Experimental Study of Rheological Behavior of MWCNT-Al2O3/SAE50 Hybrid Nanofluid to Provide the Best Nano-lubrication Conditions

In this study, MWCNT-Al2O3 hybrid nanoparticles with a composition ratio of 50:50 in SAE50 base oil are used. This paper aims to describe the rheological behavior of hybrid nanofluid based on temperature, shear rate ($$\dot{\gamma })$$ γ ˙ ) and volume fraction of nanoparticles ($$\varphi$$ φ ) to present an experimental correlation model. Flowmetric methods confirm the non-Newtonian behavior of the hybrid nanofluid. The highest increase and decrease in viscosity ($${\mu }_{\rm nf}$$ μ nf ) in the studied conditions are measured as 24% and − 17%, respectively. To predict the experimental data, the five-point-three-variable model is used in the response surface methodology with a coefficient of determination of 0.9979. Margin deviation (MOD) of the data is determined to be within the permissible limit of − 4.66% < MOD < 5.25%. Sensitivity analysis shows that with a 10% increase in $$\varphi$$ φ at $$\varphi =$$ φ = 1%, the highest increase in $${\mu }_{\rm nf}$$ μ nf of 34.92% is obtained.

An Experimental Study of Micro-Dimpled Texture in Friction Control under Dry and Lubricated Conditions

Friction control is a vital technology for reaching sustainable development goals, and surface texturing is one of the most effective and efficient techniques for friction reduction. This study investigated the performance of a micro-dimpled texture under varying texture densities and experimental conditions. Reciprocating sliding tests were performed to evaluate the effects of the micro-dimpled texture on friction reduction under different normal loads and lubrication conditions. The results suggested that a micro-dimpled texture could reduce the coefficient of friction (CoF) under dry and lubricated conditions, and high dimple density results in a lower CoF. The dominant mechanism of the micro-dimpled texture’s effect on friction reduction was discussed, and surface observation and simulation suggested that a micro-dimpled texture could reduce the contact area at the friction interface, thereby reducing CoF.

The Tribological Adaptability for Ventral Scales of Dinodon rufozonatum in Dry/Wet/Rough Environments

The ventral scales of Dinodon rufozonatum were investigated to understand the outstanding tribological adaptability in various environments. The coefficient of friction (COF) of ventral scales was measured and changed with the contact conditions. It was discovered that the COF of scales under water-lubrication conditions (WLC) was larger than that under dry conditions (DC). More interestingly, the COF increased first and then decreased as the substrate roughness reduced. The abrasion marks on scales were then observed. The results indicated that the scales in DC wore more gently than that in WLC. Moreover, the degree of wear reduced with the decrease of substrate roughness. The frictional performance of ventral scales enabled the snakes to move more efficiently, quickly, and flexibly in multiple environments.

Wear and Friction properties of H-Al-17Si alloy with dry, lubrication and coated (DLC-Star) conditions under HFRR

Dry, lubrication (SAE15W40), and coated (DLC-Star) reciprocating tribological tests on rapid solidified AlSi17Cu3.5-4Mg0.6-0.8 alloy was conducted using a high frequency linear reciprocating rig (HFRR) at ambient temperature. The alloy fabricated with the rheo-stir squeeze casting procedure under T-6 condition. However, at different loading (0-30 N) conditions, wear and friction properties of rapid solidified H-Al-17Si alloy are investigated. It is observed that the lower friction coefficient value obtained for DLC-Star coated H-Al-17Si alloy compared to dry and lubrication conditions. Though, for dry and lubricated sliding, the obtained wear coefficient values are 2.9X10-3 mm3/N.m and 4.0X10-4 mm3/N.m. A lower coefficient of wear value of 5.4X10-5 mm3/N.m was recorded with DLC-star coating under dry conditions. The alloy wear coefficient values first increases with applied load (up to 20 N) and then decreases (20 N to 30 N). EDS, AFM surface roughness profilometer, SEM, and advanced metallurgical microscope (AMM) analysis techniques used for the characterization of surface morphologies. The developments in friction and wear coefficients were fundamentally ascribed to the dispersion and size of primary Si elements and the development of tribo-oxide films on the rapid solidified AlSi17 alloy coated (DLC-Star) surfaces.

Experimental Research on the Influence of Working Conditions on Vibration and Temperature Rise of Si3N4 Full-Ceramic Bearing Motors

Working conditions such as lubrication, preload, and rotational speed have important influence on vibration and temperature rise of the spindle motor. In this study, controlled variable experiments are carried out on the silicon nitride (Si3N4) full-ceramic ball bearing and steel bearing of the same type, and the vibration signal characteristics and temperature rise of the spindle motor are tested and analysed, by changing the lubrication conditions, preloads, and rotational speeds of the spindle motor. Through the research, it is found that as the rotational speed increases, the vibration velocity of the Si3N4 full-ceramic bearing spindle motor under different preloads and lubrication conditions shows an overall increasing trend; kurtosis generally presents a downward trend and gradually flattens, indicating that although the vibration velocity increases at high speeds, the vibration signal shows a relatively stable state. As the rotational speed increases, the difference of vibration velocity under the condition of applying preload and no preload decreases, indicating that the influence of preload on the vibration of full-ceramic bearing spindle motor decreases with the increase in rotational speeds. At the same time, it is found that fr and 5fr have greater impact on the vibration of full-ceramic bearing spindle motor, where fr is the frequency of the bearing in normal operation, and 5fr is 5 times of the normal operating frequency. Lubrication conditions have little effect on the temperature rise of full-ceramic bearing spindle motor, and the temperature rise under nonlubricated conditions is even slightly lower than that under grease lubrication conditions. The research results show that the vibration velocity and temperature rise of Si3N4 full-ceramic bearing spindle motor are less than those of steel bearing with the same type, indicating that full-ceramic bearing has better performance than steel bearing under the same working conditions.

Research into the lubrication of a rotary lip seal using ferrofluid

The paper presents the results of research into a hybrid seal which is a combination of standard rotary lip seals and a magnetic fluid seal. To maintain the magnetic fluid in the friction zone region, either a specially shaped pole piece was used or the shaft was modified accordingly. The research study concerns the allowable operating pressure and lubrication conditions in short-term and durability tests after which shaft wear was also assessed. Magnetic fluids with different rheological and magnetic properties were considered. The test results showed that the long-term operation of a hybrid seal is possible. The requirements, however, are the appropriate value of the magnetic field and dynamic viscosity of the magnetic fluid.