Introduction to Three Crushing Theories

The crushing theory is mainly used to study which factors affect the energy consumption of ore during the crushing process, and to determine the amount of work done when external forces crush the ore.

When the material is broken, it first breaks along a more fragile section. Compared to the newly generated fragments, the original fragile surface no longer exists. So during the crushing process, fragile points and surfaces will gradually disappear, and as the particle size of the material decreases, the number of internal defects will decrease, making it more and more sturdy. Therefore, when crushing small particle sized materials, more energy will be consumed. Some of the work consumed in the crushing process will deform the crushed materials and distribute them in the surrounding space in the form of heat energy, while the other part will be used to form a new surface and become the Free surface energy of solids.

Due to the complexity of the crushing process, the energy consumption is related to many factors, such as the physical and mechanical properties of the ore, the crushing method used, the shape, size, and temperature of the ore. Therefore, existing fragmentation theories do not fully explain the essence of ore fragmentation, and all have certain limitations. At present, there are three main hypotheses of fragmentation theory: area theory, volume theory, and crack theory.

(1) Area theory

The function performed in the process of crushing ore is to generate a new surface area, so the work consumed in crushing ore is directly proportional to the new surface area generated, or the unit work of internal force is directly proportional to the area increment of the broken section of the material.

(2) Volume hypothesis

The work done when crushing ore is used to deform the ore block. When the deformation reaches the point where crushing occurs, the work consumed by crushing ore is proportional to the volume change of ore block, or the unit work of internal force is proportional to the micro amount of deformation volume of crushed material block when crushing similar materials into products with similar geometric shapes.

(3) Crack theory

In the process of ore crushing, the work of external forces first causes the mineral to deform. When the local deformation exceeds its critical point, cracks are generated. After the cracks are formed, the deformation stored in the object can cause the cracks to expand and generate cross-sections. The useful part of the input work will be converted into surface energy on the newly formed surface, while the rest will be converted into thermal energy loss. Due to the proposed power consumption theory surrounding the formation and expansion of cracks, it is called the crack theory.