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Development of Subscale Tester for High-Cycle Fatigue Evaluation
This report documents the development and technical validation of a subscale high-cycle fatigue tester as a materials characterization tool useful for generating Whler (stress-life; S-N) diagrams. The instrument operates under constant amplitude (displacement) loading and subjects flat-sheet specimens with modified Krouse-type geometry to fixed cantilever bending mode with a stress ratio between -1 (fully reversed) and 0 (pulsating tension). A LabVIEW program provides a user interface that displays a direct read-out of the number of cycles and saves a record of the data to a comma-separated-value file for further processing. Here we report the setup and operation of the instrument as well as details regarding specimen design and preparation. In particular, we investigate aluminum alloy 6061-T6 under fully reversed bending conditions and a 25-Hz frequency. Tests are carried out with guidance from ASTM standards B593 and E739. Corroborated by comparisons with literature data, the system can be used for effective implementation for at least aluminum alloys, although other classes of materials should be validated for as well (e.g., steels, to improve instrument robustness and versatility). Subscale fatigue testing is beneficial for limited material volumes, particularly under circumstances of high specimen preparation costs in the conventional, full-scale counterpart.
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