PSI - Issue 28

Available online at www.sciencedirect.com vailable online at .sciencedirect.co Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2019) 000–000

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ScienceDirect ScienceDirect

Procedia Structural Integrity 28 (2020) 829–835 Structural Integrity Procedia 00 (2019) 000–000

www.elsevier.com/locate/procedia

© 2020 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 European Structural Integrity Society (ESIS) ExCo Abstract Polymethylmethacrylate (PMMA) is one of the well-known dental materials generally used for restoration, extension and relining of dental prostheses. Being subjected to periodic loads, while sustaining inherent voids and microcracks, dental materials are prone to the nucleation and extension of cracks under mixed mode loading condition. In this paper, the mixed mode fracture behavior of PMMA dental materials is studied both experimentally and theoretically. The experiments are carried out using a modified single edge notched bend (SENB) specimen. To theoretically assess the onset of fracture, the theory of critical distance (TCD) along with the generalized strain energy density (GSED) criterion is utilized. This fracture model includes the effect of the second stress term in the William’s series expansion, known as the T-stress, in addition to the stress intensity factors (SIFs) to estimate the onset of fracture. Based on the theoretical model, crack propagation commences once the strain energy W reaches its critical value W c over a critical distance r c , with W c and r c both being material parameters. This article also suggests the implementation of a new critical distance model, derived from the GSED criterion, which ameliorates the theoretical estimates when compared to the traditional models for the critical distance devised specifically for stress-based fracture models. It is eventually demonstrated that the GSED criterion provides superior fracture predictions for the tested PMMA dental material in comparison with the classical SED criterion, mainly in view of the contribution of the T-stress and the critical distance concept. Keywords: Dental material; mixed mode experiments; theory of critical distance; generalized strain energy density (GSED) criterion; T-stress 1st Virtual European Conference on Fracture Theory of critical distance combined with the generalized strain energy density criterion for mixed mode fracture assessment of PMMA dental materials Bahador Bahrami a , Majid R. Ayatollahi a* , Saeid Ghouli a a Fatigue and Fracture Laboratory, School of Mechanical Engine ri g, Center of Exc llence in Experimental Solid Mechanics and Dynamics, Iran University of Science and Technology, Narmak, Tehran 16846, Iran Abstract Polymethylmethacrylate (PMMA) is one of the well-known dental materials generally used for restoration, extension and relining of dental prostheses. Being subjected to periodic loads, while sustaining inherent voids and microcracks, dental materials are prone to the nucleation and extension of cracks under mixed mode loading condition. In this paper, the mixed mode fracture behavior of PMMA dental materials is studied both experimentally and theoretically. The experiments are carried out using a m difi d single edge notched bend (SENB) specimen. To theoretically assess th onset of fracture, the theory of critical distance (TCD) ong with the g neralized s rain energy ensity (GSED) criter o is utiliz d. Th s fr cture m del inclu es the eff ct of th second stress term in the William’s series expansion, known as the T-stress, in a d tion to the stress int nsity factors (SIFs) to estimate the onset of fracture. Based on the th oretical model, crack propagati n commenc s onc the strain ne gy W reaches its critical value W c over a critical distance r c , w th W c and r c both being mat rial parameters. This article also suggests th implementation of a new crit cal dista ce model, derived from the GSED cr terion, which ameliorat s the th oretical s ima es whe compared to the trad tional mod l for the critical distanc devis d specifically f r stress-based fracture models. It is ventually demonstrated hat the GSED cri eri n provides superior f acture predictions for the t sted PMMA dental m terial in omp rison with the classi al SED criterion, mainly in view of the contribution of the T-stress and the critica distance concept. Keywords: Dental material; mixed mo e experiments; theory of critical distance; generalized strain energy density (GSED) criterion; T-stress 1st Virtual European Conference on Fracture Theory of critical distance combined with the generalized strain energy density criterion for mixed mode fracture assessment of PMMA dental materials Bahador Bahrami a , Majid R. Ayatollahi a* , Saeid Ghouli a a Fatigue and Fracture Laboratory, School of Mechanical Engineering, Center of Excellence in Experimental Solid Mechanics and Dynamics, Iran University of Science and Technology, Narmak, Tehran 16846, Iran

* Corresponding author. Tel.: +98 21 77240201; fax: +98 21 77240488. E-mail address: m.ayat@iust.ac.ir.

2452-3216 © 2020 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 European Structural Integrity Society (ESIS) ExCo 10.1016/j.prostr.2020.10.097 2452-3216 © 2020 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 European Structural Integrity Society (ESIS) ExCo 2452-3216 © 2020 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 European Structural Integrity Society (ESIS) ExCo * Corresponding author. Tel.: +98 21 77240201; fax: +98 21 77240488. E-mail address: m.ayat@iust.ac.ir.