PSI - Issue 47

ScienceDirect Structural Integrity Procedia 00 (2022) 000 – 000 Structural Integrity Procedia 00 (2022) 000 – 000 Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Available online at www.sciencedirect.com ScienceDirect

www.elsevier.com/locate/procedia www.elsevier.com/locate/procedia

Procedia Structural Integrity 47 (2023) 617–622

© 2023 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the IGF27 chairpersons Abstract The paper is focused on the numerical simulation and mathematical prediction for the fatigue crack initiation and growth in smooth specimens under very high cycle fatigue (VHCF) torsion loading. The numerical simulation is based on the two-criteria multi-regime fatigue failure model proposed by authors. The experimental study on the VHCF torsion properties of titanium alloy have shown a complex scenario of the fatigue crack initiation and growth. The surface and subsurface crack initiations were observed. The initial stage of the fatigue crack growth is associated with a shear crack opening while the further growth is associated with a normal crack opening. The trajectory of the fatigue crack growth under pure torsion has a complex spatial shape with spontaneous branching. The proposed model is based on damage theory and through-calculation algorithm considering the change in stress state of the specimen during the cycling loading. The mechanical property of the material is linked to a value of damage function. The damage function is determined by stress state sensitive kinetic equation. The damage accumulation is associated with two different mechanisms: normal opening and shear cracks. The verification by these two criteria at each time step in each spatial node of the model allows to capture the change in crack opening mechanism during the simulations and the crack branching. During the simulation the crack is associated with areas of high damage accumulation that we call ‘quasi - cracks’. These quasi -cracks represent the spatial fatigue crack shape and the controlling the node-dying criterion allows to determine the type of the crack opening. The model was successfully applying to fatigue crack initiation and growth prediction in smooth VHCF specimens subjected to pure torsion loading. The results of numerical simulations are in good agreement with the experimental data. © 2023 The Authors. Published by EL SEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the IGF27 chairpersons Keywords: VHCF torsion, multi-regime model, numerical simulation, crack path prediction, damage function. Abstract The paper is focused on the numerical simulation and mathematical prediction for the fatigue crack initiation and growth in smooth specimens under very high cycle fatigue (VHCF) torsion loading. The numerical simulation is based on the two-criteria multi-regime fatigue failure model proposed by authors. The experimental study on the VHCF torsion properties of titanium alloy have shown a complex scenario of the fatigue crack initiation and growth. The surface and subsurface crack initiations were observed. The initial stage of the fatigue crack growth is associated with a shear crack opening while the further growth is associated with a normal crack opening. The trajectory of the fatigue crack growth under pure torsion has a complex spatial shape with spontaneous branching. The proposed model is based on damage theory and through-calculation algorithm considering the change in stress state of the specimen during the cycling loading. The mechanical property of the material is linked to a value of damage function. The damage function is determined by stress state sensitive kinetic equation. The damage accumulation is associated with two different mechanisms: normal opening and shear cracks. The verification by these two criteria at each time step in each spatial node of the model allows to capture the change in crack opening mechanism during the simulations and the crack branching. During the simulation the crack is associated with areas of high damage accumulation that we call ‘quasi - cracks’. These quasi -cracks represent the spatial fatigue crack shape and the controlling the node-dying criterion allows to determine the type of the crack opening. The model was successfully applying to fatigue crack initiation and growth prediction in smooth VHCF specimens subjected to pure torsion loading. The results of numerical simulations are in good agreement with the experimental data. © 2023 The Authors. Published by EL SEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the IGF27 chairpersons Keywords: VHCF torsion, multi-regime model, numerical simulation, crack path prediction, damage function. 27th International Conference on Fracture and Structural Integrity (IGF27) The modeling of the spatial fatigue crack growth in smooth specimens under VHCF torsion loading Ilia Nikitin, Alexander Nikitin*, Boris Stratula Institute for computer-aided desing Russian Academy of Sciences, 19/18, 2 nd Brestskaya, Moscow, 123056, Russia 27th International Conference on Fracture and Structural Integrity (IGF27) The modeling of the spatial fatigue crack growth in smooth specimens under VHCF torsion loading Ilia Nikitin, Alexander Nikitin*, Boris Stratula Institute for computer-aided desing Russian Academy of Sciences, 19/18, 2 nd Brestskaya, Moscow, 123056, Russia

* Corresponding author. Tel.: +7 965 436 59 80. E-mail address: nikitin_alex@bk.ru * Corresponding author. Tel.: +7 965 436 59 80. E-mail address: nikitin_alex@bk.ru

2452-3216 © 2023 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the IGF27 chairpersons 2452-3216 © 2023 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the IGF27 chairpersons

2452-3216 © 2023 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY-NC-ND license (https://creativecommons.org/licenses/by-nc-nd/4.0) Peer-review under responsibility of the IGF27 chairpersons 10.1016/j.prostr.2023.07.061