A scuffing load capacity test with the FZG gear test rig for gear lubricants with high EP performance

Methods for the evaluation of the scuffing load capacity of EP lubricants of API GL-4 and GL-5 performance levels have been developed for the standard FZG gear test rig, which has a centre distance of a = 91.5 mm. Procedure A10/16.6R/90 is capable of discriminating between industrial gear oils and automotive gear oils up to GL-4 performance level while procedure S-A10/16.6R/90 can be applied to GL-4 and GL-5 lubricants. The test methods were verified with reference oils and commercial gear lubricants. The results of the tests can be used to give a relative ranking of reference and candidate lubricants. They can also be used as limiting values in the scuffing load capacity rating method according to DIN 3990 (ISO DIS 6336).     

Friction coefficient in FZG gears lubricated with industrial gear oils: Biodegradable ester vs. mineral oil

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. J STLE Lubr Eng 1999; Höhn BR, Michaelis K, Doleschel A. Frictional behavior of synthetic gear lubricants. Tribology research: from model experiment to industrial problem. Elsevier 2001; Martins R, Seabra J, Seyfert Ch, Luther R, Igartua A, Brito A. Power Loss in FZG gears lubricated with industrial gear oils: biodegradable ester vs. mineral oil. Proceedings of the 31th Leeds-Lyon symposium on tribology. Elsevier; to be published; Weck M, Hurasky-Schonwerth O, Bugiel Ch. Service behaviour of PVD-coated gearing lubricated with biodegradable synthetic ester oils. VDI-Berichte Nr.1665 2002.]. The viscosity–temperature behaviors are compared to describe the feasible operating temperature range.Standard tests with the Four-Ball machine and the FZG test rig [Winter H, Michaelis K. FZG gear test rig—desciption and possibilities. In: Coordinate European Council second international symposium on the performance evaluation of automotive fuels and lubricants; 1985.] characterize the wear protection properties. Biodegradability and toxicity tests are performed in order to assess the biodegradability and toxicity of the two lubricants.Power loss gear tests are performed on the FZG test rig 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. Lubricant samples are collected during and at the end of the gear tests [Hunt TM. Handbook of wear debris analysis and particle detection in liquids. UK: Elsevier Science; 1993.] and are analyzed by Direct Reading Ferrography (DR3) in order to evaluate and compare the wear particles concentration indexes of both lubricants.An energetic model of the FZG test gearbox is developed, integrating the mechanisms of power dissipation and heat evacuation, in order to determine its operating equilibrium temperature. An optimization routine allows the evaluation of the friction coefficient between the gear teeth for each lubricant tested, correlating experimental and model results.For each lubricant and for the operating conditions considered, a correction expression is presented in order to adjust the friction coefficient proposed by Höhn et al. [Höhn BR, Michaelis K, Vollmer T. Thermal rating of gear drives: balance between power loss and heat dissipation. AGMA Technical Paper; October 1996. pp 12. ISBN: 1-55589-675-8.] to the friction coefficient exhibited by these lubricants. 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 operating temperature.     

Power losses at low speed in a gearbox lubricated with wind turbine gear oils with special focus on churning losses

In this study gear oils were tested for power loss behaviour in a two stage multiplying gearbox, on a back-to-back test rig with recirculating power. The tests were performed at low input speeds and high input torques with oil sump temperature set free.A power loss model simulating the power loss mechanisms was implemented to evaluate gear power losses, but failed to correctly describe the gear churning.Two lubricant flow regimes were identified, which are related to the nature of the fluid circulation, as well as with the gearbox case. A calibration method for the gear churning loss is proposed based on these results and a method to identify the transition between the fluid flow regimes inside the gearbox.     

Wear of gear of circular-arc tooth-profile: effect of helix angle and oil viscosity

The results are presented of an experimental investigation carried out at Mansoura University Laboratories aimed at studying the effect of change of helix angle and lubricating oil on wear of a relatively new type of gearing of circular-arc tooth-profile. Eighteen pairs of gears of 6 DP, 91.5 mm pitch diameter and different helix angles were run in power circulating gear test rig at different speeds and transmitting different loads, and the gears were lubricated with oils of different viscosities. It was found that wear increases with increasing helix angle and decreases with increase of oil viscosity. Variations of amount of wear with all the test variables are presented.     

Torque loss of type C40 FZG gears lubricated with wind turbine gear oils

Five fully formulated wind turbine gear oils were characterised. The gear oils have 320 ISO VG grade and different formulations: ester, mineral, PAO, PAG and mineral+PAMA.A back-to-back FZG test machine, with re-circulating power, was used and a torque-cell was included on the test rig in order to measure the torque loss. Eight thermocouples were included to monitor the temperatures in different locations of the test rig.Tests at 1.13, 2.26 and 6.79 m/s were performed for different FZG load stages: K1, K5, K7 and K9. Both gearboxes were jet-lubricated with an oil flow of 3 l/min. The input flow temperature was kept almost constant (80 ±1 °C).Friction generated between the meshing teeth, shaft seals and rolling bearing losses was predicted.     

Influence of lubricant on gear failures — test methods and application to gearboxes in practice

Base oil type, oil viscosity, and additive type and content have a strong influence on typical gear failures. As it is not possible to quantify the influence of a lubricant on load‐carrying capacity simply from a knowledge of the physical or chemical oil data, many test methods have been developed for the evaluation of mechanical—technological lubricant properties. Simple low‐cost bench test methods often show poor correlation with practice. From both experience and systematic investigation, it can be seen that testing of gear lubricants can be performed adequately only in gear test rigs using specified test gear geometry. The standard FZG back‐to‐back gear test rig has been developed over many years and improved for different types of gear failure simulation. The standard FZG oil test A/8.3/90 is widely used for the evaluation of the scuffing properties of industrial gear oils. Automotive gear oils of GL4 level can be tested in the step test A10/16.6R/90, and axle oils of GL5 level in the shock test S‐A10/16.6R/90. For slow‐speed regimes, the C/0.05/90:120/12 wear test can be used. The influence of lubricants on the micropitting performance of gears can be evaluated in the GF‐C/8.3/90 micropitting test. Different pitting tests are available, as single‐stage (PT‐C/9:10/90) or load spectrum (PT‐C/LLS:HLS/90) tests. The aim of this paper is to describe the influence of the lubricant on the different failure modes in gears, how to quantify this effect in adequate test methods, and how to introduce the results of such tests as determining values of the lubricant into load‐carrying capacity rating methods.     

A method for testing lubricants under conditions of scuffing. Part I. Presentation of the method

A method for the tribological assessment of lubricants under conditions of scuffing is presented. The method uses a four‐ball tester, and allows one to assess the effect of lubricant on scuffing intensity through an analysis of changes in the friction torque and wear of the stationary balls, at continuously increasing load. The behaviour of a lubricant under scuffing conditions can be characterised using the so‐called limiting pressure of seizure p_oz, which depends on the load at which the balls seize and the average value of the wear area calculated from the wear‐scar diameters measured on the stationary balls. A comparison is made ‐ from the point of view of the resolution, time consumption, and cost ‐ of the new method with the existing, standard tests, using a four‐ball tester and a gear test rig (FZG). It is concluded that the proposed method, unlike standard FZG and certain four‐ball tests, enables one to differentiate between gear oils, in agreement with their API GL performance level. The very short run‐time of the new method enables one to perform more tests and obtain a low standard deviation. The new method is much cheaper than the standard four‐ball and FZG methods.     

Tribological properties of an environmentally adopted universal tractor transmission oil based on vegetable oil

Universal tractor transmission oil (UTTO) is multipurpose tractor oil formulated for use in transmissions, final drives, wet brakes and hydraulic systems of tractors employing a common oil reservoir. In the present work, the results of a series of tests performed to evaluate vegetable based oils are presented. Tribological properties of formulated rapeseed and high oleic sunflower based UTTO were investigated in the standard and non-standard test procedures and compared with the properties of commercially available synthetic and mineral UTTO. Performances of test oils were demonstrated by using SRV high frequency test device, four-ball test rig, and FZG spur gear test rig. For final tests a laboratory hydraulic system and a spur gear test rig were used.     

Influence of Rolling Element Bearing Modeling on the Predicted Thermal Behavior of the FZG Test Rig

A thermomechanical model of the FZG test rig is presented. The numerical model is based on the thermal network method and takes into account power losses due to tooth friction, rolling element bearings (REBs), oil churning, and shaft seals. Some measurements underline that REB rings run at different temperatures. To investigate this difference, several REB models are proposed and compared to measurements. Their influence on the global thermal behavior of the gear unit is discussed and analyzed.     

Influence of Lubricants on Power Loss of Cylindrical Gears©

The total power loss of gears was measured in a back-to-back gear test rig. Test equipment, measuring principle and evaluation of the data are described. The influence of different lubricant type, viscosity and temperature on mesh and churning losses was investigated. The churning losses depended mainly on the viscosity of the lubricant and on the operating conditions, not on the lubricant type. The mesh power loss depended mainly on the type of lubricant, not on viscosity, temperature, or oil additives.

Churning losses can be reduced by using low viscosity lubricants. Mesh power loss can be reduced by as much as 50 percent of the power loss of mineral oils by using polyglycol-type lubricants. In wide application ranges, viscosity and oil additives do not influence mesh power loss. An experimentally-based equation for the coefficient of friction in the gear mesh is given. Earlier derived equations for the mesh power loss of different gear geometry were confirmed.     

Synthetic fluids for automotive gear oil applications: A survey of potential performance

This paper describes studies of transmission lubricants in an axle efficiency test rig. The test lubricants were evaluated over various temperature ranges, for each of five road load speed conditions. This was done for both truck and passenger car. Three synthetic gear oils were evaluated, based on various combinations of synthetic hydrocarbons, esters, and viscosity improvers, and were compared to conventional SAE 80W-90 lubricants. All three oils demonstrated improvements in axle eficiency. Also reported are evaluations of seven test lubricants in a high-temperature, high-torque test, and results of seal compatibility tests.     

Pitting load capacity test on the FZG gear test rig with load-spectra and one-stage investigations

Lubricants in their combination of base oil and additive influence the pitting and micropitting load-carrying capacity of cylindrical gears. The aim of the FVA ‘Pitting test’ research project was to develop and establish a test method on the standard FZG gear test rig with a centre distance a = 91.5 mm. Two different test procedures were proposed, one using a load spectrum and the other a constant load. These tests can be used to determine the relative pitting load capacities of reference and candidate oils. From these results the pitting load-carrying capacity can be calculated.     

工业齿轮油长周期密封相容性研究

工业齿轮油与齿轮箱密封圈的相容性对于机械设备正常运转至关重要.近些年随着齿轮箱技术不断发展,工业齿轮油密封相容性要求越来越严苛,高端齿轮箱采用常规静态相容性测试已不能满足要求,需采用长周期静态试验,以及与齿轮箱实际工况最为契合的长周期动态密封试验来评价工业齿轮油密封相容性.对3种不同抗氧剂体系的L-CKD矿物型工业齿轮...     

A laboratory technique for the evaluation of automotive gear oils of API GL-4 level

Automotive gear oils, as typically used in rear axles, are normally evaluated in terms of their performance in full-scale bench tests. One such test is the CRC L-19/CRC L-42 test, which is included in API and other specifications. The L-19 test method is now obsolete, and the L-42 is used basically to define GL-5 level oils. An indigenous test method, IIP Method VAV-382, has been developed at the Indian Institute of Petroleum on an Amsler machine, operating under sliding conditions between two discs, and is also included in the IS:1118-92 specification for multi-purpose gear oils for GL-4 level oils. This method has been re-examined to obtain better resolution of scuffing of the disc surfaces. The modified procedure has proved effective, and the procedure and results for various commercial oils are described in this paper, which shows the method to be effective for the evaluation of GL-4 level oils.     

兆瓦级机械功率全封闭试验台

针对机械全封闭兆瓦级功率试验台空白,而电封闭试验台耗能较大的现状,建成了兆瓦级机械功率全封闭试验台.介绍了其主要特点和应用案例,该试验台可用于大功率减速器、增速器、齿轮箱、变速箱、联轴器的机械性能检测、疲劳寿命校核验证.     

齿轮传动动态系统辨识及修形研究

利用自动控制理论研究实际工况下齿轮传动的动态性能, 通过系统辨识算法, 建立了直齿圆柱齿轮传动周向振动和噪声之间的差分方程模型, 此模型能够准确描述齿轮传动系统的动态特性。根据齿轮传动周向振动和轮齿变形之间对应关系, 对降低齿轮传动噪声的齿廓修形曲线进行了优化设计, 并进行了试验验证。为齿轮传动系统的修形、减振、降噪和优化设计提供了一种新的研究方法。     

An In-Line Method for Measuring Oxidation in Gear Oils and Hydraulic Fluids

A study was conducted to examine degradation of a gear oil and a hydraulic fluid using an in-line polymeric bead matrix (PBM) system that correlates oil oxidation with a relative change in the solvent properties of a fluid. The solvent property is an inherent aspect of an oil and allows oxidation to be measured independent of the base type, additive package, and viscosity. Samples of gear oil were heated to simulate a typical oxidized condition. Hydraulic fluids from a turbine were run for a limited time to provide discrete oxidized samples and test the sensitivity of the method. Results for the gear oils with the PBM are shown to compare favorably with infrared (IR) spectroscopy at room temperature. Elevated temperatures available with the PBM were needed to resolve oxidation levels for the hydraulic fluids.     

齿轮修形的优化设计与试验研究

通过对齿轮传动动态性能进行仿真研究,以一对直齿圆柱齿轮传动为例,研究了直线修形、抛物线修形和正弦修形,并优化设计了该齿轮传动取优动态性能时的齿廓修形曲线。通过比较修形齿轮和标准渐开线齿轮实测的振动加速度和噪声,证明了本优化修形设计方法对提高齿轮传动动态性能的突出效用。     

Industrial oil performance in terms of base oil chemical structure

Some performance properties for turbine, hydraulic and gear oils were correlated with changes in chemical structure for incorporated base oils. Blends with different viscosity grades were formulated from different neutral oils, brightstocks and additives. Different statistical approaches were used to evaluate the degree of fit for these correlations. The derived models were considered at a minimum of 99% confidence. Results clarified the role of non-hydrocarbons and aromatic compounds, either by type or by content, in changing the performance behaviour for tested industrial oils.     

Efficiency determination of cylindrical gear units in a back-to-back gear test rig

A method is presented for determining the efficiency of gear units in test rigs with a mechanically closed energy flow, based on measuring the losses in the rig, that is, the torsion torque at the driving motor and the stabilised thermic level. The energy losses between the two gear units would be separated according to the direction of power flow within the stressed framework of the rig. Experimental results are given for gear units including three types of gears, i.e.: involute gears with hobbed toothing, involute gears with ground toothing, and Wildhaber/Novikov (W/N) non-involute circular arc gears with two meshing lines, achieved by hobbing.