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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2. Methods and materials

2.1. Samples In this study, an annealed steel 3 specimen with dimensions of 23.3×34.5×97 mm and hardness assumed to be 20 HRC is used as the core of the modelled surface-hardened product. Different depths of the hardened layer are simulated by using 60C2A steel plates of different thicknesses quenched in oil from a temperature of 870 �. The thickness of these plates, the hardness measured on the Rockwell scale, and the initial relative magnetic permeability µ n are listed in Table 1. The parameter µ n was calculated as the slope of the initial section of the magnetization curve, which was measured by means of a permeameter in a Remagraph C-500 device. Table 2 shows the chemical composition of this steel grade.

Table 1 – The geometric and physical properties of 60C2A plates

Depth d , mm Hardness, HRC µ in , arb. unit 1.65 63.4 60.3 2,67 62.9 55.9 3.51 62.5 58.7

For further calculations, we assume that µ in is equal to 60 and that electrical conductivity σ is equal to 1.9 10 6 S/m.

Table 2 – The chemical composition of the 60C2A steel C, % Si, % Mn, % Ni, % S, %

P, %

Cr, % Cu, %

Fe

0.57-0.65 1.5-2 0.6-0.9 ≤ 0.25 ≤ 0.035 ≤ 0.035 ≤ 0.3

≤ 0.2

~96

2.2. Experimental setup

Figure 1 shows a schematic diagram of the experimental setup by means of which the measurements were carried out. The transformer eddy current probe, designed to excite eddy currents in the TO and to convert the electromagnetic field of the TO into a signal of the probe itself, consists of excitation and measuring coils, as well as a resistor to measure the current in the excitation coil circuit. The figure also shows a G3-109 low-frequency signal generator serving as a source of a sinusoidal signal fed to the excitation coil of the ECP. An F2-16 phase difference meter (PDM) served to measure the phase difference between the current in the excitation coil circuit and ε in the measuring coil circuit. With the help of a V7-40/1 voltmeter (V), the effective value of voltage across the measuring coil was determined. An AKIP-4115/1A oscilloscope (O-scope) was used to control the frequency of the generator signal and the voltage value across the resistor in the measuring coil circuit. In this case, the constancy of the current amplitude value across the measuring coil was ensured and therefore the constancy of the primary magnetic field value of the eddy current probe.

Fig 1 – Schematic diagram of the experimental setup