Degree Of Anisotropy Research Articles

Dark-field radiography for the detection of bone microstructure changes in osteoporotic human lumbar spine specimens

BackgroundDark-field radiography imaging exploits the wave character of x-rays to measure small-angle scattering on material interfaces, providing structural information with low radiation exposure. We explored the potential of dark-field imaging of bone microstructure to improve the assessment of bone strength in osteoporosis.MethodsWe prospectively examined 14 osteoporotic/osteopenic and 21 non-osteoporotic/osteopenic human cadaveric vertebrae (L2–L4) with a clinical dark-field radiography system, micro-computed tomography (CT), and spectral CT. Dark-field images were obtained in both vertical and horizontal sample positions. Bone microstructural parameters (trabecular number, Tb.N; trabecular thickness, Tb.Th; bone volume fraction, BV/TV; degree of anisotropy, DA) were measured using standard ex vivo micro-CT, while hydroxyapatite density was measured using spectral CT. Correlations were assessed using Spearman rank correlation coefficients.ResultsThe measured dark-field signal was lower in osteoporotic/osteopenic vertebrae (vertical position, 0.23 ± 0.05 versus 0.29 ± 0.04, p < 0.001; horizontal position, 0.28 ± 0.06 versus 0.34 ± 0.04, p = 0.003). The dark-field signal from the vertical position correlated significantly with Tb.N (ρ = 0.46, p = 0.005), BV/TV (ρ = 0.45, p = 0.007), DA (ρ = -0.43, p = 0.010), and hydroxyapatite density (ρ = 0.53, p = 0.010). The calculated ratio of vertical/horizontal dark-field signal correlated significantly with Tb.N (ρ = 0.43, p = 0.011), BV/TV (ρ = 0.36, p = 0.032), DA (ρ = -0.51, p = 0.002), and hydroxyapatite density (ρ = 0.42, p = 0.049).ConclusionDark-field radiography is a feasible modality for drawing conclusions on bone microarchitecture in human cadaveric vertebral bone.Relevance statementGaining knowledge of the microarchitecture of bone contributes crucially to predicting bone strength in osteoporosis. This novel radiographic approach based on dark-field x-rays provides insights into bone microstructure at a lower radiation exposure than that of CT modalities.Key PointsDark-field radiography can give information on bone microstructure with low radiation exposure.The dark-field signal correlated positively with bone microstructure parameters.Dark-field signal correlated negatively with the degree of anisotropy.Dark-field radiography helps to determine the directionality of trabecular loss.Graphical

Homogenization of a random mixture of identically oriented superspheroidal particles

Depolarization dyadics were computed for superspheroidal particles made of an isotropic dielectric material and immersed in a uniaxial dielectric material. Superspheroidal shapes of two kinds were considered: one intermediate between spheroidal and cylindrical, and the other intermediate between spheroidal and cuboidal. These depolarization dyadics were employed in the Maxwell Garnett and Bruggeman homogenization formalisms to estimate the relative permittivity dyadics of homogenized composite materials (HCMs) that are random mixtures of identically oriented superspheroidal particles. The anisotropy of the HCMs was exposed through numerical investigations which revealed the dependencies of the HCM's anisotropy upon the shapes of the constituent particles and their volume fractions. The largest degrees of HCM anisotropy arose when the shape of the constituent particles deviated most from spherical, especially at mid-range volume fractions. Estimates of HCM anisotropy from the Maxwell Garnett and Bruggeman formalisms were broadly similar over the volume-fraction range appropriate for the Maxwell Garnett formalism, with modest differences being most apparent for particle shapes that deviated most from spherical.

Study of strength-ductility and anisotropic behavior of Mg-Gd-Y-Zn-Zr alloy prepared by Equal channel double angular pressing

In the present work, the Mg-Gd-Y-Zn-Zr alloy was processed by Equal channel double angular pressing (ECDAP). The evolution of microstructure and mechanical properties are systematically investigated. The results demonstrate that the strength and ductility after ECDAP can be simultaneously enhanced, which is due to the generation of dynamic recrystallization and unique basal texture with dispersive circular distribution. The anisotropy behavior is also evaluated by the compression testing along different direction. After ECDAP for 4 passes, the anisotropy degree is effectively decreased compared with the sample after ECDAP for 1 pass. Moreover, the deformation behavior during ECDAP process is determined by prismatic slip.

Research on orthotropic anisotropy characteristics of thick bedded limestone based on in situ deformation tests

The orthotropic anisotropy of sedimentary rocks has a significant impact on the force and deformation behavior of the project. In this paper, radial pressurization tests were carried out in the borehole in a typical northern karst area to obtain the deformation properties and orthotropic anisotropy of the rock masses. The test results showed that the deformation modulus and elastic modulus of the limestone rocks in the dam site area obeyed normal distribution. The deformation modulus was basically larger than the proposed deformation modulus of Class II rocks (10 GPa). The deformation behavior and anisotropy degree of the limestone showed a weak correlation with the elevation, but a strong correlation with the development density of the rock joints. The larger development density of the rock in the right bank test section leads to a larger degree of orthotropic anisotropy and frequency of occurrence.

Probing Three-dimensional Magnetic Fields. III. Synchrotron Emission and Machine Learning

Synchrotron observation serves as a tool for studying magnetic fields in the interstellar medium and intracluster medium, yet its ability to unveil three-dimensional (3D) magnetic fields, meaning probing the field’s plane-of-the-sky (POS) orientation, inclination angle relative to the line of sight, and magnetization from one observational data, remains largely underexplored. Inspired by the latest insights into anisotropic magnetohydrodynamic (MHD) turbulence, we found that synchrotron emission’s intensity structures inherently reflect this anisotropy, providing crucial information to aid in 3D magnetic field studies: (i) the structure’s elongation gives the magnetic field’s POS orientation and (ii) the structure’s anisotropy degree and topology reveal the inclination angle and magnetization. Capitalizing on this foundation, we integrate a machine learning approach—convolutional neural network (CNN)—to extract this latent information, thereby facilitating the exploration of 3D magnetic fields. The model is trained on synthetic synchrotron emission maps, derived from 3D MHD turbulence simulations encompassing a range of sub-Alfvénic to super-Alfvénic conditions. We show that the CNN is physically interpretable and the CNN is capable of obtaining the POS orientation, inclination angle, and magnetization. Additionally, we test the CNN against the noise effect and the missing low-spatial frequency. We show that this CNN-based approach maintains a high degree of robustness even when only high-spatial frequencies are maintained. This renders the method particularly suitable for application to interferometric data lacking single-dish measurements. We applied this trained CNN to the synchrotron observations of a diffuse region. The CNN-predicted POS magnetic field orientation shows a statistical agreement with that derived from synchrotron polarization.

An innovative 4D printing approach for fabrication of anisotropic collagen scaffolds

Collagen anisotropy is known to provide the essential topographical cues to guide tissue-specific cell function. Recent work has shown that extrusion-based printing using collagenous inks yield 3D scaffolds with high geometric precision and print fidelity. However, these scaffolds lack collagen anisotropy. In this study, extrusion-based 3D printing was combined with a magnetic alignment approach in an innovative 4D printing scheme to generate 3D collagen scaffolds with high degree of collagen anisotropy. Specifically, the 4D printing process parameters-collagen (Col):xanthan gum (XG) ratio (Col:XG; 1:1, 4:1, 9:1 v/v), streptavidin-coated magnetic particle concentration (SMP; 0, 0.2, 0.4 mg ml-1), and print flow speed (2, 3 mm s-1)-were modulated and the effects of these parameters on rheological properties, print fidelity, and collagen alignment were assessed. Further, the effects of collagen anisotropy on human mesenchymal stem cell (hMSC) morphology, orientation, metabolic activity, and ligamentous differentiation were investigated. Results showed that increasing the XG composition (Col:XG 1:1) enhanced ink viscosity and yielded scaffolds with good print fidelity but poor collagen alignment. On the other hand, use of inks with lower XG composition (Col:XG 4:1 and 9:1) together with 0.4 mg ml-1SMP concentration yielded scaffolds with high degree of collagen alignment albeit with suboptimal print fidelity. Modulating the print flow speed conditions (2 mm s-1) with 4:1 Col:XG inks and 0.4 mg ml-1SMP resulted in improved print fidelity of the collagen scaffolds while retaining high level of collagen anisotropy. Cell studies revealed hMSCs orient uniformly on aligned collagen scaffolds. More importantly, collagen anisotropy was found to trigger tendon or ligament-like differentiation of hMSCs. Together, these results suggest that 4D printing is a viable strategy to generate anisotropic collagen scaffolds with significant potential for use in tendon and ligament tissue engineering applications.

Inferring system parameters from the bursts of the accretion-powered pulsar IGR J17498–2921

ABSTRACT Thermonuclear (type-I) bursts exhibit properties that depend both on the local surface conditions of the neutron stars on which they ignite, as well as the physical parameters of the host binary system. However, constraining the system parameters requires a comprehensive method to compare the observed bursts to simulations. We have further developed the beansp code for this purpose and analysed the bursts observed from IGR J17498$-$2921, a 401-Hz accretion-powered pulsar, discovered during it’s 2011 outburst. We find good agreement with a model having H-deficient fuel with $X=0.15\pm 0.4$, and CNO metallicity $Z=0.0014^{+0.0004}_{-0.0003}$, about a tenth of the solar value. The model has the system at a distance of $5.7^{+0.6}_{-0.5}$ kpc, with a massive (${\approx} 2\ \mathrm{ M}_\odot$) neutron star and a likely inclination of $60^\circ$. We also re-analysed the data from the 2002 outburst of the accretion-powered millisecond pulsar SAX J1808.4$-$3658. For that system we find a substantially closer distance than previously inferred, at $2.7\pm 0.3$ kpc, likely driven by a larger degree of burst emission anisotropy. The other system parameters are largely consistent with the previous analysis. We briefly discuss the implications for the evolution of these two systems.

Study on the creep constitutive model of layered rockconsidering anisotropic and damage factors after hightemperature exposure

The failure of layered rock after high temperature exposure is a major concern in deep underground engineering projects. This paper proposes an improved Nishihara creep constitutive model that considers damage factors and the bedding angle, which overcomes the shortcomings of the deviation in the description of the conventional Nishihara model in the acceleration stage. The constitutive model is verified by the conventional triaxial creepiest. The theoretical curve has a high degree of fitting with the experimental curve. The experimental results show that a temperature of [Formula: see text] has an obvious influence on the steady creep rate and the creep strain of layered sandstone, and [Formula: see text] can be regarded as the temperature threshold for the long-term strength and change from anisotropic to isotropic of layered sandstone. The irreversible melting mixing phenomenon at the boundary of mineral particles with increasing temperature is the mechanism by which different treatment temperatures affect the anisotropy degree of layered rock.

Bruggeman homogenization of a particulate composite material comprising truncated spheres and spheroids.

Closed-form expressions were established for depolarization dyadics&#xD;for a&#xD; truncated sphere and a truncated spheroid, both electrically small, immersed in a uniaxial dielectric ambient medium.&#xD; These depolarization dyadics were used to develop the&#xD; Bruggeman homogenization formalism to predict the relative permittivity dyadic of a homogenized composite material (HCM) arising from a&#xD; randomly distributed mixture of oriented particles shaped as truncated spheres and spheroids. Unlike other homogenization formalisms, most notably the Maxwell Garnett formalism,&#xD; the Bruggeman formalism is not restricted to composites containing dilute volume fractions of constituent particles.&#xD;Numerical investigations highlighted the anisotropy of the HCM and its relation to the shapes of its constituent particles and their volume fractions. Specifically, greater degrees of HCM anisotropy arise from constituent particles whose shapes deviate more from spherical, especially for mid-range volume fractions.

Strain Measurement on a PBX during Temperature Cycling Using Fibre Bragg Gauges

AbstractThe anisotropic and irreversible expansion properties of polymer‐bonded explosives (PBX) can significantly influence the utility and reliability of associated equipment. The physical state of PBX under temperature cycling affects the strain distribution across the surface of cylindrical specimens. This strain is indicative of the irreversible growth and anisotropic expansion of the specimens. In this study, fiber Bragg grating sensors are employed to monitor the strain of PBX throughout the temperature cycling process, and our focus was on analyzing the changes in anisotropy and strain distribution during the cycle. The relationships between strain, temperature, material properties, and differences among various materials are examined. Experimental results indicate that the strain along the height and radial directions of the PBX specimens displayed a monotonic gradient distribution, increasing progressively in areas of higher density. TATB‐based PBX exhibited anisotropic expansion throughout the temperature cycling, with the degree of anisotropy increasing during heating and decreasing upon cooling. Conversely, HMX‐based PBX showed greater expansion in the height direction during both the heating and cooling phases, but it did not display noticeable anisotropy following the temperature cycling. At the highest temperature‐holding stage (100°C), the HMX‐based PBX was isotropic. The extent of strain in PBX was correlated with the thermal expansion coefficient of the crystal, although the final degree of expansion was not dependent on the initial range of strain. The ratchet growth of TATB‐based PBX was approximately 31 μϵ greater than that of HMX‐based PBX.

Uniaxial Molecular Alignment in Thin Films Composed of Discrete NDI‐T2 Oligomers Investigated by Variable‐Angle Spectroscopic and Imaging Ellipsometry

The understanding of the optical characteristics and the influence of thermally induced crystallization is vital to evaluate newly synthesized organic semiconductors for their potential applications. Variable‐angle spectroscopic ellipsometry (VASE) is employed to determine the complex dielectric function of two recently developed discrete oligomers based on naphthalene diimide (NDI) and bithiophene (T2), applying an anisotropic optical model. It is shown that the as‐cast films are optically near‐isotropic, while the annealed films exhibit pronounced anisotropies with respect to the orientation of the π−π* transition. Differences between the two distinct molecules are observed and discussed. The degree of optical anisotropy is quantified using the average molecular orientation angle φ, associated with the orientation of the π−π* transition dipole, and the related orientation order parameter S. The molecules are shown to form crystallites of several microns in size upon annealing. Imaging ellipsometry is thus additionally employed to study their optical anisotropy on a microscopic scale, and the agreement with results from macroscopic measurements is evaluated.

Chitosan-based anion exchange membranes for fuel cell application: Enhanced hydration & durability to dry-wet cycling

Herein, a new type of anion exchange membranes (AEMs) based on chitosan (CS) and poly(4-vinylbenzyl chloride) (PVB) polymers is reported. Depending on whether the PVB side chains are mono-cationic (quaternized PVB, QPVB) or di-cationic (di-quaternized PVB, DQPVB), the AEMs are denoted as QPVB@CS and DQPVB@CS, respectively. Due to the lateral aggregation of chitosan chains assisted by hydrogen bonds, the in-plane expansion is limited (1.4–11.5 % at 80 °C), resulting in excellent mechanical properties of AEMs (dry tensile strength of 55.2–81.0 MPa). And after 10 dry-wet cycles, the AEMs maintain their appearance and show improved mechanical properties. Due to high through-plane swelling degree, AEMs effectively retaining water (water uptake of 272.5–501.5 % at 80 °C) in the AEMs. DQPVB@CS AEMs, with their higher ion content, exhibit superior ionic conductivity (74.2–116.5 mS cm−1 at 80 °C) compared to QPVB@CS (27.7–44.3 mS cm−1 at 80 °C) and achieve a peak power density of 729.6 mW cm−2 in an anion exchange membrane fuel cell (AEMFC), versus 128.1 mW cm−2 for QPVB@CS-2. To the best of our knowledge, the AEMs developed in this study represent the first example of AEMs prepared from chitosan gel membranes, achieving anisotropic swelling degree, high water uptake, and excellent dry-wet cycling resistance without the need for additional chemical cross-linking.

Analysis of Thermoelectric Properties of Hot-deformed Bismuth Telluride Sintered Materials

Bismuth telluride (Bi2Te3)-based alloys are widely used for thermoelectric cooling and power generation at low temperatures, and they are the only commercially available materials for thermoelectric applications below 500 K. The rhombohedral unit cell with a large c/a lattice constant ratio consisting of - Te-Bi-Te-Bi-Te- stacked layers inevitably brings about a large anisotropy in transport properties, which is why texturing is very important in polycrystalline Bi2Te3&lt;/sub alloys for maximum performance. In this report, p and n-type polycrystalline Bi2Te3&lt;/sub alloys were synthesized and hot-deformed to investigate the effects of texturing on thermoelectric properties. Hot deformation (HD) induces the strong alignment of (001) orientations along the compression direction, and a remarkable increase in the orientation factor F of (001) orientations is observed after HD in both p and n-type materials. All of the hot-deformed polycrystalline samples showed increased electrical conductivity (σ), power factor (PF), and thermal conductivity (k) in the in-plane (IP) direction, and vice versa in the out-of-plane (OOP) direction, which makes the IP direction of the hot-deformed bodies more favorable for module fabrication in terms of power factor, for both p and n-type Bi2Te3&lt;/sub-based alloys. However, due to the different degree of anisotropy of k and σ, the figures of merit (zT) were maximized in the OOP direction in the p-type materials after HD, whereas the zTs of the n-type materials were higher in the IP direction. This occurs because the anisotropy factor of electron conduction is higher than that of hole conduction, which more than offsets the advantage of the smaller k in the c-direction of n-type Bi2Te3&lt;/sub. The maximum zT of 1.33 (OOP) and 0.90 (IP) were obtained after HD from the p and n-type Bi2Te3 alloys, respectively, which were 9.3% and 18.4% higher than those of as-sintered materials.

Understanding the influence of drained cyclic preloading on liquefaction resistance of sands using DEM-clump modeling

The soils in situ are subjected to various types of preloading histories. Extensive work has been devoted to understanding the impact of undrained preloading with different strain histories on the reliquefaction resistance of sands. This study primarily examines the effects of drained cyclic preloading histories on the liquefaction resistance of soils using DEM-clump modeling. The effects of preloading stress path and preloading deviatoric stress amplitude on the drained cyclic behavior and subsequent undrained liquefaction response are discussed. Moreover, the evolution of two microscale descriptors, including coordination number Z and fabric anisotropy degree ac, during the total process is analyzed. The results demonstrate that a smaller preloading stress amplitude and an increasing preloading cycle generally increase the liquefaction resistance of sandy soils. In comparison, a larger preloading stress amplitude significantly reduces the liquefaction resistance. We also reveal that drained cyclic preloading histories induce soil samples with different relative densities and fabrics. The relationship between relative density and liquefaction resistance of soils is not unique. Essentially, Z and ac are good indexes for determining the liquefaction resistance of soils with various drained cyclic preloading histories. The primary objective of this study is to elucidate the micromechanical effects of drained cyclic preloading on the liquefaction resistance of sandy soils.

Enhanced Emitting Dipole Orientation Based on Asymmetric Iridium(III) Complexes for Efficient Saturated-Blue Phosphorescent OLEDs.

Three novel asymmetric Ir(III) complexes have been rationally designed to optimize their emitting dipole orientations (EDO) and enhance light outcoupling in blue phosphorescent organic light-emitting diodes (OLEDs), thereby boosting their external quantum efficiency (EQE). Bulky electron-donating groups (EDGs), namely: carbazole (Cz), di-tert-butyl carbazole (tBuCz), and phenoxazine (Pxz) are incorporated into the tridentate dicarbene pincer chelate to induce high degree of packing anisotropy, simultaneously enhancing their photophysical properties. Angle-dependent photoluminescence (ADPL) measurements indicate increased horizontal transition dipole ratios of 0.89 and 0.90 for the Ir(III) complexes Cz-dfppy-CN and tBuCz-dfppy-CN, respectively. Analysis of the single crystal structure and density functional theory (DFT) calculation results revealed an inherent correlation between molecular aspect ratio and EDO. Utilizing the newly obtained emitters, the blue OLED devices demonstrated exceptional performance, achieving a maximum EQE of 30.7% at a Commission International de l'Eclairage (CIE) coordinate of (0.140, 0.148). Optical transfer matrix-based simulations confirmed a maximum outcoupling efficiency of 35% due to improved EDO. Finally, the tandem OLED and hyper-OLED devices exhibited a maximumEQE of 44.2% and 31.6%, respectively, together with good device stability. This rational molecular design provides straightforward guidelines to reach highly efficient and stable saturated blue emission.

Stress distributions and stiffness anisotropy of circumferentially corrugated shells under uniform external pressure

As an excellent pressure structure, circumferentially corrugated shells have been widely used in many fields, such as ocean engineering and aerospace. At present, the circumferentially corrugated shells have only obtained good buckling performance in tests and finite element analysis. However, the corrugated shells have not been further analyzed in theory, and some new problems have been found in tests. The geometrical parameters of shell structures determine the stress distributions and stiffness anisotropy, and the von Mises stress and local stiffness determine the collapse form and collapse location. The relationship between them has not been explained. The study of this problem will be beneficial to establish the active design theory of the circumferentially corrugated shells. Therefore, this paper aims to investigate the von Mises stress and stiffness anisotropy of the circumferentially corrugated shells. Some corrugated shells with uniform thickness and some corrugated shells with non-uniform thickness are established. The parameters used to represent the corrugated structure and the degree of stiffness anisotropy are proposed. The influence of corrugation parameters on the stress distributions and stiffness anisotropy is studied by finite element method and theoretical analysis, the mechanical behaviors of two types of shells under uniform lateral external pressure is perfectly explained. It provides a direction for the design and optimization of these shells. In addition, a new circumferentially corrugated shell is proposed at the end of this paper. It has good mechanical properties, which will make it possible to further reduce its weight.

Effect of microstructural anisotropy and heat treatment on the corrosion behaviour of additively manufactured Ti-6Al-2Sn-4Zr-6Mo alloy

The electrochemical behaviour of Ti-6Al-2Sn-4Zr-6Mo alloy produced by Powder Bed Fusion – Laser Based/Metals has been investigated to identify the corrosion mechanism characteristic of the material processed by additive manufacturing technology. A microstructural characterisation of the material in as-built and heat-treated conditions was carried out to identify the different phases and assess the degree of anisotropy of the additive manufactured material. After that, the corrosion behaviour was studied by potentiodynamic polarisation and electrochemical impedance spectroscopy. Results showed that a homogeneous and compact oxide layer characterises the as-built material due to the presence of a finely dispersed α’’ phase in the β grains. Conversely, in the heat-treated alloy, the corrosion attack proceeds preferentially on the large α phase domains, where the oxide layer is less protective. Despite the anisotropy in the microstructure of the as-built material, the electrochemical behaviour was revealed to be the same for the section parallel and perpendicular to the building direction, noting the less influential factor of grain orientation on corrosion mechanisms.

Контактная задача для трансверсально изотропного слоя с трением

It is investigated the spatial contact problem of asymmetric interaction of two punches on a transversally isotropic layer with friction forces taken into account in an unknown contact domain. The planes of isotropy are parallel to the layer faces. The friction forces are taken into account along one coordinate axis. The lower layer face is subjected to sliding support. The layer material is characterized by five independent elastic parameters. The problem is reduced to an integral equation with respect to the contact pressure with the help of a double Fourier transformation together with the Coulomb law. The anisotropy degree is characterized be three dimensionless parameters arising in the kernel of the integral equation, two of which satisfy characteristic equation. In particular cases, the integral equation coincides with those well-known for the corresponding contact problems with friction for the isotropic layer and half-space. The B.A. Galanov method is used for numerical solutions. A system of the integral equation and integral inequality is considered. A rectangle is taken which a priori contains the unknown contact domain. By introducing special nonlinear operators, the system is reduced to only one nonlinear equation of the Hammerstein type which can be solved by the successive approximations method. The contact domain is determined by nodes at which the function required is positive. The punches are taken in the form of asymmetric elliptic paraboloids. The method allows us to investigate percolation, i.e. the process of junction of the discrete contact domains due to increasing the forces applied and settlements of the punches. Calculations are made for different friction coefficients, materials and relative thicknesses of the transversally isotropic layer.

Nanofluid minimum quantity lubrication assisted grinding force model considering anisotropy of SiCf/SiC ceramic matrix composites

SiCf/SiC ceramic matrix composites with excellent thermal stability, light weight and oxidation resistance have become key components in advanced aircraft engines. Nanofluid minimal quantity lubrication (NMQL) exhibits significant potential in enhancing heat transfer and lubrication efficiency during the grinding process. The technological challenge lies in thoroughly investigating the theoretical variation rule of grinding force, assisted by nanofluid minimal quantity lubrication, and subsequently achieving low-damage machining of SiCf/SiC composites. In this study, a prediction model for the grinding force during NMQL-assisted grinding was established, integrating diverse lubrication methods, grinding wheel geometric parameters, wear degree, process parameters, the anisotropy and damage degree of SiCf/SiC composites. The model was subsequently experimentally validated through grinding tests conducted on SiCf/SiC composites under various conditions, including dry grinding (DG), flood grinding (FG), minimum quantity lubrication (MQL), and carbon nanotube nanofluids (NMQL-CNTs), across multiple grinding depths. The present investigation’s grinding force forecasting model is evidenced to possess high accuracy of precision, showcasing mean deviations of 6.64 % and 11.97 % in the perpendicular (Fn) and tangential (Ft) grinding force components, respectively. Additionally, employing NMQL-CNTs facilitates the achievement of minimal grinding force and surface finish quality. At depths of 0.4 mm and 0.6 mm during grinding, the mean Fn magnitudes under the NMQL-CNTs lubrication approach underwent a decrease of 66.7 % and 74.5 %, respectively, in contrast, the mean Ft magnitudes experienced a reduction of 55 % and 67.2 %, correspondingly, in comparison to the DG lubrication technique. Notwithstanding the consistency in the material’s brittle removal mechanism across varying lubrication strategies, the NMQL-CNTs approach effectively alleviates fiber abrasion. Concisely, the research presented herein provides foundational theoretical insights and practical technological assistance for the achievement of low damage SiCf/SiC composite processing.

Torsion of end-bearing pile foundations in layered anisotropic geomaterials

ABSTRACT An analysis for the torsional dynamic response of end-bearing pile foundations embedded in a layered transversely isotropic geomaterial (soil/rock) is presented. The deformation of the transversely isotropic soil or rock is described by the method of separation of variables. The elasticity theory for a viscoelastic medium with frequency independent hysteretic material damping, and the Extended Hamilton’s Principle are utilised to derive the differential equations describing pile and soil motions. The differential equations are solved analytically in an iterative algorithm. The accuracy of the analysis is verified with existing studies reported in the literature for pile foundations embedded in a homogeneous and layered soil deposit. The effect of the degree of anisotropy on the pile-soil response – dynamic pile-head stiffness, distribution of pile rotation and torque with depth, dimensionless soil displacement function for various values of pile slenderness and pile-soil stiffness ratios in a homogenous soil deposit is investigated. Design charts of static pile-head stiffness in a homogeneous soil deposit for a wide range of pile-soil stiffness and pile slenderness ratios, and degree of anisotropy are also reported. The effect of soil layering for a pile embedded in a two-layered soil deposit is also studied.