ドップラー幅広がり測定を用いた陽電子消滅法によるSUS316鋼の非破壊的疲労評価

Abstract

Aiming at non-destructive evaluation of fatigue stored in type 316 stainless steel which is mostly used in the primary water line of pressurized water reactor (PWR), we tried to apply positron annihilation lineshape analysis to fatigue damage. By making use of 68Ge as a positron source, an energy spread of annihilation gamma ray peak from stainless steel specimens was measured. We prepared stress controlled fatigue specimens and strain controlled fatigue specimens, and then we investigated the relation between fatigue life and a non-destructive parameter of lineshape analysis defined as S-parameter and compared the microstructure of the fatigue specimens with the S-parameter. As a result, it is seen that there exists a good correlation between the S-parameter and the fatigue life; the S-parameter increases with dislocation density monotonically. The relation between the S-parameter and the fatigue life in the stress controlled fatigue is different from that in strain controlled fatigue. The S-parameter in the latter increases faster in early stage than that in the former. In the case of stress controlled fatigue, the change in the S-parameter does not depend on stress amplitude in the range from 200 to 250 MPa. In the case of strain controlled fatigue, the change in the S-parameter does not depend on strain amplitude in the range from 0.25 to 0.31%. Finally we succeeded in demonstrating systematic data to evaluate the fatigue damage in type 316 stainless steel.