ing. Radiography was used to ore fter bending. The ultrainspect the alloys cores, ished fuel elements. as used to determine element core blanks. at ing fatigue tests were performed in the range 1300 to 1500 F, for frequencies of 6 and 60 cpm. Continuous traces of load and strain were made to determine relationships between stress, strain, and lifetime, for lifetimes vithin the range of 10/sup 3/ and 10/sup 5/ cycles. The data obtained indicate that fatigue strength, whether measured in stress, total strain, or plastic strain, is a function of both temperature and frequency. It was found that the relationship between stress and strain varies with cycles of stress reversal, never reaching an equilibrium condition. In addition, the strain behavior of a specimen during stress cycling is not continuous. Strain in the plastic region was found to occur in sudden, steplike increments which are predictable functions of temperature, stress, frequency, and cycles. (auth)