Monitoring the viscosity of diesel engine oil is very important as it affects the performance of engines. In this study, the AE signals are applied for measuring the viscosity of engine oil which is affected by the increase of the age of the in-service duration. AE signals are generated in the sliding zone of the piston as well as on the engine oil surface, because the signal is very sensitive to the viscosity of the engine oil. The AE signals can be translated into AE energy by using the Time Domain Analysis. The value of the viscosity will be assessed from the AE energy by applying certain mathematical equations. This study shows that the AE viscosity model is applicable to determine the viscosity of the engine diesel oil.
Electrospun nanofiber webs are of increasing interest for a variety of functional goods, not only textiles. The mechanical strength of these nanofiber webs must be evaluated to estimate the effect of rubbing against other fabrics and human skin. Therefore, we analyzed the frictional behavior of polyurethane (PU) nanofiber web against various fabrics and against artificial skin sheets. The present results are summarized as follows: 1) The mean friction coefficient of the PU nanofiber web was independent of the load. 2) Nanofiber web showed stick-slip motion, the frequency depending on the mating material and applied load. 3) The highest observed mean friction coefficients were 0.8 and 0.83 for silk and Flexcare®, respectively, and the lowest were 0.53 to 0.54 for Lorica® and silicone rubber, respectively.
Sealing devices are needed to prevent dust and water invading the positioning mechanisms of outdoor equipment. The frictional resistance generated by the seal frequently obstructs the smooth motion of the mechanism. The friction properties for high-speed and precision control mechanisms are required to be low and stable without lowering the sealing performance. In this study, the influence of the surface conditions of seal gland for PTFE sliding seal on friction properties was investigated experimentally. As a result, it has been found that the suitable surface condition of the seal gland for a high-speed and precision control mechanism is the electroless-nickel-plated surface of 0.1 μm Ra
Z-dol and Z-tetraol represent most often used disk lubricants. So that we would be better able to design lubricants of higher thermal stability (for Heat-Assisted-Magnetic-Recording application), detailed analysis of thermally induced oxidation processes of Z-dol and Z-tetraol were performed. Samples were heated in a thin-film configuration where facile infusion of oxygen occurred and were examined by F-19 and C-13 NMR. Z-dol was found to be stable in the 150 ∼ 200 °C temperature range. In the same temperature range Z-tetraol was found to undergo either (1) the well known step-wise oxidation of primary alcohol (alcohol → aldehyde → acid) or (2) direct conversion to Z-dol. The latter process is initiated by a base-catalyzed step whereby the end-group Z-O-CF2-CH2-O-CH2-CH(-OH)-CH2-OH converts to an aldehyde, Z-O-CF2-CH2-O-CH2-CH( = O), and CH3OH. Z-dol results upon oxidation of the aldehyde yielding Z-O-CF2-CH2-OH, CH2 = O and CO2. It was found that substitution of the terminal OH with a phenoxy unit suppressed these decomposition processes. Z-tetraol lubricant molecular chains that became bound to the carbon overcoat at their termini are also protected from these oxidation processes. Thus for HAMR application, a combination of lubricants bonded to the carbon overcoat at their termini and mobile lubricants possessing phenoxy groups at their termini may be the best possible system based on perfluoropolyether lubricants.
Thermoreversible gel lubricant (TR gel lube) has been developed as a unique new lubricant. TR gel lube contains a high percentage of aliphatic amide as a gel agent in the base fluid. It is able to repeatedly change from a gel state to a liquid state at the melting point. Therefore, the new lubricant is expected to be useful as an impregnant for porous tribomaterial. In previous research, the lubricants exhibited good lubricity and low friction properties. These tribological properties were depended on the molecular structure and content of amide gel agents. In this study, physicochemical properties of the TR gel lube were examined to discuss in detail the lubrication mechanism. It was revealed that TR gel lube indicated a soft gel compared with general grease by measuring dynamic viscoelasticity. Entropy changes of TR gel lubes were depended on the amide molecular structure by analyzing the thermo dynamical data. Lubricating mechanisms by oiliness effect of adsorbed gel agent and introducing to contact area were proposed.
A significant variation in oil film temperature has been observed in hydrodynamic journal bearings. Here, a journal bearing test rig has been developed to measure the oil film temperature on the three circumferential planes of the journal bearing. Further, an elliptical journal bearing with DImin = 65.2 mm, OD = 85 mm and L = 65 mm, Cm = 200 μm and C = 300 μm has been designed and tested to access the temperature rise at oil bush interface with three grade oils namely Oil 1, Oil 2, and Oil 3 at loads = 200 N, 400 N, and 500 N and speeds = 3000, 3500, 4000 rpm at constant oil supply pressure. The results show that with increase in the load at constant speed and pressure, and with increase in speed at constant load and pressure, the oil film temperature increases in the central plane of both the lobes of the bearing for all the grade oils. The nature of the oil film temperature distribution along the circumference of the journal bearing has been observed very close to the oil film temperature distribution reported in the literature.