Buckling of High Strength Steel Cylinders Under Cyclic Bending in the Inelastic Range1

Abstract

The present paper examines the structural behavior of elongated steel hollow cylinders, referred to as tubes or pipes, subjected to large cyclic bending, through a rigorous finite element simulation. The bent cylinders exhibit crosssectional distortion, in the form of ovalization, combined with excessive plastic deformations. Those deformations grow under repeated loading and may lead to structural instability in the form of local buckling (wrinkling) and, eventually, failure of the loaded member. The study focuses on relatively thickwalled seamless cylindrical members made of highstrength steel, which exhibit local buckling in the plastic range of the steel material. The analysis is conducted using advanced nonlinear finite element models capable of describing both geometrical and material nonlinearities. A cyclic plasticity model that adopts the “bounding surfaceâ€‌ concept is employed. The material model is calibrated through specialpurpose material testing, and implemented within ABAQUS, using a usersubroutine. The finite element model is validated by comparison with two experiments on highstrength steel tubular members. Special emphasis is given on the increase of ovalization and the gradual development of smallamplitude initial wrinkles with repeated loading cycles. A parametric numerical study is conducted, aimed at determining the effects of initial wrinkles on plastic buckling performance.