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A conceptual 20 MW high-temperature superconducting (HTS) motor (HTSM) with a novel glass-fiber reinforced plastic (GFRP) racetrack ring in the flexible support rotor was explored in this study. To support the cold mass at operating conditions, the high-strength, low-leakage GFRP racetrack ring was designed as follows. First, conceptual design of the 20 MW HTSM was conducted, and the torque transmitted by the GFRP racetrack rings was obtained through electromagnetic analysis. Second, a GFRP racetrack ring was designed, and its total cross-sectional area was obtained through theoretical analysis. Third, thermal leakage and stress were calculated and examined through theoretical and finite element analyses, respectively. The GFRP racetrack ring with the “D” ring was selected based on the results. The thickness and width of the GFRP ring were set to 16 and 10 mm, respectively, and the thickness of the “D” ring was 3 mm. Then, a full-scaled GFRP ring was fabricated, and its strength and stiffness were tested via room-temperature and low-temperature tensile tests. The average tensile strength and average Young’s modulus of the GFRP ring at room temperature were 1131.5 MPa and 49.9 GPa, respectively. The strength of the GFRP ring at 193.4 K was 1243.9 MPa, and the Young’s modulus of the GFRP ring at 141.3 K was 69 GPa. Lastly, a new 200 kW HTS generator was assembled using a scaled rotor with the same structure as the 20 MW HTSM and the original stator of an existing 200 kW generator. The test system was built to evaluate the feasibility of the GFRP ring before manufacturing the 20 MW HTSM. Test results showed that the GFRP ring is feasible, the design method of the GFRP ring is credible. The GFRP ring is suitable for the cold mass support of HTSMs and other low-temperature devices.

Zirconium based alloys, as refractory metallic materials, can be fabricated into brittle zirconium hydride by hydrogen charging and can then be used as neutron moderators in the nuclear industry. In this study, the fracture toughness of bulk e zirconium hydride was attempted to be estimated by means of Vickers microhardness indentation. Several representative semi-empirical formulas based on Palmqvist and half-penny crack models were adopted, and relevant parameters including Young’s modulus, Vickers hardness, indentation dimension, and crack length were respectively determined. It was observed that cracks began to nucleate at impression corners and peripheries when the load was higher than 500 gf. Crack length at 1000 gf was measured and used to estimate the fracture toughness. The results showed similar values to previous reports obtained from conventional experimental means, indicating that Vickers microhardness indentation is an available method for estimating the fracture toughness of e zirconium hydride.

A self-healing index, recovery modulus ratio (RG), was proposed to evaluate the self-healing characteristics of asphalt materials with intermittent loading tests which is more consistent with the t...

In this study, Ti-(0-30 wt.%)Nb alloys developed from elemental powders were fabricated by the Selective Laser Melting (SLM) process. Compositional homogeneity, microstructure and mechanical performance were investigated as a function of energy density. The proportion of un-melted Nb particles and isolated pore count reduced with increasing energy density, while Ti allotropic content (i.e. α’, α” and β) varied with energy density due to in-situ alloying. Increasing the Nb content led to the stabilisation of the α” and β phases. The mechanical properties were similar to those compositions manufactured using casting methods, without further post processing. The addition of 20Nb (wt.%) and using an energy density of 230 J/mm3 resulted in a Young’s Modulus of 65.2 ± 1.8 GPa, a yield strength of 769 ± 36 MPa and a microstructure of predominantly α” martensite. This strength to stiffness ratio (33% higher than Ti-10Nb and 22% higher than Ti-30Nb), is attributed to in-situ alloying that promotes solid solution strengthening and homogenisation. These alloys are strong contenders as materials suitable for implantable load-bearing orthopaedic applications.

The machining accuracy of a copper electrode gear (CEG), especially the pitch deviation of CEG, is affected by the wear of the ball end mill (BEM) with the increase of the length of milling path. Based on the error mapping principle, this work focuses on the influence of BEM wear on pitch deviation. In order to dynamically compensate the influence of the BEM wear on pitch deviation, a novel milling pitch deviation compensation model was proposed based on the formation mechanism and measurement principle of pitch deviation. To ensure the uniform wear at the milling edge of the BEM during the milling process, BEM wear was firstly copied to the pitch deviation according to the tooth-by-tooth milling strategy. Then, the BEM wear curve was fitted based on orthogonal experiments and multiple linear regression. According to the wear curve, an offline compensation method was adopted to compensate for the pitch deviation caused by BEM wear. In addition, the reverse compensation principle was used to compensate for the normal deviation of BEM milling path. Finally, the compensation model was verified by milling experiments. Pitch deviation met the requirements of Levels 4 $\sim $ 5 in GB/T 38192-2019. The model can be used to guide the milling process of CEG.

The size effects in spherical contact a investigated by employing a modified couple stress elasticity theory. An approximate couple stress field inside the half space is obtained by assuming that the couple stress elasticity-based displacement field is the same as the linearly elastic one. Besides, the linearly elastic stress field is expressed in a more explicit form. The stiffening effects of couple stress on contact load are expressed, and a contact load model is derived accordingly. Based on the derived load model, a modulus model which is able to describe the size effects observed in spherical contact tests is proposed. Furthermore, the validity of the modulus model is illustrated by comparing the model results with related experimental data. This work is helpful for readers to understand and calculate the size effects when measuring the modulus through spherical contact tests.

The cubic-phase antimony trioxide (α-Sb2O3) is a room-temperature stable molecular crystal, composed of cage-like tetraantimony hexoxide (Sb4O6) molecules. Despite its versatile functionality, the van der Waals (vdW) bond-dominated nanomechanics is still unclear. Here, the bending plate-like linear behaviors of high-quality α-Sb2O3 nanoflakes were observed using the nanoindentation method. It is found that the cage-molecular crystal owns a very low in-plane Young's modulus of 14.9 ± 0.8 GPa and a remarkable maximum tensile strain of 6.0-8.8%, corresponding to a rupture strength of 0.89-1.31 GPa. Elucidated by the atomistic simulations, the compliant elastic modulus and the unexpectedly strong rupture strain are associated with the high-symmetry vdW bonding structure. The vdW nanomechanics is of fundamental and technological relevance to nanoelectronics.

An asymptotic formula for the variance of squarefree numbers in arithmetic progressions of given modulus was obtained by Nunes (see reference [3]). We improve one of the error terms., Comment: Published with important revisions in Journal de Th\'eorie des Nombres Bordeaux

Halide double perovskite Cs2AgBiBr6 shows promising potential applications in next-generation photovoltaic devices. The strain engineering strategy has been proven as a reliable method to improve its performance. The fundamental physical tensor of elastic constants Cij has not been accurately measured yet, due to the limited size of samples. The aim of this work is to measure its full elastic tensor Cij using various techniques. We utilized nanoindentation and contact resonance atomic force microscopy (CR-AFM) techniques to measure the elastic modulus on an as-grown facet, which is along the [111] direction. Then, the inelastic X-ray scattering (IXS) approach and density functional theory were introduced to obtain the accurate full elastic constant Cij of single crystal Cs2AgBiBr6. The full elastic constants were measured as C11 = 44.52 GPa, C12 = 17.63 GPa and C44 = 8.56 GPa. The results for the modulus along the [111] direction reveal that nanoindentation and CR-AFM are sufficiently reliable for quantitative measurements of small single crystals Cs2AgBiBr6. The results provide guidelines for strain engineering in the photovoltaic applications using Cs2AgBiBr6 and for elastic property measurements in nanomaterials.

Stress waves propagate along vertical, radial and circumferential directions when a non-uniformly distributed load is applied at one end of a three-dimensional shaft. As a result, the receiving signals are usually mixed with undesired interference components, often featuring as high-frequency fluctuations. Previous studies have revealed that sectional geometry (shape and size) greatly affects the high-frequency interference. In this study, low strain dynamic testing on full-scale X-section concrete is conducted in order to investigate the influences of high-frequency interference on velocity responses at the pile head. Emphasis is placed on the frequency and peak value of interference waves at various receiving points. Additionally, the effects of the geometrical, and mechanical properties of the pile shaft on high-frequency interference are elaborated on through the three-dimensional finite element method. The results show that the measured wave is obscured by interference waves superposed by two types of high-frequency components. The modulus and cross-sectional area are contributing factors to the frequency and peak value of the interference waves. On the other hand, the position with the least interference is determined, to some extent, by the accurate shape of the X-section.

This study explores the benefits of utilizing recently developed protocols for microstructure quantification and the multiresolution mechanical characterization of Ti-based bulk metallic glass matrix composites. Four alloys with different compositions and amorphous (glass) fractions were studied. Microstructure quantification of the amorphous and crystalline phase in these alloys was performed using rotationally invariant 2-point spatial statistics and principal component analysis on approximately 1300 micrographs. Mechanical properties of the constituent phases as well as the bulk mechanical properties of the composites were measured using recently established high-throughput multiresolution spherical indentation stress–strain protocols. The results showed that decreasing amorphous volume fraction results in a decrease in both bulk Young’s modulus and the bulk yield strength of the samples, without significant changes in the mechanical properties of the constituent phases.

Wave velocity as a nondestructive test is widely used in various fields such as mining, civil, rock mechanics and rock engineering, and dynamic elastic properties of rocks are also determined by wave velocity. Rock mass contains discontinuities with different orientation angles, numbers of sets and frequencies and the impacts of such discontinuity properties on the wave velocity have not yet been systematically investigated. In this study, 20 groups of jointed cylindrical specimens with a wide range of discontinuity orientation angles (0°, 30°, 45°, 60° and 90°), numbers of sets and frequencies were prepared, and their P-wave velocities were measured. P-wave velocity (VP) significantly increased with increasing orientation angle (θ) and decreasing the discontinuity frequency (F). Several relations were applied to analyze the results. Finally, a new empirical relation was developed to predict VP as a function of θ angle using two parameters of P-wave velocity perpendicular to the discontinuity plane (VP0°) and P-wave velocity along the discontinuity direction (VP90°) or anisotropy degree (e = (VP90° − VP0°)/VP0°) with a good correlation of determination (R2 = 0.933), low RMSE (RMSE = 200.0 m/s) and low CV (CV = 6.7%). A good correlation between VP and F was also achieved for the test results. The intact rock elements in the complex nature of a rock mass are surrounded by discontinuities like a three dimensional puzzle. Treatment of such a rock mass system using cement grouting is an attractive method to improve its quality for various purposes. All 20 groups of jointed cylindrical specimens were grouted by cement. Wave velocities of the grouted specimens were measured after 2 months. VP significantly increased after grouting for all models of jointed specimens, as wave velocity of jointed specimens improved and approached to the wave velocity of the intact rock for most cases. The discontinuity orientation of the specimens had no significant effect on the wave velocities after grouting. But the results showed that VP and VS increased little with increasing orientation angle for jointed specimens consisting only of one set of discontinuity. After grouting the jointed specimens, orientation angle and frequency of discontinuities had also similar effects on the dynamic Young's modulus (E), Poisson's ratio (ν), shear modulus (μ), bulk modulus (K) and Lame’s constant (λ). These results also showed that the dynamic elastic properties of jointed specimens significantly improved using cement grouting.

We have developed cross-linked polyrotaxane (cPR) that is composed of moveable cross-links and slide-ring components, in its backbone. The cPR is blended with oil well cement to improve elastic properties, and it has demonstrated improvement in elastic modulus with minimum effect on compressive strength. The optimization of curing time, fluid flow behavior, and dynamic strength development in the presence of cPR in cement are also evaluated. The Young’s modulus and compressive strength are measured at 20 MPa and 150°C to simulate downhole conditions. Remarkably, cement—cPR has, revealed a 33% increase in strain compared to neat cement.

In this paper, an Artificial Intelligence (AI) model is constructed for the behavior prediction, i.e. Young’s modulus, of polymer/carbon-nanotube (CNTs) composites. The AI is proposed to overcome t...

Coatings used in tribological applications often exhibit high hardness and stiffness to achieve high wear resistance. One coating characterization method frequently used is nanoindentation which allows the determination of indentation hardness and indentation modulus among other material properties. The indentation modulus describes the elastic surface behavior during indentation and is, among hardness, a direct indicator for wear resistance. To obtain the true indentation modulus of a coating, it must be measured with varying loads and then extrapolated to zero load. Current recommendation of the standard ISO 14577-4:2016 is a linear extrapolation which fits poorly for nonlinear curves. Such nonlinear curves are commonly found for high hardness mismatches between coating and substrate, for example, superhard tetrahedral amorphous carbon coatings (ta-C) on a steel substrate. In this study, we present a new empirical fit model, henceforth named sigmoid. This fit model is compared to several existing fit models described in the literature using a large number of nanoindentation measurements on ta-C coatings with wide ranges of indentation modulus and coating thickness. This is done by employing a user-independent and model agnostic fitting methodology. It is shown that the sigmoid model outperforms all other models in the combination of goodness of fit and stability of fit. Furthermore, we demonstrate that the sigmoid model’s fit parameter directly correlates with coating thickness and thus allows for a new approach of determining ta-C coating thickness from nanoindentation.

Li-ion solid-state electrolytes (SSEs) have great potential, but their commercialization is limited due to interfacial contact stability issues and the formation and growth of dendrites. In this study, a machine learning regression algorithm was implemented to screen for mechanically superior SSEs among 17,619 candidates. Elasticity information (14,238 structures) was imported from an available database, and their machine learning descriptors were constructed using physiochemical and structural properties. A surrogate model for predicting the shear and bulk moduli exhibited R2 values of 0.819 and 0.863, respectively. The constructed model was applied to predict the elastic properties of potential SSEs, and first-principles calculations were conducted for validation. Furthermore, the application of an active learning process, which reduced the prediction uncertainty, was clearly demonstrated to improve the R2 score from approximately 0.6-0.8 by adding only 32-63% of new data sets depending on the type of modulus. We believe that the current model and additional data sets can accelerate the process of finding optimal SSEs to satisfy the mechanical conditions being sought.

High temperature thermal-mechanical stability of tribological thin coatings is extremely important to a large number of applications in modern industries. DC magnetron sputtering of single metallic element (Cr, Si) and alloy (Ni:Cr) targets formed transition metal nitrides film coatings, CrSiN and CrNiN onto M2 steel. High temperature in-situ synchrotron X-ray diffraction, in the range 25 °C–700 °C, obtained experimental data for a range of structural and mechanical properties. Furthermore, experimental room temperature Nanoindentation measurements, made before and after the in-situ heating cycle, provided corresponding hardness and shear modulus results. The structural results identified microstructure and phase transformation changes, while the mechanical results identified microstrain, hardness, elastic modulus and deformation resistance properties of the coatings. Density functional theory (DFT) and quasi-harmonic approximation (QHA) modelled the high temperature thermal and mechanical properties such as: Young's modulus, shear modulus and thermal expansion coefficients (populated up to 1200 °C). Estimates of hardness are made by correlating the bulk phase hardness and shear modulus, of the CrN and Ni phases, as a function of temperature. Results indicate that Si doping enhances the hardness of the CrN framework, increasing from 29 to 36 GPa and improves the coatings elastic modulus, and resistance to deformation. However the addition of Ni reduced these properties. Furthermore, formation of (Cr,Si)N and Ni(Cr) solid solutions is inferred from DFT, Rietveld and lattice constant analysis.

Graphene possesses a large specific surface area, a high Young's modulus, high fracture strength, high electrical conductivity, and excellent optical performance. It has been widely studied for biomedical use since its first appearance in the literature. This article offers an overview of the latest advances in the design of graphene-based materials for delivery of bioactive agents. To enhance the translation of these carriers into practical use, the toxicity involved is needed to be examined in future research in more detail. In addition, guidelines for standardizing experimental conditions during the evaluation of the performance of graphene-based materials are required to be established so that candidates showing higher practical potential can be more effectively identified for further development. This can streamline the optimization and use of graphene-based materials in delivery applications., Graphical abstract Graphene-based carriers have been widely developed in recent years as carriers of bioactive agents. Along with recent advances in molecular design and engineering, they show practical potential for future use in bioactive agent delivery.Image, graphical abstract

The present research explores the effect of various support system on deformation in a shallow tunnel from North-Western Himalaya, India. The deformation measurements assessed through field investigation were utilized to simulate the pre-existing and the present ground scenario, and furthermore in the evaluation of elastic parameters such as Young’s modulus and Poisson’s ratio through finite element back analysis. Back-analysed model predicted a Young’s modulus of 32 MPa and Poisson’s ratio of 0.3. Afterwards, the effect on the deformation of surrounding groundmass for unexcavated and the present condition were numerically ascribed at three different stages of excavation. The numerical application of forepoling and steel liners showed a marked reduction in the tunnel deformation. The combined effect of applied support methods was also enumerated and compared with individual stabilization method. This assessment may aid engineers and planners working in similar geological conditions, by making the excavation safer, stable and economical.

Pyrolytic carbon (PyC) plays a critical role in many applications for its unique properties. In ceramic composite systems, the elastic properties of PyC at the fiber/matrix interface drive toughening mechanisms, enabling structural performance at increased operating temperatures. PyC expresses a wide range of crystallographic texture depending on fabrication parameters. As a result, modelling and optimization requires direct understanding of the texture-property relationships at the relevant length scales. This research leverages high-resolution transmission electron microscopy (HRTEM) to link the PyC microstructure to the elastic response observed via digital image correlation (DIC) during micropillar compression. The HRTEM and DIC results quantitatively resolve a gradient for microstructural texture and Young's modulus respectively, showing that disordered texture increases compressive stiffness normal to the average orientation of the PyC basal planes. The values for modulus ranged from 55 to 150 GPa, which are large compared to most experimental methods, but may be more realistic considering the uniaxial stress state and length scale. The behavior supports findings from numerical homogenization models, suggesting that this advanced technique may provide a path forward for optimization and validation of these nanoscale elasticity models.

Summary Objective Synthetic vocal fold (VF) models used for studying the physics of voice production are comprised of silicone and fabricated using traditional casting processes. The purpose of this study was to develop and demonstrate a new method of creating synthetic VF models through 3D printing in order to reduce model fabrication time, increase yield, and lay the foundation for future models with more life-like geometric, material, and vibratory properties. Study design Basic science. Methods A 3D printing technique based on embedding a UV-curable liquid silicone into a gel-like medium was selected and refined. Cubes were printed and subjected to tensile testing to characterize their material properties. Self-oscillating VF models were then printed, coated with a thin layer of silicone representing the epithelium, and used in phonation tests to gather onset pressure, frequency, and amplitude data. Results The cubes were found to be anisotropic, exhibiting different modulus values depending on the orientation of the printed layers. The VF models self-oscillated and withstood the strains induced by phonation. Print parameters were found to affect model vibration frequency and onset pressure. Primarily due to the design of the VF models, their onset pressures were higher than what is found in human VFs. However, their frequencies were within a comparable range. Conclusion The results demonstrate the ability to 3D print synthetic, self-oscillating VF models. It is anticipated that this method will be further refined and used in future studies exploring flow-induced vibratory characteristics of phonation.

An advanced fabrication technology of reaction-bonded SiC is developed, which includes the preparation of a C/SiC preform by repeated cycles of phenolic resin impregnation and pyrolysis, followed by infiltration with silicon melt. The use of different number of impregnation stages provides control of carbon content in the preform and the corresponding SiC content in final ceramics. The effect of the impregnation number on the preform characteristics and ceramics composition, thermal and mechanical properties are investigated comprehensively. With an increase of impregnation number up to four, SiC fraction in the ceramics enlarges to 93 vol%, thermal conductivity and Young’s modulus increase to 186 W/(m∙K) and 427 GPa respectively, which are superior to most reaction-bonded SiC. Flexural strength (225 MPa) and thermal expansion coefficient (2∙10−6 K-1) are not dependent on the impregnation number. The obtained results provide an opportunity to design and fabricate reaction-bonded SiC ceramics with a given set of properties.

Ab initio calculation and data mining are very useful methods to predict the interrelationships among structure properties. In this paper, the first-principles modelling based on the density functional theory (DFT) was used to explore the structural, mechanical, and electronic properties of ten hydrides REH2 (RE = La, Ce, Pr, Nd, Sm, Tb, Dy, Ho, Er, Tm). From the present work, it can be noted that LaH2, CeH2, NdH2, and PrH2 compounds crystallizing in the hydrogen-rich cubic phase present good mechanical properties which could be of use to future applications in hydrogen storage. Furthermore, the electronic structures were also evaluated to provide a deep insight regarding their trends and confirm the metallic character of these systems. While, HoH2, DyH2, ErH2, TbH2, TmH2, SmH2 hydrides are mainly hard and rigid systems with high values of the bulk modulus (B), shear modulus (G), Young's modulus (E), micro-hardness (H), and low values of B/G ratio. More significantly, the adopted principal component analysis (PCA) provided an advantageous technique in selecting and identifying the minimum of inputs variables necessary to capture all information of the systems.

Rare-earth zirconate ceramics are conventionally sintered at high temperatures for long durations to achieve a full density. Herein, we synthesized and densified five lanthanide-group rare-earth zirconates (Ln2Zr2O7, Ln = La, Nd, Sm, Eu, Gd) containing different numbers of Ln cations in a high-throughput mode using a novel ultrafast high-temperature sintering technique within a cycle of 5 min, and investigated the effects of components on the structure and properties of the resultant ceramics. Under the high-throughput mode, the same sintering conditions make the analysis and comparison of the results more reasonable. The average grain size decreased while hardness and Young’s modulus increased with an increase in the number of the Ln components in the zirconate ceramics. The mechanisms were ascribed to the sluggish diffusion and lattice distortion effect caused by the increase in entropy.

This work addresses the role of rigid inclusions in determining the elastic modulus of particle-filled colloidal networks by modifying an established fractal scaling model. The approach acknowledges the heterogeneous nature of stress distribution at length scales beyond the colloidal aggregates, while maintaining structural information at the level of individual clusters. This was achieved by introducing a scaling factor to account for system heterogeneity which contains intrinsic information about the network’s capacity to form load-bearing links. Rigid fillers bound to the network induce stress concentration, but additionally serve as junction zones which introduce additional load-bearing pathways. This gives rise to the observed increase in the modulus with filler volume fraction. The proposed relationship between the load-bearing network connectivity and scaling behavior may have additional implications on the fractal dimension determined by rheological methods. Further, this model accommodates an experimentally observed correlation between the scaling behavior of the modulus associated with the addition of fillers and that arising from increasing structurant concentration. The modified fractal model thus provides an alternative view of how fillers contribute to the small- and large-deformation mechanical behavior of filled colloidal gels in a manner consistent with experimental observations.

To analyze the stress of functionally graded materials (FGMs) through an experiment, transparent homogeneous FGMs (THFGMs) with similar theoretical and physical properties need to be created. This study developed such THFGMs and proposed a method for determining their stress intensity factors (SIFs) and T-stresses via photoelastic experiments. The Young’s modulus and Poisson’s ratio of these THFGMs linearly change along the physical variation direction, and the shear modulus varies almost linearly. The SIFs and T-stresses were obtained for the central and edge cracks in finite rectangular FGM plates with linear variations in the shear modulus under constant density along the direction of the crack under mode I loading. The SIFs and T-stresses can be obtained using the exponential and linear variation in the stress fields, even if the physical properties of FGM plates show linear variation in the shear modulus. The characteristics of the experimental SIFs obtained in this study generally agree with those of theoretical SIFs reported in previous research. For center crack tips, the SIFs at the hard right crack tip were greater than those at the soft left crack tip. For edge crack tips, when a/W 0.35, the SIFs were greater than the homogeneous materials. The experimental T-stresses for the center crack agreed well with the numerical T-stresses reported in previous research. For the edge crack, when a/W ≤ 0.3, the experimental T-stresses agreed with the numerical T-stress, but when a/W ≥ 0.4, considerable differences were observed between the experimental and numerical T-stresses. Where a(a) denotes the crack length for edge cracks or half the crack length for center cracks, and W is the width of the specimen. Experimental results coincide well with those reported in the literature, except for the T-stresses for edge crack when a/W > 0.3. Therefore, the THFGMs, which are new FGMs developed in this study, can be effectively used in experimental fracture analysis.

The Expander Body pile (EB) is a combination of a cast-in-situ pile method with an inflated, pump-grouted tip. The EB system's pioneering conjunction with the conventional drilling pile technique has improved work load, foundation security, cost reductions and abrupt displacements in lateritic, porous, unsaturated soils. The aim of this article is to analyze settlement estimates of bored piles equipped with the Expander Body System on tropical lateritic soil, using a deformability modulus obtained from laboratory and field tests. The piles were subjected to compression and uplift load tests. In addition, the estimates of the pile settlement are compared with the measured values, and the findings are discussed. The results strongly support that PMT and SPT tests present the optimal ratios between the measured and estimated settlements for both bored piles and bored piles with the Expander Body System. It can also be observed that CPT tests presented reasonable estimates for tensioned piles. Ultimately, it is verified that straightforward elastic models for the settlement assessment of bored piles can be used reliably in practice for piles equipped with the Expander Body System on tropical unsaturated soils.

We report on the fabrication of oriented collagen films by drying a dilute collagen solution on a polydimethylsiloxane (PDMS) substrate with a micrometer grooved surface. The resultant films show optical and mechanical anisotropy along the groove direction, and have a high mechanical strength with Young's modulus of 2.3 GPa. This process might enable collagen materials to be applied to anisotropic biocompatible substrates, large-area functional scaffolds, and soft robotic materials.

Tensile tests of composite materials based on carbonfiber reinforced plastics (CFRPs) have been performed to benchmark the impact of action of abrasive water jet (AWJ) and high-speed milling (HSM) on the stiffness and strength of CFRP laminates. CFRP specimens were tested according to the ASTM D3039 and ASTM D5766. The drilled specimens exhibited a linear behavior up to failure, but their stress–strain relation was pronouncedly nonlinear, with higher tensile strains than nondrilled ones. Results showed that ultimate the stress–strain relation and Young’s modulus were affected by the machining process. The stress and strain limits for samples prepared using the AWJ method were higher than for those machined by HSM, but the opposite effect was observed for Young’s modulus.

Rubber nanocomposites experiencing dynamic shears at large strain amplitudes (γ) exhibit the nonlinear Payne effect featured by decays of storage and loss moduli (G′ and G″) or by G′ decay accompanied with G″ overshoot near a critical strain amplitude. The occurrence of the Payne effect has been assigned to damages of “filler network” and rubber-filler interfacial interactions for a long time and to Rouse dynamics of rubber chains recently. To solve the dispute, influences of extraction, crosslinking, and paraffin swelling on the Payne effect of carbon black filled natural rubber nanocomposites are investigated systematically. Master curves of G′ as a function of γ could be always created, and overshoot of G″ in the filled vulcanizates weakens with increasing filler content and intensifies by dilution via paraffin swelling, suggesting that the Payne effect is not mainly rooted in the “filler network” and rubber-filler interfacial interactions. The filler reduces the onset strain amplitude of the Payne effect by amplifying microscopic strain amplitude of the rubber phase, irrespective of whether the matrix is crosslinked or not and whether the crosslinked matrix is swollen or not. Partial removal of bound rubber by compounding the paraffin swollen compounds could lower modulus and eliminate G″ overshoot of the deswollen vulcanizates without influence on the mechanism of G′ decay accompanying Payne effect. The overshoot is found to be closely related to the overall viscous characteristic of the vulcanizates in the linear viscoelastic regime. Provided herein are new insights for recognizing the important roles of the viscoelastic rubber phase on the Payne effect of the nanocomposites.

Hydraulic fracturing technology has become an effective technical method of developing tight oil reservoirs, such as an oilfield in Mahu, China. However, numerical simulation of the actual fracture seam network remains problematic. In this paper, we have simulated hydraulic fractures in the Urho Group of the Mahu target layer and analyzed the characterization of the rock mechanics parameters. The results show that Young’s modulus of the Wuerhe domain ranges between 18 and 58.5 GPa, with an average of 32.4 Gpa, the Poisson’s ratio is between 0.21 and 0.38, with an average of 0.31, the brittleness index is between 21.0 and 89.0, with an average of 44.3, and the hydraulic fracturing can form a multi-branch crack modification. The designed direction of horizontal wells in the area is north-south, and the horizontal stress difference is between 4.2 and 9.8 MPa, which facilitates easy fracturing of the reservoir and reforming of a complex seam network. Simulation of the artificial seam network helps to optimize the reasonable parameters of fracturing and the development parameters of horizontal wells in the Mahu 1 well area.

Brittle thin film photovoltaics (PV) that are integrated with load-bearing structures can be subjected to large strains that lead to fragmentation and performance degradation. Such adverse effects can be mitigated, or altogether eliminated, by mechanically isolating a thin PV module from the underlying load-bearing structure. We developed an effective and efficient strain attenuation strategy to eliminate strain transfer from a stiff unidirectional Carbon Fiber Reinforced Polymer (CFRP) laminate to an integrated thin amorphous Si PV module. An analytical model of the three-layer material system (CFRP laminate, interface layer and PV module) was employed to create strain attenuation maps that depend on the length of the PV module and capture the coupled effects of the shear modulus and the thickness of the interface layer (G2, t2), and the Young’s modulus and the thickness of the PV module (E3, t3) through the terms G2/t2 and E3t3, respectively. Based on these strain attenuation maps, polydimethylsiloxane (PDMS) was identified as an effective and versatile interface material, which provided up to 100% strain attenuation between the CFRP laminate and the PV module. After accounting for confinement effects on the effective modulus of the PDMS interface layer, a very good agreement was achieved between the measured and the predicted strain attenuation. Importantly, the PDMS interfacial layer preserved the initial fill factor of the PV module until CFRP laminate failure at 1.7% strain, while in the absence of the PDMS interface the fill factor decreased when the CFRP laminate strain exceeded 0.80%.

This study provides an insight into the structure-property relationship of graphene network (GN) reinforced metal matrix composites (MMCs). Molecular dynamics results show that the interlocking structure improves the deformation compatibility between the GN and matrix, as well as increases the load-sharing of GN. And the mechanical interlocking can be further enhanced by the dislocation-GN interactions as the GN being straightened. The straightening of GN also enables itself to release its stress concentrations through overall deformation, which helps the GN perform better in dislocation-blocking than graphene sheets. Besides, curved portions of GN contribute more to dislocation-GN interactions while the straight portions do better in load-sharing. With the hole-like defects on whether straight or curved portions of GN, both the strength and Young's modulus of the imperfect GN reinforced composites are reduced. However, these defects enable the matrix to be connected into a continuous body, by which the ductility of imperfect GN reinforced Ni matrix composites is improved since their failures are mainly dictated by the fracture of Ni matrix, while the rupture of GN determines the failure of composites reinforced by the GN without hole-like defects.

Additive manufacturing, known as “3D printing”, is a set of manufacturing technologies that can build parts with complex geometries in a process by adding layers of powder material. The laser powder bed fusion (L-PBF) process is characterized by selectively melting layers of particulate material at a micrometer scale in repetitive patterns. This technology is expected to improve Young's modulus of metallic biomaterials, by controlling the microstructure and crystallographic texture– influenced by the laser power and scanning speed parameters which promote an oriented heat extraction. Implant materials should have low Young's modulus, to avoid a large mismatch with that of the bones. This work investigates the role of the laser power and scanning speed on microstructure and crystallographic texture formation of the Nb–48Ti alloy, fabricated by laser powder bed fusion process, using pre-alloyed plasma atomized powder. The microstructure was characterized by optical microscopy (OM), scanning electron microscopy (SEM), backscattered electron diffraction technique (EBSD) for crystallographic texture, and Young's modulus was obtained indirectly via EBSD data. The microstructure showed a cellular dendritic solidification morphology formed by epitaxy at the edge of the melt pools. Texture results indicated that higher values of power and scanning speed favored the increasing of a near-cube-on-face texture and a reduction in Young's modulus.

First-principles approach was applied to investigate the stability, electronic and mechanical properties of Cr2-xNixN (x = 0, 0.083, 0.167,0.250, 0.333) and Cr1-xNixN (x = 0,0.125,0.25,0.375, 0.5). The calculated formation enthalpy and mechanical stability results show that Cr2-xNixN and Cr1-xNixN are all stable. The bulk, shear and Young's modulus results indicate that different variation trend is observed in Cr2-xNixN and Cr1-xNixN with the increase of x. Base on Pugh and Pettifor criteria, Cr2N belongs to the brittle area and the ductility of Cr2-xNixN increases with the increment of x, obtain the maximum results when x = 0.333. However, CrN, which belongs to the ductile area, alloying with Ni decreases its ductility and increases its brittleness, reach the maximum brittleness when x = 0.5. The charge density difference study reveals that the doped Ni atom affects the interaction between Cr and N in Cr2-xNixN and Cr1-xNixN differently. Furthermore, the stress-strain curve of Cr2N, Cr1.833Ni0.167N, and Cr1.667Ni0.333N under shear and tensile deformation shows that the ultimate stress of Cr2N is decreased and its ductility increased. Nevertheless, the stress-strain curve of CrN, Cr0.75Ni0.25N, and Cr0.5Ni0.5N under shear and tensile deformation indicates that the strength of CrN can be enhanced and its deformation process is significantly changed when x = 0.25.

Microcellular injection molding (MIM) is a flexible, efficient, and environmentally friendly foaming technology to prepare plastic foams with complex shapes. However, MIM product suffers from deteriorated mechanical properties, limited weight reduction, and poor surface appearance. In this study, mold-opening microcellular injection molding (MOMIM) was used to prepare high-performance polypropylene/glass fiber (PP/GF) composite foams. GF was used to improve the foaming behavior of PP and to enhance the mechanical properties of foamed samples. Firstly, the crystallization and rheological behavior of PP and PP/GF were analyzed. Afterwards, the foaming behavior of PP and PP/GF in microcellular injection molding process were investigated. Finally, the mechanical properties of PP and PP/GF foams were measured and discussed. It was found that PP/GF composite foams show a rather uniform cellular structure than the pure PP foams. Moreover, PP/GF composite foams exhibit much higher strength and stiffness than the pure PP foams. Furthermore, MOMIM can significantly enhance the flexural modulus of the molded samples. For the foams with an expansion ratio of 1.5-fold, by adding 20 wt% GF, the tensile strength and modulus can be increased by 60% and 50%, respectively. For the PP/GF composite with 20 wt% GF, the foamed sample prepared by MOMIM can have a flexural modulus nearly 200% higher than that of the unfoamed sample. Thus, MOMIM PP/GF composites show a promising perspective in providing lightweight and strong plastic products that can be widely used in automotive, electronics, and appliances.

This research is aimed at investigating the influence of the coal height ratio on the mechanical properties and damage behavior of rock-coal-rock combined samples (RCRCS) under coupled static and dynamic loads. For this purpose, a uniaxial cyclic dynamic loading experiment with four different coal height ratios of RCRCS was conducted. Mechanical properties, failure modes, and wave velocity evolution of RCRCS were analyzed; the process of rock burst under coupled static and dynamic loads in rock-coal-rock combined structure was discussed. The following research results are obtained. (1) The peak strength of RCRCS under static and dynamic load decreases with the increasing coal height ratio as an inverse proportional function. (2) The loading and unloading modulus remains consistent for the same levels of dynamic load; the coal height ratio of 40% may be the limit for the stable value of modulus. (3) The increase of the coal height in RCRCS leads to a gradual increase of the energy release rate; the cracks develop preferentially in coal and then extend to rock sample. The distribution of AE events and damage is consistent with the distribution of passive wave velocity. The research results provide important scientific bases for the guidance of early warning of rock burst.

Considering a homeomorphism of the plane onto itself, we prove that the criterion of quasiconformality is the presence of an upper bound for the modulus of the family of curves joining the images of the opposite sides of an arbitrary oriented square with the sides parallel to the coordinate axes.

Rock mechanical properties play a crucial role in fracturing design, wellbore stability and in situ stresses estimation. Conventionally, there are two ways to estimate Young’s modulus, either by conducting compressional tests on core plug samples or by calculating it from well log parameters. The first method is costly, time-consuming and does not provide a continuous profile. In contrast, the second method provides a continuous profile, however, it requires the availability of acoustic velocities and usually gives estimations that differ from the experimental ones. In this paper, a different approach is proposed based on the drilling operational data such as weight on bit and penetration rate. To investigate this approach, two machine learning techniques were used, artificial neural network (ANN) and support vector machine (SVM). A total of 2288 data points were employed to develop the model, while another 1667 hidden data points were used later to validate the built models. These data cover different types of formations carbonate, sandstone and shale. The two methods used yielded a good match between the measured and predicted Young’s modulus with correlation coefficients above 0.90, and average absolute percentage errors were less than 15%. For instance, the correlation coefficients for ANN ranged between 0.92 and 0.97 for the training and testing data, respectively. A new empirical correlation was developed based on the optimized ANN model that can be used with different datasets. According to these results, the estimation of elastic moduli from drilling parameters is promising and this approach could be investigated for other rock mechanical parameters.

An ecofriendly fiber reinforced polymer (FRP) had been used in the last decade to enhance the short concrete column’s strength and deformation capacity. This study involves the wrapping of FRP sheets with a thickness of 3 mm and 5 mm on a short column, and then the compressive strength is determined. The rectangular columns of size 150 mm × 300 mm are used for this study, and cast under the grades of M20 and M40 are wrapped with GFRP sheets at the thickness of 3 mm and 5 mm. These results are clarified at a specific thickness of the FRP-wrapped columns. It provides a maximum axial compressive strength, and Young’s modulus gets enhanced rigorously when it is to be compared to the normal concrete. This thesis deals with experimental studies of different parameters associated with wrapped glass fiber reinforced polymer (GFRP). In M20 grade, when the 3 mm wrapped specimen and the 5 mm wrapped specimen are compared, the specimen wrapped with 5 mm increases 5.182% more than the specimen wrapped with 3 mm. In M40 grade, when the 0 mm, 3 mm, and 5 mm wrapped specimens are compared, the specimen wrapped with 5 mm increases 2.47% more than the specimen wrapped with 0 mm. The 5 mm wrapping attains the maximum strength.

The linear amplitude sweep (LAS) test is useful for evaluating the fatigue of asphalt binders. In this paper, the combined effects of strain and temperatures are investigated, and a method for esti...

This study aims to promote the concept of using rubber granules from waste tyres as elastic aggregates blended with traditional ballast particles for better performance of rail tracks, i.e. a Rubber Intermixed Ballast System (RIBS). This paper describes the mechanical and compressibility characteristics of RIBS under monotonic loads and a criterion designed to determine the optimum rubber content in the proposed RIBS. The most interesting findings of this study embrace how the rubber granules in the blended rockfill assembly significantly reduce the dilation and modulus degradation, and the breakage of ballast aggregates. RIBS with more than 10% of rubber demonstrates a seemingly consistent reduction in dilation under changing confining pressures. Increased deviator stress and larger effective confining pressure compress the rubber particles within the RIBS which may cause relatively large initial settlements in the ballast layer, if the rubber content becomes excessive. It is also evident from the results that rubber particles ranging from 9.5 to 19 mm with similar angularity to ballast aggregates is advantageous, because, they reduce the breakage of load-bearing larger aggregates, thus effectively controlling ballast fouling within the granular matrix.

Methods for evaluation of Young’s modulus (Em) of structural materials by instrumented indentation using ball indenter have been considered. All these techniques are based on the solution of elastic contact problems performed by H. Hertz. It has been shown that registration of the initial elastic region in the «load – displacement» indentation diagram provides the Em determination for metals and alloys. However, it is necessary to evaluate accurately the elastic compliance of a device, to use an indenter with a large radius R, and ensure a high surface quality of the test material in advance. Methods for Em determation, when indentation diagrams are recorded in the elastoplastic indentation region, should include the effect of plastic deformation on the elastic displacement calculated by H. Hertz expression. However, it appeared essential to determine the relation between the elastic αel and plastic h components of the total elastoplastic displacement α and the elastic displacement α0 estimated by H. Hertz expression for a definite indentation load. A close correlation between α0 and αel is revealed for steels, aluminum, magnesium, and titanium alloys when using indenters with a radius of R = 0.2 – 5 mm (diameter D = 0.4 – 10 mm) and maximum indentation load Fmax = 47 – 29430 N (4.8 – 3000 kgf). It is also shown that a gradual decrease in Em is observed with an increase in R(D) at the same degree of loading F/D2 for the same material. This fact was explained by the scale factor effect.

Under cyclic fatigue loading, hysteresis loops appear in fiber-reinforced ceramic-matrix composites (CMCs) due to composite’s internal damage mechanisms. Loading/unloading inverse tangent modulus (ITMs) of the hysteresis loops reflect the composite’s internal damage state and can be used an effective tool to monitor composite’s fatigue damage evolution and fracture. In this paper, characterization of cyclic fatigue hysteresis loops of CMCs using ITMs are investigated. Loading/unloading ITMs are derived using a micromechanical hysteresis constitutive model considering fatigue damage mechanisms of matrix cracking, interface debonding, wear and slip, and fiber’s failure. Relationships between composite’s fatigue hysteresis loops, ITMs and interface slip state (i.e., interface reverse slip ratio (IRSR) and interface new slip ratio (INSR)) are established. Experimental fatigue hysteresis loops, ITMs, and IRSR/INSR of cross-ply SiC/CAS and SiC/MAS composites from the literature are predicted, and the effects of fiber’s volume fraction, matrix crack spacing, and interface debonding energy on composite’s fatigue hysteresis loops, ITMs, and IRSR/INSR are analyzed.

Nanoporous metals have received significant attention as a new class of structural and functional materials. However, the macroscopic brittle fracture under the tensile test is an impediment to their practical applications. Thus, it is of central importance to develop nanoporous materials with low cost and high tensile ductility. Herein, a nanoporous Cu film supported on a pure Cu substrate (NPC@Cu) was fabricated by utilizing a liquid Ga assisted alloying-dealloying strategy, and the thickness of NPC film can be precisely regulated by changing the mass loading of liquid Ga. In-situ X-ray diffraction was performed to further explore the alloying/dealloying mechanisms. The NPC@Cu films show good tensile mechanical properties with a minimum elongation of 13.5 %, which can be attributed to the good interface bonding and certain modulus matching between the nanoporous Cu layer and the Cu substrate. Our findings demonstrate that the design of film-substrate structure provides a feasible strategy for enhancing the mechanical properties of nanoporous metals.

Mastering mechanical properties of polymers at nanometer scale is highly demanded yet remains challenging. Pioneering advances determined Young's modulus in ultrathin polymer films and attained unprecedented results including rubbery stiffening. However, many viscoelastic properties such as dynamic mechanical behavior of freestanding nanoconfined polymer films are still unknown. Here we demonstrate striking changes of stiffness and the ratio between elastic and viscous responses in thin PDMS films, using a microvibrational system which enables direct measurements of dynamic stress-strain relation of freestanding films. The results show that elastic modulus is enhanced by a factor of 135 in 50 nm films than the bulk, while the viscous response substantially increases at strains >0.05 in 125 nm films. These observations exhibit significant alterations of viscoelasticity under nanoconfinement. With insights on the underlying mechanism of these results, this study is expected to provide new evidence toward gaining a comprehensive understanding of nanoconfinement effect of soft matter.

This study compares the flexural properties of unreinforced and Z-fibre reinforced 3D carbon/epoxy composites. Z-fibre reinforcement is introduced by a novel stitching pattern where uniform distribution of Z-fibres is achieved by inserting linear and angular stitch loops. Flexural tests were performed on both normal and parallel to stitching directions. Z-fibre reinforcement caused reduction in composite density and fibre volume fraction due to local gaps introduced by the needle insertion, which are filled with epoxy resin, resulting in resin rich regions and affecting flexural behaviour. Z-fibre reinforcement reduced the flexural strength and modulus of the composites (up to 27% and 39%, respectively), while the toughness of the Z-fibre reinforced 3D carbon/epoxy system is improved, since damage is more progressive in nature rather than sudden and brittle like fracture. Strain to failure increased from 1.9% to almost 2.8%, a significant improvement, resulting in more damage tolerant behaviour.

The role of bone fatigue damage at the nanostructural level, and its effect on fatigue properties is an understudied and important subject. In this study, nanoindentation was used to probe the micro-mechanical properties of bovine tibiae subjected to fatigue loading in four-point bending. Indentation tests were conducted in the same 30 μm × 120 μm region before fatigue loading and after loading to fracture. Using an optical microscope and scanning electron microscope, the morphology of the initial residual indentation before fatigue loading appeared the same as that after loading to fracture. The mechanical properties calculated using nanoindentation were reduced modulus and hardness, the time constant based on creep, long-term creep viscosity and the dissipated work. Differences of each parameter before loading and post fracture were examined using paired t-tests. The results show that the reduced modulus decreased significantly (p = 9.47 × 10–3) by 7.62–15.16% after fracture whereas the time constant of creep increased slightly (p = 0.049) by 2.81–5.41%. There was no clear change in hardness or dissipated work with fatigue loading. Fatigue loading has the largest effect on bone’s reduced modulus compared to all other mechanical properties.

In the current study, a series of laboratory triaxial loading and unloading experiments were conducted for the purpose of comprehensively understanding the effects on sandstone of loading processes under axial stress conditions and unloading processes under confining pressure conditions. The mechanical properties and crack propagation behaviors of sandstone specimens were analyzed. In addition, a new damage variable based on crack evolution was proposed. The experimental results showed that the strain-softening modulus of the sandstone specimens under triaxial loading and unloading compression conditions decreased with the increases in the loading rate. Meanwhile, the elastic modulus was only observed to undergo small changes. This study found that with the increases in the loading rates of axial stress, the deformation and strength levels of the sandstone specimens also increased. In addition, the crack initiation stress showed a linear increasing trend with the increases in the loading rates of axial stress. The peak crack volumetric strain displayed a slight increase with the loading rate of axial stress, which indicated that the larger the loading rate of axial stress on the sandstone specimens was, the smaller crack propagation strain levels at the peak stress levels would be. The crack propagation velocities were observed to be larger when the loading rates of axial stress were higher. Also, at the same loading rate of axial stress, the crack propagation velocity corresponding to the peak stress of the volumetric cracks was the largest, followed by radial cracks. The crack propagation velocity of the axial cracks was determined to be the smallest. In this study, a new crack damage variable based on crack volumetric strain was proposed. According to the evolution of the crack damage variables of the sandstone specimens, the following four stages of the failure process were obtained: original damage stage; elastic stage; linear damage stage; and accelerated damage stage. The results obtained in this research study provided an important scientific basis for the support of future designs and safety protection measures in underground mining operations.

This paper deals with the problem of finding some upper bound estimates for the maximal modulus of a lucunary polynomial on a disk of radius $$R, R\ge 1$$ under the assumption that the polynomial does not vanish in another disk with radius $$k, k\ge 1$$ . The obtained results generalize as well as sharpen some already known estimates due to [2–5].