Experimental analysis on the buckling failure of elliptical-notched circular tubes subjected to cyclic bending

This paper presents an experimental investigation on the buckling failure of 304 stainless steel tubes with five different elliptical-notched depths subjected to cyclic bending. It can be observed from the experiment data that the steel tube with any notch depth exhibits a cyclic hardening phenomenon from the moment and curvature relationship, and a steady-state loop is found after a few loading cycles. From the relationship between the ovalization and curvature, an unsymmetric and ratcheting manner of the curve is found. Lower notch depth leads to further unsymmetry of the curve. It can also be observed from curvature-number of cycles to produce buckling curve that five almost parallel straight lines can be found for five different notch depths in a log-log scale. Finally, by using the theoretical equation introduced by Kyriakides and Shaw in 1987, a material parameter equation for the notch depth was proposed in this study to simulate the aforementioned relationship. By comparing the theoretical analysis with the experimental data, it is shown that the theoretical formulation can properly represent the experimental results.