Effect of Crack Geometry and Tensile Properties on Tensile Strain Limit of X80 Linepipe

摘要

Construction of gas transmission pipelines is expanding to severe environmental area such as seismic or permafrost region. This paper presents the preliminary studies performed with curved wide plate test focused on the tensile strain limit of X80 girth welded linepipe which will be used in such regions. Three dimensional elastic-plastic finite element analyses (FEA) are also conducted to obtain the equivalent plastic strain at the notch tip which is used for critical parameter of ductile crack initiation. The critical equivalent plastic strain for ductile crack initiation is obtained from the single edge notched tension test and the FEA. In this paper, curved wide plate tests of specimens having defects in the heat affected zone (HAZ) of girth welded joints and a parametric study by FEA were carried out, focusing on the tensile strain limit for ductile crack initiation as a early stage of ductile fracture. In particular, the effects of material tensile properties, strength matching, crack dimensions, plate thickness and the width of HAZ on the relationship between the critical equivalent plastic strain at the crack tip for ductile crack initiation and the global strain were investigated by using curved wide plate model.