Investigation of dynamic characteristics of cutting products from titanium alloy VT6
Students Name: Kyrychuk Vladyslav Vitaliiovych
Qualification Level: magister
Speciality: Mechanical Engineering Technologies
Institute: Institute of Mechanical Engineering and Transport
Mode of Study: full
Academic Year: 2022-2023 н.р.
Language of Defence: ukrainian
Abstract: The object of research is the dynamic characteristics of cutting products made of VT6 titanium alloy. Purpose of the work: The purpose of the research is to determine the optimal cutting parameters of the titanium alloy and structural elements of the VPID system to reduce the amplitude of their oscillations. The causes of oscillations in the process of cutting titanium alloy parts are analyzed. The influence of the amplitude and frequency of oscillations on the quality of the surface of the part, the stability of the tool and the resource of the machine was evaluated. The optimal values of vibration parameters for the effective implementation of the technological process of processing the surface of a part made of titanium alloy VT6 have been noted. It is shown that the rheological modeling of the titanium alloy cutting process in the DEFORM system and the mathematical modeling of the titanium alloy cutting process in the MATLAB system, where the approximate value of the cutting force obtained from the DEFORM system is used as the vibration excitation force of the four-mass oscillating system VPID, can be an effective method of ensuring optimal parameters cutting of titanium alloys. The results of the rheological modeling of the titanium alloy cutting process in the DEFORM system allow us to evaluate the dynamics of the force, stress-strain and thermodynamic state of the tool, taking into account the specified cutting parameters and the changing properties of the processed material. The input data for cutting simulation in the DEFORM system are cutting parameters, namely cutting speed, depth of cut and feed. A characteristic feature when processing titanium alloys is the tendency of the elastic system of the VPID to intense vibrations, primarily due to the high plasticity of titanium alloys, which contributes to the appearance of a specific process of forming a tooth-shaped chip shape. The final result of the rheological modeling is the time dependence of the cutting force, which is approximated by the mathematical expression v serves as an input value for the mathematical model of the VPID system, namely the force that excites the oscillations of this system. To determine the spectrum of amplitude-frequency and phase-frequency characteristics of the dynamic analysis of the cutting process, the method of direct Fourier transformation, implemented as a function in the MATLAB software environment, is used. It is shown that the response of individual elements of the VPID system is different to different excitation frequencies and, as is known, depends on the proximity to resonance of its individual elements. The analysis of the research results showed that the approximation of the frequency of natural oscillations of the element of the VPID system to the frequency of the forcing force with a significant value of the amplitude (local maximum) leads to a significant increase in the amplitude of the oscillations of the tool relative to the part (approximately 12 times). This significantly affects the accuracy and quality of machining (primarily, the vibrational component of roughness). The obtained results of mathematical modeling indicate that for effective and high-quality processing of the part, the natural frequencies of oscillations of the elements of the VPID system should be provided so that they are sufficiently far from the maximum amplitude-frequency values of the cutting force. This is especially important for processing titanium alloys, since the dynamics of the cutting force has a well-defined sinusoidal character. In order to carry out experimental studies of the dynamics of the cutting process of titanium alloy VT6, an experimental installation was developed and created, which is made on the basis of a lathe and consists of a workpiece (material VT6), a turning cutter (material VK8), a vibrometric transducer (piezo-accelerometer UC 507-1 ), a 3-cam cartridge, a 2-channel USB oscilloscope (OWON VDS1022) and a computer for recording and storing experimental data. A comparison of the simulation results and experimental data allows us to state a high level of adequacy of the theoretical and real representation of the vibration processes that occur during the mechanical processing of the VT6 titanium alloy. The main idea of the described scientific method of ensuring the accuracy and quality of machined surfaces as a result of mechanical processing is to determine the dynamics of the cutting force in one of the simulation modeling systems (Deform, LSDyna, Abaqus) and to solve the system of equations of the four-mass system, which will make it possible to avoid resonant convergence of the amplitude frequency characteristics of the forcing and natural oscillations of the VPID system. Our proposed approach to the study of vibrational processes occurring during cutting of titanium alloy consists in the fact that we propose to combine analytical modeling of the dynamics of the cutting process with the results of simulation modeling. This ultimately contributes to solving two main tasks: determining rational cutting conditions and choosing ways to achieve the required quality of the treated surface and the layer adjacent to it, in which the initial physical and mechanical properties of the titanium alloy would be preserved or other values of them, guaranteeing characteristics would be obtained , necessary for the product in potential operating conditions.