Papers by Author: Han Lian Liu

Abstract: The single-asperity friction of polished single crystal silicon using a cone with a spherical apex tip was quantitatively studied concerning the influence of normal load and scratching cycles. Specific friction equations were presented and the interfacial friction equations were determined by fitting the experiment data obtained in the scratching tests. The influence of different scratch conditions to both the interfacial fiction and the plowing friction was analyzed. This paper aims to understand the mechanisms of friction and material removal of single crystal silicon in micro and nanocutting or polishing.

Abstract: The milling of AISI 321 stainless steel which has wide engineering applications particularly in automobile, aerospace and medicine is of great importance especially in the conditions where high surface quality is required. In this paper, L16 orthogonal array design of experiments was adopted to evaluate the machinability of AISI 321 stainless steel with coated cemented carbide tools under finish dry milling conditions, and the influence of cutting speed ( V ), feed rate ( f ) and depth of cut ( a_p ) on cutting force, surface roughness and tool wear was analysed. The experimental results revealed that the cutting force decreased with an increase in the cutting speed and increased with an increase in the feed rate or the depth of cut. The tool wear was affected significantly by the cutting speed and the depth of cut, while the effect of the feed rate on the tool wear was insignificant. With the cutting speed increased up to 160 m/min, a decreasing tendency in the surface roughness was observed, but when the cutting speed was further increased, the surface roughness increased. The effect of the feed rate and the depth of cut on the surface roughness was slight.

Abstract: Gear grinding is expensive and difficult to research due to its complex kinematics and meshing theory. In the paper, a simplified method based on the meshing model of spiral bevel gear system is presented. With the relative speed and normal curvature of tooth surfaces and grinding wheels on meshing point deduced from differential geometry theory and grinding parameters, the spiral bevel gear grinding can be simplified to fundamental grinding process like surface, cylindrical and internal grinding, which may be utilized to perform experimental investigation on mechanism of gear grinding.

Abstract: In this work, two kinds of Al₂O₃-TiC-TiN ceramic cutting tools (AC2U and AC2UN2) were developed by hot-pressing sintering techniques. The mechanical properties were measured and the cutting performance was investigated. The workpiece used in the cutting experiment was quenched carbon tool steel T10A, and the tool material for comparison was LT55. The wear resistance and the main wear patterns of the ceramic tools were analyzed at the high speed of 300m/min. The results indicated that the novel Al₂O₃-TiC-TiN ceramic cutting tools showed better cutting performance than LT55, and AC2UN2 was better suitable for machining quenched T10A. When the cutting condition was v=300m/min, f=0.1mm/r and a_p=0.1mm, the adhesion wear and abrasive wear of the novel ceramic tools were slighter than those of LT55, the diffusion wear resistance of AC2U was better and the oxidation resistance of AC2UN2 was better.

Abstract: In order to fulfil the actual request of machining process to the machining database system, according to the characteristics and requirements of machining process, the fuzzy technology and case-based reasoning method were introduced to the design of machining database system. The reasoning process of case-based reasoning method and three main aspects of the fuzzy model were discussed. The match of cases and fuzzy comprehensive evaluation were introduced. The function of high-speed machining database was analyzed and the structure of the database was described. The users can use the database to acquire the overall solutions about high-speed machining.

Abstract: The cutting performance, failure mechanisms and reliability of Al₂O₃/TiC micro-nanocomposite ceramic tools with different geometry parameters in continuous machining of austenitic stainless steel were studied. The results showed that the largest metal removal amount was got at the cutting speed of 80 m/min, the feed rate of 0.15 mm/r and the cutting depth of 0.1 mm. The failure modes of the tool with small chamfering width and corner radius were mainly cutting edge fracture and tool materials peeling off, which was due to the subcritical crack growth. The life of the tool with small chamfering width and corner radius well followed the Gamma distribution.

Abstract: 17-4PH stainless steel is a widely used martensitic precipitation hardening stainless steel, and it is a typical difficult-to-cut material. Residual stress is an important part of the surface integrity. In this paper, superficial residual stress tests of face-milling the 17-4PH stainless steel were carried out at 0.1~0.3 mm/tooth with TiAlN coated carbide inserts. The effects of feed rate on the superficial residual stresses at various cutting speeds were studied. It was found that the residual stresses on the machined surface were very sensitive to the feed rate. The superficial residual stresses at the directions of parallel to and normal to the feed direction both remained compressive and changed obviously in higher compressive direction along with the feed rate. The burnishing effect determined by the cutting force was found to be the primary reason of the residual compressive stresses on the machined surface. The suitable cutting parameters were recommended according to the superficial residual stresses.

Abstract: Micro milling is most flexible to create 3D features for application. However, how to design and fabrication of high precision micro milling tools are one of big challenges for mechanical micro milling. Commercially available micro milling tools are usually simply made from downsizing of macro milling tools, which have negative impact on milling performance. Therefore, in this paper, firstly, various structural of micro milling tools were optimized with abaqus that investigated stress and strain under certain static load on the cutting edges. Then, results showed the minimum stress and strain was a micro hexagonal end mill. Finally, a Ti (C₇N₃) cermet micro hexagonal end mill with a radius of 0.5mm was fabricated by wire electrical discharge machining, and the evaluation experiments for the hexagonal mill have been processed on a micro milling centre.

Abstract: Inconel 718 alloy is a typical difficult-to-cut material and widely used in the aerospace industry. Finite element simulation is an efficient method to investigate the cutting process, whereby a work material constitutive model plays an important role. In this paper, finite element simulation of the cutting process for Inconel 718 alloy using a new material constitutive model for high strain rates is presented. The effect of tool cutting edge radius on the cutting forces and temperature is then investigated with a view to facilitate cutting tool design. It is found that as the cutting edge radius increases, the characteristics of tool-work friction and the material removal mechanisms change, resulting in variation in cutting forces and temperature. It is shown that a smaller cutting edge radius is preferred to reduce the cutting forces and cutting temperature.

Abstract: A new developed TiN-TiB₂ ceramic cutting tool material (marked as TBN5) with high comprehensive mechanical properties was fabricated by the in-situ integration synthesis process. The cutting performance of TBN5 tool in continuously turning the austenitic stainless steel 1Cr18Ni9Ti was experimentally investigated; the failure modes and failure mechanisms of the cutting tool TBN5 were analyzed combined with its mechanical properties. Aiming at the materials removal amount, the optimal cutting parameters of TBN5 tool in turning 1Cr18Ni9Ti were firstly obtained by the orthogonal tests; and then with this cutting parameters, the cutting performance of TBN5 compared to the commercial tools LT55 and SG4 was studied. The results showed that the advanced tool TBN5 could get longer tool life than LT55 and SG4; the main failure modes of TBN5 were flank wear, breakage and the flaking of main cutting edge. The scope of its flaking was smaller and diffusion wear was not obvious, which was related to the higher fracture toughness and the higher thermal conductivity of TBN5.