Slip Regime Research Articles

A new accurate solution method for steady forced convection in an unbounded flow around a circular cylinder in continuum and slip regimes

A new accurate numerical solution method for steady forced convection in an unbounded bidimensional flow around a circular cylinder is presented, addressing both the no-slip and slip regimes for Reynolds numbers and Knudsen numbers within the range 0.01 ≤ Re ≤ 47 and 0 ≤ Kn ≤ 0.1. The challenge of singular behaviour in infinite domains, which degrades numerical precision, is effectively mitigated by our new approach, unlike previous methods that truncate the flow domain. This method provides complete and correct description of the flow near the cylinder and in the far field perfectly reproducing the asymptotic solutions at large distances. We also present a new effective analytical solution for Oseen flow with slip effects, accurately representing flow at low Reynolds numbers. The validity of our numerical solution is confirmed by extensive comparisons with analytical solutions and numerical and experimental data from the literature. Additionally, we derive a new accurate correlation formula for the Nusselt number in slip flow regimes, involving both scenarios with and without temperature jump. This formula is crucial for engineering applications, especially in constant temperature hot-wire anemometry, as it avoids the requirement to correct heat transfer measurements due to slip and temperature jump effects when using very small diameter wires.

A theoretical derivation of slip boundary conditions based on the Cercignani–Lampis–Lord scattering model

To characterize fluid flow in the slip regime, the use of Navier–Stokes–Fourier (NSF) equations with slip boundary conditions is prevalent. This trend underscores the necessity of developing reliable and accurate slip boundary conditions. According to kinetic theory, slip behaviours are intrinsically linked to the gas scattering processes at the surface. The widely used Maxwell scattering model, which employs a single accommodation coefficient to describe gas scattering processes, reveals its limitations when the difference between accommodation coefficients in the tangential and normal directions becomes significant. In this work, we provide a derivation of velocity slip and temperature jump boundary conditions based on the Cercignani–Lampis–Lord scattering model, which applies two independent accommodation coefficients to describe the gas scattering process. A Knudsen layer correction term is introduced to account for the impact of the surface on the velocity distribution function, which is associated with the scattering model. The governing equation of the correction term is established based on the linearized Boltzmann equation. Additionally, two moments are derived to capture the collision effect in the Knudsen layer: a conserving moment of collision invariants, and an approximate higher-order conserving moment. These moments are then employed to determine the coefficients in the correction term. We demonstrate that the derived slip coefficients align closely with numerical results obtained by solving the Boltzmann equation in the Knudsen layer. Besides, we apply the derived slip boundary conditions within the framework of the NSF equations, yielding numerical results that exhibit excellent consistency with those obtained through molecular-level simulations.

Fretting corrosion behavior and microstructure evolution of hydrided zirconium alloy under gross slip regime in high temperature high pressure water environment

Fretting corrosion behavior and microstructure evolution of hydrided zirconium alloy under gross slip regime in high temperature high pressure water environment

Boundary Element Method for Viscous Flow through Out-phase Slip-patterned Microchannel under the Influence of Inclined Magnetic Field

Abstract In this paper, we investigate the impact of an inclined magnetic field of uniform intensity on viscous, incompressible pressure-driven Stokes flow through a slip-patterned, rectangular microchannel using the boundary element method based on the stream function-vorticity variables approach. The present investigation focuses only on the out-phase slip patterning of the microchannel walls. We address two scenarios of slip patterning, specifically large and fine slip patterning, which are determined by the periodicity of the patterning. We utilized the no-slip and Navier’s slip boundary conditions in an alternative manner on the walls. The Stokes equations govern the viscous flow through a microchannel. We assume a very small magnetic Reynold’s number to eliminate the equation of induced magnetic field in the present study. We analyzed the impact of considered dimensionless hydrodynamic parameters, including the Hartman number (Ha), inclination angle (θ) of the magnetic field, and the slip length (ls ) on fluid dynamics. In the case of fine slip, we observed significant variations in both velocity and pressure gradient, in contrast to large slip patterning. Fine slip patterning significantly increases the shear stress at slip regimes, while large slip periodicity significantly reduces it at no-slip regimes. The present investigation has several notable implications, such as regulation and advancement of mixing and heat transmission within microfluidic systems.

Insight into the fretting corrosion behavior of 316L steel in liquid lead-bismuth eutectic at 500°C

Due to flow induced vibration caused by coolant circulation, fretting corrosion inevitably occurs between fuel cladding, heat exchanger tubes and their holders in Gen IV lead-bismuth eutectic (LBE) cooled nuclear reactors. In the current work, fretting corrosion behavior of 316 L steel in oxygen-saturated LBE at 500 °C has been investigated. It is shown that within the gross slip regime, the microstructure under fretting interface presents a stratified structure, composed of third body layer, oxide scales and plastic deformation layer. At the early stage of fretting corrosion, the dominant damage mechanism is fretting wear, showing that the thickness of third body layer is much larger than that of oxide scale. As fretting time increases, the dominant damage mechanism is gradually changed to LBE corrosion and fretting wear together, as the visible oxide scale is formed next to the third body layer. Moreover, the growth rate of oxide scales under fretting interface is accelerated by over an order of magnitude compared to that when 316 L steel exposed to LBE directly. In particular, after 60 h exposure, the thicknesses of oxide scale related to the worn and unworn regions are ∼4.5 μm and ∼0.2 μm, respectively. The occurrence of such phenomenon is thought to be ascribed to the severe plastic deformation under fretting contact interface, since the crystal defects served as perfectional nano-channels can promote the diffusivity of oxygen atoms. In addition, the acceleration diffusivities of oxygen atoms caused by the local high contact stress may also be responsible for this matter.

Independent friction-restitution modeling of collisions: application to planar sphere rebound on a massive surface

The most widely used impulse-based description of impact events expresses it in terms of the coefficient of restitution (normal and tangential) and friction. This model leads to significant variations of the coefficients of tangential restitution and friction with the impact angle. An alternative formulation is presented based on the idea that friction and restitution can be treated as ‘mechanisms’ operating simultaneously but independently throughout the impact. The resulting independent friction restitution closure describes the impact for both stick and slip regimes using the same set of ‘constant’ coefficients of restitution (normal and tangential) and friction. The model yields theoretical predictions in agreement with reported experimental data including several results considered as ‘anomalous’ in the literature.

Effect of external magnetic field on the fretting wear mechanism of the ferromagnetic materials

With the widespread implementation of maglev technology in fields such as rail transit and military, it is imperative to investigate the effects of magnetic fields on fretting damage in metallic materials. This study conducted multi-parameter fretting wear tests on typical ferromagnetic counterparts in the presence of an external permanent magnetic field. Subsequently, the wear behavior and damage mechanism of the fretting interface were elucidated through multi-scale characterization analysis. The results indicated that the operation state of the fretting interface was shifted towards the partial slip regime under the magnetic field. Meanwhile, the external magnetic field transformed the dominant wear mechanism from abrasive wear to adhesive wear. The influence of the external magnetic field on fretting wear has been demonstrated to manifest in dual aspects: Firstly, the Hertzian contact stress at the interface is enhanced by the magnetic field induction force, resulting in a remarkable reduction of about 79.83 % in accumulated dissipation energy; Secondly, the effectiveness of debris being expelled from the worn interface decreased, and the wear progression was further impeded by the accumulated debris, so that the abrasion loss is significantly reduced by about 60.66 %. These findings provide valuable theoretical data and practical reference for the protection of fretting damage in ferromagnetic materials under the action of a magnetic field.

Experimental and Numerical Investigation of Slip Effect on Nanofiber Filter Performance at Low Pressures.

Nanofiber filters are widely used in air filtration applications due to their superior performance over microfiber filters. Velocity slip around nanofibers has been identified as a key factor contributing to their high figure of merit, yet its impact on filter performance, especially particle collection efficiency, remains unclear due to the difficulty in isolating the slip effect as the sole variable. This study combines experimental and simulation methods to investigate the slip effect by adjusting the air molecule mean free path, rather than varying fiber size as done in previous studies. Filter media with mean fiber sizes ranging from 16.2 to 0.084µm are utilized. An image-based regression method is developed to address the challenge of determining the solidity of thin nanofiber layers. The results show that the slip effect is enhanced as the testing pressure decreases, reducing pressure drop by less than 15% for microfiber filters and over 50% for nanofiber filters ≈100nm. The enhanced slip effect at low pressures (i.e., relatively low pressure compared to the ambient environment) significantly improves filtration efficiency, especially for particles larger than 100nm. It also proposes semi-empirical equations for predicting filter performance in slip and transition flow regimes.

Evolution of fretting wear behavior of zirconium alloy cladding tube under gross slip regime in simulated primary water of pressurized water reactor

The evolution of fretting wear behavior of zirconium alloy cladding tubes mated with dimples under the gross slip regime (GSR) was investigated. The findings revealed that the primary wear mechanisms under GSR were delamination, surface fatigue wear and abrasive wear, and the fretting damage rate mainly depends on delamination. The cross-sectional microstructure of the worn area could be divided into the third-body layer, tribologically transformed structure layer, and general deformation layer, with their formation mechanisms analyzed. Furthermore, the mechanism of wear-induced grain refinement was identified as dynamic recrystallization (DRX), including both continuous DRX and discontinuous DRX. Additionally, the processes of fretting wear and DRX were discussed.

Dependence of fretting wear resistance on the α morphology and stress-induced martensite transformation in a metastable β titanium alloy

Systematic experimental investigations concerning the influence of α morphology on the fretting wear behaviors of metastable β titanium alloys are carried out. A Ti-10V-2Fe-3Al titanium alloy was subjected to different heat treatment routes to create dual phase microstructures consisted of β phase plus α phase with three different morphologies. The effect of α morphology on the fretting wear resistance, the resulting failure mechanisms, and stress induced martensite transformation (SIMT) were unraveled. Results show that the α morphology has a significant influence on fretting wear behaviors depending on the fretting run regimes. In the partial slip regime (PSR) and mixed fretting regime (MFR), the microstructure with lath α morphology has a lowest fretting wear volume accompanied by relatively strong SIMT effect. While in gloss slip regime (GSR), the globular α microstructure has a lowest fretting wear volume along with strongest SIMT response, yet a highest fretting wear volume for the acicular α morphology microstructure due to its brittleness nature. The subsurface observations demonstrates that a compacted and thick plastic deformation layer, especially for the mechanical mixture layer, can well protect the material surface against the fretting wear damage.

Modeling of residual stiffness phenomenon in modified Iwan model of bolted joints and its application

Bolted joints have been widely used in various mechanical structures. Due to the presence of contact interfaces, the joints exhibit complex nonlinear behavior under dynamic loading. Effective prediction of the dynamic response of bolted structures requires the construction of appropriate dynamic models. This paper proposes a modified Iwan model which gives a more comprehensive description of joints than the previous Iwan models, especially for the phenomenon of residual stiffness in macro slip. The equations of the model's backbone curve, hysteresis curve, and energy dissipation are derived. The parameter identification procedure is also provided. Subsequently, connection elements based on the modified Iwan model are integrated into a single bolted joint and a thin-walled cylinder containing multiple bolted joints, the responses under quasi-static unidirectional loading, quasi-static cyclic loading and constant-frequency excitation are investigated. The physical interpretation of the parameters in the model is discussed, thus explaining the relationship between the bolted joint's physical parameters and some important variables. The results indicate that the model can effectively characterize the nonlinear mechanical behavior of the bolted joint for both micro and macro slip regime, with significant improvement in computational efficiency.

Fretting wear mechanism of DZ125 surface created by WEDM

In this paper, the fretting wear mechanism of the directionally solidified superalloy (DZ125) surface created by wire electrical discharge machining (WEDM) are studied. Samples with varying surface characteristics are prepared by changing the number of wire cutting (NWC), ranging from one to five times (NWC-1 to NWC-5). Comparative analysis reveals that the NWC-3 exhibits the best surface characteristics. Subsequent fretting wear tests under different displacement amplitudes show increased dissipation energy with greater displacement. Compared with other samples, NWC-3 in the synergistic effect of surface roughness and hardness exhibits excellent fretting wear performance. In addition, the fretting mechanism transitions from mixed slip regime (MSR) to gross slip regime (GSR) as the displacement increases. The wear mechanism transitions from abrasive wear to oxidation wear and adhesive wear.

Comparative study on tribological behaviors of interproximal tooth enamel against zirconia under fretting and sliding conditions

Interproximal contact loss (ICL) between zirconia crown and adjacent natural teeth is a common complication that could lead food impaction and compromise the periodontal/peri-implant tissue health and patient’s satisfaction. Both fretting and sliding wear mode can be found in the frictional pair between zirconia crown and interproximal enamel during mastication. In this study, fretting and sliding wear behavior of interproximal enamel against zirconia in artificial silva was investigated. The wear damage of the interproximal enamel in a sliding movement was higher than in a fretting movement. In fretting mode, the running condition fretting map (RCFM) composed of partial slip regime (PSR), gross slip regime (GSR), and mixed fretting regime (MFR) was constructed depending on different normal loads and displacement amplitudes. Intact surface was observed in the PSR. Plastic deformation at contact center and microcracks at contact margin were detected in the MSR. Severe wear damage occurred in the GSR, predominated by microfracture, brittle deformation. Macroparticles generation, fatigue delamination and abrasive wear prevailed in sliding mode. In contrast, enamel debris could be transferred on zirconia surface while the material loss of the antagonist zirconia was negligible in both fretting and sliding test.

Fretting-corrosion mechanisms of Ti6Al4V against CoCrMo in simulated body fluid under various fretting states

Ti6Al4V alloy–CoCrMo alloy pair is commonly applied for modular head–neck interfaces for artificial hip joint. Unfortunately, the fretting corrosion damage at this interface seriously restricts its lifespan. This work studied the fretting corrosion of Ti6Al4V–CoCrMo pair in calf serum solution. We established this material pair’s running condition fretting map (RCFM) regarding load and displacement, and revealed the damage mechanism of this material pair in various fretting regimes, namely partial slip regime (PSR), mixed fretting regime (MFR), and gross slip regime (GSR). The damage mechanism of Ti6Al4V alloy was mainly abrasive wear induced by CoCrMo alloy and tribocorrosion. Adhesive wear (material transfer) also existed in MFR. The damage mechanism of CoCrMo alloy was mainly abrasive wear induced by metal oxides and tribocorrosion in GSR and MFR, while no apparent damage in PSR. Furthermore, a dense composite material layer with high hardness was formed in the middle contacting area in GSR, which reduced the corrosion and wear of Ti alloys and exacerbated damage to Co alloys. Finally, the ion concentration maps for Ti and Co ions were constructed, which displayed the transition in the amount of released Ti and Co ions under different displacements and loads.

Effect of fretting wear regimes on stress corrosion cracking of Alloy 690TT in high-temperature pressurized water

Stress corrosion cracks initiation and propagation of Alloy 690TT under different fretting regimes were investigated. The results indicated that mixed regime had the highest susceptibility to stress corrosion cracking, followed by gross slip regime, and then partial slip regime. Crack initiation depended on the distribution of residual strain induced by fretting regimes. In partial slip and mixed regimes, cracks were mainly initiated at the edge of the wear scar, while in gross slip regime, cracks were randomly distributed on the wear scar. Crack propagation was related to the type of grain boundaries and geometrically necessary dislocation density induced by fretting loading. In partial slip and gross slip regimes, cracks usually tended to propagate intergranularly. While in MR, cracks mainly propagated in a transgranular manner.

Influence of Chloride Concentration on Fretting Wear Behavior of Inconel 600 Alloy.

The nickel-based alloy Inconel 600, strengthened by solution treatment, finds extensive application as a heat exchange pipe material in steam generators within nuclear power plants, owing to its exceptional resistance to high-temperature corrosion. However, fretting corrosion occurs at the contact points between the pipe and support frame due to gas-liquid flow, leading to wear damage. This study investigates the fretting wear behavior and damage mechanism of the nickel-based alloy Inconel 600 and 304 stainless steel friction pairs under point contact conditions in a water environment. Characterization was performed using laser confocal scanning microscopy and scanning electron microscopy equipped with energy-dispersive spectroscopy. Results indicate that the friction coefficient remains consistent across different chloride ion concentrations, while the wear volume increases with increasing chloride concentrations. Notably, friction coefficient oscillations are observed in the gross slip regime (GSR). Moreover, the stability of the oxide layer formed in water is compromised, diminishing its protective effect against wear. In the partial slip regime (PSR), friction coefficient oscillations are absent. An oxide layer forms within the wear scar, with significantly fewer cracks compared to those within the oxide layer in the GSR. It is worth noting that in GSR, the friction coefficient oscillates.

Improving frictional state at fretting interfaces through the covalent structure of diamond–graphite–graphene

This study proposes a novel approach based on the covalent structure of diamond–graphite–graphene (CDGG) to integrate the outstanding properties of diamond, graphite, and graphene, synergistically improving frictional behavior of fretting interfaces. The results demonstrated that in-situ CDGG significantly reduced the alternating stress at the contact interface, the friction coefficient decreased by 40–62 % over pristine diamond coatings under gross slip regime, accompanied by a shorter running-in period. The counterpart pair wear corresponding to in-situ CDGG was lower, and no delamination caused by metal adhesion. The surface graphene/graphite exhibited good frictional toughness, effectively absorbing the relative displacement at contact interface, enabling CDGG to exhibit partial slip regime under higher loads and smaller displacement amplitudes.

Application of design of experiments for single-attribute optimization using response surface methodology for flow over non-linear curved stretching sheet

Optimizing the heat transmission rate of the flow through the statistically designed chain of experiments has major applications in product designing and improvising. Here, statistic design is framed by implementing response surface optimization methodology to contemplate the flow of dual non-Newtonian fluids allowed to flow over non-linear stretched geometry. The fluid flow model is designed under Cattaneo-Christov diffusion theory over a magnetized-radiative surface. The boundary condition is enriched with the slip regime and Newtonian heating. Numerical computations are acquired by employing the shooting technique approach in association with Runge-Kutta Fehlberg numerical scheme. Statistical and numerical consequences disclose that non-linear stretching index causes a depletion in velocity and temperature. When the Eckert number and the heat generating parameter are both large, the heat transfer rate is also large. Mass transport rate is lowest for higher ratios of diffusion coefficients. The 0.265365 is the maximum possible heat transport rate attained for the 8th experimental run with the key elements: Eckert number, heat source and radiation parameter. The critical point claimed by the Pareto chart shows that the slightest manipulation of the radiation parameter is critical for the heat transport rate, whereas the heat source parameter and Eckert number have almost similar influences on the response.

Investigating fretting wear mechanisms in Ti-6Al-4V: insights from residual stress and equivalent plastic strain analysis

Purpose The study delves into the influence of wear cycles on these parameters. The purpose of this paper is to identify characteristic patterns of σRS and εPEEQ that discern varying wear situations, thereby contributing to the enrichment of wear theory. Furthermore, the findings serve as a foundational basis for nondestructive and in situ wear detection methodologies, such as nonlinear ultrasonic detection, known for its sensitivity to σRS and εPEEQ. Design/methodology/approach This paper elucidates the wear mechanism through the lens of residual stress (σRS) and plastic deformation within distinct fretting regimes, using a two-dimensional cylindrical/flat contact model. It specifically explores the impact of the displacement amplitude and cycles on the distribution of residual stress and equivalent plastic strain (εPEEQ) in both gross slip regime and partial slip regimes. Findings Therefore, when surface observation of wear is challenging, detecting the σRS trend at the center/edge, region width and εPEEQ distribution, as well as the maximum σRS distribution along the depth, proves effective in distinguishing wear situations (partial or gross slip regimes). However, discerning wear situations based on εPEEQ along the depth direction remains challenging. Moreover, in the gross slip regime, using σRS distribution or εPEEQ along the width direction rather than the depth direction can effectively provide feedback on cycles and wear range. Originality/value This work introduces a novel perspective for investigating wear theory through the distribution of residual stress (σRS) and equivalent plastic strain (εPEEQ). It presents a feasible detection theory for wear situations using nondestructive and in situ methods, such as nonlinear ultrasonic detection, which is sensitive to σRS and εPEEQ. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2024-0005/

Fretting wear behavior and wear mechanism of selective laser melting IN738LC alloy with various loads and micro-structures

In this study, the ambient temperature fretting wear behavior and the wear mechanisms of the Selective Laser Melting prepared IN738LC alloy with various micro-structures were systematically investigated under varying load conditions (35 N, 100 N). The results indicate that the running states of fretting gradually transitions from the gross slip regime (GSR) to the mixed slip regime (MSR) as the load increases. The HT-2 samples (Unimodal precipitation, hardness 512 HV) present more fine homogeneous and dense secondary γ′ phase compared with HT-1 (Bimodal precipitation, hardness 487 HV) and As-built (No precipitation, hardness 392 HV) counterpart, which result in excellent wear resistance. The main fretting wear mechanisms for all samples were oxidation wear, abrasive wear, fatigue wear.