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BY 4.0 license Open Access Published by De Gruyter September 26, 2018

Execution and evaluation of cyclic tests at constant load amplitudes – DIN 50100:2016

Dedicated to Professor Dr.-Ing. Harald Zenner on the occasion of his eightieth birthday

Ausführung und Auswertung zyklischer Versuche bei konstanten Amplituden – DIN 50100:2016
Rainer Masendorf and Christian Müller
From the journal Materials Testing

Abstract

Tests with constant load amplitudes are used to characterize the fatigue strength behavior of material specimens and components. The S-N curve derived from these test results describes the relationship between the load amplitude and the corresponding cycles to failure. Different concepts for carrying out and evaluating fatigue tests make it difficult to compare the results from different research institutes. The aim of the new version of the German standard DIN 50100:2016 is to define a procedure for determining an S-N curve for metallic alloys that does not allow any scope for interpretation. It is assumed that the test results are subject to logarithmic normal distributions in both load and cycle direction. It is further assumed that the S-N curve in the high-cycle fatigue regime and the long-life fatigue regime can be approximated by a bilinear function. For the determination of the straight line of finite life, the pearl string method and the load level method are available for determining the position parameter and the slope of the power function according to Basquin. Long-life fatigue strength is determined using the staircase method and forms the knee point of the S-N curve on average with the straight line of finite life. For the long-life fatigue regime, a horizontal course or a decrease with low inclination, depending on the material group examined, is assumed. In addition, DIN 50100:2016 contains information on the accuracy of the estimation of the mean values and the scatter of the characteristic values according to the sample size. The goal of achieving comparability of S-N curves is supported by extensive examples. An English translation of DIN 50100:2016 is available also.

Kurzfassung

Versuche mit konstanter Lastamplitude dienen zur Charakterisierung des Schwingfestigkeitsverhaltens von Werkstoffproben und Bauteilen. Die aus den Versuchsergebnissen abgeleitete Wöhlerlinie beschreibt den Zusammenhang von Lastamplitude und Lebensdauer. Unterschiedliche Konzepte zur Durchführung und Auswertung von Schwingfestigkeitsversuchen erschweren die Vergleichbarkeit von Ergebnissen verschiedener Forschungsstellen. Ziel der Neufassung von DIN 50100:2016 ist die Definition einer Vorgehensweise zur Ermittlung einer Wöhlerlinie, die keinen Interpretationsspielraum zulässt. Dazu wird angenommen, dass die Versuchsergebnisse sowohl in Lastrichtung als auch in Schwingspielzahlrichtung einer logarithmischen Normalverteilung unterliegen und der Verlauf der Wöhlerlinie im Zeit- und Langzeitfestigkeitsbereich durch eine bilineare Funktion angenähert werden kann. Für die Ermittlung der Zeitfestigkeitsgeraden stehen das Perlenschnur- und das Horizontenverfahren zur Verfügung, um Lage und Neigung der Potenzfunktion nach Basquin zu bestimmen. Die Langzeitfestigkeit wird im Treppenstufenverfahren ermittelt und bildet im Schnitt mit der Zeitfestigkeitsgerade den Knickpunkt der Wöhlerlinie. Im Langzeitfestigkeitsbereich wird ein horizontaler Verlauf oder ein Abfall mit geringer Neigung in Abhängigkeit von der untersuchten Werkstoffgruppe angenommen. Zusätzlich enthält DIN 50100:2016 Angaben zur Treffsicherheit der aus den Versuchsergebnissen geschätzten Mittelwerte und Streuungen in Abhängigkeit vom Stichprobenumfang. Durch umfangreiche Beispiele wird das Ziel, die Vergleichbarkeit von Wöhlerlinien zu erreichen, unterstützt. Eine englische Übersetzung von DIN 50100:2016 ist verfügbar.


*Correspondence Address, Dr.-Ing. Rainer Masendorf, Institut für Maschinelle Anlagentechnik, und Betriebsfestigkeit, TU Clausthal, Leibnizstraße 32, 38678 Clausthal-Zellerfeld, Germany, E-mail:

Dr.-Ing. Rainer Masendorf, born in 1964, studied Mechanical Engineering at Clausthal University of Technology (TUC), Germany and has been a scientific employee at the Institute for Plant Engineering and Fatigue Analysis (IMAB) of TUC since 1994. His PhD thesis (2000) considered the influence of the prestraining cyclic material properties of thin sheets. He has been a leading engineer at IMAB (TUC) in Clausthal, Germany since 2000. The focus of his work is fatigue testing of materials and components for determining fatigue properties.

Dr.-Ing. Christian Müller, born in 1984, studied Mechanical Engineering at Clausthal University of Technology (TUC) and was a scientific employee at the Institute for Plant Engineering and Fatigue Analysis (IMAB) of TUC between 2010 and 2015. He completed his PhD thesis on the statistical evaluation of S-N curves in 2015. Since then, he has worked in the field of the fatigue strength of high-voltage batteries at Audi Ingolstadt, Germany.


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Published Online: 2018-09-26
Published in Print: 2018-10-27

© 2018, Carl Hanser Verlag, München

This work is licensed under the Creative Commons Attribution 4.0 International License.

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