Failure analysis of LCF cracked medium-voltage switch bellows
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B. Fischer
Boromir Fischer completed a training as State Certified Technical Assistant for Metallography and Physical Material Analysis at Lette-Verein in Berlin. He has worked in the metallographic laboratory of the Siemens Gas Turbine Plant (Siemens-Gasturbinenwerk) Berlin for more than a decade. The key areas of his work are failure analysis and microstructural examinations using the field emission scanning electron microscope.Madeleine Giller Apprenticeship as a materials testing technician at the welding institute SLV Berlin-Brandenburg. After that, she studied materials science at the Berlin Institute of Technology. She graduated with a masters degree in materials science in 2012. Since November 2012 employment as engineer at the Metallography Laboratory of the Siemens Gas Turbine Works in Berlin. She has been appointed laboratory manager within the Berlin Testing Center of the Large Gas Turbine Engineering Group in 2014. Her main fields of expertise comprise failure analysis and micro-structural investigations using the field emission scanning electron microscope.
Abstract
Three cracked spring bellows used for medium voltage switches were subjected to materialographic examinations. They were installed in switches that were tested in the test facility performing simulated switching cycles and failed prematurely. The number of load cycles until crack initiation is not known. However, it was well under 10,000. The cause of the crack was low-cycle fatigue (LCF) induced by wall thinning wear resulting from a relative movement between the bellow and the inner polytetrafluoroethylene (PTFE) sleeve. Hot cracking characteristics or evidence of other fracture mechanisms were not found.
Kurzfassung
Drei gerissene Federbälge für Mittelspannungsschalter wurden werkstofftechnisch untersucht. Sie waren in Schaltern eingebaut, die im Prüffeld mittels simulierter Schaltspiele getestet wurden und versagten vorzeitig. Die Lastspielzahl bis zur Risseinleitung ist nicht bekannt, betrug aber deutlich unter 10 000. Die Rissursache war niederzyklische Ermüdung (LCF), verursacht durch wandausdünnenden Verschleiß infolge Relativbewegung zwischen Wellrohr und innerer Hülse aus PTFE. Keinerlei Heißrissmerkmale oder Hinweise auf andere Rissmechanismen wurden gefunden.
About the authors
Boromir Fischer completed a training as State Certified Technical Assistant for Metallography and Physical Material Analysis at Lette-Verein in Berlin. He has worked in the metallographic laboratory of the Siemens Gas Turbine Plant (Siemens-Gasturbinenwerk) Berlin for more than a decade. The key areas of his work are failure analysis and microstructural examinations using the field emission scanning electron microscope.
Madeleine Giller Apprenticeship as a materials testing technician at the welding institute SLV Berlin-Brandenburg. After that, she studied materials science at the Berlin Institute of Technology. She graduated with a masters degree in materials science in 2012. Since November 2012 employment as engineer at the Metallography Laboratory of the Siemens Gas Turbine Works in Berlin. She has been appointed laboratory manager within the Berlin Testing Center of the Large Gas Turbine Engineering Group in 2014. Her main fields of expertise comprise failure analysis and micro-structural investigations using the field emission scanning electron microscope.
References / Literatur
[1] Neidel, A.; Fischer, B.; Giller, M.; Gädicke, T.: Ursachenanalyse an 3 Federbälgen mit Rissen. Interner Bericht BLN MT/2023/0312. Berlin, 31.07.2023.Search in Google Scholar
[2] ASM Handbook, Vol. 11: Failure Analysis and Prevention, Sixth printing, American Society for Metals, Handbook Committee, 1998.Search in Google Scholar
[3] Lange, G.: Systematische Beurteilung technischer Schadensfälle. 3. Auflage, DGM, 1992.Search in Google Scholar
[4] Grosch, J.: Schadenskunde im Maschinenbau. 4. Auflage, Expert Verlag, 2004.Search in Google Scholar
[5] Engel, L.; Klingele, H.: Rasterelektronenmikroskopische Untersuchungen von Metallschäden, Gerling Institut für Schadensforschung und Schadensverhütung, 1974 R.Search in Google Scholar
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Articles in the same Issue
- Contents
- Editorial
- Editorial
- Microstructural characteristics and mechanical properties of WAAM components
- Grain size characterization of nickel alloy 718 with optimized metallographic sample preparation route followed by a novel etching technique
- High-resolution microscopy of biofilm and bacteria on titanium implants
- Failure Analysis
- Failure analysis of LCF cracked medium-voltage switch bellows
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- News
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