台湾的机械设计研究(英文版)

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pvt1352021701Cracks may occur coincident with corrosion representing a new hybrid defect in gas and
oil pipelines known as crack in corrosion (CIC) that is not directly addressed in the cur-rent codes or assessment methods. Hence， there is a need to provide an assessment of
CIC and evaluate the line integrity， as well as identify the requirements for defect repair
or line hydrotest. An experimental investigation was undertaken to evaluate the collapse
pressures of lines containing corrosion， cracks， or (CIC) defects in a typical line pipe
(API 5L Grade X52， 508 mm diameter， 5.7 mm wall thickness). The mechanical proper-ties of the pipe were measured using tensile， Charpy， and J-testing for use in applying
evaluation criteria. Rupture tests were undertaken on end-capped sections containing
uniform depth， finite length corrosion， cracks， or CIC defects. Failure occurred by plastic
collapse and ductile tearing for the corrosion defects， cracks， and CIC geometries tested.
For the corrosion defects， the corroded pipe strength (CPS) method provided the most
accurate results (13% conservative on average). The API 579 (level 3 failure assessment
diagram (FAD)， method D) provided the least conservative collapse pressure predictions
for the cracks with an average error of 20%. The CIC collapse pressures were bounded
by those of a long corrosion groove (upper bound) and a long crack (lower bound)， with
collapse dominated by the crack when the crack depth was significant. Application of
API 579 to the CIC provided collapse pressure predictions that were 18% conservative.
Sixteen rupture tests were successfully completed investigating the failure behavior of
longitudinally oriented corrosion， crack， and CIC. The pipe material was characterized
and these properties were used to predict the collapse pressure of the defects using cur-rent methods. Existing methods for corrosion (