Papers by Author: Ning He

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Authors: Zi Yang Cao, Ning He, Liang Li
Abstract: In order to investigate the effects of cutting edge radius on micro/meso-scale cutting process, the current paper is concerned with a fundamental investigation of the contribution of cutting edge radius to cutting temperature, stress field and size effect by means of two-dimensional finite-element simulation for orthogonal cutting process. The results indicated that cutting edge radius has remarkable effects on cutting temperature and stress field, and the existence of cutting edge radius is one of the main reasons generating size effect. The cutting edge radius affects the micro/meso scale cutting process at smaller uncut chip thickness by altering the effective rake angle and enhancing the plowing effect, affecting the material deformation process, expanding and widening the plastic deformation zone, and causing higher energy dissipation due to increased tool-chip contact length.
Authors: Ning He, Liang Li, X.L. Li
Abstract: Gas cooled cutting is an important branch of green machining technology with its excellent cooling performance and is used more and more widely in field of machining. A new method of developing cooling gas generator using semiconductor refrigeration is presented in this paper. Then the main principle, structure and performance of the generator are introduced. In addition, the experiments of high speed milling of Ti Alloy using cooled nitrogen gas were conducted and satisfactory results were achieved. These researches show that the new cooling gas generator has a series of merits such as simple structure, excellent performance, handy operation, low cost and significant spreading value etc.
Authors: Xiao Qiang Xue, Ning He, Liang Li, Wei Zhao, Qi Wang
Abstract: This paper investigates the selection method of vari-speed milling parameters by experiments. The orthogonal experiments of vari-speed milling were studied on a given speed according to the stability lobes, and various parameters were selected. The experimental results show that varying speed milling approach possesses effects on vibration suppression on proper parameters selection though the acceleration damping ratio γa and the sound damping ratio γs. The variance analysis of dual factors test is adopted to data process and the acceleration damping ratio γa is taken as the evaluation index of vibration suppression. Finally, the preliminary conclusions on how to select proper parameters are obtained on the basis of the analysis of the experimental results, which is applied to online monitoring techniques using vibration to achieve automatic control of variable speed cutting.
Authors: Xiao Qiang Xue, Ning He, Liang Li, Wei Zhao, Qi Wang
Abstract: The axial limit cutting depth(LCD) of constant speed were studied, and the stability lobes were gotten by expriments and simulation. The vari-speed milling selected various parameters was investigated by expriments,also.The experimental results show that varying speed milling approach improves the limit cutting depth on proper time and prope parameters selection. According to the comparative analysis of the exprimental results of constant speed and vari-speed milling, it was obtained whether the varying speed milling approach was to be chosen and how to select proper parameters, should be reference to the stability lobes of constant speed.
Authors: Kai Wu, Ning He
Abstract: The existent studies on the milling of the thin-web components are reviewed first, then the cutter selection strategies are discussed theoretically based on the mechanistic model of the milling cutter, and several experiments are carried out to verify the theoretical analysis. At last, the conclusions are given on the cutter selection strategy in the milling of the thin-web components.
Authors: G. Liu, Ning He, Z.L. Man, Liang Li
Authors: Wei Zhao, Ning He, Liang Li
Abstract: Titanium alloys are known for their strong chemical reactivity with surrounding gas due to their high chemical affinity, especially in dry machining. This paper describes a study of chip formation characteristics under nitrogen gas media when machining Ti6Al4V alloy with WC-Co cemented carbide cutting tools at high cutting speeds. Based on the experimental study, a finite element model of two-dimensional orthogonal cutting process for Ti6Al4V alloy at different cutting conditions was developed using a commercial finite element software Deform-2D. Saw-tooth chips with adiabatic shear bands were produced in both experiments and simulations. And the enhanced cooling and anti-frictional effects of nitrogen gas upon the high speed cutting process of Ti6Al4V alloy were analyzed. Results of this investigation indicate that the anti-frictional performance of nitrogen gas has a significant effect on chip formation when machining Ti6Al4V alloy at high cutting speeds. Compared to air, Nitrogen gas is more suitable in improving the contact conditions at chip-tool interfaces and in increasing the shear band frequency of chip formation during high speed cutting of Ti6Al4V alloy.
Authors: Yu Su, Ning He, Liang Li
Abstract: Cryogenic minimum quantity lubrication (CMQL) is a kind of green cooling/lubrication technique, which consists of the application of a small amount of lubricant (6-100 ml/h), delivered in a refrigerated compressed gas stream to the cutting zone. This paper experimentally investigates the effect of CMQL on cutting temperature and tool wear in high-speed end milling of titanium alloys. Comparative experiments were conducted under different cooling/lubrication conditions, i.e. dry milling, refrigerated air cutting, and CMQL. The refrigerated gas equipment was manufactured based on composite refrigeration method to provide the refrigerated air. The experimental results show that application of CMQL resulted in drastic reduction in cutting temperature and tool wear especially when machining titanium alloys at a high cutting speed.
Authors: Mao Hua Xiao, Ning He, Liang Li, Xiu Qing Fu
Abstract: The method to measure the cutting speed when high speed milling nickel alloy Inconel 718 based on semi-artificial thermocouple. The cutting parameters, tool wear and so on the cutting temperature were analyzed. The tests showed that the temperature was gradually increased with the increase of cutting speed. The cutting speed must be more than 600m/min, when the ceramic tools would perform better cutting performance in the high-speed milling nickel-based superalloy. In order to achieve more efficient machining, milling speed can be increased to more than 1000m/min. The impact amount of Radial depth of cut and feed per tooth were relatively small.
Authors: B.Y. Qi, Ning He, Liang Li
Abstract: Hardened steel is widely used for good mechanical property, but its machinability is bad comparatively. It is efficient to enhance metal removed rate when high speed milling (HSM) hardened steel, but tool wear is rapid. In this paper, high-speed milling experiments were carried out for hardened steel with TiAlN coated tools. The effects of milling parameters on tool wear and surface roughness were studied. The influences of different coolants, such as dry, MQL, cryogenic MQL conditions on HSM hardened steel, were compared with each other, results showed that cryogenic MQL HSM hardened steel had better effects that can better reduce tool wear, extend tool life.
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