Friction最新文献

Frictional contact between biological tissues is of critical importance in biomechanics and clinical treatment strategies, which is particularly relevant to diarthrodial joints, where articular cartilage surfaces undergo reciprocal contact loading for thousands of cycles per day. Taking the temporomandibular joint (TMJ) as an example, mandibular resection and reconstruction significantly alter the masticatory system and impact its biomechanical conditions. Clinical evidence indicates that pain is more frequent in the contralateral TMJ after this kind of surgery. However, there has been limited analysis of TMJ biomechanics following reconstructive surgery to date. Therefore, our study aimed to investigate the effects of masticatory muscle loss on stress distribution in the TMJs, determine an optimum loading region to mitigate excessive stress in the contralateral TMJ, and explore how the frictional change influences the biomechanics of the TMJ. The results demonstrate that the loss of masticatory muscles on the ipsilateral side due to resection can increase contact pressure in the contralateral TMJ and that incisor and ipsilateral dental implant occlusal loading generates the most desired stress patterns in the contralateral TMJ. This study reveals that the excessive contact pressure could increase the real contact area in the joint and further cause a transition from fluid film lubrication to solid contact, leading to increased friction and wear. This work sheds some light on asymmetric anatomy and frictional condition changes arising from surgery, which contribute to stress concentration in the contralateral TMJ and may be associated with degenerative changes. These findings hold significant clinical implications for selecting an optimal and patient-specific occlusal loading to mitigate excessive contact pressure and potential damage in the articular joint.

The energy crisis and environmental pollution are worsening. Therefore, water-based hydraulic fluids, i.e., aqueous ethylene-glycol-based, fire-retardant hydraulic fluid concentrates (HFCs), are becoming increasingly used. However, seawater intrusion inevitably occurs under marine conditions, generating hazards, such as corrosion and friction, within the hydraulic system components, pipelines, and materials. Moreover, HFCs have several drawbacks, including low viscosity, inadequate lubrication, and high corrosivity. Therefore, the tribological characteristics and corrosivity of HFCs must be improved and reduced, respectively. This can be achieved using additives. Herein, we summarize the fundamental characteristics of HFCs and their modifications for use in the marine environment, focusing on the optimal water–ethylene glycol proportion and its influence on the physicochemical, lubricating, and tribological properties of this HFC under varying conditions. We discuss the latest progress on the effect of seawater on the tribological corrosion of HFCs and the reduction of corrosivity in the presence of different additives. Finally, we highlight challenges and propose future research to improve performance in the marine environment.

This study conducted friction and wear tests on a TiAl alloy and a nickel-based powder metallurgy (P/M) superalloy. The test results were analyzed and compared to elucidate the friction and wear mechanisms of the two materials and to validate the proposed wear model. The findings indicate that high-hardness oxidized composite debris accumulates on the contact surface. In the early stage, ploughing predominates, leading to an accelerated wear rate. As friction progresses, the accumulation of debris and the formation of a hardened layer partially mitigate the wear rate. However, prolonged friction causes fragmentation of the debris layer, and the subsequent interaction between hardened debris and the surface promotes additional ploughing, thereby increasing the wear rate once more. This study developed an energy-based wear model that accounts for the observed reduction in the coefficient of friction (COF) with increasing normal load and sliding frequency. The discrepancy between the fitted and experimentally measured friction coefficients is within 20%. Simulations based on this model produced wear-depth predictions within a 5μm margin of error relative to experimental measurements, thereby demonstrating high predictive accuracy.

Microforming is a promising approach to micro-manufacture miniaturized components. The material flow and tribological aspects of microforming are affected by the size effect. The size effect phenomenon is influenced by parameters such as the initial microstructure, deformation temperature, lubricant type, and billet geometry downsizing. The scope of this article is to establish the tribology based scientific knowhow by considering all the mentioned parameters. As a case study to mimic the tribological interaction during microforming, a micro double cup extrusion (MDCE) test is performed on engineered Magnesium QE22 materials. The experiments were performed on various grain sizes, lubricants, and temperatures. The comprehensive investigation of all the conditions indicated that the UFG microstructure is the best-suited initial microstructural condition for maintaining excellent surface morphology, surface roughness, and microstructural homogeneity. The CG microstructure exhibited substandard surface properties and microstructural heterogeneity. EBSD microstructural analysis establishes tribological interactions with the activated micro mechanisms in all the CG, FG, and UFG conditions. In the CG condition, the activation of twin induced dynamic recrystallisation resulted in a greater cup height ratio and coefficient of friction.  This shows the incompetence of the CG microstructure in accommodating the friction-induced shear. On the other hand, the UFG microstructure condition demonstrated a resilient microstructure that accommodated the induced frictional shear with ease by activation of the grain boundary sliding (GBS) mechanism. The activation of the GBS mechanism resulted in complete anhelation of the frictional subsurface layer, thereby eliminating the tribological size effect that remained unaffected even when the billets were downsized.

In the current semiconductor manufacturing process, Chemical Mechanical Polishing (CMP) and post-CMP cleaning are critical steps. These processes require ensuring atomic-scale flatness and complete removal of contaminants. This review examines using Molecular Dynamics (MD) simulations to elucidate atomic-scale mechanisms underlying CMP and post-cleaning, focusing on four major MD methodologies: Classical MD, Reactive Force Field MD (ReaxFF), Tight-Binding Quantum Chemical MD (TB-QC MD), and Ab Initio MD (AIMD). Classical MD provides a foundation for simulating large-scale systems but lacks the accuracy for modeling chemical reactions. ReaxFF allows real-time bond breaking and formation simulations during CMP. TB-QC MD combines quantum accuracy with classical efficiency, enabling exploration of chemical reactions' effects on friction and material removal. AIMD directly calculates atomic interactions for precise depictions of chemical processes, although it is computationally expensive. MD simulations act as a "computational microscope," enhancing CMP and post-cleaning processes by quantifying interactions, material removal pathways, and contaminant desorption. Future research should address multi-scale modeling challenges, improve AIMD efficiency, and develop accurate potential functions to propel semiconductor manufacturing toward greater precision and efficiency.

Vascular interventional surgery is a minimally invasive treatment. It involves introducing catheters, guidewires, and other precision instruments into the human body to locally diagnose and treat internal diseases. However, mechanical contact, such as friction, compression, and collision, inevitably occurs during the intervention process. This can cause tissue damage. Currently, mechanical damage to vascular tissues is evaluated primarily in qualitative terms, which limits accurate reflection of both the extent of tissue damage and its influencing factors. This paper specifically researches friction injury between interventional catheters and vascular tissues. It develops the first quantification model of injury between catheters and blood vessels. Results showed that increases in normal force led to higher coefficients of friction (COF) and greater energy dissipation between the friction head and vascular tissue. In contrast, varying speeds produced a trend where COF and energy dissipation first increased, then decreased. A quantitative evaluation system for vascular tissue injury was established, based on indicators such as endothelial cells, glycoproteins, curled tissues, and intimal thickness on the vascular surface. Using this system, damage scores and damage grades were assigned to surface injuries in friction experiments. Pearson correlation analysis revealed a strong correlation between the COF and injury score. The link between normal load and sliding velocity was even higher than that between friction time and injury score. These experimental results lay the foundation for quantitative mechanical damage evaluation. They enable mapping of relations between mechanical factors and tissue damage.

Among the mechanical stimuli that arise in the tactile interaction between finger and surface during the tactile exploration, stimulating the mechanoreceptors, Friction-Induced Vibrations (FIV) play a fundamental role for discriminating the surface textures. Although it is well known that vibrational tactile stimuli strongly depend on the characteristics of the explored textures, the correlation between the different FIV features (such as amplitude and spectral distribution) with the texture perception and discrimination is still an open field of research. A vibrotactile rendering device has been here used to replicate the FIV measured when exploring isotropic textures. A sensory campaign has been conducted on 10 participants to investigate their ability to discriminate real and rendered isotropic textures, while the reproduced FIV have been manipulated and altered to mislead tactile perception. By swapping the FIV amplitudes measured from real textures, it has been observed that the participants discriminated the samples consistently with the vibration amplitude. The campaign has allowed to correlate the FIV amplitude and their frequency distribution with the perceptual results of the discrimination campaigns on real and mimicked textures.

Self-lubricating fabric composites significantly enhance the tribological performance of joint bearings by minimizing friction and wear on both inner and outer rings, thereby substantially extending their operational lifespan. These characteristics make them excellent candidates for bearing liner materials. However, conventional PTFE/Nomex phenolic-based fabric composites exhibit limitations in high-temperature environments, necessitating the development of more thermally stable alternatives. To address this challenge, this study introduced a novel PBO/PTFE polyimide (PI)-based self-lubricating fabric composite and proposed a PBO/PTFE-PI@M50 tribo-pair system suitable for high-temperature working conditions, utilizing M50 bearing steel as the counterpart material. Compared to Nomex fiber-reinforced self-lubricating fabric composites, PBO/PTFE-40PI (fabric composites with resin mass fraction of 40%) demonstrated significantly superior high-strength and high-temperature tribological performance. Notably, even at 300℃, it maintained an elastic modulus of approximately 15 GPa and a tensile strength of around 335 MPa, while achieving a low friction coefficient of 0.023 and an impressively low wear rate of 0.83×10^-6mm³/(N·m). The superior properties of PBO/PTFE-PI@M50 tribo-pair system stemmed from the composite's exceptional heat resistance and mechanical stability at high temperatures. Under the combined effects of the 'thermal-mechanical-chemical' interactions, the fiber-reinforced composite material formed a dense, uniform, and strongly stable transfer film on the surface of the M50 steel ring. Detailed analysis revealed that the film's stability primarily arose from the viscoelastic transition of PI and PTFE under high temperature, coupled with their strong tribo-chemical reactions with the steel ring. Given its outstanding performance, the PBO/PTFE-PI@M50 tribo-pair system holds considerable promise for advanced engineering applications.

The poor wear performance and susceptibility to pitting corrosion of titanium alloys in practical applications have attracted increasing attention. Layered double hydroxides (LDH) coatings, with two-dimensional structure, have shown great potential in protecting metals from corrosion and wear. However, the dense oxide layer on titanium alloys has hindered the development of LDH on these materials. In this study, a ZnAl LDH coating was fabricated on the surface of TC4 alloy via an in situ growth method. Molybdic acid anions were subsequently incorporated into the LDH interlayer through an ion exchange process. Inspired by biomimetic principles, a UV-grafted PDMS-infused slippery surface was prepared based on the nanoporous structure of ZnAl LDH, resulting in a protective surface with excellent hydrophobicity, corrosion resistance, and wear resistance. The anti-corrosion performance of the surface was evaluated using Tafel polarization and electrochemical impedance spectroscopy (EIS). The results demonstrated excellent corrosion protection for the TC4 substrate, as indicated by a low corrosion current density of 2.34 × 10^-7 A/cm². Compared with the bare TC4 alloy, the modified surface exhibited improved improved wear performance, owing to the infused silicone oil and ZnAl LDH nanosheets. This work not only provides valuable insights into the controllable in situ fabrication of LDH coatings but also offers a new strategy for the broader application of TC4 alloys and further research in the field of metal protection.

Gearbox efficiency is essential for the range of new energy vehicles. Most of energy in gearbox is consumed on the load-independent factor, e.g., churning loss, which however, has not been deeply addressed. In this study, load-independent losses are inhibited by oleophobic treatment to the surfaces of a transmission component. A polytetrafluoroethylene (PTFE) coating is prepared by electroless chemical plating. The contact angle (CA) and surface morphology of the coated surfaces are tested to elucidate the loss inhibition mechanism on the oleophobic interface. A visualized test rig for measuring the churning oil flow is built with the function of temperature control at a range of -30℃-80℃. Moving Particle Semi-implicit (MPS) method is used to further investigate the mechanism of oleophobic surface regulation. The oil velocity and pressure distributions, the slip characteristics and flow field around the coated surface are investigated. An analytical flow model is established to demonstrate the flow structure and to quantify the relationship with oil properties and surface characteristics. The results showed that the CA increased from 7.8° to 31.2° when the surface is coated by PTFE. The average reduction of the churning torque test values ranged from 20% to 36% across a wide temperature range of -30℃ to 80℃, with a maximum of 50.7% at 40℃. Simulated slip lengths ranged from 2.9 μm to 16.0 μm at different rotational velocities. The coating reduced the oil velocity and pressure, as well as the viscous shear and differential pressure resistance on the surface of the rotating component. This study thus provides scientific support for the efficiency improvement of gearboxes used in complex engineering.