**Maciej Roskosz 1,\*, Krzysztof Fryczowski <sup>2</sup> and Krzysztof Schabowicz <sup>3</sup>**


Received: 6 April 2020; Accepted: 27 April 2020; Published: 29 April 2020

**Abstract:** Measurements are carried out of the Barkhausen noise (BN) and hardness on specimens where changes in hardness were obtained due to strain hardening (S235 and DC01 steels) and due to thermochemical treatment (AMS 6414 steel). A method is presented of processing the recorded BN signal to extract diagnostic information. The BN number of events is selected as the signal characteristic property to develop relevant correlations. A new methodology is presented for the development of correlations between the Barkhausen noise number of events and hardness. A possibility is indicated of developing correlations with a high R2 determination coefficient. The method limitations are specified.

**Keywords:** hardness; Barkhausen noise; number of events; non-destructive testing inverse problem
