Search Results (1,721)

This study analyzes the impact of slip-dependent zeta potential on the heat transfer characteristics of nanofluids in cylindrical microchannels with consideration of thermal radiation effects. An analytical model is developed, accounting for the coupling between surface potential and interfacial slip. The linearized Poisson–Boltzmann equation, along with the momentum and energy conservation equations, is solved analytically to obtain the electrical potential field, velocity field, temperature distribution, and Nusselt number for both slip-dependent (SD) and slip-independent (SI) zeta potentials. Subsequently, the effects of key parameters, including electric double-layer (EDL) thickness, slip length, nanoparticle volume fraction, thermal radiation parameters, and Brinkman number, on the velocity field, temperature field, and Nusselt number are discussed. The results show that the velocity is consistently higher for the SD zeta potential compared to the SI zeta potential. Meanwhile, the temperature for the SD case is higher than that for the SI case at lower Brinkman numbers, particularly for a thinner EDL. However, an inverse trend is observed at higher Brinkman numbers. Similar trends are observed for the Nusselt number under both SD and SI zeta potential conditions at different Brinkman numbers. Furthermore, for a thinner EDL, the differences in flow velocity, temperature, and Nusselt number between the SD and SI conditions are more pronounced. Full article

Traditional static analysis cannot effectively explain the issue of the sealing performance of the premium connection being decreased due to the vibration of the tubing, leading to the failure of the connection sealing. In this paper, based on the energy dissipation theory and considering the influence of the micro contact slip of the sealing surface under the vibration of the tubing, a finite element model of the premium connection is established. The natural frequency and vibration mode are obtained through modal analysis experiments, and the accuracy of the finite element model is verified. The results show that the first five natural frequencies are mainly concentrated in the axial direction of the tubing, with the amplitude of the radial vibration mode being small. The vibration mode results are applied to the model as boundary conditions. It is found that an increase in the axial displacement amplitude leads to an increase in the energy dissipation of the sealing surface of the premium connection, which reduces the normal contact pressure and the effective length of the sealing surface, ultimately leading to a decrease in the sealing performance. Full article

Composite adsorbents based on a natural biopolymer matrix of chitosan, to which 4-amino-N′-hydroxy-1,2,5-oxadiazole-3-carboximidamide and its Se derivative were attached, were synthesized. A complex of physicochemical analysis methods indicates that the direct introduction of a matrix with high ionic permeability into the reaction mixture contributes to the formation of homogeneous particles of composite with developed surface morphology, which enhances the kinetic and capacitive parameters of uranium sorption in liquid media. It has been established that the direct introduction of a matrix with high ionic permeability into the reaction mixture contributes to the formation of homogeneous particles with a developed surface morphology, which enhances the kinetic and capacitive parameters of uranium sorption in liquid media. The synthesized materials had increased sorption-selective properties towards uranium in the pH range from 4 to 9 under static sorption conditions. The formation of the Se derivative of amidoxime during its attachment to the polymer matrix (Se-chit) contributes to the creation of a more chemically stable and highly effective adsorbent, compared to the direct binding of 4-amino-N′-hydroxy-1,2,5-oxadiazole-3-carboximidamide with chitosan (43AF-chit). The optimal parameters for the synthesis of materials were established. It was demonstrated that the ratio of amidoxime to chitosan should be within the range of 2:1 to 1:2. As the mass content of chitosan increases, the material gradually dissolves and transforms into a gel, resulting in the formation of liquid radioactive waste with a complex chemical composition. It was found that the kinetic sorption parameters of composite materials increase 2–10 times compared to those of non-composite materials. The sorption capacity of uranium in solutions with pH 6 and pH 8 can reach approximately 400–450 mg g⁻¹. Under dynamic sorption conditions, the effective filtration cycle values (before uranium slips into the filtrate ≥ 50%) improve significantly when transitioning from a non-composite adsorbent to a composite one: increasing from 50 to 800 b.v. for pH 6 and from 2700 to 4000 b.v. for pH 8. These results indicate that the synthesized sorbents are promising materials for uranium removal from liquid media, suitable for both purification and the recovery of radionuclides as valuable raw materials. Full article

Background: Femoral neck fractures are rare but serious injuries in children and adolescents, often resulting from high-energy trauma and prone to complications like avascular necrosis (AVN) and nonunion. Even rarer is the development of slipped capital femoral epiphysis (SCFE) following femoral neck fracture, which presents unique diagnostic and treatment challenges. SCFE can destabilize the femoral head, with severe cases requiring complex surgical interventions. Case presentation: This report details a case of a 15-year-old male with autism spectrum disorder (ASD) who developed severe SCFE one month after treatment for a Delbet type III femoral neck fracture. The condition was managed with an Imhäuser intertrochanteric osteotomy (ITO), in situ fixation (ISF), and osteochondroplasty (OChP), supported by virtual surgical planning (VSP) and 3D-printed patient-specific instruments (PSIs) for precise correction and fixation. Discussion: The surgery was completed without complications. Six months after the operation, the patient exhibited a pain-free, mobile hip with radiographic evidence of fracture healing and no signs of AVN. Functional outcomes were favorable despite rehabilitation challenges due to ASD. Conclusions: The Imhäuser ITO, combined with ISF and OChP, effectively addressed severe SCFE after femoral neck fracture, minimizing AVN risk. VSP and PSIs enhanced surgical accuracy and efficiency, demonstrating their value in treating rare and complex pediatric orthopedic conditions. Full article

It is very easy for a small lunar rover to slip on the regolith of the lunar surface and become stuck. Previous studies have quantitatively evaluated the effects of wheel geometry, such as elliptical or eccentric wheels, on the performance of a rover when climbing up slopes. These studies reported that the rovers were able to run on a 30-degree slope made of silica sand. In this study, a small rover was designed and created, and running tests were conducted using lunar soil simulant and silica sand to predict its performance on the lunar surface. The effects of soil differences on the performance of the rover were clarified through the running tests and the measurement of reaction force on the lug. Although the rover exhibited a greater slip ratio on the lunar soil simulant than on the silica sand, the rover with eccentric wheels was able to climb up to a 30-degree angle on the lunar soil simulant. The results for the sinkage measurement of the rover showed that the eccentric wheels prevented sinkage with their up-and-down motion, enabling the rover to climb steep slopes. Furthermore, the tests for measuring the reaction force on the lug indicated that the density change in the lunar soil simulant did not provide sufficient reaction force, and that the running performance on the lunar soil simulant was lower than that on the silica sand. Full article

Magnetic hydrogel soft robots have shown great potential in various fields. However, their contact dynamic behaviors are complex, considering stick–slip motion at the contact interface, and lack accurate computational models to analyze them. This paper improves the numerical computational method for hydrogel materials with magneto-mechanical coupling effect, analyses the inchworm-like contact motion of the biomimetic bipedal magnetic hydrogel soft robot, and designs and optimizes the robot’s structure. In the constitutive model, a correction factor representing the influence of the direction of magnetic flux density on the domain density has been introduced. The magnetic part of the Helmholtz free energy has been redefined as the magnetic potential energy, which can be used to explain the phenomenon that the material will still deform when the magnetic flux density is parallel to the external magnetic field. The accuracy of the simulation is verified by comparing numerical solutions with experimental results for a magnetic hydrogel cantilever beam. Furthermore, employing the present methods, the locomotion of a magnetic hydrogel soft robot modeled after the inchworm’s gait is simulated, and the influence of the coefficient of friction on its movement is discussed. The numerical results clearly display the control effect of the external magnetic field on the robot’s motion. Full article

This paper investigates the tensile and low-cycle fatigue characteristics of S32750 duplex stainless steel subjected to two distinct solid solution treatment temperatures. The microstructures, fracture surfaces, and slip systems of the tested steel were analyzed using optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. The findings reveal that elevating the solid solution treatment temperature from 1080 °C to 1180 °C results in an increase in the yield strength of the tested steel by approximately 36 MPa and a substantial enhancement in fatigue life by 34%. Microhardness measurements indicate that the degree of hardening in austenite post-fatigue failure significantly surpasses that of ferrite. The variation in solid solution temperature alters the ferrite and austenite content within the matrix, consequently affecting the strain distribution between the two phases. The high-temperature solid solution treatment effectively enhances the two-phase strain-bearing capacity of the tested steel. Following the 1180 °C solid solution treatment, no cloud-like dislocation patterns were observed in the ferrite; instead, they were replaced by a proliferation of thick, interwoven dislocation bundles. In contrast, the dislocations within the austenite predominantly consist of ordered planar slip and twinning. The primary contributor to the extended fatigue life is the increased number of absorbed dislocations within the ferrite grains. Full article

Accurately and quickly estimating the peak pavement adhesion coefficient is crucial for achieving high-quality driving and for optimizing vehicle stability control strategies. However, it also helps with putting forward higher requirements for vehicle driving states, tire model construction, the speed of the convergence, and the precision of the estimation algorithm. This paper unequivocally presents two highly effective methods for accurately estimating the peak pavement adhesion coefficient. Firstly, a new dimensionless tire model is constructed. A relationship between the mechanical tire characteristics and peak adhesion coefficient is established by using the Burckhardt model’s analogy between the adhesion coefficient and peak adhesion coefficient, and the UKE algorithm completes the estimation. Secondly, an adaptive variable universe fuzzy algorithm (AVUFS) is established using the follow-up of the adhesion coefficient between the tire and the road surface. Even if the slip rate is less than 5%, the algorithm can still complete accurate estimations and does not depend on the initial given information. Finally, using the estimation advantages of the two algorithms, fusion optimization is performed, and the best estimation result is obtained. Based on the simulation results, the algorithm can quickly and precisely predict the maximum pavement adhesion coefficient in situations where the pavement has a low or high adhesion coefficient. Full article

Background: Prostheses are becoming more advanced and biomimetic with time, providing additional capabilities to their users. However, prosthetic sensation lags far behind its natural limb counterpart, limiting the use of sensory feedback in prosthetic motion planning and execution. Without actionable sensation, prostheses may never meet the functional requirements to match biological performance. Methods: We propose an approach for upper limb prosthetic grasp security feedback, delivered to the wearer through direct nerve stimulation proportional to the likelihood of objects slipping from grasp. This proportional feedback is based on a linear regression of the sensors embedded in a prosthetic hand to predict slip before it occurs. Four participants with transhumeral amputation performed pulling tasks with their prosthetic hand grasping an object at predetermined grip forces, attempting to pull the object with as much force as possible without slip. These trials were performed with two different prediction notification paradigms. Results: At lower grasp forces, where slip was more likely, a strong, single impulse notification of impending slip reduced the incidence of object slip by a median of 32%, but the maximum achieved pull forces did not change. At higher grasp forces, where slip was less likely, the maximum achieved pull forces increased by a median of 19% across participants when provided with a stimulation strength inversely proportional to the grasp security, but slip incidence was unchanged. Conclusions: These results suggest that this approach may be effective in recreating a lost sense of grip stability in the missing limb that can be incorporated into motor planning and ultimately prevent unanticipated object slips. Full article

This study aims to explore the effect of microstructural parameters on the notch fatigue damage behavior of the TC21 alloy. Different levels of lamellar microstructures were achieved through distinct aging temperatures of 550 °C, 600 °C, and 650 °C. The findings reveal that increasing aging temperature primarily contributes to the augmentation of α colony (α_c) thickness, grain boundaries α phase (GBα) thickness, and α fine (α_fine) size alongside a reduction in α lath (α_lath) thickness and α_fine content. The notch alters stress distribution and relaxation effects at the root, enhancing notched tensile strength while weakening plasticity. Moreover, the increased thickness of GBα emerges as a critical factor leading to the increase area of intergranular cleavage fracture. It is noteworthy that more thickness α_lath and smaller α_fine facilitate deformation coordination and enhance dislocation accumulation at the interface, leading to a higher propensity for micro-voids and micro-cracks to propagate along the interface. Conversely, at elevated aging temperatures, thinner α_lath and larger α_fine are more susceptible to fracture, resulting in the liberation of dislocations at the interface. The reduction in α_lath thickness is crucial for triggering the initiation of multi-system dislocations at the interface, which promotes the development of persistent slip bands (PSBs) and dislocation nets within α_lath. This phenomenon induces inhomogeneous plastic deformation and localized hardening, fostering the formation of micro-voids and micro-cracks. Full article

Damage mechanisms are a key factor in materials science and are essential for understanding and predicting the behavior of materials under complex loading conditions. In this paper, the influence of different directions, different rates and different model parameters on the mechanical behavior of AZ31 magnesium alloy during the tensile process is investigated based on the secondary development of the VUMAT user subroutine based on the GTN damage model and verified by the tensile experiments at different loading rates and in different directions. The results show that AZ31 magnesium alloy exhibits significant differences in mechanical properties in radial and axial stretching, where the yield strength is lower in the radial direction than in the axial direction, and the elongation is the opposite. Moreover, the maximum stress and elongation of the material decreased with the increasing tensile rate, revealing the importance of the loading rate on the material properties. Compared with the existing studies, this paper determines the GTN model parameters of the AZ31 magnesium alloy extruded state bar by theresponse surface method combined with the optimization algorithm and obtains the parameter set that can accurately describe the damage behavior of this material. The study also found that the nucleation-averaged plastic strain (${\epsilon }_N$) has the most significant effect on the maximum stress and fracture point of the stress–strain curve by the sensitivity analysis of six key parameters of the GTN model, while the other parameters change the shape of the curve and the local features to different degrees. Further analysis shows that the differences in yield strength and elongation can be attributed to the differences in basal slip, twinning behavior and dynamic recrystallization in the microstructure, which provides an important guidance for the optimization of the microstructure of AZ31 magnesium alloy. This study not only reveals the influence law of loading conditions on the mechanical properties of AZ31 magnesium alloy but also provides a theoretical basis and reference for understanding the damage mechanism of magnesium alloy and optimizing its mechanical properties. Full article

In order to effectively process crystal-structured materials like metal, knowledge of the working slip system during plastic deformation is necessary. Rolling is a widely utilized industrial processing method, and understanding its inherent characteristics can optimize the process and help achieve the desired microstructure and texture. One key aspect worth investigating is how shear deformation penetrates through the material thickness, particularly in relation to contact conditions. Analyzing slip system activity provides valuable insights into the deep penetration of shear deformation. This is achieved by examining orientation gradients derived from inverse pole figure maps obtained through electron backscatter diffraction. The rotation axis is extracted and compared with that obtained from calculation using simple first-order self-consistent formulation. The analysis was carried out on grains with $\left\{001\right\}<1\overline{1}0>$, $\left\{001\right\}<\overline{1}\overline{1}0>$, $\left\{111\right\}<1\overline{1}0>$, $\left\{111\right\}<1\overline{2}1>$, $\left\{111\right\}<0\overline{1}1>$, and $\left\{111\right\}<\overline{1}\overline{1}2>$ to see the activity of slip systems of $\left\{112\right\}<111>$ when plane strain or plane + shear mode is in operation. The rotation axis from the experiment is in agreement with that from the calculation, which confirmed the activity of the well-known $\left\{112\right\}<111>$ slip systems. It was found that $\left\{112\right\}<111>$ was active in solo in grain with {111}//ND orientation along the γ-fiber during the early stage of differential speed rolling (DSR). Furthermore, it was revealed that the $\left\{112\right\}<111>$ slip system was found active when shear deformation mode was in operation at the center of the sheet, which can only be found in the case of a sample with no lubrication. Conclusion: The current study shows that deep penetration was achieved under contact conditions where no lubrication was used during DSR by revealing the activity of the $\left\{112\right\}<111>$ slip system under the shear mode of deformation. Full article

Landslides on the Jiaxi Highway in Qinghai Province threaten construction safety and quality. The on-site data analysis shows that excavation at the foot of the slope and heavy rainfall are the key factors causing the displacement of the Q1 monitoring point by 1825 mm. This article uses numerical simulation methods combined with the strength reduction method to study the stability changes of slopes under different working conditions. Numerical simulations identified the landslide location and predicted a 1960 mm slip and a safety factor of 1.26 under natural conditions, indicating risks. The study adopted a strategy combining slope cutting, load reduction, and sheet pile wall reinforcement. After the first treatment, the safety factor rose to 1.83 with a 40 mm displacement; after the second, it reached 2.36 with a 37 mm displacement. Continuous monitoring showed a 50 mm displacement over six months, indicating stability. Rainfall simulations before and after treatment explained the stability evolution and local slope stability. Treatments increased the safety factor to 2.16 with a 17.6 mm displacement. This study significantly improved highway landslide stability and verified treatment effectiveness, providing a reference for similar geological conditions. Full article

Potential faults are common sensitive geological bodies that affect the safe mining of underground mines, often leading to major accidents such as rock instability and rockburst during mining. The failure mechanism of faults has been widely studied. However, due to the spatiotemporal specificity of fault occurrence, there are few theoretical and mathematical methods suitable for effective analysis in mine safety risk management. This study aims to introduce fractal theory to characterize the spatiotemporal activity fractal characteristics of induced faults intersecting the mining site and roadway during the mining process of the Ashele copper mine in China. Using microseismic systems and fractal theory, a spatiotemporal fractal model of the fault slip process is constructed, and a fractal analysis method is proposed. The fractal dimension value is calculated based on the spatiotemporal parameters of different segments and stages. The fractal dimension is used to characterize and analyze the evolution of the fault. The physical formation process of potential faults and the relationship between fractal dimension values and multiple parameters, including spatial clustering, regional distribution characteristics, and energy-release characteristics, were analyzed based on the division of events into different time stages. Discovering fractal dimension’s temporal and spatial–temporal characteristics can provide technical references for mine disaster prevention. Full article

Controlling microstructure and texture development is a key approach to improving the formability of magnesium alloys. In this study, the effects of the strain rate and initial texture on the texture evolution of magnesium alloys during high-temperature processing are investigated. The plane strain compression of three types of AZ80 magnesium alloys with different initial textures was assessed at 723 K and a train rate of 0.0005 s⁻¹. Work softening was consistently observed in the stress–strain curves of all samples. However, the peak stress varied depending on the initial texture, with lower peak stress observed under conditions favoring prismatic slip. Under these conditions, the activation of non-basal slip suppressed the formation of basal texture. The texture shifted and developed parallel to the transverse direction when prismatic slip was dominant. In contrast, the activation of pyramidal slip led to the formation of a basal texture tilted by 25° from the $\left(0001\right)$ plane. The effects of recrystallization and grain boundary migration on texture development were minimal. This study contributes to understanding the texture development mechanisms in magnesium alloys and provides insights into improving their workability and ductility through texture modification. Full article