PSI - Issue 28

Maksim Ignatev et al. / Procedia Structural Integrity 28 (2020) 1650–1654 M. Ignatev / Structural Integrity Procedia 00 (2020) 000–000 As a result, dependence of the SIF on the fracture initiation time was obtained and it adequately predicts the experimental dependence when equals to 9 s (Fig. 1). Additionally, results for the different values of were obtained. Also, one can observe a transition of the obtained dependence curve to the quasi-static critical stress intensity value, that demonstrates applicability of the developed model for a wide range loading regimes. This result was already obtained analytically using the incubation time fracture model (Petrov and Morozov (1994)) and 9 s value. This way almost identical results were obtained using both analytic solution for the stress field in the vicinity of the crack tip and numerical peridynamic method. 1653 4

Fig. 1. Dependence of the critical SIF at the time of the crack initiation on the fracture time t* . The black squares show the experimental data (Ravi-Chandar K., Knauss W.G., 1984a), the dependencies obtained using the peridynamic simulations for various values of are shown by color curves (blue, orange and green). 5. Conclusion. Peridynamic versions of the structural and incubation time fracture criteria were suggested for use in the modelling of the crack initiation problem both in quasi-static and dynamic cases. It was demonstrated that experimentally measured critical SIF - time to fracture dependence, can be predicted numerically for the dynamic case when fracture time is small and loading rates are high. Classical concepts of the static and dynamic critical SIF account for an instantaneous stress state, neglecting its time-history variation that does not provide possibility to model the dynamic crack initiation phenomenon. At the same time the proposed combined numerical approach (peridynamics with incubation time fracture model) appears to be efficient for the specimen fracture toughness assessment in the case of high-speed dynamic loading. Acknowledgements This work was supported by the Russian Foundation for Basic Research (No. 20-01-00291, No. 19-31-60037). Sections 1 and 4 were made by Yuri Petrov within the framework of the Russian Science Foundation project (No. 17 11-01053). The authors are grateful to Dr. E. Oterkus, Professor of the University of Strathclyde and Head of the