Failure load study of 18 percent Ni Maraging steel 250 (M250) using Acoustic emission parameters

Acoustic emission (AE) evaluation is global NDT technique in which acoustic emissions takes place by loading the component at a specified threshold level. In this study, a crack propagation is studied by AE parameters.Specimens are tensile deformed and AE parameters are recorded. Three types of specimens, Type A, Type B and Type C, are designated as Heat affected zone, Parent metal and Weldment, respectively. The recorded data are analysed in three zones, Zone-1, Zone-2 and Zone-3, in terms of passive, active and critically active of a crack, respectively. Zone-1 is equivalent to the data arrangement up to 60% of Failure Load (FL), Zone-2 equates to 75% - 90% of F.L. and Zone-3 corresponds to fast-fracture region and equates to 90%-F.L. AE parameters - Amplitude, Ring down counts, Duration, Rise Time, Energy, RA Value, DA Value, Hit Rate, Count Rate and Energy Rate are tabulated for various failure loads. These parameters have vital importance in critical assessment of dynamic nature of cracks in Maraging steel. The scatter plots as qualitative indicators, and the rate graphs are used for understanding crack propagation. An abort criterion is developed by using combination of parameters that will serve as an early warning tool.