Papers by Author: Song Zhang

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Authors: Xiu Li Fu, Xing Ai, Song Zhang, Yi Wan
Abstract: Accurately material constitutive model is essential to understand and predict machining process. High temperature split Hopkinson pressure bar (SHPB) test system is used to investigate flow stress behavior and characteristics of 7050-T7451 aluminum alloy. Specimens are tested from 200°C to 550°C at intervals of 50°C and room temperature, at strain-rate of 2800s-1. The experimental results show that flow stress is strongly dependent on temperature as well as strain rate, flow stress decreases with the increase of temperature, while increase with the increasing of strain rate. The material parameters are determined for both Johnson-Cook constitutive equation and modified Johnson-Cook constitutive equation. The modified JC equation is more suitable for expressing the dynamic behavior of 7050-T7451 aluminum alloy.
Authors: Feng Jiang, Jian Feng Li, Jie Sun, Song Zhang, Lan Yan
Abstract: For the analysis of cooling effect, the cutting inserts were heated to 900°C and then exposed in the room-air and cold-air with different pressure respectively. The temperature variation were recorded by infra-red (IR) pyrometer. The temperature-dependent global heat transfer coefficients were estimated by the theoretical analysis and experimental data. The finite element analysis (FEA) was employed to simulate the cooling process and modify the estimated heat transfer coefficients. The heat transfer coefficients decreased from 55.1 W/m2•°C (800°C) to 9.32 W/m2•°C (350°C) in the natural cooling and approximately 300 W/m2•°C (600°C) to 60 W/m2•°C (300°C) in the cold-air cooling. Cold-air cooling greatly increased the heat transfer coefficients, but it seemed the air pressure had little pressure on the heat transfer coefficients.
Authors: Yuan Wei Wang, Song Zhang, Jian Feng Li, Tong Chao Ding
Abstract: In this paper, Taguchi method was applied to design the cutting experiments when end milling Inconel 718 with the TiAlN-TiN coated carbide inserts. The signal-to-noise (S/N) ratio are employed to study the effects of cutting parameters (cutting speed, feed per tooth, radial depth of cut, and axial depth of cut) on surface roughness, and the optimal combination of the cutting parameters for the desired surface roughness is obtained. An exponential regression model for the surface roughness is formulated based on the experimental results. Finally, the verification tests show that surface roughness generated by the optimal cutting parameters is really the minimum value, and there is a good agreement between the predictive results and experimental measurements.
Authors: Feng Jiang, Jian Feng Li, Jie Sun, Song Zhang, Lan Yan
Abstract: In this study, orthogonal arrays were applied in the design of the experiments and Ti6Al4V end-milling experiments were performed on the DAEWOO machining center. The white light interferometer was used to obtain the average surface roughness (Ra). A quadratic model was proposed to fit the experimental data of the surface roughness. And the fit model was used to optimize the cutting parameters in the given material removal rate. Finally the verification experiments showed good agreement with the estimated results.
Authors: Song Zhang, Xing Ai, Jian Feng Li, Xiu Li Fu
Abstract: With the rapid development of high-speed machining technology, more and more machining centers have been equipped with the HSK toolholders. In this paper, the performances of the HSK spindle/toolholder interface, such as the axial movement, the radial deflection and the contact stress distribution, were simulated by means of the finite element method and compared with the traditional BT interface. From the simulated results, it was pointed out that the performances of the HSK interface were obviously superior to that of the BT interface, and the HSK interface was much more suitable for high-speed machining.
Authors: Feng Jiang, Jian Feng Li, Jie Sun, Song Zhang, Yong He
Abstract: Friction coefficient is an important index to evaluate the cooling and lubrication effects. In this study, the orthogonal milling experiments with different cooling/lubrication methods (dry, cutting fluid, MQL) were performed and the milling forces were measured to calculate the apparent friction coefficients with the mechanistic model. The effects of cutting parameters and cooling/lubrication methods on the apparent friction coefficients were analyzed.
Authors: Feng Jiang, Jian Feng Li, Jie Sun, Song Zhang
Abstract: Surface roughness is an important item to evaluate the surface quality. Many researches focused on the optimization of cutting parameters in the specified cooling/lubrication conditions. But the effect of different cooling/lubrication conditions was still less considered. Aimed at this problem, the effect of cutting parameters on the average surface roughness (Ra) in the different cooling/lubrication conditions, including MQL, wet, dry cutting, was analyzed in this study. Orthogonal arrays were applied in the design of the experiments and Ti6Al4V end-milling experiments were performed on the DAEWOO machining center. The white light interferometer was used to obtain the 3D profile of machined surface and calculate the Ra values. The regression analysis and statistical analysis of variance were employed in the process of the experimental data. The relationships between Ra and cutting parameters in the different cooling/lubrication conditions were obtained and the optimum values of the cutting parameters in the range of the experiments were selected.
Authors: Song Zhang, Jian Feng Li, Feng Shi Liu, Feng Jiang
Abstract: Titanium alloys are widely used in the aerospace industry for applications requiring high strength at elevated temperature and high mechanical resistance. However, titanium alloys are classified as extremely difficult-to-cut materials owing to their physical, chemical, and mechanical properties, which result in the low material removal rate and the short tool life. This paper presents an experimental research of the tool wear patterns and relevant wear mechanisms during high-speed milling of Ti-6Al-4V with cemented carbide inserts. SEM-EDX analysis showed that nose wear and edge wear were the main tool failure modes during high-speed milling process, which were different from the wear patterns under traditional cutting conditions. Adhesion, attrition and diffusion wear mechanisms, as well as the cracks were responsible for the tool wear.
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