Summary
It is generally accepted that relatively simple mechanical tests to measure a material property should be carried out in a standard way in order to provide a consistent basis for comparison of data for design or quality control purposes. However, more complex tests that may tend to represent an aspect (or aspects) of service conditions are generally devised in different ways by different laboratories, at least in their early stages of development.
In this chapter it is argued that although this was initially the case with low-cycle fatigue (LCF) testing at high temperatures, the subject has now developed to the point that standard test procedures are required. These would facilitate comparison of data and the assessment of methods for life prediction, reduce duplication of testing and generally assist our understanding of the processes of deformation and damage under cyclic conditions. The interdependence of increased knowledge of LCF phenomena and the improvement of test methods is stressed, and the principal factors affecting reliability of results are identified.
The importance of specimen shape and dimensions and the associated choice of the method of strain measurement are discussed with reference to the relative advantages and limitations of the main types currently in use. Other factors considered include the effect of surface finish, axtiality of loading, waveform, strain rate and, of particular importance, the need for a standard definition of failure. The problems of defining and measuring one of the fundamental parameters, i. e. plastic strain in situations where stress-strain hysteresis loops do not show the theoretically ideal shape, are considered and possible solutions are suggested. The lack of sufficient systematic information to enable quantification of the effects of variations in procedures is noted.
The present situation with respect to activities aimed at producing LCF testing standards is summarised. It is recognised that not all LCF test programmes can be, or necessarily should be, carried out solely according to a standard method; however, it is concluded that the development of a standard procedure is feasible and that the potential benefits are significant.
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© 1987 Elsevier Applied Science Publishers Ltd
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Thomas, G.B. (1987). The Case for Standards in High Temperature Fatigue. In: Skelton, R.P. (eds) High Temperature Fatigue. Springer, Dordrecht. https://doi.org/10.1007/978-94-009-3453-5_6
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DOI: https://doi.org/10.1007/978-94-009-3453-5_6
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