PSI - Issue 65

A.V. Byzov et al. / Procedia Structural Integrity 65 (2024) 48–55 A.V. Byzov, A.E. Konygin, D.G. Ksenofontov, O.N. Vasilenko / Structural Integrity Procedia 00 (2024) 000–000

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3.2. Drawing the hardness profile

Based on the regression equations determined here in Section 3.1 for all frequencies, the hardness profiles in each modelled product are calculated. The calculation results are presented in Figure 3. Judging by the data, the calculated and real hardness profiles of surface-hardened products have a similar change in depth. The real hardness profile has a sharp transition due to the fact that the hardened layer was simulated by volume hardened plates, whereas the hardness profile reconstructed on the basis of eddy current measurements changes smoothly from the high hardness area to the core hardness area. Therefore, it is reasonable to state that the considered technique is suitable for determining the hardness profile of surface-hardened flat products and that it can be used in scientific research and in production. The incomplete coincidence of dependences can be explained by a relatively small set of samples. In this connection, the equations obtained in Section 3.1 may not fully correspond to the regression equations that could be obtained in the case of a larger set of samples simulating the hardened layer. Note that in such measurements it is necessary to know precisely the relative magnetic permeability and specific electrical conductivity of the material from which the hardened product layer is composed since they are the basis for calculating the frequencies of the excitation current in the excitation coil at which the testing is performed, this being extremely important for the accuracy of the measurements made.

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Fig.3 – The reconstructed hardness profiles of the surface-hardened samples: d = 1.67 mm (a); d = 2.67 mm (b); d = 3.51 mm (c); d = 4.36 mm (d) (● – real profile; ■ – calculated profile)

4. Conclusion

The methodology presented in the literature for reconstructing the hardness profile of cylindrical surface hardened products using a through-flow eddy current transducer is also applicable to reconstructing the hardness profile of flat surface-hardened products using a surface eddy current transducer. The study has resulted in the reconstruction of the hardness profiles for all the available samples. The calculated and real hardness profiles have a similar behavior; therefore, the considered methodology is suitable for the