PSI - Issue 37

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ScienceDirect

Procedia Structural Integrity 37 (2022) 525–532 Structural Integrity Procedia 00 (2021) 1–8 Structural Integrity Procedia 00 (2021) 1–8

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ICSI 2021 The 4th International Conference on Structural Integrity ICSI 2021 The 4th International Conference on Structural Integrity

On the defect tolerance by fatigue spectral methods based on full-field dynamic testing Alessandro Zanarini ∗ On the defect tolerance by fatigue spectral methods based on full-field dynamic testing Alessandro Zanarini ∗

DIN, Industrial Engineering Dept., University of Bologna, Viale Risorgimento 2, 40136 Bologna, Italy DIN, Industrial Engineering Dept., University of Bologna, Viale Risorgimento 2, 40136 Bologna, Italy

Abstract Abstract

© 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 In real life production of dynamically loaded components, we might accept the risk of defects only if we can assess their position by NDT techniques, their e ff ect by proper cumulative damage theory, the dynamic signature of the excitation and the structural dynamics of our structures in service. This work addresses the latter topic by means of experimental full-field optical techniques, which can provide accurate surface displacement distribution in a broad frequency band directly from real components, while recording the excitation, thus, with advanced numerical derivations, coming to an experiment-based full-field strain FRF character isation, here applied on an aluminium plate. The knowledge of the material constitutive parameters is used to obtain the Von Mises equivalent stress FRFs. The signature of the excitation permits the evaluation of the Von Mises stress PSDs, which can be used in a spectral fatigue method (here the one from Dirlik), coming to a frequency-to-failure distribution. The same distribution can be scaled to a risk index and compared to the defect locations from NDT, in order to build a defect tolerance map and discriminate the product acceptance for dynamically loaded components. The smart exploitation of full-field optical techniques play a relevant role in measuring, with high spatial resolution, the manufactured components in their e ff ective broad structural dynamics and give defect tolerance experiment-based maps, without the need of a highly tuned FE model. c � 2021 The Authors. Published by ELSEVIER B.V. This is an open access article under the CC BY- C-ND license (https: // creativec mmons.org / licenses / by-nc-nd / 4.0) Peer-review under responsibility of Pedro Miguel Guimaraes Pires Moreira. In real life production of dynamically loaded components, we might accept the risk of defects only if we can assess their position by NDT techniques, their e ff ect by proper cumulative damage theory, the dynamic signature of the excitation and the structural dynamics of our structures in service. This work addresses the latter topic by means of experimental full-field optical techniques, which can provide accurate surface displacement distribution in a broad frequency band directly from real components, while recording the excitation, thus, with advanced numerical derivations, coming to an experiment-based full-field strain FRF character isation, here applied on an aluminium plate. The knowledge of the material constitutive parameters is used to obtain the Von Mises equivalent stress FRFs. The signature of the excitation permits the evaluation of the Von Mises stress PSDs, which can be used in a spectral fatigue method (here the one from Dirlik), coming to a frequency-to-failure distribution. The same distribution can be scaled to a risk index and compared to the defect locations from NDT, in order to build a defect tolerance map and discriminate the product acceptance for dynamically loaded components. The smart exploitation of full-field optical techniques play a relevant role in measuring, with high spatial resolution, the manufactured components in their e ff ective broad structural dynamics and give defect tolerance experiment-based maps, without the need of a highly tuned FE model. c � 2021 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: defect tolerance; optical full-field dynamic testing; full-field FRFs; fatigue spectral methods; NDT Keywords: defect tolerance; optical full-field dynamic testing; full-field FRFs; fatigue spectral methods; NDT

1. Introduction 1. Introduction

The key idea sketched in this brief article is to use a broad frequency band experiment-based full-field FRF ap proach to bring the complete & real structural dynamics into fatigue life expectations, which come as failure maps, therefore opening for a risk tolerance strategy of the defects that may be inside the material, due to the manufacturing process or to excessive loading. In such a broad perspective, for the retained dynamics and for the high resolution mapping achievable, the location of the potential defect plays an uttermost relevance in the crack & failure start: what follows is devoted to highlight the potentials of this smart approach with simple examples. The key idea sketched in this brief article is to use a broad frequency band experiment-based full-field FRF ap proach to bring the complete & real structural dynamics into fatigue life expectations, which come as failure maps, therefore opening for a risk tolerance strategy of the defects that may be inside the material, due to the manufacturing process or to excessive loading. In such a broad perspective, for the retained dynamics and for the high resolution mapping achievable, the location of the potential defect plays an uttermost relevance in the crack & failure start: what follows is devoted to highlight the potentials of this smart approach with simple examples.

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.2022.01.118 ∗ Corresponding author. Tel + 39 051 209 3442. E-mail address: a.zanarini@unibo.it (Alessandro Zanarini). 2452-3216 c � 2021 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. ∗ Corresponding author. Tel + 39 051 209 3442. E-mail address: a.zanarini@unibo.it (Alessandro Zanarini). 2452-3216 c � 2021 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.