Strain Analysis of Pipeline Test Specimens Containing Longitudinal and Circumferential Corrosion Defects

Abstract

The elastic and plastic strain data of tubular specimens undergoing rupture under internal pressure tests are presented and analyzed. Six tubular specimens were tested. The specimens were cut from longitudinally welded tubes made of API 5L X80 steel with a nominal outside diameter of 457.2mm (18in) and a nominal wall thickness of 7.93mm (0.312in). Each of the six specimens had one external longitudinal or circumferential corrosion defect that had been machined using spark erosion. Tensile specimens and impact test specimens were tested to determine material properties. Post-yielding electrical resistance strain gages were used to measure the elastic and plastic strains. The failure pressures measured in the laboratory tests were compared with those predicted by the DNV RP-F101 method for single defects and by the Kastner equation. The paper also discusses the strength of the pipe segments used in the tests under the assumptions of following the Tresca rupture criterion.