Papers by Author: Li Fa Han

Abstract: In this paper, the morphology of machined surface in turning NbC particle reinforced iron-base composites was investigated. It indicates that since the dispersive distribution of reinforcing particles, the machined surface is likely to occur various defects such as tool traces, small pits, discontinuous grooves or micro-cracks. Moreover, the surface generation mechanism was discussed. There exist three different behaviors for reinforcing particles such as brittle breakage, pressed into or flaking off the machined surface during machining. Generally, particles of small diameter are likely to be pressed into the matrix and the machining defects are relatively slight. However, particles of large diameter are likely to break or flake off, which makes surface integrity deteriorate.

Abstract: In this paper, frictional behaviors of tool, workpiece and chip in turning particulate reinforced iron-based composites were investigated. Experimental results reveal that in frictional process, the frictional coefficient decreases with the normal force increasing or with the reinforcement content decreasing. In turning process, the variation rule of such parameter is just similar to that of frictional process, but frictional force and average frictional coefficient on rake face are more than that of frictional process. Meanwhile, the frictional mechanism of cutting tool and material is also studied. It indicates that adhesion occurs on tool-chip interface. The intense scratching of reinforcing particulates blocks the formation of adhesion layer and makes the frictional coefficient decrease, on the other hand, it increases the sliding resistance of chip, which makes the frictional coefficient increase. Since the latter is dominant, the tool-chip frictional coefficient increases with the increase in reinforcing particulates.

Abstract: The wear characteristics and life of Al2O3/(W,Ti)C ceramic tool in turning NbCp-reinforced iron-based P/M composites was investigated. Experimental results indicate that cutting parameters have an influence on tool wear, among which cutting speed and depth of cut seem to be more prominent. The maximum flank wear rapidly increases as the increase in cutting speed and depth of cut. While, it increases gradually as the decrease in feed rate. Meanwhile, an empirical model of tool life is established, from which the influence of cutting speed and depth of cut on tool life is far greater than that of feed rate. Also from the empirical model, the preferable range of cutting parameters was obtained.

Abstract: This paper presents an investigation on the surface characteristics of NbC particulate reinforced iron-base composites after burnished by a ceramic ball burnishing apparatus. The effect of relative parameters on surface roughness, surface micro-hardness and depth of hardening layer of composites is studied. The results show that after burnishing process the surface roughness of composites samples sharply decreases, and the surface micro-hardness increases relatively, and the depth of hardening layer accesses 0.120.16mm. Also, material’s burnishing mechanism is discussed, and the process parameters are optimized.

Abstract: This paper presents an investigation on the surface roughness of burnished hypereutectic Al-Si alloy ¾ a widely used light-weight and wear resistant material in automobile, electric and aircraft industries. Based on the techniques of Taguchi, an orthogonal experiment plan with the analysis of variance (ANOVA) is performed and a second-order regressive mathematical model is established. Meanwhile, the influence of process parameters on surface roughness and its mechanism are discussed. From the experiments, it is found that burnishing process is effective to decrease surface roughness of hypereutectic Al-Si alloy components, in which, all input parameters have a significant effect on the surface roughness. To achieve a small surface roughness, the optimum process parameters are recommended.