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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 37, Issue 12 - Dec 2013
Volume 37, Issue 11 - Nov 2013
Volume 37, Issue 10 - Oct 2013
Volume 37, Issue 9 - Sep 2013
Volume 37, Issue 8 - Aug 2013
Volume 37, Issue 7 - Jul 2013
Volume 37, Issue 6 - Jun 2013
Volume 37, Issue 5 - May 2013
Volume 37, Issue 4 - Apr 2013
Volume 37, Issue 3 - Mar 2013
Volume 37, Issue 2 - Feb 2013
Volume 37, Issue 1 - Jan 2013
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Small-Sized Variable Stiffness Actuator Module Based on Adjustable Moment Arm
Yu, Hong-Seon ; Song, Jae-Bok ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 10, 2013, Pages 1195~1200
DOI : 10.3795/KSME-A.2013.37.10.1195
In recent years, variable stiffness actuation has attracted much attention because interaction between a robot and the environment is increasingly required for various robot tasks. Several variable stiffness actuators (VSAs) have been developed; however, they find limited applications owing to their size and weight. For realizing their widespread use, we developed a compact and lightweight mini-VSA. The mini-VSA consists of a control module based on an adjustable moment arm mechanism and a drive module with two motors. By controlling the relative motion of cams in the control module, the position and stiffness can be simultaneously controlled. Experimental results are presented to show its ability to change stiffness.
Detectability of Pore Defect in Wind Turbine Blade Composites Using Image Correlation Technique
Kim, Jong Il ; Huh, Yong Hak ; Lee, Gun Chang ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 10, 2013, Pages 1201~1206
DOI : 10.3795/KSME-A.2013.37.10.1201
Defects that occur during the manufacturing process or operation of a wind turbine blade have a great influence on its life and safety. Typically, defects such as delamination, pore, wrinkle and matrix crack are found in a blade. In this study, the detectability of the pores, a type of defect that frequently occur during manufacturing, was examined from the full field strain distribution determined with the image correlation technique. Pore defects were artificially introduced in four-ply laminated GFRP composites with
fiber direction. The artificial pores were introduced in consideration of their size and location. Three different-sized pores with diameter of 1, 2 and 3 mm were located on the top and bottom surface and embedded. By applying static loads of 0-200 MPa, the strain distributions over the specimen with the pore defects were determined using image correlation technique. It was found the pores with diameter exceeding 2 mm can be detected in diameter.
Study on Mechanical Parameters of a Wheelset Influencing Derailment of Rolling Stock
Oh, Hyun Sun ; Koo, Jeong Seo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 10, 2013, Pages 1207~1218
DOI : 10.3795/KSME-A.2013.37.10.1207
It is difficult to predict derailment with the existing derailment coefficient like Nadal's formula which is based on the contact forces between one wheel and rail. A new derailment coefficient model developed on a wheelset is able to make a better estimate about the climb derailment, slip derailment, roll over derailment, and mixed derailment types of these. Moreover, not only the mechanical factors considered in the existing derailment coefficients but also other various factors affecting derailment such as wheel unloading and loading, diameter of wheel, and locations of axle-box bearings can be covered with this new derailment coefficient model. That is, the derailment patterns which couldn't be solved with the existing formulas such as Nadal's and Weinstock's models can be analyzed with this wheelset derailment coefficient model because of considering various factors causing derailment. Finally, the validity of the new derailment coefficient model is verified using dynamic model simulations.
Wearable Robot System Enabling Gaze Tracking and 3D Position Acquisition for Assisting a Disabled Person with Disabled Limbs
Seo, Hyoung Kyu ; Kim, Jun Cheol ; Jung, Jin Hyung ; Kim, Dong Hwan ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 10, 2013, Pages 1219~1227
DOI : 10.3795/KSME-A.2013.37.10.1219
A new type of wearable robot is developed for a disabled person with disabled limbs, that is, a person who cannot intentionally move his/her legs and arms. This robot can enable the disabled person to grip an object using eye movements. A gaze tracking algorithm is employed to detect pupil movements by which the person observes the object to be gripped. By using this gaze tracking 2D information, the object is identified and the distance to the object is measured using a Kinect device installed on the robot shoulder. By using several coordinate transformations and a matching scheme, the final 3D information about the object from the base frame can be clearly identified, and the final position data is transmitted to the DSP-controlled robot controller, which enables the target object to be gripped successfully.
A Numerical Approach to Spherical Indentation Techniques for Creep Property Evaluation
Lim, Dongkyu ; Lee, Jin Haeng ; Choi, Youngsick ; Lee, Hyungyil ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 10, 2013, Pages 1229~1237
DOI : 10.3795/KSME-A.2013.37.10.1229
In this study, the theory of spherical indentation based on incremental plasticity is extended to an indentation method for evaluating creep properties. Through finite element analysis (FEA), the point where the elastic strain effect is negligible and the creep strain gradient constant is taken as the optimum point for obtaining the equivalent strain rate and stress. Based on FE results for spherical indentation with various values of creep exponent and creep coefficient, we derive by regression an equation to calculate creep properties using two normalized variables. Finally a program is generated to calculate creep exponent and creep coefficient. With this method, we obtain from the load-depth curve creep exponents with an average error of less than 1.5 % and creep coefficients with an average error of less than 1.0 %.
Development of Test Method for Simple Shear and Prediction of Hardening Behavior Considering the Bauschinger Effect
Kim, Dongwook ; Bang, Sungsik ; Kim, Minsoo ; Lee, Hyungyil ; Kim, Naksoo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 10, 2013, Pages 1239~1249
DOI : 10.3795/KSME-A.2013.37.10.1239
In this study we establish a process to predict hardening behavior considering the Bauschinger effect for zircaloy-4 sheets. When a metal is compressed after tension in forming, the yield strength decreases. For this reason, the Bauschinger effect should be considered in FE simulations of spring-back. We suggested a suitable specimen size and a method for determining the optimum tightening torque for simple shear tests. Shear stress-strain curves are obtained for five materials. We developed a method to convert the shear load-displacement curve to the effective stress-strain curve with FEA. We simulated the simple shear forward/reverse test using the combined isotropic/kinematic hardening model. We also investigated the change of the load-displacement curve by varying the hardening coefficients. We determined the hardening coefficients so that they follow the hardening behavior of zircaloy-4 in experiments.
High-Temperature Design and Integrity Evaluation of Sodium-Cooled Fast Reactor Decay Heat Exchanger
Lee, Hyeong-Yeon ; Eoh, Jae-Hyuk ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 10, 2013, Pages 1251~1259
DOI : 10.3795/KSME-A.2013.37.10.1251
In this study, high temperature design and creep-fatigue damage evaluation of a decay heat exchanger (DHX) in the decay heat removal systems of a sodium-cooled fast reactor (SFR) have been performed. Detail design and 3D finite element analysis have been conducted for the DHXs to be installed in active and passive decay heat removal systems in Korean Generation IV SFR, and the DHX installed in the STELLA-1(Sodium integral effect test loop for safety simulation and assessment) at KAERI (Korea Atomic Energy Research Institute). Evaluations of creep-fatigue damage based on full 3D finite element analyses were conducted for the two Mod.9Cr-1Mo steel heat exchangers according to the elevated temperature design codes of ASME Section III Subsection NH and RCC-MR code. Code comparisons were made based on the creep-fatigue damage evaluation and issues on conservatisms of the design codes were discussed.
Use of Parametric Generalized Coordinates for Kinematic Constraint Formulation of Low Degree-of-Freedom Joints
Lee, Jung Keun ; Lee, Chul Ho ; Bae, Dae Sung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 10, 2013, Pages 1261~1267
DOI : 10.3795/KSME-A.2013.37.10.1261
In multibody mechanical systems, low-degree-of-freedom (DOF) joints such as revolute and translational joints are much more frequently used than high-DOF joints. In order to formulate kinematic constraint equations, especially for low-DOF joints, in an efficient and systematic manner, this paper presents a parametric generalized coordinate formulation as a new approach for describing constraint equations. In the proposed approach, joint constraint equations are formulated in terms of a mixed set of Cartesian and parametric generalized coordinates, which drastically reduces the complexity and computational cost of the partial derivatives of the constraints such as the constraint Jacobian. The proposed formulation is validated using a simple cylinder-crank system with an implicit integrator.
Effects of Cutting Area on Straightness Characteristics in Side Walls Caused by Form Generation Mechanism in End-Milling Process
Kim, Kang ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 10, 2013, Pages 1269~1278
DOI : 10.3795/KSME-A.2013.37.10.1269
The cutting area changes periodically in the end-milling process because of its form generation mechanism. In this study, the effects of the cutting area on end-milled side walls are studied by developing a cutting area model that simulates the area formed by engagement between a workpiece and a cutting edge of the end mill. To do this, the straightness profile of the side wall in the axial direction is investigated. Models for estimating the cutting area and the transition point, where the slope of the straightness profile changes suddenly, are verified from real end-milling experiments under various radial and axial depth of cut conditions. Through this study, it is confirmed that the final end-milled side wall is generated in the regions where cutting areas are constant and decreasing in the down-cut. Similarly, in stable up-cut, it is also generated in the regions where cutting areas are increasing and constant. It is found that the transition point appears when the region changes.
Structural Analysis and Shape Optimization for Rotor of Turbomolecular Pump Using P-Method
Won, Bo Reum ; Jung, Hae Young ; Han, Jeong Sam ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 10, 2013, Pages 1279~1289
DOI : 10.3795/KSME-A.2013.37.10.1279
In recent times, turbomolecular pumps (TMPs) have been used frequently to generate and maintain high and clean vacuum. Because of the high-speed rotation of the rotor, its structural safety should be treated as the first design concern. This paper presents the structural analysis and optimization of rotor blades of a TMP. To increase the numerical efficiency in the finite element modeling and analysis, the P-method provided in Pro/ENGINEER was used for simulation. The structural responses for several types of rotor blades were investigated, and the effects of the blade angle, blade length, and round size are thoroughly studied for each type of TMP blade. In addition, structural optimization to reduce and even the maximum stress at each stage of the TMP by changing the size of rounds between the blade and the hub was performed very successfully by using the P-method.
Prediction of Maintenance Period of Equipment Through Risk Assessment of Thermal Power Plants
Song, Gee Wook ; Kim, Bum Shin ; Choi, Woo Song ; Park, Myung Soo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 10, 2013, Pages 1291~1296
DOI : 10.3795/KSME-A.2013.37.10.1291
Risk-based inspection (RBI) is a well-known method that is used to optimize inspection activities based on risk analysis in order to identify the high-risk components of major facilities such as power plants. RBI, when implemented and maintained properly, improves plant reliability and safety while reducing unplanned outages and repair costs. Risk is given by the product of the probability of failure (POF) and the consequence of failure (COF). A semi-quantitative method is generally used for risk assessment. Semi-quantitative risk assessment complements the low accuracy of qualitative risk assessment and the high expense and long calculation time of quantitative risk assessment. The first step of RBI is to identify important failure modes and causes in the equipment. Once these are defined, the POF and COF can be assessed for each failure. During POF and COF assessment, an effective inspection method and range can be easily found. In this paper, the calculation of the POF is improved for accurate risk assessment. A modified semi-quantitative risk assessment was carried out for boiler facilities of thermal power plants, and the next maintenance schedules for the equipment were decided.
Nonlinear Stress Analysis of Dust Covers for Ball Joint of Automotive Steering System
Kim, Ji Ho ; Lee, Boo Youn ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 10, 2013, Pages 1297~1303
DOI : 10.3795/KSME-A.2013.37.10.1297
A nonlinear finite element analysis is performed to evaluate the sealing capability and stress of dust covers for the ball joint of an automotive steering system. The analysis is performed for two types of dust covers: wrinkle type and pot type. The assembly condition and operation condition are analyzed, and the maximum stress and contact normal stress at the ribs are evaluated. It is confirmed that the sealing capability of both types is fairly good, but the wrinkle type is better than the pot type in terms of the maximum stress.
Simplification of Boundary Representation Models Based on Stepwise Volume Decomposition
Kim, Byung Chul ; Mun, Duhwan ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 10, 2013, Pages 1305~1313
DOI : 10.3795/KSME-A.2013.37.10.1305
In this study, a method to apply feature-based simplification to boundary representation models is proposed. For feature-based simplification, a volume decomposition tree is created from a boundary representation model. The volume decomposition tree is represented by regularized Boolean operations of additive volumes, subtractive volumes, and fillet/round/chamfer volumes, and it is generated by stepwise volume decomposition, which consists of fillet/round/chamfer decomposition, wrap-around decomposition, volume split decomposition, and cell-based decomposition. After the volume decomposition tree is transformed to an infix expression, the CAD model can be simplified by reordering the volumes. To verify the proposed method, a prototype system was implemented, and experiments on test cases were conducted. From the results of the experiments, it is verified that the proposed method is useful for simplifying CAD models based on boundary representation.