ASTM D4846-96(R2021) pdf free download

ASTM D4846-96(R2021) pdf free download.Standard Test Method for Resistance to Unsnapping of Snap Fasteners
5. Significance and Use
5.1 This test method may be used for acceptance testing of commercial shipments of snap fasteners, but caution is advised since information on between laboratory precision is incom- plete. Comparative tests as directed in 5.1.1 are advisable. 5.1.1 In case of a dispute arising from differences in reported test results when using Test Method D4846 for acceptance testing ofcommercial shipments, the purchaser and seller should conduct comparative tests to determine if there is statistical bias between their laboratories. Competent statistical assistance is recommended for the investigation of bias. As a minimum, the two parties should take a group of test speci- mens that are as homogeneous as possible and that are from a lot of material of the type in question. The test specimens then should be assigned randomly in equal numbers to each laboratory for testing. The average results from the two laboratories should be compared using Student’s t-test for unpaired data and an acceptable probability level chosen by the two parties before testing is begun. If a bias is found, either its cause must be found and corrected or the purchaser and seller must agree to interpret future test results in the light of the known bias.
6. Apparatus
6.1 Tensile Testing Machine—A constant rate of extension (CRE) type or constant rate of traverse (CRT) type testing machine conforming to Specification D76/D76M with a rate of traverse of305 mm (12 in.)/min, or a rate agreed upon between purchaser and seller, and a scale which will produce accurate results at very low force levels. There may be no overall correlation between the results obtained with the CRE and CRT tensile testing machines. In the case of controversy, however, the CRE method shall prevail. 6.2 Jaws—The back jaws of the clamps on the tensile testing machine should be at least the same width as the front jaws. The front jaws must be 25.4 mm (1 in.) wide. 6.3 Aluminum Plate—A plate is required measuring 50 mm by 100 mm by 4 mm (2 in. by 4 in. by 1 ⁄ 8 in.) with dowel pins inserted (see Fig. 1). 6.4 Attaching Machine—A hand operated, foot operated, or automatic machine for attaching snap fastener parts conform- ing to specifications of seller.
7. Sampling
7.1 LotSample—As a lot sample for acceptance testing, take at random the number of shipping cartons of snap fasteners or shipping cartons of garments directed in an applicable material specification or other agreement between the purchaser and the seller. Consider shipping cartons of snap fasteners or shipping cartons of garments to be the primary sampling units. N OTE 1—An adequate specification or other agreement between the purchaser and the seller requires taking into account the variability between shipping cartons, units within a shipping carton, and between specimens from a unit within a shipping carton, to provide a sampling plan with a meaningful producer’s risk, consumer’s risk, acceptable quality level, and limiting quality level. 7.2 Laboratory Sample—As a laboratory sample for accep- tance testing, proceed as follows: 7.2.1 Unattached Snap Fasteners—Take one box or card of unattached snap fasteners at random from each shipping carton in the lot sample. If the male and female parts are packed separately, take one box of each from each shipping carton in the lot sample. 7.2.2 Attached Snap Fasteners—Take one garment from each shipping carton in the lot sample. 7.3 Test Specimens: 7.3.1 Unattached Snap Fasteners—From each box or card in the laboratory sample, take five snap fasteners at random. If the male and female parts are packed separately, for each pair of boxes from a shipping carton in the lot sample, take five male parts at random and match them with five female parts taken at random. 7.3.2 Attached Snap Fasteners—From each garment in the laboratory sample, take five snap fasteners at random on garments with more than five. If less than five, take all snap fasteners from each garment.