Search Results (505)

Porous media have great application prospects, such as transpiration cooling for the aerospace industry. The main challenge for the prediction of gas permeability includes the geometrical complexity and high Knudsen number of gas flow at the nano-scale to micro-scale, leading to failure of the conventional Darcy’s law. To address these issues, the Quartet Structure Generation Set (QSGS) method is improved to construct anisotropic and heterogeneous three-dimensional porous media, and the lattice Boltzmann method (LBM) with the multiple relaxation time (MRT) collision operator is adopted. Using MRT-LBM, the pressure boundary conditions at the inlet and outlet are firstly dealt with using the moment-based boundary conditions, demonstrating good agreement with the analytical solutions in two benchmark tests of three-dimensional Poiseuille flow and flow through a body-centered cubic array of spheres. Combined with the Bosanquet-type effective viscosity model and Maxwellian diffuse reflection boundary condition, the gas flow at high Knudsen (Kn) numbers in three-dimensional porous media is simulated to study the relationship between pore-scale anisotropy, heterogeneity and Kn, and permeability and micro-scale slip effects in porous media. The slip factor is positively correlated with the anisotropic factor, which means that the high Kn effect is stronger in anisotropic structures. There is no obvious correlation between the slip factor and heterogeneity factor. Full article

The 6 February 2023 M_W 7.8 and M_W 7.6 earthquakes in southeastern Türkiye ruptured more than 400 km of the East Anatolian Fault Zone (EAFZ), producing one of the most destructive seismic sequences in recent history. Here, we integrate InSAR data, a new GNSS velocity field, and small-magnitude earthquakes to investigate the coseismic deformation, rupture geometry, and interseismic strain accumulation along the EAFZ. Using elastic dislocation modeling with a variable-strike, multi-segment fault geometry, we constrain the slip distribution of the mainshocks, showing improved fits to the surface displacement compared to the planar fault model. The M_W 7.8 event ruptured a number of fault segments over ~300 km, while the M_W 7.6 event activated a more localized fault system with a peak slip exceeding 15 m. We also model two moderate events (M_W 5.6 in 2020 and M_W 5.3 in 2022) along the southwestern part of the Pütürge segment—an area not ruptured during the 2020 or 2023 sequences. GNSS-derived strain-rate and locking depth estimates reveal strong interseismic coupling and significant strain accumulation in this region, suggesting the potential for a future large earthquake (M_W 6.6–7.1). Similarly, the Hatay region, at the southwestern termination of the 2023 rupture, shows a persistent strain accumulation and complex fault interactions involving the Dead Sea Fault and the Cyprus Arc. Our results demonstrate the importance of combining remote sensing and geodetic data to constrain fault kinematics, evaluate rupture segmentation, and assess the seismic hazard in tectonically active regions. Targeted monitoring at rupture terminations—such as the Pütürge and Hatay sectors—may be crucial for anticipating future large-magnitude earthquakes. Full article

The propulsion system is a critical component of medium–low-speed maglev trains and the single-sided linear induction motor (SLIM) has been adopted to generate thrust. However, the SLIM operates periodically in maglev trains. The temperature of the secondary plate of the SLIM rises significantly due to eddy currents when the train enters and leaves the station, where large slip occurs. Subsequently, the temperature decreases through natural cooling during the shift interval time. This periodic operating condition is rarely addressed in the existing literature and warrants attention, as the temperature accumulates over successive periods, potentially resulting in thermal damage and thrust variation. Furthermore, the conductivity of plate varies significantly in the process, which affects the losses and thrust, requiring a coupled analysis. To investigate the temperature variation patterns, this paper proposes a coupled model integrating the lumped parameter thermal network (LPTN) and the equivalent circuit (EC) of the SLIM. Given the unique structure of the F-shaped rail, the LPTN mesh is well designed to account for the skin effect. Three experiments and a finite element method (FEM)-based analysis were conducted to validate the proposed model. Finally, optimizations were performed with respect to different shift interval time, plate materials, and carriage numbers. The impact of temperature on thrust is also discussed. The results indicate that the minimum shift interval time and maximum carriage number are 70.7 s and 9, respectively, with thrust increasing by 22.0% and 22.0%. Furthermore, the use of copper as the plate material can reduce the maximum temperature by 22.01% while decreasing propulsion thrust by 26.1%. Full article

Electron backscatter diffraction and scanning electron microscopy were performed herein to in situ investigate the influence of texture on the anisotropic deformation mechanism of TC11 forged components. The in situ tensile specimen was cut from the TC11 ring forging, and the tensile force–displacement curve was recorded while the slip lines in the specimen surface detected was traced during the in situ tensile test. The tensile results show that the yield and ultimate tensile strengths decreased in the order of transverse-direction (TD) > rolling-direction (RD) > normal-direction (ND) samples. The anisotropy of the tensile strength was related to the differences in the activated slip systems of the ND, TD, and RD samples. The slip lines results show that in the yielding stage, the ND, TD, and RD samples were dominated by Prismatic <a>, Pyramidal <c + a>, and Pyramidal <a> slips, respectively. In order to further analyze the relationship between the slip system and the yield strength, an anisotropy coefficient was determined to evaluate the differences in resistances for different activated slip systems, providing a good explanation of the variations in the tensile strength anisotropy. The ratios of the critical resolved shear stress (CRSS) of the basal, Prismatic <a>, primary Pyramidal <c + a>, and secondary Pyramidal <c + a> slip systems in the α phase were estimated to be 0.93:1:1.18:1.05 based on the type, number, orientation of slip activations, and Schmid factor. Moreover, the Prismatic <a> slips primarily occurred in the axial and radial (ND and RD) samples with [0001] and [$\stackrel{\mathrm{-}}{1}2\stackrel{\mathrm{-}}{1}2$] textures, whereas the Pyramidal <c + a> slip system was dominant in the TD samples with [11$\stackrel{\mathrm{-}}{2}2$] and [10$\stackrel{\mathrm{-}}{1}$2] textures. Overall, this research demonstrates that the activation of the α-phase slip depends on the grain orientation, SF, and the CRSS, promoting strong strength anisotropy. Full article

The ultra-thin Invar alloy strips are widely used in the manufacture of the fine masks; cold rolling of such thin strips (<100 μm) poses significant difficulties, primarily due to the limited number of grains within the thickness range. Consequently, it is important to understand the grain structure and property evolutions of the ultra-thin Invar alloy strips during cold rolling. In this study, an annealed Invar36 alloy strip, 100 µm thick, was cold rolled to different thicknesses, and the surface deformation morphologies, cross-sectional grain structure, intracrystalline microstructure and tensile properties of these thin strips were characterized and analyzed. The results show that plastic deformation of the initial annealed equiaxed grains is not uniform, depending on the grain orientation, resulting in different slip bands morphologies, unevenness and increase in roughness. Meanwhile, the grain rotation and rolling texture develop with increasing cold rolling reduction. The dislocation density in the 60% cold-rolled strip is about decuple that of the original annealed strip, and high-density tangled dislocations are formed, making the tensile strength increase from 430 MPa to 738 MPa. Grain refining and proper intermediate annealing are proposed to optimize the thickness uniformity, evenness and surface roughness. Full article

To elucidate the mechanism underlying the changes in the bonding performance of reinforced reef limestone concrete under dry–wet carbonation cycles, and to establish a foundation for its durability analysis and design, experiments were conducted with varying dry–wet carbonation cycles (0, 20, 40, 60, and 80 cycles) and loading rates (0.01 mm/min, 0.1 mm/min, 1 mm/min, 2 mm/min, and 5 mm/min) through pull-out tests. The results demonstrate that as the number of dry–wet carbonation cycles increases, the damage to reinforced reef limestone concrete intensifies progressively, reaching a mass loss rate of 3.05% by the end of the cycles, while the ultrasonic wave velocity decreases by 17.4%. The effects of different loading rates and cycle counts on reinforced reef limestone concrete are primarily observed through alterations in peak bond stress. Utilizing the experimental data, this study established an equation to analyze the influence of dry–wet carbonation cycles and loading rates on the bond strength and slip behavior between steel bars and reef limestone concrete. This equation offers a theoretical framework for the durability analysis and design of reinforced reef limestone concrete. Full article

To investigate the influence of repeated loading on the bond behavior between steel bars and reactive powder concrete (RPC), this study conducted repeated loading tests on eight beam specimens and one static loading test as a control. The effects of stress levels and the number of repeated loading cycles on the bond behavior between steel bars and RPC were examined. The results indicate that the static failure mode was characterized by steel bar pull-out accompanied by significant plastic deformation, with no propagation of cracks in the RPC after their initiation, demonstrating the excellent crack control capability of RPC. After 10,000 cycles of repeated loading at a high stress level (Z = 0.9), the ultimate bond strength decreased by only 3.68%, indicating the superior fatigue resistance of the steel–RPC interface. Based on the analysis of slip accumulation effects, a constitutive model considering stress levels and the number of repeated loading cycles was established. This model can serve as a basis for the design of steel anchorage in RPC structures subjected to cyclic loading. Full article

Considering stick–slip vibration and the impact loads formed while drilling in strongly heterogeneous formations or soft–hard interbedded formations, an adaptive matching drilling load method is presented in this paper to form dynamic drilling loads to automatically adjust the applied axial load acting on the drill bit. To determine the rock-breaking mechanisms using this method, the structure of a kind of downhole tool was designed and a discrete element simulation model was established with a PDC cutter cutting heterogeneous rock. The effects of the load factor, the applied initial axial force, and the driven force on the variation in the axial force, as well as the moving displacement of the PDC cutter and the rock-breaking characteristic parameters, were studied. The failure states of the simulated rock have a positive correlation with the number of total cracks generated in the rock-breaking process, as opposed to MSE. The decrease in the reaction force suffered by the PDC cutter in the cutting direction was caused by the automatically adapting load, although there was no significant regularity in the axial direction. MSE decreased obviously under the action of the adaptive matching drilling load method so that the contacting states of the PDC cutter could be improved, thus raising the rate of penetration of the PDC bit. This study provides a feasible method for rapidly drilling in highly heterogeneous formations or soft–hard interbedded formations. Full article

This research investigates the impact of second-order slip conditions, Stefan flow, and convective boundary constraints on the stagnation-point flow of couple stress nanofluids over a solid sphere. The nanofluid density is expressed as a nonlinear function of temperature, while the diffusion-thermo effect, chemical reaction, and thermal radiation are incorporated through linear models. The governing equations are transformed using appropriate non-similar transformations and solved numerically via the finite difference method (FDM). Key physical parameters, including the heat transfer rate, are analyzed in relation to the Dufour number, velocity, and slip parameters using an artificial neural network (ANN) framework. Furthermore, response surface methodology (RSM) is employed to optimize skin friction, heat transfer, and mass transfer by considering the influence of radiation, thermal slip, and chemical reaction rate. Results indicate that velocity slip enhances flow behavior while reducing temperature and concentration distributions. Additionally, an increase in the Dufour number leads to higher temperature profiles, ultimately lowering the overall heat transfer rate. The ANN-based predictive model exhibits high accuracy with minimal errors, offering a robust tool for analyzing and optimizing the thermal and transport characteristics of couple stress nanofluids. Full article

Through hydraulic control principles, numerical simulation and indoor testing, the opening principle of a toe-end sliding sleeve with a time delay mechanism is explained. Conventional toe-end sliding sleeve in shale oil wells have problems with premature opening and a failure to open, which means they cannot ensure the whole-well pressure test process and can cause serious economic losses to the oil and gas industry. In order to solve the above problems, a new type of optimal design for toe-end sliding sleeve with a 30 min delayed opening is proposed. In this paper, based on the principle of hydraulic flow, ABAQUS 2022 numerical simulation software was used to study the influence of different states and the same hydraulic pressure on its internal stress–strain value. A qualitative study of the delayed-opening function was carried out using a pressurized pump unit. In addition, principle tests under different operating parameters were designed to quantitatively analyze the pin shear situation and the delayed opening time of the toe-end sliding sleeve when the tool was fitted with different numbers of pins and when the delay valve was fitted. In addition, the simulation results of the hydraulic fluid’s flow inside the time delay mechanism with different nozzle diameters were compared with the theoretical values, which showed that the hydraulic fluid’s flow rate inside the mechanism increased with the enlargement of the nozzle diameter, and the optimal nozzle diameter was 0.56 mm. The indoor test showed that when the tool was retrofitted with a time delay mechanism, installing six pins was the optimal combination. The field application of the slip-on was able to satisfy an opening time delay of 28.3 with a relative error of only 5.67%. These results complement the research on toe-end sliding sleeve and provide ideas for the optimization of toe-end slipcovers incorporating a time delay mechanism. Full article

Recent research indicates that high-strength bolts could be more effectively and efficiently used to connect steel girders and fabricated decks or retrofit existing composite girders than headed studs. To reduce the number of bolt shear connectors and, thus, further accelerate the construction of composite girders, high-strength large bolts could be an excellent alternative, resulting in greater concrete stress below the bolt. Also, hybrid fiber-reinforced concrete (HFRC) has better tensile ductility and strength than that of ordinary concrete (OC). Therefore, this study tried to design eighteen push-out test specimens, including different configurations of bolt shear connectors, to investigate the static properties of post-installed, high-strength, large-bolt shear connectors with fabricated HFRC/OC slabs. The experimental results indicated that the capacity and initial stiffness of a high-strength large through-bolt shear connector was the smallest. The fiber might enhance the capacity and initial stiffness of bolt shear connectors. Increasing the bolt diameter can significantly enhance the initial stiffness and load-bearing capacity, while the clearance of the bolt hole had a great influence on the capacity, initial stiffness, and slippage of the post-installed high-strength large-bolt shear connector. Finally, the capacity equation and slip behavior of post-installed, high-strength, large-bolt shear connector with fabricated HFRC deck were obtained using the regression method, which could provide the reference for their design. Full article

This study explored the relationship between the Nusselt number and the friction factor in the laminar boundary slip flow of a Newtonian liquid between parallel plates. In addition, simplified equations were developed to estimate two key parameters—slip velocity and temperature jump—both of which are typically difficult to measure in experimental settings. The primary objectives of investigating the relationship between the Nusselt number and the friction factor were twofold: (1) to uncover the previously unknown mathematical connection (or analogy) between momentum transfer and heat transfer in the presence of boundary slip and (2) to enable predictions of either the pressure drop or the heat transfer coefficient by measuring just one of these quantities, thus simplifying experimental procedures. Considering the difficulty of conducting experiments of this type of flow (as described in the published literature), a finite element-based numerical model built in COMSOL Multiphysics software was used to validate the theoretically developed relationship over a wide range of Reynolds numbers and boundary slip values. While surface modifications like dimples, bumps, and ribs typically modify both the Nusselt number and pressure drop, leading to their increase for a given fluid and constant inlet Reynolds number, their behavior changes when boundary slip is present, particularly in cases where there is a low temperature jump at the wall. The analysis identified a specific threshold for the dimensionless temperature jump below which the Nusselt number with boundary slip will exceed 8.235. Furthermore, the analysis showed that for the Nusselt number to rise above 8.235, the non-dimensional velocity slip must be at least 3.19 times larger than the non-dimensional temperature jump. This means that the velocity slip has to be significantly larger than the temperature jump to achieve enhanced heat transfer in boundary slip flows. Full article

In this study, the evolution process of a landslide model under continuous rainfall conditions with a rainfall intensity of 30 mm/h is studied in depth based on an outdoor rainfall model test of a colluvial slope as the research material. The response law of pore water pressure and settlement amount is also obtained, and the influence of bedrock inclination angle on the development and deformation failure of the colluvial landslide is discussed. When the dip angle of the bedrock is 40°, it is prone to sudden slip-type landslides, and the evolution process is as follows: tensile cracks appear at the trailing edge, and these cracks continue to increase, leading to overall sliding. When the bedrock dip angle is 30°, traction landslides are prone to occur, and the evolution process is as follows: there is sliding at the foot of the slope, tensile cracks appear in the middle, sliding occurs in the middle, and tensile cracks appear in the upper part, leading to overall sliding. Before the landslide starts, the pore water pressure rises significantly. In the process of landslide evolution, the fine particles move to the foot of the slope with the rainwater, and the larger the angle of the slope, the greater the number of fine particles that accumulate at the foot of the slope, and the higher the elevation and the larger the scale of the trailing edge of the sliding body during sliding. Full article

The movement of a wheeled vehicle is a non-regular dynamic process characterized by a large number of states that depend on the movement conditions. This movement involves a large number of situations where elastic tires skid and slip against the base surface. This reduces the efficiency of movement as useful mechanical energy of the electromechanical drive is spent to overcome the increased skidding and slipping. Complete sliding results in the loss of control over the vehicle, which is unsafe. Processes that take place immediately before such phenomena are of special interest as their parameters can be useful in diagnostics and control. Additionally, such situations involve adverse oscillatory processes that cause additional dynamic mechanical and electrical loading in the electromechanical drive that can result in its failure. The authors provide the results of laboratory road research into the emergence of self-oscillatory phenomena during the rolling of a wheel with increased skidding on the base surface and a low traction factor. This paper reviews the methods of designing an anti-slip control system for wheels with an oscillation damping function and studies the applicability and efficiency of the suggested method using mathematical simulation of the virtual vehicle operation in the Matlab Simulink software package. Using the self-oscillation suppression algorithm in the control system helps reduce the maximum amplitude values by 5 times and average amplitudes by 2.5 times while preventing the moment operator from changing. The maximum values of current oscillation amplitude during algorithm changes were reduced by 2.5 times, while the current change rate was reduced by 3 times. The reduction in the current-change amplitude and rate proves the efficiency of the self-oscillation suppression algorithm. The high change rate of the current consumed by the drive’s inverters may have a negative impact on the remaining operating life of the rechargeable electric power storage system. This impact increases with the proximity of its location due to the low inductance of the connecting lines and the operating parameters, and the useful life of the components of the autonomous voltage inverters. Full article

The Indonesian government is currently focusing on infrastructure development, including military infrastructure to strengthen national defense. One of these projects is the development of the Indonesian Army Central Hospital, which is being continually expanded with facilities such as proton beam therapy. Due to its underground construction, special attention must be given to construction safety to prevent workplace accidents. This study focuses on assessing construction safety risks at the military hospital using activity-based failure modes and effects analysis (FMEA). The research methodology employed is a mixed-method approach involving 5 construction safety experts and 100 respondents directly involved in underground structure construction. Descriptive data analysis was conducted, serving as the basis for calculating risk priority numbers (RPN) using the FMEA method. Three main activities were identified with very high risks ranked from 1 to 10: lifting of contiguous pile casing, basement excavation, and installation of cast in situ bored pile gutter. These activities entail safety risks with RPN values ranging from 100 to 125, including worker’s hands being caught in tools/materials, being struck by tools/materials, falling/slipping into excavations, and being buried/struck by excavated soil. This research has positive implications as a reference for developing construction safety plans that include risk identification, risk assessment, and determination of control measures. Full article