Plastic Collapse Load Determination Using Laboratory-Scale SE(T) Samples Under Fixed-Grip Loading

A high-toughness steel was tested in tension under fixed-grip loading using Charpy-size SE(T) samples. The objective was to determine plastic collapse loads using laboratory-scale samples under conditions similar to those experienced by girth weld defects in pipelines. The selection of the high-toughness steel was to inhibit significant crack extension from notches at maximum loads and this was largely achieved based on fractographic observations and ductile tearing analysis. This paper includes detailed experimental measurements of maximum loads, fractographic observations, and comparison of the experimental values with FEA results in 2-D plane stress and plane strain and in 3-D. The plastic collapse limit in BS 7910 was found to be conservative for plane-sided samples by 17 to 30% (average 23%) for the steel and geometries used in this work.