Mathematical Model of State of Stress in Cutting Area During Synthegran Machining

Synthegran is composite material compounded of an epoxy binder and high-strength mineral filler. Fillers include different fractions of granite macadam with various grain sizes from 1 to 15 mm. Synthegran is used in order to substitute iron casting employed for basic parts of lathes, machines, and tools. Nowadays, the behavior of this material in the process of manufacturing parts and assemblies from it and while machining has not been sufficiently studied yet. Synthegran machining has several features distincting it from similar metal machining. It is explained by characteristic properties and the structure of material to be machined. This article deals with the mechanism of swarf formation during machining of the mentioned composite by a blade cutting tool. Due to the material being fragile, the fundamental principles of the theory of fracture mechanics as well as the theory of metal cutting were analyzed. The mathematical models of cutting process, which allow us to determine state of stress in cutting area and predict the quality of synthegran surface, were proposed. The research demonstrated that peak normal and shear stresses during machining occur below the cutting surface. Thus, during swarf formation, the crack will spread deep into a material surface. Consequently, the quality of the composite surface is fully determined by a trajectory of crack propagation under the formation of discontinuous chip.