Determination of the Boundaries of Plastic Zone of Metal Deformation During the Cutting

Abstract

The main objective of this work is to analyse the problem of determining the boundary of elastoplastic zone with various methods of machining parts by cutting. The structure of complex theoretical and experimental studies of energy–power parameters of the technological processes is considered. The method for calculating the processes of plastic deformation of metals based on a closed set of equations of continuum mechanics is proposed for the theoretical study of energy–power parameters of the technological processes. The expressions, which make possible the reproduction of the spatial pattern of the strain distribution within the metal at the diamond smoothing and grinding, are obtained. This allows visualizing the mechanism of the deformation and simplifying the analysis of the deformed state of the material. Functional relationship between the power of the deformation and parameters of the machining conditions at the diamond smoothing and grinding is established. Various methods for determining the cutting forces during machining with chip removal as well as approaches to determining deflected mode of a material are considered. A method for express calculation of cutting forces using well-known engineering techniques is proposed. The experimental and calculated data on determination of the sizes of plastically deformable zone of difficult-to-cut materials are analysed. The mechanism of inhibition of dislocations and energy conversion during deformation is considered in detail. As a result, a dislocation–kinetic approach is developed, based on the concept of dislocation as a quasi-particle of a strain quantum. Using the dislocation–kinetic approach, the mathematical model is developed, which allows us to calculate a magnitude of the zone of leading cold hardening that is confirmed by comparison with experimental data. The Starkov’s model is improved; the physical meaning of coefficient in formulas for calculating boundaries of cold-hardening zones is explained. A new similarity criterion is introduced, which relates dissipation of plastic strain energy and rate of rearranging of temperature field.

Keywords

• elastoplastic zone
• cutting forces
• dislocation–kinetic approach
• similarity criterion
• dissipation of energy