PSI - Issue 39

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

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

Procedia Structural Integrity 39 (2022) 179–193

© 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 CP 2021 – Guest Editors Abstract The harmonic content of the temperature measured via a Thermoelastic Stress Analysis setup in a Single Edge Notched Tension stainless steel specimen is analyzed to obtain information about crack-closure during crack propagation. The first harmonic amplitude maps, combined with the Williams’ stress solution, are used to monitor the crack growth and evaluate the Stress Intensity Factor, enabling the extraction of a Paris’ law. Particular attention is devoted to the detection of crack-closure, via the second harmonic component of temperature. A study of the effects of the cyclical load that acts on the flanks of the crack is presented, and the experimental campaign allows to validate the theoretical assumptions made. It is shown that the load that acts on the wake of the crack has a significant component at twice the loading frequency, that is codified at a specific angular position. Furthermore, the analysis of a previously overloaded specimen allows to highlight the different crack closure behavior due to a residual stress state at the crack tip. The work proves that the proposed second harmonic thermoelastic analysis represents a powerful and robust tool for studying crack closure during crack propagation. © 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 CP 2021 – Guest Editors Keywords: Fatigue Crack Growth; Thermoelastic Stress Analysis; Plasticity-Induced Crack Closure; Stress Intensity Factor. 1. Introduction Thermoelastic Stress Analysis (TSA) is a full-field non-contact technique [1] that many authors successfully used in the study of crack problems [2]–[11]. Among other experimental techniques (e.g., strain gauges, photoelasticity, Abstract The harmonic content of the temperature measured via a Thermoelastic Stress Analysis setup in a Single Edge Notched Tension stainless steel specimen is analyzed to obtain information about cra k-closure during crack propagation. The first harmonic amplitude maps, combi ed with the Williams’ stress soluti , re sed to monitor the crack growth and evaluate t Stress Intensity Factor, enabling the extraction of a Paris’ law. Particular attention is devoted to the detection of crack-closure, via the s cond h rmonic component of temperature. A study of the effects of the cyclical load that acts on the flanks of the crack is presented, a the experimental campaign allows to validate the th oretical assumptions ma e. It is sh wn that the load that acts on the wake of t crack has a significant component t twice the loading frequency, that is codified at a specific angular position. Furthermore, t analysis of a previously verloaded specimen allows to highlight the different crack closure behavior due to a residual stress state at the crack tip. The work pr ves that the proposed second harmonic thermoelastic analysis represents a powerful and robust tool for studying crack closure during crack propagation. © 2021 The Authors. Publish d 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 CP 2021 – Guest Editors Keywords: Fatigue Crack Growth; Thermoelastic Stress Analysis; Plasticity-Induced Crack Closure; Stress Intensity Factor. 1. Introduction Thermoelastic Stress Analysis (TSA) is a full-field non-contact technique [1] that many authors successfully used in the study of rack problem [2]–[11]. Among other experimental techniques (e.g., strain gauge , photoelasticity, 7th International Conference on Crack Paths Detection of crack-closure during fatigue loading by means of 7th International Conference on Crack Paths Detection of crack-closure during fatigue loading by means of Second Harmonic Thermoelastic Stress Analysis Riccardo Cappello a , Salvatore Cutugno a , Giuseppe Pitarresi a * a Department of Engineering, University of Palermo, Viale delle Scienze, 90128, Palermo, Italy Second Harmonic Thermoelastic Stress Analysis Riccardo Cappello a , Salvatore Cutugno a , Giuseppe Pitarresi a * a Department of Engineering, University of Palermo, Viale delle Scienze, 90128, Palermo, Italy

* Corresponding author. Tel.: +39 091 23897281 E-mail address: giuseppe.pitarresi@unipa.it * Corresponding author. Tel.: +39 091 23897281 E-mail address: giuseppe.pitarresi@unipa.it

2452-3216 © 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 CP 2021 – Guest Editors 2452-3216 © 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 CP 2021 – Guest Editors

2452-3216 © 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 CP 2021 – Guest Editors 10.1016/j.prostr.2022.03.087