Papers by Author: Jun Wang

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Authors: Hai Bin Yu, Chuan Zhen Huang, Han Lian Liu, Bin Zou, Hong Tao Zhu, Jun Wang
Abstract: A 3D finite element polycrystalline microstructure model of ceramic tool materials is presented. Quasi-static crack propagation is modeled using the cohesive finite element method (CFEM) and the microstructure is represented by 3D Voronoi tessellation. The influences of cohesive parameters, the ratios of maximum traction of grain boundary to maximum traction of grain on the crack patterns of Al2O3 have been discussed. This study has demonstrated the capability of modeling 3D crack propagation of ceramic microstructure with CFEM and Voronoi tessellation model. It is found that the fracture mode is changed from intergranular to transgranular as the maximum traction of grain boundary is increased.
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Authors: Zhe Lv, Chuan Zhen Huang, Jun Wang, Hong Tao Zhu, Cui Lian Che
Abstract: Having an insight on the fluid field in AWJ machining is of important significance but the direct observation and measurement can be hardly implemented. Thus a 3D simulation of the fluid field in AWJ has been undertaken using FLUENT 6.3. The pressure and velocity distribution results on the impacted surface under different impact angle conditions are acquired and analyzed. The influence of the impact angle on the characteristics such as the symmetry of the distribution, position of the maximum value and the stagnation effect is highly concerned. In addition, an experiment under the similar conditions of the simulation is conducted and the results are compared with that of the simulation.
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Authors: Shao Chuan Feng, Chuan Zhen Huang, Jun Wang, Hong Tao Zhu, Peng Yao, Liang Wang
Abstract: Single crystal silicon carbide (SiC) is a new semiconductor material that has a great potential to be widely used. However, SiC is a kind of difficult-to-machine material due to its extreme hardness and brittleness. The present study investigated the machinability of single crystal SiC using dry laser and three different water-laser co-machining processes. The results indicate that using the hybrid laser-waterjet micro-machining to micro-groove single crystal SiC can derive the clean and straight edges and thermal damage-free grooves.
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Authors: Viboon Tangwarodomnukun, Jun Wang, Philip Mathew
Abstract: Laser micromachining has been widely used for decades to fabricate the micro- and submicro-component structures. However, thermal and physical damages are crucial issues associated with the process. Underwater laser ablation has been developed as a damage-free micro-ablation technique. In this paper, a comparison of the conventional dry and underwater laser micromachining of silicon is presented. It shows that the heat affected zone (HAZ) can be reduced significantly in the underwater laser process, though the material removal rate is reduced due to the energy loss by the water layer. The effects of pulse frequency, traverse speed and laser energy on the obtained kerf width, HAZ and cut surface quality are also analyzed and discussed.
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Authors: Jun Wang
Abstract: Increasing the performance of the abrasive waterjet (AWJ) cutting technology for engineering materials is the ultimate aim of research in this field. This paper presents a review on the studies using a controlled nozzle oscillation technique to increase the cutting performance of the AWJ cutting technology and the associated mechanisms primarily based on the work in the author’s laboratory. Primary attention is paid to the discussions of the depth of cut, the effect and selection of process parameters and the advantages by using this technique in both single- and multi-pass cutting modes.
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Authors: Fu Yuan Li, Jun Wang
Abstract: As a base of optimization of metal cutting, a new method of solution of optimization for single pass turning is proposed in this paper. There are three parts for this new method. Firstly, the optimal point must exist on the boundary of the feasible domain of the cutting conditions. Secondly, it is easy to add the processing of determining the boundary of feasible domain as new constraints. Thirdly, the local optimal point on every piece of line or curve of the boundary can be calculated, and finally the minimum of those local optimal points is the final optimal point. There are no local optimal points on the curves of constraints Tmin and Tmax except the intersection points. In addition, the trend of the objective function is affected by the rate . It is helpful to calculate the optimal point by computer. This approach provides a basic research on the affection of the statistics characteristic of the empirical functions used in this case.
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Authors: Thai Nguyen, King Pang, Jun Wang
Abstract: The erosion process in micro-machining of brittle glasses using a low pressure slurry jet is discussed. The process capability of the technique is assessed by examining the machined surface integrity in relation to fluid flow dynamics in micro-hole generations. The holes produced are characterised by a “W” shape in the cross section, while the surface morphology is distinguished by three zones associated with the fluid flow behaviour, i.e. a direct impact zone, a wavy zone and an accumulation zone. The surfaces appear to be smooth and without cracks, indicating a predominance of the ductile mode erosion process. With the increase of pressure, the erosion rates can be enhanced as a result of the expending of the accumulation zone while the outer diameter of the holes remains unchanged. This study shows that this technique can be used for micro-machining with high surface quality, and provides an essential understanding for further research in the avenue.
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Authors: Alireza Moridi, Jun Wang, Yasser M. Ali, Philip Mathew, Xiao Ping Li
Abstract: Owing to its various distinct advantages over the other machining technologies, abrasive jet machining has become a promising machining technology for brittle and hard-to-machine materials. An experimental study is presented on the micro-grooving of quartz crystals using an abrasive airjet. The effect of the various process parameters on the major machining performance measures are analysed to provide a deep understanding of this micro-machining process. Predictive models are then developed for quantitatively estimating the machining performance. The models are finally verified by an experiment. It shows that the model predictions are in good agreement with the experimental results under the corresponding conditions.
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Authors: J. Madadnia, Dinesh K. Shanmugam, Thai Nguyen, Jun Wang
Abstract: Current jet cutting systems experience severe nozzle erosion and associated maintenance and downtime costs. An experimental investigation was conducted to qualitatively and quantitatively analyse the generation of cavitation in a high pressure water jet cutting system, and to characterise cavitation induced accelerated surface erosion by slurries. The analysis of surface morphology indicates that the shearing induced by cavitation played a major role in the erosion process. The results promise a feasible solution to reduce nozzle wear, and to enhance material removal in the jet cutting process.
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Authors: Huai Zhong Li, Jun Wang
Abstract: nconel 718 is one of the most commercially important superalloys but with very poor machinability. It has a very high yield stress and a high tendency to adhesion and work-hardening. A recent trend of improving the machining processes of difficult-to-cut materials is to move towards dry cutting operations. This paper presents an experimental study of the cutting forces in high speed dry milling of Inconel 718 using a milling cutter with coated carbide inserts. It is found that the peak cutting forces increase with an increase in chip load in a nonlinear way, but cutting speed does not show a significant influence on the cutting force for the range of cutting speeds tested in this study.
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