Papers by Author: Hong Min Pen

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Authors: Cai Xu Yue, Xian Li Liu, Hong Min Pen, Jing Shu Hu, Xing Fa Zhao
Abstract: Tool wear plays an important part during cutting process, and wear loss has a close relationship with cutting condition, which affects machined surface mostly. In order to accomplish tool wear prediction in way of FEM, based on founding of cutting model under steady state, interrelated parameters needed for tool wear prediction, such as cutting temperature, contact pressure and raletive sliding velocity are extracted. By compiling Python subprogram and using Abaqus tool in hard cutting process PCBN tool wear is predicted, which provide foundation for optimizing cutting condition.
Authors: Jing Shu Hu, Hong Min Pen, Yu Wang, Tao Chen, Zhen Chang, Xian Li Liu
Abstract: Air cooling is a near dry machining method, which cools cutting area and evacuates chip using low temperature wind instead of cutting liquid. It can decrease tool wear, improve tool life, reduce cost and produce no chemical pollution. In this paper, air cooling system is established, in which vortex tube is used for cooling. Air cooling test was carried on, in which high hardness bear steel GCr15 is machined by PCBN tool. Experiment results indicated that cold air from vortex tube has a significant effect on cutting force, cutting temperature and chip formation process. Cutting force and cutting temperature were simulated using Marc. Change rules that analysis results indicated are in accordance with experiment results. This paper’s conclusions have a great reference value for the practical application of air cooling technology.
Authors: Tao Chen, Fu Gang Yan, Chun Ya Wu, Hong Min Pen, Xian Li Liu
Abstract: By cutting experiments, this paper investigates the effect of various chamfer widths and chamfer angles on cutting force, cutting temperature, and chip morphology when hardened steel GCr15(HRC60+2) is machined with PCBN tools. The research results indicate that with the enlargement of chamfer angle both cutting temperature and main cutting force increase gradually, and especially, radial force increases more significantly. In addition, it is shown that as chamfer width increases both cutting force and cutting temperature rise. The analytical results of chips derived from cutting experiments reveal that chamfer angle being 20º, chips are the thickest and less serrated. Furthermore, chip thickness diminishes gradually with the increment of chamfer width.
Authors: Xian Li Liu, Hong Min Pen, Tao Chen, Fu Gang Yan, Yu Wang, Jing Shu Hu
Abstract: Through combining turning experiments and FE simulations, this paper studied the effects of force, temperature and residual stress of machined surface on high speed hard turning GCr15 bearing steel hardened to HRC60-62 with three kinds of ordinary edge preparation (sharp-edge, hone and chamfer). The experiment and simulation results indicated that the diathermanous proportion of chamfered edge preparation to tool and machined surface is less, and this distribution of cutting temperatures is useful for tool life and machined surface quality. The simulation results showed that cutting force had a descending tendency with increasing of cutting speed, which is in accordance with the change rules of machining general rigidity material, and it proved that FE simulations have good precision. The simulation results of residual stress of machined surface showed that residual tensile stress existed in machined surface using both honed and chamfered tools, and a highest compressive stress (about -200MPa) existed among 150-200μm of the depth into the workpiece surface. The difference was that the depth of superficial harden layer with honed tools is larger than that with chamfered tools.
Authors: Yu Wang, Peng Wang, Hong Min Pen, Yu Fu Li, Xian Li Liu
Abstract: Experiment of hard cutting GCr15 with PCBN cutting tools, the influence of tool’s inclination angle and cutting parameters (cutting speed and feed speed) on cutting forces and cutting temperature are studied. A three-dimensional finite elements model using the commercial software Deform 3D 5.03 is developed. The friction between the tool and the chip is assumed to follow a modified Coulomb friction law and the adaptive remeshing technique is using for the formation of chip. The workpiece material property is a function of temperature, strain, and strain rate in the primary and secondary shear zones. Finite element method is used to simulate three-dimensional precision cutting, including orthogonal cutting and oblique cutting. The cutting forces and back forces are slightly changed by tool’s inclination angle. However, in high cutting speed, the cutting force decrease as the tool’s inclination angle increase, while the cutting temperature increase as the tool’s inclination angle increase. The simulation results are compared with experimentally measured data and found to be in good agreement to some extent.
Authors: Ying Chun Liang, Hong Min Pen, Qing Shun Bai, Xing Lei Hu, Zhi Guo Wang
Abstract: In order to investigate the mechanical properties of single crystal Cu nanorod with preset defects, the multiscale unixial tension simulation models of nanorods with two different crystallographic orientations are established. In two orientations, the dislocations are emitted firstly from the notch tip. The results show that the defect evolution, stress-strain curves and train energy vary with different crystallographic orientations. In setup, the deformation is ductile mode and it is fracture fashion in the setup.
Authors: Ying Chun Liang, Xing Lei Hu, Jia Xuan Chen, Hong Min Pen
Abstract: Nanometric uniaxial tension tests of single crystal copper nanorod are simulated using multiscale simulation method, which has combined molecular dynamics (MD) and finite element method (FEM). New tension models of nanorod are constructed. Tension processes of ideal nanorod without notches and that with notches are performed to analyze their mechanical properties. Deformation mechanism of tension process is discussed in detail. Yield strength and elastic modulus are calculated according to the obtained stress-strain curves. Finally, the results show that the notches have obvious influence on the mechanical properties of copper nanorod. Due to the existence of notches, the section area of single crystal nanorod decreases by 40%; however, the yield strength and elastic modulus decreases by 39.0% and 10.2% respectively in our simulations. This research is helpful for identifying the mechanical properties of single crystal copper nanorod, and for understanding the deformation mechanism of tension process of nanorod.
Authors: Ying Chun Liang, Hong Min Pen, Qing Shun Bai
Abstract: A multiscale simulation model was built to study the nanometric cutting process of single crystal copper. This multiscale model distinctly reduces the degree of freedom of the whole system compared with full atomistic simulations. Through analyzing the fluctuations of tangential cutting force and strain energy with cutting distance, we confirm that the deformation mechanism of single crystal copper is plastic deformation caused by generation and evolution dislocation. The highest compressive stress locates in shear zone and highest tensile stress locates in the machined surface and subsurface. Simulation results show that there exists a high value of stress around dislocations, which reveals the local high value of stress is the main reason for the generation and evolution of dislocations in the workpiece material.
Authors: Hong Min Pen, Qing Shun Bai, Ying Chun Liang
Abstract: Quasicontinuum simulation of nanometric cutting was conducted on single crystal copper to investigate the effect of crystal orientation and cutting direction on nature of deformation of this material. The model reduces the degrees of freedom in simulations of nanometric cutting process without sacrificing important physics. The simulation results show the crystal orientation and cutting direction have a significant effect on the nature of deformation of nanometric cutting process. In addition, the variations of strain energy of workpiece atoms in different crystal set-ups are investigated.
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