Papers by Author: Wen Feng Ding

Abstract: High-speed grinding experiment of titanium matrix composites is carried out with cubic boron nitride (CBN) superabrasive wheels in this work. The heat transfer into the titanium matrix composites (TMCs) is discussed based on theoretical analysis. A calculation method of thermal ratio passing into the workpiece is represented. Results obtained show that high-speed grinding of PTMCs using vitrified CBN wheel has a greater thermal ratio passing into the workpiece than using electroplated CBN wheel. Moreover, a linear relationship is established between e_s and d_s^1/4a_p^-3/4v_w^-1/2.

Abstract: Electroplated profiled superabrasive grinding wheels which integrate both advantages of grinding and profile milling have been widely used in the machining process the wide chord hollow fan blade rabbets made of Ti-6Al-4V alloy. However, the employment of these tools has been impeded by drastic forces and thermal damage. In order to investigate the variation regularities of grinding forces and temperature with different machining parameters, experiments were carried out with single layer electroplated CBN grinding wheels. Grinding forces and temperature were measured and analyzed. Meanwhile, tool life and metallography of workpiece were studied. The results showed that higher spindle speed leads to lower forces and higher temperature. With the increase of feed rate and radial cutting depth, forces and temperature increase. Strong adherence of chips makes abrasives grits blunt which results in the increase of grinding forces after a great deal of tests. Metallographic structure of the machined workpiece is almost identical with the original sample.

Abstract: The present article deals with the surface topography during high speed grinding of particulate reinforced titanium matrix composites (PTMCs). Scanning electron microscopic images of the ground surface was analyzed. Combining the results presented in this paper, the following results could be summarized: (1) The reinforcing particles of PTMCs are removed by means of voids, pulled-out, fracture or crushed, and micro-cracks, which attributed to the plowing and shearing during high speed grinding. (2) The formation of the fracture pattern of PTMCs is formed due to the wear debris of the abrasion during high speed grinding.

Abstract: Grinding experiments were conducted using vitrified CBN wheel on particulate reinforced titanium-based matrix composites (PTMCs) and Ti-6Al-4V matrix. The issues discussed are grinding forces, surface roughness, and the formation of surface integrity. The main results are summarized as follows: (1) The grinding forces increase with the increasing workpiece speed and depth of cut during grinding PTMCs and Ti-6Al-4V materials. (2) Decreasing depth of cut properly contribute to obtaining finished surface with good surface during grinding of PTMCs using CBN wheel, but the workpiece speed has little influence on the surface roughness value of PTMCs. (3) The formation of surface integrity of PTMCs is due to the combined removal of the TiC and TiB reinforcements and the Ti-6Al-4V matrix.

Abstract: This article studies the effect of process parameters on the grindability of Ti-6Al-4V and particulate reinforced titanium matrix composites (PTMCs) comparatively, using the wheels of white alundum (WA) and cubic boron nitride (CBN) respectively. The processing variables, such as grinding force, grinding temperature, specific energy were investigated in detail. The results indicate that the grinding force and temperature with WA wheels were obviously larger than that of CBN wheels. The specific energy of Ti-6Al-4V and PTMCs decreased gradually with the increase in the maximum underformed chip thickness using the two different wheels.

Abstract: Particulate reinforced titanium matrix composites (PTMCs) are attracting increasingly attention in various engineering applications. In this paper, comparative grinding experiments of PTMCs were carried out using WA abrasive wheel and CBN abrasive wheel. The morphology of the ground surface was observed by scanning electron microscope. The main results are summarized as follows: (1) The damage of reinforcements in the PTMCs results from the plowing and shearing during grinding in the form of crater, micron gap, broken, coating and micron crack. (2) The formation of grinding chip is a function of the collaborate removal of reinforcements and matrix material. (3) The surface fracture pattern of PTMCs using WA wheel is to form the grinding chip through severe extrusion. While using CBN wheel, the abrasion due to the formation of the wear debris is the main surface fracture pattern of PTMCs.

Abstract: Cu-Sn-Ti filler alloy was applied as brazing material to join UcBN grains onto the steel matrix using three different brazing temperatures (880, 900 and 920°C). The microstructure and properties of the UcBN-filler-steel joint and the compressive strength of UcBN grains were investigated respectively by means of scanning electron microscopy and energy dispersive X-ray spectroscopy and compressive test. The microstructural studies revealed an intermetallic interlayer of type TiN, TiB and TiB₂ at the joint interface, which grew with increasing brazing temperatures. The compressive force of UcBN grains with a maximum value of 79.3N was found when the brazing temperature was 900°C for 8 min. The wear process of brazed UcBN grains was a process transforming from abrasion wear to micro fracture mutually.

Abstract: This paper mainly deals with the reconstruction and fractal analysis of wear topography of brazed polycrystalline cubic boron nitride (PcBN) grain in grinding process. On the basis of fractal analysis, the uncertainty in shape and complexity in wear mechanism are analyzed by means of the construction of micro fracture of PcBN grain after producing the brazed abrasive tool with PcBN grains and carrying out grinding test. The main results are summarized as follows: (1) Actual behavior of self-sharpening phenomenon due to micro fracture in the grinding process can be grasped and reconstructed using SEM and 3D video microscope. The reconstruction model can clearly express the complicated wear features and characteristics of the grain. (2) The fractal dimension can relate the performance of PcBN grain to its micro fracture, and then the self-sharpening phenomenon due to micro fracture can be evaluated quantitatively on the basis of fractal analysis.

Abstract: Metal-bonded cBN wheels with regular pores were fabricated using Cu-Sn-Ti alloy, cBN abrasive grains and alumina (Al2O3) bubble particles. Dressing experiments were carried out through rotary dressing method. Subsequently, grinding experiments were conducted on nickel-based superalloy GH4169. Comparative grinding performance was evaluated with vitrified cBN wheels in terms of grinding force and specific grinding energy. The results reveal that the pores in the working layer of the cBN wheels are exposed after rotary dressing. Compared to vitrified cBN wheels, grinding forces and specific grinding energy of the newly developed cBN wheels with regular pores are smaller.

Abstract: Fabrication experiments of porous composite-bonded CBN wheels were conducted using alumina (Al2O3) bubbles, CBN grains, Cu-Sn-Ti alloy and graphite particles. Influence of sintering parameters and porosity on the bending strength of the CBN composite blocks was measured and analyzed. Dressing and grinding practice was carried out. The results show that the optimal sintering temperature of the CBN composite blocks is 880°C. When the porosity of composite blocks is 8-45 %, the strength reaches 51-103 MPa. Regular shape of the pores is obtained after dressing. Both the grinding force and grinding temperature of the composite-bonded CBN wheel are lower than that of the vitrified one under the same grinding condition, which indicates the better grinding performance of the new-type porous composite-bonded CBN wheel.