Crushing Analysis of Circular Tube With Local Thickness Reduction Between Wedge Indenter and Rigid Plane

Offshore pipelines are susceptible to both corrosion induced thickness reduction and external inference load from anchors or dropping objects. The deformation modes and energy absorption properties of defected rings have been rarely studied. This paper presents a combined experimental, FEA and analytical analysis of crushing of circular rings with local thickness reduction between a wedge-shape indenter and a rigid plane. Short-width aluminium defected ring specimens were manufactured by CNC milling to avoid residual stress and experimentally crushed under a top wedge of 90-deg included angle. The tensile tests were carried out to obtain the material hardening parameters. A python script in Abaqus was compiled to allow automatic parametric modelling and analysis enabling extensive parametric analysis under plane stress conditions. The active yielding region visualization was employed to illustrate clearly the evolution of plastic regions and force-displacement curves show agreements between experimental and FEA results. Parametric analysis was presented for angular extent, 0 or 180 deg loading cases, material hardening. Analytical formulations by rigid plastic model are presented for crushing phases with initial elastic phase predicted well by Castigliano’s theorem. Initial phase prediction agreed exactly with FEA or experimental results. While the accuracy of analytical formulation was shown to significantly depend on the hardening property: when hardening is weak, the plastic hinge is more localized and the collapse mechanism could be well-predicted. Interestingly in the 180 degree loading case, when the extent angle of the thinner region is small, separation at bottom occurs. Collapsed shapes and active yielding zone visualization are presented for smooth and rough friction cases and separation gap is smaller in rough cases. An analytical averaged force estimation by rigid plastic model is presented allowing accurate estimation of absorbed energy amount for realistic materials. This paper should enhance the understanding of crushing behavior of defected short-length tube or ring under plane stress state and applicable to structural integrity assessment for estimating the allowable impacting kinetic energy.