Ring Friction Research Articles

Structural Optimization Analysis of Combined Sealing Ring

Abstract In this paper, the effect of the contact forces of the combined sealing ring by the pre-compressibility of the O-ring seal and the working pressure is studied. The influence of the structural parameters (width, thickness and chamfer) of the friction ring on the contact forces of the combined sealing ring is analyzed. The results show that, in the combined seal, it is not that the higher the pre-compressibility, the higher the sealing efficiency. Under certain working conditions, the chamfer of the friction ring increases, the contact forces of the friction ring decreases; the thickness of the friction ring increases, the contact forces of the friction ring is almost unchanged; The contact force increases with the increase of the width of the friction ring. Under the condition of a given medium pressure of 25 MPa and a compressibility of 22.5%, the optimal values of friction rings L, R, and H and three contact forces and contact forces F under the corresponding conditions are calculated by the optimization algorithm.

Research on the Friction Force Characteristics for the Double O-ring Seal of the Cylinder under the Small Displacement Condition

In order to obtain a high-precision pneumatic control system, it is necessary to study the friction force of the cylinder. However, few have considered the cylinder's frictional characteristics at small-displacements. This study investigated the influence of different conditions on the cylinder friction characteristics during the process from static to small-displacement of pneumatic double O-ring seal. A set of experimental apparatuses controlled by an electric actuator perform a seal ring small-displacement friction test to achieve the goals. The working principle of sealing rings in different deformation stages is expounded. According to experiments, the sealing ring's friction force in small-displacement movement can be separated into tilt, elastic deformation, pre-sliding, and sliding friction stages. Furthermore, the clearance characteristics between the sealing ring and the piston groove are verified, which decreases with the sealing ring thickness. Finally, the friction displacement characteristics of sealing rings under different pressures and materials during the elastic deformation stage were verified. It can be concluded that when the displacement is between 0.05-0.25mm, the friction of the sealing ring is almost linear with the displacement; when the displacement reaches 0.25mm, with the increase of the displacement, the friction force changes in a similar parabola manner. This study provides a detailed analysis of the friction characteristics of the seal in different stages of small displacement, which plays an important reference role in overcoming cylinder friction and promotes the development of pneumatic systems in the field of accurate position and speed control.

Analysis of friction vibration characteristics of the end face of a T-slot sealing ring under thermal deformation

Aiming at the friction vibration problem caused by dry friction contact during the start-stop process of a dry gas sealing device, this paper takes the end face of a T-slot dry gas sealing ring as the research object and establishes a numerical calculation model of the end face of the T-slot sealing ring. The thermal coupling method is used to obtain the thermal deformation law of the seal ring end face. The transient dynamics analysis method was applied to study the frequency and vibration mode of the friction vibration instability of the seal ring end face under thermal deformation. A vibration test bench was set up for the friction ring, and the friction vibration signals of the test pieces were collected, and the characteristic frequencies were extracted. The results show that: After thermal deformation, the end face of the sealing ring changes from a parallel surface to an inward converging surface, and the friction system of the sealing ring will become unstable. When considering the influence of thermal deformation, there are more unstable frequencies and lower frequency values that are most prone to frictional vibration. As the thermal deformation of the sealing ring increases, the frictional vibration becomes greater. In areas where the characteristic frequency values of frictional vibration are concentrated during thermal deformation, the occurrence rate of frictional vibration noise is higher.

Analysis of Friction and Wear Properties of Friction Ring Materials for Friction Rings under Mixed Lubrication

Aiming at the problem of mechanical seal failure due to serious wear and tear in operation, the numerical model of the thermal–solid coupling wear of the seal ring is established by taking the friction sub-material as the research object, and the hardness, wear coefficient, and friction coefficient of different soft-ring materials are obtained by a test to verify the accuracy of the numerical model of wear. Additionally, the temperature field and deformation field of the seal ring of different materials are calculated, and the effects of the material parameters, such as elasticity modulus and thermal conductivity, on the temperature, relative deformation, and axial deformation trend are reported. The wear relation of the mechanical seal was optimized, and the correction coefficients of several materials were calculated. The results show the following: the main wear of the seal ring is due to adhesive wear leading to particle shedding and extrusion, adhesive wear causes material transfer, which alters the composition of the worn surface.in turn leading to cratering, which also causes the wear of the seal ring; the friction performance is better when the soft-ring material is graphite (C); the temperature, as well as the deformation, is smaller when the soft-ring material is silicon carbide (SIC); the correction coefficients for the life of SIC are calculated to be 0.23, for C, to be 0.14, and for stainless steel (Ss), to be 0.31, and the corrected equations can more accurately predict the corresponding material. The corrected equation can more accurately predict the service life of the corresponding material.

Process optimization and tribological behavior of Ti-48Al-2Cr-2Nb prepared by selective electron beam melting

Selective electron beam melting (SEBM) technology was utilized to fabricate TiAl alloys which possess low density and excellent high-temperature performance, to achieve lightweight design of automotive engines. The forming process of Ti-48Al-2Cr-2Nb was systematically optimized, and found that the microstructure of TiAl formed by SEBM consisted of a layer of alternating γ-band structure and duplex-like structure. As the energy density increases, grain coarsening, proportion increasing of high angle grain boundaries, and anisotropy strengthening occur successively. The forming quality of TiAl reaches its peak at an energy density of 22.5 J/mm3, at which point its mechanical properties and wear resistance also perform the best. Subsequently, in-depth friction experiments at high and room temperatures were conducted, and it was found that at room temperature, as the load increased, the friction coefficient of the samples decreased and the wear rate increased. In addition, the friction coefficient decreases from 0.54 to 0.44, while the wear rate increases from 19.90×10−5 mm3/(N·m) to 25.97×10−5 mm3/(N·m). At this point, abrasive and adhesive wear were the main wear mechanism. Under high temperature conditions, the wear mechanism of the substrate is mainly abrasive wear, adhesive wear, and oxidative wear. And the friction coefficient decreases from 0.69 to 0.49. At lower temperatures, the detached debris was filled and solidified on the wear marks under the action of the friction ring, forming a hardened layer called “enamel”, which can alleviate the negative effects of wear. Under the influence of extreme high temperature environment, the unworn surface forms a light blue oxide film due to rapid oxidation, known as the “burning blue” phenomenon. Along with the high-temperature oxidation phenomenon confirmed by EDS, the oxide layer is more prone to peeling off and forming debris. In addition, melting softening occurs inside the annular wear scar, which increases the amount of deformation under external force, ultimately leading to a significant increase in wear.

A Comparative Analysis of Friction and Energy Losses in Hydrogen and CNG Fueled Engines: Implications on the Top Compression Ring Design Using Steel, Cast Iron, and Silicon Nitride Materials.

Optimizing the design of the top compression ring holds immense importance in reducing friction across both traditional Internal Combustion (IC) engines and hybrid power systems. This study investigates the impact of alternative fuels, specifically hydrogen and CNG, on the behavior of top piston rings within internal combustion (IC) engines. The goal of this approach is to understand the complex interplay between blow-by, fuel type, material behavior, and their effects on ring friction, energy losses, and resulting ring strength. Two types of IC engines were analyzed, taking into account flow conditions derived from in-cylinder pressures and piston geometry. Following ISO 6622-2:2013 guidelines, thick top compression rings made from varying materials (steel, cast iron, and silicon nitride) were investigated and compared. Through a quasi-static ring model within Computational Fluid Dynamics (CFD), critical tribological parameters such as the minimum film and ring friction were simulated, revealing that lighter hydrogen-powered engines with higher combustion pressures could potentially experience approximately 34.7% greater power losses compared to their heavier CNG counterparts. By delving into the interaction among the fuel delivery system, gas blow-by, and material properties, this study unveils valuable insights into the tribological and structural behavior of the top piston ring conjunction. Notably, the silicon nitride material demonstrates promising strength improvements, while the adoption of Direct Injection (DI) is associated with approximately 10.1% higher energy losses compared to PFI. Such findings carry significant implications for enhancing engine efficiency and promoting sustainable energy utilization.

Study of in vitro wear resistance and degradation properties of self-made treated medical magnesium alloys

Study of <i>in vitro</i> wear resistance and degradation properties of self-made treated medical magnesium alloys

ANALYSIS OF UNCONTROLLED WEAR IN THE AREA OFA BELLEVILLE SPRING OF A FRICTION TORSIONAL VIBRATIONDAMPER IN A MOTOR VEHICLE CLUTCH

The article describes the problem of excessive tribological wear of a torsional vibration damper built intoa single-disc friction clutch of a truck vehicle. In contrast to the controlled, design-based wear of damper’sfriction rings, i.e., wear whose kinetics are known and predictable, uncontrolled wear at Belleville springcontact surfaces effects in a premature decrease in the damper’s friction torque and, consequently, loss ofdurability. As a result of the analyses and experimental work, the causes of accelerated wear were identified.Sets of springs and friction rings from the 10 used vibration dampers that worked under similar operatingconditions but with different operating periods were used as the basic research material. The influence ofabrasive wear of Belleville springs on their load-deflection characteristic was identified. A comparativeanalysis of the characteristics of the new spring and the used springs is also presented to illustrate changes inthe axial load in the assemblies of the analyzed dampers.

Influence of Liner Surface with Parameterized Pit Texture on the Friction Characteristics of Piston Rings

The arrangement of a pit-shaped surface texture on the surface of a cylinder liner significantly affects reductions in piston ring friction, and the influence of the structural parameters and spatial distribution on piston ring friction power consumption is unclear. In this paper, the diameter, depth, axial spacing distance, and radial spacing distance of the pits on the inner surface of a cylinder liner were used as variable parameters to process the surface textures of different schemes, and then a friction and wear test was carried out on UMT piston ring–cylinder liner specimens, several texture schemes with the best anti-friction effect were selected, an engine bench test was carried out by comparing these texture schemes with non-texture schemes, and the frictional torque and fuel consumption of the engine were studied at different oil temperatures. The results show that the depth of the pits in the surface texture of a cylinder liner has a greater influence on the friction reduction effect, followed by the radius. The higher the oil temperature in the engine bench test, the greater the impact of the surface texture. The reduction in fuel consumption was greater in the lower-speed region after structuring the textured cylinder liner compared to the non-textured cylinder liner. Specifically, the friction coefficient was mainly affected by the depth of the pits, and the depths of the pits in the texture schemes with good friction reduction effect were all 17–19 μm. The best friction reduction could be achieved when the pit radius is around 50 μm, with little difference in pit depth. When the oil temperature was 95 °C, the average drag torque reduction was about 1.69 Nm; when the oil temperature was 105 °C, the decrease was about 2.54 Nm; and when the oil temperature was 105 °C, the decrease was about 4.53 Nm. After adding the surface texture of the cylinder liner, the fuel consumption rate of the engine equipped with the structured cylinder liner was generally reduced compared with that of the original cylinder liner engine. Among them, the average and subsequent consumption rate of surface assembly scheme 11 decreased the most, with a value of 1.3 g/kwh.

Effects of fuel composite additives on the vibration, wear and emission performances of diesel engines under hot engine tests

Diesel engines applied for ships are currently facing an escalating demand for energy conservation and emission reduction, which has driven the application of fuel composite additives. Nevertheless, adverse phenomena affecting engine reliability have been observed in practical engine applications with unclear mechanisms. The present study investigated the vibration, wear, and emission performances of three types of composite additives with detergent and synergist function in a diesel engine. Vibration acceleration, cylinder temperature, NOx emission quantity, as well as the wear characteristics of cylinder liner-piston ring (CLPR) friction pairs were selected as characterization parameters. The results revealed that components of additives have a certain impact on vibration, wear, combustion, and emission performance. Specifically, additives of Type Ⅰ containing aviation kerosene and Type Ⅱ containing 2-Ethyl 1-hexanol and 2-Ethylhexyl nitrate compound in diesel were susceptible to cause aggravated engine vibration and thus lead to excessive wear. Furthermore, Type I exacerbates the thermal stress and worsens combustion stability, resulting in increased mechanical vibrations, cylinder temperature, and NOx emission. In contrast, addition of Type Ⅲ containing 2-nitro-propane and toluene results in improved reliability, demonstrating a 7.6% reduction in mechanical vibration energy and a 27.4% decrease in wear mass losses of piston rings, while effectively mitigating abnormal wear on the liner surface. Likewise, it also it also facilitates a mild combustion process and achieves better emission reduction results by reducing the NOx emission by 11.5% while slightly lowering the cylinder temperature by 0.74%.

Insights Into Frictional Brush Seal Hysteresis

Abstract Brush seals offer a superior sealing effectiveness compared to labyrinth seals. However, widespread use of brush seals is constrained by deleterious behaviors such as pressure-stiffening and hysteresis. For the latter, the bristles bend during the shaft incursion process and do not fully recover during the shaft retraction process. An opening gap is created, which increases seal leakage unless the pressure load drops to a certain level. In this work, analytical and numerical models based on a single bristle are proposed to capture the seal's response to shaft displacement with and without pressure loading. The models are validated using static stiffness tests at an unpressurized condition from literature. The main results show that modeling of the backing ring friction is essential to capture the bristle hang-up behavior. Shaft friction dominates at unpressurized conditions, while backing ring friction dominates at high pressure loading. An expression for shaft hang-up displacement has been derived. A sensitivity study shows that seals with shallow lay angle, short bristle length, and large bristle diameter are less prone to hang-up problems. The models developed in the present framework have been shown to qualitatively capture the pressure stiffening, hysteresis, bristle hang-up, and shaft rotation effects.

Synergistic effects of graphene additives and piston ring surface treatment on friction properties of engine oil

The use of nano-additives improves the performance of lubricants by minimizing energy loss due to friction and wear. In this study, tribological properties of cylinder liner-piston ring were improved by modifying monolayer graphene with surfactants. Additionally, surface chemical chromium coating and chemical heat treatment were conducted on the friction surfaces of specially made piston ring samples to further enhance the friction of piston ring. From the comparison of experimental results, the best lubrication performance was exhibited by the use of 0.05 wt% modified graphene nano-lubricant, which reduced the friction coefficient by approximately 31.1% and improved the anti-wear performance by approximately 59.6% compared to the base oil. In addition, the effect of the graphene nano-lubricant on the friction performance of chromium-coated samples was more substantial than that of the chemically heat-treated samples. Under high-temperature and heavy-load conditions, the corresponding friction coefficient was reduced by 15.5% and 34%, respectively, when compared to the base oils. This can be attributed to the porous surface of the chromium-coated sample, which promotes the storage of the graphene nano-lubricant. The results highlight the synergistic effect of graphene additives and piston ring surface treatment on the tribological performance.

Limit analysis of multi-ring masonry arches: a parametric study on the effects of friction angle, geometry, interlocking, and ring number

The majority of built heritage covering large spans are built with curved masonry components, such as multi-ring arches, to attain greater overall thickness. Their ultimate structural capacity when subjected to external loads is significantly influenced by the various construction techniques utilized. Such structures are made up of independent rings that communicate with one another through interface contacts, and the geometrical features, like size, orientation, and the arrangement of units, play a significant role, as do the mechanical characteristics, like friction. Multi-ring arches subjected to a vertical load at quarter span are assessed utilizing an in-house code implementing the upper bound approach of the limit analysis for masonry structures. The formulation of a script for geometry generation has been given and used for the input to the code. A discrete model has been adopted accounting for a combination of size and disposition of blocks, friction angle, number of rings and the span length are taken into account. Following their combination of impacts in terms of collapse multipliers, which are classified as per respective influencing parameters, each one’s importance was demonstrated by classifying them into two major groups as per unit size. The outcomes showed that all the parameters were key influencing factors in the performance of such structures. Using relatively larger units enhanced the impact of interlocking and provided larger collapse multipliers. While interlocking played a more significant role when span was considered, it together with friction had a larger impact when ring number was varied, such that better interlocking and larger friction values provided higher collapse multipliers.

Bionic Design and Optimization of the Wear-Resistant Structure of Piston Rings in Internal Combustion Engines

Internal combustion engines, during their operation, subject the piston to high-temperature and high-pressure conditions, requiring it to endure intense, continuous reciprocating motion. This strenuous process leads to significant wear and tear. Among the engine’s crucial components, the piston ring plays a pivotal role but is particularly susceptible to wear. Therefore, extensive research has been devoted to investigating the wear of piston rings, a critical sealing component within internal combustion engines. To address the high cost of existing coating methods, which hinders widespread application, we propose a bionic design approach inspired by groove structures observed on earthworm bodies, aimed at enhancing the wear resistance of piston rings. Bionic piston rings featuring optimally designed groove structures inspired by the earthworm’s anatomy were designed. These rings exhibited varying groove depths (1 mm, 2 mm, and 3 mm), groove widths (0.1 mm, 0.3 mm, and 0.5 mm), and groove spacings (0.1 mm, 0.2 mm, and 0.3 mm). We conducted thermal–structural coupling analyses on both standard piston rings and these bionic counterparts. The results revealed that the maximum stress was concentrated at the first piston ring, precisely at the opposing region of the end gap. Thus, the initial piston ring endured the primary frictional losses. Moreover, a comparison of stress levels between bionic rings and the standard ring revealed that the bionic groove structure substantially reduced stress and minimized stress concentration, thus enhancing wear resistance. Groove width had the most notable influence on wear performance, followed by groove depth and groove spacing. Optimal wear resistance was achieved when the groove depth was 3 mm, groove width was 0.1 mm, and groove spacing was 0.1 mm. Subsequently, we constructed a piston ring friction test bench to validate the wear resistance of the most effective piston ring. The results indicated that the wear resistance of the bionic piston ring exceeded that of the standard piston ring by up to 19.627%. Therefore, incorporating a bionic groove structure within the piston ring can effectively reduce surface friction and enhance wear resistance. This, in turn, can enhance the operational lifespan of internal combustion engines under favorable working conditions.

A Comparison of Hydrogen and Gasoline Piston Ring Simulations

This paper presents a transient mixed-lubrication hydrodynamic and gas flow simulation model for a piston ring pack for a four-stroke internal combustion engine. The analyses carried out compare two fuel types, hydrogen and gasoline, at a 2000 rpm low engine load (20%), as well as 3000 rpm low (20%) and high (100%) engine loads, to investigate the effects of the different fuels and loading conditions on the ring pack. In particular, the minimum oil film thickness at the top compression ring, the total ring friction of the ring pack, the friction power loss and the blow-by are studied. The simulation shows that, under the high load conditions at 3000 rpm, the hydrogen variant exhibits larger friction power losses, around a 200 W peak difference and larger blow-by throughout the expansion stroke of the engine cycle. A similar trend can be observed for the low loads, where larger friction power losses with peak differences of 30 W and 40 W for 2000 rpm and 3000 rpm, respectively, are observed. The blow-by results for the low load at 2000 rpm show a slight increase of approximately 22% more gas flow into the crankcase, while the 3000 rpm simulation shows a 50% increase in blow-by for the hydrogen variant at low load and a 40% increase at high load. The findings that are presented indicate that, although alternative fuel sources such as hydrogen are very attractive alternatives to fossil fuels such as gasoline, there can be unwanted side effects that could lead to the permanent damage of components through quicker wear or hydrogen embrittlement from the blow-by gas.

Fusion of Multi-scale Features Seal End Face Fluid Characterization

The composite weaving of dynamic and static ring friction end faces with multi-scale features can improve the sealing performance of mechanical seals, but there is no clear mechanism of weaving action, and it is difficult to optimize seal surface weaving. In this study, a mathematical model is developed to analyze the fluid sealing performance of the composite textured mechanical seal end face with a combination of a 5-sided micro-pit and T-slot according to the mass conservation cavitation boundary condition. The change in sealing performance between the composite texture and single texture in terms of opening force and leakage volume was investigated. Numerical analysis shows that compared with a single texture, the multi-scale texture end face creates a coupling effect between the micro-pit and T-slot, which has a stronger dynamic pressure lubrication effect and improves the sealing performance of the sealing sub-seal with increased pressure. The research results can be applied to the design optimization of mechanical seal surface textures.

Development of a New Measurement System for Piston Ring Friction Based on the Floating Liner Method

Development of a New Measurement System for Piston Ring Friction Based on the Floating Liner Method

Synergistic effects of carbon fiber and polytetrafluoroethylene on the friction and wear behavior of polyarylene ether nitrile under dry lubrication condition

AbstractThe synergistic effects of carbon fiber (CF) and polytetrafluoroethylene (PTFE) on the friction and wear behavior of polyarylene ether nitrile (PEN) under dry lubrication condition were studied. According to the scanning electron microscopy (SEM) on the composites' surface after wear, the wear mechanism of the composites under dry sliding condition was analyzed. The research results show that the addition of solid lubricants PTFE and carbon fibers to PEN helps to enhance the properties of friction and wear. The specific wear rate is decreased to 5.7 × 10−7 mm3/N m at a PTFE composition of 5 wt%, which is optimized by 33.4% more than PEN/CF composites. In addition, wear mechanisms are mainly abrasive wear, accompanied by adhesive wear and plowing of the friction ring.

Positive Effect of Periodic Micropatterns on Compression Ring Friction

Internal combustion engines are increasingly regulated in regard to efficiency and environmental impact, which requires advanced optimization strategies of engine components. The contact between the top ring and the cylinder liner is critical to the efficiency of an internal combustion engine. As shown in a previous study, an amorphous carbon coating can greatly improve the friction properties of piston rings. This work expands on these results by fabricating laser‐interference‐induced microchannels on the coating perpendicular to the direction of movement with a mean depth of 0.97 and 3.13 μm spatial period to further optimize the tribology. Fired single‐cylinder engine measurements of the microtextured rings show a significant reduction in mean piston assembly friction of 5% for operation points that are relevant for urban transportation and up to 10% for specific operation points. Subsequent multibody elastohydrodynamic simulations prove that measured friction changes result from the compression ring microtexture. In particular, the microtexture increases the hydrodynamic pressure, reduces hydrodynamic losses, and leads to 20% lowered compression ring losses for an entire combustion cycle of the investigated operation point. In the future, such tribological concepts can be deployed in internal combustion engines that are powered by sustainable hydrogen or methanol.

Influence of thermal effect in piston skirt lubrication considering thermal deformation of piston and cylinder liner

With the development of high-strength marine diesel engines, piston skirt lubrication plays an increasingly important role. In this study, to ensure that the mixed lubrication can be applied, the contact of the PS corner and CL is simplified to a spring–damper system. A coupled dynamical–tribological numerical model of a piston skirt is proposed by combining mixed lubrication and the secondary motion of the piston. The model is then used to study how the thermal effect of the piston skirt-cylinder liner friction pair affects (i) the secondary motion of the piston, (ii) the contact force of the piston-skirt corner points, and (iii) the lubrication characteristics, while considering ring friction, friction moment of piston pin and three-dimensional thermal deformation of the piston and cylinder liner. The results show that the secondary motion under the thermal condition is less than that under the cold condition, and the reverse rotation of the piston under the thermal condition occurs earlier. Asperity contact and corner points contact appear under the thermal condition, and the friction mean effective pressure under the cold condition is 47.7% greater than that under the thermal condition. Overall, it is necessary to consider the thermal effect of the piston skirt-cylinder liner friction pair.