Papers by Author: Philip Mathew

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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: 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: Philip Mathew
Abstract: A variable flow stress machining theory is described where it is used to predict the cutting forces associated with High Speed Machining (HSM) process. The predicted and experimental results for different materials and different cutting conditions are presented and compared and it is shown that the theory developed is capable of predicting the cutting forces and the other parameters associated with the HSM process. The extension of the theory to HSM has been successful within the machining conditions presented here in this paper. Further work is necessary to improve this theory further.
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Authors: Yasser M. Ali, Philip Mathew, Jun Wang
Abstract: Most existing models for abrasive jet machining (AJM) are based on erosion models for either ductile or brittle materials. This classification imposes some limitations, because most materials are neither absolutely ductile nor absolutely brittle, but lay within the continuous spectrum between those two idealizations. This work reports recent progress in the modeling of erosion processes for real materials, and discusses the implications of a new model in estimating the performance of AJM. The new model is more capable in explaining the effects of jet velocity, abrasive particle size, and various material properties on the efficiency of the cutting process.
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Authors: Da Ping Wan, Philip Mathew, Jun Wang
Abstract: Ultra-short pulsed laser ablation of crystalline silicon is characterized by a complicated heat diffusion process. In this research, a computational investigation is undertaken to achieve the temperature distribution and heat effect as a function of micromachining parameters. Heat accumulation and heat affected zone (HAZ) of silicon ablation by ultra-short lasers are estimated through solving coupled energy balance equations. The laser energy deposition and possible non-thermal ablation process are analyzed in the case of succession of laser pulses. Thermal-mechanical response induced by temperature gradient is discussed around the laser ablation region. The agreement between the model calculations and experimental results show that this research provides an efficient thermal analysis method, and a feasible way to optimize process parameters with minimum thermal damages.
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