1、Designation: F38 00 (Reapproved 2014)F38 18Standard Test Methods forCreep Relaxation of a Gasket Material1This standard is issued under the fixed designation F38; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the year of last rev
2、ision.Anumber in parentheses indicates the year of last reapproval.Asuperscriptepsilon () indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the U.S. Department of Defense.1. Scope1.1 These test methods provide a means of measur
3、ing the amount of creep relaxation of a gasket material at a predeterminedtime after a compressive stress has been applied.1.1.1 Test Method ACreep relaxation measured by means of a calibrated strain gauge on a bolt.1.1.2 Test Method BCreep relaxation measured by means of a calibrated bolt with dial
4、 indicator.1.2 The values stated in SI units are to be regarded as standard. The values given in parentheses are for information only.1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to est
5、ablish appropriate safety safety, health, and healthenvironmental practices and determine theapplicability of regulatory limitations prior to use.1.4 This international standard was developed in accordance with internationally recognized principles on standardizationestablished in the Decision on Pr
6、inciples for the Development of International Standards, Guides and Recommendations issuedby the World Trade Organization Technical Barriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2A193/A193M Specification forAlloy-Steel and Stainless Steel Bolting for HighTemperature or
7、High Pressure Service and OtherSpecial Purpose ApplicationsB637 Specification for Precipitation-Hardening and Cold Worked NickelAlloy Bars, Forgings, and Forging Stock for Moderateor High Temperature ServiceD3040 Practice for Preparing Precision Statements for Standards Related to Rubber and Rubber
8、Testing (Withdrawn 1987)3F104 Classification System for Nonmetallic Gasket MaterialsF436/F436M Specification for Hardened Steel Washers Inch and Metric Dimensions2.2 ASTM Adjuncts:Relaxometer, Method A (F38)4Relaxometer, Method B (F38)53. Summary of Test Methods3.1 In both test methods the specimen
9、is subjected to a compressive stress between two platens, with the stress applied by a nutand bolt.3.2 In Test Method A, normally run at room temperature, the stress is measured by a calibrated strain gauge on the bolt. Inrunning the test, strain indicator readings are taken at intervals of time, be
10、ginning at the loading time, to the end of the test. Thestrain indicator readings are converted to percentages of the initial stress which are then plotted against the log of time in hours.The percentage of initial stress loss or relaxation can be read off the curve at any given time, within the lim
11、its of the total test time.1 These test methods are under the jurisdiction ofASTM Committee F03 on Gaskets and are the direct responsibility of Subcommittee F03.20 on Mechanical Test Methods.Current edition approved March 1, 2014Aug. 1, 2018. Published April 2014November 2018. Originally approved in
12、 1962. Last previous edition approved in 20062014as F38 00 (2006).(2014). DOI: 10.1520/F0038-00R14. 10.1520/F0038-18.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to
13、the standards Document Summary page on the ASTM website.3 The last approved version of this historical standard is referenced on www.astm.org.4 A print of this apparatus is available at a nominal cost from ASTM International Headquarters. Order Adjunct No. ADJF003801. Original adjunct produced in 19
14、65.5 Detailed working drawings of this apparatus are available from ASTM International Headquarters. Order Adjunct No. ADJF003802. Original adjunct produced in 1965.This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have b
15、een made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official docume
16、nt.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States13.3 In Test Method B, run at room or elevated temperatures, the stress is determined by measuring the change in length of thecalibrated bolt with a dial indicator. The bolt length is
17、measured at the beginning of the test and at the end of the test; from thisthe percentage of relaxation is calculated.4. Significance and Use4.1 These test methods are designed to compare related materials under controlled conditions and their ability to maintain agiven compressive stress as a funct
18、ion of time. A portion of the torque loss on the bolted flange is a result of creep relaxation.Torque loss can also be caused by elongation of the bolts, distortion of the flanges, and vibration; therefore, the results obtainedshould be correlated with field results. These test methods may be used a
19、s a routine test when agreed upon between the consumerand the producer.NOTE 1Test Method B was developed using asbestos gasket materials and at issuance substantiating data were not available for other gasket materials.5. Apparatus5.1 Test Method A:5.1.1 Strain Indicator.5.1.2 Timer.5.1.3 Relaxomete
20、r,4composed of two platens, upper and lower; a bolt, with mounted strain gauge; and a thrust bearing as shownin Fig. 1.5.1.4 Strain Gauges,6120 resistance with a gauge factor of 2.0 6 0.10 %. The gauges shall be mounted to indicate tensilestrain and positioned to compensate for torque, temperature,
21、and bending. The gauges shall be mounted on the small diameter ofthe bolt about 50.8 mm (2 in.) from the head. The bolt with mounted strain gauges must be calibrated.5.2 Test Method B:5.2.1 Relaxometer, Platen Assembly5composed of two platens, specialspecially drilled and calibrated bolt, washer and
22、 nutcomposed of Specification A193/A193M Grade B7 or Specification B637 Grade UNS N07718 or other alloys of construction thatwould satisfy the calibration procedure (see Annex) for the test temperature specified, and a dial indicator assembly as shown inFig. 2.5.2.2 Dial Indicator Assembly, composed
23、 of an adaptor body, floating pin, set screw, and dial indicator, as shown in Fig. 2. Dialindicator should have graduations of 0.0025 mm (0.0001 in.) or smaller.5.2.3 Box End Wrench. Wrench916 in., Qty. 2.6 The sole source of supply of strain gauges (Type AB-7) known to the committee at this time is
24、 Baldwin-Lima-Hamilton. If you are aware of alternative suppliers, pleaseprovide this information to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of the responsible technical committee,1 whichyou may attend.FIG. 1 Relaxometer, Test Method AF38 1826.
25、Test Specimen6.1 Test Method AThe sample size shall be 33.02 6 0.05 mm (1.300 6 0.002 in.) in inside diameter and 52.32 6 0.05 mm(2.0606 0.002 in.) in outside diameter.6.2 Test Method B:6.2.1 Specimen size shall be 10.16 6 0.381 mm (0.400 6 0.015 in.) wide by 31.75 6 0.381 mm (1.250 6 0.015 in.) lon
26、g. Fourspecimens are required per test.6.2.2 An annular specimen with 1290-mm2 (2.0-in.2 ) surface area may also be used. A size of 15.62-mm (0.615-in.) insidediameter by 43.56-mm (1.715-in.) outside diameter is recommended.6.2.3 For Type 4 Class 2 materials, specimen size shall be one continuous le
27、ngth of 152.4 mm (6.0 in.).6.3 A minimum of three tests shall be conducted.6.4 Nominal thickness of specimen shall be 0.8 mm (0.03 in.) unless otherwise agreed upon between the consumer and theproducer. For Type 4 materials the nominal thickness of the specimen shall be no greater than 1.78 mm (0.07
28、 in.).7. Conditioning7.1 Condition cut specimens in accordance with their classification as required in Classification F104.8. Procedure8.1 Test Method A:8.1.1 Clean all surfaces, platens, and specimen free of wax, mold release, and oils. (Remove with isooctane or other suitablesolvent.) Lubricate b
29、olt threads.8.1.2 Use an initial stress of 13.8 6 0.3 MPa (2000 6 50 psi) unless otherwise specified.8.1.3 Conduct the test at 20 to 30C (70 to 85F) unless otherwise specified.8.1.4 Disassemble the relaxometer and place the specimen between platens. The inside diameter of the specimen should benearl
30、y concentric with the inside diameter of the platens. Screw on the nut and thrust bearing and tighten very slightly, by hand,or just enough to hold the specimen in place during subsequent handling. Mount the head of the bolt in a clamp.8.1.5 Hook up and balance the strain indicator. Record the readi
31、ng. Then set the reading on the strain indicator for the specifiedinitial stress. (The microinches that are added to the above reading will vary the stress and the strain gauge bolt calibration.)FIG. 2 Relaxometer Relaxometer, Platen Assembly and Dial Indicator Assembly, Test Method BF38 1838.1.6 Ap
32、ply stress to the gasket by tightening the nut with a solid wrench until the strain indicator reaches a balance. A torqueof approximately 30 Nm (22 lbfft) is required for a compressive force of 17.8 kN (4000 lbf). The stress should be applied atuniform rate such that at the end of 10 6 2 s the speci
33、fied stress is reached. This is called the “initial stress.”8.1.7 Beginning at the time of “initial stress,” take strain indicator readings at intervals of 10 s, 1 min, 6 min, 30 min, 1 h, 5h, 24 h, etc., or until the end of the test. (Check the zero of the strain indicator after the test.)8.1.8 Con
34、vert the strain indicator readings of 8.1.7 to a percentage of “initial stress.” Then plot this percentage on semilog paperagainst the log of time in hours.8.2 Test Method B:8.2.1 Clean all surfaces and lightly lubricate the washer and bolt threads; graphite and molybdenum disulfide have been foundt
35、o be acceptable lubricants.8.2.2 Place rectangular specimens between the platens in accordance with Fig. 2 and making sure they are no closer than 2 mm(0.078 in.) to the other pieces and the edge of the platens. If an annular specimen is used, center the specimen around the bolt holebetween the plat
36、ens. If a Type 4 Class 2 specimen is used, center the specimen around the bolt hole between the platens, beingcertain that the two ends overlap by a minimum of 6.35 mm (0.25 in.).8.2.3 Place the washer in position and screw on the nut, finger tight.8.2.4 Screw on the dial indicator assembly, finger
37、tight, and set the dial indicator at the zero reading.8.2.5 Apply stress to the specimens by tightening the nut with a wrench until the desired dial indicator reading is reached.Record the reading (D0). Apply the stress in one continuous motion with a maximum loading time of 3 s. A bolt elongation o
38、f0.1222 to 0.1270 mm (0.00481 to 0.00500 in.) is typical for a compressive force of 26.7 kN (6000 lbf). Remove the dial indicatorassembly. (The calibration procedure is outlined in Annex A1.)NOTE 2When testing materials thicker than 0.8 mm (0.03 in.), the time to tighten the nut may be extended to 5
39、 s maximum to allow for the longerarc required to apply the test load.8.2.6 Place the specimen unit in a hot air-circulating oven for 22 h at 100 6 2C (212 6 3.6F), unless otherwise specified. Themaximum test temperature for Specification A193/A193M Grade B7 shall not exceed 204.4C (400F) and the ma
40、ximum testtemperature for Specification B637 Grade UNS N07718 shall not exceed 482.2C (900F).78.2.7 Remove from the oven and cool to room temperature.8.2.8 Replace the dial indicator assembly, finger tight, and set the dial indicator at the zero reading. Loosen the nut, withoutdisturbing the dial in
41、dicator assembly, and record the dial reading (Df).8.2.9 Calculate the percentage relaxation as follows:Relaxation,%5D02Df! /D 0#3100 (1)9. Report9.1 Report the following information:9.1.1 Identification and designation number of the material tested,9.1.2 Test temperature,9.1.3 Length of the test, i
42、n hours,9.1.4 “Initial stress” used, and the specimen thickness,9.1.5 Percentage stress loss for each specimen, and7 Some laboratories have found Alloy A-286 meets the calibration standard at temperatures up to 482.2C (900F). The user may specify any alloy of construction as longas the alloy meets t
43、he calibration standard for the desired test temperature.TABLE 1 Precision of Creep Relaxation Test of Gasket Materials, Using Coefficient of Variation Method of Presenting ResultsNOTE 1S = standard deviation.CV = % coefficient of variation = (S 100) (average).LSD = % least significant difference be
44、tween two individual test results based on a 95 % confidence level, 522sCVd.NOTE 2An annular specimen can be used in place of rectangular specimens for Type 1, Class 2; Type 5, Class 1; Type 7, Class 1; and Type 7, Class 2.An annular specimen cannot be used in place of rectangular specimens for Type
45、 1, Class 1 because of the statistically significant difference in results.Material Type andClass, ClassificationF104Relaxation Values, % Repeatability ReproducibilityRange Average S CV, % LSD, % S CV, % LSD, %Type 1, Class 1 11.515.4 13.3 1.22 9.4 26.5 1.58 11.9 33.7Type 1, Class 2 27.233.7 30.9 1.
46、87 6.2 17.6 2.52 8.2 23.1Type 5, Class 1 4.08.9 6.3 1.27 18.1 51.2 2.01 31.9 90.1Type 7, Class 1 14.224.5 18.1 1.33 8.0 22.7 3.93 21.8 61.5Type 7, Class 2 20.728.5 26.0 0.97 4.2 11.8 3.10 11.9 33.7F38 1849.1.6 Average of all the results recorded in 9.1.5.10. Precision and Bias810.1 These precision a
47、nd bias statements have been pre-pared in accordance with Practice D3040. Please refer to this practicefor terminology and other testing and statistical concept explanations.10.2 Seven laboratories tested the following five gasket materials (Classification F104 material designations) for creeprelaxa
48、tion: Type 1, Class 1; Type 1, Class 2; Type 5, Class 1; Type 7, Class 1; Type 7, Class 2. Test Method B, Type 1 conditioningwas used by all laboratories. Rectangular test specimens were prepared from gasket sheets by cutting them with the long dimensionin the machine direction. Tests were conducted
49、 in accordance with Test Methods F38, Test Method B, with an initial stress of 20.68MPa (3000 psi) applied on a 1290-mm2 (2-in.2) sample area, total of 26.7-kN (6000-lb) compressive force. The tests wereconducted for 22 h at 100C (212F). The tests were conducted in triplicate on each material using the A193 Grade B7 Fixture.10.3 The precision results for the Specification A193/A193M Grade B7 Fixture are given in Table 1.10.4 Additional F38 Round Robin test data regarding the evaluation of Specification B637 UNS N07718 is provided inAppendix
