Papers by Author: Ming Chen

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Authors: Dong Jin Zhang, Chen Wang, Gang Liu, Ming Chen
Abstract: As a typical difficult-to-cut material, the nickel-based superalloy GH4169 has been used in many kinds of aeronautical key structures and turbine components because of its high yield stress and anti-fatigue performance even in high temperature. In this paper, finite element method (FEM) is introduced to study the saw-tooth chip formation in detail. By the way of Lagrange approach, adiabatic shear band (ASB) is simulated and the chip forming mechanism is interpreted by adiabatic shearing theory via the comparison of two models, one of which has a failure criterion and another not. The comprehensive comparison and analysis of chip morphology between simulation and experiment are also presented in this paper.
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Authors: Jun Li Li, Ming Chen, Bin Rong
Abstract: The nickel-based superalloy GH80A has been widely used in kinds of aeronautical key structures because of its high yield stress and anti-fatigue performance at high temperature. However, it is also a typical difficult-to-cut material. In order to improve cutting process, kinds of methods have been applied to study cutting process including experimental approach and finite element method (FEM). In this paper, a comparison of chip formation is carried out between traditional Johnson-Cook (JC) model and Isotropic model. Besides, effects of tool rake angle and friction coefficient on chip formation are investigated by Isotropic model. FEM predicated results such as stress and cutting temperature are also analyzed. Relative turning tests are performed and comparison of chip morphology between FEM and experiment is carried out.
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Authors: Jun Li Li, Gang Liu, Dong Jin Zhang, Ming Chen
Abstract: The nickel-based superalloy GH80A is a typical difficult-to-cut material. It has been used in a good many kinds of aeronautical key structures because of its high yield stress and anti-fatigue performance at high temperature. But selection of cutting parameters in actual machining process mainly depends on experience and lacks of scientific utterance. In this paper, finite element method (FEM) was introduced to study the chip formation process when machining nickel-based superalloy GH80A. By the way of lagrangian finite element approach and material failure, adiabatic shear band (ASB) and periodic fracture were simulated with the help of former researchers’ studies on the material constitutive relation. Both the mechanism of adiabatic shearing phenomenon at primary shear zone and periodic crack in the free surface were analyzed, chip formations under different cutting parameters were got and compared carefully. The root cause of saw-tooth chip formation under different cutting speeds was discussed.
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Authors: Kun Xian Qiu, Ya Xing Bie, Sheng Qin, Qing Long An, Ming Chen
Abstract: High strength carbon fiber reinforced polymers (CFRP) with unidirectional laminate structure have gradually developed into major materials in load-bearing aerospace components, and the cutting demand of CFRP is increasing. In this work, orthogonal cutting tests were conducted on T700 high-strength CFRP laminates to get the mechanistic force model of special cutting tools. Also cutting force coefficients were obtained when cutting T700 high-strength CFRP laminates under different fiber orientations. Experimental results showed that the lowest cutting force was obtained when fiber orientation was between 120° and 150°.
704
Authors: Kun Xian Qiu, Sheng Qin, Chun Xin Ge, Ming Chen
Abstract: Both aluminum alloy and titanium alloy have been widely used in aerospace, aviation, military and automotive industries. This research presents a study of modified drills for drilling aluminum alloy and titanium alloy. The modified drills can be expected to reduce the cutting forces and torque. A set of experiment was carried on to investigate the performance of the modified drills. A method to quantitative assess of the reduction of the thrust force and torque was given below, and the calculation shows that the modified drills can reduce the thrust force and the torque by as high as 21.16% and 90.48%, respectively, as compared to the conventional drills under the same conditions.
163
Authors: Li Qiang Zhang, Yu Han Wang, Ming Chen
Abstract: In free-form surface machining, it is essential to optimize the feedrate in order to improve the machining efficiency. Conservative constant feedrate values have been mostly used since there was a lack of physical models and optimization tools for the machining processes. The overall goal of this research is the integration of geometric and mechanistic milling models for force prediction and feedrate scheduling for free-form surface machining. For each tool move a geometric model calculates the cutting geometry parameters, then a mechanistic model uses this information with the constraint force to calculate desired feedrates. The feedrate is written into the part program. When the integrated modeling approach was used, it was shown that the machining time can be decreased significantly along the tool path. Production time in machining propeller example was reduced to 35% compared to constant feedrate cases.
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Authors: H.Z. Zhang, Wei Wei Ming, Ming Chen, Bing Han, Bin Rong, Gang Liu, Yun Shan Zhang
Abstract: The α+2βtype Ti-5Al-4.75Mo-4.75V-1Cr-1Fe (TC18) is a very difficult machine material for its low thermal conductivity, low elastic modulus, and high chemical activity. So how to improve the machining efficiency and prolong the tool life have got more and more attentions. In this paper, wear mechanism and wear types of coated (TiN+TiAlN) carbide tool and uncoated carbide tool are presented when face milling the Ti-18 alloy under the same machining condition. The results showed that wear types of PVD coated tool are mainly adhesive, diffusion and crater wear, while the mainly failure mode of uncoated carbide tool is tipping. So it is more appropriate to select the PVD coated tool than uncoated tool in the milling TC18 alloy process.
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Authors: Yu Han Wang, Jing Chun Feng, Yu Hao Li, Ming Chen
Abstract: To alleviate the feed fluctuation and maintain a smooth feed in five-axis machining, this paper takes the following two constraints into account: (1) the machining dynamics, including the constraints of power, velocity and acceleration represented by upper bounds for each axis (2) the contour constraints of the tool path, including the linear distance of the segment and sharp corner at the segment junctions. With the analysis of these constraints, the optimal feed is derived and the corresponding adjusted interpolation algorithm is presented such that a smooth motion during the machining can be obtained. The presented algorithm is demonstrated by the simulation result.
873
Authors: Jing Chun Feng, Yu Hao Li, Yu Han Wang, Ming Chen
Abstract: To overcome the acceleration discontinuity and feed fluctuation of the conventional five-axis grinding interpolator, a jerk-limited acceleration is utilized and two aspects of constraints is taken into account: (1) the machining dynamics, including the constraints of power, velocity, acceleration and jerk represented by upper bounds for each axis (2) the contour constraints of linear segments, including the linear distance of the segment and sharp corner at the segment junctions. With the analysis of these constrains, the optimal feed for each segment and the joint feed at the segment junctions is derived. The corresponding adjusted interpolation algorithm with jerk-limited acceleration is presented such that a smooth motion during the machining can be maintained. The presented algorithm is demonstrated by the simulation result.
204
Authors: Wei Wei Ming, Qing Long An, Ming Chen
Abstract: Centerless grinding is a widely used manufacturing process in the mass production of precision parts. However, its productivity and precision is largely determined by the grinder set-up conditions, process stability and workpiece surface integrity. Grinding titanium alloys encounters difficulties due to its low thermal conductivity, high shear strength and extreme chemical reactivity. Therefore, the grindability of titanium alloy should be improved in order to increase the productivity for the sake of workpiece quality. In this paper, centerless grinding process was introduced initially and the research of impact factors on centerless grinding performance was reviewed. The problems occurred in the centerless grinding of titanium alloy were studied and optimum guidelines were proposed.
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