Bending Capacity of Tubes With Lüders Bands: Influence of Geometric and Material Parameters

Previous studies involving a combination of experiment and analysis have shown that when bending a pipe with material that exhibits Lüders bands to strain levels of 2–3% the structure develops instabilities that can lead to premature collapse. It has been demonstrated that the associated events and limit states can be consistently simulated using 3D finite elements and an elastic-plastic constitutive model with an up-down-up material response. This paper presents the results of a parametric study of the problem in which a wide range of geometric and material parameters are considered. The parametric study quantifies the boundary between stable and unstable behavior and shows that the bounding values of Lüders strain depend on the D/t of the tube and the level of the Lüders stress.