No abstract

Nondestructive positron-lifetime measurements have been performed during stress-controlled symmetric fatigue of austenitic stainless steel up to failure for different applied stress amplitudes between 230 and 300 MPa. For this purpose a fatigue machine has been equipped with a mobile positron beam emitted from a 22 μCi (0.8 MBq) Se/7272As generator. A pronounced increase of the mean positron lifetime has been found within the first 10% of fatigue life. Saturation has been reached after 40% of fatigue life. The mean positron lifetime at failure depends strongly on the applied stress amplitude.