Friction最新文献

Rubber products used in shoe soles and tires need high friction, especially under lubrication, to ensure safety in daily life. The frictional behavior of rubber under lubrication is influenced by various parameters, including the properties of the rubber tread, lubricant, mating surface, and sliding conditions. The effects of these parameters on friction have been investigated, but the mechanisms for enhancing friction under lubrication have not been studied systematically. This review is a summary of the methods used to enhance rubber friction under lubrication, including optimizing the tread groove geometry to improve drainage, texturing to increase the contact area, preventing liquid from flowing into the contact interface, increasing hysteresis friction, and controlling the surface free energy of rubber to promote dewetting. Additionally, suction-based attachment is emphasized as an effective mechanism for liquid-covered surfaces. Integrating these approaches may significantly advance the design of high-friction rubber tread, enabling the development of materials that maintain high friction regardless of lubrication conditions.

During cardiovascular interventional surgeries, catheters come into mechanical contact with vascular tissues, resulting in friction, collisions, and compression that can damage the tissue. To address this, surface engineering is essential for modifying the catheter surface. Effective catheter coatings require high adhesion strength to prevent peeling or delamination from the inner surface, while the outer surface must provide excellent lubricity and biocompatibility. In this study, we use the layer-by-layer (LbL) technique to introduce catechol-modified chitosan (CC) and dopamine-modified oxidized hyaluronic acid (DOHA), forming a nanoscale, superhydrophilic, strongly adhesive, and biocompatible coating on cardiovascular catheters. Tight binding of CC and DOHA results from electrostatic interactions, chemical reactions, and catechol group enrichment, yielding an adhesion strength up to 1 MPa. These CC/DOHA multilayers greatly enhance the lubrication performance of the TPU substrate, reducing the coefficient of friction (COF) by up to 95% compared to the uncoated state. After a 30-minute friction test, the COF of the CC/DOHA₁₆ coating only slightly increased from 0.032 to 0.044, demonstrating excellent stability. Evaluations showed a reduction in vascular intima damage from grade 5 without coating to grade 3, confirming the coating's effectiveness in minimizing friction-induced damage.

Pitch deviation, a type of longwave deviation, has been demonstrated to be a significant contributor to noise generation in the drive trains of motor vehicles operating at relatively high speeds. To date, numerous studies have investigated the effects of pitch deviation on the dynamic characteristics of gear systems. However, these models often exhibit inconsistencies with real-world observations due to the simplification of the contact between teeth pairs. This simplification ignores clearance compensation and damping of the oil film. To fill this gap, a new numerical model of spur gear systems with pitch deviation considering lubrication is proposed. An analytical model of the time-varying mesh stiffness (TVMS) and meshing impact force for spur gear pairs is proposed, in which the geometric relationship and iterative solution process are investigated. An improved tribodynamic model is established to investigate the excitation behavior of gear pairs with pitch deviation under lubrication. The accuracy of the proposed model is verified through comparisons with references and experimental results. The results show that the random impact phenomenon of the TVMS is significantly suppressed by the oil film, and the meshing impact force is also reduced. The transmission stability of spur gear pairs with tooth pitch deviation is improved under lubrication. The research results provide theoretical support for accurately predicting the dynamic responses of spur gear pairs with different precision levels while considering lubrication.

Under special operation conditions such as the starting, stopping, and turning of marine engines, it is challenging to establish a stable water lubricating film for water-lubricated bearings. Lubrication failure leads to severe friction-induced vibration behaviours, which threatens the reliability of bearings and the stealthiness of ship. In this study, a novel vibration dissipation mode via the mechanical-electrical-thermal energy conversion pathway was applied for the design of water-lubricated bearing materials. The piezoelectric damping composites (PDCs) with different deformation responses were fabricated. Under water-lubricated conditions, M3055 had excellent tribological properties, including a low average friction coefficient (COF) of about 0.22 and a low wear rate of 0.0066 mm³/(N·h). Furthermore, M3055 demonstrated excellent vibration-noise attenuation with maximum vibration and noise amplitudes of 4.2 m/s² and 0.88 Pa, respectively. These results were attributed to the fact that M3055 provided suitable deformation resistance and optimal piezoelectric damping effect, and the mechanical energy (vibration) was successfully converted into Joule heat. The knowledge gained could not only contribute to a better understanding of PDCs but also provide a theoretical reference for the development of novel anti-wear and vibration-attenuated water-lubricated bearing polymers.

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.