COMPARISON BETWEEN CREEP FAILURE ANALYSIS AND MAGNETIC BARKAHUSEN NOISE RESULTS
The Barkhausen effect is a name given to the noise in the magnetic output of a ferromagnet when the magnetizing force applied to it is changed. Discovered by German physicist Heinrich Barkhausen in 1919, it is caused by rapid changes of size of magnetic domains (similarly magnetically oriented atoms in ferromagnetic materials).
On this work authors have compared the results obtained after a conventional creep failure analysis and magnetic Barkhausen noise. They chose one region without creep damage that was named as standard. Two other regions with creep damage were named as T1 and T2. The sample T1 after optical metallographic analysis has presented level A and B of creep damage according the method of Neubauer to estimate the rest life of creeping by replicas. The sample T2 after optical metallographic analysis has presented level C and D of creep damage according the same method. Based on the failure analysis, they evaluated MBR analysis and compared the results.
Creep damage is the root causes of many failure equipments on heavy industries that work at non conventional temperature, specially boilers and furnaces. It's very difficult detect regions with creep damage by others conventional NDT methods. Replicas are the most used NDT technique to detect creep damage but this technique is based on result of discrete point; may not cover the entire surface of tubes. The electromagnetic techniques are sensible to micro structural change that modifies the magnetic permeability of the material. The authors have emphasized these promising techniques - remote field and magnetic Barkausen noise. The details of the write-up may be downloaded clicking the blue rectangle below;