In situ Fatigue in an Environmental Scanning Electron Microscope – Potential and Current Limitations
Biallas, Gerhard and Maier, Hans Jürgen (2007) In situ Fatigue in an Environmental Scanning Electron Microscope – Potential and Current Limitations. International Journal of Fatigue, 29 (8), pp. 1413-1425. DOI: 10.1016/j.ijfatigue.2006.11.008.
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The present study provides a survey on in-situ fatigue devices suitable for loading specimens in a scanning electron microscope (SEM). Particular emphasis is placed on the experimental methods employed to operate a small-scale load frame in an environmental SEM (ESEM). Specimen design and surface preparation, various modes of conducting the fatigue tests, specimen heating and imaging at elevated temperatures are considered. In addition, recent data from in-situ fatigue studies conducted in an ESEM between room temperature and 600 °C are summarized. Fatigue tests conducted on AM60B cast magnesium demonstrate a substantial environmental effect on cyclic deformation and fatigue damage evolution even at room temperature. Fatigue behaviour of high-temperature titanium alloy IMI 834 at 400 °C illustrates a completely different effect of environment on slip band formation and crack nucleation as compared to AM60B. Investigations performed on IMI 834 at 600 °C reveal current limitations of the in-situ fatigue technique applied. An approach to overcome these limitations is discussed. Ambient conditions can be simulated in an ESEM using pure water vapour atmosphere at a pressure similar to the partial pressure of the ambient environment. This is demonstrated for AM60B at room temperature and IMI 834 at 400 °C. However, this approach cannot necessarily be applied to all other material/environment combinations as is exemplarily shown for in-situ fatigue loading of IMI 834 at 600 °C. Data obtained from in-situ fatigue testing are compared to those from post-mortem SEM studies of failed specimens, which portray a wrong impression in certain cases. Experimental issues specific to environmental in-situ testing at elevated temperatures are addressed as are the ramifications of such tests with respect to modelling of fatigue life.
|Title:||In situ Fatigue in an Environmental Scanning Electron Microscope – Potential and Current Limitations|
|Journal or Publication Title:||International Journal of Fatigue|
|In ISI Web of Science:||Yes|
|Page Range:||pp. 1413-1425|
|Keywords:||In-situ fatigue, cast magnesium, AM60B, high-temperature titanium alloy, IMI 834, environmental degradation, fatigue mechanisms, microstructure, crack initiation, small crack growth, damage evolution|
|HGF - Research field:||Aeronautics, Space and Transport|
|HGF - Program:||Aeronautics|
|HGF - Program Themes:||L AR - Aircraft Research|
|DLR - Research area:||Aeronautics|
|DLR - Program:||L AR - Aircraft Research|
|DLR - Research theme (Project):||L - Structures & Materials|
|Institutes and Institutions:||Institute of Materials Research > Mechanical Testing of Materials|
|Deposited By:||Dr.-Ing. Gerhard Biallas|
|Deposited On:||19 Apr 2007|
|Last Modified:||27 Apr 2009 13:22|
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