关键词: 金刚石磨粒, 钛合金, 切削-滚压, 磨削系统, 模糊控制

Abstract: The low thermal conductivity of titanium alloys used in biotechnology and aerospace, as well as the machining tools, leads to a concentration of heat on the surface during mechanical processing. In the case of superconducting diamond abrasives, graphite wear occurs due to catalysis by titanium atoms during grinding. Therefore, both situations necessitate the use of non-recyclable cooling fluids. Based on the superconducting properties of diamond, it is possible to disperse the heat concentration on the surface of titanium alloys and suppress the graphite formation on the cutting edges of abrasive particles through an increase in the edge area of the grinding grit. This enables dry machining. However, it should be noted that the maintenance and dressing of ultra-hard diamond abrasives are difficult. The application of ECD mechanical-thermochemical dressing technology is capable of truncating the cutting edges of diamond abrasives. However, during the truncating process, the unstable nature of the thermal energy generated by the pulsed discharge between the grinding wheel and the electrode hinders effective thermal chemical dressing. Therefore, to address the power of ECD mechanical-thermochemical truncating, a fuzzy control technique for studying truncating parameters is proposed. Additionally, a titanium alloy dry machining method based on the concept of cutting-burnishing with increased area of abrasive edge for dressing is introduced. The aim is to develop a comprehensive dry grinding system that incorporates the logic chain control of the entire process, including machining objectives-abrasive morphology-dressing techniques-and cutting-burnishing conditions. First, a titanium alloy machining model related to the grain cutting-burnishing transition coefficient is carried out based on the truncated grain flank surface area; then, the trigger conditions of the thermal transmission balance at the diamond cutting interface are analysed, and the fuzzy control model for the process conditions in the electro-discharge thermochemical-mechanical hybrid truncating; and finally, the control experiments are conducted on the proposed dry grinding system for the TC4 titanium alloy. The results show that regulating the grain cutting-to-burnishing transition coefficient might change the grain machining behavior from cutting to burnishing. As the coefficient increases, the normal force dispersion on the machining surface, the diamond grain graphitization constraint and the thermal dispersion on the machining surface are activated successively. The system could real-time control the nonlinear-relevant electro-discharge parameters and mechanical movement parameters, achieving the stabilized electro-discharge truncating power within ±5% as well as the dry grinding of titanium alloy at a large depth of cut of 12 μm with a reduced roughness value of 496 nm by 55% and a maintained surface hardness of 340 HV. The proposed dry grinding system yields a high efficiency and a surface-hardening polishing effect.

Key words: daimond grain, titanium alloy, cutting-to-burnishing, grinding system, fuzzy control