Observing the atomic-level deformation of a frictional interface in real-time is important step to elucidate the mechanism of lubrication. We have combined the nano-scale handling capabilities of MEMS technology with the unsurpassed observation ability of TEM and developed a MEMS-in-TEM experimental setup. Our MEMS device had Ag tips with two degree-of-freedom controlled by electrostatic actuators. Opposing tips were brought into contact using the actuator. After forming a contact, one tip was actuated laterally but slowly enough to maintain the contact between the tips. We succeeded in observing the nano-scale deformation of Ag junction in real time.
Environmentally friendly lubricants have been gaining importance worldwide for different technical applications because of the growing concern for the environments. In this respect vegetable oils have immense potential to replace polluting mineral oil based lubricants due to their biodegradability, renewability, low toxicity and excellent lubrication performance. In this paper tribological property of two vegetable oils, namely, rapeseed oil and sunflower oil, were evaluated at different temperatures. The influence of stearic acid as an additive on the tribological properties of these vegetable oils was also investigated using four-ball tribometer. The viscosity, acid value, peroxide value and iodine value of the selected oils were determined experimentally following AOCS methods. It has been observed that stearic acid improved the antiwear properties of the vegetable oils based on formulation under boundary conditions of lubricants at different temperatures.
Study on usage of biodiesel, its impact on lubrication oil and its drain period, engine components are still under investigation. This experimental study investigates the effect of B20 FME (Fish oil methyl ester) on lubricating oil performance & engine emissions. Performance, Emissions and long-term wear tests were carried out on a computerized four stroke single cylinder diesel engine for both Diesel fuel & B20 FME, with SAE 20W40 oil used as Engine oil in a laboratory. Modern analytical techniques like a) Fuel dilution by Fourier Transform Infrared spectrometry (FTIR) b) Wear metal analysis by Inductively Coupled Plasma spectroscopy test (ICP) c) CHNS analyzer and other oil testing instruments were used to study the various tribological parameters of engine oil d) study on engine component by engine strip - down analysis before and after trials are done. The experimental results indicate that the engine can be safely operated with B20 FME, without significant changes in lubrication oil performance with respect to viscosity, Total Base Number (BN), Total Acid Number (AN) & soot content. It is observed that the B20 FME reduce the soot content in diesel engine, better cleanliness, less abrasive in component wear & hence extended engine oil drain period.
Bore ovality or non-circularity is due to manufacturing irregularity or running in. Misalignment is the non-parallel positioning of the shaft due to the nature of non-central dynamic loading, elastic deformation and thermal distortion of shaft. Misalignment may be also due to manufacturing error of shaft or bush. Study of combined effect of bore-out-of-roundness and shaft misalignment is important in bearing design. In this paper, the steady state characteristics of elliptic bore journal bearing are analyzed considering the shaft misalignment. A case specific film profile is derived to address the bore ellipticity together with shaft misalignment in eccentric positioning. Combined solution of Reynolds equation and Energy equation is carried out considering non-Newtonian piezo-viscous behavior of lubricant. The performance parameters such as film thickness, load carrying capacity, friction force, flow rate and side leakages are analyzed taking into account the thermal effect. The combined effect of bore non-circularity and shaft misalignment on temperature rise is also presented in this paper.
The friction at high speed and high pressure tends to cause the lowering of grease stickiness because the frictional heating occurs at the sliding surface, which will bring to the degradation of lubricity. In order to improve the lubricity, carbon nanotubes (CNTs), which has excellent heat conductivity, was added as an additive into the different types of greases. Two kinds of the CNTs, which were synthesized by a floating catalyst method at different annealing temperatures, were used. The sliding experiments were conducted to study the tribological performance of the grease composites by varying the added amounts of CNTs and were compared to the original greases. As a result, it was found that the CNTs improved both the friction and the wear properties. The optimum content of the CNTs in the grease composites was 0.3 mass%.