Titanium pipes subjected to bending moment and external pressure

Titanium is being considered as an alternative to steel for risers and flowlines, particularly for deep-water applications. However, steel capacity formulas for local buckling and collapse are inadequate for direct application to titanium pipes subjected to bending and high external pressure. If formulas developed for steel are applied directly, the model uncertainty is unknown. Ideally, extensive model testing of titanium pipes is required. This paper discusses the use of a supplementary numerical approach based on finite element analysis. The relationship between material model parameters being input to the analysis and the collapse/buckling capacity is investigated by performing a series of nonlinear finite element analyses. The results from the non-linear response analyses are compared with experimental results for pipes with different D/t-ratios. Finally, the results are as a basis for proposing a formula for design check of titanium pipes subjected to high external pressure and bending moments. (C) 2003 Elsevier Ltd. All rights reserved.