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

53

6

   

   

U refl 

U k

Im

sin

sin 0 

 

   

.

(6)

k

U U

0

0

2.3.3. Drawing the hardness profile of a surface-hardened product On the basis of eddy current measurements, the ε dependence of the measured hardness at a certain depth, for which the frequencies were calculated, is plotted. A linear regression equation between these parameters is determined. After that, by the linear regression equations for each specific depth, the hardness is calculated using the modulus of ε rel of the eddy current probe. Thus, a data array of calculated hardnesses and their corresponding depths are obtained. Based on this array, the hardness–depth dependence is plotted, so that the hardness profile of the surface-hardened product is reconstructed as a result of eddy current measurements. 3.1. Drawing the ε rel -dependence of hardness As a result of measuring the voltage across the measuring coil and the phase difference between the current strength across the excitation coil and the voltage across the measuring coil, the dependences of layer hardness HRC on the calculated parameter e for specific frequencies are plotted. A regression equation is also determined for each case from the available data set. Figure 2 shows examples of such dependences for frequencies of 181.4, 355.5, and 2222 Hz. 3. Results and Discussion

70

а

b

60

60

50

50

40

40

30 HRC

HRC

30

H = 3110.3· e rel -2189.4

H = 3798.1· e rel -2527.9

20

20

0.71

0.72

0.73

0.67

0.68

0.69

e rel , arb. unit

|U вн /U 0 |, arb.unit

c

63.4

63.2

63.0

62.8

HRC

62.6

H = 333.7· e rel -134.4

62.4

0.590

0.591

0.592

0.593

e rel , arb.unit

Fig. 2 – The ε rel -dependence of layer hardness: 181 Hz (a); 355.5 Hz (b); 2222 Hz (c)