Application of Barkhausen noise in creep and fatigue damage assessment

Majority of thermal power plant components undergo damages due to fatigue, creep, or combined fatigue-creep effects during service. These damages invo lve changes in residual stress and microstructure, whose presence is known to influence the Barkhausen Noise amplitude in ferro-magnetic materials. Pr esent investigation aims at applying Barkhausen Noise (BN) to assess these damages. Methods for fatigue damage assessment in steam turbine rotor, casi ng and boiler water feed pump shaft steels through residual stress measurem ents using BN have been established. Attempts were made to correlate the ma gnetic parameter (MP) values with respective rupture lives in some of the c reep resistant steels subjected to different aging times. Correlations betw een MP ratio (MP/MP0) and creep strain were established for rotor steel. Re sults obtained in this investigation have indicated the possibility of empl oying the Barkhausen noise for assessing fatigue/creep damage in thermal po wer plant materials.