Papers by Author: Dong Liu

Abstract: A new simple methodology to determine the flow stress of material is presented and Johnson–Cook (JC) constitutive model of titanium alloy Ti6Al4V is obtained via this approach. The JC model is verified by comparison between simulations and experiments. The results show that the model is suitable for cutting simulation. This simple method can be used to determine conveniently JC model not only in the scientific research but also in the workshop production.

Abstract: The Composites are difficult machining materials which widely used in aerospace industry due to their excellent mechanical properties. Tool wear and delamination are considered the major concern in manufacture the parts and assembly. The orthogonal experiment method was used to investigate the milling force of carbon fibred composite with diamond mill tool. The experiments were carried out under air cooling cutting conditions. The experimental results indicated that the feed rate was the most significant fact which affect the average peak value of the milling force. the average milling force decreased with the cutting speed increased and increased with the feed rate and width of cut increased.

Abstract: Insulating glass is an important architecture energy saving material, large vertical glass edging machine is one of the indispensable facilities on insulating glass product line, the vibration situation of grinding wheel mechanism on large vertical glass edging machine has an important effect on grinding quality. The paper has established the dynamic equation of grinding wheel mechanism and it was simulated by using MATLAB. The simulating result indicates that the distance (l) of grinding wheel mechanism to the top bearing has an important influence on the vibration of grinding wheel mechanism, the larger l value the higher amplitude, it should be considered when designing large vertical glass edging machine. In addition, the paper puts forward some effective solutions to reduce the vibration amplitude of grinding wheel mechanism such as improving the dynamic balance precision of grinding wheel, reducing the mass of grinding wheel mechanism and enhancing the rigidity of ball leadscrew.

Abstract: The Composites are difficult machining materials which widely used in aerospace industry due to their excellent mechanical properties. Tool wear and delamination are considered the major concern in manufacture the parts and assembly. The thrust force and torque affect the tool life and delamination mostly. This paper investigated the drilling force and torque of carbon fibred composite with carbide drilling tools and half core drilling tool. The experiments were carried out under air cooling cutting conditions and the drilling force using carbide tool and half core tool were compared and the experimental results indicated that the drilling forces using half core drill were smaller than that of using carbide tool.

Abstract: High-temperature alloy GH536 is a difficult-to-cut material. The paper finished milling experiment of GH536 with cemented carbide tool based on orthogonal test, obtained regulations between milling force and feed speed, cutting depth and spindle speed. Results indicate that the milling force increases with feed speed and cutting depth, decreases with spindle speed. Exponential formulas of milling force were obtained by SPSS, variance analysis showed it agreed well with experimental data.

Abstract: Titanium alloys are widely used in aerospace industry due to their excellent mechanical properties. Because of their low thermal conductivity, high chemical activity, large friction coefficient and so on, such problems occur during the cutting process as high cutting temperature, large specific cutting force and serious tool wear, leading to low machining efficiency. The cutting force, forms of tool wear; wear mechanics were experimentally studied and analyzed while machining titanium alloy TC4 using carbide tools YS8 and YG8. The experimental results indicated that the tool wear of YG8 influenced cutting force not very remarkable when flank wear smaller than 0.25mm. But when the flank wear was bigger than 0.25mm, the cutting force increased rapidly with the flank wear increased. And the tool wear influenced the cutting force dramatically. The forms of tool wear during machining TC4 using carbide tool were adhesion wear, tool chipping and. The desquamation and chipping of tool caused by adhesion wear were the main reason of the tool failure.

Abstract: Silicon–aluminum alloys (Al-Si), with Si contents up to 12% are important materials in automotive and aeronautical industries due to their low density and high wear resistance. The cutting force, surface roughness and tool wear of diamond tools and cemented carbides tool were compared when turning Al-Si alloy. The results indicated that there wasn't remarkable difference between diamond tools and cemented carbides tool in cutting force and surface roughness when rough turning silicon-aluminum alloy. While in finish turning, less cutting force and surface roughness can be obtained when using diamond tools. The flank wears of diamond tools were less than cemented carbides. It was concluded that diamond tools can improve machining characteristics and reduce tool wear.

Abstract: A methodology to determine the flow stress of material was presented and Johnson–Cook (JC) constitutive model of titanium alloy Ti6Al4V was obtained based on cutting experiment and optimization. This JC model was verified by comparison between simulations with different JC models respectively and experiment. It showed that the accuracy of simulation of cutting force has an increase and the new model is more suitable for cutting simulations. This simple method could improve the accuracy and reliability of the cutting simulation, and could be used to establish the constitutive model of workpiece with more accuracy.

Abstract: The formation of shear localized chips in orthogonal machining of Ti-6Al-4V was investigated. The chips in different cutting velocities were collected and the structure of the adiabatic shear localization was examined by optical microscope and SEM after polishing and eroding. The serrated coefficient, serrated frequency and fibred coefficient were proposed in this paper to characterize the degree of serration and plastic shear flow of the chip quantitatively. Experimental results show that the width of the shear band decreased and the fibred coefficient of the shear band increased as cutting speed increased. The serrated and frequency, the serrated coefficient increased with the increase of cutting speed in the experimental range of cutting speeds.

Abstract: The machining of titanium alloys classified as difficult machining materials. It is a major problem how to improve the machining efficiency of titanium alloys. The TC4 and YS8 natural thermocouple pair was calibrated and the variation of electromotive force with change of temperature was obtained. The calibrated results were used to measure the cutting temperature while machining TC4 and the variation regulation of cutting temperature with cutting speed was obtained.