1、Designation: F 38 00 (Reapproved 2006)Standard Test Methods forCreep Relaxation of a Gasket Material1This standard is issued under the fixed designation F 38; the number immediately following the designation indicates the year of originaladoption or, in the case of revision, the year of last revisio
2、n. A number in parentheses indicates the year of last reapproval. A superscriptepsilon (e) indicates an editorial change since the last revision or reapproval.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 These test methods provide a means of measuring
3、theamount of creep relaxation of a gasket material at a predeter-mined time after a compressive stress has been applied.1.1.1 Test Method ACreep relaxation measured by meansof a calibrated strain gauge on a bolt.1.1.2 Test Method BCreep relaxation measured by meansof a calibrated bolt with dial indi
4、cator.1.2 The values stated in SI units are to be regarded as thestandard. The values given in parentheses are for informationonly.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establi
5、sh appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2A 193/A 193M Specification for Alloy-Steel and StainlessSteel Bolting Materials for High Temperature or HighPressure Service and Other Specia
6、l Purpose ApplicationsB 637 Specification for Precipitation-Hardening Nickel Al-loy Bars, Forgings, and Forging Stock for High-Temperature ServiceD 3040 Practice for Preparing Precision Statements forStandards Related to Rubber and Rubber Testing3F 104 Classification System for Nonmetallic Gasket Ma
7、te-rials2.2 ASTM Adjuncts:Relaxometer, Method A (F 38)4Relaxometer, Method B (F 38)53. Summary of Test Methods3.1 In both test methods the specimen is subjected to acompressive stress between two platens, with the stress appliedby a nut and bolt.3.2 In Test MethodA, normally run at room temperature,
8、 thestress is measured by a calibrated strain gauge on the bolt. Inrunning the test, strain indicator readings are taken at intervalsof time, beginning at the loading time, to the end of the test.The strain indicator readings are converted to percentages ofthe initial stress which are then plotted a
9、gainst the log of timein hours. The percentage of initial stress loss or relaxation canbe read off the curve at any given time, within the limits of thetotal test time.3.3 In Test Method B, run at room or elevated temperatures,the stress is determined by measuring the change in length ofthe calibrat
10、ed bolt with a dial indicator. The bolt length ismeasured at the beginning of the test and at the end of the test;from this the percentage of relaxation is calculated.4. Significance and Use4.1 These test methods are designed to compare relatedmaterials under controlled conditions and their ability
11、tomaintain a given compressive stress as a function of time. Aportion of the torque loss on the bolted flange is a result ofcreep relaxation. Torque loss can also be caused by elongationof the bolts, distortion of the flanges, and vibration; therefore,the results obtained should be correlated with f
12、ield results.These test methods may be used as a routine test when agreedupon between the consumer and the producer.NOTE 1Test Method B was developed using asbestos gasket materialsand at issuance substantiating data were not available for other gasketmaterials.5. Apparatus5.1 Test Method A:5.1.1 St
13、rain Indicator.1These test methods are under the jurisdiction of ASTM Committee F03 onGaskets and are the direct responsibility of Subcommittee F03.20 on MechanicalTest Methods.Current edition approved Oct. 1, 2006. Published December 2006. Originallyapproved in 1962. Last previous edition approved
14、in 2000 as F 38 00.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3Withdrawn.4Aprint of this apparatus is av
15、ailable at a nominal cost fromASTM InternationalHeadquarters. Order Adjunct No. ADJF003801. Original adjunct produced in 1965.5Detailed working drawings of this apparatus are available from ASTMInternational Headquarters. Order Adjunct No. ADJF003802. Original adjunctproduced in 1965.1Copyright ASTM
16、 International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5.1.2 Timer.5.1.3 Relaxometer,4composed of two platens, upper andlower; a bolt, with mounted strain gauge; and a thrust bearingas shown in Fig. 1.5.1.4 Strain Gauges,6120 V resistance with a gauge fac
17、torof 2.0 6 0.10 %. The gauges shall be mounted to indicatetensile strain and positioned to compensate for torque, tem-perature, and bending. The gauges shall be mounted on thesmall diameter of the bolt about 50.8 mm (2 in.) from the head.The bolt with mounted strain gauges must be calibrated.5.2 Te
18、st Method B:5.2.1 Relaxometer,5composed of two platens, specialdrilled and calibrated bolt, washer and nut composed ofSpecification A 193/A 193M Grade B7 or Specification B 637Grade UNS N07718 or other alloys of construction that wouldsatisfy the calibration procedure (see Annex) for the testtempera
19、ture specified, and a dial indicator assembly as shownin Fig. 2.5.2.2 Box End Wrench.6. Test Specimen6.1 Test Method AThe sample size shall be 33.02 60.05 mm (1.300 6 0.002 in.) in inside diameter and 52.32 60.05 mm (2.0606 0.002 in.) in outside diameter.6.2 Test Method B:6.2.1 Specimen size shall b
20、e 10.16 6 0.381 mm (0.400 60.015 in.) wide by 31.75 6 0.381 mm (1.250 6 0.015 in.) long.Four specimens 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.)inside diameter by 43.56-mm (1.715-in.) outside diameter isrecomm
21、ended.6.2.3 For Type 4 Class 2 materials, specimen size shall beone continuous length 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 consumerand the producer. For Type 4 materi
22、als the nominal thickness ofthe specimen shall be no greater than 1.78 mm (0.07 in.).7. Conditioning7.1 Condition cut specimens in accordance with their clas-sification as required in Classification F 104.8. Procedure8.1 Test Method A:8.1.1 Clean all surfaces, platens, and specimen free of wax,mold
23、release, and oils. (Remove with isooctane or othersuitable solvent.) Lubricate bolt threads.8.1.2 Use an initial stress of 13.8 6 0.3 MPa (2000 650 psi) unless otherwise specified.8.1.3 Conduct the test at 20 to 30C (70 to 85F) unlessotherwise specified.8.1.4 Disassemble the relaxometer and place th
24、e specimenbetween platens. The inside diameter of the specimen shouldbe nearly 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 duringsubsequent handling. Mount the head of the bolt
25、in a clamp.8.1.5 Hook up and balance the strain indicator. Record thereading. Then set the reading on the strain indicator for thespecified initial stress. (The microinches that are added to theabove reading will vary the stress and the strain gauge boltcalibration.)8.1.6 Apply stress to the gasket
26、by tightening the nut with asolid wrench until the strain indicator reaches a balance. Atorque of approximately 30 Nm (22 lbfft) is required for acompressive force of 17.8 kN (4000 lbf). The stress should beapplied at uniform rate such that at the end of 10 6 2 s thespecified stress is reached. This
27、 is called the “initial stress.”6The sole source of supply of strain gauges (Type AB-7) known to thecommittee at this time is Baldwin-Lima-Hamilton. If you are aware of alternativesuppliers, please provide this information to ASTM International Headquarters.Your comments will receive careful conside
28、ration at a meeting of the responsibletechnical committee,1which you may attend.FIG. 1 Relaxometer, Test Method AF 38 00 (2006)28.1.7 Beginning at the time of “initial stress,” take strainindicator readings at intervals of 10 s, 1 min, 6 min, 30 min,1 h, 5 h, 24 h, etc., or until the end of the test
29、. (Check the zeroof the strain indicator after the test.)8.1.8 Convert the strain indicator readings of 8.1.7 to apercentage of “initial stress.” Then plot this percentage onsemilog paper against the log of time in hours.8.2 Test Method B:8.2.1 Clean all surfaces and lightly lubricate the washer and
30、bolt threads; graphite and molybdenum disulfide have beenfound to be acceptable lubricants.8.2.2 Place rectangular specimens between the platens inaccordance with Fig. 2 and making sure they are no closer than2 mm (0.078 in.) to the other pieces and the edge of the platens.If an annular specimen is
31、used, center the specimen around thebolt hole between the platens. If a Type 4 Class 2 specimen isused, center the specimen around the bolt hole between theplatens, being certain that the two ends overlap by a minimumof 6.35 mm (0.25 in.).8.2.3 Place the washer in position and screw on the nut,finge
32、r tight.8.2.4 Screw on the dial indicator assembly, finger tight, andset the dial indicator at the zero reading.8.2.5 Apply stress to the specimens by tightening the nutwith a wrench until the desired dial indicator reading isreached. Record the reading (D0). Apply the stress in onecontinuous motion
33、 with a maximum loading time of 3 s. A boltelongation of 0.1222 to 0.1270 mm (0.00481 to 0.00500 in.) istypical for a compressive force of 26.7 kN (6000 lbf). Removethe dial indicator assembly. (The calibration procedure isoutlined in Annex A1.)NOTE 2When testing materials thicker than 0.8 mm (0.03
34、in.), thetime to tighten the nut may be extended to 5 s maximum to allow for thelonger arc required to apply the test load.8.2.6 Place the specimen unit in a hot air-circulating ovenfor 22 h at 100 6 2C (212 6 3.6F), unless otherwisespecified. The maximum test temperature for SpecificationA 193/A 19
35、3M Grade B7 shall not exceed 204.4C (400F)and the maximum test temperature for Specification B 637Grade 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, andset the dial indicator at the zero re
36、ading. Loosen the nut,without disturbing the dial indicator assembly, and record thedial reading (Df).8.2.9 Calculate the percentage relaxation as follows:Relaxation, % 5 D02 Df!/ D0# 3 100 (1)9. Report9.1 Report the following information:9.1.1 Identification and designation number of the materialte
37、sted,9.1.2 Test temperature,9.1.3 Length of the test, in hours,9.1.4 “Initial stress” used, and the specimen thickness,9.1.5 Percentage stress loss for each specimen, and9.1.6 Average of all the results recorded in 9.1.5.10. Precision and Bias810.1 These precision and bias statements have been pre-p
38、ared in accordance with Practice D 3040. Please refer to thispractice for terminology and other testing and statisticalconcept explanations.10.2 Seven laboratories tested the following five gasketmaterials (Classification F 104 material designations) for creeprelaxation: Type 1, Class 1; Type 1, Cla
39、ss 2; Type 5, Class 1;Type 7, Class 1; Type 7, Class 2. Test Method B, Type 1conditioning was used by all laboratories. Rectangular test7Some laboratories have found Alloy A-286 meets the calibration standard attemperatures up to 482.2C (900F). The user may specify any alloy of constructionas long a
40、s the alloy meets the calibration standard for the desired test temperature.8Supporting data have been filed at ASTM International Headquarters and maybe obtained by requesting Research Report RR: F03-1009.FIG. 2 Relaxometer and Dial Indicator Assembly, Test Method BF 38 00 (2006)3specimens were pre
41、pared from gasket sheets by cutting themwith the long dimension in the machine direction. Tests wereconducted in accordance with Test Methods F 38, Test MethodB, with an initial stress of 20.68 MPa (3000 psi) applied on a1290-mm2(2-in.2) sample area, total of 26.7-kN (6000-lb)compressive force. The
42、tests were conducted for 22 h at 100C(212F). The tests were conducted in triplicate on each materialusing the A193 Grade B7 Fixture.10.3 The precision results for the Specification A 193/A 193M Grade B7 Fixture are given in Table 1.10.4 Additional F 38 Round Robin test data regarding theevaluation o
43、f Specification B 637 UNS N07718 is provided inAppendix X1.11. Keywords11.1 creep relaxation; deflection; gasket material; platens;relaxometer; strain; stress; temperature; torque bolt; torque lossANNEX(Mandatory Information)A1. TEST METHOD B CREEP RELAXATON APPARATUS: BOLT CALIBRATION PROCEDUREA1.1
44、 PurposeA1.1.1 To precondition (strain relieve) the bolts at elevatedtemperature prior to calibration.A1.1.2 To calibrate the bolts after preconditioning, and on aperiodic basis after use. Bolts used at temperatures greater than205C (401F) should be recalibrated more often than boltsused at lower te
45、st temperatures.A1.1.3 To ensure that the bolt is functioning properly.Should the calibration of a bolt result in an elongation of lessthan 0.114 mm (0.00450 in.) or more than 0.140 mm(0.00550 in.) at 26.7 kN (6000 lbf), the bolt should bediscarded.A1.2 ApparatusA1.2.1 Relaxometer, in accordance wit
46、h 5.2.1, modified sothat each platen can accept a pair of steel dowel pins.A1.2.2 Spacer, washer-shaped, 0.80 6 0.13 mm (0.031 60.005 in.) thick.A1.2.3 Tensile Testing Machine, capable of obtaining andrecording a load of 26.7 kN (6000 lbf). The maximumallowable system error equals 0.5 % of the appli
47、ed load.A1.2.4 Calibration Apparatus, to connect the relaxometerto the tensile machine. See Fig. A1.1.A1.3 ProcedureA1.3.1 If the bolts to be calibrated are new, they must bepreconditioned using the following procedure. Assemble therelaxometer without gaskets. Load the bolt to obtain a deflec-tion o
48、f 0.13 6 0.0013 mm (0.00500 6 0.00005 in.) and recordthis value as the original deflection. Place the fixture in acirculating air oven preheated to 50F above the intendedmaximum test temperature.After 22 h, remove the fixture fromthe oven, cool to room temperature, and remove the load fromthe bolt,
49、measuring the deflection to the nearest 0.0013 mm(0.00005 in.). Record this deflection as the final deflection.Repeat this cycle until the original and final deflection differ bya value that does not show a trend to decrease further from onecycle to the next. Typically, the bolts will stabilize at 3 % orless difference between the original and final deflection.NOTE A1.1Normally, seven cycles or less are sufficient to precondi-tion bolts.A1.3.2 with the steel washer in place of the gasket, andtighten the nut only finger tight. Mount the fixture in thecalibra
