# Energy Balance of the Dynamic Impact Stressing of Conveyor Belts
## 3 Results and Discussion
### A Comparison of the Calculated Energies for the Impactors Used  
Histograms of the correlations between the impact energy and the impact height were created for the individual values of the impact energy, the impactor types used, and the individual hammer masses (Figures 6 and 7). A comparison of the impact energy values clearly indicated that higher values were reached in the tests with the pyramidal impactor. This type of impactor causes significant damage to the structural components of rubber-textile conveyor belts, and with this type of impactor, punctures occurred at lower impact heights than those with the spherical impactor [28]. The shape of the pyramidal impactor simulates sharp-edged materials that cause punctures to the rubber cover layer. This usually leads to damage caused by thet tribological interactions between the transported material and the conveyor belt. Moreover, such interactions cause evident abrasive wear of the belts. A spherical impactor simulates a more favourable shape of the transported material, and unlike a pyramidal shape, it does not concentrate the damage within a small volume. With both impactor types used, the impact energies increased with the increasing impact heights and hammer masses. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & & & \multicolumn{4}{c}{**E\({}_{\text{Pz}}\) [J]**} \\ \hline
**h [m]** & **50 kg** & **60 kg** & **70 kg** & **80 kg** & **90 kg** & **100 kg** \\ \hline
0.2 & 12.8 & 25.9 & 33.0 & 39.2 & 48.6 & 62.8 \\
0.4 & 28.4 & 49.4 & 65.9 & 81.6 & 107.7 & 123.6 \\
0.6 & 41.2 & 71.8 & 101.6 & 128.7 & 160.7 & 190.3 \\
0.8 & 70.1 & 104.8 & 139.4 & 180.5 & 223.4 & 257.0 \\
1 & 82.9 & 168.3 & 180.6 & 211.9 & 276.3 & 276.6 \\
1.2 & 112.8 & 193.6 & 225.2 & 224.5 & 302.0 & 344.3 \\
1.4 & 142.2 & 238.4 & 254.1 & 267.6 & 326.7 & 394.4 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Values of residual positional energy E\({}_{\text{Pz}}\) for individual tests with the pyramidal impactor. Figure 6: Impact energy E\({}_{\text{Pr}}\) of the hammer as a function of the impact height h, with the spherical impactor (for various masses in kg). Figure 7: Impact energy E\({}_{\text{Pr}}\) of the hammer as a function of the impact height h, with the pyramidal impactor (for various masses in kg). A better comparison is presented in the form of a curve of the correlation between the impact energy and the hammer impact height (Figure 8). It clearly shows that the impact energies of the hammer with the pyramidal impactor were higher than those observed with the spherical impactor while this difference increased with the growing impact height. The graph below (Figure 9) represents the curve of a correlation between the bounce height and the impact height for the pyramidal impactor. It is evident that as the impact height increased, the height to which the hammer bounced off the stretched belt increased too. The maximum bounce heights were observed with the hammer mass of 100 kg because, in this case, the unconsumed portion of the total potential energy reached its peak. Figure 10 shows the same comparison, i.e., a correlation between the impact height and the bounce height, but for the spherical impactor. The bounce heights increased more evenly with the increasing impact heights. Again, the maximum values were observed in the experiments with the hammer weighing 100 kg, i.e., the maximum mass value. Figure 8: A comparison of the correlation between the impact energy \(\mathrm{E_{Pr}}\) and the impact height h for the impactor types used. Figure 9: The correlation between the bounce height \(\mathrm{h_{z}}\) and the impact height h for the pyramidal impactor. The unconsumed portions of the total potential energy, i.e., residual positional energy \(\mathrm{E_{Pr}}\), were graphically presented as a function of the hammer mass for the impactor types used (Figure 11). The graph indicates that with an increasing mass, the residual energy increases too; this corresponds to increases in the bounce height.