|英文题名||Simulation and theoretical analysis of metal cutting process under tool vibration|
|关键词||高速切削 材料失稳 振动切削 数值模拟|
Metal machining, as a main forming processing of materials, has been widely applied in manufacturing industry. However, metal cutting processes is inevitably accompanied with the vibration phenomena of tool system, which not only decreasing the machining quality but also reducing the tool life . Therefore, it is necessary to deeply investigate the cutting mechanisms of metals involving vibration phenomenon of tool system.
Metal cutting process is usually involved in two types of mechanical vibration of tool system, called forced vibration (FV) and self-excited vibration (SEV). The tool FV is induced by exerted artificial conditions. It has been found that it usually produces bad effects on the cutting process, however, for the prescribed vibration frequency it can evidently improve the machining quality. The tool SEV attributes to internal harmonic excitations of tool-workpiece system and physical self-feedback. The rough machining surface, the instability of multiple shear bands and the friction at tool-chip interface may cause the SEV of tool system. The SEV always has a detrimental effect on the machining quality and the tool life.
In this master's thesis, the numerical simulations and theoretical analysis on the vibration cutting process of metals are performed successively. In numerical simulations, the one-tool and double-tool cutting models are established based on the coupling Eulerian-Lagrangian (CEL) finite element method, to simulate the FV and SEV cutting processes respectively. And in theoretical analysis, linear perturbation method is employed to analyze the chip formation mechanisms in the FV cutting process and the stability of the tool system vibration in the SEV cutting process. The main studies focus on the following aspects:
1. In the numerical simulation based on the CEL FE model, the effects of tool vibration frequency on chip form mechanisms was studied. Moreover, the cutting force and plastic instability behavior of chip material under different cutting conditions were also investigated.
2. Linear perturbation method was used to analyze the instability behavior of the adiabatic shear band of chip material in high-speed cutting process, and the influence of tool FV motion on the shear band instability was analyzed. The instability criterion is obtained for the evaluation of plastic flow stability of chip material in the FV cutting. The reasons of the shear banding formation and the transition from serrated chip to continuous chip are discussed.
3. The effects of the wave machining surface generated in cutting and the cyclic shear band instability on the tool SEV process were simulated by the double-tool FE model. Theoretically, the controlling equations describing the SEV process was obtained and the relationships among the wave surface frequency, the shear band instability frequency and the tool vibration frequency were established for studying the stability of the SEV process of tool system.
4. Vumat material subroutine was compiled through the ABAQUS material constitutive subroutine interface. The competed Vumat subroutine could simulate the cutting process of different metals and study the effects of different material constitution models on vibration cutting processes.
The studying results of this thesis are expected to be helpful for better understanding of the metal machining in engineering application.
|孙宗涛. 金属振动切削过程的数值模拟及理论分析[D]. 北京. 中国科学院大学,2018.|