• Vippola, Minnamari
• Santa-Aho, Suvi Tuulikki
• Sorsa, Aki
• Lundin, Per
• Tomkowski, Robert

Abstract

The Barkhausen Noise Testing (BNT) is a non-<br/>destructive method for investigation many of <br/>ferromagnetic material features. The most common <br/>application is monitoring of so-called grinding burns <br/>caused by introducing locally high temperature while <br/>grinding. Other features, such as microstructure, residual <br/>stress changes, hardening depth, etc., can be monitored as <br/>well. Nevertheless, because the BNT is a method based on <br/>a complex magneto-electric phenomenon which still <br/>needs more scientific investigations an understanding, it is <br/>not standardized yet. Therefore, there is a need for <br/>studying of traceability and stability of the measurement <br/>method. The aim of this study was to carry out statistical <br/>analysis of the ferromagnetic samples after grinding <br/>processes by the use of BNT. The first part of the <br/>experiment was to grind samples in different facilities <br/>(Sweden and Finland) with similar grinding parameters, <br/>different grinding wheels, and different hardness. The <br/>second part was to evaluate measured BNT parameters in <br/>order to determine significant factors affecting BNT signal <br/>value.The measurement data from the samples were divided <br/>into two different batches according where they were <br/>manufactured. Both grinding batches contained <br/>measurement data from three different appraisers. The <br/>main feature for calculation was the RMS value from the <br/>Microscan direct results. The first processing step was to <br/>normalize the RMS values for all the measurements. The <br/>standard analysis of variance (ANOVA) was applied for <br/>the normalized dataset. The ANOVA analysis showed that <br/>a significant impact on the BNT signal value has grinding <br/>parameters, while the other investigated factors (e.g. <br/>measurer) are negligible. The reasons of that are discussed <br/>at the end of the paper.

Topics

• impedance spectroscopy
• microstructure
• experiment
• grinding
• hardness