Nine of the bottles were wound according to the

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Nine of the bottles were wound according to the specification, with hoop termination at the tangent line between the cylindrical and dome regions (Figs. 25 and 26) for both hoop layers. The other three bottles were wound with a simulated manufacturing discontinuity. Here, varying amounts of the second or outer hoop layer were left off one end of the 101.6 mm (4.00 in.) long cylindrical region. The first of these, bottle 5-7, was wound with hoop reversal 5.1 mm (0.20 in.) short of the tangent line; bottle 8-8 had hoop reversal 10.2 mm (0.40 in.) short of the tangent; and bottle 15-17 was wound 15.2 mm (0.60 in.) short. Another purpose of these tests was to determine the effect of temperature on burst pressure. Hence, three of the vessels were tested at 0 ° C (32 ° F), three at 21.1 ° C (70 ° F) and three at 43.3 ° C (110 ° F). All three of the bottles with the abbreviated hoop layers were tested at the 21.1 ° C (70 ° F) room temperature baseline. Two other variables were added to the tests to increase the information output from the acoustic emission test data. First, two different transducer configurations were investigated. Four of the bottles were monitored using all four acoustic emission transducers, two mounted on the polar bosses and two on the domes. The remaining eight bottles were tested with only the two polar boss mounted transducers. The second additional variable was the pressurization scheme. Here two different schemes were used: (1) a load-hold-unload pattern similar to that used in acoustic emission proof testing of full-scale pressure vessels 17 and rocket motor cases 27,31 (Fig. 27) and (2) a simple ramp to failure in accordance with ASTM D 2585. 30 Six of the bottles were 384 Acoustic Emission Testing F IGURE 25. Fiberglass epoxy test bottle measuring 146 mm (5.75 in.). Dome region helical fibers Polar boss Polar boss Cylindrical region hoop fibers Hoop fibers Longitudinal stress Hoop stress F IGURE 26. Acoustic emission transducer placement for the 146 mm (5.75 in.) diameter bottles. 1 2 3 4 F IGURE 27. Hydrostatic proof test pressurization of 146 mm (5.75 in.) diameter bottles. 20 (290) 16 (232) 12 (174) 8 (116) 4 (58) 0 Pressure, MPa (10 –3 lb f ·in. –2 ) Time (s) 240 s 240 s 240 s 200 400 600 800 1000 A A A B Legend A = 69 kPa·s –1 (10 lb f ·in. –2 ·s –1 ) B = 138 kPa·s –1 (20 lb f ·in. –2 ·s –1 ) = pressurization = simultaneous pressurization and acoustic emission
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tested with each of the two schemes. The solid lines in Fig. 27 indicate pressurization and acoustic emission test data being considered simultaneously, whereas the broken or dashed lines indicate pressurization data only. Historically, some of the thinking behind the load-hold-unload pressurization scheme has been to measure the felicity effect 27,32 and to research the creep behavior during the hold periods. 16,26,27,31 In this case, the two different loading sequences were used to observe the bottles at different loading rates and load levels. The low pressure ramp holds were also designed to see if the acoustic emission test data would provide meaningful results at about 25 percent of the anticipated burst pressure and whether or not the additional proof cycle provided by the
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  • Fall '19
  • Fighter aircraft, Nondestructive testing, Acoustic Emission, Acoustic Emission Testing

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