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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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Abstract

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.

Document Type:Article
Title:In situ Fatigue in an Environmental Scanning Electron Microscope – Potential and Current Limitations
Authors:
AuthorsInstitution or Email of Authors
Biallas, GerhardUNSPECIFIED
Maier, Hans JürgenUniversität Paderborn
Date:2007
Journal or Publication Title:International Journal of Fatigue
Refereed publication:Yes
In ISI Web of Science:Yes
Volume:29
DOI:10.1016/j.ijfatigue.2006.11.008
Page Range:pp. 1413-1425
Status:Published
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 (old)
HGF - Program:Aeronautics
HGF - Program Themes:Aircraft Research
DLR - Research area:Aeronautics
DLR - Program:L AR - Aircraft Research
DLR - Research theme (Project):L - Structures & Materials
Location: Köln-Porz
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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