In comminution machines, the product properties (particle size distribution, mineral liberation characteristics) and process consumables (energy for size reduction, wear) are affected by various parameters. On the one hand, understanding and optimizing these parameters can provide an energy efficient process and a specified product. On the other hand, a fundamental understanding of the breakage process can even be used for designing new or improved comminution machines. In this thesis, breakage fundamentals are analyzed and set against the principles of various comminution machines. The study of the breakage fundamentals is crucial for a better understanding of the effect of different comminution environments on ore types and their textures in order to achieve a desired product size and liberation. This work defines three main areas of breakage processes with breakage fundamentals, namely “loading mechanism”, “breakage mechanism” and “breakage mode”. The “loading mechanism” is defined as the physical action that is applied to a particle or several particles in order to introduce mechanical stress. The resulting pattern of the particle failure is named “breakage mechanism”. Finally, the “breakage mode” defines the particle breakage in terms of being random or non‐random. Non‐random breakage depends on the ore texture, which can be categorized as preferential breakage and phase boundary breakage. Promoting the breakage mode to the phase boundary breakage could help to increase the liberation degree. Various studies have assessed the effect of ore texture and operational parameters on mineral liberation. While ore texture is related to the particle inherent characteristics, operational conditions such as loading mechanism are related to the comminution environment. In all these investigations, little attempt has been made to explore the combined effects of loading mechanism and quantitative ore texture features on breakage mode and mineral liberation. In addition, a lack of fundamental understanding of the breakage process and mineral liberation can be seen. Accordingly, a more fundamental study of the causes behind the effects of loading mechanism and texture is required in order to optimize the comminution process in terms of mineral liberation. The objective of this work is, therefore, to investigate the effects of different loading mechanisms on particle breakage and breakage mode. In order to achieve this goal, work has started with using two methods including three‐dimensional deformation and two‐dimensional crack quantification. The former method involved X‐ray computed micro‐tomography (XCT) imaging and Digital Volume Correlation (DVC) measurements which determiners the breakage mode in terms of being random or non-random. Whereas the latter was done using an image processing code in MATLAB to quantify cracks in terms of random and non-random breakage (preferential or phase boundary) from Scanning Electron Microscopy (SEM) images. In addition, XCT 3D imaging was used in order to track the propagated cracks in the third dimension. Moreover, phase boundary breakage in magnetite grains was studied qualitatively based on optical microscopy images in order to identify and characterize the propagated cracks.

Within mineral comminution, the product properties (such as particle size distribution and mineral liberation characteristics) along with process efficiency are affected by material related and process environment factors. Understanding and optimizing these factors leads to designing and developing an energy-efficient process with a specified product. A better understanding of interactions between comminution environments and ore properties is the fundamental approach to improve the breakage process. This could lead to achieving a desired product particle size and liberation with the least energy consumption. It can even be used for designing new or improving the performance of comminution machines. In this doctoral thesis, breakage fundamentals are analyzed and set against the principles of various comminution machines: (i) Loading mechanism is defined as the physical action that is applied to a particle or several particles to introduce mechanical stress. (ii) The resulting pattern of the particle failure is referred to as breakage mechanism. (iii) The breakage mode defines the particle breakage and its dependence on ore texture and mineral liberation. To date, most of the research has addressed fragmentation and energy consumption within the comminution system. While optimizing these two factors is used as the approach to have an efficient process, improving mineral liberation is the other approach. In this regard, promoting the breakage mode to preferential in phase and phase boundary breakage could help to increase the liberation degree. According to the literature, mechanical stress is one of the factors controlling mineral liberation. While mechanical stresses are related to the comminution environment, ore texture is related to the particle's inherent characteristics. The thesis aims to identify ore textural micro features and combine them with micro-static and micro-dynamic processes as the key to achieve the most efficient process in terms of mineral liberation, fracture energy, and particle fragmentation. In the first stage of the work, iron oxide ore from the Malmberget mine in Northern Sweden was used and various ore textures were characterized on micro-level to attain the qualitative and quantitative features. These features were not only used for distinguishing textures but were also used later for data interpretation. In the second stage, two distinct ore textures were selected to investigate single particle breakage through four‐dimensional deformation and two‐dimensional crack quantification. The former method determines the breakage mode by quantifying internal deformation and strain in a three-dimensional volume of in-situ X-ray computed micro-tomography measurements. In the latter method, two-dimensional scanning electron microscopy - backscattered electron was used to quantify cracks based on the type of breakage mode. In addition, X-ray computed micro-tomography three-dimensional imaging was used in order to track the propagated cracks in the third dimension. Moreover, magnetite grains cracks were studied qualitatively based on optical microscopy images in order to identify and characterize the propagated cracks. In the third stage, multiple layers of particles of three hematite and three magnetite ore textures were fragmented at two displacement rates. The attained data in terms of breakage mode, liberation distribution, fragmented particles, and fracture energy were compared and their relation to micro-processes and micro-ore features were evaluated. In the fourth stage, multivariate data analysis was applied for finding and predicting patterns in mineral liberation, fracture energy, and fragmentation connected to ore texture features and displacement rate. Moreover, a comparison of ore textural features was also done to find the strongest factors. Finally, the optimal conditions to have the lowest fracture energy and highest liberation were investigated.