Numerical simulation considering phase transformations on stocky columns of high strength S960 steel welded box sections under compression

Abstract

Due to their specific heat treatments during manufacturing, high strength low alloy S960 steel undergoes an intricate microstructural change after welding, resulting in complex phase transformations. To investigate and quantify the influence of these phase transformations on the structural behaviour of stocky columns of high strength S960 steel welded box sections under compression, this paper presents an advanced numerical simulation approach, i.e. the "thermo-metallurgical-mechanical-structural" approach, or the TMMS approach, which has been rationally validated through calibration against various sets of test data. Through standard dilatometry tests, the continuous cooling transformation curves of the S960 steel were determined, and they were employed to simulate the effects of welding onto the S960 steel during fabrication of the welded box sections using the finite element software SYSWELD. Both measured temperature-time curves obtained with thermocouples during welding, and surface residual stresses measured with the hole drilling method after welding were employed to validate accuracy of the thermo-metallurgical-mechanical simulation. After incorporating these data into structural models of the S960 steel welded box sections using the finite element package Abaqus, the structural behaviour of these box sections under compression was obtained, and their predicted load-deformation characteristics were found to compare well with measured data. Consequently, the proposed TMMS approach is demonstrated to be able to predict "thermo-metallurgical-mechanical-structural" responses of these high strength S960 steel welded sections effectively.