Abstract
The safety of structures and mechanical instruments can be evaluated quantitatively by monitoring the damage level of the composition elements. In this study, we propose the oscillation circuit method for measuring local strain in the elements. The fatigue tests of the specimen with a center hole are carried out under tension-compression axial loading, and the change of local strain is measured by using the oscillation circuit method and the usual instrument. The results are summarized as follows; (1) when the frequency of cyclic load is low, the strain measured by the oscillation circuit method agrees well with that by the usual measurement. (2) the crack initiation and propagation can be monitored based on the mean value of sampling time of stain measured by the oscillation circuit method.
