Evaluation of a New Barkhausen Noise Sensor

In this thesis, it is investigated if the Barkhausen noise can be detected in a rotating environment using a new, passive sensor design. The sensor relies on the relative movement between the measured material and the sensor to function. The idea behind the thesis is to investigate if this sensor can detect changes in the Barkhausen noise measured on a ferromagnetic material as it is being subjected to stress until the point of breakage, and if this change can be related to fatigue in the material. If this is the case, the sensor-technology could be valuable for e.g. condition monitoring purposes.The work was focused on improving the design of an existing sensor, to build an accompanying measurement system - composed of the sensor, an amplifier, a data acquisition box and a computer - and to provide a proof of concept that the sensor can detect the Barkhausen noise. The sensor in its most basic form consist of a solenoid coil, with or without a core, and a permanent magnet. A number of different sensor versions were made and tested, to investigate the effects of the following parameters: the thread size in the coil, the core material, and the number of magnets and their orientation. To test the functionality of the sensor design, a rotating bending test rig (RotaBend by Sincotec) was used. This machine also allow to expose the specimen to stress, to investigate if a change related to fatigue can be detected. MATLAB were used as an interface to the data acquisition box, to acquire and analyse data from the measurements using the sensor. The analysis were performed by calculating the RMS-voltage and the Fourier transform of the data. The thesis shows that the sensor can detect the Barkhausen noise in a rotating element. The limited amount of tests also indicates that it is possible to detect a change in the Barkhausen noise RMS-value as the material of the specimen is fatigued. It has not yet been proven if or how this change can be related to fatigue in the material. The tests also indicates that there is no change in the frequency content of the Barkhausen noise as the material of the specimen is fatigued. Left for further investigation is at what depth in the material the Barkhausen noise is induced.Validerat; 20150310 (global_studentproject_submitter