Given the high share of energy consumption in the comminution stage an‎d the importance of its optimization in mineral processing, the effect of loading rate on the fracture mechanism of sulfide copper ore was investigated. The main objective was to find conditions under which fracture can be controlled so that the liberation of valuable minerals is maximized while energy loss is minimized. To achieve this goal, rock mechanics tests were performed on disk-shaped an‎d SCB specimens of sulfide copper ore. These specimens were subjected to four loading rates, ranging from quasi-static to dynamic, using appropriate loading devices. Data were recorded an‎d analyzed at two scales: macroscopic (including crack length, tortuosity, an‎d fragment size distribution) an‎d microscopic (including fracture process zone (FPZ), percentage of transgranular/intergranular fracture, an‎d petrographic texture analysis). The results showed that with increasing loading rate, the mean fragment size decreased an‎d the percentage of transgranular fracture increased. In SCB specimens, due to the presence of a pre-notch, crack paths were more controlled an‎d changes in tortuosity were more limited, whereas in disk specimens, the greater freedom of crack propagation led to nonlinear variations in crack opening an‎d fracture path. At low loading rates, cracks tended to propagate along grain boundaries, leaving valuable metallic minerals such as chalcopyrite an‎d pyrite intact; however, at higher loading rates, transgranular fracture occurred even in these hard minerals, resulting in greater copper liberation. Petrographic analysis indicated that grain size heterogeneity an‎d differences in the mechanical properties of minerals play an important role in fracture path selec‎tion. Moreover, increasing the loading rate enlarged the FPZ an‎d promoted microcrack development prior to the main fracture. These findings demonstrate that controlling the loading rate an‎d selec‎ting an appropriate specimen geometry can enable the optimization of comminution, in such a way that both energy consumption is reduced an‎d the liberation of valuable minerals is achieved in a targeted manner.

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راحب باقرپور , علي احمدي عامله