine group [P = 0.005]). Consistent with these results, collagen content and collagen crosslinking decreased with bupivacaine exposure as measured by mass spectrometry. Compressive properties of the explants were unaffected by bupivacaine exposure. Explants also exhibited a trend toward dose-dependent decreases in viability (51.2% for the controls, 47.3% for the 0.25% bupivacaine-exposed group, and 37.0% for the 0.50% bupivacaine-exposed group [P = 0.072]). CONCLUSIONS: Three weeks after 1-hour bupivacaine exposure, the tensile properties of bovine cartilage explants were significantly decreased, while the compressive properties remained unaffected. These decreases in tensile properties corresponded with reductions in collagen content and crosslinking of collagen fibers. Physicians should be judicious regarding the intra-articular administration of bupivacaine in native joints.

BackgroundThe calcaneal enthesis, an osseous footprint where the Achilles tendon seamlessly integrates with the bone, represents a complex interface crucial for effective force transmission. Bone adapts to mechanical stress and remodels based on the applied internal and external forces. This study explores the relationship between the elasticity of the Achilles tendon enthesis and the bone microstructure in the calcaneal crescent.MethodsIn total, 19 calcaneal-enthesis sections, harvested from 10 fresh-frozen human cadaveric foot-ankle specimens (73.8 ± 6.0 years old, seven female), were used in this study. Indentation tests were performed at the enthesis region, and Hayes' elastic modulus was calculated for each specimen. Micro-CT scanning was performed at 50-micron voxel size to assess trabecular bone microstructure within six regions of interest (ROIs) and the cortical bone thickness along the calcaneal crescent.ResultsSignificant Spearman correlations were observed between the enthesis elastic modulus and trabecular bone thickness in the distal entheseal (ROI 3) and proximal plantar (ROI 4) regions (R = 0.786 and 0.518, respectively).ConclusionThis study highlights the potential impacts of Achilles tendon enthesis on calcaneal bone microstructure, which was pronounced in the distal calcaneal enthesis, suggesting regional differences in load transfer mechanism that require further investigation.

Mitigating ambient vibrations using periodic pile barriers has gained significant attention in the past decade. The width of the bandgap and the attenuation coefficient are two important factors that determine the vibration reduction capabilities of periodic pile barriers. In certain situations, significant vertical anti-plane vibrations may occur, such as those generated by subways. Therefore, the focus of this article is to optimize the attenuation coefficients of anti-plane shear waves in periodic pile barriers. Firstly, a single-objective topology optimization framework is developed based on the Genetic Algorithm (GA) to maximize the attenuation coefficient of anti-plane shear waves in periodic pile barriers at a target frequency. The optimization considers the effects of the target frequency, elastic modulus of soil, and wave vector direction. A comparison between the optimized and traditional pile barriers is performed to demonstrate the superiority of the optimized design. Secondly, a multi-objective optimization framework is developed based on the non-dominated sorting GA II (NSGA-II) to investigate the relationship between the attenuation coefficient and the filling fraction, as well as the relationship between the attenuation coefficient and the bandgap width. The results indicate that a higher filling fraction results in a larger attenuation coefficient, while there is a tradeoff between the filling ratio and the bandgap width. Thirdly, an optimization framework is established considering the effect of a moving load, and the coverage rate of the target frequency range is defined to design periodic pile barriers. Finally, numerical simulations are conducted to validate the effectiveness of periodic pile barriers in mitigating vibrations when a finite number of pile rows is used. [ABSTRACT FROM AUTHOR]

Triggered by the growing needs for photoelectric conversion and optical interconnections, flexible optoelectronics have recently attracted a surge of interest. Flexible hybrid laminates are promising components of these devices owing to their high performance and flexibility. However, the thermomechanical mismatch of heterostructures usually induces interfacial stresses and resultant failures, particularly for multilayer structures with soft polymeric substrates. The interfacial stresses in flexible laminates remain a challenging matter to be understood distinctly. Herein, the interfacial stresses are investigated via a representative case composed of hard and soft hybrid laminate under nonuniform temperature. By introducing nonuniform shear strain in the thickness direction of bond layer, and nonuniform temperature changes of multilayer simultaneously, a novel analytical model is developed to describe the interfacial stresses with considering adjusted interfacial compliances for the bond layer with varying thicknesses. Our analytical expressions are suitable for different interfacial compliances and a trilinear approximation is verified by the finite element method (FEM) for the adhesive layers with different thicknesses, and comparative analyses were carried out with the existing literatures. The characteristics of the shear stresses are quantitatively illustrated under different temperature variations, elastic moduli and geometrical dimensions. Based on above the vital influencing factors, the mitigating strategies for shear stress are proposed to decrease the interfacial damage. By optimizing key parametric designs, the model and analysis of interfacial stresses could be useful for characterizing the interfacial thermal stress of rigid-flexible films, and enhancing the mechanical stability of heterogeneous multilayers. [ABSTRACT FROM AUTHOR]

One approach to structural health monitoring (SHM) involves embedding sensors within a composite material. However, the integration of these sensors can potentially introduce flaws that might affect the composite's mechanical properties. This research aims to explore the impact of embedding exfoliated graphite (EG)/epoxy sensors on the mechanical characteristics of composite systems through laboratory experiments and numerical simulations. Sensor strips composed of varying volume fractions of EG/epoxy were fabricated. Tensile test specimens were prepared by embedding these sensors in the epoxy matrix oriented both lengthwise and widthwise. Baseline specimens of EG/epoxy without sensors were also created for comparison. Tensile tests were performed on the samples to evaluate the effects of the embedded sensors on the composite's elastic modulus and tensile strength. The results indicated a slight improvement in both elastic modulus and tensile strength with the introduction of EG. Crucially, the orientation of the sensors within the samples had a significant impact on the composite's mechanical properties. Samples with widthwise-aligned sensors showed reduced tensile strength due to delamination along the sensor edges. Finite element simulations using a viscoelastic model based on the experimental data were conducted to analyze the effect of sensor alignment on mechanical properties. The findings revealed that a grid pattern alignment of sensors significantly enhanced mechanical performance compared to lengthwise or widthwise alignment, particularly at 0.1% and 0.3% EG volume fractions, highlighting the effectiveness of a grid pattern for embedding sensors in SHM applications. [ABSTRACT FROM AUTHOR]

Basalt fiber-reinforced composite (BFRC) is extensively used in various fields such as rail transportation and aerospace. However, how to design the structure of BFRC to optimize its impact resistance remains a great challenge. Herein, inspired by the double-twisted Bouligand structure of coelacanth scales, a biomimetic BFRC is prepared. Significantly, the peak impact force of double-twisted BFRC (DT-BFRC) is 3408.12 N, which increases by 48.56% compared with unidirectionally laminated BFRC (UL-BFRC). The maximum residual elastic modulus of DT-BFRC reaches 7.88 J, which is 236.75% higher than that of UL-BFRC. This work offers a promising way to efficiently develop impact resistant BFRC. [ABSTRACT FROM AUTHOR]

A coupled Mori-Tanaka/finite element strategy was implemented to capture deformation profiles of aluminum AA 6063 cylindrical and hexagonal tubes reinforced with 60% variable coir-fiber thickness (5 mm, 10 mm) coir-fiber under variable oblique crushing. By a representative volume element (RVE) defined elastic moduli of the reinforcement phase hybrid tubes were simulated for the effect of reinforcement layer thickness under the Johnson-Cook's and Hashin's intralaminar damage with cohesive zone modeling. As, transformations in deformation underscored variabilities in shape, multicellularity and reinforcement thickness, a correlation is found between loading angles and peak crushing forces in evolving a lightweight absorber consistent with extreme oblique impacts. [ABSTRACT FROM AUTHOR]

One current trend in orthopedics is the production of bone-mimetic porous structures using selective laser melting (SLM). However, there is still a lack of knowledge on fine-tuning the process to ensure the quality of such complex products. Therefore, this study sought to gain insight into how the laser parameters affect the pore shape and mechanical properties. Specifically, based on Voronoi tessellation, the bone-mimetic porous structure was designed to have an average pore size of 600 µm and fabricated by an SLM machine using Ti-6Al-4 V powder. The laser power and scan speed varied at 80–160 W and 550–950 mm/s, respectively. Afterward, the pore shape error was manually measured using micro-CT images, and the mechanical properties were obtained through compression tests. As a result, the pore narrowed in response to stronger laser powers and slower scan speeds, more dominantly altered by the former. In addition, greater dimensional inaccuracies led to higher mechanical properties, showing a positive correlation. Consequently, the combination of the weakest laser power (80 W) and the fastest scan speed (950 mm/s) exhibited the closest pore size distribution to the design with minimized shape errors of 135–150 µm while maintaining clinically acceptable levels of compressive strength and elastic modulus (131.45 MPa and 6.24 GPa, respectively). Our findings can serve as valuable references for successfully manufacturing the latest porous implants. [ABSTRACT FROM AUTHOR]

Bi-directional re-entrant anti-tetrachiral (BRATC) structure with negative Poisson's ratio is developed in this paper to meet the requirement in the variation of morphing wing area. Inherited from the anti-tetrachiral (ATC) structure, the BRATC has the potential of lightweight and out-of-plane stiffness properties, which is suitable for simultaneous deformation and load-bearing capability in the design of morphing wings. At the same time, inspired by the design idea used in re-entrant anti-tetrachiral (RATC), the BRATC structure has improved the potential of deformability by relaxing the rotation constraints of the ligaments. The effect of the geometric parameters on the equivalent mechanical properties of BRATC, such as elastic modulus and Poisson's ratio was investigated by using the finite element method. The relation between geometric parameters and the mechanical properties is then obtained. Finally, mechanical properties of the BRATC structure are tested with the aid of additive manufacturing technology in the tensile experiment. [ABSTRACT FROM AUTHOR]

The bonding performance and formation of the interphase region between fiber and matrix have significant effects on the strength and durability of composites. A new approach, involving combined experimental and numerical analyses, has been developed to avoid the shortcomings and scattering associated with local experimental methods. For this purpose, tensile tests are performed on specimens fabricated from a single glass fiber and epoxy resin. The elongations for specified lengths are measured using the digital image correlation (DIC) technic. The size of the fiber diameter and specimen section are also measured from SEM images. The obtained experimental displacements for micro tensile tests are used in an inverse elastic finite element solution to obtain the interphase elastic modulus. It is shown that, considering the interphase thickness of 1.0 μm that is more realistic, the interphase elastic modulus is in the range of 12 ∼ 19 GPa. However, the performed sensitivity analysis shown that considering interphase thickness ranging from zero to 2.0 μm the interphase elastic modulus varies between 9 and 46 GPa. It is shown that the proposed procedure can be used to obtain the overall mechanical properties of the matrix/fiber interphase in long fiber composites. [ABSTRACT FROM AUTHOR]

The bar properties (elastic modulus, density, Poisson's ratio, and sound speed) necessary for exploiting bar impact tests were calibrated via two methods called the 1D method (which combines the iterative dispersion correction with 1D approximation) and 3D method (which resorts to the simulation-based reverse engineering of the strain profile in a circular 3D bar). The two methods cross-verified one another for a maraging steel bar with 19.1 mm in diameter. This paper also considers the method of calibrating measured strain and finally presents a method of determining the impact velocity with reference to a reliably measured strain profile for a bar calibrated via the 1D method. [ABSTRACT FROM AUTHOR]

Nanocrystalline apatite (Ap), known for its exceptional biological properties, faces limitations in hard tissue engineering due to its poor mechanical properties. To overcome this limitation, we investigated the preparation of nanocomposites through heterogeneous nucleation of calcium phosphate on exfoliated graphene (G) and graphene oxide (GO) flakes, selected for their outstanding mechanical properties. The flakes were treated (functionalized) with amino acids of varying isoelectric points—namely L-Arginine (Arg), L-Alanine (Aln) and L-Aspartic acid (Asp)— as well as citrate (Cit) molecules. Furthermore, Tb3+ was incorporated into the formulations to introduce luminescence and further enrich the functionality of the composite. The synthesis was conducted using the sitting drop vapor diffusion method. Functionalized GO/Ap nanocomposites significantly improved roughness, adhesion forces and elastic modulus compared to Ap and G-based particles. GO-Asp-Ap-Tb nanocomposites exhibited the highest roughness (163.8 ± 116.2 nm), while G-Cit-Ap had the lowest (6.8 ± 5.6 nm). In terms of adhesion force, GO-Cit-Ap-Tb reached the highest value (31.06 ± 13.3 nN), while G-Arg-Ap had the lowest (3.7 ± 1.8 nN) compared to Ap (13.6 ± 3.2 nN). For the elastic modulus, GO-Aln-Ap-Tb demonstrated the greatest stiffness (3489 ± 101.01 MPa) compared to Ap (30.2 ± 6.5 MPa), while G-Aln-Ap-Tb showed the lowest (17.2 ± 8.4 MPa). Concerning their luminescence, regardless of G/Ap and GO/Ap, the relative luminescence intensities depended on the biomolecule used and decreased in the order Arg > Aln > Asp and Cit. Furthermore, G/Ap and GO/Ap nanocomposites demonstrated good biocompatibility on murine mesenchymal stem cells at low concentrations, showing cell viabilities exceeding 80 % at 0.1 μg/mL. This research offers a novel approach to enhancing the mechanical properties of apatites while preserving their good biocompatibility properties and introducing new functionalities (i.e. luminescence) in the composites, thereby expanding their range of applications in hard tissue engineering. [Display omitted] • Nanocomposites by heterogeneous nucleation of apatite on biomolecule-labeled G and GO. • L-Arginine, L-Alanine, L-Aspartic acid, citrate and Tb3+ influence Ap deposition. • GO-Ap nanocomposites improve roughness, adhesion, and elastic modulus over Ap. • Tailored mechanical, luminescent and biological properties of G-Ap and GO-Ap. [ABSTRACT FROM AUTHOR]

Yttrium-containing ceramics exhibit excellent resistance to water-oxygen corrosion, making them an attractive choice as the modified matrix for SiC f /SiC composites. However, the oxidation products of yttrium-containing ceramics are complex and vary widely in performance. In this study, YSOC ceramics, which are composed of yttrium silicate, SiO 2 , and SiC, were prepared using Y 2 O 3 , SiO 2 , SiC, and Li 2 CO 3. This research investigated the effects of high temperatures, air oxidation, and water-oxygen corrosion on the phase compositions of YSOC ceramics. The influence of environmental factors on the synthesis and decomposition of yttrium silicate was analyzed. Moreover, the study explored the compatibility of different oxidation products with SiC. The results suggest that Y 2 SiO 5 and Y 2 Si 2 O 7 are formed through the low eutectic of SiO 2 , Y 2 O 3 , and Li 2 CO 3. The high SiO 2 content likely contributes to the relatively low formation temperature of Y 2 Si 2 O 7. In the oxidizing environment, Y 2 SiO 5 reacts with SiO 2 to produce Y 2 Si 2 O 7. Conversely, in the water vapor-containing atmosphere, Y 2 Si 2 O 7 undergoes hydrolysis to form Y 2 SiO 5. Y 2 Si 2 O 7 displays a reduced elastic modulus in comparison to SiC fibers and exhibits favorable physical and chemical compatibility with SiC fibers. However, the hydrolysis of Y 2 Si 2 O 7 may potentially affect the water-oxygen corrosion resistance of the ceramics. These findings will significantly advance research and enhance understanding of the water-oxygen corrosion behaviors of yttrium-containing matrix-modified composites. [ABSTRACT FROM AUTHOR]

The study uncovers the microstructure and mechanical properties of brazed joints between SrTiO 3 ceramics and a phosphate glass with the composition 49SnO-19ZnO-32P 2 O 5 -3SiO 2. The primary objective is to investigate the wettability of the phosphate glass on SrTiO 3 ceramics and the evolution of joint strength over varying holding times. Key findings reveal that the phosphate glass exhibits favorable wettability on SrTiO 3 ceramics. The formation of Zn 2 P 2 O 7 and SnP 2 O 7 phases in the joint microstructure and the amount of these two phases gradually increases with the holding time. The mechanical performance is highlighted by the achievement of a peak shear strength of 40.3 MPa after brazing at 560 °C for 10 min. Additionally, the hardness, elastic modulus, and plasticity of the Zn 2 P 2 O 7 and SnP 2 O 7 phases were found to be intermediate between those of the SrTiO 3 matrix and the glass. The formation of these two phases significantly enhances the mechanical properties of the joint. [ABSTRACT FROM AUTHOR]

CaBi 4 Ti 4 O 15 (CBT) ceramics are promising piezoelectric materials that have been widely studied for high-temperature applications. Despite significant advancements in the electrical performance of CBT ceramics, the understanding of their mechanical behaviors remains limited, which is unfavorable for designing ceramics with high stability and reliability during high-temperature service. This work investigated the mechanical properties and fracture behaviors of Nb/Mn co-doped CaBi 4 Ti 4 O 15 (CBTNM) with various doping levels, focusing on stress-strain responses and ferroelastic deformation behaviors under uniaxial compression and multi-field coupling conditions. HRTEM analysis reveals small-scale layered domain wall structures on the surface of plate-like grains. The fracture and compressive strengths of CBTNM ceramics initially decrease and then increase with an increase in doping content, and the underlying mechanisms are related to grain size, defects, and densification. CBTNM ceramics exhibit nonlinear stress-strain responses due to ferroelastic deformation under compressive loading, and the resultant irreversible domain switching strain increases with an increase in doping content, while poling can further increase the residual strain. Under multi-field loading conditions, CBTNM ceramics undergo more ferroelastic deformation events and exhibit larger residual strain. The micro-cracks, pores, complicated fracture modes, and degraded fracture surfaces with fragmental and rough features are mainly responsible for the lower elastic modulus and inferior mechanical response. This work enhances our understanding of the mechanical behaviors of high-temperature piezoelectric ceramics and provides guidance for designing high-performance piezoelectric materials for complex environmental applications. [ABSTRACT FROM AUTHOR]

C/C composite was successfully brazed with TiZrHfTa/Ni or ZrHfNbTa/Ni composite interlayers using spark plasma sintering. The influence of different interlayers and joining parameters on the joint morphology, shear strength at room temperature and 1000 °C was investigated. For both composite interlayers, the C/C joints obtained at 1800 °C for 30 min consisted of a single high entropy cermet structure, with a near equimolar high entropy carbide hard phase and a near pure Ni binder phase. However, the use of different composite interlayers resulted in differences in the elastic modulus and hardness of the formed high entropy carbide phase. The maximum shear strengths of the obtained C/C composite joints using TiZrHfTa/Ni and ZrHfNbTa/Ni interlayers at room temperature were close, with value of 37.49 ± 1.44 MPa and 38.95 ± 1.26 MPa, respectively. Because (Zr-Hf-Nb-Ta)C had better high-temperature stability than (Ti-Zr-Hf-Ta)C, the obtained C/C-ZrHfNbTa/Ni-C/C joint exhibited a higher shear strength of 28.54 ± 1.71 MPa at 1000 °C. After shear testing at both room temperature and 1000 °C, fractures in all joints predominantly occurred within the C/C composite near the reaction layer, indicating a substrate failure mode. The use of composite interlayers resulted in C/C composite joints with excellent shear strength, primarily due to the in-situ synthesized high entropy cermet reaction layer, which provided superior strength and toughness. Additionally, the laser-textured pattern on the C/C composite surface formed numerous interlocking structures at the joint interface, further enhancing the joints' shear strength. [ABSTRACT FROM AUTHOR]

The interactions between hydrogen and crystallographic defects are the key to understanding hydrogen induced localized plasticity or damage mechanisms. However, unraveling such interactions based on the resulting mechanical effects alone can be challenging, due to the spectrum of various effects hydrogen can create in a given microstructure. Pre-deformation or post-mortem characterization of hydrogen segregation has similar limitations, as they can only provide snapshots of these complex processes with challenging spatial and temporal scales. To tackle this, we design in situ experiments that combine electron channeling contrast imaging (ECCI), electron backscattered diffraction (EBSD), and desorption spectroscopy, to investigate hydrogen defect interactions, under no external loading. We show that the inhomogeneous hydrogen distribution within microstructures can cause long-range (>200 nm) dislocation rearrangements. Interpretation of these results as manifestations of boundary-segregation induced stress suggests that microstructural characteristics on either side of the boundary should also play an important role. We provide quantitative assessments of these microstructure neighborhood effects and discuss additional contributions from hydrogen-induced changes in stacking fault energy and elastic modulus. • Hydrogen presence can alter defect substructures and local crystal orientation. • Defect activity likely arise from local lattice accommodation of H-induced stresses. • HE-resistant design lies in uniform H-distribution and accommodating textures. [ABSTRACT FROM AUTHOR]

In order to reveal the response mechanism of longitudinal wave velocity and related parameters, through the statistical analysis of the measurement data of seafloor sediments, it is found that there is a minimum value of the change of longitudinal wave velocity with porosity of seafloor sediments. The minimum values of the empirical formula for the change of longitudinal wave velocity with porosity of sediments in different sea areas and their critical porosity values are uniformly analyzed. The calculation shows that the minimum variation range of longitudinal wave velocity with porosity of sediments in different sea areas is between 1468.59 and 1520.22 m/s, and the corresponding critical porosity value changes between 0.69 and 0.88. The analysis shows that the empirical formulas of different scholars belong to the unified mathematical expression derived from acoustic theory. The study shows that the essential reason for the formation of the minimum of longitudinal wave velocity in seafloor sediment is that the coupling of sediment grains affects the propagation of longitudinal wave. It is further revealed that the physical mechanism of the change of longitudinal wave velocity is that the change of contact or suspension state of seafloor sediment grains in seawater affects the elastic stress-strain relations of sediments. [ABSTRACT FROM AUTHOR]

As a pivotal elastic property, elastic modulus plays a crucial role in characterising the mechanical performance of materials. To achieve the convenient and remote measurement of the elastic modulus of materials at elevated temperatures, a method based on diffracted grating laser-induced narrowband surface acoustic waves (SAW) is proposed. The design scheme of the diffraction grating is disclosed, and a CCD camera is deployed to confirm the generated grating pattern and determine the actual grating period. Delving into the viability of an effortless and reliable procedure for calculating elastic modulus is discussed. The elastic modulus determined by the SAW does not depend on the exact Poisson's ratio, which can be calculated from the SAW velocity with a given, less precise value for Poisson's ratio. Experimental results of the three metals are in line with the reference values, and the elastic modulus at elevated temperature is successfully measured remotely, thereby verifying the feasibility of the proposed method. [ABSTRACT FROM AUTHOR]

Bio-polymer composites are emerging as a feasible substitute for conventional polymers in various major fields of applications. In the current research, the impact of hybridization of inter and intra-woven natural engineering fibers namely, brown flax, white flax, and jute of different amalgamations along with commingled SCF and novel nano IW filler has been studied. The composites are manufactured by hand layup process and physical and thermomechanical characteristics of the composites are experimentally studied. The composites mingled with IW filler demonstrated better dimensional stability and mechanical properties such as maximum tensile strength of 36.74 MPa, bending strength of 82.53 MPa, and hardness of 84.89 D compared to other composites. However, elastic and flexural modulus are maximum for composite without any filler. The composites mingled with SCF filler demonstrated the highest impact strength, energy absorption, and elongation. Thermogravimetric analysis and thermal conductivity study demonstrated that the composite with SCF filler exhibited better thermal stability and thermal resistance than the other hybrid composites. Fourier transform infrared spectroscopy study confirms the interaction of hydrogen bonds with different polymers, matrices, and fillers. It is established that the weaving pattern and the filler types greatly influences the mechanical and thermal characteristics of the composites. Filler addition and fabric hybridization optimizes the catastrophic failures and enhances the thermal stability, hence becoming more suitable for small interior structural components in aerospace and automobile applications. [ABSTRACT FROM AUTHOR]

Summary: We report on the role of ethylenediaminetetraacetic acid (EDTA) in addition to the structural and material properties of acid milk gels formed via addition of glucono‐delta‐lactone (GDL) and these properties of corresponding analogue cream cheeses prepared from these gels. Increasing addition of EDTA to cheese milks prior to acidulation reduced the concentration of insoluble calcium in the milks. Acid gelation of milks, as measured by small deformation rheology, showed a decreased rate of gelation and lower relative elastic modulus of gels with increasing EDTA concentration. The sequestration of colloidal calcium phosphate from the casein micelle by the addition of EDTA led to the lower gelation rate and elastic modulus. The lower extent of ionic binding is considered the causative mechanism for formation of weaker gel structures. Cream cheeses prepared using acid gels with GDL acidulant were compositionally unaffected by EDTA concentration. However, variations in G′ observed in the acid gels containing increasing levels of EDTA correlated with large deformation material property changes in cream cheese analogues. In addition, the increasing inclusion of EDTA in cheese milks translated to reduced water‐holding capacity of the cream cheeses prepared from those milks. These results provide insights on the specific role of milk calcium on the structure, material and physical properties of acid milk gels and corresponding cream cheese analogues. [ABSTRACT FROM AUTHOR]

This study presents comprehensive numerical modeling methods for simulating early‐age stress (EAS) relaxation in cementitious materials, based on the autogenous deformation (AD), elastic modulus, creep, and stress continuously tested by a mini temperature stress testing machine (Mini‐TSTM) and a mini AD testing machine from a very early age (i.e., from a few hours to a week). Four methods for converting creep compliance to relaxation modulus were discussed in detail and used for the one‐dimensional (1D) and three‐dimensional (3D) simulation of stress evolution in the Mini‐TSTM test. Furthermore, virtual creep and relaxation tests were conducted using an exponential algorithm with either the Kelvin or Maxwell chains to show their applicability in simulating the viscoelastic behavior of early‐age cementitious materials. The results showed that the exponential algorithm with the Maxwell chain using an exponential conversion function from creep to relaxation obtains good prediction accuracy of EAS in 3D analysis. The numerical solutions of the Volterra integral of creep compliance can lead to a negative relaxation modulus, thus introducing stress calculation errors in both 1D and 3D analysis. [ABSTRACT FROM AUTHOR]

Weld lines are common surface defects in micro-injection molding (µIM) and degrade the appearance quality and material properties of polymer parts. The restraining effects of the two-dimensional ultrasonic vibration (2DUV) on weld lines are investigated, and the feasibility of the 2DUV in reducing the weld line dimensions and improving the material properties is verified. The results show that the 2DUV outperforms the one-dimensional ultrasonic vibration (1DUV) in restraining weld lines. By raising the polymer melt temperature, reducing the flow pressure loss, and improving the melt fluidity, the 2DUV facilitates the formation of smaller weld lines, achieving the largest reductions of 3% (76.8 µm), 31% (25.8 µm), and 23% (2.0 µm) in the length, width, and depth, respectively, compared with no ultrasonic vibration (NUV). Simultaneously, the 2DUV weakens the polymer molecule orientation and promotes the crystallization, leading to a more significant enhancement in the material properties of the weld line area than the 1DUV, in which the elastic modulus and hardness of the start area of the weld line are 1.06 GPa and 0.072 GPa, respectively, showing the largest increases of 8.5% and 12.5%, compared with the NUV. Furthermore, the 2DUV reduces the material anisotropy of the weld line area and is superior to the 1DUV in improving the uniformities of the material properties. Compared with the NUV, the largest improvements of the uniformity of the elastic modulus and hardness in the weld line area under the 2DUV are 76% and 93%, respectively, and those in the whole bottom are 94% and 80%, respectively. [ABSTRACT FROM AUTHOR]

The tunneling underlying inevitably leads to the displacement of adjacent soil, greatly influencing the deformation of the tunnel above. Most theoretical studies primarily concentrate on analyzing the mechanical equilibrium of individual tunnel sections, ignoring the energy generated by the system during tunnel deformation. Based on this, in view of the energy relationship, the overlying tunnel's deformation is simulated by using the Rayleigh–Ritz method. Further, its potential energy equation can be established based on the Vlasov foundation. The corresponding energy variational solution is solved according to the minimum potential energy principle, leading to an analytical solution for the shield tunneling‐induced overlying tunnel's response. The efficacy of the suggested method is verified by contrasting it with centrifuge experiments and field case studies derived from prior studies. Relative to the Winkler foundation model, which deviated from the suggested approach, the results derived from the suggested method show a closer correlation with the collected measurement data. Further parameter studies show that the vertical clearance and skew angle between two tunnels, the volume loss rate, and elastic modulus are significant factors affecting the tunnel behaviors due to tunneling underneath. The suggested theoretical model can be applied to forecast potential risks that an existing tunnel may encounter during the excavation of a new tunnel underlying in similar engineering projects. [ABSTRACT FROM AUTHOR]

The aim of this work is to investigate the deformation and energy characteristics of skarn with different interlayer inclination angles under cyclic loading. The skarn samples with marble bands of various orientations (i.e., 30°, 45°, 60°, and 75°) were chosen as the test material. It is revealed from the testing results that the presence of interlayers changes the geomechanical properties of the rock, rock peak strength, and elastic modulus increases with increasing the interlayer inclination angle. Additionally, the growth rate of input energy exhibits an inverted "V" pattern with respect to the interlayer inclination angle. In terms of damage modes, intact marble and skarn predominantly exhibit tensile damage, whereas interlayered rocks exhibit a combination of tensile and shear failure pattern. Finally, a damage evolution model defined by axial strain is proposed and expressed to fit the experimental data. The results in this work would provide a crucial theoretical basis for the safety assessment of underground engineering constructions. [ABSTRACT FROM AUTHOR]

Polystyrene foam (EPS) concrete is a composite concrete material commonly used in construction, which has excellent thermal insulation and thermal insulation properties, but also has defects of weak bonding interface.KH-560 can significantly improve the characteristics of EPS particles and concrete matrix, which have different physical and chemical properties and are difficult to combine. In this study, the effects of different levels of KH-560 on the enhanced mechanical properties of EPS concrete were studied from the aspects of macroscopic mechanical properties, microstructure characteristics, chemical composition and discrete element simulation, and the mechanism of action was discussed. The results of mechanical experiments show that the compressive strength and flexural strength of EPS concrete mixed with KH-560 are higher than those of ordinary EPS concrete, and its mechanical properties gradually increase with the increase of KH-560 content. XRD, FT-IR and SEM observations showed that more C-S-H gels would be produced under the action of KH-560, which made the structure of the weak interface transition zone of EPS concrete more compact. The results of discrete element simulation show that the peak strength of EPS concrete increases with the increase of friction coefficient, but has little effect on its elastic modulus. [ABSTRACT FROM AUTHOR]

To evaluate the peel resistance of a device wherein a polyimide (PI) sheet is bonded to a curved surface with a pressure-sensitive adhesive (PSA) experimentally and analytically, we applied a mechanical simulation considering the viscoelasticity of the pressure-sensitive adhesive (PSA) and the fracture energy of the bonding interface. The mechanical behavior against the local load applied on the PI sheet surface was evaluated using this simulation. To verify the accuracy of this simulation, we fabricated a local load tester that could apply a load to a local area of 8 mm in diameter and compared the mechanical behavior with the simulation results. Dynamic mechanical analysis of the PSA with a film thickness of 19 μm was performed using the nanoindentation technique. The generalized Maxwell model parameters were estimated by fitting the relaxation elastic modulus E(t) to conduct a mechanical simulation. For the double cantilever beam test to derive the interfacial fracture energy, soft PI sheets were reinforced with Al substrates. As a result of these analyses, it was confirmed that the relationship between the displacement and load obtained by this simulation agrees well with the actual local load test. This technique is useful for predicting the bonding strength of complex-shaped devices fabricated using soft adherends and adhesives. [ABSTRACT FROM AUTHOR]

Effect of Nb element on the microstructure and mechanical properties of Co–8.8Al–9.8W superalloy was analysed by studying the occupancy of Nb element in the lattice and difference in the microstructure evolution during deformation. The calculation results show that Nb atom occupies the first priority position of Al2 and the second priority position of W6, forming a γ′ phase doped structure, and its strength, hardness and structural stability are improved. In the process of high-temperature deformation, the dislocations of 0Nb alloy have the mechanisms of cutting and bypassing, which makes strengthening phase rafting phenomenon, and dislocation propagation in 2Nb alloy is difficult, and there are a lot of stacking faults. Compared to 0Nb alloy, 2Nb alloy has improved nano-indentation hardness and elasticity modulus. [ABSTRACT FROM AUTHOR]

Concrete can be cast and cured at freezing temperatures when additive-based freeze protection (ABFP) is included in the concrete mixture. However, the effects of extremely cold temperatures on the mechanical properties of concrete with ABFP have not been studied. In addition, the impact of cold temperatures on shear strength and modulus of rupture of concrete with or without ABFP have not been measured. The present study measures the effects of decreasing temperatures on the compressive strength, modulus of elasticity, shear strength, and modulus of rupture of concrete with and without ABFP. Different types of aggregates and ABFP systems were used to manufacture conventional concrete (without ABFP) and concrete with ABFP. Concrete with ABFP is mixed, cast, and cured at −5°C and conventional concrete, at 20°C. Specimens are conditioned at 20°C, −5°C, −20°C, −40°C, or −60°C for 24 h and then tested. Generally, it was found that the mechanical properties of both types of concretes increased as the test temperature decreased. However, ABFP lowers the pore solution's freezing point and lowers the relative compressive strength increase rate compared with conventional concrete. Concrete with ABFP can have a higher rate of increase in relative elastic modulus than conventional concrete. This is due to the two-phase system of an ABFP pore solution at low temperatures, where ice fills voids, and the unfrozen concentrated pore solution continues to fill capillary voids and wet calcium silicate hydrate. The increase in shear strength from the aggregates and hydration products is greater than the contributions of the pore solution's frozen properties. Finally, the rise in rupture strength is attributed to the increase in the strength of concrete materials because there is no significant change in the tensile strength of ice with decreasing temperature. [ABSTRACT FROM AUTHOR]

The thermal-induced pore-water pressure and shear characteristics of lateritic clay under different temperature paths without drainage are studied through a series of temperature-controlled undrained triaxial shear tests with temperatures ranging from 5°C to 50°C. The effects of different temperature paths under undrained conditions on pore-water pressure and shear behavior are discussed. The results indicate that monotonic heating and multistage heating have equivalent effects on the accumulation of pore-water pressure when the initial temperature and target temperature are the same. The initial positive pore-water pressure induced by heating leads to a lower bearing capacity during the early stage of the shearing process. The secant elastic modulus (εa = 0.1%) shows a significant decrease with increasing temperature, suggesting that mechanical properties at small strains are influenced by temperature. However, undrained heating has no influence on the shear strength finally. Furthermore, under undrained conditions, temperature variations do not alter the unique relationships among void ratio, deviator stress, and mean effective stress. [ABSTRACT FROM AUTHOR]

Horizontal well fracturing in the roof of coal seams has been demonstrated to be an effective technique for extracting coalbed methane. However, the mechanism of hydraulic fracturing fracture expansion from roof to coal seam and penetrating the interlayer in multiple stage fracturing is not comprehensive. Mechanical properties of the reservoir, fracturing parameters, and fracturing mode are the mainly factors that influence extraction efficiencies. To explain the relationship between fracturing behaviors and coal, the interlayer and roof along with the fracture propagation and penetration in multiple stages of fracturing; the interaction mechanism of fracture propagation; and penetration with elastic modulus, injection velocity, and fluid viscosity are simulated in single and staged fracturing. Additionally, the effect of the fracturing mode on fracture propagation is considered. The results show that the coal seam strength dominantly influences longitudinal fracture propagation while marginally affecting circumferential stress. Significant modulus differences between coal-rock interlayers and coal seams hinder fracture propagation. In the case of a low injection rate and fluid viscosity, increasing the injection rate and fluid viscosity can help enlarge the fracture area and facilitate penetration. Multistage fracturing and its high injection rates are conducive to maximizing the efficiency of fracturing operations. These results contribute to understanding and optimizing hydraulic fracturing in coal seams for efficient coalbed methane extraction. [ABSTRACT FROM AUTHOR]

This paper presents the experimental results of Grade 8.8S high-strength steel coupons tensioned to fracture at room and elevated temperatures, followed by finite element analyses for investigating the ductile fracture behavior. Smooth round bars, notched round bars, flat shear sheets, and flat grooved sheets were tested at room temperature, which covered a wide range of stress states. The relationship between the ductility of the Grade 8.8S high-strength steel and the stress state was discussed. Extra smooth and notched round bars were also redesigned and tested at elevated temperatures. The nonlinear variations of material properties, including elastic modulus, yield strength, and tensile strength, were discussed. Different modeling strategies were used for the room and elevated temperatures. At room temperature, three uncoupled ductile fracture criteria were evaluated regarding their applications in the Grade 8.8S high-strength steel. Besides, in conjunction with a modified Johnson–Cook (JC) hardening model, the JC fracture criterion was improved and characterized by an exponential temperature function, as the original linear temperature function could not accurately describe the relationship between the fracture strain and temperatures. The developed finite element models closely traced most specimens' load-displacement paths at the room and elevated temperatures. [ABSTRACT FROM AUTHOR]

This study selected ZrB2–hBN ceramics as the matrix for low‐cost second‐generation SiC fibers, due to their low modulus and ability to be sintered at relatively low temperatures. The resulting composites, which contained up to 30 wt.% short‐chopped SiCf, were consolidated using reactive spark plasma sintering at 1550 and 1700°C under 50 MPa for 5 min. Without needing to prepare interfaces on the SiCf surfaces, fiber pullout, strengthening, and toughening during the fracture process were realized. By constructing the volatility phase diagram for the fiber, the microstructural changes that occurred on the fiber surfaces during sintering were successfully illustrated. Mechanical properties of ZrB2–hBN ceramics with 10 wt.% SiCf sintered at 1550°C still showed considerable improvements, including an elastic modulus of 187 GPa, a flexural strength of 337 ± 16 MPa, and a fracture toughness of 4.12 ± 0.25 MPa m1/2, increases of 12.6%, 61.2%, and 118%, respectively, compared to the counterparts without adding chopped fibers. Variations in these properties were linked to the matrix porosity and SiCf pullout behaviors, which were subsequently analyzed using the He–Hutchinson model. [ABSTRACT FROM AUTHOR]

Medium-entropy Zr–Nb–Ti (ZNT) alloys are being extensively investigated as load-bearing implant materials because of their exceptional biocompatibility and corrosion resistance, and low magnetic susceptibility. Nevertheless, enhancing their yield strength while simultaneously decreasing their elastic modulus presents a formidable obstacle, significantly constraining their broader utilization as metallic biomaterials. In this study, three medium-entropy ZNT alloys, i.e., Zr 45 Nb 45 Ti 10 , Zr 42.5 Nb 42.5 Ti 15 , and Zr 40 Nb 40 Ti 20 (denoted ZNT 10 , ZNT 15 , and ZNT 20 , respectively), were designed based on the miscibility gap in the ZNT phase diagram and prepared by annealing of cold-rolled ingots. Their microstructures, mechanical properties, wear resistance, corrosion resistance, magnetic susceptibility, and biocompatibility were systematically studied. Spinodal decomposition occurred in the cold-rolled ZNT 10 and ZNTi 15 after annealing at 650 °C for 2 h and resulted in nanoscale Zr-rich β 1 and (Nb, Ti)-rich β 2 phases, which significantly improved their yield strength and reduced their elastic modulus. The wear resistance of the alloys decreased with an increase in Ti content. Dense ZrO 2 , Nb 2 O 5 , and TiO 2 oxide layers were formed during the polarization process in Hanks' solution, which enhanced the corrosion resistance of the alloys. These ZNT alloys exhibited significantly lower magnetic susceptibility than medical Ti alloys. The ZNT alloys showed a cell viability of more than 94 % toward MG-63 cells after culturing for 3 d Overall, the spinodal ZNT 15 showed the best combination of mechanical properties, wear resistance, corrosion resistance, low magnetic susceptibility, and sufficient biocompatibility among the three alloys. This work reports on medium-entropy Zr–Nb–Ti (ZNT) alloys with heterostructure. Spinodal decomposition significantly improved their mechanical strength and reduced the elastic modulus of the alloys. The wear resistance of the ZNT alloys decreased with an increase in Ti content. Dense ZrO 2 , Nb 2 O 5 , and TiO 2 oxide layers were formed during the polarization process in Hanks' solution, which enhanced the corrosion resistance of the alloys. The ZNT alloys exhibited significantly lower magnetic susceptibility than medical Ti alloys. The ZNT alloys showed a cell viability of >94 % toward MG-63 cells after culturing for 3 d The results demonstrate that spinodal ZNT alloys have enormous potential as bone-implant materials due to their outstanding overall mechanical properties, high corrosion resistance, wear resistance, low magnetic susceptibility, and sufficient biocompatibility. [Display omitted] [ABSTRACT FROM AUTHOR]

In Si-killed steels, especially tire cord steel, the low-liquidus-temperature control technology for non-metallic inclusions had limitations in effectively addressing the issue of wire breakage. During the solidification of molten steel, oxide inclusions within the Al2O3-SiO2-CaO-based system could demonstrate crystallization or glass-forming behavior. The inherent disparities in properties between glassy and crystalline inclusions significantly influenced their deformation behavior during rolling process. Molecular dynamics and thermodynamic calculation provided the insight that the glass-forming ability could be precisely controlled by carefully manipulating the CaO/SiO2 ratio and Al2O3 content. Meanwhile, the advantage of glassy inclusions, which possessed a lower elastic modulus compared to crystalline inclusions, was verified through calculations. In addition, the Young modulus of glass differed from its glass-forming ability, which was not only determined by network connectivity but also influenced by density. The CaAl2(SiO4)2 phase stood as the most optimal choice for the composition controlling of Al2O3-SiO2-CaO inclusions crystallization. These profound insights could serve as a solid theoretical foundation for enhancing inclusion controlling strategies. [ABSTRACT FROM AUTHOR]