Prediction of creep deformation behavior of KHR45A heater tube steel using nonlinear mixed-effect model

A study for predicting the creep deformation behavior of a MERT (mixing element radiant tube) type KHR45A steel is carried out. To this end, a modification of the theta projection model is proposed by incorporating a statistical analysis technique especially with a nonlinear mixed-effect model. The model is applied for predicting the creep deformation behavior of a KHR45A steel. Creep curve data used for prediction was obtained by creep test in the stress range of 20.2–73.7 MPa and the temperature range of 816–1093 °C. The proposed model is demonstrated to be more accurate and practically meaningful than the existing theta projection model for predicting the creep deformation behavior. The prediction accuracy of the proposed model is confirmed using mean absolute percentage error (MAPE) and symmetric MAPE (SMAPE) calculations.