Study on the Ultimate Load Capacity of Cu-Ni Alloy Pipelines with Double Pitting Defects

Abstract

To accurately evaluate the load-bearing capacity of Cu-Ni alloy pipelines with double pitting corrosion defects, in this study, the influence of dual-defect morphological parameters on the ultimate load capacity was investigated through finite element simulation. On the basis of the ultimate load capacity model for single pit defects and simulation results, an assessment model was developed for Cu-Ni alloy pipelines containing double pitting defects, and its accuracy was validated through hydrostatic burst tests. The results indicate that the ultimate load capacity increases gradually with increasing interdefect center distance, asymptotically approaching the load-bearing capacity of a single-defect pipeline with an equivalent depth and diameter. The proposed model demonstrates excellent predictive performance, with a maximum error margin within 3%. During failure, Cu-Ni alloy pipelines with double pitting defects develop fine axial cracks at the defect sites while exhibiting significant overall bulging deformation. These findings can be effectively applied to predict the ultimate load capacity of Cu-Ni alloy pipelines with double pitting defects, providing substantial engineering value for an accurate assessment of the load-bearing capacity of pipelines with actual corrosion defects.

Keywords: Cu-Ni alloy pipeline; double pitting defect; finite element simulation; hydrostatic burst test; ultimate load capacity.

Figure 12

Comparison of fracture morphology. (Figure (c) presents a cross-section of Figure (f) at A-A, rotated 90° clockwise).

Figure 1

Research methodology and approach.

Figure 2

Schematic diagram of defect parameter definitions.

Figure 3

Schematic diagram of the test equipment connection.

Figure 4

Blast Morphology of Double Pitting Corrosion Defects.

Figure 5

Von Mises stress nephogram of pipeline AP8# under different internal pressures.

Figure 6

Relationship between double pitting defect depth and ultimate load capacity.

Figure 7

Relationship between the center distance of double pitting defects and the ultimate load capacity (for different corrosion depth ratios N).

Figure 8

Relationship between double pitting defect diameter and ultimate load capacity.

Figure 9

Relationship between center distance of double pitting defects and the ultimate load capacity (for different corrosion diameters $D_P$).

Figure 10

Correction effectiveness of the modified formula for double pitting defects.

Figure 11

Documentation of the bursting process in pipeline 1#.