Investigation of the size of the fracture process zone and the cleavage stress in cracked steel parts

The study is devoted to the development of methods for predicting the brittle fracture of a steel part with a crack. To describe the limit state of the fracture process zone, a mathematical model of the fracture process zone in an elastic–plastic stress state and the generalized brittle fracture theory have been used. The cleavage stress and the size of the fracture process zone are used as parameters for the fracture toughness of the material. A finite element analysis approach was developed to determine these parameters by considering the elastic–plastic stress state of cracked specimens. An analytical procedure for calculating the above parameters for low‐carbon and low‐alloy steels is given. The proposed models allow the analytical calculation of critical values of the stress intensity factor for specimens with cracks at negative temperatures. The development of this study is linked to the improvement of the technology for determining the physical strength criteria of materials. The application of the proposed models makes it possible to create a methodology for predicting crack resistance of welded structures of arctic design considering their geometry and structural and technological characteristics. Highlights The crack resistance parameters are determined based on the analysis of the fracture process zone limit state. The fracture process zone size is calculated for structural steels as a function of the yield strength. The cleavage stress dependence on the yield strength and the rolled thickness is given. The presented analytic models are verified by the testing results of cracked steel specimens.