FZG Gear Test Rig Research Articles

Evaluation of vibration behavior at different sensing positions on gearboxes

Monitoring systems for rolling contacts in machinery are widespread. There are multiple solutions in various applications like Health Usage Monitoring Systems (HUMS) for Helicopters and smart bearings from different manufacturers. The number of solutions and possibilities is rising. This paper outlines how the vibrational behavior depends on the measuring position outside and inside the gearbox. The effect of the sensor location is evaluated by examining different locations close to the main excitation of gearboxes—the loaded tooth contact—as well as positions on the gearbox housing. Based on the results, recommendations for an optimal sensor position for gear vibration monitoring are given by considering the efforts of sensor integration. The results can be used to select sensors with the lowest cost to support the widespread gear vibration monitoring.Important locations for health monitoring are the gear meshes inside the gearbox. Due to the requirement of high power density, a compact design is mandatory. This does not allow for sensor application close to the gear meshes but only on the outside of the gearbox. An impediment of signal quality and less chance of early damage detection is the consequence. Hence, efforts have been made to directly integrate multiple sensors inside the gear body without negatively impacting the package.For the investigation of the vibration transmission behavior, an FZG gear test rig is selected. These standardized test rigs are approved and established all around the world for the creation and evaluation of various gear failure data. The presented test rig has been modified to be able to sense vibration in the gear wheel, at the gear wheel, and on the gearbox housing to evaluate different sensor positions and vibration sensors for their suitability on vibration measurement.

How lubricant formulations and properties influence the performance of rotorcraft transmissions under loss of lubrication conditions

Loss of lubrication (LOL) in a rotorcraft transmission causes erratic degradation of drivetrain components due to direct surface contact thereby increasing the frictional heat in the system. This article studies the ability of synthetic and mineral-based lubricating oils typically used in the aviation industry regarding their physical properties, chemical composition, and detailed chemical structure to extend the longevity of the rotorcraft transmissions in the event of LOL. The lubricating oils were subjected to boundary lubrication tests using a FZG gear test rig and two lab-scale tribometers, cylinder-on-ring and ball-on-disc. The results provide an enhanced ranking of the selected lubricating oils based on their load-carrying capacity and scuffing resistance under LOL conditions complemented by the consideration of the oil chemistry.

Tribological properties of laser-generated hard ceramic particles in a gear drive contact

The lubricant is a central element in the transmission design. It primarily separates the two contact partners through a pressure-induced solidification in the lubrication gap, thus enabling the operation of heavily loaded sliding-rolling contacts. On the one hand, the quality and properties of a lubricant depend on the base oils, which differ by their viscosity and process-technological parameters. The addition of particulate additives gives the lubricants further functional properties that are not contained in the base oil. In this study, the influence of laser-synthesized yttria-stabilized zirconia nano- or submicrometer spheres as dispersed functional elements in the lubricant is studied, and their impact on wear and fatigue on the tooth flank is investigated. The work includes systematic investigations on the influence of the particle’s shape and size by running tests on a FZG gear test rig. Finally, the potential of the laser-generated particles as a lubricant additive is evaluated in a first conclusion.

Analysis of efficiency of spur ground gears and the influence of running-in

High-performing gear transmissions are needed to reduce CO2 emissions. In this paper an FZG gear test rig was used to investigate how two running-in loads affect the gear mesh efficiency for two different temperatures. The gear surface roughness was investigated in parallel with testing. Higher efficiency was observed for tests using a high running-in load, and for low lubricant temperatures. The running-in load had a larger effect on the mesh efficiency than temperature. The high running-in load also yielded higher gear mesh efficiency and had a larger impact on surface parameters.

The effect of running-in on the efficiency of superfinished gears

Reduced gear contact losses are necessary to keep operating temperatures, as well as fuel consumption low. In this work, an FZG gear test rig was used to investigate the effect of running-in on superfinished gears with respect to efficiency. This was compared to ground gears where a higher contact pressure yielded higher efficiency. No difference was found between the two running-in procedures when analysing superfinished gears. The effect of running-in on gears decreased when the initial surface roughness was reduced, which initially had an Ra, Rz and Rpk value of 0.08, 0.75 and 0.08μm, respectively. Superfinished gears showed an overall higher efficiency; however, a distinctly lower efficiency was present below 2m/s when compared to ground gears.

Torque loss and wear of FZG gears lubricated with wind turbine gear oils using an ionic liquid as additive

This work presents a study of the tribological behavior of a mineral fully-formulated wind turbine gear oil additised with [BMP][NTf2] ionic liquid. The target application is the wind turbine gearboxes, thus the fully formulated oil with and without ionic liquid additive was tested in a rolling bearings test rig to measure the thrust rolling bearing torque loss and was also tested in a FZG gear test rig to measure the gears torque loss at operating conditions similar to the observed in a wind turbine gearbox.The results show that a wind turbine gear oil additised with ionic liquid can reduce the torque loss and improve the gearbox efficiency while producing less wear particles as observed in the oil analysis.

Experimental application of pitting formation for 20MnCr5 carburized gear tooth

Gear tooth contact analysis and a FZG gear test rig were applied to study and analyze gear contact fatigue in this paper. Under the range of operating conditions, experiments were performed in the test rig by using standard FZG type C spur gear test specimens which were made from 20MnCr5 gear steel. Test rig, spur gear test specimens, the properties of the gear material were also introduced. After the test, pitting formation was investigated using scanning electron microscopy. Two kinds of fatigue spallings caused by subsurface fatigue failure and surface fatigue failure were investigated. And energy spectral analysis for two kinds of fatigue positions were analyzed by the EDS detector, the materials of subsurface fatigue failure are the oxide Al2O3 and the carbide, and the black textures of surface fatigue failure are the oxide and the non-martensitic material. Through the mechanism analysis of this gear contact fatigue failure, it is founded that reducing the oxygen content in the material, can effectively reduce the oxide inclusions in the steel. It would provide a reliable reference study for 20MnCr5 carburized gear.

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.

Developments in mass finishing technology

Reduced gear contact losses are necessary to keep operating temperatures, as well as fuel consumption low. In this work, an FZG gear test rig was used to investigate the effect of running-in on superfinished gears with respect to efficiency. This was compared to ground gears where a higher contact pressure yielded higher efficiency. No difference was found between the two running-in procedures when analysing superfinished gears. The effect of running-in on gears decreased when the initial surface roughness was reduced, which initially had an Ra, Rz and Rpk value of 0.08, 0.75 and 0.08 μm, respectively. Superfinished gears showed an overall higher efficiency; however, a distinctly lower efficiency was present below 2 m/s when compared to ground gears.

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

AbstractMethods 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).

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.

Scoring tests of aircraft transmission lubricants at high speeds and high tem peratures

AbstractAircraft engines contain gears that have to be lubricated under conditions of high speeds and extremely high temperatures, In this field of application scoring damage can occur. In Europe and partly also in the USA the scoring load capacity of gear oils is expressed in terms of FZG Scoring Load Stage; the FZG Gear Test Rig is described. The normal test procedure A/8.3/90 as standardised in DIN 51 354 using A‐type gears at a pitch line velocity of v = 8.3 m/s and a starting oil temperature of 90°C is presented. A modified procedure at double speed and increased oil temperature A/16.6/140 is discussed. The scoring load capacity of aircraft transmission lubricants is expressed worldwide in Ryder Gear Test results. Because of the high costs and problems with the availability of test gears a modified FZG Ryder Test was developed. The method is presented and comparative results of typical aircraft engine oils in the FZG, the FZG‐Ryder and the original Ryder Gear Test are shown. From this experience it becomes obvious that alternative test methods for the evaluation of scoring load capacity of aircraft transmission lubricants can be available in the near future.

Studies on Limiting Load for Scoring of Spur Gears : Effects of Zn-P Anti-Wear Agent by Means of FZG Gear Test Rig

The limiting load for scoring was investigated by means of the FZG gear testing machine. The influences of coefficient of oil viscosity and concentration of anti-wear agent (Zn-P type) in oil upon the limiting load for scoring were disclosed. Furthermore the results of these gear tests were compared with the results of 4 ball tests. We have found in general that the higher the revolutional speed of gear, the greater the the influence of anti-wear agent upon the increasing rate of limiting load for scoring. And further we have found that the lower the viscosity of base oil, the greater the influence of anti-wear agent (Zn-P type) up-on the increasing rate of limiting load for scoring.