Frictional Resistance Research Articles

Centrifuge Modeling of Backfill Consolidation in Soil-bentonite Cutoff Walls

Soil-bentonite (SB) is commonly adopted for the backfill of vertical cutoff walls to contain contaminated groundwater. The permeability of SB backfill is dependent on its effective stress state, which is affected by the backfill consolidation process. This paper presents a geotechnical centrifuge model test to simulate the primary consolidation of typical SB cutoff walls with the advantages of reduced scale in time and size. The moisture content and earth pressure of the wall were monitored at varied depths. Test results showed that the rapid consolidation stage developed swiftly and various consolidation indicators exhibited significant development. Within the buried depth over the half (approximately two-thirds), the distribution of vertical effective stress was similar to the Bucknell field testing results, namely that it increased nonlinearly and then tended to stabilize. Also, the cumulative effect of lateral frictional resistance increased with depth and reached its peak value. In the deeper buried areas, lateral frictional resistance decreased sharply before increasing again with increasing depth, while vertical effective stress followed a pattern of significant increase followed by a decrease. This centrifuge test may be useful for achieving a comprehensive evaluation of the consolidation behaviour and mechanism of SB cutoff walls.

Multi-Objective Optimization towards Heat Dissipation Performance of the New Tesla Valve Channels with Partitions in a Liquid-Cooled Plate

The utilization of liquid-cooled plates has been increasingly prevalent within the thermal management of batteries for new energy vehicles. Using Tesla valves as internal flow channels of liquid-cooled plates can improve heat dissipation characteristics. However, conventional Tesla valve flow channels frequently experience challenges such as inconsistencies in heat dissipations and unacceptably high levels of pressure loss. In light of this, this paper proposes a new type of Tesla valve with partitions, which is used as internal channel for liquid-cooled plate. Its purpose is to solve the shortcomings of existing flow channels. Under the working conditions of Reynolds number equal to 1000, the neural network prediction-NSGA-II multi-objective optimization method is used to optimize the channel structural parameters. The objective is to identify the optimal structural configuration that exhibits the greatest Nusselt number while simultaneously exhibiting the lowest Fanning friction factor. The variables to consider are the half of partition thickness H, partition length L, and the fillet radius R. The study result revealed that the optimal parameter combination consisted of H = 0.25 mm, R = 1.253 mm, L = 0.768 mm, which demonstrated the best performance. The Fanning friction factor of the optimized flow channel is substantially reduced compared to the reference channel, reducing by approximately 16.4%. However, the Nusselt number is not noticeably increased, increasing by only 0.9%. This indicates that the optimized structure can notably reduce the fluid’s friction resistance and pressure loss and slightly enhance the heat dissipation characteristics.

Computational analysis of air bubble-induced frictional drag reduction on ship hulls

About 60% of marine vessels’ power is consumed to overcome friction resistance between the hull and water. Air lubrication can effectively reduce this resistance and lower fuel consumption, and consequently emissions. This study aims to analyze the use of a gas-injected liquid lubrication system (GILLS) to reduce friction resistance in a real-world scenario. A 3D computational fluid dynamics model is adopted to analyse how a full-scale ship (the Sea Transport Solutions Designed Catamaran ROPAX ferry) with a length of 44.9 m and a width of 16.5 m is affected by its speed and draught. The computational model is based on a volume of fluid model using the k-ꞷ shear stress transport turbulence model. Results show that at a 1.5 m draught and 20 knots cruising speed, injecting 0.05 kg/s of compressed air into each GILLS unit reduces friction resistance by 10.45%. A hybrid model of natural air suction and force-compressed air shows a friction resistance reduction of 10.41%, which is a promising solution with less required external power. The proposed technique offers improved fuel efficiency and can help to meet environmental regulations without engine modifications.

Enhancement of serrawettin W1-producing Serratia marcescens cell migration by resonant oscillation under alternating current electric field

Swarming migration is observed in flagellated bacteria on wet surfaces. As the secreted biosurfactant hydrates, friction between the cell and the wet surface is reduced, and weak flagellar movement appears to be a significant force for cell translocation. Developing an artificial swarming control method could greatly aid in establishing techniques for biofilm inhibition and detachment. In this study, the effect of forced cell vibration by an alternating current electric field (ACEF) on swarming motility was investigated using the serrawettin W1-producing Serratia marcescens strain. At frequencies close to the natural frequencies of microbial cells (12 MHz), swarming motion was effectively enhanced in biosurfactant-producing S. marcescens, but not in non-surfactant-producing Escherichia coli or non-flagellated Staphylococcus aureus. Electric field-assisted cell migration was significantly induced under swarming conditions with low friction resistance between the cell and gel surface. This finding suggests a direction for developing strategies to regulate biofilm formation and detachment using ACEF-assisted oscillation of cells attached to surfaces.

Performance of low shrinkage Bis-EFMA based bulk-fill dental resin composites

ObjectivesThe purpose of this study was evaluating the performance of new Bis-EFMA based bulk-fill composites with common methacrylate based composites and commercial dental composites. MethodsThe Bis-EFMA monomer was synthesized and the novel Bis-EFMA based bulk-fill composites were prepared. The resin composite samples were co-cultured with human gingival epithelial cells and human dental pulp stem cells to test the biocompatibility. The edge adaptation was observed under a combination of stereoscope and scanning electron microscope. The internal hardness was measured using a Vickers microhardness tester after one-time filling of cavities prepared in extracted teeth. After friction and wear test on the surface of the resin composites, the surface morphology and volume wear of each group were measured by the optical profilometer. The color stability was measured by a colorimeter. ResultsDirect contact with human gingival epithelial cells and human dental pulp stem cells did not cause significant changes in their growth density and morphology, indicating good biocompatibility of Bis-EFMA group (p > 0.05). The continuous margin proportion of the Bis-EFMA group was as good as commercial bulk-fill composites (p > 0.05). The sectional microhardness results showed that the Bis-EFMA group had the highest microhardness. After the friction and wear test, the volume wear of the Bis-EFMA group was minimal, indicating its good wear resistance and mechanical strength. Color changes in all resin groups after 28 days of immersion were within the clinically acceptable range. SignificanceThe addition of Bis-EFMA demonstrated excellent biocompatibility, edge adaptation and color stability comparable to commonly used clinical bulk-fill composites, along with preferable mechanical strength, friction and wear resistance. Bis-EFMA based bulk-fill composites have the potential to be employed as a bulk filling material in commercial dental composite applications.

Numerical investigation of the behavior of combination connections with pretensioned high-strength bolts and longitudinal fillet welds

Numerical analysis is conducted to investigate the behavior of double shear combination connections made with pretensioned high-strength bolts and longitudinal fillet welds. The finite element (FE) models were validated using the results of an experimental investigation and utilized to develop a better understanding of the influence of critical input parameters on the connection behavior. Slip-dependent surface frictional and weld ductile fracture models were incorporated into the numerical models to simulate the nonlinear behavior of the connections. The numerical simulations confirm that at low slip displacements, the force carried by the combination connection can be estimated as the summation of the friction resistance introduced by the pretensioned bolts and the shear force carried by the fillet welds. The results also indicate that the behavior and capacity of the combination connection are not sensitive with respect to the weld location compared to the center of gravity of the bolts as long as no eccentricity is introduced within the force transfer mechanism. The paper also investigates the stress distribution within the connection plates and studies the effect of fillet weld size on the behavior of combination connections.

Analytical solution for axially loaded floating pipe piles in homogeneous elastic soil layer

An analytical solution for the analysis of open-ended floating pipe piles in a homogeneous elastic soil layer is developed in this paper, based on the Tajimi-type elastic continuum model. Solving the governing equations of the outer and inner soil results in closed-form expressions for the external and internal frictional resistances developing at the soil-pile interfaces. The one-dimensional rod theory is adopted to model the pipe pile and its underlying soil hollow column. The external and internal frictional resistances are substituted into the governing equations of the pile and soil column to derive closed-form solutions for the vertical displacement and head stiffness of the pipe pile. The accuracy of the proposed model is verified by comparisons against existing numerical studies. Finally, parametric analyses are presented to discuss the sensitivity of the behavior of axially loaded floating pipe piles to the main problem parameters.

Experimental insights on biofouling growth in marine renewable structures.

Marine biofouling is a threat to industries working in the marine environment, representing significant costs associated with equipment impairment and loss of performance. In the Marine Renewable Energy (MRE) and other maritime sectors which operate at sea for long periods, an important aspect of biofouling is related to the type and frequency of inspections and biofouling removal procedures. This study investigated important parameters of macrofouling ( e.g. composition, including the presence of non-indigenous species, thickness, and weight) from communities growing on samples that emulate tubular components of marine renewable devices. The trials were performed during short periods of submersion (one to eight weeks) in the seasons when the colonisation process should be most intensive (spring, summer, and autumn). Furthermore, the frictional resistance forces generated during the scraping of biofouling from those components were investigated. Overall, results provide insights on the growth rates and removal requirements of biofouling in marine components. The results show that, while biofouling growth in early colonization stages might not present great detrimental effects to wave energy components, the consequent marine corrosion (fostered by biofouling) and the settlement of non-indigenous species (NIS) should be factors of concern. Performing biofouling-related maintenance activities after the peak of maximum growth and reproduction (during the warmer seasons in temperate to cold environments) is suggested to reduce the number and frequency of activities. NIS can be detected at very early stages in the colonization process, highlighting the importance of biofouling monitoring and the implementation of biosecurity risk assessment plans early in the operational stage of MRE projects.

ANALISIS PERBANDINGAN KARAKTERISTIK ALIRAN TERADAP NILAI KEKASARAN PIPA YANG BERBEDA

Flow obstructions often occur in the flow that passes through a pipe installation. As a result, head loss and pressure drop occur which are influenced by fluid friction and changes in the flow pattern of a pipe. However, under certain conditions, frictional resistance is only influenced by fluid viscosity. The aim of this research is to analyze the characteristics of the flow of roughness values ​​in PVC pipes and the flow of roughness values ​​in PP-R pipes using experimental methods carried out in the laboratory. The data that has been collected analyzed using the Reynolds equation, Darcy equation and Bernoulli equation. The research results showed that the characteristic of PVC pipes with the largest froude number value which 0.315 and the smallest which 0.090 were subcritical flow. Meanwhile, the characteristic of the PP-R pipe with the largest froude number value which 0.297 and the smallest which 0.057 were also subcritical flow.

Presence of Frozen Fringe Impacts Soft‐Bedded Slip Relationship

AbstractGlaciers and ice streams flowing over sediment beds commonly have a layer of ice‐rich debris adhered to their base, known as a “frozen fringe,” but its impact on basal friction is unknown. We simulated basal slip over granular beds with a cryogenic ring shear device while ice infiltrated the bed to grow a fringe, and measured the frictional response under different effective stresses and slip speeds. Frictional resistance increased with increasing slip speed until it plateaued at the frictional strength of the till, closely resembling the regularized Coulomb slip law associated with clean ice over deformable beds. We hypothesize that this arises from deformation in a previously unidentified zone of weakly frozen sediments at the fringe's base, which is highly sensitive to temperature and stress gradients. We show how a rheologic model for ice‐rich debris coupled with the thermomechanics of fringe growth can account for the regularized Coulomb behavior.

Design and application of a monitoring device for embedded foundation side friction resistance

Design and application of a monitoring device for embedded foundation side friction resistance

Enhancing optical and thermohydraulic performance of linear Fresnel collectors with receiver tube enhancers: A numerical study

Linear Fresnel collector system is a type of solar thermal utilization installation. It is mainly used to focus solar radiation on the receiver tube to generate high temperature thermal energy which can be applied in many aspects. This study investigates five different types of receiver tube models using water as the flowing medium, which leads to improving heat transfer performance by means of being equipped with enhancers. The optical results and thermohydraulic performance of the Linear Fresnel collector system are evaluated through Monte Carlo Ray Tracing and Computational Fluid Dynamics (CFD) simulation methods. The obtained optical results reveal that the distribution of energy flux density concentrating on the receiver tube surpasses that of the parabolic trough collector system. In order to maintain an energy reception rate of 90.0% or higher, the installation height range of the receiver tube should be between 1468–1532 mm. When the sun-tracking error increases from 0.0° to 1.0°, the overall optical efficiency of the Linear Fresnel collector system decreases from 98.9% to 79.7%. The thermohydraulic performance shows that the enhancers can generate a swirling flow as its main feature, which effectively promotes the homogenization of the temperature field and destroys the boundary layer near the receiver tube wall, thus greatly improving the convective heat transfer in the receiver tube. However, the introduction of the enhancers also means that the pressure drop loss of the receiver tube increases. Furthermore, the impact of the Kenics mixer's enhancer on heat transfer and flow characteristics is further amplified as the rotation rate decreases, owing to its alternating and complex structure. Through a comparative analysis of the influence of different receiver tube models on Nusselt number (Nu), Frictional resistance coefficient (f) and comprehensive evaluation criterion (PEC) under four rotation rate conditions (y = 6.3, 8.1, 11.34, 18.9), the conclusions present that the receiver tube with an enhancer at a low rotation rate has a larger Nu than that at a high rotation rate, while the Frictional resistance coefficient changes little at different rotation rates. Therefore, the PEC is higher when the receiver tube is equipped with a low-rotation-rate enhancer. Moreover, the receiver tube equipped with a Kenics mixer at a rotation rate of 6.3 was found to be the overall optimum case, with the PEC value varying from 1.47 to 1.73.

Heat and mass transfer analysis for bi-dimensional bioconvective MHD nanofluid with varying thermal traits

ABSTRACT Bioconvection phenomena offer practical applications in biomicrosystems, fuel cells, biosensors, biocomputing, electronic thermal management, and renewable energy systems, showcasing their relevance and potential impact across various engineering sectors. Consequently, this study delves into the examination of a bi-dimensional magnetohydrodynamic nanofluid flow model encompassing the intricate dynamics of gyrotactic microorganisms, subject to the effects of suction and thermal radiation. The primary objective of the investigation is to optimize the thermal energy transfer efficiency of the fluid while concurrently minimizing associated costs, with the secondary aim of diminishing the frictional resistance at the fluid-solid interface. The basis for energy and momentum equations incorporating radiation using Rosseland’s approximation is established by the Buongiorno nanofluid model. The foundational PDEs along with their BCs, are reformulated into ODEs utilizing similarity variables, then transformed into a set of first-order ODEs ensuring compatibility with MATLAB’s bvp4c solver, which offers high convergence rates and accuracy due to its efficient algorithms and precision handling. Heat transfer rate boosts up by increasing suction and radiation parameters, while it dwindles due to an increase in the magnetic field. Enhancing suction and the magnetic field lowers skin friction. Microbial concentration surges by increasing the magnetic field, while suction minimizes it. Intensifying the thermophoresis parameter increases the concentration of nanoparticles.

The development of B/Cr co-doped DLC coating by FCVA deposition system and its tribological properties at 300 °C

The diamond-like carbon (DLC) coating prepared using filtered cathodic arc deposition (FCVA) lost its promising wear resistance under high temperatures. Element-doped DLC coatings have been investigated to suppress carbon oxidation reaction and subsequently enhance the wear resistance in high-temperature environments. Previous research clarified the excellent tribological properties of boron-doped DLC (B-DLC) but identified challenge such as arc discharge extinguishment and coating declamation (under high-temperature friction test). In this study, the introduction of Argon gas (10 sccm) during the deposition process stabilized stable arc discharge, resulting in high hardness and deposition rate. Moreover, a chromium interlayer and varying concentration of Cr dopant (0.5 %, 1.0 %, 3.0 % at.) were added to B-DLC to develop a stable, co-doped DLC with low friction and high wear resistance. Raman spectroscopy and nano-indentation revealed an increase in the disordered carbon structure and reduction in hardness and Young's Modulus with Cr doping. Macroscopic ball-on-disk friction test, showed 1 % Cr-doped B-DLC (a-C:B:Cr1) coating exhibited super low friction (avg. coefficient 0.02) and a low specific wear rate (<5.0 × 10−6 mm3/Nm). Raman spectroscopy indicated that the transferred graphite-like tribo-film onto the surface of Si3N4 counterparts contributed to stable low friction. Additionally, XPS analysis on the DLC coatings' wear track suggested the rich BB bond might contribute to its high wear resistance. This successful improvement on element-doped DLC prepared by FCVA provided valuable insights for further exploration of DLC coating applied to various working situations.

A Comparative Evaluation of Frictional Resistance of Various Lingual Brackets With Nitinol (NiTi) Archwires of Different Dimensions: An In Vitro Study.

Introduction Orthodontic mechanics involves transferring some of the applied force to the tooth's supporting components via friction, which in turn allows the tooth to move more easily. Aim The purpose of this in vitro experiment was to examine the frictional resistance (FR) of different lingual brackets utilizing Instron universal testing machines and nitinol (NiTi) archwires of varying sizes. Materials and methods Twenty-four sectional anterior die stones were replicated from a study model. They were categorized into eight categories, with the Libral lingual bracket and the JJ lingual bracket having 0.012" and 0.014" inch NiTi archwire, which were further subdivided into six subgroups. Three brackets were bonded to the anterior teeth of the upper and lower segments and replicated on other models with the help of silicon putty. Elastomeric modules were ligated to two diameters of NiTi wire (0.012" and 0.014") in each model. An Instron universal testing machine was used to measure the frictional force. Numerical data and descriptive statistics such as mean and standard deviation have been shown. Results In the overall analysis, it was observed that among JJ Orthodontics samples using 0.012" NiTi archwires, the maxilla exhibited a higher FR (4.205N) compared to the mandible (4.092N). Similarly, in the case of Libral Orthodontics samples with 0.012" NiTi archwires, the maxilla also demonstrated a higher FR (5.10N) than the mandible (4.97N). However, this trend did not hold for samples using 0.014" NiTi archwires. There was a statistically nonsignificant difference (p > 0.05) in the values between all the pairs of groups. Conclusion The present study concludes that Libral lingual brackets produced overall more FR than JJ lingual brackets.

Effects of graphene addition on the mechanical, friction and corrosion properties of laser powder bed fusion 316L stainless steel

Laser powder bed fusion of 316 L (LPBF-316 L) has been known to exhibit high ductility but low strength, along with strong corrosion resistance and weak anti-friction properties. Graphene is commonly utilized as a reinforcement phase in metals fabricated through LPBF, as this process helps reduce the tendency of graphene to agglomerate. Therefore, it is crucial to investigate the impact of incorporating graphene into the LPBF-316 L alloy, aiming to enhance toughening and anti-friction properties while maintaining the original corrosion resistance. Various concentrations of graphene were incorporated into 316 L powder and processed using LPBF. The study examined the impact of graphene concentration on the electrochemical, mechanical, and friction properties of the resulting composites. The study revealed a significant reduction in corrosion current from 8.05 ± 0.6 × 10−7 A/cm2 to 6.61 ± 0.8 × 10−8 A/cm2. The 15-day immersion experiment further validated that the incorporation of graphene contributed to enhancing the stability of corrosion resistance. Additionally, the presence of graphene led to improved strength and ductility in LPBF-316 L through grain refinement and precipitation. Notably, samples containing 0.2 wt% graphene exhibited a tensile fracture strength of 927.4 MPa and ductility of 54.75%. In addition, the compressive fracture strength of 2342.8 MPa, both surpassing that of LPBF-316 L. Furthermore, the study investigated the impact of graphene content on the friction of LPBF-316 L, revealing that graphene addition increased matrix hardness, reduced COF, and enhanced wear resistance. Overall, the findings suggest that graphene serves as an effective reinforcing agent for 316 L stainless steel matrix composites, enhancing mechanical properties, friction resistance, and wear resistance while preserving original corrosion resistance.

The Experimental Characterization of Iron Ore Tailings from a Geotechnical Perspective

The mining industry produces large amounts of tailings which are disposed of in deposits, which neglects their potential value and represents important economic, social and environmental risks. Consequently, implementing circular economy principles using these unconventional geomaterials may decrease the wide-ranging impacts of raw material extraction. This paper presents an experimental characterization of iron ore tailings, which are the most abundant type of mining waste. The characterization includes various aspects of behavior that are relevant to different types of use as a building material, including physical and identification properties, compaction behavior and stress–strain properties under undrained monotonic and cyclic triaxial loading. The tailings tested can be described as low-plasticity silty sand materials with an average solids density of 4.7, a maximum dry unit weight close to 3 g/cm3 and a higher angle of friction and liquefaction resistance than common granular materials. The experimental results highlight the particular features of the behavior of iron ore tailings and emphasize the potentially promising combination of high shear resistance and high density that favors particular geotechnical applications. Overall, the conclusions provide the basis for promoting the use of mining wastes in the construction of sustainable geotechnical works and underpin the advanced analysis of tailings storage facilities’ safety founded on an open-minded geotechnical approach.

Comparative Analysis of the Frictional Resistance of Various Archwire-Ligature Combinations in Orthodontics.

Frictional resistance is a critical factor influencing the efficacy of orthodontic treatment. Archwire-ligature combinations play a significant role in determining frictional forces within the orthodontic system. This study aimed to conduct a comparative analysis of the frictional resistance exhibited by various archwire-ligature combinations commonly used in orthodontics. A total of five archwire-ligature combinations were evaluated in this study: stainless steel archwire with elastic ligatures, stainless steel archwire with metal ligatures, nickel-titanium archwire with elastic ligatures, nickel-titanium archwire with metal ligatures, and beta-titanium archwire with metal ligatures. Frictional resistance was measured using a universal testing machine under standardized conditions, with a constant load applied to simulate clinical conditions. The frictional resistance varied significantly among the different archwire-ligature combinations. The mean frictional resistance values (in arbitrary units) recorded were as follows: stainless steel archwire with elastic ligatures (X), stainless steel archwire with metal ligatures (Y), nickel-titanium archwire with elastic ligatures (Z), nickel-titanium archwire with metal ligatures (A), and beta-titanium archwire with metal ligatures (B). Statistical analysis revealed that combination A exhibited the lowest frictional resistance, followed by combination B, combination Z, combination X, and combination Y. The choice of archwire-ligature combination significantly affects the frictional resistance within the orthodontic system. Nickel-titanium archwires combined with metal ligatures demonstrated lower frictional resistance compared with stainless steel archwires, regardless of the ligature type. Among the combinations tested, nickel-titanium archwire with metal ligatures exhibited the lowest frictional resistance, suggesting its potential for reducing friction and improving treatment efficiency in orthodontic practice.

Numerical Study on Heat Transfer and Frictional Resistance of Two Types of Molten Salts in Straight Channels and Supercritical Carbon Dioxide in Airfoil Channels

Numerical Study on Heat Transfer and Frictional Resistance of Two Types of Molten Salts in Straight Channels and Supercritical Carbon Dioxide in Airfoil Channels

Investigation on dynamic mechanism of fault slip and casing deformation during multi-fracturing in shale gas wells

Fracturing horizontal well casing deformation has become very prominent, particularly in tectonic stress-concentrated shale gas fields, limiting the efficient development progress of shale gas. The main failure mode of casing shearing deformation had been attributed to fault slip caused by multi-fracturing. The current research did not provide a clear picture of the dynamic evolution relationship between hydraulic fracturing, fault slip, and casing deformation. In this paper, the dynamic model of fault slip induced by formation pressure change is established, incorporating the effects of stress drop, physical change of friction, and casing and cement-sheath resistance loads. The discontinuous displacement approach and explicit/implicit coupling iteration methods are used to reveal the relationships between the effective normal stress, shear stress, friction coefficient, and sliding velocity during the fault slip process. Furthermore, the microscopic process of casing deformation sheared by fault slip is investigated using static equilibrium theory, and a characterization method for determining the amount casing deformation caused by real-scale fault slip is proposed. The results show that three stages exist in the process of casing deformation sheared by fault slip, including trigger activation stage, accelerated slip stage, and deceleration slip stage. Fault slip is clearly influenced by fault strike. To reduce the amount of fault slip, the fault direction with the maximum in-situ stress should be avoided as much as possible. Serious casing deformation still occurs for large-scale activated faults even though the optimization measure of wellbore structure has been well taken. To fundamentally reduce the possibility of casing shear deformation, it is necessary to prevent fault slip through optimizing the design of hydraulic fracturing. This study lays the theoretical groundwork for the casing deformation control method in shale gas wells.