PSI - Issue 54

Available online at www.sciencedirect.com Available online at www.sciencedirect.com ScienceDirect Structural Integrity Procedia 00 (2023) 000–000

www.elsevier.com/locate/procedia

ScienceDirect

Procedia Structural Integrity 54 (2024) 188–195

© 2023 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 ICSI 2023 organizers Abstract The early detection of cracks in fatigue experiments on specimens with round cross-sections is often difficult to perform. Due to the unknown location of the crack initiation site on the circumference of the specimen displacement measurements or potential drop measurements do not provide satisfactory results. Previous investigations (Hartweg und Bär 2019; Nahbein und Bär 2022) have shown that cracks can be detected and localized early using a multiple potential probe measurement in combination with a simple geometrical model in which the measured potential drop values are treated as vectors. In this work, the possibilities for determining the crack size that result from this method are examined. The experimental verification was undertaken by fatigue experiments on a high alloyed steel. The crack size and shape were marked on the fracture surface with overloads introduced in defined intervals. The initiation of cracks at defined positions was forced by introducing notches with an engraving laser. The crack size was determined from the mean value of the three potentials as well as the radius coordinate of the normal vector. For the calculation of the crack depth two different equations were investigated. The equation proposed by Tiedemann (Tiedemann 2016) shows better agreement with the experimental data than the widely used Johnson equation (Johnson 1965). The investigations have shown that the use of the radius coordinate of the normal vector in conjunction with the equation proposed by Tiedemann is the optimal solution for determining the crack depth in round specimens by means of multiple potential drop measurements. © 2023 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 ICSI 2023 organizers Keywords: Fatigue; Crack detection, Potential Drop Measurement International Conference on Structural Integrity 2023 (ICSI 2023) Crack Detection and Crack Size Measurement in Round Specimen using Multiple Potential Drop Measurements Jürgen Bär Universität der Bundeswehr München, Institute of Materials Science, D-85577 Neubiberg, Germany

Nomenclature a

Crack depth

a 0 Depth of the secondary notch d Diameter of the specimen in the notch root � Normal vector

2452-3216 © 2023 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 ICSI 2023 organizers

2452-3216 © 2023 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 ICSI 2023 organizers 10.1016/j.prostr.2024.01.072