SEDL / STP / STP1023-EB / STP18893S

Creep Behavior of Zircaloy Cladding Under Variable Conditions

Matsuo, Y
Senior researcher, Central Research Institute, Mitsubishi Metal Corporation, Omiya, Saitama,

Pages: 14    Published: Jan 1989

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Abstract

Various creep tests of Zircaloy cladding tubes under variable conditions were conducted to investigate which hardening rule can be applicable for the creep behavior associated with condition changes. The results show that the strain-hardening rule is applicable in general when either the stress or temperature conditions change, provided that a certain amount of creep strain recovery is observed in case of stress drop. In stress reversal conditions, however, “softening” of the material was observed. Strain rate after stress reversal is much higher than that predicted by the strain-hardening rule. Tn this case, the modified strainhardening model, considering a recoverable creep-hardening range together with the strain recovery, predicts the creep behavior well. The applicability of the model is ascertained through a verification test that includes stress reversal, strain recovery, stress changes, and temperature changes.