A technique for experimental determination of the resistance of materials to plastic shear upon their processing by cutting

Abstract

Theoretical or theoretical-experimental methods are widely used when studying various techniques for processing materials, cutting among them. The physical and mechanical properties of the materials being processed are to be taken into account along with the process parameters (mode, geometric parameters of the machining tool, etc.). The resistance of the material to plastic shear present in the calculated dependences for determination of the force and temperature in the cutting zone and the temperature in the surface layer of the workpiece, as well as for determination of the quality parameters of the surface layer of the part (the residual stresses, degree and depth of work hardening, roughness, and others) and the accuracy of processing is used in all the aforementioned methods in addition to the ultimate tensile strength and the modulus of elasticity of the processed material. Previously, when determining the numerical value of the resistance of the processed material to plastic shear, the latter was considered as a function of the tensile strength of the processed material. However, an increased temperature observed in the cutting area which depends on the combination of the processed and tool materials, the mode of processing, and on the geometry of the cutting part of the tool was not taken into account. The value of the effective cutting force was also ignored though this value is determined by the same parameters which determine the temperature in the cutting zone. The mechanical characteristics of the processed material are known to depend on the temperature. In this regard, the resistance of the processed material to plastic shear was assessed at a certain temperature determined by the technological conditions of processing. The goal of the study is to prove the necessity of determining the resistance of the processed material to plastic shear to be used in theoretical determination of cutting forces, temperature in the cutting zone, and the quality parameters of the surface layer of the part. The dependence is given to determine the value of the resistance of the processed material to plastic shear under optimal processing conditions that ensure the minimum wear of the cutting tool taking into account the parameters of the cutting process and the geometry of the cutting part of the tool. Processing conditions that determine the temperature and force in the cutting zone are taken into account by chip shrinkage in the formula for determining the value of the resistance of the processed material to plastic shear. The use of the proposed technique can improve the accuracy of calculations of the quality parameters of the material of the surface layer of the part and the accuracy of processing.