1、 _ SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising ther
2、efrom, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be revised, reaffirmed, stabilized, or cancelled. SAE invites your written comments and suggestions. Copyright 2017 SAE International All rights reserved. No part of this
3、publication may be reproduced, stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: +1 724-776-49
4、70 (outside USA) Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/standards.sae.org/AIR6157 AEROSPACE RECOMMENDED PRACTICE ARP6157 Issued 2017-05 WAM Pressure-Viscosity Coefficie
5、nt Measurement RATIONALE The pressure-viscosity coefficient of lubricating oils is an inherent property for generating EHD films. It is used in rolling element bearing and gear design calculations for predicting EHD (elastohydrodynamic) film thickness and for estimating wear life, scuffing resistanc
6、e and contact fatigue life. Pressure-viscosity is a report item in AS5780 and the measurement method is currently described in an appendix of AS5780. Improvements in the measurement technique and the identification of the operating speeds to avoid thermal effects have provided recommended test condi
7、tions for measurement. The SAE E-34 committee has made recommendation for the test method to be documented as recommended practice. TABLE OF CONTENTS 1. SCOPE . 3 2. REFERENCES . 3 3. APPROACH . 4 4. REQUIRED HARDWARE 6 5. TEST PROCEDURE 12 5.1 Specimen Cleaning and Storage 12 5.2 Configure WAM in B
8、all under Disc Mode and Install Optics Hardware. 14 5.3 Establish Communication Between AChILES and WAMControl. 23 5.4 AChILES Software Set Up . 24 5.5 Calibrate with static contact 27 5.6 Measure Spacer Layer Thickness 31 5.7 Check accuracy of X position and Y position . 33 5.8 Measure EHD Film Thi
9、ckness at 40 C Over a Range of Entraining Velocities 33 5.9 Save the AChILES project file 36 5.10 Save the AChILES report file . 36 5.11 Calucate the average test temperature 36 5.12 Calculate the average test oil viscosity at the average test temperature. 36 5.13 Calculate Pressure-Viscosity Coeffi
10、cient . 37 5.14 Repeat 6.8 to 6.13 at 70 C, 100 C, 130 C, and 150 C 37 6. PRECISION STATEMENT . 38 7. NOTES . 38 7.1 Revision Indicator . 38 SAE INTERNATIONAL ARP6157 Page 2 of 38 Figure 1 Inlet zone pressure generation and EHD parameters for oil film thickness . 4 Figure 2 WAM set up for EHD film t
11、hickness measurement 5 Figure 3 Space Layer Optical Disc and Grade 10 M50 Ball . 6 Figure 4 Disc bolt, washer, ball bolt and fiber optic cable bushing . 6 Figure 5 Disc sump assembly 7 Figure 6 Driven ball optics nosepiece adaptor . 7 Figure 7 Driven ball optics assembly 8 Figure 8 Silicone tubing a
12、nd inline oil filter . 8 Figure 9 Microscope with 5x and 10X objectives . 9 Figure 10 Adaptor Plate 9 Figure 11 XY Microscope Slide 10 Figure 12 Digital camera and lens 10 Figure 13 Camera power supply 11 Figure 14 Light source and fiber optic cable 11 Figure 15 RGB and Null modem cables . 11 Figure
13、 16 Monochromatic (red) filter 12 Figure 17 Configuration for flushing ball and disc sump with solvent and oil in between test oils . 13 Figure 18 Rig clear of specimens and accessories in preparation for homing. 14 Figure 19 Checking run-out of driven ball optics nosepiece adaptor . 15 Figure 20 Ch
14、ecking ball run-out. 16 Figure 21 Driven ball optics assembly installed 16 Figure 22 Disc sump installed. WAM9 shown, others similar . 17 Figure 23 Ball sump positioned within disc sump. WAM9 shown, others similar . 17 Figure 24 Disc spindle position 1mm above top of ball. WAM9 shown, others similar
15、 . 18 Figure 25 Lube system configuration . 19 Figure 26 XY slide attached to WAM . 19 Figure 27 XY slide adaptor plate installed on microscope . 20 Figure 28 Microscope installed on XY slide 20 Figure 29 Camera installed on microscope 21 Figure 30 Disc and ball sump filled with test fluid . 22 Figu
16、re 31 Initial evaluation range dialog box 24 Figure 32 Interferometry type dialog box 25 Figure 33 Pressure correction dialog box . 25 Figure 34 Imaging dialog box . 25 Figure 35 Project constants 26 Figure 36 Static contact white light interference image with no spacer layer. 28 Figure 37 Static co
17、ntact with red filter for calibration 29 Figure 38 Interference peaks across monochromatic static contact 29 Figure 39 Calibration profile selection 30 Figure 40 White light fringes with suitable calibration 31 Figure 41 Spacer layer thickness measurement 32 Figure 42 Recommended entraining velocity
18、 range(s) for film thickness measurements at (4) temperatures 35 Figure 43 Film Thickness Vs. Speed in AChILES 36 Figure 44 Calculation of pressure viscosity coefficient . 37 Figure 45 Sample pressure-viscosity data for a 5 cSt MIL-PRF-23699 oil . 38 SAE INTERNATIONAL ARP6157 Page 3 of 38 1. SCOPE T
19、he lubricant performance capability for aero propulsion drive systems is derived from the physical properties of the oil and performance attributes associated with the chemical properties of the oil. Physical properties, such as viscosity, pressure-viscosity coefficient and full-film traction coeffi
20、cient are inherent properties of the lubricating fluid. Chemical attributes are critical for the formation of protective boundary lubricating films on the surfaces to prevent wear and scuffing. These attributes are also associated with surface initiated fatigue (micropitting). To assure performance
21、and to provide required information for engineering design, methodology for at least five oil properties are being studied: (1) pressure-viscosity coefficient, (2) full-film traction coefficient, (3) scuffing resistance, (4) wear resistance; and (5) micropitting propensity. The pressure-viscosity co
22、efficient can be measured either directly by assessing viscosity as a function of pressure using high-pressure apparatus, or indirectly by measuring film thickness in an optical interferometer. This document (ARP6157) describes the test method for calculating the pressureviscosity coefficient by mea
23、suring film thickness with a WAM (Wedeven Associates Machine) and the calculating pressure-viscosity coefficient from the measured film thickness. 1.1 Purpose The purpose of this test method is to measure the elastohydrodynamic (EHD) film thickness of a test oil over a specific range of entraining v
24、elocities, five temperatures and one Hertzian contact stress. The test conditions presented here are suitable for a range of oil viscosities, including commonly used aviation oils with viscosities between 3 and 10 cSt. The measured EHD film thickness is used to calculate the pressure-viscosity coeff
25、icient at each test temperature from a commonly used Hammrock-Dowson film thickness equation 1, 2 shown in Figure 1. The pressure-viscosity coefficient is used in design, along with other physical properties of the oil, such as viscosity and traction coefficient. The five selected temperatures for m
26、easurement are common to other properties, as reported in AIR5433B 3 2. REFERENCES 2.1 Applicable Documents The following publications form a part of this document to the extent specified herein. The latest issue of SAE publications shall apply. The applicable issue of other publications shall be th
27、e issue in effect on the date of the purchase order. In the event of conflict between the text of this document and references cited herein, the text of this document takes precedence. Nothing in this document, however, supersedes applicable laws and regulations unless a specific exemption has been
28、obtained. 2.1.1 SAE Publications Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or +1 724-776-4970 (outside USA), www.sae.org. AIR5433 Lubricating Characteristics and Typical Properties of Lubricants Used in Aviation Pro
29、pulsion and Drive Systems AS5780 Specification for Aero and Aero-Derived Gas Turbine Engine Lubricants 2.1.2 ASTM Publications Available from ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959, Tel: 610-832-9585, www.astm.org. ASTM D341 Standard Practice for V
30、iscosity-Temperature Charts for Liquid Petroleum Products SAE INTERNATIONAL ARP6157 Page 4 of 38 2.2 Related Publications The following publications are provided for information purposes only and are not a required part of this SAE Technical Report. Hamrock, B.J. and Dowson, D. “Isothermal Elastohyd
31、rodynamic Lubrication of Point Contacts, Part III Fully Flooded Results”, J. Lubr. Technology, Vol. 99, No. 2, Feb 1977, pp 264-276. Hamrock, B.J., and Dowson, B. “Ball Bearing Lubrication The Elastohydrodynamic of Elliptical Contacts”, Willey, 1981. 3. APPROACH The method described below relies on
32、interference fringe color analysis AChILES (Automatic Chromatic Interferogram Laboratory Evaluation System), a special test machine (WAM) and control software (WAMControl). The test approach requires an accurate measurement of EHD film thickness under controlled surface motion, contact stress and th
33、ermal environment. The controlling parameters for EHD film thickness (hc) are illustrated in Figure 1 for a point contact configuration. Figure 1 - Inlet zone pressure generation and EHD parameters for oil film thickness The WAM test machine configured for optical interferometry is shown in Figure 2
34、. The test configuration consists of a transparent optical disc which is loaded and rotated against a smooth steel ball. The contact is lubricated with the test fluid and operated in pure rolling motion. Partially reflecting optical coatings on the disc allow light interference fringes to form betwe
35、en the ball and disc surfaces. The coatings typically include a thin “spacer layer” of SiO2 which has a refractive index similar to typical oils. A spacer layer of known thickness avoids zero-order fringes where the separation thickness is too small to get sufficient interference of light. The color
36、ed interference fringes are monitored with a microscope and camera. The color of the interference fringes changes when the sepration (oil film thickness, hc) of the ball and disc changes. SAE INTERNATIONAL ARP6157 Page 5 of 38 The optical system captures the interference images and test conditions.
37、Images are processed with the AChILES software from which the central film thickness is derived. Once the film thickness is obtained, the AChILES software calculates a P-V coefficient according to the Hammrock Dowsen equation 1, 2 for isothermal central film thickness. The calibration of the optical
38、 system and method for measurement of EHD film thickness, followed by the calculation of P-V coefficient are described in the sections below. Figure 2 - WAM set up for EHD film thickness measurement Ball and disc specimens are driven with motorized spindlesAir bearingPartially reflecting Cr coating
39、and SiO2spacer layer for ultra-thin film measurementsSAE INTERNATIONAL ARP6157 Page 6 of 38 4. REQUIRED HARDWARE 4.1 WAM machine with driven ball optics capability. 4.1.1 114.3 mm (4.5 inch) diameter, 1.588 mm (0.625 inch) thick, Tempered Pyrex 7740 disc with optical coatings on Side A and Side B, s
40、ee Figure 3. 4.1.2 Side A: Anti-reflecitive MgF2 coating. 4.1.3 Side B: Partially reflective Cr, followed by 200 nm thick SiO2 layer, 5 mm wide radial strip with Cr only. Figure 3 - Space layer optical disc and Grade 10 M50 ball 4.2 20.64 mm (13/16 inch) diameter Grade 10 or better M50 ball with 6.4
41、8 mm (0.255 inch) through-hole, see Figure 3. 4.3 Optical disc clamp washer (to secure disc), see Figure 4. 4.4 3/8 inch-24X3/4 Flat head bolt (to secure disc), see Figure 4. 4.5 Modified precision shoulder bolt (to secure ball), see Figure 4. 4.6 Fiber optic cable bushing (for microscope), see Figu
42、re 4. Figure 4 - Disc bolt, washer, ball bolt and fiber optic cable bushing SAE INTERNATIONAL ARP6157 Page 7 of 38 4.7 Driven ball optics disc sump assembly, see Figure 5. WAM10 sump shown, others are similar. Figure 5 - Disc sump assembly 4.8 Driven ball optics nosepiece adaptor, see Figure 6. WAM1
43、0 adaptor shown, others are similar. Figure 6 - Driven ball optics nosepiece adaptor SAE INTERNATIONAL ARP6157 Page 8 of 38 4.9 Driven ball optics assembly, see Figure 7. WAM9 assembly shown, others are similar. Figure 7 - Driven ball optics assembly 4.10 2.38 mm (3/32 inch) ID 5.56 mm (7/32 inch) O
44、D translucent high temperature silicone rubber tubing and inline PVDF (2) micron filter, 135 C (275 F) capability, 6.35 mm ( inch) tube fitting, see Figure 8. Figure 8 - Silicone tubing and inline oil filter SAE INTERNATIONAL ARP6157 Page 9 of 38 4.11 Mituyo Microscpe with 5X and 10X objectives, see
45、 Figure 9. Microscope shown, others similar. Figure 9 - Microscope with 5X and 10X objectives 4.12 Microscope adaptor plate for attaching microscope to XY slide, see Figure 10. WAM9 plate shown, others similar. Figure 10 - Adaptor plate SAE INTERNATIONAL ARP6157 Page 10 of 38 4.13 Microscope XY slid
46、e assembly, see Figure 11. WAM9 slide shown, others are similar. Figure 11 - XY microscope slide 4.14 Digital camera and lens, see Figure 12. WAM9 camera shown, others are similar. Figure 12 - Digital camera and lens SAE INTERNATIONAL ARP6157 Page 11 of 38 4.15 Camera power supply, see Figure 13. Fi
47、gure 13 - Camera power supply 4.16 Light Source and fiber optic cable, see Figure 14. Figure 14 - Light source and fiber optic cable 4.17 RGB Video Cable and Null modem cable, see Figure 15. Figure 15 - RGB and Null modem cables SAE INTERNATIONAL ARP6157 Page 12 of 38 4.18 Monochromatic filter, see
48、Figure 16. Figure 16 - Monochromatic (red) filter 5. TEST PROCEDURE 5.1 Specimen Cleaning and Storage Ball and disc specimens are cleaned ultrasonically before installation on the machine. Ball and disc sumps are simply rinsed/flushed with solvent prior to installation to ensure minimal debris conta
49、mination and the removal of visible oil films. While testing a series of oils, it is impractical and unnecessary to remove the sumps and specimens for cleaning. In that case, the ball and disc are wiped clean with solvent and a lab wipe until no visible oil films exist. The ball sump and disc sump are flushed with solvent and then with clean test oil into a waste oil container in preparation for the testing of
