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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
Selecting the target year
Trajectory Regeneration Considering Velocity of Dynamic Obstacles Using the Nonlinear Velocity Obstacles
Moon, Chang-Bae ; Chung, Woojin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 11, 2014, Pages 1193~1199
DOI : 10.3795/KSME-A.2014.38.11.1193
To achieve safe and high-speed navigation of a mobile service robot, velocity of dynamic obstacles should be considered while planning the trajectory of a mobile robot. Trajectory planning schemes without considering the velocity of the dynamic obstacles may collide due to the relative velocities or dynamic constraints. However, the general planning schemes that considers the dynamic obstacle velocities requires long computational times. This paper proposes a velocity control scheme by scaling the time step of trajectory to deal with dynamic obstacle avoidance problem using the RNLVO (Robot Nonlinear Velocity Obstacles). The RNLVO computes the collision conditions on the basis of the NLVO (Nonlinear Velocity Obstacles). The simulation results show that the proposed scheme can deal with collision state in a short period time. Furthermore, the RNLVO computes the collisions using the trajectory of the robot. As a result, accurate prediction of the moving obstacles trajectory does not required.
Development of Wheel Loader V-Pattern Operator Model for Virtual Evaluation of Working Performance
Oh, Kwangseok ; Kim, Hakgu ; Ko, Kyungeun ; Kim, Panyoung ; Yi, Kyongsu ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 11, 2014, Pages 1201~1206
DOI : 10.3795/KSME-A.2014.38.11.1201
This paper presents the development of an event-based operator model of a wheel loader for virtual V-pattern working. The objective of this study is to analyze the performance and dynamic behavior of the wheel loader for a typical V-pattern. The proposed typical V-pattern working is divided into four stages. The developed operator model is based on eight events, and the operator's inputs are occurred sequentially by event. A 3D dynamic simulation model of the wheel loader is developed and used to analyze the dynamic behavior during working, and the simulation results are compared with the experimental data of V-pattern working. The proposed 3D dynamic simulation model and operator model are constructed using MATLAB/Simulink. The proposed operator model for V-pattern working is expected to enable evaluation of the working performance and dynamic behavior of the wheel loader.
Crack-tip Stress Field of Fully Circumferential Surface Cracked Pipe Under Combined Tension and Thermal Loads
Je, Jin Ho ; Kim, Dong Jun ; Kim, Yun Jae ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 11, 2014, Pages 1207~1214
DOI : 10.3795/KSME-A.2014.38.11.1207
Under excessive plasticity, the fracture toughness of a material depends on its size and geometry. Under fully yielded conditions, the stresses in a material near its crack tip are not unique but rather depend on the geometry. Therefore, the single-parameter J-approach is limited to a high-constraint crack geometry. The JQ theory has been proposed for establishing the crack geometry constraints. This approach assumes that the crack-tip fields have two degrees of freedom. In this study, the crack-tip stress field of a fully circumferential surface-cracked pipe under combined loads is investigated on the basis of the JQ theory by using finite element analysis. The combined loads are a tensile axial force and the thermal gradient in the radial direction. Q-stresses of the crack geometry and its loading state are used to determine the constraint effects. The constraint effects of secondary loading are found to be greater than those of primary loading. Therefore, thermal shock is believed to be the most severe loading condition of constraint effects.
Optimum Design of Latch Position and Latch Length on Operating Mechanism of a Circuit Breaker using ADAMS and VisualDOC
Cha, Hyun Kyung ; Jang, Jin Seok ; Yoo, Wan Suk ; Sohn, Jeong Hyun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 11, 2014, Pages 1215~1220
DOI : 10.3795/KSME-A.2014.38.11.1215
Breaking time is an important performance indicator of a circuit breaker. Thus, the operating mechanism of the circuit breaker should be optimized for reducing the breaking time. The operating mechanism in a gas circuit breaker is made up of several latches. Specifically, the geometry and relative positions of latches influence the dynamic behaviors of the operating mechanism. In this study, a three-stage latch operating mechanism is analyzed on the basis of the verified multibody dynamics model constructed using the MSC.ADAMS program. The relative positions and lengths of latches are selected as design variables. The dominant design variables are selected by a design study. Optimization is performed using a genetic algorithm (GA). The study results demonstrate that the performance of the circuit breaker improves by about 22.5.
Accelerated Life Evaluation of Propeller Shaft for Forklift Truck
Kim, Do-Sik ; Sung, Baek-Ju ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 11, 2014, Pages 1221~1229
DOI : 10.3795/KSME-A.2014.38.11.1221
This paper proposes an approach for predicting the fatigue life of a propeller shaft of a forklift truck by an accelerated life test method. The accelerated life test method adopted in this study is the calibrated accelerated life test, which is highly effective in the prediction of the lifetime and enables significant reduction of the test time as well as a quantification of reliability in the case of small sample sizes. First, the fatigue test was performed under two high stress levels, and then, it was performed by setting low stress levels in consideration of the available test time and extrapolation. Major reliability parameters such as the lifetime, accelerated power index, and shape parameter were obtained experimentally, and the experimentally predicted lifetime of the propeller shaft was verified through comparison with results of an analysis of load spectrum data under actual operating conditions.
Modeling and Verification of Multibody Dynamics Model of Military Vehicle Using Measured Data
Ryu, Chi Young ; Jang, Jin Seok ; Yoo, Wan Suk ; Cho, Jin Woo ; Kang, E-Sok ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 11, 2014, Pages 1231~1237
DOI : 10.3795/KSME-A.2014.38.11.1231
It is essential to perform driving performance tests of military vehicles on rough terrain. A full car test is limited by cost and time constraints, because of which a dynamic analysis via computer simulation is preferred. In this study, a vehicle model is developed using MSC.ADAMS, a commercial multibody analysis program, and compared via experiments. FTire is modeled using the results of a tire performance test to obtain the vertical stiffness. A nonlinear damper is modeled by a characteristic experiment. Leaf springs are modeled with beam force elements and consisted to a vehicle model. The vertical force and acceleration response of the wheel are identified when vehicle is passing over a simple bump as well as a sinusoidal road. The developed vehicle model is verified with the results of a full car test.
Study on Fastened Properties by Applied to CFRP Laminates of Subminiature Screw
Choi, Byung Hui ; Kim, Ho Joong ; Kim, Ji Hoon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 11, 2014, Pages 1239~1243
DOI : 10.3795/KSME-A.2014.38.11.1239
This paper presents the application of carbon-fiber-reinforced polymer (CFRP) for the damage absorption and optimal design of portable smart devices to close in life. CFRP specimens are subjected to a tensile test to estimate their mechanical properties in terms of the stacking angles. Further, the screw reverse torque and screw torque at each stacking angle are determined using a torque tester after tapping holes on the CFRP specimens. Two experiments are performed for comparing their results in order to determine optimal conditions. In the tensile test, a woven specimen is found to have the highest strength and stiffness. In the case of the woven specimen, no difference is observed even when it is applied to prevent loosening of the coating. And average result value was excellent.
Estimation of Fatigue Crack Growth using Gamma Process Model
Park, Sung Ho ; Kim, Jae Hoon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 11, 2014, Pages 1245~1256
DOI : 10.3795/KSME-A.2014.38.11.1245
The physical nature of fatigue shows the considerable amount of scatter from intrinsic and extrinsic factors. In this study, some degradation models, such as the gamma process model, were reviewed in terms of uncertainties associated with the continuous, gradual, and monotonic nature of fatigue crack growth. Statistically varying fatigue crack growth data obtained from Lu and Meeker were used as an example to demonstrate the use of the gamma process model. This model can describe the condition and lifetime as statistical distribution curves whose shapes vary with cycles. From the skewness of the statistical distribution curves, it was confirmed that the median is suitable for being considered as the expected life. The use of the gamma process model enables the optimum replacement period and percentile life to be employed as criteria for preventive maintenance policy.
Estimates of Partial Safety Factors of Circumferential Through-Wall Cracked Pipes Based on Elastic-Plastic Crack Initiation Criterion
Lee, Jae-Bin ; Huh, Nam-Su ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 11, 2014, Pages 1257~1264
DOI : 10.3795/KSME-A.2014.38.11.1257
Efforts are presently underway for developing an optimal design methodology for GEN-IV nuclear reactors based on target failure probabilities. A typical example is the system-based code, in which the results are represented in the form of partial safety factors (PSFs). Thus, a PSF is one of the crucial elements in either component design or integrity assessment based on target failure probabilities during the operation period. In the present study, a procedure for calculating the PSF of a circumferential through-wall cracked pipe based on the elastic-plastic crack initiation criterion is established, in which the importance of each input variable is assessed. Elastic-plastic J-integrals are calculated using the GE/EPRI and reference stress methods, and the PSF values are calculated using both first- and second-order reliability methods. Moreover, the effect of statistical distributions of assessment variables on the PSF is also evaluated.
Progressive Failure Analysis of Adhesive Joints of Filament-Wound Composite Pressure Vessel
Kim, Junhwan ; Shin, Kwangbok ; Hwang, Taekyung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 11, 2014, Pages 1265~1272
DOI : 10.3795/KSME-A.2014.38.11.1265
This study performed the progressive failure analysis of adhesive joints of a composite pressure vessel with a separated dome by using a cohesive zone model. In order to determine the input parameters of a cohesive element for numerical analysis, the interlaminar fracture toughness values in modes I and II and in the mixed mode for the adhesive joints of the composite pressure vessel were obtained by a material test. All specimens were manufactured by the filament winding method. A mechanical test was performed on adhesively bonded double-lap joints to determine the shear strength of the adhesive joints and verify the reliability of the cohesive zone model for progressive failure analysis. The test results showed that the shear strength of the adhesive joints was 32MPa; the experiment and analysis results had an error of about 4.4%, indicating their relatively good agreement. The progressive failure analysis of a composite pressure vessel with an adhesively bonded dome performed using the cohesive zone model showed that only 5.8% of the total adhesive length was debonded and this debonded length did not affect the structural integrity of the vessel.
Characteristic Analysis and Fabrication of Bioceramic Scaffold using Mixing Ratios of TCP/HA by Fused Deposition Modeling
Sa, Min-Woo ; Kim, Jong Young ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 11, 2014, Pages 1273~1281
DOI : 10.3795/KSME-A.2014.38.11.1273
Tissue engineering is an emerging research field that has the potential to restore, regenerate and repair damaged bone tissue and organs. Tricalcium phosphate and hydroxyapatite biomaterials-based calcium phosphate are excellent materials that have both osteoconduction and biocompatibility for bone tissue regeneration. In this study, solution structures were successfully fabricated using a fused deposition modeling system based on deposition and heating devices. The morphology characteristics of the bioceramic scaffolds sintered at a temperature of
were analyzed by scanning electron microscopy. The effects of various blended TCP/HA ratio on the microstructure and shrinkage were studied. The mechanical properties of the scaffolds were measured using a compression testing machine from stress-strain curves on the crosshead velocity of 1 mm/min. The fabricated scaffolds were evaluated by cell proliferation tests of MG-63 cells. The results of this study suggest that the blended TCP(75 wt%)/HA(25 wt%) scaffold is an appropriate scaffold for bone tissue regeneration.
Forensic Engineering Study on Structure Stability Evaluation of Deep Cement Mixing Vessel using ADINA Software
Kim, Eui Soo ; Kim, Jong Hyuk ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 11, 2014, Pages 1283~1290
DOI : 10.3795/KSME-A.2014.38.11.1283
Recently, a wide variety of simulation techniques such as structure analysis and structure-fluid interaction analysis are being employed in the field of forensic engineering for resolving the problem of legal liability for accidents and disasters. In this study, we performed a forensic engineering investigation of a sinking accident of a DCM (deep cement mixing) vessel. The accident vessel was built as a dedicated SCP (sand compaction pile) vessel at the time of vessel building, and the DCM vessel was structurally modified, e.g., by increasing the leader height and constructing for leader expansion, without a stability review. To determine the effects of expansion and modification of structures in this sinking accident, structural stability evaluation was performed using commercial software for structural analysis, ADINA software. Through an analysis and comparison of simulation results obtained using ADINA software with the results of the structural modification and expansion, we could determine the exact cause of the sinking accident of the DCM vessel.
Integrated Chassis Control with Electronic Stability Control and Active Rear Steering
Yim, Seongjin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 11, 2014, Pages 1291~1297
DOI : 10.3795/KSME-A.2014.38.11.1291
This paper proposes integrated chassis control (ICC) with electronic stability control (ESC) and active rear steering (ARS). Direct yaw moment control is used to generate a control yaw moment. A weighted pseudo-inverse-based control allocation (WPCA) method is adopted to distribute the control yaw moment into tire forces, generated by ESC and ARS. Simulation-based tuning of variables weights in the WPCA is used to enhance the yaw moment distribution performance. Simulations using the vehicle simulation software
show that the proposed ICC is effective in improving maneuverability and lateral stability.
Selection and Verification of 3D Finite Element Method Model for Silicone Foot Sensor with Low Detection Pressure
Seong, Byuck Kyung ; Seo, Hyung Kyu ; Kim, Dong Hwan ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 11, 2014, Pages 1299~1307
DOI : 10.3795/KSME-A.2014.38.11.1299
In this work, an appropriate analysis model of a precise foot sensor with low detection pressure capability under a low range of variation in the dimensional variables was proposed. With a simple two-dimensional model, it was found that a remarkably high error level sometimes occurred between the analysis and experimental results. In order to overcome the error and improve the performance, a three-dimensional model was introduced, and the detection pressure and sensor characteristics were compared with those of the experimental results, which showed its enhanced performance with less error and higher precision.
Study on Running Safety of EMS-Type Maglev Vehicle Traveling over a Switching System
Han, Jong-Boo ; Lee, Jong Min ; Han, Hyung-Suk ; Kim, Sung-Soo ; Yang, Seok-Jo ; Kim, Ki-Jung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 11, 2014, Pages 1309~1315
DOI : 10.3795/KSME-A.2014.38.11.1309
The switch for a maglev vehicle should be designed such that the vehicle safely changes its track without touching the guiderail. In particular, a medium-to-low-speed EMS -type maglev train relies heavily on a U-type electromagnet where it generates levitation force and guidance force simultaneously. Therefore, it is necessary to evaluate the safety of the vehicle whenever it passes the switch, as it lacks active control of the guidance force. Furthermore, when the vehicle passes a segmented switch, which is a group of curves made up of connected lines with a small radius of curvature, it may come into mechanical contact with the guiderail owing to the excessive lateral displacement of the electromagnet. The goal of this study is to analyze the influence of a segmented switch on the safety of major design-related variables for achieving improved running safety. We propose a three-dimensional multibody dynamics model composed of two cars with one body. Using the proposed model, we perform a simulation of the lateral air gap, which is one of the measurements of the running safety of the vehicle when it passes the switch. The analyzed design variables are the length between short span girder, the articulation angle, the length between two centers of a fixed girder at its ends, and the number of girders. On the basis of the effects of the considered design variables, we establish an optimized design of a switch with improved safety.