SYMPOSIA PAPER Published: 01 August 2022
STP163820210044

Crack Growth Measurements under Thermo-Mechanical Fatigue Loading Using Alternating Current Potential Drop

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Applying damage-tolerant design approaches requires a comprehensive understanding and reliable modeling of crack growth under service conditions. This in turn requires gathering the necessary database for model parametrization and validation from the observation of crack growth in component-like test piece geometries at service-like thermo-mechanical fatigue (TMF) conditions. A standard tool for gathering such information, employed in both research and industry, is the potential drop method. However, in combination with alternating temperature and power surges from heating devices, this method proves difficult. In recent years, the Institute for Materials Technology in Darmstadt, together with partners from the energy and aerospace industry, conducted various research projects on TMF crack growth in nickel alloys. One key element was the employment of the alternating current potential drop (ACPD) measurement technique to monitor crack growth during testing. This paper presents the measurement setup, the data assessment process, the validation results, and the most prominent findings from these projects. The data collection includes different standardized and individualized sample geometries made from multiple nickel alloys and heat-resistant steels and covers a temperature range from room temperature up to 1,100°C. The presentation of the experimental results is complemented by a theoretical evaluation of ACPD crack growth measurement using multiphysics finite element simulations. Through such modeling approaches, the effects of, for example, creep strain development or the di-electric material properties of different materials on crack growth measurement accuracy can be investigated. These approaches also help one gain a fundamental understanding of this still largely empirically based measuring technology.

Author Information

Kraemer, Karl, Michael
Institute for Materials Technology, Technical University Darmstadt, Darmstadt, DE
Brune, Timo
Institute for Materials Technology, Technical University Darmstadt, Darmstadt, DE
Mueller, Falk
Institute for Materials Technology, Technical University Darmstadt, Darmstadt, DE
Kontermann, Christian
Institute for Materials Technology, Technical University Darmstadt, Darmstadt, DE
Oechsner, Matthias
Institute for Materials Technology, Technical University Darmstadt, Darmstadt, DE
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Details
Pages: 160–185
DOI: 10.1520/STP163820210044
ISBN-EB: 978-0-8031-7724-6
ISBN-13: 978-0-8031-7723-9