Tensile damage evolution of structural steels with different structure

Assessment of the current state and prediction of the residual life of a material or structural element during operation remains one of the most urgent tasks for many years. The results obtained in this area are important both from a scientific and an engineering point of view. This study is devoted to establishing the correlation between the real damage of the material at different stages of loading and the characteristics evaluated by non-destructive techniques. In the study, we investigated the changes in physical parameters of non-destructive testing (coercive force, eddy current parameter, and self-magnetic field intensity), acoustic emission parameters, and characteristics of real damage (relative area of the damaged surface), estimated at static tension of specimens made of structural steels. The real damage estimation was carried out by studying the microcracks patterns at various stages of the deformation of specimens. The achievement of characteristic stresses – the yield strength and ultimate strength – affect the magnetic and acoustic parameters. The results obtained allowed us to distinguish four stages of fracture including the stage of elastic deformation, stage of initiation, and growth of microcracks, stage of microcracks coalescence, and pre-fracture stage. The approach used in this work made it possible to obtain empirical dependencies between the coercive force and damage parameter, which can be used to assess the state of material during its deformation or operation.