Papers by Keyword: Lubricant

Abstract: Most air conditioners utilize vapor compression refrigeration cycle in their operation. In this cycle, the compressor is deployed to circulate the refrigerant from low to high pressures. Lubrication is an important aspect in the compressor to lubricate internal parts. Due to their remarkable properties in the thermo-physical and heat transfer capabilities, nanoparticles have prospect to be applied in the refrigeration and air conditioning system. The reliability and solubility nanoparticle of TiO₂ in refrigeration systems have been investigated by several by several researchers. By introducing TiO₂ nanoparticle in the lubricant, the friction coefficient and input power of the compressor can be decreased. An air conditioner with cooling capacity of 2.5 kW is utilized in the experiment. Five different concentrations of nanoparticle in the lubricant, viz.: 0.1, 0.2, 0.4, 0.5 and 0.6 gram of TiO₂ in one liter of lubricant were mixed using a magnetic stirrer. After 10 days, TiO₂ nanoparticles in the lubricant were observed its solubility. Furthermore, based on their solubility, TiO₂ nanoparticle with concentration of 0.2 g/L was selected in the experiments. The results show that the air conditioner using R290 with TiO₂ nanoparticle in the lubricants works normally and the input power of the air conditioner decreases about 3.1% and the cooling capacity and the COP increase about 5.1% and 8.4%, respectively, compared to the system without nanoparticle in the lubricant.

Abstract: Rotary swaging is an incremental cold forming process for tubes and rods. The established processes use lubricants based on mineral oil. The functions of the lubricant are the reduction of friction, wear and tool load, furthermore it cools the tools and flushes the working zone. But the use of lubricant increases the cost due to additional process steps and lubricant is diverted with the work piece during the process. Thus from economic and ecological points of view it is worthwhile to eliminate the use of lubricant. Therefore it is necessary to realize the functions of the lubricant in another way. For example by means of coating and micro-structuring of the tools the friction and wear can be influenced. In this study dry rotary swaging is tested with conventional tools and machine settings. The analysis of the recorded process parameters and the formed geometry of the workpiece reveal the potential of dry rotary swaging, but also the difficulties that arise. Dry rotary swaging needs a modification of the process and system parameters as well as an adjustment of the tools.

Abstract: Today an application of metal nanoparticles as additives to base oils is widely studied in tribological centers in many countries. The additives containing nanoparticles essentially raise the wear resistance ability of lubricants and reduce the friction coefficient. However, such lubricants are still not widely used. This paper gives a brief analysis of the problem.

Abstract: To understand the effects of tribo-film formation derived from ZnDTP (zinc dialkyl ditio phosphate) on friction behavior, friction tests were carried out with varying sliding time. The sliding surfaces were analyzed using Fourier transform infrared spectroscopy (FT-IR) and X-ray Photoelectron Spectroscopy (XPS). On the basis of the surface analytical results of the tribo-film, the absorption bands in the region of 1300-1000 cm^-1 assigned as polyphosphate appeared in all IR spectra after the sliding. The friction behavior of ZnDTP was related to the intensity change of the IR spectra peak at 1200 cm^-1.

Abstract: The increasing demand for fuel-efficient vehicles has led automotive industry to introduce new alloys in car manufacturing, characterized by a high stiffness and strength-to-weight ratio. Due to their mechanical and chemical properties, aluminium alloys appear potential candidates to replace traditional steels for several parts of the car-body-in-white, even if the limited formability at room temperature, the marked springback and the severe tribological behaviour have often represented important drawbacks in traditional properties. Recently, the use of temperature-assisted processes, such as hot stamping, allows overcoming such limits thanks to substantial increase of the formability and, at the same time, a drastic reduction of springback. However, the choice of proper process parameters, in terms of lubrication at the interfaces between the dies and the blank, and thermal parameters of the dies materials still represent critical points for the feasibility of the process. Recent investigations have proved the limits of assuming constant friction for all the areas of the dies and the steps of the deformations, especially with variable pressures and non-constant temperatures at the interfaces. Such factors, together with the lubricants and the lubricant deposition on the blank, the blank and dies coatings, the surface roughness, the stamping speed are not always considered, despite their considerable influence on the process tribology. In this paper the friction behaviour of commercially available automotive aluminium (AA6016 alloy) is studied. The friction coefficient is measured by means of a new machine for strip draw test at different levels of pressure, temperature, sliding speed and type of lubricant. The results report the investigation of the surface topography of the metal sheets, investigated by Energy-Dispersive X-ray spectroscopy and optical profilometry.

Abstract: The paper presents the results of tests on the distribution of hydrodynamic pressure in relation to the viscosity of a lubricant, the rotational speed of a journal and bearing load. Two different lubricants were selected for taking tests: base oil SN-150 and mineral engine oil. The distribution of hydrodynamic pressure was determined employing a device constructed for this particular purpose. It has been proved that the type of the lubricant, bearing load and, to a lesser extent, the rotational speed of the journal affect the distribution of hydrodynamic pressure.

Abstract: Effect of nanoparticles to improve the lubrication load capacity and resistance to extreme pressure of water-based rolling liquid was studied by four-ball tester. Compression experiments were conducted in different lubrication conditions with nanoparticles using Gleeble hot compression simulation machine. Then the residual nanoparticles characteristics and the surface morphology of the compressed sample were analyzed by SEM and EDS. The results show that water-based nanoTiO₂ lubricant can efficiently reduce the friction during metal deformation. nanoZnO is preferred to adhere to metal surfaces and employed to isolate the surfaces. A new lubricating mechanism of nanoparticles in metal hot deformation named convex peak extreme pressure buffering mechanism is thereby proposed, which is verified by the surface morphology of compressed sample.

Abstract: Magnesium alloy is known for its light weight and high strength. Due to the desirable properties, Magnesium alloy is required in the fields such as transportation from the energy-saving point of view. The development of forming methods is especially highly expected. In order to manufacture productions of high dimensional accuracy with good surface finish without defects, it is important to evaluate tribological characteristics of forging of Magnesium alloys. In this paper, the friction coefficients were measured by the ring compression test. It compresses a ring specimen between parallel tools and is the method for the friction coefficient by the rate of change of the inside diameter. The friction coefficients of several kinds of Magnesium alloys have been evaluated depending on temperature, compression speed, and the kind of the lubricant here.

Abstract: Soil pollution around railroad sites is mainly caused by heavy oils such as diesel and lubricants. In particular, the majority of contamination in soil around railroad turnouts is caused by oil that drips off of railcars and lubricants that leak during vehicle maintenance. Generally, removing lubricants from contaminated soil is more difficult than removing diesel, due to the properties of the respective oils. This study aims to investigate alternative remediation method of lubricant-contaminated soils around railroad turnouts. The EK-Fenton process was used to clean up the lubricant-contaminated railroad soil. Several operating conditions were tested, including the concentration of hydrogen peroxide, and electrolyte types and concentrations. We determined that the removal efficiency was affected by the amount of EOF in the soil and its oxidizing capacity. The TPH removal efficiency was greatest at 0.1 M of NaCl electrolyte and 5 % (v/v) of hydrogen peroxide. This shows that the in-situ EK-Fenton process is a promising remediation technique for decontaminating railroad soil polluted with lubricant oil.

Abstract: Lubrications industry is widely expand throughout the years. Well established mineral oil based promised the highest demand all over the world. But as the environmental concern is debated at most of world conferences, people are thinking to find the alternative for mineral oil replacement due to its non-biodegradable behaviour. The best suited source that having quite a par characteristic with mineral oil is vegetable oil. Vegetable oil is well known with its super bio-degradable characteristic. The source is renewable and does not require huge cost as compared to mineral and synthetic oil in term of exploration, development, production and transportation. Palm oil based is best suited among the vegetable oil series because of its stability and sources around the world. The major issue of palm oil based lubricant is low oxidative stability as the lubricant is commonly used at very high temperature and long shelf life application. Therefore some modification of molecule structure is needed by adding selected anti-oxidant at certain ratios. Tertier-butyl-hydroquinone (TBHQ) is used as anti-oxidantin this study. The results showing that a sufficient concentration of anti-oxidantprovides better solution for the low oxidative stability issues raised in palm oil based lubricants. The TBHQ also showed good characteristic in protecting two mating surfaces in wear scar analysis.