The conventional measurement of mechanical hardness, for instance, in steel, is usually carried out using the same principle. A mechanical indenter is forced towards the surface of the workpiece, penetrating it and leaving an imprint. This imprint is measured using optical microscopy and a hardness value is determined considering the relationship between the geometry of the indenter, the applied force, the holding time and the geometry of the imprint. Depending on the size of the indenter and the force applied, a distinction is made between micro or macro hardness. In some cases, the workpieces must be pre-treated (e.g. by polishing) prior to hardness measurement. Conventional hardness measurement is difficult to integrate into production lines as the process itself is time consuming. Furthermore, traditional measurement of hardness is destructive, rendering the workpieces tested useless.
The situation is different with the use of magnetic methods. The Barkhausen noise analysis, also known as the micromagnetic method, is at the forefront of nondestructive hardness measurement techniques. The probe consists of an electromagnet which generates an alternating magnetic field. Simultaneously, it records the interaction of the generated magnetic field with the ferromagnetic material. This interaction generates an inductive current, whose strength depends on the hardness of the material. Soft materials generate intensive high amplitude signals whereas hard materials generate signals with low amplitudes. The micromagnetic method has