Three-dimensional finite element analysis of temperature and stress distributions for in-service welding process

Welding onto a pipeline in active operation, called in-service welding, is an advanced technique employed in the repair of pipelines, and it has wide application in guaranteeing the safe transmission of petroleum or gas. The main objective of the present investigation is to carry out the analysis of temperature and stress during in-service welding of X70 pipeline steel. Using the three-dimensional analysis software SYSWELD, a 3-D numerical model was established to simulate a single bead-on-plate specimen. To study the influence of flowing water on the temperature field and stress distributions of in-service welding, model predictions have been compared against data generated by welding without flowing water. The results showed the flowing medium creates much heat loss, resulting in accelerated cooling of the weld and the great decrease in the peak temperature of the inner surface of the plate, and the flowing water also has significant influence on the residual stress. Through developing a reasonable test equipment of in-service welding and using the simulation experiment of shielded manual mental arc bead-on-plate welding, the calculation results of this finite element (FE) model have been validated and show good agreement with the experimental data.