Predicting Damage in Steel Pipe Elbow Under Combined Pressure and Bending Using X-FEM

Abstract

This study determined the limit loads for API X60 pipe elbows subjected to in-plane bending moments in both opening and closing modes, while accounting for the effects of internal pressure. Load–deflection curves were analyzed to identify plastic collapse and instability loads at various pressure levels. The extended finite element method (XFEM) was used, incorporating a specialized elbow element to account for varying bend factors. The results indicated that theoretical equations are more conservative for closing moments compared to opening moments. Internal pressure significantly enhances load-bearing capacity, with a more pronounced effect as the bend factor increases. The Goodall equation remains conservative when combined with internal pressure and bending moments. Additionally, the study highlights pipe elbow geometry as a key factor influencing structural capacity, offering valuable insights for safer pipeline design.