OBRABOTKAMETALLOV MATERIAL SCIENCE Том 23 № 3 2021 EQUIPMEN . INSTRUM TS Vol. 7 No. 3 2025 A quantitative evaluation of the content of needle-shaped and isometric grains obtained by roller-press and rotary grinding is presented in fig. 7. Following roller-press grinding, the content of needle-shaped grains (l/b > 2) in the five fractions ranges from 2.8 % to 5.2 %, while following rotary grinding, it ranges from 0.9 % to 1.9 %. On average, the number of needle-shaped grains in the five-fraction samples is reduced threefold after rotary grinding compared to roller-press grinding. a b Fig. 6. Dependence of the aspect ratio l/b on grain width b for five fractions after roller-press (a) and rotary (b) grinding a b Fig. 7. Content of needlelike (a) and isometric (b) grains after roller-press (1) and rotary (2) grinding, depending on the average cell size of the upper and lower sieves of the Wm fraction The proportion of isometric grains (l/b ≤ 1.3) after both roller-press and rotary grinding ranges from 33 % to 46 % (fig. 7). Rotary grinding yields the highest proportion of isometric grains, ranging from 40 % to 46 %. Following roller-press grinding, the proportion of isometric grains ranges from 33 % to 41 %. The average proportion of isometric grains is approximately 42 % after rotary grinding and 37 % after rollerpress grinding, representing a 5 % decrease. Conclusions 1. The grain shape factor distributions after roller-press and rotary grinding adhere to the law of maximum value. The geometric parameters used to calculate the shape factor follow these distribution models: grain length – the law of maximum value, grain width – the normal distribution. 2. Given that, of the three geometric parameters analyzed, only grain width follows the normal distribution, it is impossible to meet a prerequisite for using the Pearson correlation coefficient: the analyzed datasets of geometric parameters must conform to a normal distribution. Consequently, Spearman’s rank criterion was employed to assess the relationship strength.
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