TY - JOUR A1 - Thomas, Hans-Martin A1 - Dey, Anika A1 - Heyder, R. A1 - Krull, R. T1 - Prüfverfahren zur Früherkennung von Rollkontaktermüdung in Schienen N2 - Ständige Betriebsbeanspruchungen der Eisenbahnschienen führen an den Rad-Schiene-Kontaktflächen zu Ermüdungserscheinungen des Materials. Infolgedessen entstehen unter anderem an bogenäußeren Schienenfahrkanten Rollkontaktermüdungsrisse, auch genannt Head Checks. Zur frühzeitigen zerstörungsfreien Prüfung der Ermüdungsrisse wird das Wirbelstromverfahren eingesetzt. Neben der Detektion von Rissen, reagiert die Wirbelstromprüfung außerdem sehr empfindlich auf Veränderungen von Materialeigenschaften, wodurch sich Verfestigungen auch ohne jedes Vorhandensein von Ermüdungsrissen nachweisen lassen. Längerfristige Beobachtungen haben gezeigt, dass die Wirbelstromprüfung das Potential besitzt, mögliche Orte der Entstehung von Ermüdungsrissen in einem extrem frühzeitigen Stadium nachzuweisen. KW - Wirbelstromprüfung KW - Rollkontaktermüdung KW - Head Checks KW - Eisenbahnschienen KW - Kaltverfestigung PY - 2008 SN - 0013-2810 IS - 11 SP - 27 EP - 33 PB - Eurailpress Tetzlaff-Hestra CY - Hamburg AN - OPUS4-18381 LA - deu AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Thomas, Hans-Martin A1 - Dey, Anika A1 - Heyder, R. T1 - Eddy current test method for early detection of rolling contact fatigue (RCF) in rails N2 - The findings indicate that rolling contact fatigue with consecutive head checks develops preferentially in rail sections that have experienced operational work-hardening. Such hardening can be identified by instruments measuring the increased hardness values with respect to the base material. Eddy current testing was initially introduced with the aim to detect head checks and determine their damage depth. Because the material texture influences eddy current flow in the test objects very strongly, variations in hardness can easily be visualised using this method. Thus, in principle, it is possible to predict places where head checks will emerge later. This knowledge may be very helpful in improving our understanding of head check emergence under real conditions. This knowledge may also help in developing new and effective precautionary maintenance strategies. KW - Rails KW - Rolling contact fatigue KW - Head checks KW - Non-destructive testing KW - Eddy current technique PY - 2010 DO - https://doi.org/10.1784/insi.2010.52.7.361 SN - 0007-1137 VL - 52 IS - 7 SP - 361 EP - 365 PB - British Institute of Non-Destructive Testing CY - Northampton AN - OPUS4-21934 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Schlichting, Joachim A1 - Ziegler, Mathias A1 - Dey, Anika A1 - Maierhofer, Christiane A1 - Kreutzbruck, Marc T1 - Efficient data evaluation for thermographic crack detection N2 - We present an all-purpose crack detection algorithm for flying spot thermography which is directly applicable to a thermogram sequence without the need of any additional information about the experimental setup. A single image containing distinct crack signatures is derived in two steps. Firstly, the spatial derivative is calculated for each frame of the sequence and, secondly, the resulting data set is sorted pixel wise along the time axis. The feasibility of the proposed procedure is proven by testing a piece of rail that comprises roll contact fatigue cracks and by comparing the results with magnetic particle testing. KW - Active thermography KW - Laser scanner KW - Railway KW - Roll contact fatigue KW - Open surface cracks PY - 2011 SN - 1768-6733 VL - 8 IS - 1 SP - 119 EP - 123 PB - Lavoisier CY - Cachan Cedex AN - OPUS4-24255 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -