1、Designation:D647608 Designation: D6476 12Standard Test Method forDetermining Dynamic Air Permeability of Inflatable RestraintFabrics1This standard is issued under the fixed designation D6476; the number immediately following the designation indicates the year oforiginal adoption or, in the case of r
2、evision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers the procedures used to determine under dynamic airflow conditions the hig
3、h pressure permeabilityof permeable, uncoated fabrics typically used for inflatable restraints. For the determination of air permeability of inflatablerestraint fabrics under low pressure conditions at steady-state air flow, refer to Test Method D737.1.2 Procedures and apparatus other than those sta
4、ted in this test method may be used by agreement of purchaser and supplierwith the specific deviations from the standard acknowledged in the report.1.3The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in eachsystem are not exact equ
5、ivalents; therefore, each system must be used independently of the other.1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.4 This standard does not purport to address all of the safety concerns, if any, associated with its
6、 use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D123 Terminology Relating to TextilesD737 Test Method for Air Permeability
7、of Textile FabricsD1776 Practice for Conditioning and Testing TextilesD2904 Practice for Interlaboratory Testing of a Textile Test Method that Produces Normally Distributed DataD6799 Terminology Relating to Inflatable RestraintsE691 Practice for Conducting an Interlaboratory Study to Determine the P
8、recision of a Test Method3. Terminology3.1 For all terminology relating to D13.20, Inflatable restraints, refer to Terminology D6799.3.1.1 The following terms are relevant to this standard: average dynamic air permeability (ADAP), dynamic air permeability(DAP), cushion, exponent of dynamic air perme
9、ability (EXP, ) inflatable restrain, inflator, module, standard atmosphere for testingtextiles3.2 For all other terms related to textiles, see Terminology D123.4. Summary of Test Method4.1 A volume of dessicated compressed air at known volume and pressure passes through a fabric specimen into the st
10、andardatmosphere for testing textiles. During the portion of the test cycle which simulates airbag inflation, the pressure differentialpressure across the specimen rises to a value corresponding to a peak inflation pressure. During the portion of the test cycle whichsimulates airbag deflation, the p
11、ressure differential drops to 0 kPa as the air passes through the specimen. The time to reach themaximum pressure and the subsequent time to correspond to similar times in an airbag deployment.4.2 Software algorithms integral to the apparatus smooth out the pressure data and determine the values for
12、 ADAP and EXP.1This test method is under the jurisdiction of ASTM Committee D13 on Textiles and is the direct responsibility of Subcommittee D13.20 on Inflatable Restraints.Current edition approved July 1, 2008.2012. Published July 2008.August 2012. Originally approved in 2000. Last previous edition
13、 approved in 20052008 asD647605.D647608. DOI: 10.1520/D6476-08.10.1520/D6476-12.2For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. ForAnnual Book ofASTM Standardsvolume information, refer to the standards Document Summary page on t
14、he ASTM website.1This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users
15、consult prior editions as appropriate. In all cases only the current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.5. Significance and Use5.1 For
16、matters relating to lot acceptance of commercial shipments and conformity to specification or other standard, refer toSection 13 of this test method.5.2 This test method is useful in the selection and design validation of permeable, uncoatable fabrics used in inflatable restraintcushions. The dynami
17、c conditions and higher pressure differentials of this test method may better simulate the inflation anddeflation cycle of an airbag module during deployment than do the steady-state conditions of Test Method D737.5.2.1 Only uncoated, permeable fabrics should be used. Use of coated fabrics may yield
18、 invalid results and potentially damagethe test apparatus.5.3 Within the limits of variance expressed in Section 12, this test method is useful for design validation and may be suitablefor incorporation in a material specification or for lot acceptance testing of commercial shipments. Caution is adv
19、ised on very lowpermeability fabrics or with the 200 cm3. size test heat because between-laboratory precision as presented in Section 12 may beas high as 21 %.5.4 This test method may be used for materials other than inflatable restraint fabrics which experience dynamic air permeabilityin sudden bur
20、sts. In such cases, the physical apparatus or its software algorithms may require modification to provide suitabilityfor use.5.5 Due to the split-second time interval for testing, the pressure versus time data is subject to recording anomalies andelectronic noise. The data should be digitally filter
21、ed to obtain the underlying smooth pressure curve prior to data analysis. Thesoftware in the apparatus includes a reliable algorithm both to smooth the curve and to determine the exponent of air permeability.5.6 It is inherent in the design and operation of this equipment that major components key t
22、o the calibration and measurementsare specific to the individual test head. The size or permeability measuring range of the test head is typically chosen to correspondto the fabric specimen to be tested. The precision of this test method is highly dependent on the size of the test head. The precisio
23、nof the data collected using one test head should be used to estimate the precision of data collected using a different test head, evenon the same apparatus.5.7 It is mandatory that fabric specimens be conditioned and tested in standard atmosphere for testing textiles.6. Apparatus6.1 Removable Test
24、Head, containing a Pressure Vessel of known volume capable of being charged pneumatically from 0 to noless than 400 kPa (0 to no less than 58 psi) with a tolerance of 6 3.0 %, of sufficient volume to challenge adequately the fabricbeing tested, equipped with a solenoid release valve mechanism, a tes
25、t chamber, and a circular orifice with an area of 50 cm2; andequipped with a means of measuring and adjusting the pressure range in increments of 1 kPa (0.1 psi), kPa, a minimum rangebetween pressure set points of 5 kPa (1 psi) and rise and fall ranges in ms sufficient to meet the conditions of a ma
26、terialspecification for dynamic air permeability testing of inflatable restraint fabrics.6.2 Pressure Transducers and Rigid Wall Pickup Tubes, suitable for measuring the pressure differential of the fabric specimenin a range sufficient to meet the conditions of a material specification for dynamic a
27、ir permeability testing of inflatable restraintfabrics, with a tolerance of 6 2 %, mounted in a static or low pressure area in the test fixture that does not interfere with airflow.6.3 Air Compressor and Air Desiccating Cartridge, capable of charging the pressure vessel in the test head to the speci
28、fiedpressure up to 400 kPa.6.4 Mounting Fixture, capable of retaining the fabric specimen over the test orifice without stretching the specimen and withoutair leakage at the periphery of the test area.6.5 Electrical Firing Pulse Source, suitable for actuating the inflation and for communicating with
29、 the data acquisition systemdependent on an electrical signal.6.6 Data Acquisition System, suitable for recording the output of the pressure transducers versus elapsed time of airflow.6.7 Filter Requirements, data sampling rate, transducer frequency response, and amplifier frequency response shall b
30、e such thatminimal effect on accuracy of the data occurs. The accuracy of the pressure transducers, amplifiers, and timers within the testapparatus shall be calibrated to within 6 3%.7. Sampling7.1 Dynamic air permeability testing is a destructive test and therefore necessitates sampling procedures
31、if used in conjunctionwith lot acceptance of commercial shipments.7.2 Lot Sample:7.2.1 For acceptance testing, the lot size is the quantity of fabric finished in one production day or as agreed upon between thepurchaser and the supplier.7.2.2 Unless otherwise agreed upon between the purchaser and th
32、e supplier, take as a lot sample all the rolls in a commercialshipment. Consider the rolls to be the primary sampling units.7.3 Laboratory Sample7.3.1 An entire roll of fabric or a full-width cut from the end of a roll within a lot sample constitutes a laboratory sample.7.4 Test Specimens:7.4.1 Test
33、 specimens are the pieces of fabric that actually undergo testing. Cut or mark specimens from the end of each roll offabric in the laboratory sample, as indicated in the material specification or equivalent. Cut 165mm165 by 330 mm rectangularD6476 122specimens from the full-width fabric sample, or m
34、ark similarly sized areas across the full-width fabric sample without cuttingindividual specimens.7.4.2 If areas of full width fabric are tested without cutting individual specimens, position test areas representing a broaddistribution across the length and width, preferably along the diagonal of th
35、e laboratory sample, and no nearer the edge than onetenth its width.8. Conditioning8.1 Precondition test specimens in accordance with Practice D1776 or as agreed upon between the the purchaser and thesupplier.8.2 Prior to testing, bring the test specimens to moisture equilibrium at ambient atmospher
36、ic pressure, at 21 6 1C (70 62F),1C, and at 65 6 2 % relative humidity, unless directed to do otherwise by an agreement by the purchaser and supplier.8.3 Equilibrium is considered to have been reached when the increase in mass of the specimen in successive weighings madeat intervals of not less than
37、 2 h does not exceed 0.1 % of the mass of the specimen.9. Procedure9.1 Select and condition specimens in accordance with 8.1.9.2 Mount the fabric specimen on the test fixture, ensuring that the retention mechanism clamps the fabric tightly with minimaltension and without damage or wrinkling.9.3 Perf
38、orm all system calibrations.9.4 Enter the specimen number into recording portions of the data acquisition.9.5 Ensure the pressure vessel is pressurized with desiccated air to a pressure sufficiently high to test the specimen within thepressure ranges specified.9.6 In accordance with the applicable m
39、aterial specification or laboratory guideline, select and install the appropriate test headfor the fabric type to be measured.9.7 Preset the start, upper, and lower pressure limits.9.7.1 Unless otherwise stated in the customer specification, the test head size, and starting pressure should be select
40、ed such thatan average peak pressure of 100 6 10 kPa is reached during the test. Also unless otherwise stated in the customer specification,the Lower Limit should be set to 30 kPa and the Upper Limit should be set to 70 kPa.9.8 Establish data acquisition system response to pressure inputs.9.9 Initia
41、te the starting sequence and note the response of the data acquisition system to verify successful airflow.9.10 Record maximum differential pressure in kPa (psi),kPa, time to maximum pressure in ms, or whatever data points arerequired by the material specification.9.11 Remove the specimen from the t
42、est stand and mark it as having been tested.9.12 On the test report, record the data required by the material specification.NOTE 1The unit of permeability commonly used for ADAP measurement is mm/s. A velocity of 1 mm/s is the mathematical equivalent of apermeability of 0.1 cm3/(cm2.s). Permeability
43、 and velocity are considered interchangeable terms.10. Equipment Calibration10.1 For inflatable restraints, all test equipment used in accordance with these test methods shall be certified for calibrationannually by an independent agency or equipment manufacturer whose results are traceable to the N
44、ational Institute of Science andTechnology (NIST) or other national standards laboratory. The test parameters of the equipment shall be tested within the operatingranges covered in the material specification or equivalent document.11. Report11.1 State that the tests were conducted in accordance with
45、 this test method for determining the dynamic air permeability ofinflatable restraints fabrics.11.1.1 If deviation from this test method occurred, any reference to this test method shall state: “Testing was performed inaccordance with ASTM D6476, with the following changes:”11.2 The purchaser and su
46、pplier shall determine the exact form of the test report. Unless otherwise specified, report thefollowing information:11.2.1 Fabric designation,11.2.2 Lot identification,11.2.3 Date of report,11.2.4 Name of person certifying report,11.2.5 Relevant specification,11.2.6 Number of specimens used in eac
47、h test,11.2.7 Tests performed and data obtained,11.2.8 Laboratory conditions if other than standard, and11.2.9 Deviations from standard procedures and apparatus.D6476 12312. Precision and Bias12.1 BiasFor multifilament fabrics such as those used for inflatable restraints, there is no standard refere
48、nce material availableto serve as an accepted standard value for dynamic air permeability testing. In the absence of a known true value, the accuracyof this test method cannot be determined.12.2 The analysis of precision of test results using this test method is meaningful both within-laboratory and
49、 between-laboratorywith multiple operators.12.3 An Interlaboratory Test3was planned and conducted on uncoated fabrics covering a range of permeabilities typically usedin inflatable restraint cushions in accordance with Practice E691 and Practice D2904. For inflatable restraint fabrics, the typicalrange of permeabilities is between zero and 10 cfm when measured in accordance with Test Method D737. Two variables, ADAPand EXPONENT were studied. Analysis was done using SAS 6.1, PROC. GLM, and PROC. VARCOMP. Three components ofvariance - single-operator, within-laboratory, and be
