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| CONSTITUTIVE MODEL OF LOW TEMPERATURE RATCHETING EFFECT OF S30408 |
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Abstract S30408 austenitic stainless steel is widely used to make the inner container of LNG and other cryogenic tanker due to its excellent mechanical properties and low temperature resistance. The inner container of this type of tank can not only bear constant stress caused by internal pressure, but also bear alternating stress caused by inertial load at its supporting part, which is prone to gradual plastic strain accumulation, i.e. ratcheting.However, there is still a lack of constitutive description to effectively predict the low temperature ratcheting effect of S30408. The ratcheting strain of low temperature S30408 austenitic stainless steel is simulated by sevseral more advanced constitutive models. It is found that this several constitutive models have the the disadvantages of low-prediction in the early cycles and over-prediction in the late cycles. And this difference will increase with the number of cycles. Based on the Ohno-Wang II model, this paper associates deformation martensite content with isotropic and kinematic hardening rule, and gives the evolution rule of martensite limit content dL, and then proposes a cyclic plastic constitutive model containing martensite transformation. The dL of the martensite limit content in this paper can better describe the variation rule of martensite limit value with the accumulated plastic strain. Through the simulation of low temperature S30408 austenitic stainless steel by sevseral more advanced constitutive models and the new constitutive model, it is found that the model can effectively improve the situation that the predicted value is too low in the initial cycles, and can also well describe the situation that the material reaches ratchet stability in the later cycles.
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Received: 20 December 2019
Published: 28 October 2020
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2020, Vol. 41 
