How to Deal with Very High Cycle Fatigue (VHCF) Effects in Practical Applications?*

Manfred Bacher-Hoechst; Stephan Issler

doi:10.3139/120.110387

Article

How to Deal with Very High Cycle Fatigue (VHCF) Effects in Practical Applications?^*

Manfred Bacher-Hoechst and Stephan Issler

Published/Copyright: May 26, 2013

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From the journal Materials Testing Volume 54 Issue 11-12

Abstract

Fatigue designing of high-stressed engine components is a key factor for reliable power train systems in automotive industry. In this context load assumptions are very important since this is attended with a pre-designing of important machine elements. Load analyses are usually performed by using experimental methods since the accuracy of load simulations are often not precise enough. An example for VHCF problems occurs in modern high pressure pumps for gasoline direct injection systems, which have load spectra with a large amount of cycles up to 10⁹ including a very powerful shape of the spectra. At the same time it is necessary to consider the properties of fuels in service since they might affect the fatigue strength significantly. For example, ethanol-based gasoline fuels are used in a lot of countries worldwide and especially their additives may lead to significant corrosion fatigue effects. In addition, it is well known that material inclusions play an important role for the VHCF behaviour especially for high-strength steels. This paper deals with possibilities to avoid VHCF problems of components in service to maintain reliable systems.

Kurzfassung

Das Ermüdungsdesign von hochbeanspruchten Motorkomponenten ist ein Schlüsselfaktor für zuverlässige Antriebsstränge in der Automobilindustrie. In diesem Kontext sind Lastannahmen sehr bedeutend, da diese mit dem Vordesgin von wichtigen Maschinenelementen zusammenhängen. Lastanalysen werden üblicherweise mit experimentellen Methoden durchgeführt, da die Lastsimulationen oft nicht präzise genug sind. Beispielsweise treten VHCF-Schwierigkeiten bei modernen Kraftstoff-Direkteinspritzsystemen auf, diese haben Lastspektren mit einer hohen Zyklenzahl von bis zu 10⁹ zusammen mit einer sehr leistungsstarken Form der Spektren. Gleichzeitig ist es notwendig die Eigenschaften von Kraftstoffen während des Betriebes zu berücksichtigen, da diese das Ermüdungsverhalten signifikant beeinflussen können. Beispielsweise werden in vielen Ländern Ethanol-basierte Kraftstoffe verwendet, und insbesondere deren Additive können zu signifikanten Schwingungsrisskorrosionserscheinungen führen. Darüber hinaus ist wohl bekannt, dass Materialeinschlüsse eine wichtige Bedeutung für das VHCF-Verhalten insbesondere von hochfesten Stählen haben. Dieser Beitrag behandelt Möglichkeiten, um VHCF-Schwierigkeiten im Betrieb von Komponenten zu vermeiden und um so zuverlässigere Systeme zu erhalten.

Extended Version of the Contribution to VHCF 5

Dr. Manfred Bacher-Hoechst was born in 1953 in Muelheim/Ruhr, Germany, graduated as mechanical engineer at KIT Karlsruhe in 1983 and finished his PhD in 1987 concerning deformation and fracture behaviour of case hardened steels. Since 1988 he is working at Robert Bosch GmbH, Stuttgart, Corporate Research and Advance Engineering, Materials and Process Engineering Metals, as director. His main research and development topics are new metallic materials, simulation methods for fatigue as well as lifetime design and testing technology concerning structural metals and components. From 1989 to 1998 he held lectures at the University for Applied Sciences, Esslingen, Germany. From 2008 to 2011 he was president of the German Association for Materials Research and Testing (DVM).

Dr. Stephan Issler was born in 1969 in Stuttgart, graduated as mechanical engineer at University of Stuttgart, Germany, in 1996 and finished his PhD in 2001 dealing with fatigue designing methods for the life assessment of gas turbines. From 2000 to 2005 he worked at DaimlerChrysler AG, Mercedes-Benz Technology Center, Sindelfingen, responsible for the fatigue testing of cars and body components. Since 2005 he is working at Robert Bosch GmbH, Stuttgart, Corporate Research and Advance Engineering, Materials and Process Engineering Metals, as senior program manager. His main research and development topics are simulation and testing methods for fatigue as well as lifetime design concerning structural components, respectively.

References

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Published Online: 2013-05-26

Published in Print: 2012-11-01

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https://doi.org/10.3139/120.110387