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The geometric imperfections in high strength U-ing, O-ing and expanding (UOE) manufactured pipes are investigated in this paper using a high-resolution 3D surface scanner, and a reverse engineering and inspection software. The geometric analyses show that the initial imperfection patterns in the UOE manufactured pipes are not at all random, although the magnitudes of imperfections may vary across specimens. These patterns of outside radii and pipe wall thickness imperfections consistently appear along the length of the specimens regardless of their D/t ratios and manufacturer. The sources of these imperfections can potentially be traced back to the UOE manufacturing process.

The effects of the initial geometric imperfections on the buckling response of grade X-100 UOE manufactured pipes are studied through finite element analysis (FEA). The initial geometric imperfections had been previously measured and quantified in terms of deviations in outside radius (OR) and wall thickness. The measurement results are used to develop imperfection models to be incorporated into buckling analysis. The OR deviation is seen to have insignificant effects on the buckling behavior, while the effects of thickness deviation are seen to be profound for both unpressurized and pressurized pipes. The geometric imperfection models are further investigated through a sensitivity study to isolate the most influential imperfection aspects on the buckling resistance of UOE pipes. A parametric study is carried out using these models and shows that excluding geometric imperfections will always result in overprediction of buckling capacity irrespective of D/t ratios.