NB/SH/T 0721-2016 Determination of friction and wear properties of lubricating greases — High-frequency linear vibration test machine (SRV) method

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Card type: Test method

1. Method number / full title / English title / replacement relationship

• Standard number: NB/SH/T 0721—2016
• Chinese title: Determination of friction and wear properties of lubricating greases — High-frequency linear vibration test machine (SRV) method
• English title: Standard test method for measuring friction and wear properties of lubricating grease using a high-frequency, linear-oscillation (SRV) test machine
• Replacement relationship: replaces SH/T 0721—2002 "Determination method for friction and wear properties of lubricating greases (high-frequency linear vibration test machine method)"
• Adoption relationship: modified adoption by redrafting of ASTM D5707-11
• Publication/implementation: published on 2016-12-05, implemented on 2017-05-01
• Issuing authority: National Energy Administration
• Secretariat: Petroleum Fuels and Lubricants Subcommittee of the National Technical Committee for Standardization of Petroleum Products and Lubricants (SAC/TC 280/SC1)
• Drafting organization: Sinopec Lubricant Co., Ltd. Chongqing Branch (see the original foreword for participating drafting organizations)

2. Scope of application and non-applicability

• Applicable to the determination of the friction coefficient and anti-wear performance of lubricating greases under high-frequency linear vibration conditions using a high-frequency linear vibration test machine (SRV) under specified conditions such as load 200N, frequency 50Hz, amplitude 1.00mm, test duration 2h, and test machine temperature range from room temperature to 280℃.
• Also applicable to the determination of the anti-wear performance and friction coefficient of liquid lubricants under similar conditions.
• Not applicable: no explicit non-applicability clause is provided in the available source.

3. Method principle

On a high-frequency linear vibration test machine (SRV), a test ball is reciprocated against a test steel disk under constant load; after the test, the wear scar on the ball and the friction coefficient are measured. If a surface topography measuring instrument is used, additional wear information can be obtained by measuring the wear scar on the test disk. (Chapter 4 of the original text)

4. Reagents and materials (purity / preparation)

• 7.1 Test ball: AISI 52100 steel, Rockwell hardness HRC60±2, surface roughness Ra of 0.025μm±0.005μm, diameter 10mm.
• 7.2 Lower test disk: AISI 52100 steel, material produced by vacuum arc remelting, with inclusion rating evaluated by ASTM A295/A295M or ASTM E45 D method as class A, stiffness grade ≤0.5, or total impurity content K≤10 according to ISO 683-17 standard, and spherical carbides obtained by spheroidizing annealing, Rockwell hardness HRC60±2; the surface of the lower test disk shall be ground and free of abrasive material; the lower test disk has a diameter of 24mm and a thickness of 7.85mm; its surface topography shall satisfy the following four parameter value ranges:
  • 0.50μm < Rk (the unit in the original text is marked as UIN, requires confirmation against the source standard (source-text extraction)) < 0.65μm
  • 0.035μm < Rpk < 0.050μm
  • 0.020μm < Rvk < 0.035μm
  • 0.050μm < R (the subscript in the original text requires confirmation against the source standard (source-text extraction)) < 0.075μm
• 7.3 n-Heptane: analytical reagent. Warning: flammable, harmful to the body.
• 7.4 Isopropanol: analytical reagent. Warning: flammable, harmful to the body.
• 7.5 Toluene: analytical reagent. Warning: flammable, harmful to the body.
• 7.6 Cleaning solvent: the test disk shall be cleaned with a liquid solvent (chlorine-free, no residual film after evaporation). Note: a mixed solvent of equal volumes of n-heptane, isopropanol, and toluene is recommended. Warning: flammable, harmful to the body.

5. Apparatus and equipment

• 6.1 High-frequency linear vibration test machine (SRV): as shown in Figure 1, Figure 2, and Figure 3. SRV Test machine test range: load (for SRV I model, 10N–1200N; for SRV II model, 10N–1400N; for SRV III model, 10N–2000N; for SRV IV model, 10N–500N; model names require confirmation against the source standard (source-text extraction)), frequency (5Hz–500Hz), and amplitude (0.1μm–4.0mm). Note: if necessary, provide an upgraded device to allow the SRV II/III test machine to operate up to 1600N.
• 6.2 Microscope: equipped with an eyepiece of 0.005mm, or equipped with a micrometer readable to 0.005mm, and should have sufficient magnification for measurement; generally recommended magnification (the value in the original text requires confirmation against the source standard (source-text extraction)).
• Figure 3 Test chamber structure labels: 1— vibration drive rod; 2— test ball holder; 3— loading rod; 4— test ball; 5— test disk; 6— resistance heater; 7— resistance thermometer; 8— test disk holder; 9— piezoelectric measuring device; 10— base.

6. Recommended operating conditions

• Load: 200N
• Frequency: 50Hz
• Amplitude (stroke): 1.00mm
• Test duration: 2h
• Test machine temperature range: room temperature~280℃
• Running-in conditions: for SRV I model and SRV II model, 50N running-in 30s; for SRV III model and SRV IV model, 50N running-in 30s (original text 9.7.1, 9.7.4)
• Precision statistical test conditions: load 200N, frequency 50Hz, stroke 1mm, temperature 50℃ and 80℃

7. Sampling and specimen preparation

• 9.1 Wipe the surfaces of the test ball and test disk clean with a laboratory silk cloth or lint-free paper dipped in cleaning solvent, repeatedly wiping until there is no black (residue) on the silk cloth. Immerse the test ball and test disk in a beaker containing cleaning solvent, vibrate with an ultrasonic instrument for 10min, then rinse with clean (solvent) to ensure that no streaks appear on the specimen surfaces.
• 9.2 Place a small amount (about 0.1g~0.2g) of grease specimen on a clean area of the test disk surface that has no wear scar, and avoid (overlap with) the previously produced wear scar.
• 9.3 Install the test ball into the upper holder and place it in the middle of the grease specimen so that the specimen can form a circular uniform coating between the test ball and the test disk.

8. Analytical procedure

• 8.1 Preparation of SRV I model and SRV II model test machines:
  • 8.1.1 Before the test starts, preheat the test machine and chart recorder for not less than 15min.
  • 8.1.2 Adjust the instrument according to the instrument manufacturer's instructions so that the friction data appears at the maximum peak position of the test machine. Note: in most cases, this is accomplished by a slide switch located on (circuit board model requires confirmation against the source standard (source-text extraction)) (front side of the circuit board behind the panel) and a slide switch located on the rear panel of the control unit.
  • 8.1.3 Turn the rotation amplitude knob to "zero".
  • 8.1.4 Set the (switch) to the automatic position.
  • 8.1.5 According to the instrument manufacturer's instructions, set the frequency to 50Hz and the time to 2h00min30s.
  • 8.1.6 According to the manufacturer's instructions, set the required range and calibrate the chart recorder, and set the recorder paper speed.
• 8.2 Preparation of SRV III model and SRV IV model test machines:
  • 8.2.1 Before the test starts, turn on the test machine and computer and preheat for not less than 15min.
  • 8.2.2 Open the desktop software operating program, open the software connection program for online automatic detection and connection.
  • 8.2.3 When entering the test program and step unit, edit the test conditions and input parameters such as set test temperature, test time, test frequency, and test stroke.
  • 8.2.4 Enter the test measurement driver program, select the test condition type module, and input parameters such as test sample name, upper and lower specimen names, test operator, and file name.
  • 8.2.5 Confirm test conditions such as temperature, frequency, and stroke, and enter the preloading step.
• 9.4 After confirming that the test machine is not loaded (the load gauge reading indicates -13N or -14N), carefully place the test disk containing the grease specimen and test ball onto the test platform surface.
• 9.5 First tighten the test ball and test disk holders until resistance is felt. For SRV III model and SRV IV model, operate according to clause 9.6; for SRV I model and SRV II model, operate according to clause 9.7. (Note: the correspondence between model and step in the original text is suspected to be reversed at source-text extraction, requires confirmation against the source standard (source-text extraction))
• 9.6 For SRV I model and SRV II model, proceed as follows:
  • 9.6.1 First use the slow speed range, then tighten the test ball and test disk holders to a torque value of 2.5N·m, then reduce the load to 50N for the running-in test.
  • 9.6.2 Turn on the heating controller and set it to the required test temperature, such as 50℃ and 80℃.
  • 9.6.3 When the temperature is stable, turn on the recorder paper feed switch, lower the recorder pen, press the toggle start switch until the timer starts timing, then adjust the stroke amplitude knob to 1.00mm. Note: the stroke should be checked periodically by measuring the wear scar length on the test disk minus the wear scar diameter on the steel ball; the difference must be less than ±10% of the set stroke.
  • 9.6.4 When the digital timer reaches 30s, use the slow speed range to apply the load to 200N, run at this load for 2h±15s, and the test machine will stop automatically.
  • 9.6.5 After the test ends, turn (off) the machine, turn the power back on, and reduce the load to -13 or -14N for disassembly. Note: at the end of the test the power automatically (turns off).
  • 9.6.6 (Read the minimum friction coefficient value) from the recorder curve.
• 9.7 For SRV III model and SRV IV model, proceed as follows:
  • 9.7.1 First enter the preloading procedure; the machine will automatically apply a load of 50N for the running-in test, then use a torque wrench to tighten the test ball and disc fixture to 2.5N·m.
  • 9.7.2 Enter the software test run preparation procedure; the machine will automatically heat up.
  • 9.7.3 When the test temperature stabilizes, the testing machine will automatically start running, and the computer will display the curve graphs of each parameter.
  • 9.7.4 When the machine has run in under a load of 50N for 30s, it will automatically apply up to 200N; after running under this test load for 2h±5s, the testing machine and software program will automatically stop.
  • 9.7.5 After the test ends, the testing machine automatically shuts down and turns off heating, automatically unloads, and the computer automatically returns to the initial desktop program selection interface.
  • 9.7.6 Data analysis program: select the operator module, enter the test number unit to display the curve graphs of each parameter, and read the corresponding friction coefficient.
• 9.8 Remove the test ball and test disc, and clean them thoroughly as described in clause 9.1.
• 9.9 Place the test ball on a suitable fixture, measure with a microscope, with the minimum wear scar width accurate to 0.005mm, then measure once more the wear scar at an angular orientation of 90° from the first measurement.
• 9.10 Obviously this step has no specially specified part, but when additional wear analysis or wear volume measurement is required, the wear scar on the test disc may be subjected to surface topography measurement according to the surface topography measuring instrument manufacturer's instructions (see Appendix A). Test method ASTM D6425 (the text here in the source is incomplete, requires confirmation against the source standard (source-text extraction)) describes the criteria for calculating wear volume.

9. Qualitative and Quantitative and Calculation Formulas

• Report the minimum friction coefficient (read from the recorder curve).
• Report the dimensions on the test ball (wear scar): the two measured values and the average wear scar value.
• Report the depth of the wear scar on the lower test disc (if surface topography measurement was performed).
• Definition of friction coefficient: the dimensionless ratio (3.2) between the friction force (F) between two objects and the normal force (N) pressing on these two objects.
• Definition of wear volume: the amount of volume loss of the steel ball after the test (3.15).
• Specific calculation formula: not provided in the available source.

10. Precision

• Eighteen operators tested (several) kinds of greases on the SRV testing machine; the average minimum friction coefficient range was 0.056–0.122, and the average wear scar diameter range of the test balls was 0.50mm–0.90mm. The precision was determined by statistical examination of test results among laboratories under load 200N, frequency 50Hz, stroke 1mm, temperature 50℃, and 80℃.
• 11.1 Precision (95% confidence level):
  • 11.1.1 Average wear scar diameter of the ball:
    • 11.1.1.1 Repeatability: for the same operator, under specified operating conditions, with the same instrument and the same sample, the difference between two consecutive results shall not exceed 0.07mm.
    • 11.1.1.2 Reproducibility: for different operators, different laboratories, and different instruments, the difference between two independent test results on the same sample shall not exceed: under 50℃, 0.29mm; under 80℃, 0.24mm.
  • 11.1.2 Minimum friction coefficient:
    • 11.1.2.1 Repeatability: for the same operator, under specified operating conditions, with the same instrument and the same sample, the difference between two consecutive results shall not exceed: under 50℃, 0.012; under 80℃, 0.008.
    • 11.1.2.2 Reproducibility: for different operators, different laboratories, and different instruments, the difference between two independent test results on the same sample shall not exceed: under 50℃, 0.031; under 80℃, 0.032.
• 11.2 Bias: evaluating the friction and wear characteristics of grease by this test method will not produce bias, because the friction coefficient and wear scar diameter can only be determined according to the definitions in this test method.
• Appendix A (informative appendix) A.1.1: friction coefficient repeatability 0.01, reproducibility 0.03; test ball wear scar diameter repeatability 0.07mm, reproducibility 0.2mm.
• Appendix A A.1.2: the above precision data were obtained statistically from tests of three kinds of lubricating oils (one anti-wear hydraulic oil, one engine oil, and one EP gear oil) among 22 laboratories according to an internal laboratory test procedure.
• Appendix B (informative appendix): statistical data of the RR2000 and RR2001 international interlaboratory comparison tests (Table B.1, specific values source-text extraction severe noise, requires confirmation against the source standard (source-text extraction)).

11. Report

• 10.1 Report the following test parameters: running-in load (N); (test load) N; frequency Hz; stroke mm; test disc material; sample name.
• 10.2 Report on the test ball (wear scar): the two measured values and the average wear scar value.
• 10.3 Report the minimum friction coefficient.
• 10.4 If surface topography measurement was performed, the report shall include a copy of the friction coefficient test record and shall report the depth of the wear scar on the lower test disc.

12. Normative References

• GB/T 17754—2012 Tribology terminology
• GB/T 18778.2—2003 Geometrical product specifications (GPS) Surface texture: Profile method—Surfaces having stratified functional properties—Part 2: Height characterization using the linearized material ratio curve
• ISO 683-17 Heat-treatable steels, alloy steels and free-cutting steels—Part 17: Ball and roller bearing steels
• ASTM A295/A295M Specification for high-carbon anti-friction bearing steel
• ASTM D6425 Determination of friction and wear properties of extreme-pressure lubricating oils—SRV testing machine method
• ASTM E45 Method for determination of impurity content in steel
• DIN 51834-3 Lubricant testing—Friction test with translational oscillating apparatus—Part 3: Determination of friction properties of materials used with lubricants
• References: [1] DIN 51834-2

13. Source and verification

This page is an AI translation of the available Chinese method card. Human verification is pending. It is not an official translation of the standard. Check the source standard and product certificate before use.

14. Quick Q&A Reference