Results of an Interlaboratory Fatigue Test Program Conducted on Alloy 800H at Room and Elevated Temperatures

A number of difficulties were encountered in early low cycle fatigue tests conducted at General Atomic Company (GAC). The experimental approach adopted for this work involved the use of electro-hydraulic test systems, hour-glass geometry specimens, diametral extensometers, and axial strain computers. Attempts to identify possible problem areas with this approach were complicated by the lack of reliable data for the particular heat of Alloy 800H under investigation. The method adopted to resolve this difficulty was to generate definitive test data in an Interlaboratory Fatigue Test Program. The laboratories participating in the program were Argonne National Laboratory, Battelle Columbus, Mar-Test, and NASA-Lewis. Fatigue tests were conducted on both solid and tubular specimens at temperatures of 20, 593, and 760°C and at strain ranges of 2.0, 1.0, and 0.5%. It was concluded that the subject test method can, under certain circumstances, produce fatigue data which are seriously in error. As a result, this approach subsequently was abandoned at GAC in favor of parallel gage length specimens and axial extensometers.