PSI - Issue 37

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

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Procedia Structural Integrity 37 (2022) 397–403

ICSI 2021 The 4th International Conference on Structural Integrity Global and local fracture behavior in a brittle solid with a set of pre-existing small-scale cracks Koji Uenishi a,b *, Kunihiro Nagasawa b ICSI 2021 The 4th International Conference on Structural Integrity Global and local fracture behavior in a brittle solid with a set of pre-existing small-scale cracks Koji Uenishi a,b *, Kunihiro Nagasawa b a Department of Advanced Energy, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8561, Japan b D epartment of Aeron utics a d Astronautics, The University of Tokyo, 7-3-1 Hongo, Bunkyo 113-8656, Japa n Global and local fract eh g - cale cracks d r f 7 g o 6 a Department of Advanced Energy, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa 277-8561, Japan b D epartment of Aeronautics and Astronautics, The University of Tokyo, 7-3-1 Hongo, Bunkyo 113-8656, Japa n

© 2022 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 Pedro Miguel Guimaraes Pires Moreira Abstract For understanding the mechanics of complicated seismic activities, not only global observations of large-scale material behavior but also more local tracing of smaller-scale fractures is needed. In this study, therefore, by using the technique of dynamic photoelasticity, the evolution of fractures and waves is experimentally traced in a two-dimensional linear elastic brittle specimen that has a set of pre-existing small-scale parallel fracture regions. The small-scale fracture regions or cracks, modeling a large-scale geological normal fault plane, are prepared by a digital laser cutter. Our experimental observations with a high-speed video camera, together with finite difference numerical simulations, indicate that the global and local fracture behavior significantly depends on the initial inclination angle and distribution pattern of the set of parallel cracks. In the case of pre-existing cracks that are more vertically inclined with respect to the quasi-static external load applied by a tensile testing machine, the main fracture develops dynamically and then the secondary fractures appear at spatiotemporally remote distances from the main fracture. The secondary fractures extend also dynamically, into the direction opposite to the main fracture. On the other hand, in the case of smaller inclination angles, the main fracture tends to evolve quasi-statically. Nevertheless, in both cases, it is found that fracture can be arrested and jump without difficulties in a brittle solid having a number of small-scale cracks, which implies that such small-scale cracks may play an important part in the generation of a cluster of seismic events. © 2022 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 Pedro Miguel Guimaraes Pires Moreira Keywords: Jumping fracture; cluster of fractures; normal faulting; fracture dynamics; wave-induced fracture Abstract For understanding the mechanics of complicated seismic activities, not only global observations of large-scale material behavior but also more local tracing of maller-scale fractures is needed. I his study, therefore, by using the techniqu of dyn mic photoelasticity, the evolution of fracture and w ves i experim ntally traced in a wo-dimensional linear elastic brittle speci en that has a set of pr - xisting small-s ale parallel fracture regions. The small-scale fracture regions or cracks, modeling a larg -scale geologic l normal fault plane, are prepared by a digital las r cutter. Our experim nt l obs vati s with a high-sp ed video camera, together with finite differe ce numerical simulations, indicate hat the global and local fracture behavior significantly epends on he initial ncli a ion angle and dist bution pat er of the set of paralle cr cks. In the c se of pre-existin cra ks that are more vert cally i li ed with respect to the quasi-st ic external load a plied by tensile t sting machin , the main frac ure devel ps dynamically a d then the econdary fracture ppear at spati tem orally remot d stances from t e main fracture. The secondary fractures exte also dynamically, into the direction op osite to the main fracture. On the other h nd, in he case of smaller inclination angles, the main fr cture tends to evolve quasi- tatically. Nevertheless, in both cases, it is found at fracture can be arrested a d jump without di ficulti s i a brittle solid h v ng a number of smal - cale cracks, which mplies that such small-scal c acks m y play an impor ant part n the generation of a cluster of seismic events. © 2022 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 u der responsibility of Pedro Miguel Guimara s Pires Moreira K ywords: Jumping fracture; cluster f fractures; normal faulting; fracture dynamics; wave-induced fracture b a g e . s dy pho d p a w n a c t h a a r r ck d a s g g d y g x e a h a t t e i s i en he n he c - ra a e v c s -s a n dy ic e ry f ar a e a l mo e f e in p i e th a f i g i ur ot s i ou ct n a di t d n u p c a t g n u f © T i t l N - Pe - i re r g i a e K f a te f r l d i

* Corresponding author. Tel.: +81-4-7136-3824; fax: +81-4-7136-3824. E-mail address: uenishi@k.u-tokyo.ac.jp * Corresponding author. Tel.: +81-4-7136-3824; fax: +81-4-7136-3824. E-mail address: enishi@k.u-tokyo.ac.jp E i

2452-3216 © 2022 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 Pedro Miguel Guimaraes Pires Moreira 2452-3216 © 2022 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 u der responsibility of Pedro Miguel Guimara s Pires Moreira T i de - P r b r g a

2452-3216 © 2022 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 Pedro Miguel Guimaraes Pires Moreira 10.1016/j.prostr.2022.01.101