1、Designation: D7559/D7559M 09 (Reapproved 2014)Standard Test Method forDetermining Pressure Decay of Inflatable RestraintCushions1This standard is issued under the fixed designation D7559/D7559M; the number immediately following the designation indicates theyear of original adoption or, in the case o
2、f revision, the year of last revision. A number in parentheses indicates the year of lastreapproval. A superscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method is intended to determine the ability ofan inflatable restraint cushion to ret
3、ain air pressure at elevatedpressures for a specified time interval.1.2 Procedures and apparatus other than those stated in thistest method may be used by agreement of purchaser andsupplier, provided the specific deviations from the standardacknowledged in the report.1.3 The results of this test met
4、hod should not be used topredict the actual internal pressure decay of a cushion during adeployment.1.4 The values stated in either SI units or inch-pound unitsare to be regarded separately as standard. The values stated ineach system may not be exact equivalents; therefore, eachsystem shall be used
5、 independently of the other. Combiningvalues from the two systems may result in non-conformancewith the standard.1.5 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 appro-priate sa
6、fety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D123 Terminology Relating to TextilesE691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodD6799 Terminology Relating
7、 to Inflatable Restraints3. Terminology3.1 For all terminology relating to D13.20, Inflatablerestraints, refer to Terminology D6799.3.1.1 The following terms are relevant to this standard:deployment; inflatable restraint.3.2 For all other terms related to textiles, see TerminologyD123.4. Summary of
8、Test Method4.1 After inflation with air to a specific initial internalpressure, an inflatable restraint cushion is tested to for itsability to retain a specified residual pressure (allowing for somepressure loss) over a specified time period.4.2 An inflatable restraint cushion is mounted onto a test
9、stand that allows for the inflation of the cushion to a specifiedinitial internal pressure. After the air supply is discontinued,instrumentation measures and records internal pressure dropover time.4.3 Cushion internal pressure versus time data is recordedand compared to allowable limits agreed upon
10、 by the purchaserand supplier.5. Significance and Use5.1 This test method may be used for product developmentand design, production validation, manufacturing processcontrol, lot acceptance, or for a combination thereof.5.2 The rate of inflation in this method does not attempt tomimic that of an actu
11、al cushion deployment, nor is it intendedto subject the cushion to the dynamic loads, stress, andtemperatures during such an event. It is also recognized that thecompressed air used for this tests may not leak through thecushion at the same rate as the gas or mixture of gassestypically used in cushi
12、on inflators. Rather this method isintended to give a relative indication of the pressure holdingability of the cushion.5.3 The internal volume and internal design of cushionsvaries greatly. This test method is most useful when comparingdata from cushions of the same design and volume. This testmeth
13、od does not provide any data concerning the volume ofgas leaking from the bag. At certain higher levels of the initialinternal pressure, this test method will irreversibly damage thecushion and change its leakage properties for future testing orfor commercial use. The damage to the bag is dependent
14、on thedesign or shape of a specific bag and the type of coating1This test method is under the jurisdiction of ASTM Committee D13 on Textilesand are the direct responsibility of Subcommittee D13.20 on Inflatable Restraints.Current edition approved July 1, 2014. Published August 2014. Originallyapprov
15、ed as D7559/D7559M-09. Last previous edition approved in 2009 asD7559/D7559M-09. DOI: 10.1520/D7559_D7559M-09R14.2For 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
16、 standards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1applied. It is the responsibility of the supplier and / orpurchaser to determine if the parameters under which a cushionis tested will
17、 be destructive and render the cushion unfit forfuture use5.4 Within the limits of variance expressed in Section 12,this test method is useful for design and production validationand may be suitable for incorporation in a cushion specificationor for lot acceptance testing of commercial shipments.6.
18、Apparatus6.1 Air Supply Source, capable of filling the cushion to thespecified pressure, with a flow rate capable of maintaining thespecified pressure at equilibrium. Typically the pressure usedfor testing the cushion will not exceed 200 kPa 29 psi, norwill the flow exceed 1500 L/min 53 CFM. The air
19、 sourceshould be equipped with an inline filter, shut off valve, and flowregulator. Care should be taken to trap out excess moisture oroil from the compressed air source.6.2 Shut Off Valve, capable of being actuated either manu-ally or remotely by an electrical signal.6.3 Mounting Fixture, capable o
20、f allowing a sealed attach-ment of the cushion to the air supply source, the shut off valve,and instrumentation to monitor the pressure decay during thetest. It should contain a pressure pickup tube. It shall be in anorientation that allows free expansion of the cushion geometry.It should have suffi
21、cient safety shielding and isolation foroperator protection during the test. The clamping device thatattaches the opening of the cushion to the filling tube fixtureshould be designed to properly fit the opening of the cushion,provide a secure mechanical attachment, and prevent gasleakage.6.4 Pickup
22、Tube, mounted coaxially inside filling tube of themounting fixture. One end should extend inside the cushion atminimum of 25 mm 1 in. beyond the clamping device. Theother end should extend through the wall of the filling tube ofthe mounting fixture through a sealed joint, and be connectedto a pressu
23、re transducer or gauge. The end that extends into thecushion should be oriented such that it allows free expansion ofthe cushion geometry.6.5 Pressure Transducer, suitable for measuring pressuresinside the cushion (via the pickup tube) from 0 to at least 200kPa 0 to 29 psi and maintained to an accur
24、acy of a maximumof 62%.6.6 Pressure Gauge, suitable for measuring pressures insidethe cushion (via the pickup tube) from 0 to at least 200 kPa 0to 29 psi and maintained to an accuracy of a maximum of 62%.6.7 Data Acquisition System, suitable for recording theoutput of the pressure transducer versus
25、elapsed time. Theinput amplifier and the time interval at which the data isrecorded must have an accuracy of 61 %. It is optional thatthis system can initiate the filling of the bag and the closure ofthe shut-off valve.6.8 Manual Timer (stopwatch), optional, suitable for manu-ally observing elapsed
26、time. This must have an accuracy of 61%.6.9 Filter requirements, data sampling rate, transducer fre-quency response, and amplifier frequency response shall besuch that the overall accuracy of the data acquisition systemshall be within 61 %. The significant figures of the recordeddata of time and pre
27、ssure, along with the timing incrementshould be agreed upon by the purchaser and supplier.7. Sampling7.1 The Cushion Pressure Decay Test at certain test param-eters and pressures is a destructive test and therefore necessi-tates sampling procedures if used in conjunction with lotacceptance.7.2 The d
28、etermination of lot size and sampling plan shall beagreed to by purchaser and supplier.7.3 One cushion assembly is a test specimen.8. Equipment Calibration8.1 For inflatable restraints, all test equipment used inaccordance with this test method shall be certified for calibra-tion annually using gage
29、s that are traceable to the NationalInstitute of Science and Technology (NIST) or other nationalstandards laboratory. The test parameters of the equipmentshall be tested within the operating ranges covered in thecushion specification or equivalent document.9. Conditioning9.1 Conditioning of specimen
30、s and conducting of the testingin the standard atmosphere for testing textiles is desirable, butnot required. It is recognized that conditions of the air from thecompressed air source used to inflate the specimen will not becontrolled, even though care should be taken to filter the airand trap out a
31、ny excessive moisture or compressor oils.9.2 Testing can be conducted in, or specimens conditionedin an environment other that of the standard atmosphere fortesting textiles, such as in hot or cold conditions. Theseconditions will be agreed upon between the purchaser andsupplier, or as specified in
32、any relevant customer or supplierspecifications.10. Procedure10.1 Select and condition specimens in accordance withSections 7 and 9.10.2 Ensure that the shut off valve is closed and the pressurereading is at 0.10.3 Mount the specimen onto the mounting fixture, ensur-ing that it is securely attached
33、and sealed, and that the pickuptube does not interfere with the inflation of the cushion. If thecushion contains an internal gas guide or heat shield, it isoptional to remove this if it would otherwise interfere with theability to mount the specimen, or the operation of the pick-uptube.10.4 Record a
34、ny necessary information, such as cushionserial number, lot number, and style, and ensure that the dataacquisition system is ready.10.5 Open the shut-off valve and adjust the flow regulatorsuch that the specimen slowly inflates over a minimum ofD7559/D7559M 09 (2014)2typically 10 s. The specimen sho
35、uld then be inflated to apressure slightly exceeding the specified starting pointpressure, but not to exceed a level of 2 % above that of thestarting point, or 1.5 kPa 0.22 psi, which ever is greater. Thispressure should be held at equilibrium for a minimum of 0.5 s,but not to exceed a maximum 10 s.
36、10.6 Close the shut off valve. When the pressure drops tothe specified starting pressure, data collection will begin, andthis point will become time 0 of the specified time interval.10.7 Data collection will continue until the specified timeinterval has elapsed. Fig. 1shows a graphic representation
37、ofthe test scheme10.8 Safely bleed any residual air pressure from the speci-men. Remove the specimen from the test stand.10.9 Review the recorded data to ensure that the necessarydata was successfully acquired.10.10 Optional procedure In lieu of an electronic datacollection system, data can be colle
38、cted by observing amechanical pressure gauge and stopwatch type timer andrecording the data manually. This may be useful only insituations where the pressure drop is relatively slow. If thismethod is utilized, it must be mentioned on the test report. ThePrecision limits listed in Section 12 do not a
39、pply if this optionalprocedure is used.11. Report11.1 State that the tests were conducted in accordance withthis test method.11.1.1 If deviation from this test method occurred, or if theoptional procedure of 10.10 was used, any reference to this testmethod shall state: “Testing was performed in acco
40、rdance withASTM D7559, with the following changes:”11.2 The purchaser and supplier shall determine the exactform of the report. Unless otherwise specified, report thefollowing information:11.2.1 Cushion designation.11.2.2 Lot identification.11.2.3 Date of report.11.2.4 Name of person certifying repo
41、rt.11.2.5 Relevant supplier or purchaser specification if any.11.2.6 Parameters of the test and data obtained to include:initial starting pressure, specified time interval, and residualpressure after the specified time interval.11.2.7 Laboratory conditions, if other than standard.11.2.8 Deviations f
42、rom standard procedures and apparatus.12. Precision and Bias12.1 The output data of this method are pressure and time.The tolerance of the data therefore is the verified accuracy ofthe Pressure Transducer (or gauge) and the time recordingdevice. These should not exceed the limits shown in Sections6.
43、5 6.8.12.2 The analysis of precision of test results using this testmethod is meaningful both within-laboratory and between-laboratory with multiple operators.12.3 An inter-laboratory test was conducted to determineprecision. Since this test method would be destructive to thespecimen at some of the
44、pressures used in this study, asimulated cushion surrogate was constructed. The test deviceconsisted of a sealed steel tank of volume approximating thatof a typical cushion, a hose of appropriate internal diameter toFIG. 1 Test SchemeD7559/D7559M 09 (2014)3act as the neck of the cushion and facilita
45、te attachment to thetest fixture, and an orifice plug to allow for leakage at a fixedrate. Two orifices sizes were used to simulate a range of leakdown rates of the cushion. An orifice of 1.59 mm 1/16 in.diameter was chosen to simulate a bag with reasonably goodperformance that would typically meet
46、most common customerspecification. An orifice of 2.38 mm 3/32 in. diameter waschosen to simulate a bag with moderate to worse performancethat would typically be marginal or not meet most commoncustomer specifications. A variety of starting pressures andtimes were chosen to encompass the range of com
47、mon speci-fications in the industry. Data was processed using ASTME691 adjunct software package.12.4 See Data Table (Fig. 2).12.5 Precision StatementsThe number of laboratories,materials, and determinations in this study DOES NOT meetthe minimum requirements for determining precision pre-scribed in
48、Practice E691:ThisStudyPractice E691MinimumLaboratories: 4 6Materials 4 4Determinations: 5 212.5.1 Precision, characterized by repeatability, Sr,r,andreproducibility, SR, R, has been determined for the materials tobe:12.5.2 Precision Statement for Test Method: Residual kPapressure after 5 s These pr
49、ecision statements are provisional.Within five years, additional data will be obtained and pro-cessed which does meet the requirements of E691.Materials Average SrSRrRGood Performer from 17.5 kPa 10.83 0.461 0.461 1.291 1.291Good Performer from 70 kPa 54.08 0.453 0.790 1.269 2.213Good Performer from 100 kPa 81.56 0.740 1.900 2.071 5.320Moderate Performer from 70 kPa 36.95 0.556 0.758 1.557 2.12212.5.3 Precision Statement for Test Method: Residual kPapressure after 6sMaterials Average SrSRrRGood Performer from 17.5 kPa 9.720 0.492 0.492 1.378 1.378Good Performer
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