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Nozzle shape greatly affects the activity of cells and growth factors inside bio-ink, which is easy to be ignored. In this research, the finite element simulation software based on fluid dynamics theory was used to simulate the extrusion flow behavior of the bio-ink inside the printing needle. By establishing the flow models of two commonly used needles (cylindrical and conical needles), taking sodium alginate solution as bio-ink, the extrusion flow behavior of bio-ink inside the printing needle was simulated. Following, taking steady pressure, flow rate, and fluid shear stress as the research objectives, the response effects of nozzle geometry parameters, including shape, size, and feeding pressure, on the flow behavior of bio-ink were analyzed. Finally, a method based on the idea of integration for evaluating the cumulative damage to the active substances inside bio-ink has been proposed. Results show that the wall shear stress is the main stress suffered by bio-ink in the bio-printing process. Smaller inlet pressure and larger nozzle outlet diameter are beneficial for reducing wall shear stress. Compared with the cylindrical nozzle, although the maximum wall shear stress of the conical nozzle is higher than that of the cylindrical nozzle under the same inlet pressure and outlet nozzle diameter, the time of bio-ink subjected to the wall shear stress is shorter. The cumulative damage of the cylindrical nozzle is 29.65 Pa·s, and that of the conical nozzle is 18.25 Pa·s, which indicates that the conical nozzle has better biofriendliness and less damage to the active substance inside the bio-ink. [ABSTRACT FROM AUTHOR]

The smooth emergence of shear elasticity is a hallmark of the liquid to glass transition. In a liquid, viscous stresses arise from local structural rearrangements. In the solid, Eshelby has shown that stresses around an inclusion decay as a power law r−D, where D is the dimension of the system. We study glass-forming hard sphere fluids by simulation and observe the emergence of the unscreened power-law Eshelby pattern in the stress correlations of the isotropic liquid state. By a detailed tensorial analysis, we show that the fluctuating force field, viz., the divergence of the stress field, relaxes to zero with time in all states, while the shear stress correlations develop spatial power-law structures inside regions that grow with longitudinal and transverse sound propagation. We observe the predicted exponents r−D and r−D−2. In Brownian systems, shear stresses relax diffusively within these regions, with the diffusion coefficient determined by the shear modulus and the friction coefficient. [ABSTRACT FROM AUTHOR]

Coated microbubbles are widely used in medical applications, particularly in enhanced drug and gene delivery. One of the mechanisms underlying these applications involves the shear stress exerted on the cell membrane by acoustic microstreaming generated through cavitation bubbles. In this study, we develop a novel simulation approach that combines the smooth dissipative particle dynamics (SDPD) simulation method with numerical modeling of the Rayleigh–Plesset-like equation in an ad hoc manner to simulate stable cavitation of microbubbles at microsecond and micrometer scales. Specifically, the SDPD method is utilized to model fluid dynamics, while the Rayleigh–Plesset-like equation is employed to describe bubble dynamics. Adopting a 1.5 μm coated microbubble driven by ultrasound with a frequency of 2 MHz and a pressure of 500 kPa as a representative example, we observe a high-velocity microstreaming pattern emerging around the bubble on a very small scale of a few micrometers after only a few microseconds. These spatiotemporal scales may pose challenges for experimental observation. The formation of this microstreaming arises from the opposing motion of the fluid layer next to the bubble and the fluid layers further away. Furthermore, our simulations reveal high shear stress levels of thousands of Pascals exerted on a wall located a few micrometers from the bubble. This contrasts with the shear stress values of a few Pascals calculated from theoretical models in the literature, which do not incorporate radial streaming into their theories. The implications of our results for bubble cavitation-induced pore formation on the cell membrane are discussed in some details. [ABSTRACT FROM AUTHOR]

Molybdenum (Mo) is a strategic metal for the manufacture of aerospace equipment, satellite components, and vehicle armor. Thus, understanding its behaviors under harsh conditions like shock compression is crucial for its practical utilization. Through molecular dynamic simulations, we have explored the mechanical responses and microstructural evolutions of nano-polycrystalline (NPC) Mo under different shock intensities, with grain sizes ranging from 5 to 33 nm. Our study reveals that grain size considerably influences the Hugoniot data and waveform of NPC Mo. NPC Mo with a smaller grain size exhibits higher compressibility and lower Hugoniot shear stress. As the grain size increases, the presence of a double-wave structure becomes more pronounced. Additionally, with the increase in shock intensity, there is a reduction in the shock front width. Significantly, when the shock stress ranges from approximately 60 to 100 GPa, twinning structures are detected in samples with grain sizes ranging from 10 to 33 nm. Moreover, the elevated temperature behind the shock wave further promotes detwinning reactions. When the shock stresses exceed 100 GPa, twinning–detwinning as well as amorphization-recrystallization become the predominant deformation mechanisms, almost unaffected by grain size. As the shock stress exceeds 250 GPa, the atoms in the samples become completely disordered. These findings provide new insights into the mechanical responses as well as the microstructural evolutions of NPC Mo under shock compression. [ABSTRACT FROM AUTHOR]

Basal plane dislocations (BPDs) are a key factor influencing the advancement of the 4H-SiC semiconductor. In this paper, the effects of shear forces on the nucleation and movement of BPDs are revealed by employing molecular dynamics simulations. The stress–strain curves of 4H-SiC subjected to different shear forces at different temperatures are obtained. It is found that the decrease in mechanical properties of 4H-SiC is mainly due to the occurrence of dislocation. This study also delves into the complexities of dislocation entanglement and slip, unraveling the impact on the mechanical properties of 4H-SiC. Moreover, the causes of dislocation within the crystal lattice were clarified from a microscopic atomic vantage point, shedding light on the intricate mechanisms involving chemical bond rupture and regeneration. These findings not only enrich our understanding of BPDs nucleation but also provide invaluable insights for mitigating BPDs in 4H-SiC. [ABSTRACT FROM AUTHOR]

Surface pattern formation of Smart Cut™ silicon-on-insulator (SOI) substrates is investigated using a new process derived from this technology. The local control of SOI surface roughness is achieved by using hetero-temperature surface activated bonding to introduce locally bespoke shear stresses into bonded silicon wafers. The finite element method is used to back up experimental measurements of these large deformations to determine the amount of shear stresses introduced into the structure, and to determine its impact on the fracture mechanism. [ABSTRACT FROM AUTHOR]

Applying an excess entropy scaling formalism to the coarse-grained (CG) dynamics of liquids, we discovered that missing rotational motions during the CG process are responsible for artificially accelerated CG dynamics. In the context of the dynamic representability between the fine-grained (FG) and CG dynamics, this work introduces the well-known Stokes–Einstein and Stokes–Einstein–Debye relations to unravel the rotational dynamics underlying FG trajectories, thereby allowing for an indirect evaluation of the effective rotations based only on the translational information at the reduced CG resolution. Since the representability issue in CG modeling limits a direct evaluation of the shear stress appearing in the Stokes–Einstein and Stokes–Einstein–Debye relations, we introduce a translational relaxation time as a proxy to employ these relations, and we demonstrate that these relations hold for the ambient conditions studied in our series of work. Additional theoretical links to our previous work are also established. First, we demonstrate that the effective hard sphere radius determined by the classical perturbation theory can approximate the complex hydrodynamic radius value reasonably well. Furthermore, we present a simple derivation of an excess entropy scaling relationship for viscosity by estimating the elliptical integral of molecules. In turn, since the translational and rotational motions at the FG level are correlated to each other, we conclude that the "entropy-free" CG diffusion only depends on the shape of the reference molecule. Our results and analyses impart an alternative way of recovering the FG diffusion from the CG description by coupling the translational and rotational motions at the hydrodynamic level. [ABSTRACT FROM AUTHOR]

Shear-force acoustic near-field microscopy (SANM) is employed to monitor stochastic formation and post dynamic response of a water meniscus that bridges a tapered gold probe (undergoing lateral oscillations of a few nanometers amplitude at constant frequency) and a flat (gold or silicon oxide) substrate. As the probe further approaches the substrate, its amplitude decreases. Shear forces (of yet unknown precise origin) are typically invoked to explain the apparently pure damping effects affecting the probe's motion. Herein, SANM measurements underscore instead the role of near-field acoustic emission from the water meniscus as an elastic energy dissipation channel involved in shear interactions. A simplified thermodynamic argument is provided to justify the formation of a water meniscus between the probe and the sample once they are at sufficient separation distance. The reported measurements focus on the role played by the tip's geometry (by using probes of slender and chubby apex termination). The results shed some light on the potential origin of the so-called shear forces, invoked in many scanning probe microscopy applications, but not yet well understood. [ABSTRACT FROM AUTHOR]

Nanostructured high-entropy alloys (HEAs) are promising candidates for extreme load-bearing applications due to their superior performance. In this work, we investigate the deformation behaviors of CoCrFeMnNi HEA under high-speed impact by molecular dynamics simulations. Compared with Al, Ni, and Cu representing pure metals with low to high stacking fault energies, it is found that the CoCrFeMnNi HEA exhibits remarkably low twinning density under shock, despite its extremely low stacking fault energy. Shear loading is then applied to stacking-faulted HEAs and these pure metals to study the evolution of stacking faults under shear stress. The results further show a low tendency for stacking faults to transform into deformation twinning in HEAs, regardless of the initial density of stacking faults. The energy path for deformation twins and stacking faults was calculated, and a direct comparison of fault energies could not explain the deformation mechanism of HEA. We reveal that the inhomogeneous energy profile of dislocation slip caused by the inherent heterogeneity of HEA leads to dispersed stacking fault propagation, which suppresses twinning formation. These results address the spatially tunable defects and further urgent need for the synergistic design of components and microstructures in HEAs. [ABSTRACT FROM AUTHOR]

With large-scale non-equilibrium molecular dynamics simulations and in situ x-ray diffraction analysis, we conducted a systematic investigation into the effects of pre-existing shear strain (γ x y ) on the shock response of single crystal iron. Our findings reveal significant effects of γ x y on the deformation of the crystal structure during shock loading, leading to noticeable alterations in the propagation of shock waves. Specifically, during the elastic stage, the presence of γ x y results in a reduction of shock strength, consequently diminishing the magnitude of elastic lattice strain (ε e ). In the plastic stage, γ x y stimulates the α – ε phase transformation, and structure deformation undergoes a transition from the sequential activity of dislocation-to-transformation to the synchronous activity of dislocation and transformation. This transition inhibits the propagation of plastic waves and consequently broadens the elastic regime. Additionally, the introduction of γ x y activates different slip systems, as it alters the corresponding resolved shear stress. Concurrently, the presence of γ x y triggers the activation of different high-pressure phase variants. Our investigation sheds light on the fundamental physics of iron under shock compression and the influence of pre-existing shear strain on its behavior. [ABSTRACT FROM AUTHOR]

We have previously shown evidence that some individuals seem to consistently minimize low back loads when lifting. while others do not. However, it is unknown why. Individual differences in ability to perceive relevant sensory information may explain differences in minimization of low back loads during lifting, consistent with considering load reduction in one's movement objective in an optimal feedback control theory framework. The purpose of this study was to investigate whether individuals' ability to perceive proprioceptive information (both force- and posture-senses) at the low back was associated with peak low back loads when performing generic or occupation-specific lifts. Seventy-two participants were recruited to perform 10 barbell (generic) and backboard (occupation-specific) lifts, while whole-body kinematics and ground reaction forces were collected. Peak low back compression and anteroposterior shear forces normalized to body mass were calculated as dependent variables. Both posture matching ability and force matching ability at the heavier force targets were associated with lower means and variability of peak low-back loads in both lift types, albeit with small effect sizes (R² 5.17). These findings support the utility of an optimal feedback control theory framework to explore factors explaining interindividual differences in low back loads during lifting. Further, this evidence suggests improving proprioceptive ability may be a useful strategy in lift training programs designed for workplace injury prevention. [ABSTRACT FROM AUTHOR]

A method for characterizing the topological fluctuations in liquids is proposed. This approach exploits the concept of the weighted gyration tensor of a collection of particles and permits the definition of a local configurational unit (LCU). The first principal axis of the gyration tensor serves as the director of the LCU, which can be tracked and analyzed by molecular dynamics simulations. Analysis of moderately supercooled Kob–Andersen mixtures suggests that orientational relaxation of the LCU closely follows viscoelastic relaxation and exhibits a two-stage behavior. The slow relaxing component of the LCU corresponds to the structural, Maxwellian mechanical relaxation. Additionally, it is found that the mean curvature of the LCUs is approximately zero at the Maxwell relaxation time with the Gaussian curvature being negative. This observation implies that structural relaxation occurs when the configurationally stable and destabilized regions interpenetrate each other in a bicontinuous manner. Finally, the mean and Gaussian curvatures of the LCUs can serve as reduced variables for the shear stress correlation, providing a compelling proof of the close connection between viscoelastic relaxation and topological fluctuations in glass-forming liquids. [ABSTRACT FROM AUTHOR]

An extension of a constitutive law for 1,3,5-triamino-2,4,6-trinitrobenzene (TATB) is proposed with a focus on the calibration of a crystal plasticity law. TATB, a highly anisotropic energetic molecular crystal used in explosive formulations, can be subjected to high-pressure and high-temperature conditions, either under high strain-rate deformation or shock loading. The existing thermodynamically consistent model, fully informed by molecular dynamics (MD) simulations, includes nonlinear elasticity as well as a phase-field by reaction pathway formalism under large strain for the modeling of TATB behavior upon pressure as well as its well-known twinning–buckling deformation mechanism. However, it has been observed that TATB single crystal can accommodate large deformations through dislocation-mediated plasticity, a feature not included in the mesoscale model. In the present work, we take advantage of the microscopic flow surface, previously computed through MD calculations, to calibrate a crystal plasticity law, extending the capability of the continuum model currently limited to low velocity impacts and moderate strain rate. Indeed, the microscopic flow surface, defined as a 3D stress-at-first-defect-nucleation contains all information about TATB single crystal mechanical response under directional shear loading, including twinning, buckling, and plastic events. The calibration process uses differential evolution optimization to calibrate TATB basal and transverse slip systems critical stresses to reproduce the microscopic flow surface. Finally, the response of a TATB single crystal to directional loading is investigated in order to evaluate the new model. [ABSTRACT FROM AUTHOR]

We consider a cylinder immersed in viscous fluid moving near a flat substrate covered by an incompressible viscoelastic fluid layer, and study the effect of the fluid viscoelasticity on the lift force exerted on the cylinder. The lift force is zero when the viscoelastic layer is not deformed, but becomes non-zero when it is deformed. We calculate the lift force by considering both the tangential stress and the normal stress applied at the surface of the viscoelastic layer. Our analysis indicates that as the layer changes from the elastic limit to the viscous limit, the lift force decreases with the decrease of the Deborah number (De). For small De, the effect of the layer elasticity is taken over by the surface tension and the lift force can become negative. We also show that the tangential stress and the interface slip velocity (the surface velocity relative to the substrate), which have been ignored in the previous analysis, give important contributions to the lift force. Especially for thin elastic layers, they give dominant contributions to the lift force. [ABSTRACT FROM AUTHOR]

Gas–liquid two-phase stratified flow exists in many industrial processes. Although the flow pattern is simple, the interfacial shear prediction of stratified flow is still the focus of the study. The calculation of the shear stress at the gas–liquid interface is closely related to the measurement of the void fraction and pressure drop of the stratified flow. In this study, a new method for the calculation of interfacial shear stress of gas–liquid two-phase stratified flow is proposed. Differential pressure measurement and planar laser-induced fluorescence technology are combined to obtain important parameters for stratified flow under low-speed flow conditions (Ql = 0.10–0.25 m3/h, Qg = 0.35–1.00 m3/h). The interfacial shear stress is successfully calculated using macroparameters. The uncertainty associated with the calculated parameters using the proposed method is 2.67%, and this study verifies the accuracy of the linear relationship. The method provides a new way to obtain the interfacial shear stress of gas–liquid stratified flow. [ABSTRACT FROM AUTHOR]

We use molecular dynamics to study the mechanism of deformation twinning of β -1,3,5,7-tetranitro-1,3,5,7-tetrazocane (β -HMX) in the P 2 1 / n space group setting for the twin system specified by K 1 = (101) , η 1 = [ 10 1 ¯ ] , K 2 = (10 1 ¯) , and η 2 = [ 101 ] at T = 1 and 300 K. Twinning of a single perfect crystal was induced by imposing increasing stress. The following three forms of stress were considered: uniaxial compression along [ 001 ] , shear stress in the K 1 plane along the η 1 direction, and shear stress in the K 2 plane along the η 2 direction. In all cases, the crystal transforms to its twin by the same mechanism: as the stress increases, the a and c lattice parameters become, respectively, longer and shorter; soon after the magnitude of a exceeds that of c the system undergoes a quick phase-transition-like transformation. This transformation can be approximately separated into two stages: glide of the essentially intact { 101 } crystal planes along ⟨ 10 1 ¯ ⟩ crystal directions followed by rotations of all HMX molecules accompanied by N-NO 2 and CH 2 group rearrangements. The overall process corresponds to a military transformation. If uniaxial compression along [ 001 ] is applied to a β -HMX crystal which is already subject to a hydrostatic pressure ≳ 10 GPa, the transformation described above proceeds through the crystal-plane gliding stage but only minor molecular rearrangements occurs. This results in a high-pressure phase of HMX which belongs to the P 2 1 / n space group. The coexistence curve for this high-pressure phase and β -HMX is constructed using the harmonic approximation for the crystal Hamiltonians. [ABSTRACT FROM AUTHOR]

Nanograined materials possess ultrahigh strength, while their processing and technological applications are constrained by inherent thermal and mechanical instability. Existing experiments show that the stability of Cu nanograins can be enhanced by performing a rapid heating pretreatment that reduces the grain boundary (GB) energy by changing the GB structure. The variation in the GB structure inevitably affects the migration mechanism of GBs. However, the effect of the pretreatment-induced variation in migration mechanisms on stability remains unclear. Here, the shear deformation of a series of ⟨ 100 ⟩ symmetrical tilt GBs after rapid heating pretreatment is systematically investigated by molecular dynamics simulations. The simulations of unheated GBs are also included for comparison. Our results show that the rapid heating pretreatment does not improve the mechanical stability of GBs with tilt angles larger than 36.87° but rather enhances the mechanical stability of those with tilt angles less than 36.87° by the transformation of migration behavior from the normal ⟨ 110 ⟩ mode to (i) a ⟨ 100 ⟩ mode; (ii) an inhomogeneous mixed one that reconciles the ⟨ 110 ⟩ and ⟨ 100 ⟩ modes; and (iii) an inhomogeneous ⟨ 110 ⟩ mode. The former leads to an increase in the critical shear stress that is required to initiate the migration, whereas the latter two result in a decrease in the migration distance. The variation in the GB migration mechanism is attributed to the change in the GB structure from an ordered kite structure to a disordered one. The research gives an atomic insight into the stabilizing mechanism of nanocrystalline materials with rapid heating pretreatment. [ABSTRACT FROM AUTHOR]

Cutting of soft materials is a complex problem, which is still not well understood at the fundamental level, especially for soft materials. The cutting process we consider is slicing, which starts with indentation, followed by sliding of a knife on the material to be cut. Here, we describe cutting experiments on PDMS elastomers with three different moduli. Our experiments reveal typical stages of this cutting process, starting with indentation and ending at steady state cutting. The process starts with a pre-cutting phase in which the blade does not slip grossly relative to the solid to be cut, and deformation is mostly elastic. Slip of the blade initiates suddenly and is often accompanied by initiation of cutting. Cutting is relatively smooth in the next stage, which requires a continuous increase in shear force. For soft PDMS, this smooth cutting stage is followed by one in which folds or creases form on the cutting surface. The corresponding shear force response is no longer smooth as "steady" sliding occurs in a stick–slip fashion with oscillatory forces. The average shear force reaches a plateau and no longer increases with shear displacement. Experimental observations of the various cutting stages are interpreted quantitatively. [ABSTRACT FROM AUTHOR]

A significant challenge in the treatment of central nervous system (CNS) disorders is represented by the presence of the blood--brain barrier (BBB), a highly selective membrane that regulates molecular transport and restricts the passage of pathogens and therapeutic compounds. Traditional in vivo models are constrained by high costs, lengthy experimental timelines, ethical concerns, and interspecies variations. In vitro models, particularly microfluidic BBB-on-a-chip devices, have been developed to address these limitations. These advanced models aim to more accurately replicate human BBB conditions by incorporating human cells and physiological flow dynamics. In this framework, here we developed an innovative microfluidic system that integrates thin-film electrodes for non-invasive, real-time monitoring of BBB integrity using electrochemical impedance spectroscopy (EIS). EIS measurements showed frequencydependent impedance changes, indicating BBB integrity and distinguishing well-formed from non-mature barriers. The data from EIS monitoring was confirmed by permeability assays performed with a fluorescence tracer. The model incorporates human endothelial cells in a vessel-like arrangement to mimic the vascular component and three-dimensional cell distribution of human astrocytes and microglia to simulate the parenchymal compartment. By modeling the BBB-on-a-chip with an equivalent circuit, a more accurate trans-endothelial electrical resistance (TEER) value was extracted. The device demonstrated successful BBB formation and maturation, confirmed through live/dead assays, immunofluorescence and permeability assays. Computational fluid dynamics (CFD) simulations confirmed that the device mimics in vivo shear stress conditions. Drug crossing assessment was performed with two chemotherapy drugs: doxorubicin, with a known poor BBB penetration, and temozolomide, conversely a specific drug for CNS disorders and able to cross the BBB, to validate the model predictive capability for drug crossing behavior. The proposed sensorized microfluidic device represents a significant advancement in BBB modeling, offering a versatile platform for CNS drug development, disease modeling, and personalized medicine. [ABSTRACT FROM AUTHOR]

Stacking faults (SFs) could be generated in aluminum (Al) via full dislocations extension under extreme stress. However, the extension behavior of the dislocations related to the stress conditions have not been studied comprehensively. In this study, SFs were generated solely under extreme stress condition in coarse–grained Al nanocomposites, where high content of Silicon Carbide nanowires (SiCnw) was introduced as reinforcement. Dislocation extension behaviors under normal and shear stress were predicted using an atomistic approach comparing with experiment methods. The extension ability of full dislocations was studied in terms of complex stress forced on partial dislocations and the relationship between stress condition and the SF width was established by stress analysis. The generated SFs were further proved to offer superb additional strengthening effect for the composites. This study provides a new idea and theory for designing of SF generation in coarse–grained Al based nanocomposites. [ABSTRACT FROM AUTHOR]

The stenosis builds up and its progression in the artery causes serious damages, which may lead to death. This research aims to investigate the non-Newtonian properties of the pulsatile blood flow through the multi-stenotic inclined artery. The effect of external body acceleration is considered, and blood is taken as Rabinowitsch fluid in this work. The mathematical model representing the proposed problem is transformed into a dimensionless form by applying the assumption for mild stenosis. The dimensionless mathematical equations are solved using the perturbation method. The solutions of mathematical equations are investigated graphically to analyze the impacts of various physical constraints. We find that strong non-Newtonian effects lead to an increase in flow velocity and wall shear stress. The stenosis's presence and progression in the artery reduces the flow velocity. The stenotic artery (diseased artery) is found to have less flow rate than the healthy artery. It is noted that the vertically held conduit effectively has a larger flow velocity and wall shear stress than the horizontal one. External body acceleration is noted to have an impact that raises velocity and wall shear stress. [ABSTRACT FROM AUTHOR]

Loose granular materials may also exhibit instability behaviors similar to liquefaction under drained conditions, commonly referred to as diffuse instability, which can be studied through constant shear drained (CSD) tests. So far, the research on CSD in binary mixtures is still insufficient. Therefore, a series of numerical tests using the discrete element method (DEM) were conducted on binary mixtures under CSD path. The possible model of instability is categorized into type I and type II, type I instability occurs prior to reaching the critical state line (CSL), whereas type II instability occurs after exceeding the CSL. The study analyzes the macroscopic instability behavior and the impact of fine content (FC) on macroscopic instability behavior. The numerical results show that as FC increases, the slope of the instability line (IL) increases initially and then falls in the p‐q plane. In the e‐p plane, the IL decreases initially and then ascends. The instability type of the binary mixtures is influenced not only by relative density but also by FC. The stability index increased first and then decreased with the increase of FC. The microscopic origin of binary mixtures instability is explored by investigating the fabric‐stress relationship. The collapse of the weak contact sub‐network triggers the specimen instability, while the strong contact sub‐network dictates the difficulty of achieving instability. FC influences the evolution of fabric anisotropy of the strong and weak contact networks, thereby controlling the macroscopic instability behavior of binary mixtures. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the possibility of predicting the yield curves of sandstones considering only a few key mechanical parameters, and more importantly microstructural properties. Porous rocks are modeled as a set of 2D circular grains subjected to radial and axial stresses that reflect the external forces applied on the material. The contact between individual grains define local planes. The sample is assumed to yield at the inception of nonlinear response on one of these planes, when local stresses reach either shear, tensile, or compressive limit values. A Mohr–Coulomb criterion is considered, with a tensile cutoff and a limitation on the maximum allowable shear stress. The parameters of the developed yield equations are then divided into two groups. The first category relates to the microstructure of the material: porosity, grain radius, intergranular contacts radius, and intensification factor. The second category contains a set of four mechanical properties: the cohesion, the friction angle, the maximum shear, and the compressive limit. While the first set differs from one sandstone to another, the second one is assumed to be the same for all sandstones showing similar mineral compositions. The experimental data for five sandstones, Berea, Boise, Darley Dale, Diemelstadt, and Rothbach, are gathered from the literature. The mechanical parameters are calculated based on Rothbach sandstone experimental data. Satisfactory predictions of the yield limits for the remaining sandstones are obtained from their microstructural characteristics. [ABSTRACT FROM AUTHOR]

Ceramic matrix composites (CMCs) have been widely used in aerospace thermal-structures due to their excellent high-temperature performance. It is essential to understand the damage evolution of CMCs. However, in previous research work, the effect of thermal stress induced damage during CMCs fabrication on tensile response was often ignored. A damage evolution model that considers axial and radial thermal stresses to predict tensile response of unidirectional ceramic matrix composites was proposed in this study. The average relative errors between the current prediction and experimental data in the literature were calculated as 1.64 % and 1.91 %, validating this approach. Meantime, the damage evolution laws of interface debonding and the critical stress of matrix cracking in the Budiansky–Hutchinson–Evans (BHE) model were corrected to satisfy the discontinuous interfacial shear stress. According to the experimental data, the current model predicted critical stresses of matrix cracking better than the BHE model, with error rate reductions of 6.52 % and 15.38 %. [ABSTRACT FROM AUTHOR]

ABSTRACT Meat preservation processes have been widely studied over time, especially those related to low temperatures (freezing and freeze‐drying); however, there is very little research that directly relates the effect of these processes on the structure of meat—and the main meat proteins—and how these changes affect some attributes of the final quality. Pork loin meat (Longissimus thoracis) was used, which was frozen–thawed and freeze‐dried‐rehydrated to subsequently evaluate changes in its chemical composition and physicochemical parameters such as water activity (aw), pH, and water‐holding capacity. Physical aspects such as color profile, surface myoglobin fraction, shear force, and histological sections were also evaluated, along with thermal analysis by modulated differential scanning calorimetry. The data obtained were analyzed through different statistical techniques. It was found that the freeze‐drying process significantly modifies the interactions of water with the rest of the meat components (p < 0.05), promoting differences concerning samples that were only frozen, allowing us to establish the importance of water and its associations with each other and with proteins on their effect on meat preservation processes at low temperatures. [ABSTRACT FROM AUTHOR]

ABSTRACT Reported in this paper is a cutting‐edge computational investigation into the influence of geometric characteristics on abdominal aortic aneurysm (AAA) rupture risk, beyond the traditional measure of maximum aneurysm diameter. A Comprehensive fluid–structure interaction (FSI) analysis was employed to assess risk factors in a range of patient scenarios, with the use of three‐dimensional (3D) AAA models reconstructed from patient‐specific aortic data and finite element method. Wall shear stress (WSS), and its derivatives such as time‐averaged WSS (TAWSS), oscillatory shear index (OSI), relative residence time (RRT) and transverse WSS (transWSS) offer insights into the force dynamics acting on the AAA wall. Emphasis is placed on these WSS‐based metrics and seven key geometric indices. By correlating these geometric discrepancies with biomechanical phenomena, this study highlights the novel and profound impact of geometry on risk prediction. This study demonstrates the necessity of a multidimensional assessment approach, future efforts should complement these findings with experimental validations for an applicable approach for clinical use. [ABSTRACT FROM AUTHOR]

The purpose of this work was to determine the essence of the influence of the impact velocity (5, 7, and 9 m/s) on Hertzian stresses and the erosion mechanism of ferritic-pearlitic S355J2 steel. The investigations were carried out using a slurry pot tester. S355J2 steel showed a strong sensitivity to changes in impact velocity. A significant increase in erosion rate was observed at a velocity of 9 m/s. This increase was 5-fold and over 15-fold compared to velocities of 7 m/s and 5 m/s, respectively. The study of Hertzian stress is crucial in erosion research because it helps understand how impact energy is absorbed by the eroded material and the mechanisms that cause surface wear. A linear increase in mean contact pressure and maximum shear stress was observed with increasing impact velocity. The mean contact pressure increased from 4.3 GPa to 5.5 GPa and the maximum shear stress increased from 2.0 GPa to 2.5 GPa. The kinetic energy of the solid particles that hits the eroded steel is distributed in the contact area, which leads to various deformations and wear mechanisms. The primary type of deformation was fatigue degradation of the surface layers of the eroded steel. The high kinetic energy of solid particles contributed to the formation of plastic deformations and strongly deformed steel flakes. Higher impact velocities generally result in greater forces and contact stresses on the material surface. This led to the intensification of plastic deformation in the contact areas and increased the Hertzian stresses. [ABSTRACT FROM AUTHOR]

Highlights Considering their simplicity, processibility, and tunable rheological properties, polymer composite‐type precursors hold exceptional promise in the processing of polymers, ceramics, metals, and their composites. This large variety of precursors used in many different applications cover a large compositional space with dramatically varying rheological properties. Understanding how precursor composition influences their rheological properties is a key need towards streamlining the design and implementation of these precursors. With regard to this design advancement, this study elucidates the composition‐rheology relationships of graphene‐poly(ethylene) oxide (PEO) composite inks as a sample polymer composite‐type precursor. To this end, shear and extensional rheology of numerous compositions were studied across a wide compositional space, which varied graphene concentration, total solid concentration, and binder molecular weight. These studies showed that composition greatly affected various rheological parameters, such as the overall presence of yielding behavior. Specifically, this study illustrated the influence of (i) binder structure, (ii) total solid loading, and (iii) binder‐filler interactions on ink rheology. Extensional rheology was studied to examine how relaxation behaviors were dependent on composition and explicate how relaxation behaviors coincide with responses to shear forces. In tandem, our results illuminate significant composition‐rheology relationships in polymer composite‐type precursors. Rheology of polyethylene oxide‐graphene composite precursors were studied. Shear and extensional rheology, and their correlations were investigated. Composition‐binder molecular weight‐yielding relationships were elucidated. Extensional relaxation regimes were identified with respect to composition. Results can be used to determine compositional ranges for different processes. [ABSTRACT FROM AUTHOR]

ABSTRACT This study investigates the shear fracture behaviors in ultra‐high‐performance concrete (UHPC) under direct shear conditions using Z‐shaped specimens and acoustic emission (AE) monitoring. The effect of steel fiber (SSF) contents (1%, 2%, 2.5%, and 3%) on the failure process and the relative slip of cracks at different loading stages were measured and evaluated. The results indicate that increasing the SSF content significantly enhances the ultimate shear stress and ductility, effectively limits crack propagation and formation, and reduces the extent of damage for UHPC. During the failure process, an increase in the SSF content results in higher cumulative AE energy and a tendency for the peak frequency to shift towards the low‐frequency range. Additionally, increasing the SSF content expands the range of wavelet entropy values and delays the occurrence of wavelet entropy. Due to the reinforcement effects of SSF, the primary crack type evolved from shear to tensile during the failure process. [ABSTRACT FROM AUTHOR]

Reinforcing bars in structural concrete are typically designed to carry axial forces. Nevertheless, due to their bending stiffness, the bars can also carry transverse forces, that are associated with the localized bending mechanism (dowel action) resulting from the relative displacements (or slip) wherever a crack interface or a discontinuity interface (between two concrete parts cast at different times) intercept the bar. Such localized bending induces stress concentrations in both the bars and the concrete. The relative displacement can occur at interfaces either perpendicular to the bar or inclined with respect to its axis. Thanks to steel ductility, the bending stresses in the bars due to dowel action do not impair the sectional capacity at the ultimate limit state. Fatigue verifications, however, require an accurate evaluation of these stresses under imposed transverse displacements or shear forces. As well known, dowel action can be described by means of the traditional unidimensional Winkler's model (beam on an elastic foundation), where the bearing stiffness of the concrete embedment is typically introduced through a couple of parameters, namely the bar diameter and the concrete strength in compression. The actual behavior of a dowel, however, is definitely more complex and for such a reason, improvements are needed for the Winkler's model to introduce other parameters typical of actual structures. Hence, a new formulation is introduced in this study for the bearing stiffness, that is calibrated based on mechanical considerations and measurements with optical fibers. The proposed formulation also accounts for the following parameters: angle between the crack and the bar, concrete‐cover thickness, number of load cycles and the softening effect caused by the local secondary cracks radiating from bar ribs during the pull‐out process. The predictions of the model—implemented with the proposed bearing stiffness—fit fairly well the test results under both monotonic and cyclic loads, in terms of shear force–transverse displacement response and peak stress in the reinforcing bars. [ABSTRACT FROM AUTHOR]

Starch is an important and abundant macromolecule which has a wide application in food, textile, pharmaceuticals, etc. Due to this, a novel characteristic of the starch is necessary compared to native starch which has limited application due to high shear stress, digestibility, strong hydrophobicity, low thermal stability, mechanical strength, as well as high retrogradation and syneresis. These limitations can be overcome through starch modification. However, most starch modifications are not environmentally and energy‐sustainable while some chemical methods have led to the release of hazardous substances into the environment. To surmount these challenges, there is a need for sustainable methods of starch modification to bring about desirable properties. Therefore, this article reviews critically some sustainable technologies such as pulsed electric field, cold plasma treatment, ultrasonication, microwave, gamma radiation, and dynamic pressure used in starch modification. Their effects on the physicochemical and functional properties of starch such as crystallinity, granular, and molecular structures are reviewed. Applications of the starch as affected by various sustainable techniques in various food and non‐food systems are also reviewed. In general, the sustainable techniques of starch modification improve the functionalities of the starch and help in meeting the ever‐increasing market for reliable food and industrial ingredients. [ABSTRACT FROM AUTHOR]

Shear stress, resulting from fluid flow, is a fundamental mechanical stimulus affecting various cellular functions. The epididymis, essential for sperm maturation, offers a compelling model to study the effects of shear stress on cellular behavior. This organ undergoes extensive proliferation and differentiation until puberty, achieving full functionality as spermatozoa commence their post‐testicular maturation. Although the mechanical tension exerted by testicular fluid is hypothesized to drive epithelial proliferation and differentiation, the precise mechanisms remain unclear. Here we assessed whether the responsiveness of the epididymal cells to shear stress depends on functional primary cilia by combining microfluidic strategies on immortalized epididymal cells, calcium signaling assays, and high‐throughput gene expression analysis. We identified 97 genes overexpressed in response to shear stress, including early growth response (Egr) 2/3, cellular communication network factor (Ccn) 1/2, and Fos proto‐oncogene (Fos). While shear stress triggered a rapid increase of intracellular Ca2+, this response was abrogated following the impairment of primary ciliogenesis through pharmacological and siRNA approaches. Overall, our findings provide valuable insights into how mechanical forces influence the development of the male reproductive system, a requisite to sperm maturation. [ABSTRACT FROM AUTHOR]

Piezo1 is a mechanically activated cation channel that converts mechanical force into diverse physiological processes. Owing to its large protein size of more than 2,500 amino acids and complex 38-transmembrane helix topology, how Piezo1 is post-translationally modified for regulating its in vivo mechanotransduction functions remains largely unexplored. Here, we show that PKA activation potentiates the mechanosensitivity and slows the inactivation kinetics of mouse Piezo1 and identify the major phosphorylation site, serine-1612 (S1612), that also responds to PKC activation and shear stress. Mutating S1612 abolishes PKA and PKC regulation of Piezo1 activities. Primary endothelial cells derived from the Piezo1-S1612A knockin mice lost PKA- and PKC-dependent phosphorylation and functional potentiation of Piezo1. The mutant mice show activity-dependent elevation of blood pressure and compromised exercise endurance, resembling endothelial-specific Piezo1 knockout mice. Taken together, we identify the major PKA and PKC phosphorylation site in Piezo1 and demonstrate its contribution to Piezo1-mediated physiological functions. [Display omitted] • Potentiation of Piezo1 channel activities by PKA- and PKC-mediated phosphorylation • Identification of S1612 in Piezo1 as the major PKA and PKC phosphorylation site • Endothelial Piezo1 is regulated by PKA and PKC phosphorylation at S1612 • S1612A knockin mice show alterations of blood pressure and exercise performance Zhang et al. discovered a conserved phosphorylation site, serine-1612, in Piezo1 that mediates PKA- and PKC-dependent phosphorylation and potentiation of the mechanically activated channel activities. Serine-1612 phosphorylation of endothelial Piezo1 regulates Piezo1-mediated in vivo mechanotransduction functions in controlling blood pressure homeostasis and exercise performance. [ABSTRACT FROM AUTHOR]

Polymer composites with continuous fibers are expected to exhibit good mechanical performance due to orientation and high aspect ratio of fillers. Fused filament fabrication (FFF) provides an affordable method for processing these materials as products with tunable architecture. By incorporating continuous bioactive fibers coated with biodegradable polymer, the degradation rate of printed scaffolds may vary over time. As proof of concept, macroporous composites were 3D printed using continuous glass fiber‐reinforced polycaprolactone filament. Parametrization and challenges associated with printing on non‐dedicated equipment are discussed. A model describing the melt flow was employed to evaluate the velocity and shear rate profiles. Although the maximum velocity is approximately 18 mm s−1 for both neat and reinforced polymer, the obstruction caused by fibers results in higher shear rate, up to 481 s−1, higher pressure gradient, 1.95 MPa mm−1, and higher velocity gradient, conditions that limit print quality. Additionally, it was also possible to determine the shear stress experienced by the fiber bundle, 300 KPa, and the influence of different processing conditions. This investigation advances the development and understanding of manufacturing of continuous fiber‐reinforced polymers via FFF. [ABSTRACT FROM AUTHOR]

Osteocytes' response to dynamic loading plays a crucial role in regulating the bone mass but quickly becomes saturated such that downstream induction of bone formation plateaus. The underlying mechanisms that downregulate osteocytes' sensitivity and overall response to loading remain unknown. In other cell types, purinergic signaling through the P2Y2 receptor has the potential to downregulate the sensitivity to loading by modifying cell stiffness through actin polymerization and cytoskeleton organization. Herein, we examined the role of P2Y2 activation in regulating osteocytes' mechanotransduction using a P2Y2 knockout cell line alongside conditional knockout mice. Our findings demonstrate that the absence of P2Y2 expression in MLO-Y4 cells prevents actin polymerization while increasing the sensitivity to fluid flow-induced shear stress. Deleting osteocytes' P2Y2 expression in conditional-knockout mice enabled bone formation to increase when increasing the duration of exercise. Overall, P2Y2 activation under loading produces a negative feedback loop, limiting osteocytes' response to continuous loading by shifting the sensitivity to mechanical strain through actin stress fiber formation. [ABSTRACT FROM AUTHOR]

As train speeds increase, the aerodynamic effects generated during the passage of high-speed trains in tunnels become more pronounced. This article investigates the influence of line spacing on the aerodynamic forces during the passage of high-speed trains in tunnels at different speeds. The research methodology is based on the three-dimensional transient compressible Reynolds-averaged Navier-Stokes (RANS) equations and the k-ω Shear Stress Transport (SST) turbulence model, using overset grid technology to simulate the train passing process in the tunnel. The results show that the aerodynamic drag, lateral force, and lift experienced by the train increase as the line spacing decreases and as the speed increases. line spacing has the greatest impact on aerodynamic lift, followed by lateral force, with drag having the smallest impact. Compared to line spacing, speed has a much larger effect on aerodynamic forces. The aerodynamic forces experienced by the train during tunnel passage are proportional to the square of the train's speed and have an exponential relationship with the line spacing during train passage. [ABSTRACT FROM AUTHOR]

ABSTRACT The mechanisms leading to aneurysm occlusion after treatment with flow‐diverting devices are not fully understood. Flow modification induces thrombus formation within the aneurysm cavity, but fibrin can simultaneously accumulate and cover the device scaffold, leading to further flow modification. However, the interplay and relative importance of these processes are not clearly understood. A computational model of fibrin accumulation and flow modification after flow diversion treatment of cerebral aneurysms has been developed under the guidance of in vitro experiments and observations. The model is based on the loose coupling of flow and transport‐reaction equations that are solved separately by independent codes. Interaction or reactive terms account for thrombin production from prothrombin stimulated by thrombogenic metallic wires and inhibition by antithrombin as well as fibrin production from fibrinogen stimulated by thrombin and flow shear stress, and fibrin adhesion to device wires and already attached fibrin. The computational model was demonstrated and tested on idealized vessel and aneurysm geometries. The model was able to reproduce the salient features of fibrin accumulation after the deployment of flow‐diverting devices in idealized in vitro models of cerebral aneurysms. Namely, fibrin production in regions of high shear stress, initial accumulation at the inflow zone, and progressive occlusion of the device and corresponding flow attenuation. The computational model linking flow dynamics to fibrin production, transport, and adhesion can be used to investigate and better understand the effects that lead to fibrin accumulation and the resulting aneurysm inflow reduction and intra‐aneurysmal flow modulation. [ABSTRACT FROM AUTHOR]

Based on the shear flow theory for thin‐walled sections, a method for calculating the shear stress nonuniformity coefficient (µ) of a thin‐walled section is proposed according to the energy principle, and the formulas for calculating the µ values of several common sections are derived. The obtained µ value of a box section increases as the aspect ratio increases. Compared with commonly used calculation methods, the proposed method gives more reasonable results and shows that the effect of shear stress in the flange of the flat box section should not be ignored. The effects of the web and flange thicknesses on µ are analyzed and discussed. Based on these effects, a simplified method for calculating the µ value of complex box sections is presented, and this method is demonstrated to considerably reduce the calculation error and meet engineering needs. [ABSTRACT FROM AUTHOR]

This study presents a simplified numerical modeling approach that estimates the local scour depths around bridge supports based on the bed shear stresses. It is developed using 3D computational fluid dynamics and coding through ANSYS workbench scripting along with C++ language. The proposed model is called SCFDS (Simplified Computational Fluid Dynamics Scour). The model's main idea is to lower the bed bathymetry at the locations affected by flow obstruction until the shear stresses reach stable target values. The developed model is assessed by applying it to a complex pier of a real bridge over the Nile-River, and its scour data is calculated using the Hec-18 empirical equations. The outcomes of the model's assessment show that it can depict the local scour around complex bridge supports. The developed approach is a novel and efficient tool that can help the designers in simulating local scour in the vicinity of flow obstructions. However, more verification studies are necessary to reach a generalized conclusion. [ABSTRACT FROM AUTHOR]

Objective: Neovascularization has been extensively studied because of its significant role in both physiological processes and diseases. The significance of vascular microfluidic platforms lies in its essential role in recreating an in vitro environment capable of supporting cellular and tissue systems through the process of neovascularization. Biomechanical properties in a tissue engineered system use fluid flow and transport properties to recapitulate physiological systems. This enables mimicry of organ systems which can further personalized and regenerative medicine. Thus, fluid hemodynamics can be used to study these flow patterns and create a system that mimics real physiological pathways and processes. The establishment of stable flow pathways encourages endothelial cells (ECs) ECs to undergo neovascularization. Specifically, the shear stress applied in capillary beds generates the increased proliferation and differentiation of ECs to build larger microcirculatory beds. Mathematical Framework: Here, we describe a mathematical model that uses branching patterns and vessel morphology to predict hemodynamic parameters in capillary beds. Results: A retinal capillary bed is used as one‐use case of our model to show how the mathematical framework can be used to determine hemodynamic parameters for any microfluidic system. Conclusion: In doing so, this tool can be altered to be used to supplement emerging research areas in neovascularization. [ABSTRACT FROM AUTHOR]

This study utilizes molecular dynamics simulation to investigate the complex dynamics of entangled semi-flexible polymer melts. The investigation reveals a significant stress overshoot phenomenon in the systems, demonstrating the intricate interplay between shear rates, chain orientation, and chain stretching dynamics. Additionally, the identification of metastable states, characterized by a dual-plateau phenomenon in the shear stress-strain curve at specific Rouse-Weissenberg number WiR, showcases the system's responsiveness to external perturbations and its transition to stable shear banding states. Moreover, the analysis of flow field deviations uncovers a progression of shear bands with increasing WiR, displaying distinct behaviors in the system's dynamics under different shear rates and chain lengths. These findings challenge established theoretical frameworks and advocate for refined modelling approaches in polymer rheology research. [ABSTRACT FROM AUTHOR]

Researching the rheology contributes to enhancing the physical and mechanical properties of concrete and promoting material sustainability. Despite the challenges posed by numerous factors influencing viscosity, leveraging machine learning in the era of big data emerges as a viable solution for predicting the general properties of construction materials. This study aims to create models to forecast the rheological properties of cementitious materials containing fly ash and nanosilica. Four models—Random Forest, XGBoost, ANN, and RNN (Stacked LSTM)—are employed to predict and assess shear rate versus shear stress and shear rate versus apparent viscosity curves. Through hyperparameter adjustments, RNN (Stacked LSTM) exhibits excellent performance, achieving a coefficient of determination (R2) of 0.9582 and 0.9257 for the two curves, demonstrating superior statistical parameters and fitting effects. The RNN (Stacked LSTM) exhibited a better generalization ability, suggesting it will be more reliable for future prediction in cementitious material viscosity. [ABSTRACT FROM AUTHOR]

The periodontal ligament (PDL) is crucial for maintaining the integrity and functionality of tooth-supporting structures. Mechanical forces applied to the tooth during orthodontic tooth movement generate pore pressure gradients, leading to interstitial fluid movement within the PDL. The generated fluid shear stress (FSS) stimulates the remodeling of PDL and alveolar bone. Herein, we present the construction of a parallel fluid-flow apparatus to determine the effect of FSS on PDL cells. The chamber was designed and optimized using computer-aided and computational fluid dynamics software. The chamber was formed by PDMS using a negative molding technique. hPDLCs from two donors were seeded on microscopic slides and exposed to FSS of 6 dyn/cm2 for 1 h. The effect of FSS on gene and protein expression was determined using RT-qPCR and Western blot. FSS upregulated genes responsible for mechanosensing (FOS), tissue formation (RUNX2, VEGFA), and inflammation (PTGS2/COX2, CXCL8/IL8, IL6) in both donors, with donor 2 showing higher gene upregulation. Protein expression of PTGS2/COX2 was higher in donor 2 but not in donor 1. RUNX2 protein was not expressed in either donor after FSS. In summary, FSS is crucial in regulating gene expression linked to PDL remodeling and inflammation, with donor variability potentially affecting outcomes. [ABSTRACT FROM AUTHOR]

This study investigated the performance of recycled waste fishing net sheets (WSs) as a sustainable strengthening material for reinforced concrete (RC) slabs. The primary challenge addressed is the debonding failure caused by the low bond strength at the WS-to-concrete interface. To analyze this, two full-scale RC slabs—one with and one without strengthening—were cast and tested under a four-point bending setup. Finite element (FE) models incorporating existing bond–slip laws were developed using the ABAQUS software to simulate the strengthened slab's behavior. A sensitivity analysis was performed to assess the impact of bond–slip parameters on the failure mechanism. Experimental results indicated that the WS-strengthened slab enhanced the RC slab capacities by 15% in yield load and 13% in initial stiffness. Furthermore, the maximum shear stress of 0.5τmax or interfacial fracture energy of 0.2Gf, compared to values proposed by Monti et al., enabled the simulation of the global response observed in the experiment. [ABSTRACT FROM AUTHOR]

The main aim of this work is to evaluate the mechanical properties of additive manufactured polymeric parts joined with standard plastic parts through structural adhesives. The primary advantage of this technique is its ability to significantly increase the size of the final assembly by using additive manufacturing (AM) for complex joints and inexpensive, reliable extruded plastic parts for load-bearing components. This hybrid assembly combines the flexibility and shape adaptability of AM with the structural strength and cost-effectiveness of extruded polymer parts, resulting in a final design that performs comparably to the base material. The materials used in the paper are rigid acrylic adhesive and toughened acrylic, both applicable with almost no surface preparation and fast curing. The 3D-printed parts are produced in ABS, while the standard parts are in PVC. First, the work is devoted to estimating the performance of the adhesives using pin–collar joints and a combined numerical and experimental methodology. The second section presents and discusses the results of two more realistic applications of adhesive bonding to hybrid complex joints. For the pin–collar joints, the results show failure mostly in the adhesive, with an average shear stress of 11.5 MPa and 5.22 MPa and a stiffness of 4449 N/mm and 3649 N/mm for the rigid and toughened adhesives, respectively. The results of the adhesive bonding of structural joints show that the adhesive is always capable of providing the load-carrying capacity required to achieve the strength of traditionally manufactured polymeric parts. The paper shows that adhesives are a feasible way to expand the potential of 3D-printed equipment to obtain larger hybrid parts partially realized with traditional technology, especially with inexpensive off-the-shelf bars and sections. [ABSTRACT FROM AUTHOR]

Compounding is an important step in processing base polymers and is used to incorporate various additives into a polymer. For this purpose, different screw elements are used for dispersive and distributive mixing on a co-rotating twin-screw extruder. Optimising the screw configuration requires precise knowledge of the screw elements' mixing properties, which have not been thoroughly investigated. This study analyses the mixing behaviour of individual screw elements regarding dispersive and distributive mixing using 3D CFD flow simulations with subsequent particle tracking. For distributive mixing, the particle distribution behind the screw elements in the XY plane is analysed and the mixing index MQ, which relates the standard deviation and the mean value of the triangular areas between the particles, is calculated. For dispersive mixing, the maximum shear stress on the particle path and the integral of the shear stress over the residence time of each individual particle are determined. The results show that screw element geometry and rotation speed have a significant influence on dispersive and distributive mixing. In addition, better dispersive mixing is achievable with highly viscous materials. These findings enable the optimisation of the mixing zone of a co-rotating twin-screw extruder for the efficient mixing of mineral fillers. [ABSTRACT FROM AUTHOR]

In reality, the remaining oil in the ultra-high water cut period is highly dispersed, so a thorough investigation is required to understand the microscopic remaining oil. This will directly influence the technological direction and allow for countermeasures such as enhanced oil recovery (EOR). Therefore, this study aims to investigate the state, classification method and utilization mechanism of the microscopic remaining oil in the late period of the ultra-high water cut. To achieve this, the classification of microscopic remaining oil based on mechanical mechanism was developed using displacement CT scan and micro-scale flow simulation methods. Three carefully selected mechanical characterization parameters were used: oil–water connectivity, oil–mass specific surface and oil–water area ratio. These give five types of microscopic remaining oil, which are as follows: A (capillary and viscous oil cluster type), B (capillary and viscous oil drop type), C (viscous oil film type), D (capillary force control throat type), and E (viscous control blind end type). The state of the microscopic remaining oil in classified oil reservoirs was defined after high-expansion water erosion. Based on micro-flow simulation and analysis of different forces during the displacement process, the main microscopic remaining oil recognized is in class-I, class-II and class-III reservoirs. Within the Eastern sandstone oilfields in China, the ultra-high water-cut stage is a good indicator that the class-I oil layer is dominated by capillary and viscous oil drop types distributed in large connected holes. The class-II oil layer has capillary and viscous force-controlled clusters distributed in small and medium pores with high connectivity. In the case of the class-III oil layer, it enjoys the support of capillary force control throats that are mainly distributed in small holes with high connectivity. Integrating mechanisms of different types of micro-remaining oil indicates that, enhancing utilization conditions requires increasing pressure gradient and shear force while reducing capillary resistance. An effective way to improve the remaining oil utilization is to increase the pressure gradient and change the flow direction during the water-drive development process. Hence, this forms a theoretical basis and a guide for the potential exploitation of remaining oil. Likewise, it provides a strategy for optimizing enhanced oil recovery in the ultra-high water-cut stage of mid-high permeability oil reservoirs worldwide. [ABSTRACT FROM AUTHOR]

Understanding the aerodynamic performance of scaled-down models is vital for providing crucial insights into wind energy optimization. In this study, the aerodynamic performance of a scaled-down model (12%) was investigated. This validates the findings of the unsteady aerodynamic experiment (UAE) test sequence H. UAE tests provide information on the configuration and conditions of wind tunnel testing to measure the pressure coefficient distribution on the blade surface and the aerodynamic performance of the wind turbine. The computational simulations used shear stress transport and kinetic energy (SST K-Omega) and transitional shear stress transport (SST) turbulence models, with wind speeds ranging from 5 m/s to 25 m/s for the National Renewable Energy Laboratory (NREL) Phase VI and 4 m/s to 14 m/s for the 12% scaled-down model. The aerodynamic performance of both cases was assessed at representative wind speeds of 7 m/s for low, 10 m/s for medium, and 20 m/s for high flow speeds for NREL Phase VI and 7 m/s for low, 9 m/s medium, and 12 m/s for the scaled-down model. The results of the SST K-Omega and transitional SST models were aligned with experimental test measurement data at low wind speeds. However, the SST K-Omega torque values exhibited a slight deviation. The transitional SST and SST K-Omega models yielded aerodynamic properties that were comparable to those of the 12% scaled-down model. The torque values obtained from the simulation for the full-scale NREL Phase VI and the scaled-down model were 1686.5 Nm and 0.8349 Nm, respectively. Both turbulence models reliably predicted torque and pressure coefficient values that were consistent with the experimental data, considering specific flow regimes. The pressure coefficient was maximum at the leading edge of the wind turbine blade on the windward side and minimum on the leeward side. For the 12% scaled-down model, the flow simulation results bordering the low-pressure region of the blade varied slightly. [ABSTRACT FROM AUTHOR]

Nuclear power plants, where steel-plate concrete (SC) structures are commonly adopted, require large-scale components to withstand significant loads, such as those caused by sudden explosions. As a result, SC modular members used in nuclear power plants must have thicker walls filled with concrete compared to standard-sized ones. These large walls also require additional components, such as tie bars and H-shaped steel sections, to reinforce adhesion and resist shear stresses. This study focuses on tie bars placed adjacent to studs and evaluates their influence on the tensile strength of wall structures. To investigate this, we conducted experimental tests using full-scale specimens, including various combinations ranging from single stud to combined stud-tie configurations. Based on the results of these performance tests, we propose a design recommendation for estimating the tensile capacity of SC structures, considering the influence of tie bars. [ABSTRACT FROM AUTHOR]

Dilatancy is commonly defined as the ratio of the rates of plastic volumetric strain to plastic deviatoric strain, denoted as Dp. Owing to the high modulus of elasticity, the elastic volumetric and deviatoric strain rates under shear stress in conventional cohesionless materials are negligible. Therefore, using the ratio of the rates of total volumetric to deviatoric strain (Dt) as an approximation is common in studying stress–dilatancy behavior and calibrating dilatancy model parameters. This approach is also common in the study of rubber-added cohesionless materials (RCM). However, RCM with a common range of rubber content exhibit a significantly lower modulus of elasticity compared to conventional cohesionless materials. Further research is needed to evaluate the potential impact of elastic strain rates in RCM on stress–dilatancy analysis. Therefore, comparisons were conducted on the stress–dilatancy responses of a series of tests on RCM, where dilatancy is calculated by Dp and Dt, respectively. Furthermore, a modified method for calibrating the parameters of a state-dependent dilatancy model considering Dp is presented. It turns out that Dp is better suited and more precise for dilatancy analysis on highly elastic RCM. Additionally, the dilatancy model can more precisely capture the test results of RCM with parameters calibrated by the proposed method. [ABSTRACT FROM AUTHOR]