Simplified constitutive model of austenitic stainless steel at high temperatures

Based on completed experimental data and constitutive models, we proposed the simplified constitutive model of austenitic S30408 (AISI304) stainless steel at high temperatures. According to continuous trial calculation and analysis fined that the simplified constitutive model can be divided into two segments. In the first segment, the Ramberg-Osgood model (R-O model) was adopted, while the second segment was represented using a straightline expression. Next, simplified constitutive model was obtained by nonlinear fitting using Matlab. Based on this, FEA models were created, incorporating the simplified constitutive model, refined constitutive model, and constitutive model fitted based on experimental data from other literature. Using the sequential thermmechanical coupling analysis method, the FEA of the fire-resistant performance of three specimens including simply supported stainless steel rectangular beam, restrained rectangular stainless steel column and restrained stainless steel H-section columns, was carried out and compared. The conclusions drawn were as follows: For members at low temperatures, when the strain value is small, the deformation and force calculated using simplified constitutive model is not much different from that using the constitutive model fitted based on experimental results. For members at high temperatures, when the strain value is large, the deformation and force calculated using simplified constitutive model deviates from that using the constitutive model fitted based on experimental results, but deviation is within an acceptable range. Therefore, the simplified constitutive model demonstrates both feasibility and accuracy, making it suitable for calculating the fire resistance of specimens.