Lubricant Influence on Slow Speed Wear in Gears (original) (raw)
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Power Loss in FZG gears lubricated with industrial gear oils: Biodegradable Ester vs. Mineral oil
Tribology and Interface Engineering Series, 2005
Two industrial gear oils, a reference paraffinic mineral oil with a special additive package for extra protection against micropitting and a biodegradable non-toxic ester, are compared in terms of their power dissipation in gear applications [1,2]. The physical properties, wear properties and chemical contents of the two lubricants are characterized. The viscosity-temperature behaviors are compared to describe the feasible operation temperature range. Standard tests with the Four-Ball machine and the FZG test rig characterize the wear protection properties. Biodegradability and toxicity tests are performed in order to assess the biodegradability and toxicity of the two lubricants. Friction and wear tests have been performed with a configuration that combines rolling/sliding in a line contact simulating the working conditions on gears. The results for the ester oil presented a lower friction coefficient and operating temperature throughout tthe test in relation to mineral oil. Power loss gear tests are performed on the FZG machine using type C gears, for wide ranges of the applied torque and input speed, in order to compare the energetic performance of the two industrial gear oils [ 3 ]. The results of the power loss gear tests show that the operating temperature of the ester oil is always smaller than that of the mineral oil. Lubricant samples are collected during and at the end of the gear tests [ 4 ]. The lubricant samples are analyzed by Direct Reading Ferrography (DR3) in order to evaluate the wear particles concentration (CPUC) and the index of wear particles severity (ISUC). Both parameters indicate that the gear lubricated with the mineral oil suffered more flank tooth wear than the one lubricated with the biodegradable ester. The influence of each lubricant on the friction coefficient between the gear teeth is discussed taking into consideration the operating torque and speed and the stabilized temperature.
Tribology International, 2009
Gears are one of the most common mechanisms for transmitting power and motion and their usage can be found in numerous applications. Studies on gear teeth contacts have been considered as one of the most complicated applications in tribology. Depending on the application, the speed and load conditions of teeth may change triggering several types of failures on teeth surface such as wear, scuffing, micro-pitting and pitting. The above-mentioned faults influence changes in vibration and acoustic signals, due to changes in operating conditions such as increase in temperature and decrease in lubricant film thickness and specific film thickness. These abnormal changes result in cumulative effects on localised or distributed faults on load bearing surfaces of gears. Such damages cause reduction in tooth stiffness and severity of damage can be assessed by evaluating the same using vibration-based signals. This paper presents the results of experimental investigations carried out to assess wear in spur gears of back-to-back gearbox under accelerated test conditions. The studies considered the estimation of operating conditions such as film thickness and their effects on the fault growth on teeth surface. Modal testing experiments have been carried out on the same gear starting from healthy to worn out conditions to quantify wear damage. The results provide a good understanding of dependent roles of gearbox operating conditions and vibration parameters as measures for effective assessment of wear in spur gears.
ABM Proceedings, 2014
For lubrication of open gear drives applied in rotary furnaces, often gear greases are used as well as for lubrication of gear boxes in difficult sealing conditions. The selection of the gear grease influences strongly the wear behavior. Investigations with flow greases NLGI 00 were made in a back-to-back test rig determining the weight loss due to wear acc. to the standardised procedure ISO 14635 part 3. Different influences like base oil viscosity, thickener type and additional solid lubricant type were analysed. Only the type and amount of solid lubricant shows a significant influence on the weight loss due to wear. Finally, a linear wear coefficient clT according to the calculation method of the wear amount according to Plewe is derived and can be used to transfer the test results to any gears in practice.
Tribology International, 2006
Two industrial gear oils, a reference paraffinic mineral oil with a special additive package for extra protection against micropitting and a biodegradable non-toxic ester, were characterized in terms of their physical properties, wear properties and chemical contents and compared in terms of their power dissipation in gear applications [Höhn BR, Michaelis K, Döbereiner R. Load carrying capacity properties of fast biodegradable gear lubricants.
Gears made from different polymeric materials (general purpose polyamide - PA 66, unreinforced Poly-Ether-Ether-Ketone – PEEK 450G, 30% carbon fiber reinforced Poly-Ether-Ether-Ketone – PEEK 450CA30) and coated on their flanks with thin layer of different solid lubricants (MoS2, graphite (C), BN and PTFE) are tested in relation to wear and mesh point temperature in conditions of prolonged dry running. The derived experimental results are shown graphically. Some conclusions are given (the order of wear increasing according to the type of coating (PTFE (least wear), uncoated, graphite, MoS2, BN); proportional correlations between wear and mesh temperature, etc.).
GEARS AND THEIR LUBRICATION EVOLUTION OF GEARS
In the earliest machines that man built to do his work, gears formed an essential part. The teeth of these early gears were pegs fashioned out of wood and inserted in the rims of wooden wheels. They were crude affairs and the loads that were transmitted were necessarily lightspeeds were low. Lubrication was of little concern then, for when a tooth wore or broke, its replacement was a simple matter. The first big forward step in gear design came when peg teeth were abandoned, and teeth shaped much like those in modern gears were developed. Gears with teeth instead of pegs were made by mortising or keying individual hard wood pieces of the desired profile into the rim of a wheel. The first metal gears were probably cast of either bronze or iron. With this advance, lubrication assumed an important role in reducing wear and prolonging the life of the gear. Loads and speeds, however, were moderate and vegetable or animal oils sufficed as lubricants. Since those early times, correct gear-tooth profiles and proportions have been developed. Moreover, tools have been built capable of machining gear teeth in the hard, tough materials which advances in metallurgy have made available. Thus, present day gears with their accurately cut teeth of correct profile and finely finished surfaces are a far cry from the wooden pegged gears of the past. Modern gears fulfill a purpose in practically every field where power must be transmitted or where motions of machine parts must be controlled. Because of the countless ways in which gears are used, there are wide variations in their design, size, operating speed and loading. Paralleling the developments in the technique of gear design and manufacture, lubrication has become increasingly important. Even with accurately cut teeth of correct profile, gears can not operate successfully unless a lubricating film is maintained between the surfaces of the meshing teeth. If this film permits metal-to-metal contacts to occur, wear will be rapid, tooth profiles will be destroyed and failure of the gear will result. Correct Lubrication means that separating films are maintained, and that long gear life and reliable operation are assured. Once the impor tance of Correct Lubrication is fully realized more thought will be given to securing the right lubricant and to applying it in the right way. Gargoyle Lubricants, which are recommended in this publication for enclosed gears, are unusually stable, and therefore, resist oxidation to an exceptional degree. They rendex excellent service over long periods of continuous operation. Gargoyle lubricants recommended for open gears have the strong adhesive properties which enable them to cling to the tooth surfaces; thus they provide maximum protection. Moreover, for both enclosed and open types, they have the necessary high film strength to withstand the heavy loads and shocks that may accompany gear operation. FUNDAMENTALS. Gears are employed to transmit motion and power from one revolving shaft to another. The shafts on which gears are mounted can only take one of three positions with respect to each other-they may be parallel (Fig. 1), may intersect at an angle (Fig. 2) or may cross (Fig. 3). In each case, power and motion are transmitted positively, efficiently and dependably. Because of this, the application of gears to modern industrial machinery is practically without limit. FRICTION WHEELS Although gears are usually used to transmit motion from one shaft to another, it is quite pos. sible to transmit this motion by means of friction wheels. When pressed tightly together the fric tion between the surfaces is sufficient to transmit a limited amount of power. * If the shafts are parallel, the friction
Condition Monitoring of Variable Speed Worm Gearbox Lubricated with Different Viscosity Oils
Applied Mechanics and Materials, 2015
Over the years, condition monitoring of gear transmission systems have captured significant worldwide attention from both industries and academia. This is in light of the fact that an effective condition monitoring techniques will unquestionably extend the life span of the rotating equipment. In this research, both the vibration and temperature monitoring techniques were utilized to characterize the vibration behavior of worm gear as function of gear lubricant's viscosity. Three different types of lubricant's viscosity; VG100, VG460 and VG680 were used in the study to serve the sliding friction of worm gears. The predetermined speeds of electric motor at 900, 1150 and 1400 rpm were introduced to the gearbox prior to the measurement of vibration signal and temperature profile. The results revealed that a lubricant with higher viscosity contributes to less vibration amplitude. At 1150 rpm, it was recorded that the vibration amplitudes are higher compare to the other motor speeds, for all lubricant's types. In this case, VG100 showed the highest vibration amplitude followed by VG460 and VG680. This result was corroborated well with the obtained temperature profiles which are 35.0°C, 35.7°C and 39.3°C for the respective VG100, VG460 and VG680. Thus, concludes the correlation between the lubrication's viscosity, vibration level, temperature profile and worm gear speed.
Experimental Analysis of Chemically Degraded Lubricant’s Impact on Spur Gear Wear
Lubricants
The impact of lubricating oil degradation, which can happen during both storage and use, on spur gear wear is thoroughly examined in this paper at all scales, from macro to nano. A thorough structure was created by combining the results of testing performed at the macroscale on a test rig and at the nanoscale using tools such as FESEM analysis. Using a single-stage spur transmission under two different working conditions (‘40 Nm, 1200 rpm, 198 h’ and ‘50 Nm, 500 rpm, 90 min’), macroscale experiments were carried out using both conventional and artificially degraded lubricant oils. Aqueous hydrochloric acid (36.46% v/v concentration) was added to the lubricating lubricant to induce artificial degradation. Wear development and oil degradation were monitored in real time using tools such as metallic wear detritus sensors and oil sensor suites. Offline methods, such as total acid number (TAN) and pH value readings, were used with periodic lubricant oil samples. It was discovered through...