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Scatter in Dwell Time Cracking for a Ni-Based Superalloy in Combination With Overloads
Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
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2016 (English)In: Journal of engineering for gas turbines and power, ISSN 0742-4795, E-ISSN 1528-8919, Vol. 138, no 1, 012502-012502 p.Article in journal (Refereed) Published
Abstract [en]

In this paper, scatter in crack growth for dwell time loadings in combination with overloads has been investigated. Multiple tests were performed for surface cracks at 550 °C in the commonly used high temperature material Inconel 718. The test specimens originate from two different batches which also provide for a discussion of how material properties affect the dwell time damage and overload impact. In combination with these tests, an investigation of the microstructure was also carried out, which shows how it influences the growth rate. The results from this study show that, in order to take overloads into consideration when analyzing spectrum loadings containing dwell times, one needs a substantial amount of material data available as the scatter seen from one batch to the other are of significant proportions.

Place, publisher, year, edition, pages
ASME Press, 2016. Vol. 138, no 1, 012502-012502 p.
National Category
Mechanical Engineering Materials Engineering Applied Mechanics
Identifiers
URN: urn:nbn:se:liu:diva-121007DOI: 10.1115/1.4031157ISI: 000371127900013OAI: oai:DiVA.org:liu-121007DiVA: diva2:850762
Note

Funding agencies: Swedish Energy Agency; Siemens Industrial Turbomachinery AB; GKN Aerospace Engine Systems; Royal Institute of Technology through Swedish research programme TURBO POWER

Available from: 2015-09-02 Created: 2015-09-02 Last updated: 2016-03-21Bibliographically approved
In thesis
1. High Temperature Fatigue Crack Growth in a Ni-based Superalloy: Modelling Including the Interaction of Dwell Times
Open this publication in new window or tab >>High Temperature Fatigue Crack Growth in a Ni-based Superalloy: Modelling Including the Interaction of Dwell Times
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Safe life of gas turbines is always of major concern for manufacturers in order to ensure passenger safety and stable continuous power output. An increasing amount of resources have been put into research and development to assure that all safety aspects are covered in the design of new turbines and to ensure that enough frequent service intervals are scheduled to avoid complications. Many of these issues require good knowledge of material properties and of how to use these in the design process. Some of these relate to fatigue which is of major concern in all parts of a development programme. However, while some fatigue problems have been extensively studied, some have not. One example is crack growth with influence of dwell times at elevated temperature in combination with cyclic loading. Such loading conditions have been shown to give a different cracking behaviour compared to rapid cyclic loading, increasing the growth rate significantly with respect to the number of load cycles. Improved models for predicting this behaviour is therefore of major interest for gas turbine manufacturers, and could substantially increase the reliability. As a result, more research is needed in order  solve these problems.

The work presented in this dissertation has focused on how to predict life under the above-mentioned circumstances. The materials used in high temperature gas turbine applications are often nickel-based superalloys, and in this work the most common one, Inconel 718, has been studied. Mechanical experiments have been performed under operation like conditions in order to receive material data for the subsequent modelling work. The modelling approach was chosen such that the underlying physics of the dwell time cracking have been incorporated on a phenomenological basis, creating a model which can be physically motivated as well as used for industrial applications. The main feature of the modelling work has been to track material damage which is received from dwell times, how this interacts with cyclic loading and how it affects the crack growth rate, thus creating a load history dependent model.

The outcome of this work has resulted in a model which is both easy to use and which has shown to give good correlation to available experimental data. Key components such as calibration for cheap and easy parameter determination, validation on complex engine spectra loadings, three dimensional crack growth, overload influences, material scatter, thermo-mechanical fatigue crack growth and the impact of high cycle fatigue loadings, are all covered in the presented work, both as experimental findings and as continuous development of the modelling concept.

The dissertation consists of two parts. In the first an introduction with the theory and background to crack growth with dwell times is given, while the second part consists of 10 papers.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2015. 51 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1681
National Category
Mechanical Engineering Applied Mechanics Materials Engineering
Identifiers
urn:nbn:se:liu:diva-121012 (URN)10.3384/diss.diva-121012 (DOI)978-91-7519-034-1 (Print) (ISBN)
Public defence
2015-09-11, C3, Hus C, Campus Valla, Linköping, 10:15 (English)
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Available from: 2015-09-02 Created: 2015-09-02 Last updated: 2015-09-02Bibliographically approved

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Storgärds, ErikSaarimäki, JonasSimonsson, KjellSjöström, SörenMoverare, Johan
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