On the response of dented stainless-steel pipes subject to cyclic bending moments and its prediction

• Response of dented steel pipes subject to symmetric cyclic loads was investigated.
• The pipes were hardened as a result of the loading.
• The variation cross-section ovalization followed the trend seen under ratcheting.
• A creep-law like equation was proposed for prediction of the ovalization.

In this paper, the effect of initial dent depth on the response of pipes subjected to cyclic bending loads with relatively large magnitudes is investigated experimentally. The initiation and propagation of the resulting cracks in the damaged region of the pipe are found to cause fatigue failure, augmented by the progressive accumulation of the cross-section ovalization during the cyclic loading. The empirical formula proposed by Kyriakides and Shaw [1] is modified based on the experimental results, in order to predict the number of cycles causing the local instability of pipe's cross-section. Moreover, it is shown that the experimental curve of the ovalization and the number of cycles necessary to produce buckling can be divided into three stages: initial, secondary and tertiary stages. Finally, an empirical equation, similar to the Bailey–Norton creep relationship, is proposed for simulating the initial and secondary stages of the aforementioned curve. The results produced by the proposed empirical relationship are found to be in good agreement with the experimental data.