PSI - Issue 24

ScienceDirect Structural Integrity Procedia 00 (2019) 000 – 000 Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2019) 000 – 000 Available online at www.sciencedirect.com Available online at www.sciencedirect.com Sci nceDir t

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

Procedia Structural Integrity 24 (2019) 583–592

© 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the AIAS2019 organizers © 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the AIAS2019 organizers In this work, the ultrasound technique was used to monitor the damage of material subjected to fatigue loads. Prediction of structural damage is critical for safe and reliable operation of engineered complex systems. In these measurements, conventional ultrasonic probes (transmitter and receiver) were stably fixed to the tested samples with steel brackets, in order to eliminate ever possible variability associated with the coupling of probes. The transmitted and received ultrasonic signals were recorded and analyzed using a digital oscilloscope. The data were converted into the frequency domain using an algorithm developed in Matlab based on Fast Fourier Transform (FFT) for received signal in dependence of the applied stress level and the accumulated fatigue damage was deeply studied in order to recognize quantitative effects, suitable for an experimental prediction of the integrity of the material. The acquired data were compared with the reference signal, at the beginning of the fatigue tests. Particular care has been paid to UT signal attenuation and to the study of the frequency spectru as the number of load cycles varies. The applied experimental technique has proved efficient for detecting damage induced by mechanical stress. © 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the AIAS2019 organizers AIAS 2019 International Conference on Stress Analysis Real-time monitoring of damage evolution by nonlinear ultrasonic technique Vito Dattoma a , Riccardo Nobile a , Francesco Willem Panella a , Andrea Saponaro a * a Department of Engineering for Innovation, University of Salento, Lecce 73100, Italy In this work, the ultrasound technique was used to monitor the damage of material subjected to fatigue loads. Prediction of structural damage is critical for safe and reliable operation of engineered complex systems. In these measurements, conventional ultrasonic probes (transmitter and receiver) were stably fixed to the tested samples with steel brackets, in order to eliminate ever possible variability associated with the coupling of probes. The transmitted and received ultrasonic signals were recorded and analyzed using a digital oscilloscope. The data were converted into the frequency domain using an algorithm developed in Matlab based on Fast Fourier Transform (FFT) for received signal in dependence of the applied stress level and the accumulated fatigue damage was deeply studied in order to recognize quantitative effects, suitable for an experimental prediction of the integrity of the material. The acquired data were compared with the reference signal, at the beginning of the fatigue tests. Particular care has been paid to UT signal attenuation and to the study of the frequency spectrum as the number of load cycles varies. The applied experimental technique has proved efficient for detecting damage induced by mechanical stress. AIAS 2019 International Conference on Stress Analysis Real-time monitoring of damage evolution by nonlinear ultrasonic technique Vito Dattoma a , Riccardo Nobile a , Francesco Willem Panella a , Andrea Saponaro a * a Department of Engineering for Innovation, University of Salento, Lecce 73100, Italy Abstract Abstract

Keywords: NDT; fatigue; damage evolution; ultrasonic technique; FFT Keywords: NDT; fatigue; damage evolution; ultrasonic technique; FFT

1. Introduction 1. Introduction

A mechanical element subjected to a high static load in most cases develops a strong plastic deformation before breaking, allowing the component to be replaced beforehand. When, on the other hand, we are dealing with time varying loads, the component breaks down without warning, in a manner similar to that of a fragile static fracture. Traditionally, the fatigue failure process determined by variable loads is distinguished in three phases. For a well- A mechanical element subjected to a high static load in most cases develops a strong plastic deformation before breaking, allowing the component to be replaced beforehand. When, on the other hand, we are dealing with time varying loads, the component breaks down without warning, in a manner similar to that of a fragile static fracture. Traditionally, the fatigue failure process determined by variable loads is distinguished in three phases. For a well-

* Corresponding author. Tel.: +39 0832 297786; fax: +39 0832 297768. E-mail address: andrea.saponaro@unisalento.it * Correspon ing author. Tel.: +39 0832 297786; fax: +39 0832 297768. E-mail address: andrea.saponaro@unisalento.it

2452-3216 © 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the AIAS2019 organizers 10.1016/j.prostr.2020.02.051 2452-3216 © 2019 The Authors. Published by Elsevier B.V. This is an ope access article under t CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the AIAS2019 organizers 2452-3216 © 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/) Peer-review under responsibility of the AIAS2019 organizers