1、Designation: F38 00 (Reapproved 2014)Standard 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 revision.
2、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 measuring th
3、eamount 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 indica
4、tor.1.2 The values stated in SI units are to be regarded asstandard. 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 establish app
5、ro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2A193/A193M Specification for Alloy-Steel and StainlessSteel Bolting for High Temperature or High PressureService and Other Special Purpose Applicat
6、ionsB637 Specification for Precipitation-Hardening and ColdWorked Nickel Alloy Bars, Forgings, and Forging Stockfor Moderate or High Temperature ServiceD3040 Practice for Preparing Precision Statements for Stan-dards Related to Rubber and Rubber Testing (Withdrawn1987)3F104 Classification System for
7、 Nonmetallic Gasket Materi-als2.2 ASTM Adjuncts:Relaxometer, Method A (F38)4Relaxometer, Method B (F38)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 InTest MethodA, normally run a
8、t room temperature, 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
9、 are then plotted against 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 le
10、ngth ofthe calibrated 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
11、 and their ability 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 b
12、e correlated with field 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 materials1These test methods are under the jurisdiction of ASTM Committee F03 onGaskets and are the direct re
13、sponsibility of Subcommittee F03.20 on MechanicalTest Methods.Current edition approved March 1, 2014. Published April 2014. Originallyapproved in 1962. Last previous edition approved in 2006 as F38 00 (2006). DOI:10.1520/F0038-00R14.2For referenced ASTM standards, visit the ASTM website, www.astm.or
14、g, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.4Aprint of this apparatus is available at a
15、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.Copyright ASTM International
16、, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1and at issuance substantiating data were not available for other gasketmaterials.5. Apparatus5.1 Test Method A:5.1.1 Strain Indicator.5.1.2 Timer.5.1.3 Relaxometer,4composed of two platens, upper andlower; a bolt,
17、with mounted strain gauge; and a thrust bearingas shown in Fig. 1.5.1.4 Strain Gauges,6120 resistance with a gauge factorof 2.0 6 0.10 %. The gauges shall be mounted to indicatetensile strain and positioned to compensate for torque,temperature, and bending. The gauges shall be mounted on thesmall di
18、ameter of the 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,5composed of two platens, special drilledand calibrated bolt, washer and nut composed of SpecificationA193/A193M Grade B7 or Specification B637 Grade UNSN
19、07718 or other alloys of construction that would satisfy thecalibration procedure (see Annex) for the test temperaturespecified, and a dial indicator assembly as shown in 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 insid
20、e 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 be 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) sur-face ar
21、ea may also be used. A size of 15.62-mm (0.615-in.)inside diameter by 43.56-mm (1.715-in.) outside diameter isrecommended.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 spe
22、cimen shall be 0.8 mm(0.03 in.) unless otherwise agreed upon between the consumerand the producer. ForType 4 materials 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 C
23、lassification 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 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
24、Conduct the test at 20 to 30C (70 to 85F) unlessotherwise specified.8.1.4 Disassemble the relaxometer and place the 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 sli
25、ghtly,by hand, or just enough to hold the specimen in place duringsubsequent handling. Mount the head of the bolt in a clamp.8.1.5 Hook up and balance the strain indicator. Record thereading. Then set the reading on the strain indicator for the6The sole source of supply of strain gauges (TypeAB-7) k
26、nown to the committeeat this time is Baldwin-Lima-Hamilton. If you are aware of alternative suppliers,please provide this information to ASTM International Headquarters. Your com-ments will receive careful consideration at a meeting of the responsible technicalcommittee,1which you may attend.FIG. 1
27、Relaxometer, Test Method AF38 00 (2014)2specified 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 by tightening the nut with asolid wrench until the strain indicator reaches a balance. Ato
28、rque 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 is called the “initial stress.”8.1.7 Beginning at the time of “initial stress,” take stra
29、inindicator 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. (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 pape
30、r against the log of time in hours.8.2 Test Method B:8.2.1 Clean all surfaces and lightly lubricate the washer andbolt 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
31、they are no closer than2 mm (0.078 in.) to the other pieces and the edge of the platens.If an annular specimen is 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 th
32、e 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,finger 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 unt
33、il the desired dial indicator reading isreached. Record the reading (D0). Apply the stress in onecontinuous motion with a maximum loading time of 3 s.Aboltelongation 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 asse
34、mbly. (The calibration procedure isoutlined in Annex A1.)NOTE 2When testing materials thicker than 0.8 mm (0.03 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
35、 h at 100 6 2C (212 6 3.6F), unless otherwisespecified. The maximum test temperature for SpecificationA193/A193M Grade B7 shall not exceed 204.4C (400F) andthe maximum test temperature for Specification B637 GradeUNS N07718 shall not exceed 482.2C (900F).78.2.7 Remove from the oven and cool to room
36、temperature.8.2.8 Replace the dial indicator assembly, finger tight, andset the dial indicator at the zero reading. Loosen the nut,without disturbing the dial indicator assembly, and record thedial reading (Df).8.2.9 Calculate the percentage relaxation as follows:Relaxation, % 5D02 Df! / D0#3100 (1)
37、9. Report9.1 Report the following information:9.1.1 Identification and designation number of the materialtested,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 th
38、e results recorded in 9.1.5.7Some 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 as the alloy meets the calibration standard for the desired test temperature.FIG. 2 Relaxometer and Dial Indi
39、cator Assembly, Test Method BF38 00 (2014)310. Precision and Bias810.1 These precision and bias statements have been pre-pared in accordance with Practice D3040. Please refer to thispractice for terminology and other testing and statisticalconcept explanations.10.2 Seven laboratories tested the foll
40、owing five gasketmaterials (Classification F104 material designations) for creeprelaxation: Type 1, Class 1; Type 1, Class 2; Type 5, Class 1;Type 7, Class 1; Type 7, Class 2. Test Method B, Type 1conditioning was used by all laboratories. Rectangular testspecimens were prepared from gasket sheets b
41、y cutting themwith the long dimension in the machine direction. Tests wereconducted in accordance with Test Methods F38, 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 tests were conducted for 22
42、 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 A193/A193M Grade B7 Fixture are given in Table 1.10.4 Additional F38 Round Robin test data regarding theevaluation of Specification B637 UNS N07718
43、 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 PurposeA1.1.1 To precondition (
44、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 test temperatures.A1.1.3 To ensure
45、 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 with 5.2.1, modified sothat each pl
46、aten 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 applied load.A1.2.4 Calibration Appar
47、atus, 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 of 0.13 6 0.0013 mm (0.00500 6 0.
48、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 from8Supporting data have been filed at ASTM I
49、nternational Headquarters and maybe obtained by requesting Research Report RR:F03-1009.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 between two individual test results based on a 95 % confidence level, 522 sCVd.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
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