The dissertation is devoted to solving an important scientific and technical problem - increasing the efficiency of the functionally oriented technological process of machining titanium alloy products by selecting rational cutting modes, cutting tool geometry and technological environment obtained as a result of problem-oriented analysis of the results of simulation modeling of the power, thermodynamic and stress-strain state of the workpiece and tool in the process of forming.
On the basis of system analysis and generalization of experience in implementing the scientific principles of machined surface engineering, thermodynamic analysis of the influence of tribomechanical factors of the cutting process on the formation of force and stress-strain parameters of products, features of the use of simulation models and criteria for the destruction of hard-to-machine materials, a methodology for recommendations on the rational choice of modes and tooling for the titanium cutting process was formulated, substantiated, theoretically and practically implemented. The methodology of functional-oriented technological design was further developed, according to which the criterion for choosing the structure and parameters of a machining operation is not to minimize the technological cost of manufacturing a part, but to ensure the most effective parameters of the machined surfaces of the product in terms of improving its operational properties (wear resistance, fatigue strength, etc.).
The thesis proposes a new methodology for combining the results of analytical modeling of vibration processes arising during machining of titanium alloy products with the results of simulation modeling of cutting processes. Such a symbiosis of different methods will allow taking into account both the physical and mechanical features of the shape formation of the machined surfaces of a product made of titanium-containing material and the real system of stiffnesses and damping properties of the technological system “Machine-tool-tool-blanket” (MTB) and their complex interaction.
The proposed methodology for the study of tribomechanical processes of cutting titanium alloys described in this thesis differs from the traditional approach and is as follows. First, each time a different declared friction coefficient is proposed as the initial data for modeling, and each such task of simulating the machining process is solved for different parameters and cutting modes. At the second stage, the influence of these predetermined coefficients on the stress-strain (including residual) and thermodynamic states of the workpiece and tool during cutting, as well as on the dynamics of tool wear, etc. is analyzed. The third stage of the study proposes ways to ensure analytically sound tribotechnical cutting conditions. The results of the analysis make it possible to select such design, technological, or organizational solutions that implement the optimal machining conditions in the most efficient way.
As a result of theoretical and experimental studies, it has been proved that the dynamics of dissonant cyclic changes in the components of cutting forces, which is characteristic of machining titanium alloys, is a consequence of an adiabatic shift in the chip formation zone, which is confirmed by the toothed shape of the chips. The mechanism of such chip formation during machining of titanium alloys is due to the loss of thermoplastic stability within the primary shear zone. The results of theoretical and experimental studies confirm that the cyclicity and intensity of the dynamic process of loading and wear of the cutting tool during machining of titanium alloy primarily depend on the speed and depth of cut.
The implementation of the proposed methods for analyzing the results of simulation, analytical and experimental studies of tribomechanical, power, thermodynamic and stress-strain parameters allows us to implement the process of logical, scientifically based, directed selection of cutting modes and tooling for technological operations of machining titanium-containing products, based on solving problems whose causes are unambiguously clear, quantitatively and qualitatively assessed and adequate
