高温強度 ＩＮ７３８ＬＣの高温における多軸ラチェットと非比例繰返し変形のシミュレーション

Abstract

In a previous work, the present authors proposed a new extension of the constitutive model of cyclic plasticity developed by Ohno and Wang, and they verified the extension on the basis of uniaxial ratchetting experiments of 316FR steel at room temperature. The extension is featured by the capability of representing steady-state ratchetting. In this work, the extension is examined further for the validity under nonproportional cyclic loading by simulating the viscoplastic behavior of IN738LC subjected to multiaxial ratchetting, multiaxial cyclic stress relaxation, butterfly-type cyclic straining, and circular cyclic straining with strain hold at 850°C. The original Ohno and Wang model and the Armstrong and Frederick model are also examined. It is shown that the extension enables us to simulate accurately the multiaxial viscoplastic behavior mentioned above, and that if neither ratchetting nor mean stress relaxation under cyclic loading is significant the three models provide nearly the same predictions as one another.