Fatigue monitoring by NDT of austenitic stainless steel at ambient temperature and 300°C and new attempts to monitor a fracture mechanics test

NDT on-line monitoring methodology was applied at the servo-hydraulic machine to monitor the propagation behavior of ultrasonic waves during LCF-tests. Coupling-free excitation and receiving of the waves by use of EMAT were applied. A high potential to early characterize fatigue before the end-of-life was documented. So far at ambient temperature a phase transformation to -martensite is observed micro-magnetic NDT is also appropriate. Destructive SE(B) Single Edge Bending Tests were online monitored to study NDT methodology to in-situ and on-line determine crack initiation and growth during the experiment. Time of flight of an EMAT-excited ultrasonic surface wave which travels around the crack shows a linear correlation to crack growth and by a Giant Magneto-Resistor-Line-Array the magnetic leakage flux of the crack is observed.