1、I r 98FM8 New Test Methods for the Evaluation of Wear, Scuffing and Pitting Capacity of Gear Lubricants by: B.-R. Hhn, P. Oster, K. Michaelis, Gear Research Centre (FZG), Germany American TECHNICAL PAPER COPYRIGHT American Gear Manufacturers Association, Inc.Licensed by Information Handling Services
2、New Test Methods for the Evaluation of Wear, Scuffing and Pitting. Capacity of Gear Lubricants B.-R. Hhn, P. Oster, K. Michaelis, Gear Research Centre (FZG), Germany The statements and opinions contained herein are those of the author and should not be construed as an official action or opinion of t
3、he American Gear Manufacturers Association. Abstract For maximum energy savings low viscosity lubricants are frequently used. Increasing transmitted power leads to higher temperatures and thus thinner lubricating films. These tendencies increase the failure probability in gear contacts with respect
4、to wear, scuffing, micropitting and pitting performance. New test methods on modified FZG gear test rigs were developed to evaluate the load carrying capability of gear lubricants. For the low speed regime a wear test using C-type gears at low pitch line velocity of 0.05 m/s, and two different tempe
5、ratures of 90 and 120 “C to consider different additive response at high loading of load stage 12(C/0.05/90:120/12) was developed and applied to many different lubricants. New scuffing procedures for gear lubricants of scuffing performance between API GL 3 and GL5 were developed. The step test A10/1
6、6.6R/90 uses A-type gears of 10 mm pinion face width at 16.6 m/spitch line velocity with a driven pinion. A discrimination of all gear oils up to the level of API GL 4 is possible. A shock test S-A10/16.6R/90 with direct loading in the expected load stage discriminates between GL 4 and GL 5 lubrican
7、ts. Different standard pitting tests are available for different lubricant viscosity grades using C-type gears at 8.3 m/s pitch line velocity and 90 “C in load stages 9 (PT C/9/90) or 10 (PT C/10/90). For automotive applications load spectrum testing is possible at low (PT C/LLS/90) and high (FT C/H
8、Ls/90) loads. For applications with long oil drain intervals a combined pitting and oil ageing test was developed (PITS C i85 TS) using C-type gears at variable load, speed and temperature conditions. At high temperature conditions between 120 and 150 “C the oil ageingproperties together with their
9、influence on pitting characteristics is evaluated in correlation to a reference oil. The test methods are described. Test results with different market products are discussed. Copyright O 1998 American Gear Manufacturers Association 1500 King Street, Suite 201 Alexandria, Virginia, 22314 October, 19
10、98 ISBN: 1-55589-726-6 COPYRIGHT American Gear Manufacturers Association, Inc.Licensed by Information Handling ServicesP NEW TEST METHODS FOR THE EVALUATION OF WEAR, SCUFFING, AND PITTING CAPACITY OF GEAR LUBRICANTS B.-R. Hhn, P. Oster, K. Michaelis Gear Research Centre (FZGI, Germany 1 Introduction
11、 The lubricant as a design element can play an important role in the slow speed wear, scuffing, micro- pitting and pitting behavior of gears in power trains. With the demand of extended oil drain intervals, pre- dominantly in automotive applications, not only the Jerformance of the new oil but also
12、that of used oils with thermal and oxidative degradation has to be ob- served. Base oil type, viscosity and additive system influence the different failure modes. Comprehensive knowledge of the lubricant performance under compa- rable test conditions is the key factor for lubricant optimization for
13、transmissions in practice. a* A number of test methods was developed using the FZG back-to-back gear test rig where over 500 machines are available world-wide. These meth- ods are the Chevron wear test A/0.57/120/10 for tractor hydraulic fluids I I, the scuffing test A/8.3/90 2, 31, the micropitting
14、 test GF C/8.3/90 41 for indus- trial gear oils, and the pitting test PT C/9:10/90 51 for automotive gear oils (see Table 1). Continuous oil development, cost reduction and new market demands made it necessary to develop new test methods for gear oils. These new methods on the FZG gear test rig are
15、presented and discussed. 2 General Considerations on Test Strategies The best test configuration for full comparabili- ty is the actual gearbox under typical operating condi- -ions. For industrial gear applications this is always too a expensive and for automotive gear applications this is mostly to
16、o time consuming. The second best are test procedures using defined test gears with high reproducibility in geome- try, heat treatment and surface finish being exposed to exaggerated operating conditions in order to reduce test time. Parameters which are modified versus oper- ating conditions have t
17、o be chosen very carefully for best simulation. Test Gears High reproducibility of test gears can only be achieved when one manufacturer produces such gears on the basis of a commercial interest. Exotic test gears where only 200 pairs are ordered every three years, can hardly be produced to the requ
18、ired high quality standard. Therefore, it is highly recommended to write a new test procedure around already existing test gears, as e.g. FZG standard test gear types A and C (see Table 2). The production figures of FZG standard test gears type A are in the range of some 2000 per year and type C in
19、the range of some 500 per year. The manufacturer of these gears has dedicated three grinding machines only for the finishing of A type gears. Together with the control in the CEC project group ST 007, dealing with the scuffing test, a contin- uously high accuracy and reproducibility of the test gear
20、s can be guaranteed. Test gear geometry can be chosen for best simulation of the desired failure mode. A large module is in any case necessary to avoid tooth breakage. For wear investigations according to Plewe 61 the sliding COPYRIGHT American Gear Manufacturers Association, Inc.Licensed by Informa
21、tion Handling ServicesParameter Scuff i ng test Wear test Micropitting test Gear type A A G F-C 8.3 rn/s Pitch line velocity + 8.3 rn/s 0.57 rn/s Lubrication DIP DIP Spray Oil Temperature 90 oc 121 oc 90 oc uncontrolled controlled controlled Driving gear Pinion Pinion Pinion Failure criterion Load s
22、tage to Wear rate Load stage to total scuffed face in rng/kWh rnicropitting depth width 20 rnrn 15 min per LS 20 h in LS 10 IP 334 ASTM D-5182 CEC L-07-A-96 7.5 pm 16 h per LS Test procedure Standards DIN 51 354 ASTM 4998 FV A Pitting test PT-C 8.3 rn/s DIP 90 oc controlled Pinion Running time to pi
23、tted area on one tooth 4% test time FZG PITS C i80 TS c 2.4 5 E: 2.2 reference oil oil A oil 0 oil type Fig. 18: Results of the PITS Test tions a universal test method PITS C i80 TS was de- rived using conditions of variable load and speed at in- creased oil temperatures between 120 and 150 OC. The
24、method was established for a standard mineral reference oil API GL 4 (see Fig. 17). After a one hour run-in at low speed and high torque a first sequence of the test procedure is run. During these first 70 hours the Miner sum of the oil has reached unity Ioii = 1.0 and the oil is changed. The Miner
25、sum of the oil Ioi1 is calculated from the failure accumulation of the applied , ; temperature-time-spectrum versus the T-T-curve in Fig. 16. The load spectrum is chosen such that the pitting Miner sum of the gears is IPit = 0.5. The Miner sum of the gears Ipit is calculated from the failure accumu-
26、 lation of the applied load spectrum versus S-N-curves for the gear pair at different operating temperatures. With a second oil fill in the second test sequence after again 70 hours the conditions for the oil are Xoii = 1 .O and for the gears Xpit = 1 .O. The gears lubricated with the reference oil
27、fail with pitting. Candidate oils are tested against the same procedure. If no pitting occurs after the second 70 .hours a third and a fourth se- quence with each 70 h without oil change is added. Fig. 18 shows results of different oils from the market compared to the reference oil. For further test
28、 discrimi- nation the load spectrum can be increased from the 80% level of load spectrum type i (i801 to e.g. 95 % (i95). This leads to a failure of the reference oil after the first test sequence of 70 h. The method allows the relative pitting ranking of different lubricants versus a reference oil
29、under new and aged lubricant conditions. With the determination of viscosity, acid number and IR-changes during the test, the oil ageing properties of the lubricant can also be evaluated. 9 COPYRIGHT American Gear Manufacturers Association, Inc.Licensed by Information Handling Services4 Summary New
30、test methods on the standard or modified FZG back-to-back gear test rig were developed. These cover the .evaluation of O wear performance of gear oils under thin film conditions O scuffing performance of automotive gears oils up to GL 4 and GL 5 level O pitting performance of autornotive gear oils u
31、nder variable load conditions O pitting performance of automotive gear oils with simulation of oil ageing. The methods allow a relative ranking of different lubri- cants against a reference oil as well as the introduction of the results into gear load carrying capacity meth- ods. 5 Acknowledgement T
32、he authors thank the DGMK (German Society for Petroleum and Coal Science and Technology) and the FVA (German Gear Manufacturers Research Asso- ciation) for their technical support and the AiF (Associ- ation of Industrial Research) for sponsoring the differ- ent research projects. 6 Bibliography ll A
33、STM Standard D 4998-89: Standard Test Method for Evaluating Wear Characteristics of Tractor Hydraulic Fluids. 121 ASTM D-5182: Standard Test Method for Evaluating the Scuffing (Scoring) Load Capacity of Oils. 131 CEC L-07-A-95: FZG Gear Machine: Load Car- rying Capacity Test for Transmission Lubrica
34、nts. 41 FVA Information Sheet No. 54/1-IV: Test proce- dure for the investigation of the micro-pitting capacity of gear lubricants. July 1993. 51 FVA Information Sheet No. 2/IV: Influence of Lubricant on the Pitting Capacity of Casecarburized Gears in Load-Spectra and Single-Stage-Investigations. Ju
35、ly 1997. verschlei von geschmierten, langsam laufenden a- - 161 Plewe, H.-J.: Untersuchungen ber den rdern. Diss. TU Mnchen 1980. 7 Lechner, G.: Die Frelastgrenze bei Stirnrdern aus Stahl. Diss. TH Mnchen 1966. 8 Schnnenbeck, G,: Einflu der Schrnierstoffe auf die Zahnflankenermdung (Graufleckigkeit
36、und Grbchenbildung) hauptschlich im Umfangsgeschwin- digkeitsbereich 1 . 9 m/s. Diss. TU Mnchen 1984. I91 Hhn, B.-R., Oster, P., Schedl, U.: Pitting Load Capacity Test in the FZG Gear Test Rig with Load- Spectra and One-Stage Investigations. Fifth CEC Inter- national Symposium on the Performance Eva
37、luation of Automotive Fuels and Lubricants, 13-1 5 May 1997, Gteborg, Sweden. I101 Hhn, B.-R.; Michaelis, K.: Test methods for gear lubricants in the FZG gear test rig. 2nd Interna- tional Conference on Tribology “Balkantrib 96“, Thes- saloniki, 5-7 June 1996, p. 873 - 880. (1 11 DGMK Information Sh
38、eet No. 377: Method to Assess the Wear Characteristics of Lubricants in the FZG Gear Test Rig. Deutsche Wissenschaftliche Gesell- schaft fr Erdl, Erdgas und Kohle e.V. (German Soci- ety for Petroleum and Coal Science and Technology, DGMK), 1996. I1 21 dynamic Lubrication. Elsevier Tribology Seri (1
39、985). 1131 FTM Method 6508: Load Carrying Ability of Lubricating Oils (Ryder Gear Machine). I 41 DIN 3990, Teil 4: Tragfhigkeitsberechnung von Stirnrdern: Berechnung der Fretragfhigkeit. 11 51 Winter, H., Michaelis, K.: Scoring Load Capaci- ty of EP-Oils in the FZG L-42 Test. Fuels and Lubri- cants
40、Meeting Toronto, Oct. 18-21, 1982, SAE Tech- nical Paper Series 821 183, S. 1 - 7. I 61 FVA Information Sheet No. 243: Scuffing Test EP-Oils, Method to Assess the Scuffing Load Capacity of Lubricants with High EP Performance Using an FZG Gear Test Rig. November 1995. I 71 IS0 DTR 13989: Calculation
41、of Scuffing Load Capacity of Cylindrical, Bevel and.Hypoid Gears. De- cember 1995. I1 81 Wei, R.: Einflu der lalterung auf die Zahn- flankentragfhigkeit. Diss. TU Mnchen 1,994. Dowson, D. and Higginson, G.R.: 10 COPYRIGHT American Gear Manufacturers Association, Inc.Licensed by Information Handling Services
