Abstract
Five laboratories undertook a study to assess interlaoratory variability and bias in strain-cycle fatigue testing of 1.2-mm-thick sheet specimens. In addition, one laboratory evaluated the effects of specimen geometry, actuator restraint, extensometer mounting surface, etc., on validity and bias of cyclic stress-strain and strain-life data. The results show that the cyclic stress-strain curve is sensitive to the effects of interlaboratory differences. The strain-life curve is also affected by results from different laboratories, but in addition it is sensitive to testing variables such as extensometer mounting surface, failure criterion, specimen, geometry, etc. The results of this study have implications for the development of a test method and for the use of strain-cycle fatigue data obtained from thin sheet specimens. The results reported here form a basis for expanding ASTM Recommended Practice for Constant-Amplitude Low-Cycle Fatigue Testing (E 606) to include materials with thicknesses less than 2.5 mm.
