EXPERIMENTATION, ANALYSIS AND PREDICTION FOR ENVIRONMENTAL CREEP
MARTIN CO BALTIMORE MD
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An investigation was made of experimental means for characterizing the creep behavior of an Al alloy 7075-T6 for a simple environment during which metallurgical changes would occur, and of means for predicting the behavior under an arbitrary time-temperature-stress environment. Slight overaging a strength loss of 5 greatly magnified the environmental creep rate. A recovery mechanism was also observed. A transient creep stage was manifested for each reapplication of load which diminished for subsequent cycles and combinations of either high stress and high temperature or low stress and low temperature. Excellent reproducibility of an arbitrary test environment was possible when the repeat test specimens were selected from adjoining positions in the sheet. A method was developed that made possible the prediction of environmental creep behavior for an arbitrary test condition during which overaging at 350 F took place and, subsequently, when creep resistance was restored as the result of some aging mechanism.