Papers by Author: Ya Dong Gong

Abstract: Micro-grinding is an important processing method in micro-manufacturing field. The influence factors of surface quality in micro-grinding are discussed in the article. The models of finite element analysis (FEA) in micro-grinding H62 with electroplated CBN micro-grinding tool were established. The influence of different grinding factors on the surface quality of the work-piece was discussed by FEA. Different grains sizes were considered to reveal the influence rules on surface roughness in grinding experiments. The results show that the surface roughness decreases with the decreasing of the feed speed and the increasing of the grinding speed. A better surface quality can be achieved with smaller grains sizes. The minimum surface roughness can reach 481nm in side grinding H62.

Abstract: Single crystal Ni₃Al-based superalloy has excellent comprehensive performance.To study the micro-milling surface quality of Ni₃Al-based superalloy, this article used two-edged carbide alloy micro-milling tool with 0.8mm diameter, then orthogonal experiment of three factors and five levels was implemented to the micro-milling of typical single crystal Ni₃Al-based superalloy IC10. The primary and secondary factors of the impact on the micro-milling surface quality were found from spindle speed, feed rate, milling depth by range analysis, and the ideal cutting process parameters combination was optimized and obtained, then its cutting mechanism and the reason of affecting the surface quality were analyzed. The experiment result has certain guiding significance to the micro-milling mechanism of single crystal superalloy.

Abstract: This paper uses micro-grinding tool with 500# grains and 0.9 mm diameter to grind nickel-based superalloy Inconel600 through three factors(grinding depth, feed rate, spindle speed ) at three levels orthogonal grinding experiment in mesoscopic scale. Then according to the range analysis of surface roughness, the primary and secondary influencial factors are found; the micro grinding parameters are optimized ,the results show: the influence of the feed rate(v_f)is the biggest, followed by the spindle speed(n), the grinding depth(a_p) is minimal, when n=50kr/min, v_f=100μm/s, a_p=6μm, the grinding surface roughness is minimum: R_a=579nm; finally , the regression mathematical model of micro grinding surface roughness is established, the relative error of the calculated value and experimental measurements is low, showing that this regression mathematical model is accurate and effective. This study provides a theoretical basis for the micro grinding parameters and surface quality control of nickel-based superally.

Abstract: In this paper, molecular dynamics (MD) model is explored to study single-crystal nickel micro-nanomachining mechanism. Accordingly, LAMMPS would implement the simulation of nanometric cutting process, and snapshots at different steps are obtained by VMD and OVITO. On this basis, a reasonable explanation is given to the forming mechanism of chip and surface machined in the machining process of single-crystal nickel. The result of work-piece temperature distribution shows that there is a temperature gradient around the machining zone, where chip part achieved the highest temperature. Moreover, a large number of dislocations are observed. Part of dislocation atoms move forward and generate the chips, taking a lot of heat. Another part of dislocation atoms combine with the work-piece surface atoms with elastic recovery, and form the machined surface.

Abstract: Through turning experiment of machinable glass ceramics, the characteristics and law of turning force was studied. Results indicated that the overall changing process of cutting force was sinusoidal. If the cyclic fluctuation caused by system vibration was neglected, the changing process of turning force was scalariform. Through designing orthogonal experiment and applying numerical simulation of multiple regressing theory based on least square algorithm, mathematical model of turning force was established related with process parameters. R-test, F-test and P-test were carried out on the model respectively. The test results showed that the model had high precision. It could guide to cut machinable glass ceramics on prediction and controlling of turning force in some degree.

Abstract: There is a vitrified bond CBN point grinding wheel with coarse grinding area slope angle θ. This new grinding wheel has higher removing rate and better machining accuracy than conventional wheels. The design and manufacture principle of the new grinding wheels are studied in this paper. These wheels with different coarse grinding area slope angle θ are used to grind the stepped shaft of QT700 with a series of grinding parameters.VHX-1000E microscopic system and Micromeasure system are used to measure the surface quality of workpiece. In the same group of grinding parameters, compare the effect of these different wheels on surface roughness. The effect of deflection angle α on surface roughness is generalized.

Abstract: The micro-processing technology has gradually become a hot topic problem, especially in micro-scale milling chatter prevention with the development of the information age. In allusion to the actual case of micro-milling, the dynamic theoretical research is analyzed in-depth about the Fourier method and the average tooth angle method. Compared to two ways, the former is close to the actual processing requirements. The lobes are obtained use the two ways. Micro milling parameters are selected in the stable area and unstable region. Stable and non-stable curve and surface quality of machined parts are obtained after micro-milling test. The chatter points, non-chatter point and uncertain point are obtained in the high spindle speed, which are consistent with theoretical analysis. In contrast, the distribution of chatter points in the low-speed spindle speed. The reason is that the damping effect is produced in the micro-scale milling process. The research of micro-scale milling chatter, which has a certain significance to improve parts of precision machined parts, reduce the wear and tear of the micro-milling blade and extend micro-tool life.

Abstract: The cutting edge radius R_e leads to the minimum uncut chip thickness in micro machining. The single-edge single-grit model was developed for micro mill-grinding in this paper. Simulations for Ti6Al4V were performed in various cutting depths, and the minimum uncut chip thickness of micro mill-grinding was confirmed to be between 0.25R_e and 0.3R_e (approximate 0.275R_e). Various grain heights of protrusion were investigated to discuss the influence of grain depths of cut on the minimum uncut chip thickness. The minimum uncut chip thickness will increase if the grinding debris forms, while it will get smaller if the grinding debris cant be generated.

Abstract: The thermocouple temperature measurement method was adopted to measure the surface temperature in micro-grinding experiment. According to the different grinding depth, the appropriate processing parameters were chosen to find out the temperature field distribution on the surface and in different depth of subsurface. It provided a reference basis in order to prevent the grinding burn. It proves that the method combining the finite element theory with experiment method is correct and feasible. It is a basis of the factors of the grinding temperature and surface integrity of the parts. Further more, it is of great significance that grinding mechanism and surface quality improving of the parts be discussed thoroughly.

Abstract: Micro mechanical processing is the effective method for machining micro scale parts. Micro mill-grinding technology is presented based on micro milling and micro grinding processes. The machining principle of micro mill-grinding is studied, and compound tools for micro mill-grinding are fabricated based on spraying technology. Experiments are performed on Al 6061-T6 with the three-dimensional micro machining system. The results show that submicron surface roughness can be obtained by micro mill-grinding. Abrasive grains of mill-grinding tools fabricated by spraying method shed easily. Smaller abrasive particle size improves the surface quality and increases the tool life.