Advanced Materials Research Vol. 426

Abstract: In order to control chatter in machining of thin-walled workpieces, the dynamic model of milling od thin-walled workpiece is analyzed based on considering the flexibility of the workpiece and the machine. In high speed milling of 2A12 aluminum alloy, the compensation method based on the modification of inertia effect is proposed and accurate cutting force coefficients are obtained. The machining system is divided into “spindle-cutter” and “workpiece-fixture” two subsystems and the modal parameters of two subsystems are acquired via modal analysis experiments. A method for obtaining the stability lobes is presented by considering the relative movement of both subsystems. Finally, the stability lobes for high speed milling of 2A12 thin-walled workpiece are obtained and compared between considering three kind of modal parameters. The results are verified against cutting tests.

Abstract: The object of this paper is to experimentally investigate the effects of ultrasonic vibration on the roughness of surface produced by the side cutting edge of an end milling cutter. Two respective surface roughness models for conventional milling (CM) and ultrasonic vibration assisted milling (UVAM) were proposed using experimental data. RSM and ANOVA were used for analysis. As a result, it is found that the surface roughness of vertical side surface of slot improves obviously after applying ultrasonic vibration. The result of ANOVA indicated that the target surface roughness depends on the combined action of several key machining parameters in UVAM, and therefore their choosing and optimizing is very important to achieving small surface roughness.

Abstract: A viscometer based on velocity attenuation is presented. It is used to measure viscosity of liquid at an arbitrary velocity. Structure of the viscometer is designed. A motor designed specially called Series-Motor is used as driven motor of the viscometer to keep the flow stability of test liquid. A solid rotor motor is adapted to reduce the cogging effect. Pressure-feed air bearing is adapted as support to minimize the resistance torque. Simulation is made in MATLAB. Results show that Series-Motor reduces the resistance torque besides the viscous torque and it provides slow speed motor to keep the flow stability.

Abstract: The influences of various processes of cryogenic treatment, optimization of parameters and prolongation the life of the high speed steel taps have been studied in the paper. Taking W9Mo3Cr4V for an example, the influences of temperature raising and decreasing rate, cryogenic treatment temperature and holding time, times for treatment, temper process and sequence of cryogenic treatment are discussed. Two kinds of cryogenic treatment process that one is before temper and the other is after it are put forward. Process flow is designed according to the process suitability and economy, the reported research results and existent problem. The results show that the life is prolonged after cryogenic treatment and the life is longer if the cryogenic treatment is carried out before tempering. To different material, the quantity of prolonging is different. To 30CrMnTi, 1.43 times of life of the tap is prolonged if the cryogenic treatment is arranged before tempering and only 61% is prolonged after tempering. To 1Cr18Ni9Ti, 1.08 times is prolonged before tempering and only 46% is prolonged after tempering. To 5CrMnMo, 1.65 times is prolonged before tempering and only 89% is prolonged after tempering. Research indicates that after cryogenic treatment, the harder the material is, the better the cutting is.

Abstract: Surface integrity is a significant issue concerning machined part quality, especially for aluminum milling process in aerospace manufacturing. This paper gave an intensive analysis on surface integrity in high speed milling of 7075-T651 aluminum alloy, and the relationships of surface topography, surface roughness and residual stress profile with cutting speed at high levels were discussed and some basic aspects concerning surface integrity in high speed end milling of aluminum parts were presented.

Abstract: The molecular dynamics simulation and experimental study of residual stress were carried out on micro/nano scale. The relationship between residual stress and hardness was researched by the simulation for nano-indentation process of single crystal cooper. It was showed that load-displacement curve above reference state when single crystal copper surface exists compressive residual stress,and the existence of tensile residual stress is below reference state. Then the phenomenon was analyzed and gave a reasonable explanation. In addition, the regression analysis of relationship between micro/nano-hardness and residual stress was carried out.

Abstract: Aiming at the problems of composites of anisotropic, poor in dimensional and uneven temperature field in the designing of composite tool in autoclave, the techniques of designing the composite tool of aircraft components were constructed, involving in the following aspects: Taking advantage of design flexibility of composites, the thermal expansion coefficient between the moulding board and composite components matched. By analyzing the cure process curve of fiber-reinforced composites, the result that the crisis point without stress between component and tool, which the shape of composite component decided was concluded. By the temperature field analysis, and contrasted with the experimental results, the maximum difference was 4.95°C，after analysis, optimized the structure of the tool, obtaining the relatively uniform temperature field of the board.

Abstract: Dual meshing silent chain mechanism can reduce the polygon action. In order to realize the conjugate meshing, the sprocket of the dual meshing silent chain mechanism is supposed to be an involute sprocket with a large pressure angle and negative modifying coefficient. Through the investigation on the transmission progress of dual meshing silent chain mechanism, the movement trajectory of the chain link and the sprocket is achieved. The inside tooth profile of link is interfered with the hypothetical sprocket tooth profile. So the supposed involute sprocket is modified. The result shows that the sprocket with the conjugate meshing and no interference is the addendum modifying sprocket with a large pressure angle and a large negative modifying coefficient.

Abstract: As a typical high strength material, titanium alloy Ti-6Al-2Sn-4Zr- 2Mo-0.1Si (TA19) is used to manufacturing the compressor power-brake of aircraft engine and the aircraft skin. All the machining experiments were carried out on a CNC-milling center under the stable conditions of cutting speed, feed rate, and depth of cut. The performance and wear mechanisms of coated- and uncoated carbide tools have been investigated in this paper to evaluate the machinability of TA19 in face milling. The three tools used were PVD-TiN+TiAlN, CVD-TiN+Al2O3+TiCN and uncoated carbide inserts. The results indicated that PVD coating had the best performance than other tool materials in milling titanium alloy TA19, and the cutting force and the wear value were the smallest than that for CVD-coated and uncoated tools. The failure types of PVD-, CVD- and uncoated inserts were the crater wear and micro tipping; the crater wear and tipping; tipping. Abrasive wear and adherent wear were the predominant mechanism of PVD-TiN+TiAlN carbide insert in face milling TA19 alloy. For CVD- and uncoated carbide, adherent wear was predominant.

Abstract: PCBN tools were used for the turning of TC4. The cutting behavior and wear mechanisms were examined by means of the microscope, SEM and EDS analyses. The results have shown that ,the forms of the tool wear are mainly the rake face wear, flank wear, tip damage ,flaking and tipping; while the wear mechanism are mainly adhesion wear ,diffusion wear, machine wear and oxidation wear.