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Laser-assisted direct roller imprinting of large-area microstructured optical surfaces

Microsystems & Nanoengineering 2024年第1期10卷 257-266页

作者： Keisuke Nagato Ken Takahashi Yuki Yajima Masayuki Nakao Department of mechanical engineering Graduate School of EngineeringThe University of Tokyo7-3-1 HongoBunkyo-kuTokyo 113-8656Japan

In this study,a high-throughput fabrication method called laser-assisted direct roller imprinting(LADRI)was developed to lower the cost of nanoimprinting large-area polymer films and to address problems associated with nanoimprinting,namely,microstructural damage and precision in flatness of entire film.With LADRI,the laser directly heats the microstructured surface of the roller mold,which heats and melts the surface of a polymethyl methacrylate(PMMA)film to replicate the microstructures on the mold rapidly.In this study,the effects of laser power density,scanning speed,size of the microstructures,and contact pressure on the replication speed were investigated experimentally.The replication speed increased as the power and scanning speed increased.However,because the film required heating until it filled the entire depth of the microstructure,an appropriate replication speed was necessary.This result was supported by simulation of the temperature distribution inside the mold and the PMMA using transient heat conduction analyses.To demonstrate the applications of LADRI,two different optical surfaces were replicated:an antireflection(AR)structure with conical structures sized several hundred nanometers and a lightextraction structure with a microlens array(MLA)comprising 10μm lenses,for display and illumination,respectively.The replication degree of the MLA was governed by the contact pressure.Polymer flow simulation indicated that the heat conduction and flow speeds of the melted PMMA surface were comparable within several tens of micrometers.In addition,the reflectivity of the AR structure decreased from 4 to 0.5%,and the light intensity of the light-extraction structure increased by a factor of 1.47.

关键词： microstructure roller conduction

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Analysis of Machinable Structures and Their Wettability of Rotary Ultrasonic Texturing Method

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Chinese Journal of mechanical engineering 2016年第6期29卷 1187-1192页

作者： XU Shaolin SHIMADA Keita MIZUTANI Masayoshi KURIYAGAWA Tsunemoto Division of Biomechanical engineering Graduate School of Biomedical Engineering Tohoku University Department of mechanical Systems engineering Graduate School of Engineering Tohoku University

Tailored surface textures at the micro- or nanoscale dimensions are widely used to get required functional performances. Rotary ultrasonic texturing （RUT） technique has been proved to be capable of fabricating periodic micro- and nanostructures. In the present study, diamond tools with geometrically defined cutting edges were designed for fabricating different types of tailored surface textures using the RUT method. Surface generation mechanisms and machinable structures of the RUT process are analyzed and simulated with a 3D-CAD program. Textured surfaces generated by using a triangular pyramid cutting tip are constructed. Different textural patterns from several micrometers to several tens of micrometers with few burrs were successfully fabricated, which proved that tools with a proper two-rake-face design are capable of removing cutting chips efficiently along a sinusoidal cutting locus in the RUT process. Technical applications of the textured surfaces are also discussed. Wetting properties of textured aluminum surfaces were evaluated by combining the test of surface roughness features. The results show that the real surface area of the textured aluminum surfaces almost doubled by comparing with that of a flat surface, and anisotropic wetting properties were obtained due to the obvious directional textural features.

关键词： rotary ultrasonic texturing geometrically defined cutting edges surface generation mechanisms machinable structures,wetting properties

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Flow imbalance in MHD flows in splitting ducts with locally different electric conductivities of the walls

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Journal of Hydrodynamics 2018年第5期30卷 920-927页

作者： Yang Luo Mengqi Zhu C.N.Kim Department of mechanical engineering Graduate School Kyung Hee University Department of mechanical engineering College of Engineering Kyung Hee University

In this study, three-dimensional liquid-metal magnetohydrodynamic splitting flows in a duct with one inflow channel and two outflow channels with locally different wall electric conductivities（different conductance ratios） are computationally examined. The numerical calculation is achieved with the use of CFX code, with a structured grid system chosen after a series of mesh independence tests. The detailed features of the MHD flows are depicted in a case where the electric conductivities of the two outflow ducts are quite different. Also, the interdependency among the current, fluid velocity, pressure and electric potential is elucidated in order to describe the electromagnetic characteristics of the liquid-metal flows. The result shows that the imbalance of the mass flow rate in the two outflow channels strongly depends on the wall conductivity（i.e., conductance ratio） of each outflow channel.

关键词： Liquid metal flow splitting duct flow imbalance numerical examination conductance ratio

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Countermeasure Against Regenerative and Forced Chatter of Flexible Workpieces in Milling Processs Using Bi-directional Excitation

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Transactions of Nanjing University of Aeronautics and Astronautics 2018年第1期35卷 10-19页

作者： Nakano Yutaka De Silva Amal Dilanka Takahara Hiroki Akiyama Yu Department of mechanical engineering School of EngineeringTokyo Institute of Technology Department of mechanical Sciences and engineering Graduate School of Science and EngineeringTokyo Institute of Technology

A novel extended methodology for chatter suppression in milling process by applying external forced vibrations to the workpiece in two orthogonal directions which are the feed and cross-feed directions.Both the regenerative and forced chatter suppression during the milling process of flexible workpieces are investigated.Here,the workpiece is subject to a sinusoidal periodic force in the feed direction to disrupt the regenerative effect.Additionally,to minimize the forced chatter,the workpiece is subject to the periodic excitation force in cross-feed direction.This force is proportional to the magnitude of the estimated cutting force in cross-feed direction and has a phase opposite to the cutting force to minimize the vibration amplitudes.The effectiveness of the proposed method is evaluated numerically and experimentally,for the spindle speed located in both the local minima and local maxima of the stability lobe diagram.The numerical simulations indicate significant suppression effect in terms of vibration amplitudes,resulting in suppression of both the regenerative chatter and the forced chatter.Experiments were conducted by using a workpiece-mounted active stage composed of flexure hinges and driven by piezoelectric actuators.The experimental results agree qualitatively with the numerical simulations.The proposed method indicates a remarkable vibration reduction effect for both regenerative and forced chatters.

关键词： self-excited vibration vibration control regenerative chatter forced chatter milling

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Mixing features in an electromagnetic rectangular micromixer for electrolyte solutions

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Journal of Hydrodynamics 2017年第4期29卷 668-678页

作者： M.M.Wen C.N.Kim Department of mechanical engineering Graduate School Kyung Hee University Department of mechanical engineering College of Engineering Kyung Hee University

In this study, a new magnetohydrodynamic（MHD） mixer for electrolyte solutions with pumping function is reported, and the mixing performance of the device for two different electrolyte solutions is numerically examined in a uniform magnetic field. Application of different potentials to different electrodes allows the current to be induced. The combination of the induced current and magnetic field yields Lorentz force, resulting in the fluid motion. The numerical simulation for the flows in the device is carried out with commercial software CFX. The validity of CFX code for the present numerical model is presented. The mixing performance of the fluids is investigated in many different cases with different combinations of input voltage of the electrode. This study shows that the mixing performance can be enhanced by applying spatially alternating positive and negative voltages to the electrodes. The present simulation results show that with a magnetic field intensity lower than 0.5 T, a voltage difference smaller than 2.0 V, and an electric conductivity of electrolyte solution of 1.5 S/m the pumping capabilities ranging 1.6×10^（-7）-3.6×10^（-6） kg/s and the mixing indexes higher than 0.90 can be obtained with sophisticated designs of the micromixer.

关键词： Mixer electrolyte solution Lorentz force CFX

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SiC_p及Al_2O_(3w)增强铸态混杂金属基复合材料的疲劳裂纹扩展机理(英文)

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Transactions of Nonferrous Metals Society of China 2014年第S1期24卷 1-13页

作者： AKM Asif IQBAL Yoshio ARAI Wakako ARAKI graduate school of Science and engineering Saitama University Division of mechanical engineering and Science Graduate School of Science and EngineeringSaitama University

研究了一种SiCp及Al2O3w增强铸态混杂金属基复合材料(MMC)的疲劳裂纹扩展(FCG)机理,同时对比研究了Al2O3w增强铸态金属基复合材料和铸态铝合金的疲劳裂纹扩展机理。在研究近临界和裂纹稳定扩展区域的疲劳裂纹扩展(FCG)机理时,发现混杂MM... 详细信息

研究了一种SiCp及Al2O3w增强铸态混杂金属基复合材料(MMC)的疲劳裂纹扩展(FCG)机理,同时对比研究了Al2O3w增强铸态金属基复合材料和铸态铝合金的疲劳裂纹扩展机理。在研究近临界和裂纹稳定扩展区域的疲劳裂纹扩展(FCG)机理时,发现混杂MMC的临界应力强度因子?Kth值高于其他两种材料的?Kth值,说明应力强度因子?K值较低时混杂MMC可以更好地抵抗裂纹扩展。随着?K值的降低,两种MMC在近临界区域显示出相似的FCG机理,即主要由增强相–基体界面的剥离控制,随后由铝基体中空隙的形核与合并控制;在裂纹稳定或中等扩展区域,?K值较高时FCG除了受界面上周期性裂纹扩展引起的增强相–基体界面剥离的影响之外,还显著受到铝基体中疲劳条带的影响。此外,在高?K值下,因为局部失稳断裂机制,可见铝基体中空隙的形核与合并以及SiCp和Al2O3w中的穿晶断裂。对于铸态铝合金,在低?K值下,FCG主要受空隙的形核与合并所控制;在高?K值下,FCG主要受铝晶粒的疲劳条带控制,随后受Si团簇中空隙的形核与合并控制。

关键词：铸态金属基复合材料疲劳裂纹扩展应力强度因子断裂

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Mixing of two different electrolyte solutions in electromagnetic rectangular mixers

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Journal of Hydrodynamics 2016年第1期28卷 114-124页

作者： Meimei WEN Chang Nyung KIM Yue YAN Department of mechanical engineering Graduate School Kyung Hee University Department of mechanical engineering College of Engineering Kyung Hee University

This study proposes a new electromagnetic rectangular mixer, and numerically examines the mixing characteristics of two different electrolyte solutions in the device under a uniform magnetic field. The mixer consists of a conduit with electrodes equipped on its top and bottom walls. The difference in the electric potentials applied to the sets of electrodes induces the current. The combination of the induced current and magnetic field yields Lorentz force, resulting in the fluid motion for pumping and mixing of the two different fluids. The numerical simulation is carried out with the use of commercial software CFX. The present numerical model is validated by an existing numerical work. The effect of different variables on mixing efficiency is investigated in many different cases with two different heights of the duct and various input voltages of the electrodes. The current simulation results indicate that the mixing performance can be enhanced by using multiple sets of electrodes and applying higher input voltages（absolute values） to the electrodes.

关键词： CFX electrolyte solution Lorentz force mixer mixing efficiency

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Trajectory tracking control of robotic transcranial magnetic stimulation

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International Journal of Intelligent Computing and Cybernetics 2019年第2期12卷 245-259页

作者： Zecai Lin Xin Wang Jian Yang school of mechanical engineering and Automation Harbin Institute of Technology Shenzhen Graduate SchoolShenzhenChina

Purpose–Transcranial magnetic stimulation(TMS)is a non-invasive brain stimulation technique.Based on the unique functions of TMS,it has been widely used in clinical,scientific research and other fields.Nowadays,the robot-assisted automatic TMS has become the trend.In order to simplify the operation procedures of robotic TMS and reduce the costs,the purpose of this paper is to apply the marker-based augmented-reality technology to robotic TMS system.Design/methodology/approach–By using the marker of ARToolKitPlus library and monocular camera,the patient’s head is positioned in real time.Furthermore,the force control is applied to keep contact between the coil and subject’s head.Findings–The authors fuse with visual positioning which is based on augmented-reality and force-control technologies to track the movements of the patient’s head,bring the coil closer to the stimulation site and increase treatment effects.Experimental results indicate that the trajectory tracking control of robotic TMS system designed in this paper is practical and flexible.Originality/value–This paper provides a trajectory tracking control method for the robotic TMS.The marker-based augmented-reality technology is implemented which simplifies the operation procedures of robotic TMS as well as reduce the costs.During the treatment process,the patients would wear an AR glasses,which can help patients relax through virtual scenes and reduce the uncomfortableness produce by treatment.

关键词： Trajectory tracking control Force control Marker-based augmented-reality technology,Robotic TMS

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Novel extended C-m models of flow stress for accurate mechanical and metallurgical calculations and comparison with traditional flow models

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Journal of Magnesium and Alloys 2022年第9期10卷 2516-2533页

作者： Man Soo Joun Mohd Kaswandee Razali Jae Dong Yoo Min Cheol Kim Jeong Muk Choi ReCAFT Gyeongsang National UniversityGraduate School of Mechanical and Aerospace EngineeringJinju 52828South Korea Gyeongsang National University Graduate School of Mechanical and Aerospace EngineeringJinju 52828South Korea MFRC Research CenterJinju 52818South Korea Jinhap Daejeon 34302South Korea

Here,we developed novel extended piecewise bilinear power law(C-m)models to describe flow stresses under broad ranges of strain,strain rate,and temperature for mechanical and metallurgical calculations during metal forming at elevated temperatures.The traditional C-m model is improved upon by formulating the material parameters C and m,defined at sample strains and temperatures as functions of the strain rate.The coefficients are described as a linear combination of the basis functions defined in piecewise patches of the sample strain and temperature domain.A comparison with traditional closed-form function flow models revealed that our approach using the extended piecewise bilinear C-m model is superior in terms of accuracy,ease of use,and adaptability;additionally,the extended C-m model was applicable to numerical analysis of mechanical,metallurgical,and microstructural problems.Moreover,metallurgy-related values can be calculated directly from the flow stress information.Although the proposed model was developed for materials at elevated temperatures,it can be applied over a broad temperature range.

关键词： Flow stress Power law model Piecewise bilinear function Numerical analysis Microstructural prediction Peak strain

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Large Deformation Analysis and Synthesis of Elastic Closed-loop Mechanism Made of a Certain Spring Wire Described by Free Curves

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Chinese Journal of mechanical engineering 2015年第4期28卷 756-762页

作者： IWATSUKI Nobuyuki KOSAKI Takashi Department of mechanical Sciences and engineering Graduate School of Science and EngineeringTokyo Institute of Technology

Recently novel mechanisms with compact size and without many mechanical elements such as bearing are strongly required for medical devices such as surgical operation devices. This paper describes analysis and synthesis of elastic link mechanisms of a single spring beam which can be manufactured by NC coiling machines. These mechanisms are expected as disposable micro forceps. Smooth Curvature Model（SCM） with 3rd order Legendre polynomial curvature functions is applied to calculate large deformation of a curved cantilever beam by taking account of the balance between external and internal elastic forces and moments. SCM is then extended to analyze large deformation of a closed-loop curved elastic beam which is composed of multiple free curved beams. A closed-loop elastic link is divided into two free curved cantilever beams each of which is assumed as serially connected free curved cantilever beams described with SCM. The sets of coefficients of Legendre polynomials of SCM in all free curved cantilever beams are determined by taking account of the force and moment balance at connecting point where external input force is applied. The sets of coefficients of Legendre polynomials of a nonleaded closed-loop elastic link are optimized to design a link mechanism which can generate specified output motion due to input force applied at the assumed dividing point. For example, two planar micro grippers with a single pulling input force are analyzed and designed. The elastic deformation analyzed with proposed method agrees very well with that calculated with FEM. The designed micro gripper can generate the desired pinching motion. The proposed method can contribute to design compact and simple elastic mechanisms without high calculation costs.

关键词： elastic link mechanism,closed-loop,spring beam,large deformation analysis,smooth curvature model,force balance equation,synthesi

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