PSI - Issue 17

Available online at www.sciencedirect.com 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 ScienceDirect

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Procedia Structural Integrity 17 (2019) 308–315

ICSI 2019 The 3rd International Conference on Structural Integrity Determination of dissipated energies during fatigue tests on Copper and AA7475 with Infrared Thermography Jürgen Bär*, Luca Seilnacht, Ralf Urbanek University of the Bundeswehr Munich, Institute for Materials Science, D-85577 Neubiberg, Germany ICSI 2019 The 3rd International Conference on Structural Integrity Determination of dissipated energies during fatigue tests on Copper and AA7475 with Infrared Thermography Jürgen Bär*, Luca Seilnacht, Ralf Urbanek University of the Bundeswehr Munich, Institute for Materials Science, D-85577 Neubiberg, Germany In this work, detailed studies of the temperature change caused by dissipative energies within a loading cycle were performed on oxygen free copper and the aluminum alloy AA7475 T761. The temperature changes within a loading cycle were recorded with a high speed thermography camera. To determine the temperature changes due to dissipative effects, the thermoelastic effect is subtracted from the measured temperature. The corresponding thermoelastic constant is determined in an experiment with a pure elastic loading of the specimen. Force controlled experiments showed that the heating effect in a cycle decreases until an equilibrium temperature is reached. This clearly indicates a direct relation between the strain and the heating effect within a cycle. Compared to pure tension loading (R > 0) under fully reversed loading (R = -1) a higher heating can be observed, caused by an additional heating effect in compression. The equilibrium temperature increases with the loading frequency. This effect can be contributed to a decreasing cooling time within a loading cycle. The amount of dissipated energy was found to be independent of the loading frequency. The temperature change within a cycle can be described by a simple model basing on the mechanical and physical properties of the material. The investigations have shown that the detailed analysis of the temperature change within a loading cycle can provide interesting information about the amount and the time when energy is dissipated in a loading cycle. This enables a more detailed study of the fatigue behaviour of metallic materials and can provide valuable data for the prediction of the cyclic lifetime. In this work, detailed studies of the temperature change caused by dissipative energies within a loading cycle were performed on oxygen free copper and the aluminum alloy AA7475 T761. The temperature changes within a loading cycle were recorded with a high speed thermography camera. To determine the temperature changes due to dissipative effects, the ther oelastic effect is subtracted from the measured temperature. The corresponding thermoelastic constant is determined in an experiment with a pure elastic loading of the specimen. Force controlled experiments showed that the heating effect in a cycle decreases until an equilibrium temperature is reached. This clearly indicates a direct relation between the strain and the heating effect within a cycle. Compared to pure tension loading (R > 0) under fully reversed loading (R = -1) a higher heating can be observed, caused by an additional heating effect in compression. The equilibrium temperature increases with the loading frequency. This effect can be contributed to a decreasing cooling time within a loading cycle. The amount of dissipated energy was found to be independent of the loading frequency. The temperature change within a cycle can be described by a simple model basing on the mechanical and physical properties of the material. The investigations have shown that the detailed analysis of the temperature change within a loading cycle can provide interesting information about the amount and the time when energy is dissipated in a loading cycle. This enables a more detailed study of the fatigue behaviour of metallic materials and can provide valuable data for the prediction of the cyclic lifetime. Abstract Abstract

© 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ICSI 2019 organizers. © 2019 The Authors. Published by Elsevier B.V. Peer-review nder responsibility of the ICSI 2019 organizers. © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ICSI 2019 organizers.

2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ICSI 2019 organizers. 2452-3216 © 2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ICSI 2019 organizers. * Corresponding author. Tel.: +49-89-6004-2561; fax: +49-89-6004-3055. E-mail address: juergen.baer@unibw.de * Corresponding author. Tel.: +49-89-6004-2561; fax: +49-89-6004-3055. E-mail address: juergen.baer@unibw.de

2452-3216  2019 The Authors. Published by Elsevier B.V. Peer-review under responsibility of the ICSI 2019 organizers. 10.1016/j.prostr.2019.08.041