Tribological Effects Research Articles

Tribological effects of micromilling of hardened AISI D2 steel on tool wear and top burr formation

Tribological effects of micromilling of hardened AISI D2 steel on tool wear and top burr formation

EVALUATION OF THE EFFECTS OF ZDDP AND GRAPHENEADDITIVES IN PAO 8 OIL ON THE TRIBOLOGICAL PROPERTIESOF TIALN COATING

This paper investigates the tribological effects of graphene and anti-wear zinc dialkyl dithiophosphates(ZDDP). Friction tests have been carried out on a tribological tester which operates as a ball and disc assemblyin a frictional, sliding motion. Tests were carried out with a load of 10 N over a sliding distance of 1000 m.TiAlN coated HS6-5-2C steel discs, and 100Cr6 steel balls were used in the tests. Tests were conducted underlubrication conditions with poly()olefin oil PAO 8 with graphene and/or ZDDP. The chemical compositionof the TiAlN coating was studied using a scanning electron microscope, and the wear marks on the discs andballs were observed. The geometric structure of the samples was analysed before and after the friction testsusing a confocal microscope with interferometric mode. The results indicated that the addition of ZDDP andgraphene to the poly()olefin oil had an effect on reducing the friction coefficient.

Numerical identification of position-dependent friction coefficients from measured displacement data in a bolt-nut connection

Friction is a complex system affected by microscopical effects and multidisciplinary phenomena. Coulomb's simple friction model with a constant friction coefficient cannot account for all these tribological effects. Nevertheless, this model is still widely utilised for calculations of mechanical applications. In order to reflect the importance of friction as a parameter for functionality, we need more realistic and sophisticated calculations. This is particularly relevant for bolt-nut connections, which serve as motivating example for our study. Our approach is to introduce position-dependent friction coefficients by dividing the contact surface into different friction areas, each characterised by a constant friction coefficient. These coefficients are then adapted to measured displacement data. To this end, we develop a numerical parameter identification tool. The tool combines calculations in Ansys Mechanical, an established Finite Element software, and Microsoft's Visual Basics for Applications for optimisation purposes. We verify the parameter identification tool using the simple model of a block on a planar surface. Within this test scenario, the algorithm converges and provides a good approximation of the friction coefficients. Subsequently, we apply parameter identification to the model of a bolt-nut connection. We perform optical measurements to acquire experimental displacement data. The parameter identification tool demonstrates its functionality. Finally, we discuss future modifications of the procedure, that will enable more realistic and reliable results.

Combining multi-scale surface texturing and DLC coatings for improved tribological performance of 3D printed polymers

Polymer components fabricated by additive manufacturing typically show only moderate strength and low temperature stability, possibly leading to severe wear and short lifetimes especially under dry tribological sliding. To tackle these shortcomings, we investigated the combination of single- and multi-scale textures directly fabricated by digital light processing with amorphous diamond-like carbon (DLC) coatings. The topography of the samples and conformity of the coatings on the textures are assessed and their tribological behaviour under dry conditions is studied. We demonstrate that the surface textures have a detrimental tribological effect on the uncoated samples. This changes with the application of DLC coatings since friction substantially reduces and wear of the textures is not observed anymore. These trends are attributed to the protection of the underlying polymer substrate by the coatings and a reduced contact area. The best tribological performance is found for a coating with highest hardness and hardness-to-elasticity ratios. Moreover, multi-scale textures perform slightly better than single-scale textures due to a smaller real contact area. Summarizing, we verified that the high flexibility and low production costs of 3D printing combined with the excellent mechanical and tribological properties of DLC results in synergistic effects with an excellent performance under dry sliding conditions.

Tribological Effects of Metalworking Fluids in Cutting Processes

An understanding of the proper application of metalworking fluids (MWFs) is necessary for their implementation in efficient production processes. In addition, the knowledge of the process-related aspect of chip transport and the macroscopic cooling effect, the characteristics and properties of lubricant film formation, and the cooling conditions in the secondary shear zone on the chip surface, i.e., in the direct vicinity of the material separation, represent a combined fundamental scientific issue within production engineering. The aim is to transfer methods from the field of tribology of machine elements, which have already led to a considerable gain in knowledge in this discipline, to machining and to couple them with already established approaches to machining. In the case of roller bearings, the contact pressure is in the range as the pressure in the contact zone between the cutting insert and chip. Due to this, established methods might be transferred to the cutting process. In addition to classical pin-on-plate and pin-on-ring friction investigations, film thickness measurements were carried out and compared to machining tests. The coefficient of friction determined in the planing test rig is 0.48 for dry cutting, while it is 0.47 for wet cutting. These two values are much larger than the CoF with MWFs measured on the two tribometers. It is shown that the boundary friction of MWF especially influences the machining process. Thus, additives in MWF might have a high significance in machining.

Tribology of Pore-Textured Hard Surfaces under Physiological Conditions: Effects of Texture Scales.

Micro- and nanotexturing on hard biomaterials have shown advantages for tissue engineering and antifouling applications. However, a growing number of studies have also shown that texturing may cause an increase in friction, demanding further research on the tribological effects of texturing under physiological conditions. This study investigates the tribological effects of micro- and nanopore patterns on hard hydrophilic silicon sliding against soft hydrophobic polydimethylsiloxane (PDMS) immersed in aqueous liquids with various viscosities, simulating the sliding of a textured implant surface against soft tissues. The experimental results show that silicon surfaces with pore textures at both micro- and nanoscale feature sizes confer a higher coefficient of friction (COF) than an untextured one. It is attributed to the texture's edge effect caused by the periodic pore patterns between the two sliding objects with a large difference in material stiffness. For the same solid area fraction, nanopored surfaces show a higher COF than micropored surfaces because of the significantly higher texture edge length per unit area. For micropored surfaces with a similar length of texture edge length per unit area, the COF increases more significantly with the increase in pore size because of the greater stress at the rims of the larger pores. The COFs of both micro- and nanoscale pores generally decrease from ∼10 to 0.1 with an increase in the surrounding aqueous viscosity, indicating the transition from a boundary lubrication to a mixed lubrication regime while mostly remaining in boundary lubrication. In contrast, the COF of an untextured surface decreases from ∼1 to 0.01, indicating that it mostly remains in the mixed lubrication regime while showing the tendency toward hydrodynamic lubrication. Compared to a hydrophilic hard probe sliding against a textured hydrophobic soft substrate, the hydrophobic soft probe sliding against a textured hydrophilic hard substrate produces a significantly higher COF under similar physiological conditions due to the larger edge effect.

Tribological effects of boriding treatment on a low carbon steel repaired by wire and arc additive manufacturing

Recently, electric arc-based welding processes have gained significant attention in the manufacturing sector due to their usefulness for repairing or remanufacturing damaged mechanical components. The changes in microstructure and mechanical properties of materials and components repaired by electric arc-based welding techniques have been the focus of most of current research. Since most of components are damaged by wear during operation, the improvement of such repaired/welded materials or components in terms of tribological properties for each specific application is wanted. In this work, the effects of applying a thermochemical treatment (boriding) as a tribological booster on a low carbon steel repaired by arc welding were studied. The tribological behavior (coefficient of friction (CoF) and wear volume) of the repaired steel before and after being borided was evaluated by means of micro-abrasion tests to replicate three-body abrasion under muddy environments. In addition, the physical and mechanical characteristics of the boride coating in both the original material and the repaired zone were evaluated by optical microscopy, X-ray diffraction, instrumented hardness tests and the VDI adhesion test. The wear scars were analyzed by scanning electron microscopy (SEM) and non-contact profilometry to identify the resulting wear mechanisms and to measure wear scars, respectively. The results showed that boriding treatment was effective to increase the hardness and wear resistance of the repaired low carbon steel without creating gradients of hardness, CoF, wear resistance or adhesion strength between the surface of the original material and the repaired zone.

Investigation of tribological and metallurgical effects on Ti–6Al–4V laminates made by LSEM for Ti/GFRP stacked composite

Laminates of Titanium alloys find their wide application as input material for stacked composites used in different industries. Presently, the laminates are made by rolling, but the multistage deformation of the process makes it energy-intensive process. The present investigation aims to check the viability of an alternative single-stage process for the fabrication of Ti–6Al–4V alloy laminates for stacked composites. Afterward sliding wear behaviour on fabricated Ti–6Al–4V laminates prior to stacking is investigated. Laminates are fabricated by single-stage processing pass at different strain rates in dry condition. Sliding wear analysis is performed using a Tribometer. Morphology of tested samples are characterized by metallurgical tools like composition analysis by energy-dispersive X-ray spectroscopy, deformation analysis by X-Ray Diffraction, and worn-out surface topography analysis by scanning electron microscopy. Vickers hardness tester was used to analyse the micro-hardness of bulk and produced laminates and the roughness of fabricated laminate was measured by the roughness tester. Hardness measurement revealed an increase of ∼25% in the hardness value of fabricated laminates in comparison to the bulk material. Grains refinement observed in the laminates sample can be the reason for improved hardness. Wear rate was analysed at 10N, 30N, and 50N loads by keeping the sliding velocity constant at one m/s for all the produced laminates. The produced laminates show better wear resistance with low wear rate as compared to the parental material Ti–6Al–4V.

The effect of sintering time on the tribological properties of automotive brake pads

In this study, the effect of sintering temperature on the physical, chemical and tribological effects of sintered automotive friction materials was investigated. Using the powder metallurgy method, 3 different samples were produced with the codes A1, A6 and A11. Mixing, pressing and sintering processes were applied respectively as production steps. Mixing time is 90 minutes, speed is 15 rpm. The pressing pressure is 250 MPa and the duration is 1 min. The sintering temperature was 800 °C and the sintering time was 1, 6 and 11 hours, respectively. The sintering process was carried out in the sintering mold using Argon gas. As the sintering time increased, it was observed that there was an increase in the time-dependent friction coefficients of the samples. Increasing the sintering time also increased the density of the samples. As the sintering time increased, the gap in the sample decreased, as it provided better bonding of the dustsers.

Synergistic tribological effect between polyisobutylene succinimide-modified molybdenum oxide nanoparticle and zinc dialkyldithiophosphate for reducing friction and wear of diamond-like carbon coating under boundary lubrication

Organic molybdenum lubricant additive like molybdenum dialkyl dithiocarbamate (MoDTC) can cause wear acceleration of diamond-like carbon (DLC) coating coupled with steel under boundary lubrication, which hinders its industrial application. Therefore, polyisobutylene succinimide (PIBS), an organo molybdenum amide, was adopted to modify molybdenum oxide affording molybdenum polyisobutylene succinimide-molybdenum oxide nanoparticles (MPIBS-MONPs) with potential to prevent the wear acceleration of DLC coating. The thermal stability of MPIBS-MONPs was evaluated by thermogravimetric analysis. Their tribological properties as the additives in di-isooctyl sebacate (DIOS) were evaluated with MoDTC as a control; and their tribomechanism was investigated in relation to their tribochemical reactions and synergistic tribological effect with zinc dialkyldithiophosphate (ZDDP) as well as worn surface characterizations. Findings indicate that MPIBS-MONPs/ZDDP added in DIOS can significantly reduce the friction and wear of DLC coating, being much superior to MoDTC. This is because MPIBS-MONPs and ZDDP jointly take part in tribochemical reactions to form a composite tribofilm that can increase the wear resistance of DLC coating. Namely, the molybdenum amide on MPIBS-MONPs surface can react with ZDDP to form MoS2 film with excellent friction-reducing ability; and MPIBS-MONPs can release molybdenum oxide nanoparticle to form deposited lubrication layer on worn surfaces. The as-formed composite tribofilm consisting of molybdenum oxide nanocrystal, amorphous polyphosphate, and molybdenum disulfide as well as a small amount of Mo2C accounts for the increase in the wear resistance of DLC coating under boundary lubrication.

Water-based lubricant containing protic ionic liquids and talc lubricant particles: Wear and corrosion analysis

Water-based lubricants have been used in different industrial applications in recent years. However, studies evaluating the tribological and electrochemical effects of lubricants with Protic Ionic Liquid (PIL) and talc particles (TC) as additives on SAE 1010 and SAE 1045 steels are still scarce in the literature, which is the objective of this work. Samples extracted from steel sheets were investigated in the normalized (SAE 1010) and quenched-tempered (SAE 1045) conditions. Wear tests in a ball-on-plate type tribometer and corrosion tests using potentiondynamic polarization curves were performed in the presence of different lubricant solutions (PIL 3% + DI water, commercial lubricant 3% + DI water, with and without talc particle additions 0.05 and 0.1 wt%). Analyses of viscosity, pH, wettability, and particle size distribution were conduted on the lubricant and talc samples. Wear and corrosion surfaces were analyzed by SEM/EDS, and Raman techniques. The results showed that the tribofilm formed from the interaction between PIL lubricants and steel substrates decreased the wear due to the increase of lubricity of these lubricants. When the PIL and the commercial lubricants are compared, PIL additives presented higher performance, despite the talc addition. The influence of talc on the corrosion of steel is associated with the differential aeration effect, mitigated by adding the PIL.

Antifrictional Effects of Group IVB Elements Deposited as Nanolayers on Anodic Coatings

The utilization of anodized aluminum (Al) components would contribute greatly to combat against dry friction if good tribological properties could be attained. Despite its hardness, the wear rate of anodic coatings presents a major problem in many applications, including automotive, aerospace and high-tech industries. Recently, nanolayers of Ti demonstrated high tribological effectiveness and unusually low dry friction on anodic coatings. However, few researchers focus on the tribological characterization of nanolayers of other elements. In this study, nanolayers of Ti, Zr, Hf, Cu, Cr, Nb and Sn were deposited on anodized 1050 and 6082 alloys by magnetron sputtering and Atomic Layer Deposition. Major attention was devoted to surface roughness and hardness measurements, because of their importance for static friction. The results showed that structural, chemical and other intrinsic properties of nanolayers of Group IVB elements in many cases led to significant friction reduction, when compared to those of Cu, Cr and Hf. Nanolayers of 15 nm to 75 nm thicknesses appeared most effective tribologically, while 180 nm or thicker layers progressively lost their ability to sustain low dynamic friction. Deposition of nanoscale structures could provide advantages for the anodized Al industry in protection against incidental friction and wear.

Fundamental tribological effects in lubricated cutting processes

Using cutting fluids has the potential to increase tool life and workpiece quality by reducing loads during cutting. However, cutting fluids lead to additional costs and environmental impacts. To effectively utilise cutting fluids, it is important to gain insights into their working mechanisms, in particular via direct observations of the tribology at the contact surfaces. This paper presents methods to investigate lubrication in cutting, focusing on a new approach for accessing the distribution of cutting fluids at the tool's rake face. This technique of visualising a lubricating film between chip and rake face allows to deeply understand tribological effects.

Thermal contact resistance for stationary and moving heat sources in angular contact ball bearings

Sliding friction is a common tribological effect that occurs between the contact surfaces of the inner components (inner race, outer race and balls) of a spindle rolling bearing during operation. This friction generally generates heat, which can affect the performance of the rolling bearing. To date, numerous studies have assumed that the contact surface between the inner components of the bearing is circular and stationary. While this assumption has yielded adequate results, it is not sufficient in the case of angular contact ball bearings, where the contact surfaces are elliptical and could be treated as either stationary or moving heat sources. This paper presents solutions for both, stationary and moving heat sources for elliptical contact surfaces in a spindle rolling bearing. The primary objective is to find the thermal contact resistances which are dependent on the shape of contact, the loads, the rotational speed and the material properties thereof, applying the mathematical expressions developed by Muzychka and Yovanovich. These expressions were used to calculate various thermal resistances, providing results applicable to the analysis of thermal models in spindle rolling elements. Through finite element analysis (FEA) performed in Ansys Workbench, the stationary and moving heat sources were compared, finding the heat distribution along the elements of the bearing. The findings herein are suitable for the creation of thermal networks in rolling bearings, which are essential to predict their thermal behaviour.

Tribological Effects of Water-Based Graphene Lubricants on Graphene Coatings

In this study, the friction and wear characteristics of graphene coatings were evaluated using lubricants with various ratios of graphene ink to deionized (DI) water. When dry graphene ink and pure DI water were used as lubricants, the graphene coating initially peeled off, and the friction coefficient rapidly increased to a large value. However, when a lubricant with graphene ink added to DI water was used, a lubricating film was formed on the graphene coating and the friction coefficient was reduced significantly. Under dry and pure DI water conditions, severe wear morphologies were formed on the graphene coating surface, whereas in the case of the lubricant with graphene inks added to DI water, insignificant wear morphologies were formed. When the mixing ratio between DI water and graphene ink was 100:10 and 100:5, the friction coefficient and wear rate were the lowest, respectively. As a result of a long-term experiment in which the sliding cycle was performed for up to 100,000 cycles under the same experimental conditions, the lubricant with a 100:10 mixing ratio showed excellent lubrication properties, confirming that the friction coefficient and wear rate were significantly reduced compared to that of the dry or pure DI water lubrication conditions.

Tribological effects of different scaled chevron-shaped microstructures on the Stribeck curve of parallel contacts under unidirectional friction

Laser surface texturing is a widely used technology to improve the tribological behavior of articulating surfaces. Especially for lubricated contacts working in unidirectional motion, laser-generated chevron shapes are one of the most promising surface designs to reduce friction and wear. But, investigations regarding the effect of different chevron dimensions on the tribological performance of lubricated contacts are still lacking in literature. Therefore, we used a 300-femtosecond laser to apply chevron microstructures with different scaled leg widths (5–400 µm). Friction analyses were performed to determine the Stribeck curve of lubricated ring-on-disk samples at sliding velocities from 2.3 to 0.006 m/s and a constant load of 50 N. Results show that small-scale chevrons (5–40 µm) improve the overall tribological behavior of the contact partners. With small-scale chevrons, friction could be reduced by 29% in the boundary, 85% in the mixed, and up to 56% at the transition point from mixed to the lubrication regime compared to an unstructured reference. With a chevron leg width of 5 µm, a significant shift of the critical velocity for the lubrication regime transition to lower values was observed (reduction by 36% compared to the reference). In contrast, no substantial change of the coefficient of friction was observed with large-scale (leg width 200–400 µm) chevrons.

Design and Analysis of Cylinder Liner with Different Coatings

Abstract: In this project, the surface of a cylinder Liner in a diesel engine is coated with ceramiccoating powders by the plasmaspray technique using Ansys and its surface behavior is subsequently analyzed. The purpose of this study is to analyze with tribological effects of surface coating for a Liner in frictional mechanism. In, with and without coated cylinderliner was analyzed with Ansys software. The modeling and analysis of the cylinder liner is carrying by the catia and ansys software. Also, the combustion flow analysis of the cylinder liner is carried by Ansys software. From the obtained test results, it was found that the coated liner having improved properties in towards the diesel engine performance. The results show less deformation and fewer scratches due to wear on the Titania-coated Liner ascompared to uncoated one.

Effects of fly ash introduction on friction and wear characteristics of brake pads

Fly ash is a waste matter generally emitted abundantly from chimneys of the production facilities and should mostly be recycled. In this context, this study reveals the tribological effects of fly ash on brake pad components by doping the fly ash in basic brake pad matrix with various weight fractions of 30% (S30), 35% (S35) and 40% (S40) by reducing aluminum powder in the pad matrix. According to the results, as the fly ash concentration increases in the matrix, density and hardness of the structure were prone to decrease to an extent. Water immersion technique was used to determine density values and specially modified pin-on-disc tribotester was utilized to measure coefficient of friction (CF) and specific wear rate (SWR) values between brake pad samples and the cast iron rotating disc. Among prepared samples, maximum average reduction in density and hardness were observed to be by 3.97% and 10.67%, respectively. S30 depicted the minimum CF of 0.32 and maximum CF of 0.43 was performed by S40. Maximum specific wear rate was observed for S40 subtending to an increase of 8.67% from that of S30 to S40. Results showed that, though higher escalation in CF as the fly ash fraction elevates in the matrix, wear rates did not show a dramatic increase which is an indication of effectiveness of fly ash in brake pads in terms of braking performance and long term durability.

Development of a Method to Assess the Tribological Effect of Osteochondral Defects Within the Talocrural Joint

Category: Basic Sciences/Biologics; Ankle; Ankle Arthritis Introduction/Purpose: Osteochondral lesions of the talus commonly occur because of traumatic injury. These lesions can affect the biomechanical behaviour of the ankle joint resulting in further degradation of the tissue and development of osteoarthritis. However, little is known about the impact of such lesions to the biomechanical behaviour of the natural ankle joint, in particular changes to the tribology of the joint due to their introduction. The aim of this study was to develop a tribological simulation of the natural tibiotalar joint to assess frictional changes due to the introduction of chondral lesion and to further assess the impact of current treatment modalities such as AMIC techniques (Nanofracture with Chondro-Gide membrane) and osteochondral allograft cores (OCA). Methods: A healthy left cadaveric tibiotalar joint (n =1) was cemented into a custom-made jig; to preserve centre of rotation (COR). The sample was loaded into a ProSim Pendulum Friction simulator and tested using the following loading conditions. Simulations were run at 1-Hertz frequency for 3600 cycles with a constant load of 640 N applied through the tibia through a +- 10° flexion and extension (F/E) angle. Data was normalised using a mean frictional offset value calculated through a 2-minute pre- and post-test to account for additional frictional torque and changes to friction factor was assessed. Cartilage was assessed for changes in tissue appearance and damage. Following this, a 10-mm circular, chondral defect was introduced to talar dome and testing was repeated under the same conditions. The defect was repaired with a 10-mm Chondro-Gide patch and then 10-mm OCA before being subsequently tested using the same methods. Results: No visible changes were seen to the cartilage during testing for the healthy, defected and Chondro-Gide treated conditions. Some damage could be seen on the reciprocal tibial cartilage after testing with the OCA repair. Assessment of normalised friction factors showed that while testing, for each condition, the frictional output remained stable with a reduction in the mean friction factor seen due to the introduction of a defect. This was maintained with Chondro-Gide. A return to normal was seen in the OCA treatment with the overall mean values for the healthy and OCA repair were 0.0301 and 0.0329, respectively. In addition, overall mean frictional factor values in the presence of a defect and Chondro-Gide repair showed reduced frictional values of 0.0119 and 0.0103, respectively. Conclusion: This method will allow for potential preclinical evaluation of treatments for OLTs in an appropriately simulated environment to assess tribological changes. The values obtained for the frictional factor all sit within the expected range for friction between two cartilage surfaces that has been reported in the literature 0.003 and 0.08. Thus, providing a reliable platform for comparing different methods of osteochondral defect repair in the tibiotalar joint.

Tribological effect of ZBUP additive on the running-in quality of sliding bearing by fractal analysis

Purpose The purpose of this paper is to study the tribological effect of zinc borate ultrafine powder (ZBUP) oil additive on the running-in quality. Design/methodology/approach The running-in quality was assessed by friction coefficient and surface topography. Fractal parameters including fractal dimension, the width of multifractal, the multifractal difference, multifractal parameters, phase trajectory and correlation dimension were used to extract the nonlinear characteristics of surface topography and friction coefficient. Findings When the ZBUP additive was added, the convergence degree of the phase trajectory and the stability of the running in were higher than that of base oil. It indicates that the ZBUP additive can improve the running-in quality of sliding bearing. Besides, the ZBUP additive can shorten the running-in time. A boundary protective film, which has good friction-reducing and anti-wear effects, was generated on the surface when the ZBUP additive was added. Originality/value The results have a great significance to improve the running-in quality and prolong the service life of the sliding bearing.