OBRABOTKAMETALLOV Vol. 23 No. 3 2021 MATERIAL SCIENCE EQUIPMENT. INSTRUMENTS 7 5 Ta b l e 2 The reliability of the correspondence of the observed grain length distribution to the theoretical one according to Pearson’s chi-squared test χ² Grinding method Fraction Lognormal Gamma distribution Length maximum value 2 obs χ 2 crit χ 2 obs χ 2 crit χ 2 obs χ 2 crit χ Roller-press 1 53.5 11.1 5.8 11.1 16.7 16.9 2 37.4 11.1 5.5 9.5 1.7 11.1 3 36.9 11.1 11.1 18.3 8.9 12.6 4 54.7 11.1 8.0 18.3 9.3 11.1 5 18.2 9.5 8.5 11.1 3.8 12.6 Rotary 1 7.9 9.5 3.5 9.5 14.4 11.1 2 7.4 9.5 11.1 9.5 9.3 11.1 3 15.1 9.5 6.4 18.3 8.6 11.1 4 6.2 9.5 8.2 9.5 11.8 14.1 5 6.6 9.5 8.2 18.3 9.1 11.1 Reliability, % 40 90 90 Ta b l e 3 Reliability of the correspondence of the observed distributions of grain width and shape factor according to Pearson’s test Method Fraction Width Shape coefficient Normal Log-normal Maximum value 2 obs χ 2 crit χ 2 obs χ 2 crit χ 2 obs χ 2 crit χ Roller-press 1 5.8 5.8 34.0 7.8 6.0 11.1 2 5.5 5.5 68.9 11.1 7.6 7.8 3 11.1 11.1 40.1 7.8 3.1 7.8 4 8.0 8.0 54.6 11.1 9.4 11.1 5 8.5 8.5 66.9 14.1 8.3 11.1 Rotor 1 3.5 3.5 30.2 12.6 4.6 12.6 2 11.1 11.1 52.4 12.6 11.3 12.6 3 6.4 6.4 30.4 9.5 5.4 12.6 4 8.2 8.2 29.9 9.5 4.3 9.5 5 8.2 8.2 62.5 12.6 3.3 9.5 Reliability. % 100 0 100 Fig. 4. Spearman’s rank correlation coefficient ρ between geometric parameters of grains in different fractions: – roller-press grinding; – rotary grinding
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