答辩博士：Muhammad Jamil
指导教师：Prof He Ning
论文题目：Fundamental research on dry ice hybrid lubri-cooling for milling Ti-6Al-4V
答辩委员会：
主席：张为民 教授/博导 同济大学
委员：黄 翔 教授/博导 南京航空航天大学
武 凯 教授/博导 南京理工大学
李 亮 教授/博导 南京航空航天大学
赵 威 教授/博导 南京航空航天大学
秘书：陈 妮 讲师 南京航空航天大学
时间：2021年6月10日09:30
地点：南航明故宫校区A6号楼218室
Brief Introduction：
At present, the modern manufacturing sector should take into account the environment and productivity
at the same time. Under the premise of this, the sustainable improvement of processes and products has
become the driving factor for manufacturing research. Cryogenic cooling and minimum quantity lubrication
(MQL) are getting attention to improving machinability and for cleaner production. However, MQL or
cryogenic cooling is insufficient in the cutting ofhard-to-cut Ti-6Al-4V alloy at high levels ofcutting speed.
Since the poor thermal conductivity of Ti-6Al-4V alloy permits concentrated heat at the cutting zone which
softens the workpiece material as well as reduces the hardness and strength of tool material at the same time.
Therefore, nowadays hybrid lubri-cooling is under investigation due to its synergistic effect of cooling and
lubrication in cutting. In this research study, ethanol, ester oil, and hybrid ethanol-ester oil coolants/lubricants
with/without dry ice are proposed and investigated their effect in machining with the anticipation of their
significant contribution to improving the machinability of hard-to-cut materials at higher cutting conditions.
To this aim, the objective of this research is to evaluate the thermophysical, tribological, and machinability
performance measures of hybrid lubri-cooling with/without mixing dry ice.
Main research contribution and achievements：
（1）Investigation of thermophysical, tribological, and thermal properties ofhybrid lubri-coolant: The ethanol, ester oil, ethanol-ester oil in the ratio of 1:0.25, 1:0.50, and 1:1 with/without dry ice are prepared to
analyze thermophysical properties (thermal conductivity, density, specific heat, viscosity, and evaporation
partially/fully) to reduce the post-process cleaning.:
（2）Assessment of simulation and experimental temperature under hybrid lubri-cooling: The titanium
alloy (Ti-6Al-4V) material, carbide tool, heat transfer coefficient, and friction coefficient for ethanol, ester oil, and hybrid ethanol-ester oil with/without dry ice are applied in Finite Element Method (FEM) to simulate for the cutting temperature.
（3）Surface integrity analysis under hybrid lubri-coolants of face-milling Ti-6Al-4V: Face-milling
experiments are carried out on Ti-6Al-4V workpiece under different hybrid lubri-cooling. The cutting speed
and feed per tooth are varied to evaluate their effectiveness regarding workpiece surface quality, surface/subsurface hardness, and residual stresses.
（4）Investigation of tool wear and tool life under hybrid lubri-coolant of face milling Ti-6Al-4V: The milling experiments are organized under hybrid lubri-cooling to evaluate the effect of proposed coolants/lubricants on tool life and tool wear mechanism in the face-milling of Ti-6Al-4V. Energy dispersive spectroscopy (EDS) analysis such as Line-EDS, point-EDS, and EDS-mapping were carried out on the worn edge to underscore the wear mechanism.
Key innovations：
（1）(1) A novel hybrid lubri-cooling method, i.e. utilizing dry ice hybrid ethanol-ester oil as cutting medium, was proposed for high-performance machining of difficult-to-cut materials. It has a synergistic effect of cooling and lubrication to improve the machinability of difficult-to-cut materials. Moreover, it is innocuous for the operator and biodegradable.
(2) The thermophysical and tribological characteristics of the developed hybrid lubri-coolants are precisely determined by FEM and experiments. The fundamental lubri-cooling mechanism of the hybrid lubri-coolants was investigated. It was found that the hybrid mixture of low temperature can offer a significant enhancement in heat transfer characteristics, and the reduction in friction coefficient and friction force that ultimately leads to a reduction in surface roughness.
(3) The cutting behavior and its mechanism under dry ice hybrid lubri-coolants regarding cutting temperature generation, surface integrity, and tool wear were investigated by carrying out FEM and experiments on machining Ti-6Al-4V alloy. The experimental findings concluded the reduction of plastic and frictional heat generation with superior surface quality, compressive residual stresses, and longer tool life under dry ice hybrid lubri-cooling.
