PSI - Issue 42

Available online at www.sciencedirect.com Structural Integrity Procedia 00 (2019) 000 – 000 tr t r l I t rit r i ( ) Available online at www.sciencedirect.com ^ĐŝĞŶĐĞ ŝƌĞĐƚ il l li t . i i t.

www.elsevier.com/locate/procedia . l i r. /l t / r i

ScienceDirect

Procedia Structural Integrity 42 (2022) 1061–1068

© 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 the scientific committee of the 23 European Conference on Fracture – ECF23 Abstract Lock-In-Thermography is a common technique for determining local stresses in cyclic-loaded components. This so-called Thermographic Stress Analysis (TSA) uses the cyclic change of the temperature, which results from the elastic stress by the thermoelastic effect. To reduce the noise in the measured temperature signal, the evaluation is performed using a Discrete Fourier Transformation. Brémond [1] and Sakagami [2] have shown that in case of plastic deformation a second mode, coupled with the double loading frequency appears in the DFT-evaluation. This part is known as the so-called D-Mode and is assigned to dissipative energies. Investigations of Bär et al. [3] have shown that there are discrepancies in the elastic and dissipative temperature changes between the Lock-In evaluation and an analytical evaluation, showing that the Lock-In evaluation is just qualitatively but not quantitatively correct. In this study a detailed study of the temperature changes in the vicinity of a crack in AISI 316L was undertaken. A determination of temperature-force hysteresis was carried out on a precracked specimen. The comparison of temperature-force hysteresis based on a frequency synthesis of the different modes of the Lock-In evaluation with an analytical evaluation showed only an approximate match. The compensation of the thermoelastic effect with force proportional local stress changes uncovers the dissipative temperature behavior at the crack. A simple isolation of the stress change or rather the dissipative temperature changes out of the E Mode and D-Mode is not generally possible. Crack opening and compressive loads cause thermoelastic temperature changes, which affect the E-Mode as well as the D-Mode and higher harmonic D k -Modes. © 2020 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 23 European Conference on Fracture - ECF23 Keywords: Fatigue; Crack propagation; Thermography i t i t i i l l t i li l t . i ll i t l i t li t t t , i lt t l ti t t t l ti t. t i i t t t i l, t l ti i i i t i ti . i t t i l ti ti , l it t l l i i t l ti . i t i t ll i i t i i ti i . ti ti t l. t t t i i i t l ti i i ti t t t t l ti l ti l l ti , i t t t l ti i j t lit ti l t t tit ti l t. t i t t il t t t t i t i i it i t . t i ti t t t i i t i . i t t t i t i t i t t l ti it l ti l l ti l i t t . ti t t l ti t it ti l l l t t i i ti t t i t t . i l i l ti t t t t i i ti t t t t i t ll i l . i i l t l ti t t , i t t ll t i i . t . li l ie . . This is an open access article under the CC BY-NC-ND license (http:// ti . /li / / . / Peer-review under responsibility of 23 European Conference on Fracture - ECF23 : ti ; r r ti ; r r 23 European Conference on Fracture - ECF23 Measurement of Elastic Stresses and Dissipated Energies at Cracks Is the Lock-In-Evaluation an Appropriate Tool? Jürgen Bär * and Ralf Urbanek Universität der Bundeswehr München, Institute of Materials Science, D-85577 Neubiberg, Germany i it t , I tit t f t i l i , - i ,

* Corresponding author. Tel.: +49 89 6004-2561; fax: +49 89 6004-3055. E-mail address: juergen.baer@unibw.de i t r. l.: - ; f : - . - il : j r . r i . rr

2452-3216 © 2020 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 23 European Conference on Fracture - ECF23 l i r . . i i rti l r t - - li ( tt :// r ti . r /li / - - / . /) i i ilit t - t r . li

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 the scientific committee of the 23 European Conference on Fracture – ECF23 10.1016/j.prostr.2022.12.134