## 3 Results
The stress-strain state of the metal at the crack tip will in any case be more complex and inhomogeneous for a thick specimen [28]--the state of the metal and the size of the plastic deformation zone on the surface and inside the specimen differ. Therefore, at any stage of the specimen test, \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{2}{c}{**Specimen Thickness**} & \multicolumn{2}{c}{**1 mm**} & \multicolumn{2}{c}{**6 mm**} \\ \hline \multicolumn{2}{c}{**Parameter**} & \multicolumn{2}{c}{**Amplitude \(u_{m}\)**} & \multicolumn{2}{c}{**AE Hits Rate**} & \multicolumn{2}{c}{**Amplitude \(u_{m}\)**} & \multicolumn{2}{c}{**AE Hits Rate**} \\ \multicolumn{2}{c}{} & \multicolumn{2}{c}{**dB**} & \multicolumn{2}{c}{\(\dot{N}\)**, Hits/s**} & \multicolumn{2}{c}{**dB**} & \multicolumn{2}{c}{\(\dot{N}\)**, Hits/s**} \\ \hline \multicolumn{2}{c}{\(l\approx 1.7\) mm (visible} & & & & \\ crack appearance) & 68 & 2 & 100 & 26 \\ Crack length & \(l\approx 4.4\) mm (crack propagation) & 89 & 6 & 92 & 10 \\ \multicolumn{2}{c}{\(l\approx 7\)–\(8\) mm (acoustic gap)} & 65 & 3 & 70 & 6 \\ \multicolumn{2}{c}{\(l\approx 9\)–\(10\) mm (before failure)} & 82 & 27 & 100 & 38 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Comparison of the amplitudes and AE hits rate at different stages of tension tests of specimens from \(30\) KhGSA steel with a thickness of \(1\) mm and \(6\) mm. from the initiation of a crack to complete failure, the metal of a thick sample has higher strain intensities, and, accordingly, is more acoustically active. To assess the degree of danger of AE sources, criterion parameters are used, the calculation of which is carried out according to the values of amplitude, duration, activity, etc. One of the most common criteria is the \"_b-value_\" parameter. The calculation of the \"_b-value_\" parameter is carried out according to the results of the approximation of the amplitude distribution by the linear function \(lg(N)=a-b\cdot A_{dB}\)[29]. The calculation of the \"_b-value_\" parameter was carried out using a rolling window with a size of \(W=75\) signals at a scanning step of 15 pulses. The amplitude distribution was constructed in the range of values \(A_{dB}=\)[30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100] dB. The results of calculating of \"_b-value_\" are shown in Figure 7.  
As shown in Figure 7a, for the sample of 1 mm thick, the maximum value of the parameter reached \(b=2.648\), and its scattering \(\Delta b\) during the loading time was 0.552. For a sample of 6 mm thick (Figure 7b), there is an increase in the scatter of the \(b\)-_values_ (\(\Delta b=0.932\)). The definition of the damage stage, according to data shown in Figure 7, seems to be difficult. However, it should be noted that an increase in the specimen leads to an increase in the scatter of the \"_b-value_\" during the loading process. To assess the influence of the scale factor on the acoustic signal parameters generated during the crack development in the test object, it is necessary to take into account changes not only in absolute values, but also in the type of distribution functions of AE data. According to [30, 31], the processes of damage accumulation at the micro-, meso-, and macroscale levels of structural materials destruction are characterized by the unique ranges of energy (\(E\)) and mean count frequency of AE signals (\(N_{p}/\tau_{p}\)), where \(N_{p}\) is hits number and \(\tau_{p}\) is pulse duration. When the scale level of destruction is changed, the nature of damage accumulation in the material also changes. It manifests in a change in the frequency characteristics of the recorded AE signals. Therefore, for specimens of different thicknesses, the empirical distribution functions of the mean count frequency of AE signals (\(N_{p}/\tau_{p}\)), should be different.