Manufacturing Science and Engineering I

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Authors: Gang Yi Cai, Xiao Xia Liu
Abstract: Finite element simulation of the effects of mould angle on the equal channel angular pressing (ECAP) for Al-Zn-Mg-Cu aluminum alloy was investigated by using DEFORM-3D program. The results show that the work load ascended with the increasing of the mould angle and was divided into five stages including rapid increasing stage, steady stage, rapid increasing stage, steady stage and rapid drop stage. When the angle decreased from 150° to 90°, the maximum load increased by 2.87 times and the energy consuming increased by 2.36 times. In addition, with the decreasing of mould angle, the average effective strain increased after single extrusion, while the degree of effective strain uniformity of the sample decreased. There were greater strain grads between inner and surface part. As mentioned above, large angle mould should be adopted on ECAP for Al-Zn-Mg-Cu aluminum alloy in order to ensure extrusion smoothly and attain homogeneous fine grain.
Authors: Kun Chen, Yi Tao Yang, Ke Jia Liu, Guang Jie Shao
Abstract: Simulation method of void defect evolvement during the forging of steel ingot was determined by comparing simulated and experimental results of void closure in the cylinder specimens during forging. Calculation results of long and short void defect evolvement during forging indicated that effective strain required for void closure was induced by the integration of stress. The closure of tetrahedral void is the most difficult with the maximal values of critical reduction on void closure during forging, on the basis of which, theory basis is provided for making forging process.
Authors: Jun Wang, Bing Xing Wang, Wen Feng Huo, Xiao Lin Chen
Abstract: For the purpose of realizing high-precision control of temperature profile during laminar cooling process after hot rolling, the characters of temperature variation inside hot plate are analyzed with the finite element method. The temperature properties of the plate, including the temperature drop, the temperature difference in the plate thickness direction, the cooling rate, and the red-back process, is researched under different cooling conditions. The law of the temperature properties variation with the plate thickness and the flow rate is obtained.
Authors: Jun Wang, Chun Li Jia, Zhong Zhao, Zhi Jie Jiao, Jian Ping Wang
Abstract: Rolling force model is the core of all the mathematical models of plate for rolling process, but the accuracy of traditional rolling force model is not high enough in application, so in this study the rolling force model of plate is researched and improved. The effects of different physical conditions on resistance of deformation are decoupled, and the formula acquired is practical. While the composition, Nb is used to calculate residual strain. At the same time, the self-learning method, which is based on the thickness layer is applied. The on-line application results show that the predictive error between force model calculated and measured can be controlled at less than 9% and 80% of the passes can be controlled within 5%.
Authors: Yuan De Yin, Sheng Zhi Li, Jie Xu, Yang Hua Li, Gong Ming Long, Pi An Deng
Abstract: With the aid of commercial finite element analysis software MSC. Superform, the high pressure boiler steel tube continuous rolling process with 6-stand semi-floating mandrel is simulated, and the distribution characteristic of transverse wall thickness is analyzed. It indicates that it presents “M” shape that the distribution of transverse wall thickness of hollow tube along one-fourth groove periphery. Transverse wall thicknesses have low values at the top, the bottom and sidewall 45 degree or so of groove, and they have high values at the sidewall 23 degree and 67 degree or so of groove. Then the improved measure is put forward on the basis of analyzing the causes responsible for transverse wall thickness. By the comparison of the simulation results, they have been improved obviously that transverse wall thickness precision and real roundness of rolled hollow tube using the improved measure.
Authors: Yu Lan Tang, Qiang Liu, Yu Hou Wu, Ke Zhang
Abstract: A three-dimensional model of molecular dynamics (MD) was employed to study the nanometric cutting mechanism of monocrystalline copper. The model included the utilization of the Morse potential function to simulate the interatomic force. By analyses of the snapshots of the various stages of the nanometric cutting process, the generation and propagation of the dislocations around the tool are observed. Some of these dislocations are observed to travel through the entire depth of the workpiece. Those that could most escape completely through the machined surface due to elastic recovery were found to introduce atom step on the machined surface. By analyses of the cutting forces during the entire nanometric cutting process, significant fluctuations are observed in the cutting force curves. The stress distribution plots of the various stages of the nanometric cutting process show that the mechanism of chip formation is significantly different from the conventional shear ahead of the tool in the case of a polycrystalline material. Most atoms ahead of tool are compressed, but forces of one or two layers atoms contact the cutting tool are tensile. With the chip formation, a small tensile zone ahead of tool generates in the compression zone and moves with the tool.
Authors: Bing Yan, Chao Hui Xu, Wei Wang
Abstract: The machining characteristics of hardened still for mould and die greatly affect the accuracy and productivity in industry. The physical modeling and simulation of ball end milling is investigated in this paper. The influence of cutting speed to the cutting mechanism in high speed cutting is taken into account and the momentum force of chip is introduced into the model. By analyzing the shape of the chips the relationship between the cutting speed and shear angle is obtained. The model has been tested on 718HH, with appropriate Seco tools. The validation shows that the adjustment between the model and the real force is adequate, both in shape and magnitude.
Authors: Ping Ma, Cheng Xiang Liao, Zhen Hui Chen, Gong Zhen
Abstract: In high speed machining, the feed drives with high velocity and high acceleration are necessary to make full use of the capacities of the high speed motorized spindles. The linear motor feed drive eliminates any mid- transmitting mechanism, which cause achieved the high acceleration. In this paper, the GD-Ⅲ linear induction motor feed drive is introduced, and its controller is modeled and its stiffness has been investigated with simulation program MATLAB & SIMULINK. The influence of the parameters of the controller on the dynamic performance has also been analyzed. The simulation shows that the positional loop proportional gain kv, velocity proportional gain kp, velocity loop integral time constant Tn and the current loop proportional gain kpi have great influence on the dynamics of the linear motor feed drive. In the end, the simulation is verified by the experimental results.
Authors: Qing Tan, Kai Wang, Yi Min Xia, Kui Zhang, Zi Jun Xu
Abstract: In order to analyse the rock breakage process of double-edge ball tooth hob cutter and get the related curve of intrusive force and invasion depth, the numerical simulation model of double-edge ball tooth hob cutter is accurately established. In the process of interaction between hob cutter and rock mass, the material model is also established, the mechanism of rock fragmentation is carefully researched, the elastic-plastic deformation is seriously studied. Finally, we design an experiment which has a good consistency with the simulation analysis.
Authors: Li Da Zhu, Gang Li, Wan Shan Wang
Abstract: Aiming at the characteristics of structure and control of three-links hybrid machine tool, the interpolation strategy of CNC system is proposed in this paper. Coarse interpolation in workspace and fine interpolation in joint-space are expatiated. The trajectory points are transformed into discrete points by coarse interpolation mapping from workspace to joint-space. At the same time, the plans of trajectory, velocity and acceleration of discrete points in workspace are got, and then joint discrete points are realized by joint fitting smooth function. In order to meet the design demand and enhance effectively interpolation precision, the five polynomial interpolations will be thinning discrete points, and geometric locus will be very smooth.

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