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SteBLife – A new short-time procedure for the calculation of S-N curves and failure probabilities

  • Peter Starke , Alexander Bäumchen and Haoran Wu
Published/Copyright: July 3, 2018
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Materials Testing
From the journal Materials Testing Volume 60 Issue 2

Abstract

A fast calculation of Wöhler or S-N curves is of major importance in the design process of complex components and for selection of optimized materials. In the context of this work, it is shown how the nondestructive testing methods, the digitalization of the measurement techniques as well as signal processing can be combined with a new short-time procedure in order to acquire potentially more information from fatigue processes, while experimental effort and costs are reduced significantly. The results of this combination show not only considerable advantages over conventional methods aimed at determining S-N curves, but also over established short-term procedures, due to the possibility to separate several material mechanisms by means of data analysis and to use this for fatigue life calculations based on the results of a few specimens only. The SteBLife approach is a new short-time calculation method developed at the Chair of Nondestructive Testing and Quality Assurance at Saarland University, Germany, which takes into account that there is no linear relation between the elastic, elastic-plastic and plastic portion of the material response in the deformation process. With respect to the test strategy, the number of fatigue tests can be reduced for SteBLifemtc and SteBLifemsb to three and five, respectively, or in the case of SteBLifestc to one single constant amplitude test with a special step-shaped specimen geometry when compared with approximately 15 required fatigue tests for the conventional determination of Wöhler or S-N curves. Moreover, SteBLifemsb offers the possibility to calculate scatter bands for different failure probabilities, which is an important feature, even in the case of inhomogeneous materials. Within the scope of the presented work, the change in temperature of SAE 1045 (C45E) specimens was measured during fatigue tests by an infrared camera in order to feed the thermal response back into the new SteBLife approach for a reliable fatigue life calculation.

Kurzfassung

Eine zeiteffiziente Ermittlung von Wöhler- oder S-N Kurven ist wesentlich für die Auslegung komplexer Bauteile sowie für eine optimierte Materialauswahl. Im Rahmen dieser Arbeit wird gezeigt, wie zerstörungsfreie Prüfverfahren, Digitalisierung der Messtechnik sowie die Signalverarbeitung mit einem neuen Kurzzeitverfahren kombiniert werden können, um potenziell mehr Informationen aus dem Ermüdungsverhalten zu gewinnen, während gleichzeitig der experimentelle Aufwand und die Kosten erheblich reduziert werden. Die Ergebnisse dieser zuvor beschriebenen Kombination zeigen nicht nur erhebliche Vorteile gegenüber herkömmlichen Methoden zur Ermittlung von Wöhler-Kurven, sondern auch gegenüber etablierten Kurzzeitverfahren, da hierbei unterschiedliche Werkstoffmechanismen mittels Datenanalyse separiert werden können. Durch diesen Ansatz können auf der Basis weniger Versuche Aussagen zur Lebensdauer eines Werkstoffes getroffen werden. Der SteBLife-Ansatz ist eine neue Kurzzeitberechnungsmethode, die am Lehrstuhl für Zerstörungsfreie Prüfung und Qualitätssicherung der Universität des Saarlandes entwickelt wurde. Dabei wird berücksichtigt, dass im Verformungsverhalten eines metallischen Werkstoffes zwischen dem elastischen, elastisch-plastischen und plastischen Anteil kein linearer Zusammenhang besteht. Im Bezug auf die vorgestellten Versuchsstrategien kann die Anzahl der Ermüdungsversuche für SteBLifemtc und SteBLifemsb auf drei bis fünf bzw. für SteBLifestc auf einen einzigen Ermüdungsversuch mit einer speziellen stufenförmigen Probe reduziert werden, wohingegen die konventionelle Ermittlung von Wöhler oder S-N Kurven ca. 15 Ermüdungsversuche erfordert. Darüber hinaus bietet SteBLifemsb die Möglichkeit, Streubänder für unterschiedliche Ausfallwahrscheinlichkeiten zu berechnen, was gerade bei inhomogenen Werkstoffen eine wichtige Funktion darstellt. Im Rahmen der vorgestellten Arbeit wird die Temperaturänderung von Proben aus C45E in Ermüdungsversuchen mittels einer Infrarotkamera gemessen und diese Werkstoffantwort in der neuen SteBLife-Methode für eine zuverlässige Lebensdauerberechnung genutzt.

*Correspondence Address, Dr.-Ing. Peter Starke, Chair of Non-Destructive Testing and Quality Assurance, Saarland University, Am Markt Zeile 4, D-66125 Saarbrücken, E-mail:

Dr.-Ing. Peter Starke, born in 1977, studied Mechanical Engineering at University of Kaiserslautern, Germany. Since 2002, he has been a research assistant at the Chair of Materials Science and Engineering, University of Kaiserslautern. He received his engineering doctoral degree in 2007 working on “The fatigue life calculation of metallic materials under constant mplitude loading and service loading”. From 2007 to 2013, he worked as the Head of “Fatigue life calculation” group at University of Kaiserslautern. Since 2013, he is a senior research associate at the Chair of Non-Destructive Testing and Quality Assurance at Saarland University, Germany. His research is mainly focused on the use of nondestructive measurement techniques for the characterization of the fatigue behavior and the fatigue life calculation of metallic and nonmetallic materials in the LCF, HCF and VHCF regime as well as for the evaluation of defects and inhomogeneities in material microstructures.

Alexander Bäumchen, born in 1994, is studying Materials Science and Engineering at Saarland University in Saarbrücken, Germany.

Haoran Wu, born in 1988, studied Materials Science and Engineering at Tianjin University, China and Saarland University in Saarbrücken, Germany. After that, he received his master degree from Saarland University in 2016, he works at the Chair of Nondestructive Testing and Quality Assurance (LZfPQ), where he finished his by DGZfP (The German Society for Non-Destructive Testing) rewarded master thesis. He is currently working as a research associate with focus on NDT methods and material fatigue.

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Published Online: 2018-07-03
Published in Print: 2018-02-02

© 2018, Carl Hanser Verlag, München

Articles in the same Issue

  1. Inhalt/Contents
  2. Contents
  3. Fachbeiträge/Technical Contributions
  4. SteBLife – A new short-time procedure for the calculation of S-N curves and failure probabilities
  5. Surface treatment for effective bonding in the sports industry
  6. Effect of different rotational speeds on mechanical and metallurgical properties of friction welded dissimilar steels
  7. Comparison of titanium and FGM dental implants with different coating types
  8. Weld quality and productivity of AISI 4140 steel welded by unpulsed and pulsed GMAW
  9. Corrosion behavior of Hastelloy® C–4® Ni–Cr–Mo–Fe alloys for coal gasification syngas plants
  10. Application of FactSage® thermodynamic modeling for predicting the ash transformation with temperatures under partial slagging entrained flow coal gasification condition
  11. Röntgen- und Neutronentomographie am knöchernen Innenohr der Bartenwale
  12. Partial repair of thermally sprayed and sealed corrosion protection – Organic coating material or thermal spraying?
  13. Experimental study on solidification of Cu(II)-contaminated soil using red mud with cement and Ca(OH)2
  14. Tribological study of sintered iron based and copper based brake materials by pin-on-disc method
  15. Influence of drilling parameters on temperature and surface roughness of AISI O2 steel
  16. Multi-fractal characteristics of particle size distribution of granular backfilling materials under different loads
  17. Dry sliding behavior of aluminum alloy 8011 with 4 % fly ash
  18. Optimization of the milling parameters for an Al/Si3N4 functionally graded composite using grey relational analysis
https://doi.org/10.3139/120.111139

Articles in the same Issue

  1. Inhalt/Contents
  2. Contents
  3. Fachbeiträge/Technical Contributions
  4. SteBLife – A new short-time procedure for the calculation of S-N curves and failure probabilities
  5. Surface treatment for effective bonding in the sports industry
  6. Effect of different rotational speeds on mechanical and metallurgical properties of friction welded dissimilar steels
  7. Comparison of titanium and FGM dental implants with different coating types
  8. Weld quality and productivity of AISI 4140 steel welded by unpulsed and pulsed GMAW
  9. Corrosion behavior of Hastelloy® C–4® Ni–Cr–Mo–Fe alloys for coal gasification syngas plants
  10. Application of FactSage® thermodynamic modeling for predicting the ash transformation with temperatures under partial slagging entrained flow coal gasification condition
  11. Röntgen- und Neutronentomographie am knöchernen Innenohr der Bartenwale
  12. Partial repair of thermally sprayed and sealed corrosion protection – Organic coating material or thermal spraying?
  13. Experimental study on solidification of Cu(II)-contaminated soil using red mud with cement and Ca(OH)2
  14. Tribological study of sintered iron based and copper based brake materials by pin-on-disc method
  15. Influence of drilling parameters on temperature and surface roughness of AISI O2 steel
  16. Multi-fractal characteristics of particle size distribution of granular backfilling materials under different loads
  17. Dry sliding behavior of aluminum alloy 8011 with 4 % fly ash
  18. Optimization of the milling parameters for an Al/Si3N4 functionally graded composite using grey relational analysis
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