Abstract: This paper inquires into the exportability of the fatigue measurements made on standard test-specimen to wire electro- discharge machined flexures with thin cross sections (50 $mu@m). It describes the results of a set of fatigue measurements made on 66 circular flexible hinges machined in steel and bronze by wire electro-discharge machining. After reminding the fatigue theory and describing the theoretical model used to calculate the stresses inside the bent hinges, the paper describes the experimental setup and the measured results. The main conclusions drawn out of this work is that the admissible stresses for the tested flexures having a low surface roughness (Ra $EQ 0.2 $mu@m) are at least as high as the admissible stresses for standard test specimens. This indicates that fatigue data found in literature can be used to calculate the dimensions of this kind of flexures without any reduction of the safety factor.!8
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