Authors: Yu.N. Linnik, V.Yu. Linnik

Title of the article: Mechanisms of maximal loads on cutters and cutting heads of coal mining machines

Year: 2021, Issue: 4, Pages: 16-21

Branch of knowledge: 05.05.06 Mining machines

Index UDK: 62-2, 622.2.

DOI: 10.26730/1816-4528-2021-4-16-21

Abstract: Fracture of coal seams having a complex structure and enclosing solid discontinuities (solid inclusions and hard dirt bands) is associated with generation of impact loads on cutters and cutting heads of mining machines. This impairs efficiency of coal cutting and causes premature failure of different components and parts. For the reasoned choice of operating modes of cutter–loaders and in order to calculate strengths of cutters and transmissions, it is required to take into account the level and mechanisms of peak loads on cutters in cutting complex structure coal seams. To this effect, this paper, in its first part, describes the research findings on influence exerted by the cutting mode and by geometry of cutters on the impact loads in various scenarios of cutter–solid inclusion interaction. It is found that when a cutter cuts an inclusion or touches it, the size of the inclusion has no influence on the value of the peak load. In case of tear-out of an inclusion, the peak cutting force value essentially depends on the size and shape of the inclusion, as well as on the brittleness and plasticity of coal as these properties govern coal–inclusion cohesion. Out of all modes of cutter–solid inclusion interaction, the highest loads arise in the mode of central cutting of inclusions. The peak and average peak values of the cutting and feed forces are determined for the cases of central cutting of carbonate inclusions, most common in coal, with sharp and dull cutters. The authors propose relations to calculate maximal loads on cutters and action times of these loads as functions of cutting mode, as well as cutter design and geometry.
In the second part of the paper, the mechanisms and behavior of loads in short-term cutting of large (unbroken) and solid inclusions by a group of cutters are discussed. The maximal loads on groups of cutters on cutting heads can also arise in gradual stalling when the average loading level approaches the tractive effort torque of electric motor when a group of cutters cuts many solid inclusions simultaneously, or in undermining of roof rocks, or in cutting hard dirt bands. The probabilities of solid inclusion cutting by a cutter are determined for different outputs of a cutting head, and the action times of the maximal peak load in cutting a coal strip 100 m long are assessed. The relations are proposed to calculate the levels and action times of maximal loads on a group of cutters in cutting solid inclusions, as well as the coefficients of variation in the loads and the loading inequality of a cutting head. The results obtained by the authors should be taken as a basis in determination of the maximal instantaneous torque in the cutting head transmission to be used later on in calculation of the long-term strength of the transmission components.

Key words: coal cutter cutting head coal mining machine solid inclusions cutting force maximal loads cuttability depth and width of cut

Receiving date: 02.03.2021

Publication date: 25.08.2021

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