Investigation of the tensile strain response of the girth weld of high-strength steel pipeline

Abstract

The in-depth analysis of the tensile strain response of the girth weld is very important for the safety assessment of the pipeline. This study is carried out through a combination of experiment and numerical simulation. The microstructure and hardness distribution of the girth weld are obtained. Based on the digital image correlation (DIC) technique, the tensile strain response of the girth weld during the whole tensile process is obtained by using the full wall thickness specimens. The results show that the strain concentration first occurs near the outer surface of heat-affected zone (HAZ). Then, a significant strain concentration area connecting from the outer surface of HAZ to the inner surface of weld metal (WM) is gradually formed. Eventually, the crack initiates on the outer surface of the girth weld and extends to the inner surface. Considering the material constraint effect of the girth weld, a constitutive relationship determination method combing DIC technique and finite element analysis is proposed. Based on the method, the detailed constitutive parameters of the girth weld are obtained. The accuracy of the parameters is verified. The full-scale pipeline girth weld is analyzed by finite element method. The results show that the area near the interface between the root weld layer and the filler weld layer of WM is the most significant strain concentration area under different internal pressures. The change characteristics of the strain concentration factor of the girth weld are also obtained. The increase of internal pressure can reduce the strain capacity of the pipeline.