Key Engineering Materials Vol. 823

Abstract: This study involved planning different tool paths for an axisymmetric cup to explore the forming characteristics of the single point incremental forming (SPIF) process. In addition, this study developed a gradient theory to compute the inclined angle between the tangential and horizontal directions of the cup formed using single point incremental forming. The sheet thickness distribution of the cup was also calculated. To verify the theory, circle arc cups were formed by CNC machining using different tool paths. It was found that the cup formed using the spiral evolutional snail-line tool path produced a better surface than that formed using the equal height evolutional tool path. The sheet thicknesses of circle arc cups obtained by the experiment and using the cosine law were compared. A larger deviation was noted in the initial portion of the cup, whereas a smaller deviation was found in the other portion. This study also adopted a dual-conical cup to investigate the relationship between thickness and the initial inclined angle at the initial portion. It was found that a larger initial inclined angle led to good coincidence between the experimental and theoretical sheet thicknesses.

Abstract: This study aimed to understand the influence of small amount of Zr doping of amorphous carbonitride (a-CN) coatings on the structure, and mechanical and tribological behavior. The coatings were prepared using a four-target close-field unbalance magnetron sputtering system; two graphite, one Ti and one Zr targets were used. GDOS, SEM, XRD and XPS were used. A surface profilometer, a nanohardness tester, and a pin-on-disk wear tester were used. It was found the Zr doping resulting in the formation of ZrC and ZrN phases within the coating and the increase in the sp3 bonding fraction. The nanohardness was increased and the wear performance was largely improved.

Abstract: Hydrogels’ promising biocompatibility and biomimetic lubrication mechanism have led to widespread biomedical applications. To be eligible for load-bearing applications, such as cartilage reconstruction, they must be highly wear-resistant and induce ultra-low friction, once being implanted in vivo. In this study, Scanning Electron Microscopy was utilized on the worn surface of silica-nanoparticle reinforced Alginate-Polyacrylamide nanocomposite hydrogels (NCHs), as well as unmodified hydrogel as control samples, as a means of wear mechanism investigation, which is quite under-explored for these materials. Our results showed adhesion was the most prevalent wear mechanism in both NCHs and unmodified hydrogel matrix, while fatigue wear was observed in the form of surface pitting under highest load and highest test period conditions. Nevertheless, Si-NP was found to improve the wear-resistance of hydrogel matrix, as less severe surface deformation and pitting was inspected on the surface of NCHs.

Abstract: In this study, molecular dynamics (MD) are used to simulate the nanoimprinting behaviors of (001) Ni thin films using 3×3 array cuboid diamond punch. Different pitch of the punches was used to investigate the effect of the interaction among the forming pattern and the quality of the formed holes. Forming force was evaluated including normal and tractional force of the punch during pressing process. The dislocation behavior was also monitoring during the holes forming. The result showed that the pitch of the punch was 2w could get the best forming pattern.

Abstract: This study investigates the extreme pressure performance of phosphorus-based additives mixed with polyalkylene glycol (PAG) oil lubricant via a four-ball test, using an AISI 52100 hardened steel and a ceramics (ZrO2) ball, separately. According to the experimental results, PAG oil lubricant has a good tribological performance for small loads at room temperature. However, when the load or temperature was raised, the extreme pressure performance and anti-wear performance of the PAG oil lubricant declined significantly. Mixing phosphorus-based additives with PAG in appropriate ratios is expected to improve the tribological performance of the oil. Moreover, the ZrO2 four-ball test revealed an atypical wear behavior causing serious wear scar due to the sintering of the ZrO2 ball. Nevertheless, the study demonstrates that phosphorus-based additives in the PAG oil lubricant can reduce the sintering of the ZrO2 ball.

Abstract: Friction happens everywhere. Abrasives generated in tribological process will result in secondary wear. Abrasive wear is a kind of rather common but harmful wear, which is the main reason for the damage of fifty-percent mechanical components by friction. Surface texturing is an effective method to improve the tribological and lubricating performance of tribo-pairs. In this paper, with different-size diamond particles added into the lubricant and a surface of the tribo-pairs textured by different parameters (diameter and depth) with femtosecond laser, the relationship between the surface texture and the abrasive wear was researched, and the influence of the texture on the abrasive wear was analyzed. The friction experiments were carried out on UMT3. The microstructures were tested and analyzed by SEM, microscope and White Light Interferometer respectively. The experimental results showed that the size of the surface texture, compared with that of abrasives, is the main factor which determines the friction coefficient. As the size of the surface texture is much bigger than that of the abrasives, the texture can accommodate the abrasives efficiently, and thus the friction coefficient is reduced efficiently.

Abstract: It is well known that nanoparticles affect the interaction between lubricants and surfaces with various chemical compositions and different chemical and physical properties. In recent years, nanoparticles have started to play more important roles as lubricant additives for their potential in wear, friction and emission reduction and improving lubrication and fuel economy. Although nanolubricants are frequently used for friction tests, little is known about stability and degree of dispersion of these nanoparticles in viscous liquids. Most of them are unstable, agglomerate or aggregate which sediment over time. Boric acid (H₃BO₃) has always been a very important material due to its broad range of applications such as in medicine, cosmetics, automotive industry, metallurgy and also for miscellaneous purposes in other areas. Literature survey showed that friction between automobile engine parts could be greatly reduced using microscopic particles of boric acid.This study involves the new invention of successful suspension of nano boric acid (BA) additive added into 5W-40 fully synthetic commercial lubricating oil. This invention is confidential and realized by Murat ÖZAYMAN from Tribor ARGE Co. in Teknopark of YILDIZ Technical University in Istanbul-TURKEY. The particle size of BA is determined with (Transmission Electron Microscopy) (TEM). Backscattering and transmittance profiles proved that nano boric acid (BA) particles were in suspension in commercial engine oil. Suspended BA in engine oil is applied between piston ring and cylinder liner system in order to investigate their effect on friction and wear under boundary lubricated conditions. Simulation and measurement of friction and wear were conducted using a reciprocating tribometer. Surface analysis were performed using 3D digital optical microscope, Field Emission Scanning Electron Microscope (FESEM)/X-Ray, X-ray photoelectron spectroscopy (XPS) and Atomic Force Microscopy (AFM). Boron (B) from BA is well detected, mixed with other elements of additives and protected the surface under boundary lubrication conditions. The results indicate that BA can considerably improve the tribological performance of a piston ring and cylinder liner system under lubricated conditions. It has found that the friction coefficient is reduced with nano boric acid (BA) suspended engine oil and protected the surface mostly on cylinder liner mixing with other additives.

Abstract: Lubricants play a vital role in machine life and performance, reducing friction and wear and preventing component failure. Performance-enhancing additives are a vital part of today’s modern lubricants. In response to this need, this experimental work presents the development of the new suspended nanoboric acid (nBA) additive added in engine oil that can drastically lowered friction and wear.This is a new invention of nBA additive hold in suspension and added into 5W-40 fully synthetic commercial lubricating oil. This invention is confidential and realized by Tribor ARGE Co. in Teknopark of YILDIZ Technical University in Istanbul-TURKEY.The particle size of nBA is determined with (Transmission Electron Microscopy) (TEM). Turbiscan Tower Stability Analyzer results proved that nBA particles were in suspension in commercial engine oil. Suspended nBA in engine oil is applied between ball and disk system in order to investigate their effect on friction and wear under lubricated conditions. Simulation and measurement of friction and wear were conducted using a ball on disk reciprocating tribometer UMT-3. Surface analysis was performed using 3D digital optical microscope and surface roughness, Field Emission Scanning Electron Microscope (FESEM)/X-Ray and Atomic Force Microscopy (AFM). Boron (B) from nBA is well detected, mixed with other elements of additives and protected the surface under boundary lubrication conditions. The results indicate that nBA can considerably improve the tribological performance of a ball and disk pairs under lubricated conditions. It has found that the friction coefficient is reduced with nBA suspended engine oil and protected the surface on both ball and disk mixing with other additives.

Abstract: This study aims to develop a set of micro-elasticity abrasives preparation technology. The study developed micro-elasticity abrasives preparation equipment was used to discuss the feasibility of micro-elasticity abrasives preparation under the conditions of different heating temperatures and grain sizes of abrasives. According to the research findings, when the heating molding temperature is about 200 °C, #3000 SiC can be evenly coated on the surface of high polymer material, and the completed PS coated #3000 SiC, can indeed simultaneously retain the cutting properties of abrasives with a single material and the high polymer material property.