Journal Published Online: 11 August 2015
Volume 44, Issue 1

Alternative Approach for Strain Measurement and Control in Fatigue Tests at Elevated Temperature



For strain-controlled fatigue tests, especially at elevated temperature, implementation of knife-edges and punching dimples within the gauge length of a specimen is a common practice to mount the extensometer. Premature failure on the test section of the specimens might be introduced by implementing these techniques. In this paper, an alternative approach is introduced to control and measure the strains in fatigue tests. Two dimples outside the gauge-length section are punched and used to mount the extensometer. The correlation between the controlled (measured) strain and the strain within the gauge-length section is established. For the isothermal fatigue tests (strain cycling at constant elevated temperature), the correlation can be established either through analytical analysis or finite-element analysis (FEA). By comparing the hysteresis loops obtained through the correlation and the one directly measured within the gauge length, it is found that the established correlation obtained from FEA has better agreement with the latter result. In addition, this technique can also be used for thermal-mechanical fatigue (TMF) tests (both temperature and strain cycling). However, it is found that the correlation developed through FEA does not give accurate result. Therefore, the interconnection should be established through a cyclic test, in which two extensometers are mounted on the specimen, one measures the strain within the gauge length and the other measures the strain outside the gauge length.

Author Information

Chen, Jie
Mechanical Engineering, Univ. of Alberta, Edmonton, CA
Xia, Zihui
Mechanical Engineering, Univ. of Alberta, Edmonton, CA
Pages: 13
Price: $25.00
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Stock #: JTE20140132
ISSN: 0090-3973
DOI: 10.1520/JTE20140132