## 4 Discussion  
A two-variable selection function model and breakage function model were given in Equations (10) to (12) with \(t\) as parameter, and constants can be fitted to the experimental data. In order to investigate the effect of compression ratio and size distribution index on the change of the rock size in size reduction process, numerical calculation analysis of the selection function model and breakage function model are implemented. In Figure 5, it is obvious that the curvature of the selection function decreases with increase of size distribution index. This means that the particle size is of more uneven distribution with an increase of size distribution index, which will result in a coarse particle not easily broken due to the protection of the tiny particle in the breakage of rock. In Figure 6, a curve denotes the weight percentage of undersized particles passing a certain particle size, which corresponds to representation of parameters in the breakage function and how they are affected by the compression ratio. The size reduction of particles is greatly improved when compression ratio is larger. Typical results from fitting curves of the test data in 45 h are presented in Figures 7 and 8, which demonstrate the size distribution curve and flakiness index curve movement over time, and cone crusher performance changes over time. It should be noted that a change moves the size distribution curves along the vertical, while a change moves the flakiness index curve along the horizontal axis, as shown in Figures 7 and 8. The prediction data of product size distribution are obtained by Equations (7) to (14), and the measured data are obtained from field test, as shown in Table 2.  
The measured data of flakiness index are obtained by Equations (7) to (14), and the measured data are obtained from field test, as shown in Table 3.  
Tables 2 and 3 summarize the results from the tests and compute at 45 h under normal feed conditions. They show the comparison between computed results of product size distribution and \begin{table}
\begin{tabular}{c c c c c c} \hline \multirow{2}{*}{**Size (mm)**} & \multirow{2}{*}{**Measured (\%)**} & \multicolumn{2}{c}{**Considering Liner Wear**} & \multicolumn{2}{c}{**Without Considering Liner Wear**} \\ \cline{3-6}  & & **Predicted (\%)** & **Error (\%)** & **Predicted (\%)** & **Error (\%)** \\ \hline +37.5 & 88.2 & 86.4 & 2.0 & 90.8 & \(-\)3.0 \\ +31.5\(-\)37.5 & 65.5 & 65.1 & 0.6 & 71.6 & \(-\)9.3 \\ \(-\)26.5\(+\)31.5 & 49.0 & 49.8 & \(-\)1.6 & 57.1 & \(-\)16.5 \\ +19\(-\)26.5 & 28.5 & 30.8 & \(-\)8.1 & 38.0 & \(-\)33.3 \\ +16\(-\)19 & 21.6 & 24.6 & \(-\)13.9 & 31.3 & \(-\)44.9 \\ +9.5\(-\)16 & 9.6 & 10.8 & \(-\)12.5 & 14.1 & \(-\)46.9 \\ \hline \end{tabular}
\end{table} 
Table 2: Comparison between measured and predicted results of the particle size distribution (PSD). Figure 8: Worn liner causes the flakiness curve to change over time. \begin{table}
\begin{tabular}{c c c c c c} \hline \multirow{2}{*}{**Size (mm)**} & \multirow{2}{*}{**Measured (\%)**} & \multicolumn{2}{c}{**Considering Liner Wear**} & \multicolumn{2}{c}{**Without Considering Liner Wear**} \\ \cline{3-6}  & & **Predicted (\%)** & **Error (\%)** & **Predicted (\%)** & **Error (\%)** \\ \hline +31.5 & 19.5 & 19.9 & \(-\)2.1 & 23.9 & \(-\)22.6 \\ +26.5\(-\)31.5 & 20.4 & 19.1 & 6.4 & 18.8 & 7.8 \\ +19.0\(-\)26.5 & 31.4 & 28.7 & 8.6 & 24.7 & 21.3 \\ +16.0\(-\)19 & 39.2 & 36.3 & 7.4 & 31.6 & 1 flakiness index considering liner wear and those without considering liner wear. The errors could be calculated to analyze the accuracy of the results. By analyzing the measured and predicted results of size distribution and flakiness index, the errors in the predicted values can be calculated, as illustrated in Tables 2 and 3. Table 2 summarizes the results from the tests and predicted values of the PSD. It shows that the absolute values of errors in predicted values of the PSD without considering liner wear are less than 46.9% and those considering liner wear are less than 13.9%, with respect to the test values.