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Thick aluminum alloy 5083-O has gained wide usage in liquefied natural gas (LNG) tank construction. Fatigue crack growth rate (FCGR) characteristics are described for specimens obtained from 5083-O plate in thickness from about ½ to 7.75 in. Data were obtained from crack propagation gages and compared with data obtained by an ultrasonic technique. Crack growth rate was measured at 75 and -320°F. At -320°F, FCGR appeared to be substantially lower than at 75 °F in the second stage of growth; however, in the accelerated third stage of growth, the FCGR for the two temperatures were similar. Data show that location of specimen in relation to plate thickness can affect crack growth rate, depending on the crack orientation. From crack propagation gage measurements, it was determined that thickness of compact specimens, per se, (1 to 2 in.) had no effect on growth rate.

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