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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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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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People Tracking and Accompanying Algorithm for Mobile Robot Using Kinect Sensor and Extended Kalman Filter
Park, Kyoung Jae ; Won, Mooncheol ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 4, 2014, Pages 345~354
DOI : 10.3795/KSME-A.2014.38.4.345
In this paper, we propose a real-time algorithm for estimating the relative position and velocity of a person with respect to a robot using a Kinect sensor and an extended Kalman filter (EKF). Additionally, we propose an algorithm for controlling the robot in the proximity of a person in a variety of modes. The algorithm detects the head and shoulder regions of the person using a histogram of oriented gradients (HOG) and a support vector machine (SVM). The EKF algorithm estimates the relative positions and velocities of the person with respect to the robot using data acquired by a Kinect sensor. We tested the various modes of proximity movement for a human in indoor situations. The accuracy of the algorithm was verified using a motion capture system.
Evaluation of Pressure History due to Steam Explosion
Kim, Seung Hyun ; Chang, Yoon-Suk ; Song, Sungchu ; Hwang, Taesuk ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 4, 2014, Pages 355~361
DOI : 10.3795/KSME-A.2014.38.4.355
Steam explosions can be caused by fuel-coolant interactions resulting from failure of the external vessel cooling system in a new nuclear power plant. This can threaten the integrity of structures, including the nuclear reactor and the containment building. In the present study, an improved technique for analyzing the steam explosion phenomenon was proposed on the basis of previous research and was verified by simulations involving alumina experiments. Also, the improved analysis technique was applied to determine the pressure history of the reactor cavity in accordance with postulated failure locations. The results of the analysis revealed that the effects of vessel side failure are more serious than those of vessel bottom failure, with approximately 70% higher maximum pressure.
Study of the Shape Optimization in Spline FEM Considering both NURBS Control Point Positions and Weights as Design Variables
Song, Yeo-Ul ; Hur, Jun Young ; Youn, Sung-Kie ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 4, 2014, Pages 363~370
DOI : 10.3795/KSME-A.2014.38.4.363
A new NURBS-based shape optimization method is proposed. Most shape optimization studies consider only control point positions as design variables. Some shape optimization processes present problems with mesh quality and convergence when control points are constrained to a limited space. If the weights of the control points are regarded as additional design variables, it should be possible to attain a better degree of shape control. In this study, positions and weights of NURBS control points are used as design variables, and a shape optimization algorithm incorporates position optimization and weight optimization steps. This method is applied to shape optimization benchmarking problems to verify its advantages.
Fabrication and Characteristic Evaluation of Three-Dimensional Blended PCL (60 wt %)/β-TCP (40 wt %) Scaffold
Sa, Min-Woo ; Kim, Jong Young ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 4, 2014, Pages 371~377
DOI : 10.3795/KSME-A.2014.38.4.371
In tissue engineering, a scaffold is a three-dimensional(3D) structure that serves as a template for regeneration the functions of damaged tissues or organs. Among materials for scaffolds, polycaprolactone(PCL) and
-TCP) are biodegradable and biocompatible. In this study, we fabricated 3D PCL, blended PCL (60 wt %)/
-TCP (40 wt %), and pure
-TCP scaffolds by a multi-head scaffold fabrication system. Scaffolds with a pore size of
was observed by scanning electron microscopy. The effects of 3D PCL, blended PCL (60 wt %)/
-TCP (40 wt %) and pure
-TCP scaffolds were analyzed by evaluating their mechanical characteristics. In addition, in an in-vitro study using osteoblast-like saos-2 cells, we confirmed the effects of 3D scaffolds on cellular behaviors such as cell adhesion and proliferation. In summary, the 3D blended PCL (60 wt %)/
-TCP (40 wt %) scaffold was found to be suitable for human cancellous bone in terms of its the compressive strength, biocompatibility, and osteoconductivity. Thus, blending PCL and
-TCP could be a promising approach for fabricating 3D scaffolds for effective bone regeneration.
Shape Optimization and Reliability Analysis of the Dovetail of the Disk of a Gas Turbine Engine
Huh, Jae-Sung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 4, 2014, Pages 379~384
DOI : 10.3795/KSME-A.2014.38.4.379
The most critical rotating parts of a gas turbine engine are turbine blades and disc, given that they must operate under severe conditions such as high turbine inlet temperature, high speeds, and high compression ratios. Owing to theses operating conditions and high rotational speed energy, some failures caused by turbine disks and blades are categorized into catastrophic and critical, respectively. To maximize the margin of structural integrity, we aim to optimize the vulnerable area of disc-blade interface region. Then, to check the robustness of the obtained optimized solution, we evaluated structural reliability under uncertainties such as dimensional tolerance and fatigue life variant. The results highlighted the necessity for and limitations of optimization which is one of deterministic methods, and pointed out the requirement for introducing reliability-based design optimization which is one of stochastic methods. Thermal-structural coupled-filed analysis and contact analysis are performed for them.
Simulation of Rollover Crashes and Passenger Injury Assessment for a Wheeled Armored Vehicle
Lee, Gyung-Soo ; Jung, Ui-Jin ; Park, Gyung-Jin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 4, 2014, Pages 385~391
DOI : 10.3795/KSME-A.2014.38.4.385
A wheeled armored vehicle is a military vehicle that has been developed to enhance combat capabilities and mobility for the army. The wheeled armored vehicle has a high center of gravity, and it operates on unpaved and sloped roads. Therefore, this vehicle has a high risk of rollover crashes. To design the interior of the military vehicle, the crew's safety during rollover crashes is an important factor. However, actual vehicle tests for design are extremely expensive. In this paper, nonlinear dynamic analysis is performed to simulate the rollover crashes and the passenger injury is assessed for a wheeled armored vehicle. The scope of this research is the rollover condition, FE modeling of the wheeled armored vehicle and the dummy, arrangement of dummies, assessment of passenger injuries, and simulation model for rollover crashes.
The Development of the Automatic Transmission for Bicycle Using Internally Geared Hub
Lee, Man Ho ; Choi, Jun Ho ; Lee, Kun Sang ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 4, 2014, Pages 393~400
DOI : 10.3795/KSME-A.2014.38.4.393
In this study, an automatic transmission was developed for a bicycle. This transmission uses the pedal rpm and riding speed information for efficient riding. This transmission was installed on a bicycle using an internally geared hub. The automatic transmission was developed for a beginner to ride with proper gear changes. Indoor ride tests were performed to assess the performance of this transmission. Here, a 'beginner' is defined as a bicycle rider who can maintain a riding power of ~150W with a maximum heart rate of ~80%. Furthermore, 'ride with proper gear change' means that the rider could ride the bicycle while maintaining an efficient pedal rpm by the automatic transmission. One expert and four beginners participated in the ride test. The expert was chosen for the comparison with the beginners. To minimize environmental disturbances, the ride test was performed indoors. In this test, two types of gear changes manual and automatic were tested on two types of roads a road with a gradual incline of 0-3% and a road that simulates the bicycle road along the Han river in Seoul. The results of the ride tests show that the algorithm applied for the automatic transmission helps beginners to ride the bicycle efficiently.
A Study on the Effect of Cohesive Laws on Finite Element Analysis of Crack Propagation Using Cohesive Elements
Seo, Hyeong-Seok ; Baek, Hyung-Chan ; Kim, Hyun-Gyu ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 4, 2014, Pages 401~407
DOI : 10.3795/KSME-A.2014.38.4.401
In this paper, the effect of cohesive laws on the finite element analysis of crack propagation using cohesive elements is investigated through three-point bending and double cantilever beam problems. The cohesive elements are implemented into ABAQUS/Standard user subroutines(UEL), and the shape of cohesive law is varied by changing parameters in polynomial functions of cohesive traction-separation relations. In particular, crack propagation behaviors are studied by comparing load-displacement curves of the analysis models which have different shapes of cohesive laws with the same values of fracture energy and cohesive strength. Furthermore, the influence of the element size on crack propagation is discussed in this study.
3D Analysis of Crack Growth in Metal Using Tension Tests and XFEM
Lee, Sunghyun ; Jeon, Insu ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 4, 2014, Pages 409~417
DOI : 10.3795/KSME-A.2014.38.4.409
To prevent the occurrence of fractures in metal structures, it is very important to evaluate the 3D crack growth process in those structures and any related parts. In this study, tension tests and two simulations, namely, Simulation-I and Simulation-II, were performed using XFEM to evaluate crack growth in three dimensions. In the tension test, Mode I crack growth was observed for a notched metal specimen. In Simulation-I, a 3D reconstructed model of the specimen was created using CT images of the specimen. Using this model, an FE model was constructed, and crack growth was simulated using XFEM. In Simulation-II, an ideal notch FE model of the same geometric size as the actual specimen was created and then used for simulation. Obtained crack growth simulation results were then compared. Crack growth in the metal specimen was evaluated in three dimensions. It was shown that modeling the real shape of a structure with a crack may be essential for accurately evaluating 3D crack growth.
Finite Element Analysis of CFRP Frame under Launch and Recovery Conditions for Subsea Walking Robot, Crabster
Yoo, Seong-Yeol ; Jun, Bong-Huan ; Shim, Hyungwon ; Lee, Pan-Mook ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 4, 2014, Pages 419~425
DOI : 10.3795/KSME-A.2014.38.4.419
This study applied finite element analysis (FEA) to the body frame of the 200-meter class multi-legged subsea walking robot known as Crabster (CR200). The body frame of the CR200 is modeled after the ribcage of a human so that it can disperse applied external loads. It is made of carbon-fiber-reinforced plastic (CFRP). Therefore, the frame is lighter and stronger than it would be if it were made of other conventional materials. In order to perform FEA for the CFRP body frame, we applied the material properties of the CFRP as obtained from a specimen test to an FE model of CFRP frame. Finally, we performed FEA with respect to the load conditions encountered when the robot is launched into and recovered from the sea. Also, we performed FEA for the frame, assuming that it was fabricated using a conventional material, in order to compare its characteristics with CFRP.
Estimation of Hardfacing Material and Thickness of STD61 Hot-Working Tool Steels Through Three-Dimensional Heat Transfer and Thermal Stress Analyses
Park, Na-Ra ; Ahn, Dong-Gyu ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 4, 2014, Pages 427~436
DOI : 10.3795/KSME-A.2014.38.4.427
The goal of this paper is to estimate proper hardfacing material and thickness of STD61 hot-working tool steel through three-dimensional heat transfer and thermal stress analyses. Stellite6, Stellite21 and 19-9DL superalloys are chosen as alternative hardfacing materials. The influence of hardfacing materials and thicknesses on temperature, thermal stress and thermal strain distributions of the hardfaced part are investigated using the results of the analyses. From the results of the investigation, it has been noted that a hardfacing material with a high conductivity and a thinner hardfaced layer are desired to create an effective hardfacing layer in terms of heat transfer characteristics. In addition, it has been revealed that the deviation of effective stress and principal strain in the vicinity of the joined region are minimized when the Stellite21 hardfaced layer with the thickness of 2 mm is created on the STD61. Based on the above results, a proper hardfacing material and thickness for STD61 tool steel have been estimated.
Fatigue Life Evaluation of Turbine Shaft Using Applied Shaft Stress
Jin, Byeong Kyou ; Park, Ki Beom ; Chai, JangBom ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 4, 2014, Pages 437~442
DOI : 10.3795/KSME-A.2014.38.4.437
The equipment or with a constant torque and a variable stress due to axial vibration such as the turbine-generator system in nuclear power plant show the fatigue fracture behavior. Thus this study whoul aim to measure the torsional stress and analyze the fatigue fracture behavior. To achieve this, we manufactured the equipment similar with turbine-generator system and applied various torsional vibration stress due to external load. In particular, the evaluation was conducted with the existing evaluation methods of the fatigue behavior of known stress-life, strain-life, crack growth assessment methods. With increasing the external load and independent methods tends to decrease the fatigue life was confirmed up to 10 times in 5 kV external load compared to without external load.
Development of Disassembly Tool for Intermediate Examination of Nuclear Fuel Rods
Hong, Jintae ; Heo, Sung-Ho ; Kim, Ka-Hye ; Park, Sung-Jae ; Joung, Chang-Young ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 4, 2014, Pages 443~449
DOI : 10.3795/KSME-A.2014.38.4.443
To check the characteristics of nuclear fuels during an irradiation test, the nuclear fuel rod needs to be disassembled from the test rig located in the pool of the research reactor. Then, the disassembled fuel rod is delivered to the hot cell for intermediate examination. A fuel rod that passes the intermediate examination is delivered to the reactor pool to be reassembled into the test rig. The irradiation test is resumed with the reassembled test rig. Because nuclear fuel rods irradiated by neutrons are highly radioactive, all the disassembly and reassembly processes should be carried out in the pool of the research reactor to prevent operators being exposed to radiation. In particular, because a test rig is 5.4-m long and the reactor pool of HANARO is 6-m deep, special tools need to be developed for performing the disassembly and reassembly processes. In this study, a new assembly design of nuclear fuel rods for intermediate examination is introduced. Furthermore, tools for treating the irradiated fuel rod assembly are introduced, and their performance is verified by an out pile test.
Evaluation of the Structure Stability of a Plate Girder Bridge Using MIDAS Structure Analysis
Kim, Eui Soo ; Kim, Jong Hyuk ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 4, 2014, Pages 451~457
DOI : 10.3795/KSME-A.2014.38.4.451
Recently, as a means of resolving the issue of legal liability in the event of an accident or a disaster, a wide variety of simulation techniques, such as structural and structure-fluid interaction analysis, have been used in the field of forensic engineering. The plate girder bridge discussed in this paper was being constructed between a pier and an abutment to expand an existing bridge, but an accident whereby the bridge overturned occurred at the end of the concrete laying process for a protective wall. This accident was caused by additional loads not being considered at the time of the design as well as the actual construction being different from the design. The additional loads ultimately generated a negative support force. In this study, we determined the cause of the accident by comparing the structural stability of the original design with that of the additional, non-conforming construction using MIDAS structural analysis.
Design of a Helmholtz Resonator for Noise Reduction in a Duct Considering Geometry Information: Additional Relationship Equation and Experiment
Ryu, Hokyung ; Chung, Seong Jin ; Lee, Jin Woo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 4, 2014, Pages 459~468
DOI : 10.3795/KSME-A.2014.38.4.459
An additional relationship equation is numerically obtained to increase the accuracy of the conventional equation for obtaining the resonant frequency of a resonator. Although the conventional equation is widely used in industry because of its simplicity, it does not provide enough information on the cavity or the neck of the resonator for noise reduction in a duct. Resonator designers have difficulty implementing resonator design owing to the uncertainty in geometry presented by the well-known formula for determining the resonant frequency. To overcome this problem, this work determines an approximate equation using results of numerical calculation. To this end, shape parameters of the neck and cavity of a resonator are defined, and an equation describing the relationship between them is derived by adjusting the peak frequency in the transmission loss curve of a resonator to its resonant frequency. The application and validity of the derived equation are investigated in a numerical simulation and an acoustic experiment, respectively.