Papers by Author: Hong Zhi Zhang

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Authors: Chun Yang Zhao, Hong Zhi Zhang, Li Jun Yang, Yang Wang
Abstract: In laser induced thermal crack propagation (LITP) cutting brittle materials, according to the laser absorption ability, materials are divided into the body absorption and surface absorption. This paper indicates the fracture mechanism of LITP cutting surface absorption brittle materials. The crack extension appears in the lower surface firstly in this stress distribution state, then the crack extends to the upper surface and the laser scanning direction with the LITP cutting. The stress field of cutting ZrO2 ceramic is studied by finite element software ANSYS. The crack propagation process of cutting silicon wafer is studied by finite element software ABAQUS. According to the fracture mechanism, the curve cutting the ZrO2 ceramic experiments and the cooling lower surface cutting the silicon wafer experiments are carried out in this paper. Optical microscope and laser scan confocal microscope (LSCM) photographs of the curve path the ZrO2 ceramic and separation surface cutting the silicon wafer are obtained to examine the cutting quality. The quality of the curve path is very good. The quality of the separation surface in cutting the silicon wafer with the cooling lower surface is better than conventional environment.
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Authors: Xue Feng Wu, Hong Zhi Zhang, Yang Wang
Abstract: Laser assisted turning is an effective method machining difficult-to-machine materials such as ceramics, which uses a high power laser to focally heat a workpiece prior to material removal with a traditional cutting tool. A transient, three-dimensional heat transfer model was developed for laser assisted turning of silicon nitride using Finite Element Method to understand the thermal process of laser heating and to optimize the operating parameters. A laser assisted turning experiment system was set up to investigate the thermal conditions and cutting process of laser assisted turning of sintered silicon nitride and the experiments were conducted on the system using selected parameters. Effects of cutting parameters on cutting forces and specific cutting energy were investigated. Forces on the chip and SEM micrographs of chip morphology were studied to discuss the material removal mechanism of laser assisted turning of silicon nitride. Tool wear, surface roughness of the machined surface and the quality of subsurface were investigated. The results showed that the heat transfer model could be used to optimize the cutting parameters and laser assisted turning method could increase the machining efficiency while maintaining machining quality and reasonable levels of tool wear. A method of optimizing LAM based on the thermal model was presented.
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Authors: Hong Zhi Zhang, Ye Si Sang, Jian Ping Wang
Abstract: With the rise of green trade, developed countries and development cooperation between China and have to CDM to reduce and control excessive consumption of resources and environmental pollution problems. In this paper, the use of CDM in China to promote green trade development status of introduction, more comprehensive, in-depth analysis of the use of CDM to promote China's trade problems in the development of green and causes, and to make China the use of CDM to promote the development of effective countermeasures green trade.
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Authors: Xue Feng Wu, Hong Zhi Zhang, Yang Wang, Chao Xie
Abstract: Laser assisted machining (LAM) is an effective method machining difficult-to-machine materials such as ceramics which uses a high power laser to focally heat a workpiece prior to material removal with a traditional cutting tool. A laser assisted machining experiment system was set up and a transient, three-dimensional heat transfer model was developed for LAM of silicon nitride using Finite Element Method to understand the thermal process of laser heating. The model was based on temperature-dependent thermophysical properties and the heat generated was neglected due to cutting which is assumed to be small compared to the heat generated by laser heating. The experiments were carried out to investigate the effects of operating parameters, such as laser power, laser translational speed, rotational speed, laser beam diameter and preheating time on temperature distribution. An infrared radiation thermometer was used to measure the surface temperature histories and the experimental results were in good agreement with predictions. The laser power and laser translational speed have the greatest influence on the temperature.
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