1、Designation: D 7559/D7559M 09Standard Test Method forDetermining Pressure Decay of Inflatable RestraintCushions1This standard is issued under the fixed designation D 7559/D7559M; the number immediately following the designation indicates theyear of original adoption or, in the case of revision, the
2、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 retain air pressure
3、 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 method should not b
4、e 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 independently o
5、f 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 safety and health
6、practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D 123 Terminology Relating to TextilesE 691 Practice for Conducting an Interlaboratory Study toDetermine the Precision of a Test MethodD 6799 Terminology Relating to Inflatabl
7、e Restraints3. Terminology3.1 For all terminology relating to D13.20, Inflatable re-straints, refer to Terminology D 6799.3.1.1 The following terms are relevant to this standard:deployment; inflatable restraint.3.2 For all other terms related to textiles, see TerminologyD 123.4. Summary of Test Meth
8、od4.1 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 teststand tha
9、t 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 by the p
10、urchaserand supplier.5. Significance and Use5.1 This test method may be used for product developmentand design, production validation, manufacturing process con-trol, lot acceptance, or for a combination thereof.5.2 The rate of inflation in this method does not attempt tomimic that of an actual cush
11、ion 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 cushion infl
12、ators. 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 testmethod does
13、 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 on thed
14、esign 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, 2009. Published August 2009.2For referenced ASTM sta
15、ndards, 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.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken,
16、 PA 19428-2959, United States.applied. It is the responsibility of the supplier and / orpurchaser to determine if the parameters under which a cushionis tested will be destructive and render the cushion unfit forfuture use5.4 Within the limits of variance expressed in Section 12,this test method is
17、useful for design and production validationand may be suitable for incorporation in a cushion specificationor for lot acceptance testing of commercial shipments.6. Apparatus6.1 Air Supply Source, capable of filling the cushion to thespecified pressure, with a flow rate capable of maintaining thespec
18、ified 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 sourceshould be equipped with an inline filter, shut off valve, and flowregulator. Care should be taken to trap out excess moisture
19、 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 of allowing a sealed attach-ment of the cushion to the air supply source, the shut off valve,and instrumentation to monitor the press
20、ure 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 sufficient safety shielding and isolation foroperator protection during the test. The clamping device thatattaches the opening of the cus
21、hion 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 Tube, mounted coaxially inside filling tube of themounting fixture. One end should extend inside the cushion atminimum of 25 mm (1 i
22、n.) 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 pressure transducer or gauge. The end that extends into thecushion should be oriented such that it allows free expansion ofthe cushion g
23、eometry.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 accuracy of a maximumof +/- 2%.6.6 Pressure Gauge, suitable for measuring pressures insidethe cushion (via the pickup tube) from 0 to
24、 at least 200 kPa (0to 29 PSI) and maintained to an accuracy of a maximum of +/-2%.6.7 Data Acquisition System, suitable for recording theoutput of the pressure transducer versus elapsed time. Theinput amplifier and the time interval at which the data isrecorded must have an accuracy of +/- 1%. It i
25、s 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 time. This must have an accuracy of61%.6.9 Filter requirements, data sampling rate, transducer fre-quency response, and
26、 amplifier frequency response shall besuch that the overall accuracy of the data acquisition systemshall be within 6 1%. The significant figures of the recordeddata of time and pressure, along with the timing incrementshould be agreed upon by the purchaser and supplier.7. Sampling7.1 The Cushion Pre
27、ssure 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 determination of lot size and sampling plan shall beagreed to by purchaser and supplier.7.3 One cushion assembly is a tes
28、t 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 gages that are traceable to the NationalInstitute of Science and Technology (NIST) or other nationalstandards laboratory. Th
29、e test parameters of the equipmentshall be tested within the operating ranges covered in thecushion specification or equivalent document.9. Conditioning9.1 Conditioning of specimens and conducting of thetesting in the standard atmosphere for testing textiles isdesirable, but not required. It is reco
30、gnized that conditions ofthe air from the compressed air source used to inflate thespecimen will not be controlled, even though care should betaken to filter the air and trap out any excessive moisture orcompressor oils.9.2 Testing can be conducted in, or specimens conditionedin an environment other
31、 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 any relevant customer or supplierspecifications.10. Procedure10.1 Select and condition specimens in accordance withSectio
32、ns 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 and sealed, and that the pickuptube does not interfere with the inflation of the cushion. If thecushion contains an inter
33、nal 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 any necessary information, such as cushionserial number, lot number, and style, and ensure that the dataacquisition system
34、 is ready.10.5 Open the shut-off valve and adjust the flow regulatorsuch that the specimen slowly inflates over a minimum oftypically 10 s. The specimen should then be inflated to apressure slightly exceeding the specified starting point pres-sure, but not to exceed a level of 2% above that of the s
35、tartingpoint, or 1.5 kPa (0.22 PSI), which ever is greater. ThisD 7559/D7559M 092pressure should be held at equilibrium for a minimum of 0.5second, but not to exceed a maximum 10 s.10.6 Close the shut off valve. When the pressure drops tothe specified starting pressure, data collection will begin, a
36、ndthis 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 ofthe test scheme10.8 Safely bleed any residual air pressure from the speci-men. Remove the specimen from the test stan
37、d.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 collected by observing amechanical pressure gauge and stopwatch type timer andrecording the data manually. This may be usefu
38、l 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 apply if this optionalprocedure is used.11. Report11.1 State that the tests were conducted in accordance withthis test m
39、ethod.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 accordance withASTM D7559, with the following changes:”11.2 The purchaser and supplier shall determine the exactform of the
40、 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 report.11.2.5 Relevant supplier or purchaser specification if any.11.2.6 Parameters of the test and data obtained to includ
41、e: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 from standard procedures and apparatus.12. Precision and Bias12.1 The output data of this method are pressure and time.T
42、he 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 Sections6.5-6.8.12.2 The analysis of precision of test results using this testmethod is meaningful both within-laboratory and bet
43、ween-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 pressures used in this study, asimulated cushion surrogate was constructed. The test deviceconsisted of a sealed steel
44、tank of volume approximating thatof a typical cushion, a hose of appropriate internal diameter toact as the neck of the cushion and facilitate 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
45、 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 most common customerspecification. An orifice of 2.38 mm (3/32 in.) diameter waschosen to simulate a bag with moderate to worse performancethat would typicall
46、y be marginal or not meet most commonFIG. 1 Test SchemeD 7559/D7559M 093customer specifications. A variety of starting pressures andtimes were chosen to encompass the range of common speci-fications in the industry. Data was processed using ASTME691 adjunct software package.12.4 See Data Table (Fig.
47、 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 Practice E 691:ThisStudyPractice E 691MinimumLaboratories: 4 6Materials 4 4Determinations: 5 212.5.1 Precision, character
48、ized 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 precision statements are provisional.Within five years, additional data will be obtained and pro-cessed which does meet t
49、he 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 from 70 kPa 51.47 0.4666 0.694 1.304 1.942Good Performer from 100 kPa 78.21 0.813 2.071 2.275 5.710Moderate Performer from 70 kPa 31.98 0
