Dynamic stability of a cantilevered Timoshenko beam on partial elastic foundations subjected to a follower force

This paper presents the dynamic stability of a cantilevered Timoshenko beam with a concentrated mass, partially attached to elastic foundations, and subjected to a follower force. Governing equations are derived from the extended Hamilton’s principle, and FEM is applied to solve the discretized equation. The influence of some parameters such as the elastic foundation parameter, the positions of partial elastic foundations, shear deformations, the rotary inertia of the beam, and the mass and the rotary inertia of the concentrated mass on the critical flutter load is investigated. Finally, the optimal attachment ratio of partial elastic foundation that maximizes the critical flutter load is presented.     

Characteristics of a transiently propagating crack in functionally graded materials

When a crack propagates with acceleration, deceleration and time rates of change of stress intensity factors, it is very important for us to understand the effects of acceleration, deceleration and time rates of change of stress intensity factors on the individual stresses and displacements at the crack tip. Therefore, the crack tip stress and displacement fields for a transiently propagating crack along gradient in functionally graded materials (FGMs) with an exponential variation of shear modulus and density are developed and the characteristics of a transiently propagating crack from the fields are analyzed. The effects of the rate of change of the stress intensity factor and the crack tip acceleration on the individual stresses at the crack tip are opposite each other. Specially, the isochromatics (constant maximum shear stress) of Mode I tilt backward around the crack tip with an increase of crack tip acceleration, and tilt forward around the crack tip with an increase of the rate of change of the dynamic mode I stress intensity factor. This paper was recommended for publication in revised form by Associate Editor Chongdu Cho Kwang-Ho Lee received a Ph.D. degree in Yeungnam University in 1993. Dr. Lee is currently a professor at the School of Mechanical and Automotive Engineering at Kyungpook National University in Korea. He also had worked in KOMSCO as an engineer and researcher (1982.3–1996.2). He is interested in the fields of fracture and stress analysis on the composite, interface, nano and functionally graded materials by theoretical and experimental mechanics. Specially, his major interest is analysis of dynamic crack tip fields. Young-Jae Lee received his B.S degree in Agricultural Civil Engineering from Gyeongsang National University (GNU) in 1982. He then received his M.S. and Ph.D. degrees from GNU in 1984 and 1995, respectively. Dr. Lee is currently a professor at the department of Civil Engineering at Kyungpook National University in Korea. From 2005 to 2006, he had served as an editor of Korea Institute for Structure Maintenance and Inspection. His research interests are in the area of evaluation, diagnosis and optimum design of structure. Sang-Bong Cho received a Ph. D. degree from Tokyo University in 1989. Dr. Cho is currently a professor at the division of Mechanical and Automation Engineering at Kyungnam University in Korea. His research interests are in the area of fracture mechanics, FEM stress analysis and fretting fatigue.     

A pressure output feedback control of turbo compressor surge with a thrust magnetic bearing actuator

This paper presents a pressure output feedback control of turbo compressor surge using tip clearance actuation with a thrust magnetic bearing actuator. First, static and dynamic compressor models were obtained for a commercial turbocharger, and the surge point was found through local stability analysis. Then, the effect of tip clearance on the compressor pressure rise was derived, and Lyapunov analysis was used to establish a limit of stability with tip clearance modulation. After that, a linear quadratic (LQ) state feedback control was designed considering the limit established by the Lyapunov analysis. In addition, an extended Kalman filter (EKF) was designed to estimate the mass flow rate from the measured compressor pressure. Finally, the pressure output feedback controller was built by combining the LQ state feedback control and EKF. Control simulation proved the effectiveness of the output feedback controller. This paper was recommended for publication in revised form by Associate Editor Dong Hwan Kim Dr. Ahn earned Ph.D. from Seoul National University in 2001. He was a research associate of University of Virginia. He is currently an assistant professor of department of mechanical engineering at Soongsil University and serving as an editor of international journal of rotating machinery. His research interests are rotordynamics, control and mechatronics. Mr. Park is a junior research engineer in Doosan infracore. He received his master from Seoul National University. His research area is on dynamics and control of rotating machinery. Dr. Sanadgol is an assistant Professor of Physics and Engineering at Sweet Briar College. She earned her PhD in Mechanical and Aerospace Engineering with a focus in controls from the University of Virginia in 2006. Her research interests are in controlling flow instabilities in compressors and application of nonlinear control theories to mechatronics systems. Dr. Park received his PhD degree from the Seoul National University, Korea in 2007. He is currently director of research institute at KMB&SENSOR company. His research interests include the precision machine design, rotor dynamics, and magnetic actuators. Dr. Han received the Dipl.-Ing. and Dr.-Ing. in mechanical engineering from University of Karsruhe, Germany in 1975 and 1979, respectively. In 1982, he joined the school of mechanical and aerospace engineering, Seoul National University as an assistant professor. He is currently an honorary professor of mechanical engineering. His research interests are in machine element design, magnetic bearing, lubrication engineering and Bio-MEMS devices. Dr. Maslen is a Professor of Mechanical and Aerospace Engineering at the University of Virginia. He earned his Bachelor of Science in 1980 from Cornell University and his doctorate from the University of Virginia in 1991. His research focuses on application of automatic controls to electromechanical systems with a concentration in magnetic bearings.     

A study on the tension estimator by using register error in a printing section of roll to roll e-printing systems

The focus of this study is on the development of a mathematical model for estimating tension of a printing section by using the register error in R2R (Roll to Roll) e-Printing systems. In a printing section of conventional R2R printing systems, the tension is generally measured not for controlling but for monitoring, because the tension control may cause the occurrence of a register error. But, for high precision control, the tension in the R2R e-Printing system must be controlled as well as measured for more precise control of the register error. The tension can be measured by the loadcell in the conventional R2R systems. However, installing a loadcell on the R2R systems causes extra economic burden. In addition, the space for adding a loadcell on R2R systems is limited due to many components including dryers, lateral guider, doctor blade, ink supply unit and cooling unit. Therefore, a tension estimator can be another possibility for predicting the tension in a printing section. In this study, a new tension estimation model is proposed. The proposed model is based on the register error model, the equivalent torque equation, and the tension model considering tension transfer. Numerical simulations and experimental results showed that the proposed model was effective in estimating the tension in a printing section. This paper was recommended for publication in revised form by Associate Editor Hong Hee Yoo Chang-Woo Lee received a B.S. degree in Mechanical Engineering from Konkuk University in 2001. He received his M.S. and Ph.D. degrees from Konkuk university in 2003 and 2008, respectively. Dr. Lee is currently a researcher at the Flexible Display Roll to Roll Research Center at Konkuk University in Seoul, Korea. Dr. Lee’s research interests are in the area of fault tolerant control, R2R e-Printing line design, and tension-register control. He is the holder of several patents related to R2R e-Printing system. Jang-Won Lee received the B.S. and M.S.degrees in mechanical engineering from Konkuk University, Seoul, Korea. He studied continuous flexible process at the FDRC (Flexible Display R2R Research Center, Project Director: Kee-Hyun Shin), as a reseacher from the concentment to 2008. Since 2008, he has been a Research Engineer with the SKC Films R&D, Suwon, Gyeonggi-do, Korea. Now he is great on the plastic flim mechanics such as a scratch on the film surface, film extruding, winding/slitting mecha-nism and coating processes. Hyunkyoo Kang received the B.S. and M.S degree in 2000 and 2003 res-pectively from Konkuk Uni-versity, Seoul, Korea, where he is currently working toward the Ph. D. degree in mechanical design. He took part in the development of an autoalign guiding system for high-speed winding in a cable winding system, a 3-D roll-shape diagnosis method in a steel rolling system, a design of register controller for high-speed converting machine and real-time control design of electronic printing machine. His research topics include register modeling and control for printed electronics and distributed real-time control. Kee-Hyun Shin received the B.S. degree from Seoul National University, Seoul, Korea, and the M.S. and Ph.D. degrees in mechanical engineering from Oklahoma State University (OSU), Stillwater. Since 1992, he has been a Professor with the Department of Mechanical and Aerospace Engineering, Konkuk University, Seoul, Korea. For more than 18 years, he has covered several research topics in the area of web handling, including tension control, lateral dynamics, diagnosis of defect rolls/rollers, and fault-tolerant realtime control in the Flexible Display Roll-to-Roll Research Center, Konkuk University, of which he has also been a Director. He is the author of Tension Control (TAPPI Press, 2000) and is the holder of several patents related to R2R e-Printing system.     

Experimental study on heat transfer characteristics of internal heat exchangers for CO2 system under cooling condition

This paper presents the heat transfer characteristics of the internal heat exchanger (IHX) for CO₂ heat pump system. The influence on the IHX length, the mass flow rate, the shape of IHX, the operating condition, and the oil concentration was investigated under a cooling condition. Four kinds of IHX with a coaxial type and a micro-channel type, a mass flow meter, a pump, and a measurement system. With increasing of the IHX length, the capacity, the effectiveness, and the pressure drop increased. For the mass flow rate, the capacity of micro-channel IHX are higher about 2 times than those of coaxial IHX. The pressure drop was larger at cold-side than at hot-side. In the transcritical CO₂ cycle, system performance is very sensitive to the IHX design. Design parameters are closely related with the capacity and the pressure drop of CO₂ heat pump system. Along the operating condition, the performance of CO₂ IHXs is different remarkably. For oil concentration 1, 3, 5%, the capacity decreases and the pressure drop increased, as compared with oil concentration 0%. This paper was recommended for publication in revised form by Associate Editor Yong Tae Kang Prof. Young-Chul Kwon received his B.S. degree in Precision Mechanical Engineering from Pusan National University, Korea, in 1989. He then received his M.S. and Ph.D. degrees from POSTECH, in 1991 and 1996, respectively. Dr. Kwon is currently a Professor at the Division of Mechanical Engineering at Sunmoon University in Chungnam, Korea. He serves as a chief of the Institute of Automation and Energy Technology. Dr. Kwon’s research interests include heat exchanger, CO₂ cycle, heat pump, and energy recovery ventilator for HVAC&R. Mr. Dae-Hoon Kim is currently Doctoral student at the Mechanical Engineering from Hanyang University in Seoul, Korea. His research topics include experimental and numerical of CO₂ heatpump system. He has conducted a study on the Analysis of Refrigerating & Air-Conditioning Equipment Industry and Its Forecasting Supervising and Testing for Performance of Refrigerator, Freezer and Air-Conditioner. Prof. Jae-Heon Lee received his B.S. degree in Mechanical Engineering from Seoul National University, Korea, in 1971. He then received his M.S. and Ph. D. degree from Seoul National University in 1977 and 1980, respectively. Dr. Lee is currently a Professor at the school of Mechanical Engineering at Hanyang University in Seoul, Korea. Dr. Lee is currently a president at the Korea Institute research interests include simulation of thermal fluid and Plant engineering and construction. Dr. Jun-Young Choi received his B.S. degree in Mechanical Engineering from Yonsei University, Republic of Korea, in 1989. He then received his M.S. and Ph. D. degrees from Yonsei University in 1991 and 1999, respectively. Dr. Choi is currently a chief researcher with the 18 years experience on the energy performance testing of HVAC/R product. He is now assigned to the Energy Technology Center at Basic Industry Division at Korea Testing Laboratory. He has been involved in the development of Design and Manufacturing Technology for Air-Conditioner E.E.R. and Performance Testing Equipment for Cooling and Heating System with Non-CFCs, and natural refrigerants. He has conducted a study on the Analysis of Refrigerating & Air-Conditioning Equipment Industry and Its Forecasting Supervising and Testing for Performance of Refrigerator, Freezer and Air-Conditioner. Dr. Sang Jae Lee received his Ph.D. degree in Mechanical Engineering from Hanyang University, KOREA, in 2008. Dr. Lee is currently a Researcher at the Korea Institute of Industrial Technology in Cheonan, Korea. Dr. Lee’s research interests CO₂ heatpump system, liquid desiccant air conditioning system and Micro heat exchanger.     

A series solution for spatially coupled deflection analysis of thin-walled Timoshenko curved beam with and without elastic foundation

The exact solutions for the spatially coupled deflection and the normal stress at an arbitrary location of a crosssection of the thin-walled Timoshenko curved beam with symmetric and non-symmetric cross-sections with and without two types of elastic foundations are newly presented using series solutions for the displacement parameters. The equilibrium equations and the force-deformation relations are derived from the elastic strain energy including the effects of shear deformation and the axial-flexural-torsional coupling, and the strain energy considering the foundation effects. The explicit expressions for displacement parameters are derived by applying the power series expansions of displacement components to the simultaneous ordinary differential equations. Next, the element stiffness matrix is determined by using the force-deformation relationships. The normal stress at any arbitrary location of the cross-section for a curved beam is evaluated from the stiffness matrix. To verify the validity and the accuracy of this study, the displacements and the normal stresses of curved beams are presented and compared with the analytical solutions, the finite element results using the isoparametric curved beam elements based on the Lagrangian interpolation polynomial, and the detailed three-dimensional analysis results using the shell elements of SAP2000. This paper was recommended for publication in revised form by Associate Editor Maenghyo Cho Nam-Il Kim received his B.S. degree in Civil and Environmental Engineering from Sungkyunkwan University, Korea, in 1996. He then received his M.S. and Ph.D. degrees from Sungkyunkwan University in 1998 and 2004, respectively. Dr. Kim is currently a research professor at Civil and Environmental Engineering at Myongji University in Korea. Dr. Kim’s research interests include stability and vibration of steel and composite structures. Dong Ku Shin received his B.S. and M.S. degrees in Civil Engineering from Seoul National University, Korea, in 1983 and 1985, respectively. He then received his Ph.D. degree from Virginia Tech. at Blacksburg, VA, USA, in 1990. Dr. Shin is currently a professor of Civil and Environmental Engineering Department at Myongji University in Korea. Prof. Shin’s research interests include LRFD design of steel bridges and stability of composite structures.     

Receding horizon tracking control for wheeled mobile robots with time-delay

In this paper, a receding horizon (RH) controller is developed for tracking control of wheeled mobile robots (WMRs) subject to nonholonomic constraint in the environments without obstacles. The problem is simplified by neglecting the vehicle dynamics and considering only the steering system. First, the tracking-error kinematic model is linearized at the equilibrium point. And then, it is transferred to an exact discrete form considering the time-delay. The control policy is derived from the optimization of a quadratic cost function, which penalizes the tracking error and control variables in each sampling time. The minimizing problem is solved by using the QP (quadratic programming) method taking the current error state as the initial value and including the velocity constraints. The performance of the control algorithm is verified via the computer simulations with several different predefined trajectories showing that the strategy is feasible. This paper was recommended for publication in revised form by Associate Editor Doo Yong Lee Kil To Chong (M’96) received the Ph.D. degree in mechanical engineering from Texas A&M University, College Station, in 1995. Currently, he is a Professor at the School of Electronics and Information Engineering, Chonbuk National University, Jeonju, Korea, and Head of the Mechatronics Research Center granted from the Korea Science Foundation. His research interests are in the areas of motor fault detection, network system control, time-delay systems, and neural networks. Chang Goo Lee was born in Chonju, South Korea on Dec., 1958. He received the B.S. and M.S., and Dr.Eng. degrees in Electrical Engineering from Chonbuk National University, South Korea, 1981, 1983 and 1990 respectively. He had been with ETRI as a senior researcher from 1983 to 1991. Since 1992, He has been with the School of Electronic and Information Engineering, Chonbuk National University where he is presently a Professor. His research interests include intelligent control, nonlinear control, and home network control. Yu Gao received the master’s degree in Electronics and Information from Chonbuk National University, Korea, in 2008. He got his bachelor’s degree in Physics from Soochow University, China, in 2005. Currently, he is a Ph.D. candidate in the School of Electronics and Information, Chonbuk National University, Korea. His research interests are in the area of the receding horizon control.     

Nondestructive testing and crack evaluation of ferromagnetic material by using the linearly integrated hall sensor array

Magnetic flux leakage testing (MFLT), which measures the distribution of a magnetic field on a magnetized specimen by using a magnetic sensor such as a Hall sensor, is an effective nondestructive testing (NDT) method for detecting surface cracks on magnetized ferromagnetic materials. A scan-type magnetic camera, based on the principle of MFLT, uses an inclined Hall sensor array on a printed circuit board (PCB) to detect small cracks at high speed. However, the wave forms appear in a direction perpendicular to the scan because the sensors are bonded at different gradients and heights on the PCB despite careful soldering. In this paper, we propose linearly integrated Hall sensors (LIHaS) on a wafer to minimize these waves and to improve the probability of crack detection. A billet specimen is used to determine the effectiveness of the LIHaS in multiple crack detection. This paper was recommended for publication in revised form by Associate Editor Joo Ho Choi Prof. Jinyi Lee was born in Korea in 1968. He received the bachelor degree in mechanical design from Chonbuk University, Jeonju, Korea, in 1992. Also he received the master and Ph.D degree in mechanical and aeronautics & space engineering from Tohoku university, Sendai, Japan, in 1995 and 1998, respectively. He was a Researcher from 1998 to 2000 with the Tohoku university, Iwate university, Iwate Techno-Foundation and Saitama university, Japan. From 2000 to 2003, he worked for Lacomm Co., Ltd. and Gloria Techniques, Korea, as a researcher. In 2003, he was a lecturer with the Chosun university, Gwangju, Korea. Since 2005, he has been an Assistance Professor, Chosun university. His research interests are in application of magneto-optical film, laser and CCD line scan sensor, and development of magnetic camera. He is the author or coauthor of fifteen patents and over 50 scientific papers. Jiseong Hwang was born in Republic of Korea in 1979. He received the B.S and M.S degree in control and instrumentation engineering in 2005 and 2006, respectively, from the Chosun University, Gwangju, korea, where he is currently working toward the Ph.D. degree. His research interests are NDT and Evaluation, Magnetic camera. Jongwoo Jun was born in Korea in 1974. He received the bachelor degree in electronics engineering from Inje University, Kimhae, Korea, in 1999. He received the master degree in electronics engineering from Changwon University, Changwon, Korea, in 2005. Also he is currently working toward the Ph.D. degree in information & communication engineering from Chosun University, Gwangju, Korea. He worked for Lacomm Co., Ltd. and Gloria Techniques from 1999 to 2005, Korea, as a researcher. His research interests are development of magnetic camera, NDT and evaluation. Dr. Seho Choi was born in Korea in 1964. He received bachelor degree in the department of electrical and electronic engineering from Kyungpook National University, Daegu, Korea, in 1987. And he received master degree in the department of elec trical and electronic engineering from Korea Advanced Institute of Science and Technology in 1989. He received Ph.D. degree in the department of electrical and electronic engineering from the University of Sheffield in the U.K. in 2001. He had been worked for Agency for Defense Development as a Researcher from 1989 to 1992, Korea. Since 1993, he has been worked for POSCO Research Lab. as a principal researcher. His main research activities are developing Surface Defect Inspection System for hot and cold rolled steel strip, hot wire rod, and hot slab. He is also interested in developing Internal Defect Detection System for steel products by using Ultra-sonic and magnetic camera techniques. His major is image processing to detect tiny defect in high background noise image. He published many scientific papers as the author or coauthor.     

Development of a guiding system and visual feedback real-time controller for the high-speed self-align optical cable winding

Recently, the demand for the optical cable has been rapidly growing because of the increasing number of internet users and the high speed internet data transmission required. But the present optical cable winding systems have some serious problems such as pile-up and collapse of cables usually near the flange of the bobbin in the process of cables winding. To reduce the pile-up collapse in cable winding systems, a new guiding system is developed for a high-speed self-align cable winding. First, mathematical models for the winding process and bobbin shape fault compensation were proposed, the winding mechanism was analyzed and synchronization logics for the motions of winding, traversing, and the guiding were created. A prototype cable winding systems was manufactured to validate the new guiding system and the suggested logic. Experiment results showed that the winding system with the developed guiding system outperformed the system without the guiding system in reducing pile-up and collapse in high-speed winding. This paper was recommended for publication in revised form by Associate Editor Dae-Eun Kim Chang-woo Lee received a B.S. degree in Mechanical Engineering from Konkuk University in 2001. He received his M.S. and Ph.D. degrees from Konkuk university in 2003 and 2008, respectively. Dr. Lee is currently a researcher at the Flexible Display Roll to Roll Research Center at Konkuk University in Seoul, Korea. Dr. Lee’s research interests are in the area of fault tolerant control, R2R e-Printing line design, and tension-register control. He is the holder of several patents related to R2R e-Printing system. HyanKyoo Kang received the B.S. and M.S degree in 2000 and 2003 respectively from Konkuk University, Seoul, Korea, where he is currently working toward the Ph.D. degree in mechanical design. He took part in the development of an autoalign guiding system for high-speed winding in a cable winding system, a 3-D roll-shape diagnosis method in a steel rolling system, a design of register controller for high-speed converting machine and real-time control design of electronic printing machine. His research topics include register modeling and control for printed electronics and distributed real-time control. Kee-Hyun Shin (S’81-M’02) received the B.S. degree from Seoul National University, Seoul, Korea, and the M.S. and Ph.D. degrees in mechanical engineering from Oklahoma State University (OSU), Still-water. Since 1992, he has been a Professor with the Department of Mechanical and Aerospace Engineering, Konkuk University, Seoul, Korea. For more than 18 years, he has covered several research topics in the area of web handling, including tension control, lateral dynamics, diagnosis of defect rolls/rollers, and fault-tolerant real-time control in the Flexible Display Roll-to-Roll Research Center, Konkuk University, of which he has also been a Director. His research topics include distributed real-time control, embedded control, monitoring, and diagnosis and fault-tolerant control of large-scale systems such as steel plants, film-and-paper-making plants, aircraft, ships, and ubiquitous control of multirobot systems. He is the author of Tension Control (TAPPI Press, 2000) and is the holder of several patents related to R2R e-Printing system.     

An improved model-based predictive control of vehicle trajectory by using nonlinear function

A new model-based predictive control algorithm for vehicle trajectory control is proposed by using vehicle velocity and sideslip angle. Based on the error function combined with vehicle velocity and side slip of a bicycle model, a predictive control method has been proven to be useful on low velocity. Thus, it could be applied for an autonomous vehicle without a driver. Although an autonomous robot is not necessary to be driven with a high velocity, a commercial vehicle has to be driven at high velocity. Thus the previous predictive control formulation is not enough for a commercial driving system. This study is proposed to enhance the capacity of the predictive controller for rather high speed vehicles. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Mr. Jeong-Han Lee is pursuing a Ph.D. degree in Mechanical Engineering at Pusan National University under the supervision of professor Wan-Suk Yoo. His research interests are focused on the area of adaptive control using multibody dynamics. Dr. Wan-Suk Yoo received his Ph.D. degree in 1985 from the University of Iowa. In 1994, he became a full professor at the Pusan National University, and he was selected an ASME fellow. He is serving as a vicepresident of the KSME.     

Hydraulic transport of sand-water mixtures in pipelines Part I. Experiment

The hydraulic transport characteristics of sand-water mixtures in circular and square pipelines are experimentally investigated by changing the Reynolds number and volumetric delivered concentration. The hydraulic gradients are increased along with the Reynolds number. When the mean velocity is larger than the critical velocity, the hydraulic gradient of sand-water mixture in the square duct is larger than that in the circular pipe. The deposition-limit velocity in the square duct is smaller than that in the circular pipe. Thus, it can be concluded that the square duct transports sands more effectively than the circular pipe in a low operating range of velocity. The empirical correlation between the hydraulic gradient and the Reynolds number is obtained. It is believed that the present data and empirical equation can be used to validate the numerical methods developed for the analysis of the transport characteristics of slurry in the circular and square pipelines. This paper was recommended for publication in revised form by Associate Editor Jun Sang Park Chang-Hee Kim received a B.S. degree in Mechanical Engineering from Hanyang University in 1985. He then went on to receive his M.S. degrees from Hanyang University in 1994. Mr. Kim has joined Hyundai Engineering and Construction Company after his degree and is currently working for Oil & Gas Plant as a Procurement Manager. Man-Soo Lee received his M.S. and Ph.D. degrees from civil eng. dept. of Seoul National University in 1992 and 2004, respectively. He has joined Hyundai Engineering and Construction company since 1991 as a research engineer. Recently assisting a big dredging & reclamation project of Hyundai near Incheon Airport in Korea, he is responsible for the geotechnical researching team of civil engineering division at Hyundai Institute of Construction Technology. Cheol-Heui Han received a B.S. degree in Mechanical Engineering from Hanyang University in 1993. He received his M.S. and Ph.D. degrees from Hanyang University. in 1998 and 2003, respectively. Then, he worked as a visiting post-doctoral researcher at the Dept. of Aerospace and Ocean Engineering at Virginia Tech, USA. Dr. Han is currently a Assistant Professor at the Department of Aeronautical and Mechanical Design Engineering. Dr. Han’s research interests are in the area of biomimetics, aircraft and turbomachine design.     

Implementation of frequency-shaped tip reference in conjunction with learning controller for improved tip-tracking control

In the flexible manipulator control, tip-tracking control of flexible manipulator results in non-colocated control problem, which has a non-minimum phase dynamic characteristic. The level of tip-tracking performance in the non-colocated control system depends on the characteristics of the tip reference trajectory to be followed, as well as on the characteristics of the flexible manipulator system itself. In a previous research the use of a tip reference trajectory, filtered by a properly designed time-delay command shaping filter, has been proposed and a multirate repetitive learning control (MRLC) has been used as the tip-tracking controller. The practical implementation of this approach, however, requires estimation of the tip position, which is not easy to obtain. In this paper, a practical implementation of the approach is considered and the tip position is estimated with a fourth-order Kalman filter. The experimental results show that, with the use of Kalman filter, the proposed scheme results in a drastic reduction in residual tip vibrations and the required actuation effort. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Joo Han Park received his B.S. and M.S. degrees in mechanical engineering from the Kyung Hee Univ., Korea, in 2005 and 2007, respectively. He is currently a Ph.D. candidate in Kyung Hee Univ., Korea. His research interests include robotics and vibration control. Soon Geul Lee received his B.S. degree in Mechanical Engineering from Seoul National Univ. in 1983 and M.S. degree from KAIST in 1985. He received his Ph.D. degree in mechanical Engineering from U. of Michigan, Ann Arbor in 1992. He is currently a Professor at the Dept. of Mechanical Engineering in Kyung Hee Univ., Korea. Sungsoo Rhim received his B.S. and M.S. degrees in Mechanical Engineering from Seoul National Univ., Korea, in 1990 and 1992, respectively. He received his Ph.D. degree in mechanical engineering from Georgia Institute of Technology in 2000. He is currently an Assistant Professor at the Dept. of Mechanical Engineering in Kyung Hee Univ., Korea.     

Parameter study for a dimple location in a space grid under the critical impact load

The spacer grid assembly, an interconnected array of slotted grid straps embossed with dimples and springs, is one of the main structural components of a pressurized light-water reactor (PWR). It takes the role of supporting the nuclear fuel rods which experience a severe expansion and contraction caused by harsh operational conditions such as an earthquake. The external load by an earthquake can be mainly represented as a lateral load, and the resistance to it is evaluated in terms of dynamic crush strengths. It has been reported that a dimple location in a space grid has an effect on this strength. In this paper, based on this fact, the effect of a dimple location in a 3×3 support grid on impact strength has been investigated as a preliminary parameter study for a full sized support grid. The optimal location of the dimple, about 3.5 mm from the tip of the strap, has been found and some design guidelines for a support grid such as reducing the spring length and the dimple gap have been provided. This paper was recommended for publication in revised form by Associate Editor Heoung-Jae Chun Keenam Song received his B.S. degree in the department of mechanical engineering from Seoul National University in 1980, then went on to receive his M.S. degree at KAIST in 1982. Since then he has served as a researcher, senior researcher, principal researcher, and project manager at Korea Atomic Energy Research Institute. Soobum Lee is a postdoctoral research associate in the University of Maryland, U.S. He received the B.S. degree in Mechanical Design and Production Engineering from Yonsei University, Seoul, Korea, in 1998, and the M.S. and Ph.D. degree in Mechanical Engineering from KAIST (Korea Advanced Institute of Science and Technology), Korea, in 2000. His main research interests include structural shape and topology optimization, energy harvester design, nuclear plant design for hydrogen production, robust design using Taguchi method, genetic algorithm, automobile part and system design. He received the best paper award from Korean Society of Mechanical Engineering in 2007.     

Development of rapid mixing fuel nozzle for premixed combustion

Combustion in high-preheat and low oxygen concentration atmosphere is one of the attractive measures to reduce nitric oxide emission as well as greenhouse gases from combustion devices, and it is expected to be a key technology for the industrial applications in heating devices and furnaces. Before proceeding to the practical applications, we need to elucidate combustion characteristics of non-premixed and premixed flames in high-preheat and low oxygen concentration conditions from scientific point of view. For the purpose, we have developed a special mixing nozzle to create a homogeneous mixture of fuel and air by rapid mixing, and applied this rapidmixing nozzle to a Bunsen-type burner to observe combustion characteristics of the rapid-mixture. As a result, the combustion of rapid-mixture exhibited the same flame structure and combustion characteristics as the perfectly prepared premixed flame, even though the mixing time of the rapid-mixing nozzle was extremely short as a few milliseconds. Therefore, the rapid-mixing nozzle in this paper can be used to create preheated premixed flames as far as the mixing time is shorter than the ignition delay time of the fuel. This paper was recommended for publication in revised form by Associate Editor Ohchae Kwon Masashi Katsuki received his B.E. degree in Mechanical Engineering from Osaka University, Japan, in 1965. He received his Dr. Eng. from O. U. in 1985. Dr. Katsuki is currently a Visiting Professor at the Department of Environmental Engineering at Hoseo University in Chungnam, Korea. He was a Vice President of the Japan Society of Mechanical Engineers. Dr. Katsuki’s research interests include combustion, computational thermo-fluid dynamics, and molecular dynamics. Jin-Do Chung received his B. S., M.S. and Ph.D. degrees in Mechanical Engineering from Chungnam University, Korea in 1983, 1985 and 1990. He then received another Ph.D. in Environmental Engineering from Kanazawa University, Japan in 1996. After that he worked as Post-doc researcher for 1,6 year at KIMM and Senior researcher for 6years at KEPCO Research Center. Dr. Chung is currently a Professor at the Department of Environmental Engineering at Hoseo University in Asan, Korea. Dr. Chung’s research interests include thermal-fluid and environmental engineering. Jang-Woo Kim received his B. S. degree in Mechanical Engineering from Chungnam University, Korea, in 1990. He then received his M. S. and Ph. D. degrees from Kyushu University, Japan in 1994 and 1998, respectively. Dr. Kim is currently a Professor at the School of Display Engineering at Hoseo University in Asan, Korea. Dr. Kim’s research interests include CFD, aerodynamics, and display equipment technology. Seung-Min Hwang received the Ph.D. degree in Mechanical Engineering at Osaka University in 2005. After that he worked as visiting researcher for 3 years at CRIEPI (central research institute of electric power industry) and Osaka University in Japan. He is currently a Professor at the Graduate School of Venture at Hoseo University in Korea. His major research is thermal-fluid, energy issue and environment. Seung-Mo Kim received his Ph. D. degrees in Mechanical engineering from Osaka University, Japan, in 2004. Dr. Kim is currently a research Professor at Pusan Clean Coal Center at Pusan National University in Pusan, South Korea. Dr. Kim’s research interests include coal combustion, oxy-fuel combustion, coal gasification, coal de-watering, power generation plant system and energy issues. Chul-Ju Ahn received his B.S. degree in Mechanical Engineering from Hanyang University, Korea, in 1998. He then received his M.S. and Ph.D. degrees from Osaka University, Japan, in 2001 and 2006, respectively. Dr. Ahn is currently a Senior Research Engineer at Samsung Techwin CO. LTD. in Changwon, Korea. Dr. Ahn’s research interests include gas turbine engine, biomass gasification, and power system.     

Application of averaging bidirectional flow tube for measurement of single-phase flow rate in a piping system

A new instrument, an averaging bidirectional flow tube (BDFT), is proposed to measure single-phase flow rates. This averaging BDFT has unique measuring characteristics foremost among which is the capability to measure bidirectional flow and insensitivity of the fluid attack angle. Single phase calibration tests were conducted to demonstrate the performance of the averaging BDFT. Likewise, to enhance the applicability of the averaging BDFT on various flow conditions, flow analyses using CFD code were performed focusing on design optimization of the BDFT. The calibration test results indicated that this averaging BDFT has a linearity within 0.5 % in the Reynolds (Re) number range of above 10,000 where it is meaningful in terms of application. The flow analyses results demonstrate a good linearity of the averaging BDFT with various design features. Therefore, averaging BDFT can be applied for measurement of flow rates within a wide range of flow conditions. This paper was recommended for publication in revised form by Associate Editor Won-Gu Joo Kyoung-Ho Kang received his B.S. and M. S. degrees in Nuclear Engineering from SNU (Seoul National University), KOREA in 1993 and 1995, respectively. He then received his Ph.D. degree in Nuclear and Quantum Engineering from KAIST (Korea Advanced Institute of Science and Technology) in 2009. Dr. Kang is currently a senior researcher at the Korea Atomic Energy Research Institute in Daejeon, Korea. Dr. Kang’s research interests include analysis and experiments for the nuclear safety, thermal hydraulics, and experiments and modeling for the severe accidents. Byong-Jo Yun received his B.S. degree in Nuclear Engineering from SNU (Seoul National University), KOREA in 1989. He then received his M.S. and Ph.D. degrees from SNU in 1991 and 1996, respectively. Dr. Yun is currently a principal researcher at the Korea Atomic Energy Research Institute in Daejeon, Korea. Dr. Yun’s research interests include analysis and experiments for the nuclear safety, thermal hydraulics, two-phase flow, scaling analysis, and development of instrumentation for two-phase flow. Dong-Jin Euh received his B.S. degree in Nuclear Engineering from Seoul University, Korea, in 1993. He then received his M.S. and Ph.D. degrees from same university in 1995 and 2002, respectively. Dr. Euh is currently a researcher at thermal hydraulic safety research department of Korea Atomic Energy Research Institute in Daejeon, Korea. Dr. Euh’s research interests include two-phase thermal hydraulics in the Nuclear Systems and Fundamental Phenomena. Won-Pil Baek has been working at KAERI as the general project manager (director) for development of nuclear thermalhydraulic experiment and analysis technology since 2001. He received his B.S. degree in nuclear engineering from Seoul National University and his M.S. and Ph.D. degrees from KAIST. In 1991–2000, he worked for KAIST as a researcher and research professor. Currently he also serves as an executive editor of the Nuclear Engineering and Technology, an international journal of the Korean Nuclear Society. His research interests include critical heat flux, integral effect tests, modeling, nuclear safety, and advanced reactor development.     

A study on the modeling and analysis of a helicopter’s occupant seat belt for crashworthiness

Abstrac  In this paper, a method of modeling a seat belt on a crew seat during a dynamic seat testing was studied. The body segments of the occupant were modeled with joints that consisted of various stiffness, damping, and friction. Three types of seat belt restraint systems were investigated and an analysis on the injury assessment of the helicopter’s crew under a drop impact was conducted. The effectiveness of the seat belt system for crashworthiness and safety was likewise evaluated. From the impact analysis results, it was determined that the head, neck, and spine of the crew body can be easily damaged in the vertical direction more than the longitudinal direction. Based on the verified model, the human body’s behavior was studied using three point restraint systems. The displacement and injury level of the 12-point restraint system was the smallest. This paper was presented at the 4th Asian Conference on Multibody Dynamics(ACMD2008), Jeju, Korea, August 20–23, 2008. Young-Shin Lee received a B.S. degree in Mechanical Engi-neering from Younsei University, Korea in 1972. He received master and Ph.D. degree in Mechanical Engineering from Yonsei University, Korea in 1974 and 1980 respectively. He is currently professor and Dean of Industry Graduate School and Director of BK21 Mechatronics Group at Chungnam National University, Korea. Prof. Lee’s research interests are in area of impact mechanics, optimal design, biomechanical analysis and shell structure analysis. Jung-Hyun Lee received a B.S. degree in Mechanical Design Engineering from Chungnam Na-tional University, Korea in 2007. He received master degree in Mechanical Design Engineering from Chungnam National Uni-versity, Korea in 2009. He is currently researcher of Korea Aerospace Research Institute, Korea. Kyu-Hyun Han received a B.S. degree in Mechanical Design Engineering from Hanbat National University, Korea in 2002. He received master degree in Mechanical Design Engineering from Chungnam National University, Korea in 2004. He is currently researcher of Simuline Inc, Korea.     

On the equivalent mass-spring parameters and assumed mode of a cantilevered beam with a tip mass

In the Rayleigh-Ritz approach to the mathematical model of a cantilevered beam with a tip mass, the proper selection of basis functions is critical in representing the original system by an equivalent mass-spring system. Although the fundamental bending mode shape of a beam varies for a different tip mass magnitude, the numerical values of 33/140 and 3 have been conventionally employed as those of the normalized dimensionless equivalent mass and spring constants, respectively, which correspondingly yield errors in its calculated natural frequencies. This work firstly proposes a method to evaluate more accurate values of the equivalent mass and spring for a wide range of the tip mass-to-beam mass ratio by direct use of a fundamental mode, and then proposes a new basis function as a linear combination of two polynomials, which represent static deflection shapes of a beam under a tip force and a uniformly distributed force, respectively, yielding natural frequencies fairly close to those by the continuous beam equation.     

The Damping Effect on Critical Values of Nonconservative Loads

A systematic study of the effect of energy dissipation on critical nonconservative loads within the stability calculation is carried out. Some classical nonconservative elastic stability problems are considered: the stability of a linear form of equilibrium of a double pendulum under the action of a follower force, the stability of a cantilever beam compressed by a follower force (Beck’s problem), and the stability of a flat panel in a supersonic gas flow. The dependences of critical loads on the damping parameters are built, and the conditions of mechanical system stabilization and destabilization are determined for the cases when damping coefficients vary over a wide range and for various ratios. The external and internal frictions (according to the Voigt model) are considered for the distributed parameter systems. Conclusions about the effect of various types of energy dissipation on the critical values of nonconservative load parameters and about the conditions of nonconservative system destabilization due to the energy dissipation are formulated.     

Vibration and dynamic stability of pipes conveying fluid on elastic foundations

The paper deals with the vibration and dynamic stability of cantilevered pipes conveying fluid on elastic foundations. The relationship between the eigenvalue branches and corresponding unstable modes associated with the flutter of the pipe is thoroughly investigated. Governing equations of motion are derived from the extended Hamilton’s principle, and a numerical scheme using finite element methods is applied to obtain the discretized equations. The critical flow velocity and stability maps of the pipe are obtained for various elastic foundation para-meters, mass ratios of the pipe, and structural damping coefficients. Especially critical mass ratios, at which the transference of the eigenvalue branches related to flutter takes place, are precisely determined. Finally, the flutter configuration of the pipe at the critical flow velocities is drawn graphically at every twelfth period to define the order of the quasi-mode of flutter configuration.     

Analysis of unavoidable geometric errors in the side wall of end-milled parts for corner surface

The location and the size of a geometrically defected region in the side wall of a corner, which is generated during the flat end-milling process, are investigated through experiments and geometrical analysis. A corner with inner and outer surfaces is assumed to be made up of one arc-surface patch and two flat-surface patches. Based on the previous findings that the change of material removal per tooth affects the geometry of the end-milled side wall, it is expected that the geometrically defected regions are located around the corner when the tool is approaching and leaving the arc surface. In this respect, analytic models are proposed to predict the location and the size of a geometrically defected region, which are then validated via comparison with the experimental results. This paper was recommended for publication in revised form by Associate Editor Dae-Eun Kim Kun Sang Lee received his B. S. degree in Mechanical Engineering from Seoul National University, Korea, in 1982. He then received his Dipl.-Ing. and Dr.-Ing. degrees from Technical University of Berlin, Germany, in 1991 and 1993, respectively. Dr. Lee is currently a Professor at the School of Mechanical and Automotive Engineering at Kookmin University in Seoul, Korea. He serves as a Staff of the Korea Engineering Education Research Center. His research interests include precision machining, high energy beam material processing, and creative design methodology. Kang Kim received his B. S. and M. S. degrees in Mechanical Design and Production Engineering from Seoul National University, Korea, in 1982 and 1984, respectively. He then received his Ph.D. degree from Purdue University, USA, in 1992. Dr. Kim is currently a Professor at the School of Mechanical and Automotive Engineering at Kookmin University in Seoul, Korea. His research interests include material removal processes, and concurrent engineering.