Abstract
The ability of the constitutive model to simulate the ratcheting behavior of metastable austenitic stainless steel S30408 is significant to ensure the safety of the liquefied natural gas (LNG) semi-trailer tanks in the lightweight process of the inner containers. This is because the lightweight inner vessels often encounter cyclic stresses due to the road inertia loads together with high mean stresses due to internal pressures. In this study, we performed cryogenic uniaxial tension experiments and a series of ratcheting experiments to investigate the cyclic plasticity behavior of the metastable austenitic stainless steel S30408. Based on the Ohno-Wang II model, we proposed a new cyclic plasticity constitutive model with martensitic transformation, which relates the content of deformation-induced martensite with isotropic hardening and kinematic hardening. The ratcheting behaviors of S30408 were first simulated by the proposed model with the incremental loading method using MATLAB. The results showed that the model could reasonably predict the ratcheting behavior of S30408, and the evolution law of martensite content could well predict the content of deformation-induced martensite. Under the assumption of the von Mises yield criterion and normal plasticity flow rule, we developed a numerical algorithm of plastic strain with the proposed model to implement the finite element calculation of the model. Internal iteration in the numerical algorithm was implemented with the Euler backward method, which calculated the trial strain for each equilibrium iteration using the consistent tangent matrix. With a user subroutine, the proposed model was programmed into ANSYS for a user - executable version. By simulating the uniaxial ratcheting of a S30408 round bar, we found that the calculated results were in good agreement with the experimental results, which promises further applications in the design of structures, such as LNG semi-trailer tanks.
Highlights
With excellent plasticity and toughness, S30408 austenitic stainless steel (type 304 stainless steel in American Iron and Steel Institute (AISI) materials designation) is often employed in the inner containers of liquefied natural gas (LNG) semi-trailer tanks [1]
By simulating the uniaxial ratcheting of a S30408 round bar, we found that the calculated results were in good agreement with the experimental results, which promises further applications in the design of structures, such as LNG semi-trailer tanks
Based on the Ohno-Wang II model, the content of martensite is related to the isotropic hardening and kinematic hardening of materials, and we propose a constitutive model that can reasonably describe the martensitic transformation induced by S30408 at cryogenic temperatures
Summary
In order to improve the prediction of ratcheting strain of materials in the constitutive model, Halama [19] modified the model proposed by Abdel-Karim and Ohno, and embedded the cyclic hardening/softening characteristics of materials and additional hardening caused by non-proportional load into the Abdel-Karim model. Chen et al [20] introduced the evolution rule of function φ(p) and the parameter μi of material cyclic hardening or softening characteristics into the superposition model of the Ohno-Wang II model and A-F model, and improved the prediction effect of strain cyclic and uniaxial ratcheting strain. Based on the Ohno-Wang II model, the content of martensite is related to the isotropic hardening and kinematic hardening of materials, and we propose a constitutive model that can reasonably describe the martensitic transformation induced by S30408 at cryogenic temperatures. Constitutive model to predict the uniaxial ratcheting strain of the specimen
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