The Experts below are selected from a list of 6189 Experts worldwide ranked by ideXlab platform
Bekir Sami Yilbas - One of the best experts on this subject based on the ideXlab platform.
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Thermal analysis of Laser Drilling process
SpringerBriefs in Applied Sciences and Technology, 2013Co-Authors: Bekir Sami YilbasAbstract:© 2013, The Author(s). In Laser Drilling process, the material removal involves with evaporation at the surface, liquid ejection, and solid heating. However, liquid ejection vanishes for the Lasers with the pulse length within the rage and higher than the nanoseconds. However, in Drilling applications mass removal by liquid ejection is desirable because the rate of material removed becomes high. Analytical modeling the Laser heating process in relation to Drilling is difficult, since process involves with the phase change and fluid flow due to the evaporation at the surface. However, numerical modeling is feasible with some useful assumptions.
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Laser heating mechanism including evaporation process initiating Laser Drilling
International Journal of Machine Tools & Manufacture, 1995Co-Authors: Bekir Sami Yilbas, Ahmet Z şahin, R DaviesAbstract:Abstract A Laser heating mechanism initiating the Drilling process is examined. The study includes conduction and convection effects and assumes a steady-state evaporation process. This enables estimation of the limits of the Fourier theory in Laser Drilling applications. Using the model described in the analysis, maximum temperature attained inside the material, nucleation, explosion process and Drilling efficiency are predicted. The results obtained from the present work for the vapor front velocity are compared to those obtained from previous experiments. In addition, a Laser Drilling experiment is carried out while monitoring the surface evaporation process. This enables correlation of the theoretical results with the experiments.
Xiaoyue Hu - One of the best experts on this subject based on the ideXlab platform.
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Laser Drilling of structural ceramics a review
Journal of The European Ceramic Society, 2017Co-Authors: Hongjian Wang, Lijuan Zheng, Chengyong Wang, Xiaoyue HuAbstract:Abstract Structural ceramics are becoming widely popular in numerous fields because of high mechanical and physical properties. It is of great difficulty for conventional techniques to machine brittle and hard materials. As one of nontraditional machining methods, Laser beam machining has emerged as an effective technique for Drilling of ceramics. This paper reviews the research work on Laser Drilling of structural ceramics from its different pulse width. Lasers have been discussed to understand effects of critical experimental parameters on the quality characteristics and physical mechanisms involved in Drilling ceramics. In addition, it is held that heat and liquid-assisted Laser processing serves as a useful method to improve processing quality. Computational approaches of ANSYS and COMSOL are used to predict Laser input parameters’ effects on quality of hole and describe the physical phenomena during processing. Comments on Laser Drilling of ceramics developments and future directions are provided at the end.
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Laser Drilling of structural ceramics—A review
Journal of The European Ceramic Society, 2017Co-Authors: Hongjian Wang, Lijuan Zheng, Chengyong Wang, Xiaoyue HuAbstract:Abstract Structural ceramics are becoming widely popular in numerous fields because of high mechanical and physical properties. It is of great difficulty for conventional techniques to machine brittle and hard materials. As one of nontraditional machining methods, Laser beam machining has emerged as an effective technique for Drilling of ceramics. This paper reviews the research work on Laser Drilling of structural ceramics from its different pulse width. Lasers have been discussed to understand effects of critical experimental parameters on the quality characteristics and physical mechanisms involved in Drilling ceramics. In addition, it is held that heat and liquid-assisted Laser processing serves as a useful method to improve processing quality. Computational approaches of ANSYS and COMSOL are used to predict Laser input parameters’ effects on quality of hole and describe the physical phenomena during processing. Comments on Laser Drilling of ceramics developments and future directions are provided at the end.
Changcheng Li - One of the best experts on this subject based on the ideXlab platform.
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investigation of underwater Laser Drilling for brittle substrates
Journal of Materials Processing Technology, 2009Co-Authors: Chwanhuei Tsai, Changcheng LiAbstract:Abstract The aim of this paper is to present and discuss data on underwater Laser Drilling techniques for brittle substrates. Drilling under water reduced substrate defects that typically result from conventional Laser Drilling in air. In this study, the substrates were submerged 1 mm beneath the water surface. A CO 2 Laser was used to drill holes into LCD glass and alumina substrates. It was found that the underwater Laser Drilling quality for these materials is much better than that from Laser Drilling in air. Underwater Laser Drilling reduced the phenomena of micro-cracking and minimized the size of the area affected by heat from the Laser. Also in this study, single-hole Drilling and array-holes Drilling by percussion and trepanning were conducted and analyzed both in air and underwater. The minimum distance between the two neighbour holes that can be obtained was much shorter in water than in air. The SEM photographs of the holes illustrate the contrast in Drilling quality. The relationship between Laser power, pulse repetition rate, and the hole quality was also evaluated.
T. William Clyne - One of the best experts on this subject based on the ideXlab platform.
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Laser Drilling of cooling holes through plasma sprayed thermal barrier coatings
Surface & Coatings Technology, 2004Co-Authors: K. T. Voisey, T. William ClyneAbstract:Abstract Laser Drilling is a non-contact process that can be used to form small holes in a wide variety of materials with a high degree of precision and reproducibility. The advantages of being able to drill difficult materials, specifically superalloys and ceramics, are exploited in the Laser Drilling of cooling holes in thermal barrier coated superalloys. Plasma sprayed thermal barrier coatings (TBCs) consist of a partially stabilised zirconia top coat and a NiCrAlY bond coat, deposited on a Ni-superalloy substrate. Laser Drilling was performed using a pulsed Nd:YAG Laser ( λ =1.06 μm), with a focussed spot power density of approximately 0.2 MW mm −2 . Holes were drilled at both normal and inclined angles of incidence. The effect of Drilling from the side of the metallic substrate, rather than the ceramic top coat, has been investigated. Laser-induced microstructural features, such as interfacial cracking, are reported. For the conditions used here, assist gas has a negligible effect on the volume of material removed per pulse, but does create additional features in the resolidified ceramic surrounding the hole. A spontaneous debonding technique was used, in conjunction with a finite difference process model, to investigate the effect of Laser Drilling on the interfacial toughness of plasma sprayed TBCs. Drilling was found to increase slightly the interfacial toughness of the TBC. This is attributed to the crack arresting effect of a resolidified ceramic layer that partially lines the hole.
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quantification of melt ejection phenomena during Laser Drilling
MRS Proceedings, 2000Co-Authors: K. T. Voisey, C F Cheng, T. William ClyneAbstract:During Laser Drilling, material removal in general occurs both by vaporisation and by the expulsion of molten material. The latter commonly arises as a result of the rapid build-up of gas pressure within the growing cavity as evaporation takes place, but the precise mechanisms responsible for the phenomenon are still unclear. The current work is aimed at gaining an insight into these mechanisms via measurements of the amount of material ejected from cavities during Laser Drilling under different conditions. Attention is first devoted to the issues which need to be considered when making experimental measurements of the fraction of material removed by melt ejection. These include the collection efficiency and the possibility of chemical changes occurring during the process. Results are then presented from work with a range of metallic substrates (mild steel, tungsten, copper, titanium, aluminium and nickel), drilled with a JK701 Nd-YAG Laser under different conditions. Observed variations in the melt ejection levels have been studied for mild steel and aluminium and these are briefly considered in terms of the expected effects of certain material property values and the mechanisms of melt ejection. Results from an existing finite difference heat flow model are used to investigate the significance of melt ejection.
Xiaowu Ni - One of the best experts on this subject based on the ideXlab platform.
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modeling and simulation on long pulse Laser Drilling processing
International Journal of Heat and Mass Transfer, 2014Co-Authors: Yiming Zhang, Zhonghua Shen, Xiaowu NiAbstract:Abstract Combining the modified level-set method a 2D model is developed to simulate the Laser Drilling process on aluminum slab with millisecond pulsed Laser. By utilizing equivalent specific heat capacity and adding source terms of gas dynamics, phase transition is modeled. Modified level-set method is developed in order to trace the liquid–gas interface as well as consider mass loss during evaporation and boiling. The possible effects which can impact the dynamic behavior of the keyhole are taken into account, containing gravity, recoil pressure of the metallic vapor, surface tension, and Marangoni effect. Based on such model the impacts of Laser fluence and pulse duration on keyhole width and depth, average Drilling velocity, morphology and quality, melt ejection mode transition as well as velocity of melt ejecta are investigated. Compared with some corresponding experiment results, the validity of the established model is verified and the mechanisms of phenomena during Laser Drilling are analyzed.
