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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 therefr
2、om, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions. QUESTIONS REGARDING THIS DOCUMENT: (412) 772-8512 FAX: (412) 776-0243 TO PLACE A DOCU
3、MENT ORDER; (412) 776-4970 FAX: (412) 776-0790 Copyright 1997 Society of Automotive Engineers, Inc. All rights reserved.Printed in U.S.A. SURFACE VEHICLE 400 Commonwealth Drive, Warrendale, PA 15096-0001 RECOMMENDED PRACTICE Submitted for recognition as an American National Standard J1619 ISSUED JAN
4、97 Issued1997-01 SINGLE TOOTH GEAR BENDING FATIGUE TEST 1.ScopeThis SAE Recommended Practice defines the set-up and procedure for conducting the SAE Single Tooth Bending Fatigue Test. The details of the test fixture to be used (referred henceforth as “the test fixture” in this document) and gear tes
5、t sample and the procedures for testing and analyzing the data are presented in this document. 1.1PurposeThe objective of this document is to provide a means to evaluate the effects of material and process variables on the bending fatigue behavior of gears using the test fixture. The bending fatigue
6、 life of gear teeth is generally influenced by variations in such factors as geometry, material, microstructure, residual stress profile, surface finish, case depth, surface and core hardness. This test serves as a screening tool to evaluate changes in one or more of these variables to enable optimi
7、zation of the processing and design of gears. 2.References 2.1Applicable PublicationsThe following publications form a part of this specification to the extent specified herein. Unless otherwise specified, the latest issue of SAE publications shall apply. 2.1.1SAE PUBLICATIONAvailable from SAE, 400
8、Commonwealth Drive, Warrendale, PA 15096-0001. SAE J821042Gear Single Tooth Bending Fatigue Test 2.1.2ASTM PUBLICATIONAvailable from ASTM, 100 Barr Harbor Road, West Conshohocken, PA STP-91Staircase Method for Fatigue Experiments 2.1.3AGMA PUBLICATIONAvailable from American Gear Manufacturers Associ
9、ation, 1500 King Street, Suite 201, Alexandria VA 22314-2730. AGMA 2001-B88908-B89 Fundamental Ratio Factors and Calculation Methods for Involute Spur and Helical Gear Teeth 2.1.4OTHER PUBLICATION Statistical Design and Analysis of Engineering Experiments, Lipson and Sheth, “Fatigue Experiments,” pp
10、. 262-275. SAE J1619 Issued JAN97 -2- 3.Test SpecimenThe test uses a specific gear as a test specimen to account for the complex nature of bending and residual stress in a gear after processing and during loading. A straight cut 6-pitch, 34-tooth, 20- degree pressure angle spur gear with no tip reli
11、ef is the recommended test sample (Figures 1A and 1B). Other tooth sizes and profiles are acceptable, depending on specific objectives of the test. 4.Test Fixture 4.1The test fixture design was evaluated and selected by the SAE ISTC Division 33 Gear Metallurgy Committee and validated by a round robi
12、n gear test program. The results of the test machine validation are reported in SAE Publication 821042 (Reference 2.1.1) using a carburized and shot peened SAE 8620 steel gear. Figures 2 and 3 shown the overall views of the fixture set-up. Figures 4 through 13 show the detail drawings of the compone
13、nts of the test fixture. The fixture consists of a base (Figure 4), an upper load anvil (Figure 5), a lower support anvil (Figure 6), and a mandrel or mounting shaft (Figure 7). The fixture is adaptable to a variety of hydraulic cyclic testing machines when positioned between the load platens, provi
14、ded the load is applied to the spherical seat located in the top anvil (Figures 2 and 3). 4.2The replaceable upper anvil insert (Figure 8) (not crowned) loads the test gear at the tooth tip. The replaceable lower anvil insert (Figure 9) (not crowned) resists the load applied through the upper anvil
15、and prevents sample rotation by contacting a support tooth near the base circle. The upper anvil (Figure 5) is mounted on the loading arm (Figure 10) as shown in Figure 11. The fixture base, load anvil and support anvil are aligned by a common shaft (Figure 7). The test gear is mounted on the shaft
16、supported by roller bearings at the ends. The bearing supports are shown in Figure 13. The gear and load anvil rotate in an arc about the gear axis, keeping a single line of contact across the gear tooth during loading. Load is applied to the fixture through a large ball bearing (Figures 2 and 3) to
17、 eliminate misalignment and to keep applied force in line with the loading and support anvils. The complete test assembly is shown in Figure 13. 5.Test Procedure 5.1Gear PreparationOne gear tooth must be removed prior to testing the gear to provide clearance for the support anvil in the tooth root.
18、This is accomplished by carefully grinding away one tooth (Figure 3) taking care not to heat the gear above the tempering temperature. An alternate method is to remove the tooth prior to heat treatment. 5.2Fixture CalibrationIt is recommended that one test gear be strain gaged and used to periodical
19、ly verify the consistency of the test fixture. Wear on the anvil and shaft surfaces will change the loading on the gear tooth and subsequently the root stress. A procedure for preparing a calibration gear using contact strain gages is given in Appendix A. All components are replaceable items. The re
20、commended calibration procedure is estimated to provide a strain measurement precision of 10%. 5.3Test AssemblyThe test gear is first mounted on the shaft, then the support anvil is placed against one tooth root to prevent the gear from rotating. The load anvil is mounted on the same shaft as the ge
21、ar and rotates in an arc around the gear axis. The load anvil contacts a tooth at the end of the active profile across the entire face of the tooth. Care must be taken to avoid corner loading or uneven contract across the face of the test tooth. Figure 13 shows the support anvil contacting the tooth
22、 in the root and the load anvil contacting the tested tooth at the tip. This ensures that a tensile bending stress is applied to the root of the test tooth. Support teeth are not used as tip loaded fatigue test specimens in subsequent tests. Suggested tooth loading scheme is shown in the gear depict
23、ed in Figure 14. SAE J1619 Issued JAN97 -3- FIGURE 1ASPUR GEAR TEST SPECIMEN SAE J1619 Issued JAN97 -4- FIGURE 1BNORMAL RACK PROFILE SAE J1619 Issued JAN97 -5- FIGURE 2TEST FIXTURE ASSEMBLY FIGURE 3CLOSE-UP OF TEST GEAR SET-UP SAE J1619 Issued JAN97 -6- FIGURE 4BASE PLATE SAE J1619 Issued JAN97 -7-
24、FIGURE 5UPPER ANVIL SAE J1619 Issued JAN97 -8- FIGURE 6LOWER ANVIL SAE J1619 Issued JAN97 -9- FIGURE 7MANDREL FIGURE 8INSERT, UPPER ANVIL SAE J1619 Issued JAN97 -10- FIGURE 9INSERT, LOWER ANVIL SAE J1619 Issued JAN97 -11- FIGURE 10LOADING ARM SAE J1619 Issued JAN97 -12- FIGURE 11ARM/ANVIL SUB-ASSEMB
25、LY SAE J1619 Issued JAN97 -13- FIGURE 12BEARING SUPPORT SAE J1619 Issued JAN97 -14- FIGURE 13ASSEMBLY SAE J1619 Issued JAN97 -15- FIGURE 14DIAGRAM OF GEAR SHOWING USABLE TEETH FOR TESTING 5.4LoadingWhen the load anvil is in contact with the tooth root, the test tooth is loaded by having the loading
26、device make contact through the spherical seat located in the upper load anvil (see Figure 5). Single tooth bending fatigue tests are conducted using a constant amplitude cyclic load of 20 to 30 Hz. 5.5TestingA cyclic load pattern with a minimum load magnitude of 10% of the maximum load (R = minimum
27、 load/maximum load = 0.1) is recommended to keep the load anvil in contact with the test tooth and avoid shock loading. Gear teeth are tested until complete tooth fracture is achieved and the load and cycles to fracture are recorded for each tooth. The base of the test fixture is operated on a film
28、of oil to eliminate the transfer of side loads into the tooth and loading device. 5.6Analysis of ResultsThe S-N (Stress versus Cycles) curve is composed of two lines. The finite part of the plot is determined by testing at a minimum of three distinct stress levels. The endurance limit or infinite pa
29、rt of the curve is determined using the Stair Case method described in ASTM STP-91 (Reference 2.1.2). The two curves meet at a point commonly called the “knee.” A method for determining the range of endurance limits based on statistical methods is described in Statistical Design and Analysis of Engi
30、neering Experiments, Lipson and Sheth, “Fatigue Experiments,” pp. 262-275 (Reference 2.1.4). The test provides a guideline for the selection of loads in the finite portion of the curve. A life of 10 million cycles will determine a run-out; any shorter life is a failure. Appendix B provides further d
31、etails of testing scheme and analysis. 5.7Gear Stress EstimationFormulas to calculate the bending stress in the roots of gear teeth are given in AGMA 2001-B88 and 908-B89 (Reference 2.1.3). The load angle of the test fixture is used to calculate the bending stress in gears. To enable a reliable comp
32、arison of results between tests on a given gear geometry, some formulas must be applied consistently for stress calculations. SAE J1619 Issued JAN97 -16- 6.ReportReport results in the form of an endurance curve of stress versus log number of cycles to failure in a semi-log plot with the log cycles t
33、o failure on the X-axis. Important parameters to be reported along with the test results are: a.Gear MaterialSteel grade, chemistry, cleanliness b.Case DepthSurface carbon if applicable c.Carbon gradient and surface carbon d.Case and Core Hardness DataHardness gradient e.Grain Size f.Microstructural
34、Percent retained austenite, presence of any oxides g.Calibration Data h.Finishing method after heat treatment (e.g., shot-peening characterization, details, and grinding process as applicable) i.Residual stress profile as applicable PREPARED BY SAE IRON AND STEEL TECHNICAL COMMITTEE DIVISION 33 GEAR
35、 METALLURGY SAE J1619 Issued JAN97 -17- APPENDIX A STRAIN GAGING A.1Strain GagesConstantan foil alloy, polyamide-backed, self-temperature-compensated strain gages with an active grid length of 0.38 mm (0.015 in) are recommended. Gage resistance is 120 W with a gage factor setting of 2.13 for direct
36、read-out. The gage configuration is a vertical grid with side solder tabs and four 90 degree alignment arrows. A.2Strain Gage PlacementA metal template, shown in Figure A1, having five scribed lines is used to locate three strain gages at the point of maximum bending stress that is determined by the
37、 distance (X) from the tooth tip of the fracture line of a broken tooth. Transparent adhesive tape peeled from the tooth is used to transfer the reference distance (X) from a broken tooth involute surface. Parallel lines (a and b) are scribed on the template and are separated by a distance equal to
38、(X). A centerline is scribed at the center of the tooth width and perpendicular to line b. Two lines such that they are equidistant from the line of the center of the width are scribed perpendicular to line (b) or along with width. FIGURE A1A BROKEN TOOTH AND THE METAL TEMPLATE WITH LINES TO LOCATE
39、TWO STRAIN GAGES ALONG THE WIDTH OF THE TOOTH AT EQUAL DISTANCES FROM THE THIRD ONE AT THE CENTER A.2.1 Alignment arrows on the strain gage backing are used to position each gage over the crossed lines on the template with the aid of a stereobinocular at 25X magnification. Transparent, pressure-sens
40、itive, double faced tape is laid over the gages on the template so that the straight edge of the tape lays on line (a). The tape is rolled on top of the gages being careful not to disturb the alignment. In the case of the test gear used for development of the test, the distance was 10.2 mm. A.2.2 A
41、molded rubber replica of the cavity between adjacity gear teeth is prepared to position the gages in the tooth root. First, a cavity is formed by bridging the end faces of two adjacent teeth with masking tape. Then silicone rubber is poured into the cavity and to a level that covers the tips of the
42、adjacent gear teeth (Figure A2). The rubber replica is removed from the cavity and inverted. The assembly of three strain gages positioned on the template is then transferred to the replica with the edge (a) of the tape laid along the sharp molded corner formed by the tooth tip. SAE J1619 Issued JAN
43、97 -18- FIGURE A2DIAGRAM OF AN INTERTOOTH REPLICA IN A TWO TOOTH CAVITY HAVING SHARP CORNERS A.2.3 Standard cleaning procedures for specific strain gages are recommended for the root fillet before mounting. Catalyst is applied to the strain gages and a typical strain gage m, .adhesive is applied to
44、the root fillet of the cleaned gear tooth. Then the rubber replica with the gage-tape affixed is placed between the teeth and held by finger pressure for 1 min for proper bonding. Figure A3 shows the gages mounted in the tooth root fillet. FIGURE A3PRECISION STRAIN GAGES MOUNTED IN THE TOOTH FILLET
45、SAE J1619 Issued JAN97 -19- APPENDIX B TESTING SCHEME AND ANALYSIS OF DATA PrefaceFollowing is a list of steps that will produce an S/N curve for gear teeth: B.1Finite CurveThe finite part of the S/N curve is the plot from the tensile strength to the knee of the curve. The following steps will deter
46、mine the finite part of the curve: B.1.1 Determine the tensile strength, Su, of the material at the root surface of the test gear teeth. This is easily accomplished by measuring the Rockwell C hardness or microhardness near the roots of gear teeth and calculating the tensile strength based on a hard
47、ness-strength relationship. B.1.2 Test gear teeth at three distinct load levels that will give stress levels given in Table B1 and record test lift. B.1.3 Using statistical methods, calculate the mean of the test life at each of the three distinct load levels. B.1.4 Plot the Load/Mean Life data on S
48、emi-log paper; test life is plotted on the log axis of the paper. B.1.5 Estimate the knee of the S/N plot by extrapolating the load life plot to the load that produces a million cycle life. NOTE Gear teeth lacking a high residual compressive stress or with surface flaws in the root may have the knee
49、 located at 100 000 cycles. (In this case, extrapolate to 100 000 cycles.) B.2Endurance Limit-Staircase Method B.2.1 The load interval for the Staircase Method is 5% of the load estimated in Step 5 of the calculation of the Finite Curve. B.2.2 Begin the Staircase Test at the load level at least four load intervals higher than the estimated knee. B.2.3 If the tooth fails, reduce the load one interval and test the next tooth at the reduced load. B.2.4 If the tooth survives 10 000 000 cycles, suspend the test, call the sample a run-out. Increase the
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