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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Transactions of the Korean Society of Mechanical Engineers A
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Journal DOI :
The Korean Society of Mechanical Engineers
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Volume & Issues
Volume 38, Issue 12 - Dec 2014
Volume 38, Issue 11 - Nov 2014
Volume 38, Issue 10 - Oct 2014
Volume 38, Issue 9 - Sep 2014
Volume 38, Issue 8 - Aug 2014
Volume 38, Issue 7 - Jul 2014
Volume 38, Issue 6 - Jun 2014
Volume 38, Issue 5 - May 2014
Volume 38, Issue 4 - Apr 2014
Volume 38, Issue 3 - Mar 2014
Volume 38, Issue 2 - Feb 2014
Volume 38, Issue 1 - Jan 2014
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Unwinding Behavior of and Load Prediction for Protective Tube Around Fiber-Optic Cable
Kim, Kun Woo ; Lee, Jae Wook ; Kim, Hyung Ryul ; Yoo, Wan Suk ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 3, 2014, Pages 235~241
DOI : 10.3795/KSME-A.2014.38.3.235
As a fiber-optic cable is being unwound, it is protected by a tube that is designed to prevent unwinding problems such as tangling and unintentional cutting. In addition, a guide body is separated from the protective tube if a shear pin breaks when the maximum allowable load is exceeded. Therefore, it is important to analyze and predict the unwinding behavior of the protective tube, as well as the load on the shear pin, to enhance the likelihood of a successful operation when laying cables at extreme depths. In this study, the protective tube and the guide body are modeled with particles and are constrained with a constant-length constraint. The load on the shear pin was verified against experimental data, and the unwinding behavior was predicted from the load prediction results.
Experimental Verification of Unwinding Behavior of Fiber-Optic Cable and Prediction of High-Speed Unwinding
Kim, Kun Woo ; Lee, Jae Wook ; Kim, Hyung Ryul ; Yoo, Wan Suk ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 3, 2014, Pages 243~250
DOI : 10.3795/KSME-A.2014.38.3.243
Fiber-optic cables towed by underwater vehicles have an important role in enhancing the mission capability of a mother ship. In general, fiber optic cables are unwound in water for securing unwinding stability and preventing unwinding-related problems. Therefore, in this study, the numerically simulated result is verified against the experimental result in water, and the cable-unwinding motion is predicted based on the increase in unwinding velocity. The experimental apparatus is composed of a water tank and a winder, and a high-speed camera is used for photographing the cable-unwinding motion. The numerical result defined in the Cartesian coordinate system is solved using a transient-state unwinding equation of motion. The numerical result agrees well with the experimental result, and it can predict cable-unwinding behaviors in according to an increase in the unwinding velocity.
Investigation of Cracking Condition during Press Forming of Extruded Aluminum Sheets
Chu, Seok Jae ; Park, Chang Gu ; Cho, Eun Hwa ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 3, 2014, Pages 251~258
DOI : 10.3795/KSME-A.2014.38.3.251
Sunroof tracks are manufactured by press-forming extruded aluminum sheets. During press forming, cracking occurs along the sharply bent edge. The final positions of the punch and die were measured on the section, and their relation to cracking was investigated. Finite element simulation of bending to the final position was done to find the critical strains. Three-point bending tests with different material orientations, hardnesses, bending edge lengths, and bending radii were carried out in the laboratory, and finite element simulation of the three-point bending tests was performed to find the critical strains.
Fatigue Strength of Dental Implant in Simulated Body Environments and Suggestion for Enhancing Fatigue Life
Kim, Min Gun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 3, 2014, Pages 259~267
DOI : 10.3795/KSME-A.2014.38.3.259
Fatigue tests were performed in various simulated body environments reflecting various factors (such as body fluids, artificial saliva) relevant within a living body. First, the fatigue limit under a simulated body environment (artificial saliva) was evaluated and the governing factors of implant fatigue strength were looked into by observing the fracture mode. The fatigue life of an implant decreased in the artificial saliva environment compared with that in the ringer environment. Furthermore, in the artificial saliva environment, the implant fracture mode was fatigue failure of fixture as opposed to the abutment screw mode in the ringer environment. In the fatigue test, corrosion products were observed on the implant in the simulated body environment. A larger amount of corrosion products were generated on the artificial saliva specimen than on the ringer specimen. It is thought that the stronger corrosion activity on the artificial saliva specimen as compared with that on the ringer specimen led to an overall decrease of fatigue life of the former specimen. In the case of the implant with a nitrided abutment screw eliminated hardened layer (TixN), a several times increase in fatigue life is achieved in comparison with tungsten carbide-coated implants.
Numerical Analysis on the Low Noise Designs of Savonius Wind Turbines by Inducing Phase Difference in Vortex Shedding
Kim, Sanghyeon ; Cheong, Cheolung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 3, 2014, Pages 269~274
DOI : 10.3795/KSME-A.2014.38.3.269
In this study, low noise designs for a Savonius wind turbine were numerically investigated. As was reported in our previous study, the harmonic components with a fundamental frequency higher than the BPF were identified as being dominant in the noise spectrum of a Savonius wind turbine, and these components were a result of vortex shedding. On a basis of this observation, an S-shaped blade tip is proposed as a means of reducing the noise generated by small vertical(Savonius) wind turbines. This blade induces phase differences in the shedding vortices from the blades, and thus reduces the noise from the wind turbine. The aerodynamic noise characteristics of the conventional and "S-shaped" Savonius turbines were investigated by using the Hybrid CAA method where the flow field around the turbine is computed using the CFD techniques and the radiated noise are predicted by applying acoustic analogy to the computed flow field data. The degree of noise reduction resulting from the proposed design and its reduction mechanism were confirmed by comparing the predicted noise spectrum of these turbines and the flow characteristics around them.
Particle Size-Dependent Failure Analysis of Particle-Reinforced Metal Matrix Composites using Dislocation Punched Zone Modeling
Suh, Yeong Sung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 3, 2014, Pages 275~282
DOI : 10.3795/KSME-A.2014.38.3.275
Particle-reinforced metal matrix composites exhibit a strengthening effect due to the particle size-dependent length scale that arises from the strain gradient, and thus from the geometrically necessary dislocations between the particles and matrix that result from their CTE(Coefficient of Thermal Expansion) and elastic-plastic mismatches. In this study, the influence of the size-dependent length scale on the particle-matrix interface failure and ductile failure in the matrix was examined using finite-element punch zone modeling whereby an augmented strength was assigned around the particle. The failure behavior was observed by a parametric study, while varying the interface failure properties such as the interface strength and debonding energy with different particle sizes and volume fractions. It is shown that the two failure modes (interface failure and ductile failure in the matrix) interact with each other and are closely related to the particle size-dependent length scale; in other words, the composite with the smaller particles, which is surrounded by a denser dislocation than that with the larger particles, retards the initiation and growth of the interface and matrix failures, and also leads to a smaller amount of decrease in the flow stress during failure.
Trajectory Generation Method with Convolution Operation on Velocity Profile
Lee, Geon ; Kim, Doik ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 3, 2014, Pages 283~288
DOI : 10.3795/KSME-A.2014.38.3.283
The use of robots is no longer limited to the field of industrial robots and is now expanding into the fields of service and medical robots. In this light, a trajectory generation method that can respond instantaneously to the external environment is strongly required. Toward this end, this study proposes a method that enables a robot to change its trajectory in real-time using a convolution operation. The proposed method generates a trajectory in real time and satisfies the physical limits of the robot system such as acceleration and velocity limit. Moreover, a new way to improve the previous method (11), which generates inefficient trajectories in some cases owing to the characteristics of the trapezoidal shape of trajectories, is proposed by introducing a triangle shape. The validity and effectiveness of the proposed method is shown through a numerical simulation and a comparison with the previous convolution method.
Manipulator Equipped with Counterbalance Mechanism Based on Gear Unit
Kang, In Ho ; Kim, Hwi Su ; Song, Jae-Bok ; Lee, Hyun Soo ; Chang, In Sung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 3, 2014, Pages 289~294
DOI : 10.3795/KSME-A.2014.38.3.289
Industrial manipulators are usually heavy given the payloads they carry. Therefore, they require high-capacity servomotors and speed reducers, which leads to high costs. However, if manipulator weight could be compensated for using a counterbalance mechanism, the motors` and speed reducers` capacities could be minimized substantially. However, it is usually difficult to assure durability and reliability with the conventional wire-based counterbalance mechanism. Therefore, a more robust gear- and roller-based counterbalance mechanism is proposed in this study. A manipulator was developed using this mechanism; this manipulator maintains its performance even when using motors and reducers of lower capacities. The results of various simulations and experiments verified that the proposed mechanism provides the torque required to compensate for gravitational torque in any configuration and minimizes the torque required for supporting a large payload.
Optimal Design of Rotor Profile of Internal Gear Pump for Noise Reduction
Bae, Jun Ho ; Bae, Won Byong ; Joo, Ung Tak ; Kim, Chul ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 3, 2014, Pages 295~302
DOI : 10.3795/KSME-A.2014.38.3.295
An internal gear pump is required to improve the flow rate and noise. Furthermore, such pumps are durable and small in size. In this study, equations of the rotor shape with multiple profiles (ellipse 1-involute-ellipse 2) were derived, and relevant performance parameters (pressure angle, irregularity, and specific sliding) of the internal gear pump to noise were predicted and compared. Rotor profiles and performance parameters were obtained by a prediction algorithm for theoretical analysis, and the effects between the design parameters and the performance parameters were analyzed. Based on the analysis results of the effects, an optimal design of the rotor profile was proposed, and a noise test of the prototype was performed to evaluate the reliability of the design.
Stress Analysis of Plate-Spring-Type Landing Gear Materials
Kim, Kyeong-Hwan ; Lee, Young-Shin ; Han, Jae-Do ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 3, 2014, Pages 303~308
DOI : 10.3795/KSME-A.2014.38.3.303
Aircraft are an indispensable mode of modern transportation. They are also used as in a wide variety of other fields. For example, aircraft are used for accommodating passengers, carrying freight, and for military reconnaissance. Aircraft ground operations include landing and taking off. During landing, a higher load is applied to the landing gear than during takeoff. The landing gear should absorb impact energy and prevent damage to the main body of the aircraft in the case of an accident. In this study, simulations were performed for two types of plate-spring-type landing gear: that made of composite materials and that constructed with aluminum. The structural safety of landing gear made of each material was also evaluated.
Topology Optimization of Offshore Wind-Power Turbine Substructure Using 3D Solid-Element Model
Kim, Won Cheol ; Chung, Tae Jin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 3, 2014, Pages 309~314
DOI : 10.3795/KSME-A.2014.38.3.309
The structural layout of mechanical and civil structures is commonly obtained using conventional methods. For example, the shape of structures such as electric transmission towers and offshore substructures can be generated systematically. However, with rapid advancements in computer graphic technology, advanced structural analyses and optimum design technologies have been implemented. In this study, the structural shape of a jacket substructure for an offshore wind turbine is investigated using a topology optimization technique. The structure is subjected to multiple loads that are intended to simulate the loading conditions during actual operation. The optimization objective function is defined as one that ensures compliance of the structure under the given boundary conditions. Optimization is carried out with constraints on the natural frequency in addition to the volume constraint. The result of a first step model provides quick insights into the optimum layout for the second step structure. Subsequently, a 3D model in the form of the frustum of a quadrilateral pyramid is developed through topology optimization.
Integrated Chassis Control System with Fail Safety Using Optimum Yaw Moment Distribution
Yim, Seongjin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 3, 2014, Pages 315~321
DOI : 10.3795/KSME-A.2014.38.3.315
This paper presents an integrated chassis control system with fail safety using optimum yaw moment distribution for a vehicle with steer-by-wire and brake-by-wire devices. The proposed system has two-level structure: upper- and lower-level controllers. In the upper-level controller, the control yaw moment is computed with sliding mode control theory. In the lower-level controller, the control yaw moment is distributed into the tire forces of active front steering(AFS) and electronic stability control(ESC) with the weighted pseudo-inverse based control allocation(WPCA) method. By setting the variable weights in WPCA, it is possible to take the sensor/actuator failure into account. In this framework, it is necessary to optimize the variables weights in order to enhance the yaw moment distribution. For this purpose, simulation-based tuning is proposed. To show the effectiveness of the proposed method, simulations are conducted on a vehicle simulation package, CarSim.
Development of Information Technology for Smart Defense
Chung, Kyo-Il ; Lee, So Yeon ; Park, Sangjoon ; Park, Jonghyun ; Han, Sang-Cheol ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 3, 2014, Pages 323~328
DOI : 10.3795/KSME-A.2014.38.3.323
Recently, there has been demand for the convergence of IT (Information and communication Technologies, ICT) with defense, as has already been achieved in civilian fields such as healthcare and construction. It is expected that completely new and common requirements would emerge from the civilian and military domains and that the shape of war field would change rapidly. Many military scientists forecast that future wars would be network-centric and be based on C4I(Command, Control, Communication & Computer, Intelligence), ISR(Intelligence, Surveillance & Reconnaissance), and PGM(Precision Guided Munitions). For realizing the smart defense concept, IT should act as a baseline technology even for simulating a real combat field using virtual reality. In this paper, we propose the concept of IT-based smart defense with a focus on accurate detection in real and cyber wars, effective data communication, automated and unmanned operation, and modeling and simulation.
Parametric Study of Curved Guideways for Urban Maglev Vehicle
Han, Jong-Boo ; Kim, Ki-Jung ; Han, Hyung-Suk ; Kim, Sung-Soo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 3, 2014, Pages 329~335
DOI : 10.3795/KSME-A.2014.38.3.329
A maglev vehicle of middle-low speed subjected to both a lift force and a guidance force by a U-shaped single electromagnet is operated over a curved guideway without a guidance controller. Therefore, it is required to carefully decide the curve shape for preventing contact between the vehicle and the guiderail for the case that a Maglev vehicle is operated over a curved guideway with a small radius. Specifically, the shape of the transition curve is very important from the stability viewpoint. This study analyzes the influence of curve shape on maglev stability through parametric composition of the transition curve during vehicle guidance. To this end, a multibody dynamics-based threedimensional Maglev vehicle model was developed. The model was integrated with the vehicle, curved guideway, electromagnets, and their controllers. Using this model, a realistic parametric study including the curved guideway was carried out. The results of research should be considered usefully in the design of bogies and the curve shape.
Optimal Shape Design of Pyeongyeong Considering Structural and Acoustical Characteristics
Lee, Seungmok ; Kang, Minseok ; Lee, Jin Woo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 3, 2014, Pages 337~344
DOI : 10.3795/KSME-A.2014.38.3.337
An optimal shape design algorithm is suggested to systematically design a traditional Korean musical instrument, the Pyeongyeong. The Pyeongyeong consists of 16 different chime stones called Gyeongpyeons. The first natural vibration frequency of each Gyeongpyeon must be adjusted to its target frequency, which is determined by the traditional sound tuning method. The second and third natural frequencies must be proportional to the first natural frequency with a specific ratio (1:1.498:2.378). The key idea in our suggested design algorithm is to use the sensitivity of natural frequencies to the variation in the length of each side of a Gyeongpyeon. The dimensions of five different Gyeongpyeons are determined by following the suggested algorithm. Changes in natural frequencies with respect to local thickness variation are closely investigated to compensate for errors that may occur during manufacturing.