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Collapse behavior evaluation of hybrid thin-walled member by stacking condition

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Transactions of Nonferrous Metals Society of China 2011年第A01期21卷 135-140页

作者： Kil-Sung LEE Hyeon-Kyeong SEO Yong-June YANG Woo-Chae HWANG kwang-hee im In-Young YANG R&D Center Dacc LTD. 948-13 Dunsan-ri Bongdong-eup Wanju-gun Jeonbuk 565-902 Korea Departments of Advanced Parts and Materials Engineering Graduate School Chosun University Department of Automotive Engineering Woosuk University Departments of Mechanical Design Engineering Chosun University

The recent trend of vehicle design aims at crash safety and environmentally-friendly aspect. For the crash safety aspect, the energy absorbing members should absorb collision energy sufficiently but for the environmentally-friendly aspect, the vehicle structure must be light weight in order to improve the fuel efficiency and reduce the tail gas emission. Therefore, the light weight of vehicle must be achieved in a securing safety status of crash. An aluminum or carbon fiber reinforced plastics (CFRP) is representative one of the light-weight materials. Based on the respective collapse behavior of aluminum and CFRP member, the collapse behavior of hybrid thin-walled member was evaluated. The hybrid members were manufactured by wrapping CFRP prepreg sheets outside the aluminum hollow members in the autoclave. Because the CFRP is an anisotropic material whose mechanical properties, such as strength and elasticity, change with its stacking condition, the effects of the stacking condition on the collapse behavior evaluation of the hybrid thin-walled member were tested. The collapse mode and energy absorption capability of the hybrid thin-walled member were analyzed with the change of the fiber orientation angle and interface number.

关键词： collapse behavior aluminum and CFRP hybrid thin-walled member stacking condition

Ultrasonic Approach of Rayleigh Pitch-Catch Contact Ultrasound Waves on CFRP Laminated Composites

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Journal of Materials Science & Technology 2008年第3期24卷 407-409页

作者： In-Young Yang kwang-hee im Uk Heo David K Hsu Je-Woong Park Hak-Joon Kim Sung-Jin Song School of Mechanical Eng. Chosun Univ Department of Automotive Eng. Woosuk Univers-ity Center for Nondestructive Evaluation Iowa State University Dept.of Naval Arch.and Ocean Eng. Chosun Univ School of Mechanical Eng. Sungkyunkwan University

CFRP （carbon fiber reinforced plastics） composite materials have wide applicability because of their inherent design flexibility and improved material properties. However, impacted composite structures have 50%-75% less strength than undamaged structures. In this work, a CFRP composite material was nondestructively characterized in order to ensure product quality and structural integrity of CFRP and one-sided pitch-catch technique was developed to measure impacted-damaged area by using an automated-data acquisition system in an immersion tank. A pitch-catch signal was found to be more sensitive than normal incidence backwall echo of longitudinal wave under defect conditions in the composite.

关键词： impact damages C-scanner Carbon fiber reinforced plastics (CFRP) Pitchcatch mode

ULTRASONIC INFLUENCE OF POROSITY LEVEL ON CFRP COMPOSITE LAMINATES USING RAYLEIGH PROBE WAVES

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Acta Mechanica Solida Sinica 2008年第4期21卷 298-307页

作者： Je-Woong Park Do-Jung Kim kwang-hee im Sang-Kyu Park David K.Hsu Adam H.Kite Sun-Kyu Kim Kil-Sung Lee In-Young Yang Dept.of Naval Architecture and Ocean Eng. Chosun UniversityKwangju 501-759Korea Dept.of Automotive Eng. Woosuk UniversitySamrae-upWanju-kunChonbuk565-701Korea Center for Nondestructive Evaluation Iowa State UniversityAmesIowa 50011USA Division of Precision Mec.Eng. Chonbuk National UniversityJeonju 561-756Korea School of Mechanical Engineering Chosun UniversityKwangju 501-759Korea

It was found that a pitch-catch signal was more sensitive than normal incidence backwall echo of longitudinal wave to subtle flaw conditions in the composites （damages, fiber orientation, low level porosity, ply waviness, and cracks）. Both the strength and stiffness depend on the fiber orientation and porosity volume in the composites. The porosity content of a composite structure is critical to the strength and performance of the structure in general. The depth of the sampling volume where the pitch-catch signal came from was relatively shallow with the head- to-head miniature Rayleigh probes, but the depth can be increased by increasing the separation distance of the transmitting and receiving probes. Also, a method was utilized to determine the porosity content of a composite lay-up by processing micrograph images of the laminate. A free software package was utilized to process micrograph images of the test sample. The results from the image processing method were compared with existing data. Beam profile was characterized in unidirectional CFRP（carbon fiber reinforced plastics） using pitch-catch Rayleigh probes and the one-sided pitch-catch technique was utilized to produce C-scan images with the aid of the automatic scanner.

关键词： ply-layup orientation unidirectional CFRP beam profile pitch-catch contact mode,porosity level

Friction Behavior of Magnetorheological Fluids with Different Material Types and Magnetic Field Strength

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Chinese Journal of Mechanical Engineering 2016年第1期29卷 84-90页

作者： ZHANG Peng LEE kwang-hee LEE Chul-hee Department of Mechanical Engineering Inha University

Magnetorheological （MR） fluid is a type of a smart material that can control its mechanical properties under a magnetic field. Iron particles in MR fluid form chain structures in the direction of an applied magnetic field, which is known as MR effect, resulting in variation of stiffness, shear modulus, damping and tribological characteristics of MR fluid. As MR effect depends on the density of particles in the fluid or the strength of a magnetic field, the experiments are conducted to evaluate the friction property under reciprocating motion by changing the types of MR fluid and the strength of a magnetic field. The material of aluminum, brass, and steel are chosen for specimen as they are the most common material in mechanical applications. The surfaces of specimen are also observed by optical microscope before and after experiments to compare the surfaces with test conditions. The comparing results show that the friction coefficient increases as the strength of a magnetic field increases in regardless of types of MR fluid or the material. Also the density of particle in MR fluid affects the friction characteristic. The results from this research can be used to improve the performance of mechanical applications using MR fluid.

关键词： Magnetorheological (MR) fluid friction characteristics smart material magnetic field

Friction and wear of textured surfaces produced by 3D printing

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Science China(Technological Sciences) 2017年第9期60卷 1400-1406页

作者： HONG Yi ZHANG Peng LEE kwang-hee LEE Chul-hee Department of Mechanical Engineering Inha University Incheon 402-751 Korea

Surface texture patterns have great potential for improving tribological performance in terms of reducing friction and wear. The most common methods for surface texatring are laser and injection molding. The 3D printing method is also used to build parts, patterns, and molds that feature fine details for a wide range of applications because texture manufacturing by 3D printing is faster, more flexible, and less expensive than traditional techniques. To date, there has been no research on textured surfaces produced by 3D printing. Therefore, a new fabrication method using 3D printing to improve friction and wear properties is a topic worth exploring. In this study, a reciprocating friction tester was used to evaluate the friction and wear properties of different surface textures produced by 3D printing. The surface of specimens was examined by electron microscope and scanning electron microscope before and after the test. The results show that surface texturing can be applied to 3D printed parts to improve their friction and wear performance.

关键词： three-dimensional (3D) printing texture friction wear

Research on Cavitation Characteristics and Influencing Factors of Herringbone Gear Pump

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Computer Modeling in Engineering & Sciences 2024年第6期139卷 2917-2946页

作者： Jinlong Yang kwang-hee Lee Chul-hee Lee Department of Mechanical Engineering of Inha University Incheon22212South Korea

Cavitation is a common issue in pumps,causing a decrease in pump head,a fall in volumetric efficiency,and an intensification of outlet flow *** is one of the main hazards that affect the regular operation of the *** on pump cavitation mainly focuses on mixed flow pumps,jet pumps,external spur gear pumps,***,there are few cavitation studies on external herringbone gear *** addition,pumps with different working principles significantly differ in the flow and complexity of the internal flow ***,it is urgent to study the cavitation characteristics of external herringbone gear *** with experimentalmethods,visual research and cavitation area identification are achieved through computation fluid dynamic(CFD),and changing the boundary conditions and shape of the gear rotor is *** simulation yields a head error of only 0.003%under different grid numbers,and the deviation between experimental and simulation results is less than 5%.The study revealed that cavitation causes flow pulsation at the outlet,and the cavitation serious area is mainly distributed in the meshing gap and meshing *** can be inhibited by reducing the speed,increasing the inlet pressure,and changing the helix angle can be *** example,when the inlet pressure is 5 bar,the maximumgas volume fraction in themeshing area is less than 50%.These results provide a reference for optimizing the design and finding the optimal design parameters to reduce or eliminate cavitation.

关键词： Herringbone gear pump cavitation rotating speed inlet pressure helix angle TwinMesh

Effect of stick-slip on magneto-rheological elastomer with a magnetic field

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Friction 2017年第4期5卷 383-391页

作者： Chenglong LIAN kwang-hee LEE Jun-wook AN Chul-hee LEE Department of Mechanical Engineering Inha University100 InharoNam-guIncheon 22212Republic of Korea Department of Construction Machinery Engineering Inha University100 InharoNam-guIncheon 22212Republic of Korea

This study investigated the stick-slip characteristics of a magneto-rheological elastomer (MRE) against an aluminum ***,the MRE was manufactured,and a stick-slip tester was employed to evaluate the stick-slip performance of the MRE under different velocities and load conditions with and without a magnetic *** fast Fourier transform (FFT) of the friction force of the stick-slip and the roughness of the aluminum plate surface were calculated to confirm the stick-slip *** the tests,the wear surfaces were observed to evaluate the wear properties of the MRE regarding the *** showed that the stick-slip was smaller at lower *** higher velocity,the reduction of the stick-slip under a magnetic field was more clearly ***,the wear reduced with reduced stick-slip under a magnetic field.

关键词： stick-slip friction wear magneto-rheological elastomer

Interfacial modulation of bifunctional electrolyte additive engineering for dendrite-free and robust lithium metal anode

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Journal of Energy Chemistry 2024年第10期97卷 120-127,I0003页

作者： Mahammad Rafi Shaik Yongmin Park Young-kwang Jung Won Bin im Division of Materials Science and Engineering Hanyang University222Wangsimni-roSeongdongguSeoul 0473Republic of Kor Department of Chemical Engineering and Biotechnology University of CambridgeCambridge CB3 OASUK

Anode materials for rechargeable electric car batteries are obtained from Li-metal owing to their extremely high specific capacity and low redox ***,safety concerns related to dendrite formation on the anode surface caused by the uneven distribution of Li-ions during the discharge process interfere with the use of Li-metal in industrial *** this study,methyl vinyl sulfone(MVS),a sulfone-based functional electrolyte additive,is used in an additive engineering strategy to control Lielectrolyte interactions and address the aforementioned *** dendrite growth may be restricted,and transition metal degradation on the surface of the cathode can be reduced by the MVS-derived functional electrolyte additive interfacial *** electrochemical performance of an ethylene carbonate/dimethyl carbonate(EC/DMC)+1 wt% MVS Li-metal anode of a Li||Li symmetric cell exhibits remarkable cycle stability,maintaining a low overvoltage for over 750 h at 1 mA cm^(-2),and capacity of 1 mA h cm^(-2).Additionally,LiNi_(0.8)Co_(0.1)Mn_(0.1)O_(2)(NCM811) full cells with the MVS additive exhibit enhanced electrochemical stability for 250 cycles at a current density of 100 mA g^(-1).This study provides an innovative approach for stabilizing the metal-electrolyte interfacial layer that may be used for practical applications in metal-based rechargeable batteries.

关键词： Lithium rechargeable battery Dendrite-free Electrolyte additive Bifunctional electrolyte Interfacial layer

Xanthogranulomatous cholecystitis managed by laparotomy may go through troublesome clinical course: Reflection of severe inflammation

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Hepatobiliary & Pancreatic Diseases International 2023年第2期22卷 210-212页

作者： hee Ju Kim kwang Yeol Paik Department of Surgery Yeoiudo St.Mary’s HospitalCollege of MedicineThe Catholic University of Korea College of MedicineSeoul 07345Korea

To the Editor: Xanthogranulomatous cholecystitis(XGC) is an uncommon inflammatory disease of the gallbladder, and its incidence is reported to be 1.3%-5.2% [1]. XGC is diagnosed by histopathological examination, characterized by severe inflammatory destruction followed by a granulomatous reaction, marked proliferative fibrosis, and infiltration of inflammatory cells [2].

关键词： granuloma cholecystitis inflammation