Low cycle fatigue behaviour and life prediction of Q345B steel and its welded joint

Low cycle fatigue behaviour of Q345B steel and its smooth welded joint were experimentally investigated in fully reversed strain-control at constant strain rate of 0·005 s−1. The cyclic stress response characteristics, strain–life and strain–energy relationships were obtained and analysed in the strain regime 0·3–0·7%. It was found that Q345B showed significant cyclic hardening and softening above and below the 0·4% strain amplitudes, respectively. The welded joints showed cyclic hardening in the entire strain regime because of the mechanical inhomogeneity. The low cycle transition life, fatigue strength and fatigue life of welded joint were found significantly lower with increase in the cyclic hardening. The experimental data were used to extract the Coffin–Manson parameters and the strain–life relationship. In addition, the expressions of plastic strain energy and fatigue life were also obtained using the energy prediction method. Publisher statement: This is an Accepted Manuscript of an article published by Taylor & Francis in Materials Research Innovations on 30th May 2015, available online: http://www.tandfonline.com/doi/full/10.1179/1432891714Z.0000000001298