Papers by Author: Gao Feng Zhang

Abstract: To investigate the distribution of cutting temperature for surface cutting of nanastructured WC/12Co coating used the PDC cutter, according to machining properties of WC/12Co coating and working conditions, on the basis of the theory of thermal equilibrium of moving thermal source, the mathematical model of temperature field was established through reasonable hypothesis. Simulations were performed for the temperature distribution on the surface and inside the WC/12Co coating specimen using finite element method. And experiment of surface temperature of WC/12Co coating used the PDC cutter was carried out. The finite element simulation results were in good agreement with the experiment data, which verified the validation and capability of the finite element model.

Abstract: A novel diamond fibers cutter was proposed in this paper for machining of advanced materials. The fibers cutter was prepared by artificially distributing and orientating a large number of diamond fibers, which were prepared by cutting polycrystalline diamond into size of 0.4mm*0.6mm*10mm using Nd:YAG laser, and then lapped on a lapping machine to form sharpened cutting edges. To investigate the machining mechanism of the diamond fibers cutter, an experiment on machining of aluminum alloy reinforced by SiC particles and nano-structured WC/Co coating was conducted in this paper. Based on the surface observation and the cutting force analysis, it could be found that the diamond fibers cutter combined the advantages of conventional wheels and cutting tools, and was fit for machining of both brittle materials and soft materials.

Abstract: Based on the theory of metal pre-stressing machining, the method of pre-stressing suitable for ceramic materials machining was presented. Using the cluster method, the discrete element method (DEM) model of ceramic materials machining was established. The DEM simulations of cutting process of SiC ceramic under different machining parameters were carried out by orthogonal test design method, and the effects of machining parameters on the number of surface cracks and maximum crack depth after processing were also analyzed. The results showed that the tool edge radius influenced greatly on the number of surface cracks, while the pre-stress influenced greatly on the maximum crack depth.

Abstract: In this paper, the technology of pre-stressed machining suitable for ceramic materials was presented. Using the cluster method, the discrete element method (DEM) model of SiC ceramic was established to simulate the crack’s initiation and propagation in cutting processes with different pre-stress value. The scratching tests were carried out to confirm the validity of simulation. Both the DEM simulation and the experimental investigation showed that: with the increasing of pre-stress, the number of radial cracks reduced and the transverse cracks replaced the radial cracks to some extent, and also caused the material removal in the form of smaller fragments. Using pre-stressed machining can decrease the machining damage and improve the surface quality, and further prove that using DEM to simulate the machining process of ceramic materials was feasible.

Abstract: The random nature of the abrasive geometries and their distribution in a grinding wheel results in high specific grinding energy and temperature rise, large grinding forces and large deflection in the grinding system. To overcome the shortcomings encountered in grinding, it is necessary to design a new grinding wheel that is structured in controlled abrasive geometries with preferred spatial positioning and orientation. This paper deals with an experimental research of single fibrous-abrasive grinding of a nanostructured WC/12Co Coating. Prepared by the laser cutting of polycrystalline diamond compact (PDC), the single fibrous-abrasive has the dimensions of 0.3×0.6×10mm. The paper reports the research findings on normal and tangential grinding forces in terms of depth of cut and feed rate and discusses the material removal mechanism of nanostructured WC/12Co Coating ground by fibrous abrasive.

Abstract: The objective of this study is to experimentally investigate the effect of reinforced SiC particles on the machining of Aluminum/SiC composite (15% volume ratio of SiC particles with average grain size 15m). Aluminum/SiC composite and aluminum metal were milled by a tungsten carbide endmill in this study. Based on the surface observation and surface roughness inspection, it is found that the machining parameters of Aluminum/SiC composite have optimum values, and that the surface roughness of aluminum/SiC composite is smaller than that of aluminum metal. when feedrate and depth of cut are smaller than limited values, satisfactory surface finish can be attainable, however, as the depth of cut and feedrate increases, the microcracks are first initiated at the interface of SiC particles and aluminum matrix, and then periodically macrocracks are formed on the machined surface, The damage mechanism during the machining of aluminum/SiC are discussed in this paper.

Abstract: The mechanical models formed by packed circular discrete elements were used to investigate the mechanical properties of Si3N4. In these models, the distribution of elements is random in the specified region, and the average radius of elements is 6m. The main mechanical properties investigated here are Young’s modulus, compressive strength, Poisson’s ratio, fracture toughness and bending strength. Some numerical simulation analysis of the size effect of the mechanical properties in these discrete element models were carried out. The simulation results suggest that there is no obvious size effect for Young’s modulus, compressive strength and Poisson’s ratio in these discrete element models. However, for bending strength, when the number of elements in model is less than about 9000, there exists obvious size effect, with the increasing of the number of the elements, the size effect will become less and less until disappeared. The value of fracture toughness decreases with the increasing of the number of the model elements. The classical continuum fracture mechanics model about material fracture under tensile stress is also established by discrete element method. The simulation results are just the same as the simulation results of single edge notched bending (SENB) and the experimental values reported in other literatures. The results provide a more reliable foundation for the application of DEM in simulating the mechanical behaviors of advance ceramics.