Stress distribution along the plastic-elastic blade-to-chip contact area

Abstract

The purpose of this paper is to derive new formulas for the exponent of distribution function for normal stresses and values of shear stresses along the plastic blade-to-chip contact area. The research technique consists in using a new design pattern for the equilibrium of the chips and introducing a constant value of the shear friction factor in the shear plane for individual groups of steels.The starting basis for determining the parameters of index equitation and corresponding stresses is the developed system of equations of empirical dependences of the tangential, radial and axial components of the cutting forces on the depth, feed and cutting speed at certain front rake angle and radius at the vertex, the rate of wear along the rear surface with certain exponents, the dimensional proportionality factor and correction factors for the grade of the process material and cutting conditions. There are two decision options: The derivation of formula for the dependence index is based on the conditions of equilibrium of the chips under the action of resulting forces and moments of forces from the side of the shear plane and from the side of the front surface. Research results. Steel 45 (pearlite class) in comparison with steel 12KH18N9T [12Х18Н9Т] (austenitic class) has larger values of the exponent of distribution function for normal stresses and shear friction factor in the shear plane, and lower values of shear stresses in the shear plane, average and maximum normal stresses, coefficient of sliding friction of chips along the blade and shear stresses on the plastic contact area. An increase in the front rake angle leads to an unambiguous decrease in the length of the shear area and the length of blade-to-chip contact area, as well as an increase in the sliding friction of the chips along the blade and the shear stresses on the plastic blade-to-chip contact area. Scientific novelty. The novelty of the index equitation consists in the introduction of the shear friction angle in the shear plane, which, in contrast to the coefficient of sliding friction on the front surface, in a large measure takes into account the physical and mechanical properties of steel and depends almost not at all on the operating parameters, geometric parameters and contact phenomena of the cutting process. Practical importance. The resulting formula connects the shear stresses along the plastic blade-to-chip contact area with the shear stresses in the shear plane, and it is intended to make careful calculation of the friction forces on the front surface of the blade.