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21.
Overview of finite elements simulation of temperature profile to estimate properties of materials 3D-printed by laser powder-bed fusion
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Habimana Jean Willy 李辛未 Yong Hao Tan 陈哲 Mehmet Cagirici Ramadan Borayek Tun Seng Herng Chun Yee Aaron Ong 李朝将 丁军 《中国物理 B》2020,(4):98-109
Laser powder bed fusion(LPBF),like many other additive manufacturing techniques,offers flexibility in design expected to become a disruption to the manufacturing industry.The current cost of LPBF process does not favor a try-anderror way of research,which makes modelling and simulation a field of superior importance in that area of engineering.In this work,various methods used to overcome challenges in modeling at different levels of approximation of LPBF process are reviewed.Recent efforts made towards a reliable and computationally effective model to simulate LPBF process using finite element(FE)codes are presented.A combination of ray-tracing technique,the solution of the radiation transfer equation and absorption measurements has been used to establish an analytical equation,which gives a more accurate approximation of laser energy deposition in powder-substrate configuration.When this new analytical energy deposition model is used in in FE simulation,with other physics carefully set,it enables us to get reliable cooling curves and melt track morphology that agree well with experimental observations.The use of more computationally effective approximation,without explicit topological changes,allows to simulate wider geometries and longer scanning time leading to many applications in real engineering world.Different applications are herein presented including:prediction of printing quality through the simulated overlapping of consecutive melt tracks,simulation of LPBF of a mixture of materials and estimation of martensite inclusion in printed steel. 相似文献
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Ahn TK Yoon ZS Hwang IW Lim JK Rhee H Joo T Sim E Kim SK Aratani N Osuka A Kim D 《The journal of physical chemistry. B》2005,109(22):11223-11230
We have investigated the overall excitation energy relaxation dynamics in linear porphyrin arrays as well as the energy transport phenomena by attaching an energy acceptor to one end of a linear porphyrin array by using steady state and time-resolved spectroscopic measurements. We have revealed that the solvation dynamics as well as the conformational dynamics contributes significantly to the energy relaxation processes of linear porphyrin arrays. Consequently, long porphyrin arrays no longer serve as good energy transmission elements in donor-acceptor linked systems due to conformational heterogeneities which provide the non-radiative deactivation channels as energy quenchers. 相似文献
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C.J. Tun C.H. Kuo Y.K. Fu C.W. Kuo Mitch M.C. Chou G.C. Chi 《Journal of Crystal Growth》2009,311(14):3726-3730
This study demonstrates a pure c-plane AlGaN epilayer grown on a γ-LiAlO2 (1 0 0) (LAO) substrate with an AlN nucleation layer grown at a relatively low temperature (LT-AlN) by metal-organic chemical vapor deposition (MOCVD). The AlGaN film forms polycrystalline film with m- and c-plane when the nucleation layer grows at a temperature ranging from 660 to 680 °C. However, a pure c-plane AlGaN film with an Al content of approximately 20% can be obtained by increasing the LT-AlN nucleation layer growth temperature to 700 °C. This is because the nuclei density of AlN increases as the growth temperature increases, and a higher nuclei density of AlN deposited on LAO substrate helps prevent the deposition of m-plane AlGaN. Therefore, high-quality and crack-free AlGaN films can be obtained with a (0 0 0 2) ω-rocking curve FWHM of 547 arcsec and surface roughness of 0.79 nm (root-mean-square) using a 700-°C-grown LT-AlN nucleation layer. 相似文献
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We show how to approximate the feasible region of structured convex optimization problems by a family of convex sets with
explicitly given and efficient (if the accuracy of the approximation is moderate) self-concordant barriers. This approach
extends the reach of the modern theory of interior-point methods, and lays the foundation for new ways to treat structured
convex optimization problems with a very large number of constraints. Moreover, our approach provides a strong connection
from the theory of self-concordant barriers to the combinatorial optimization literature on solving packing and covering problems. 相似文献
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Kwati Leonard Junichi Kurawaki Katumitu Hayakawa Myint Thein Tun Yoshihumi Kusumoto 《Colloid and polymer science》2009,287(7):773-778
Laser irradiation of copper(II) tetrasulfonated phthalocyanine (CuTsPc) microcrystals in poor organic solvents such as methanol,
2-methyl-2-propanol, ethanol, tetrahydrofuran, and acetone has produced CuTsPc nanoparticles with 15–112 nm in diameter. Field
emission scanning electron microscopy (FESEM) images have shown the formation of CuTsPc nanoparticles in poor organic solvents
used in this work. The mean diameters of CuTsPc nanoparticles obtained from transmission electron microscopy (TEM) images
in methanol, 2-methyl-2-propanol, ethanol, tetrahydrofuran, and acetone were determined to be 26, 36, 35, 86, and 78 nm, respectively.
A correlation between the size of CuTsPc nanoparticles and a solvent polarity could be found in this work. 相似文献
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