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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 34, Issue 12 - Dec 2010
Volume 34, Issue 11 - Nov 2010
Volume 34, Issue 10 - Oct 2010
Volume 34, Issue 9 - Sep 2010
Volume 34, Issue 8 - Aug 2010
Volume 34, Issue 7 - Jul 2010
Volume 34, Issue 6 - Jun 2010
Volume 34, Issue 5 - May 2010
Volume 34, Issue 4 - Apr 2010
Volume 34, Issue 3 - Mar 2010
Volume 34, Issue 2 - Feb 2010
Volume 34, Issue 1 - Jan 2010
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Control Algorithm for Stable Galloping of Quadruped Robots on Irregular Surfaces
Shin, Chang-Rok ; Kim, Jang-Seob ; Park, Jong-Hyeon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 6, 2010, Pages 659~665
DOI : 10.3795/KSME-A.2010.34.6.659
This paper proposes a control algorithm for quadruped robots moving on irregularly sloped uneven surfaces. Since the body balance of a quadruped robot is controlled by the forces acting on its feet during touchdown, the ground reaction force (GRF) is controlled for stable running. The desired GRF for each foot is generated on the basis of the desired galloping pattern; this GRF is then compared with the actual contact force. The difference between the two forces is used to modify the foot trajectory. The desired force is realized by considering a combination of the rate change of the angular and linear momenta at flight. Then, the amplitude of the GRF to be applied at each foot in order to achieve the desired linear and angular momenta is determined by fuzzy logic. Dynamic simulations of galloping motion were performed using RecurDyn; these simulations show that the proposed control method can be used to achieve stable galloping for a quadruped robot on irregularly sloped uneven surfaces.
Locomotion of Biped Robots on Irregular Surface Based on Pseudo-Impedance Model
Shin, Hyeon-Sik ; Park, Jong-Hyeon ; Kwon, O-Hung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 6, 2010, Pages 667~673
DOI : 10.3795/KSME-A.2010.34.6.667
This paper proposes a control method based on a pseudo-impedance model to control the motion of biped robots walking on an uneven surface. The pseudo-impedance model simulates the action of the ankle of a foot landing on the ground when a human walks. When the foot is in contact with the ground, the human ankle goes through two different phases. In the first phase, the human exerts little or no effort and applies no torque on the ankle so that the orientation of the foot is effortlessly and passively adjusted with respect to the ground. In the second phase of landing, the ankle generates a significant amount of torque in order to rotate and move the main part of the human body forward and to support the weight of the human; this phase is called the weight acceptance phase. Computer simulations of a 12-DOF biped robot with a 6-DOF environment model were performed to determine the effectiveness of the proposed pseudo-impedance control. The simulation results show that stable locomotion can be achieved on an irregular surface by using the proposed model.
Development of Bioreactor for Regenerative Medicine and Effect of Mechanical Stimuli on Mesenchymal Stem Cells in Polyurethane Scaffolds
Joo, Min-Jin ; Chun, Heoung-Jae ; Jung, Hyung-Jin ; Lee, Chang-Gun ; Heo, Dong-Nyoung ; Kwon, Il-Keun ; Moon, Seong-Hwan ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 6, 2010, Pages 675~681
DOI : 10.3795/KSME-A.2010.34.6.675
It is well known that mesenchymal stem cell(MSCs) can be differentiated into fibroblasts, chondrocytes, and osteoblasts and that they develop into fibrous tissue, cartilage, or bone, as a result of mechanical stimulation. In this study, we developed a bioreactor system, which is composed of a reactor vessel that provides the required cell culture environment, an environment controlling chamber to control the media, a gas mixer, and a reactor motion control subsystem to apply mechanical stimuli to the cells. For the MSC culture, We used a poly-urethane (PU) scaffold, with a collagen coating to ensure improved cohesion ratio. Then, we transferred the cultivated MSCs in the PU scaffold, cultured the cells in the bioreactor system, and confirmed the proliferation, differentiation, and ossification processes, resulting from mechanical stimuli.
Locomotion Control of Biped Robots with Serially-Linked Parallel Legs
Yoon, Jung-Han ; Park, Jong-Hyeon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 6, 2010, Pages 683~693
DOI : 10.3795/KSME-A.2010.34.6.683
In this paper, we propose a new parallel mechanism for the legs of biped robots and the control of the robot's locomotion. A leg consists of two 3-DOF parallel platforms linked serially: one is an orientation platform for a thigh and the other is the 3-DOF asymmetric parallel platform for the shank. The desired locomotion trajectory is generated on the basis of the Gravity-Compensated Inverted Pendulum Mode (GCIPM) in the sagittal direction and the Linear Inverted Pendulum Mode (LIPM) in the lateral direction, respectively. In order to simulate the ground reaction force, a 6-DOF elastic pad model is used underneath each of the soles. The performance and effectiveness of the proposed parallel mechanism and locomotion control are shown by the results of computer simulations of a 12-DOF parallel biped robot using
Use of Guided Waves for Monitoring Material Conditions in Fossil-Fuel Power Plants
Cho, Youn-Ho ; Jung, Kyung-Sik ; Lee, Jae-Sun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 6, 2010, Pages 695~700
DOI : 10.3795/KSME-A.2010.34.6.695
Material properties of the lock plate, which covers the gas-turbine blade, are studied using ultrasonic guided waves. The lock plate is a crucial part of a gas-turbine power plant. The wave velocity and attenuation coefficient are measured to investigate the changes in the material properties under three heat-treatment conditions. Compared to the destructive mechanical tests, the material characterization of Inconel X-750 can be performed more efficiently and nondestructively by using ultrasonic guided waves; this characterization helps identify the changes occurring in its elastic moduli and Poisson's ratio under different heat-treatment conditions. The wave velocity and hardness of Inconel X-750 are proportional to each other. This nondestructive technique for the measurement of material properties can be widely used in various industries to avoid catastrophic failure. It is also expected that the guided-wave technique can be applied as a new cost- and time-saving inspection tool for longer and wider inspection ranges.
Stress and Displacement Fields of a Propagating Mode III Crack in Orthotropic Piezoelectric Materials
Lee, Kwang-Ho ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 6, 2010, Pages 701~708
DOI : 10.3795/KSME-A.2010.34.6.701
The stress and displacement fields of a permeable propagating crack in orthotropic piezoelectric materials under anti-plane shear mechanical load and in-plane electric load are analyzed. The equations of motion for the propagating crack in piezoelectric materials are developed and the solution on the stress and the displacement fields through an asymptotic analysis was obtained. The influences of the piezoelectric constant and of the dielectric permittivity on the stress and displacement fields at the crack tip are explicitly clarified. Using the stress and displacement fields obtained in this study, the characteristics of stress and displacement at a propagating crack tip in piezoelectric materials are discussed.
Assessment of Effective Factor of Hydrogen Diffusion Equation Using FE Analysis
Kim, Nak-Hyun ; Oh, Chang-Sik ; Kim, Yun-Jae ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 6, 2010, Pages 709~715
DOI : 10.3795/KSME-A.2010.34.6.709
The coupled model with hydrogen transport and elasto-plasticity behavior was introduced. In this paper, the effective factor of the hydrogen diffusion equation has been described. To assess the effective factor, finite element (FE) analyses including hydrogen transport and mechanical loading for boundary layer specimens with low-strength steel properties are carried out. The results of the FE analyses are compared with those from previous studies conducted by Taha and Sofronis (2001).
Evaluation of Fatigue Crack Propagation Depending on Fiber Array Direction in Woven CFRP Composites
Geum, Jin-Hwa ; Choi, Jung-Hun ; Park, Hong-Sun ; Koo, Jae-Mean ; Seok, Chang-Sung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 6, 2010, Pages 717~723
DOI : 10.3795/KSME-A.2010.34.6.717
Many researchers have studied woven fabric carbon-fiber-reinforced composite (CFRP) materials but the study of fatigue crack propagation in composites has been insufficient. It has known that the crack propagation behavior differs depending on the load and the fiber direction. In this study, the fatigue crack propagation along two different fiber array directions (
) in plain woven CFRP composite was investigated. Fatigue crack propagation tests were conducted on the woven CFRP composite under a sinusoidal waveform load with stress ratios of 0.1 at a frequency of 10 Hz. Once the results of the tests were obtained, fatigue crack propagation rates (da/dN) were plotted against the energy release rate amplitude (
), and it was observed that either mode I crack propagation or mixed mode crack propagation occurs depending on the fiber array direction.
Leak-Before-Break Behavior and Crack Opening Displacement in Piping Under Bending Load
Nam, Ki-Woo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 6, 2010, Pages 725~730
DOI : 10.3795/KSME-A.2010.34.6.725
The leak-before-break behavior and the crack opening displacement were investigated of statically indeterminate piping system and statically determinate piping system after a crack penetration. The reduction in the ultimate strength caused by a crack was relatively small in the statically indeterminate piping system. The leak-before-break in the statically indeterminate piping system had a larger safety margin than that in the statically determinate piping system. The crack opening displacement after crack penetration in a pipe with a nonpenetrating crack was evaluated by using a plastic rotation angle.
Comparative Study of Bifurcation Behavior of Rubber in Accordance with the Constitutive Equations
Park, Moon-Shik ; Song, Seung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 6, 2010, Pages 731~742
DOI : 10.3795/KSME-A.2010.34.6.731
Modeling of rubber for design or analysis often requires confusing or complex work because there are a large number of constitutive models to be considered. Some models have few material constants, while others have many. Researchers have to prepare and fit extensive experimental data with caution and discretion. In this paper, we first compared some typical rubber models in which deformation was carried out by stretching up to around eight times the original size. We conclude that continuum-based models and chain molecular models can be used in the study of the small deformation in most engineering applications, but chain molecular models are preferred in the study of the large deformations in most biomaterial applications. As discrimination problems, Treloar's patch and cylindrical balloon stick are tested theoretically and numerically for studying bifurcation. In the case of Treloar's patch, by using the Kearsley's equation, we show that bifurcation exists for continuum-based models but not for chain molecular models. Both models show bifurcation in the cylindrical balloon stick. Therefore, in the analysis of the bifurcation of rubber showed that its existence also depends on the constitutive model selected.
Derating Design for Improving System Reliability by Using a Probabilistic Approach
Son, Young-Kap ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 6, 2010, Pages 743~749
DOI : 10.3795/KSME-A.2010.34.6.743
This paper proposes a derating design method for improving system reliability by using a probabilistic approach. In the proposed design, the focus is upon system levels in determining derated levels of stresses such as temperature and current, unlike recent design approaches that focus on component levels. System reliability is evaluated using component reliability metrics that are given as functions of time and unknown stresses; this evaluation is based on a series system-reliability model. The variation in stress, which was not considered in previous derating designs, is introduced in the present design to account for the uncertainty in both environmental and operating conditions at the customer' hands. Optimization problems for system reliability improvement are formulated and solved using FORM to determine the best derating design. An example of a derating design for an electrical system shows the details of the proposed method and its applicability to systems design for reliability improvement.
Study of Ultrasonic Nonlinearity in Heat-Treated Material
Li, Weibin ; Lee, Jae-Sun ; Cho, Youn-Ho ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 6, 2010, Pages 751~756
DOI : 10.3795/KSME-A.2010.34.6.751
Ultrasonic nonlinearity is very sensitive to changes in material properties. This paper describes the study of the correlation between heat treatment and ultrasonic nonlinearity by taking nonlinear factors into consideration. A modified formula was proposed for ultrasonic velocity. This formula indicated that the changes occurring in nonlinearity during heat treatments cause changes in the ultrasonic velocity. The experimental results show that the relative nonlinearity parameters calculated from the modified ultrasonic velocities and the ratio of amplitudes of the second harmonic and fundamental wave are in good agreement. The experimental results prove that heat treatment can result in changes in material nonlinearity. Moreover, the relative nonlinearity parameter calculated from the modified velocity formula is has a large value. Since this parameter has high sensitivity to changes in nonlinearity, it can be used to represent the relative nonlinearity change calculated in this study by using the modified formula for ultrasonic velocity.
Fatigue Damage Evaluation of Woven Carbon-Fiber-Reinforced Composite Materials by Using Fatigue Damage Model
Park, Hong-Sun ; Choi, Jung-Hun ; Koo, Jae-Mean ; Seok, Chang-Sung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 6, 2010, Pages 757~762
DOI : 10.3795/KSME-A.2010.34.6.757
Owing to the high specific strength and stiffness of composite materials, they are extensively used in mechanical systems and in vehicle industries. However, most mechanical structures experience repeated load and fatigue. Therefore, it is important to perform fatigue analysis of fiber-reinforced composites. The properties of composite laminates vary depending upon the stacking sequence and stacking direction. Fatigue damage of composite laminates occurs according to the following sequence: matrix cracking, delamination, and fiber breakage. In this study, fatigue tests were performed for damage analysis. Fatigue damages, which have to be considered in fatigue analysis, are determined by using the stiffness values calculated from hysteresis loops, and the obtained fatigue damage curve is examined using Mao's equation and Abdelal's equation.
Fatigue Characteristic of High Impact Polystyrene(HR-1360) Materials
Kang, Min-Sung ; Koo, Jae-Mean ; Seok, Chang-Sung ; Park, Jae-Sil ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 6, 2010, Pages 763~769
DOI : 10.3795/KSME-A.2010.34.6.763
In recent times, there has been considerable interest in HIPS (High Impact Polystyrene) materials for their use in construction of office equipments, home electronics, housing for electronics appliances, packing containers, etc. However, these materials suffer from problems caused by fatigue fracture. Further, their strength is substantially affected by environmental conditions. Therefore, in this study, the effect of temperature was analyzed by performing a tensile test and a fatigue test. It was observed that the yield strength, the ultimate strength, and the fatigue life decreased relatively with an increase in temperature. Further, an S-N curve can be predicted by using the results of the tensile test and a micro-Vickers hardness test.
Design of Six-Component F/T Sensor with Flexible Fixed Ends
Lee, Bong-Hee ; Joo, Jin-Won ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 6, 2010, Pages 771~780
DOI : 10.3795/KSME-A.2010.34.6.771
This paper describes the design process of a six-component force/torque (F/T) sensor. The new six-component F/T sensor having leaf spring ends has been developed using a cross beam structure as the basic sensing element. Fundamental strain analysis of both ends fixed beam having a leaf spring structure is performed by finite element analysis. In order to obtain similar output sensing strains from the six component loads and minimize coupling strains, the optimal location of strain gages is determined and the strain gages are connected so that the bridge circuits with four strain gages would be balanced. Using leaf spring ends instead of rigid fixed ends, remarkable increment in output sensing strain can be achieved for two component forces. Several modifications in design result in a similar sensing strain of approximately
for the six-component forces and moments, and a reduced coupling strain of
between the forces and moments.
Failure Data Analysis of J79 Engine Transfer Gearbox for Aircraft Maintenance Planning
Choi, Jae-Man ; Yang, Seung-Hyo ; Hwang, Young-Ha ; Son, Ik-Sang ; On, Yong-Sub ; Kim, Young-Jin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 6, 2010, Pages 781~787
DOI : 10.3795/KSME-A.2010.34.6.781
Forecasting possible failure characteristics is very important in maintenance planning because it helps in predicting any future failures and determining the optimum replacement interval. This paper examines the time.to-failure distribution of the transfer gearbox of a J79 engine by using a probability plotting technique which is one of the most convenient techniques for reliability analysis. Various probability distributions are evaluated for determining the suitable probability distribution of the failure data of the transfer gearbox, and the resulting correlation coefficient indicates that failure data have a lognormal distribution. The expected number of unscheduled maintenance actions and the optimum replacement interval for various values of cost ratios are determined.
Inchworm-Like Robotic Colonoscope UsingLegs for Clamping
Park, Hyun-Jun ; Leem, Sang-Hyuck ; Kim, Byung-Kyu ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 6, 2010, Pages 789~795
DOI : 10.3795/KSME-A.2010.34.6.789
For the reliable clamping of a robotic colonoscope inside the colon, we propose a clamping module consisting of six legs at the front and a trigger at the rear. In addition, a pneumatic-line based locomotive mechanism, which was developed previously for in-pipe inspection, is adopted to reduce the friction force between the pneumatic lines and the locomotion environment. In order to evaluate locomotion performance, a robot with a diameter of 15 mm and a length of 110.250 mm is used. Based on control signal from LabVIEW, it is tested in acrylic pipe and pig's colon. The proposed robot is able to move in the curved path which has a radius of over 25 mm. The speed of the robot is 33 mm/s in a straight path and 12.1 mm/s on a vertical path. The proposed robot, which has one pneumatic line and two clamping modules, conclusively shows reliable locomotion performance under in vitro condition.
Construction of Vehicle Door Impact Beam Using Hot Stamping Technology
Lee, Hyun-Woo ; Hwang, Jung-Bok ; Kim, Sun-Ung ; Kim, Won-Hyuck ; Yoo, Seung-Jo ; Lim, Hyun-Woo ; Yum, Young-Jin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 6, 2010, Pages 797~803
DOI : 10.3795/KSME-A.2010.34.6.797
A vehicle door impact beam made of a thin sheet of steel has been constructed using hot stamping technology with the aim of ensuring occupant safety in the event of a side collision. This technology has been used to increase the strength of the vehicle body parts and to reduce the weight of the door impact beam as well as the number of work processes. Mechanical tests were performed to determine the material properties of the hot-stamped specimen and the results of the tests were used as input data in stamping and structural simulation in order to obtain the optimal design of door impact beam. The strength of the hot-stamped door impact beam increased to a value that was 102% higher than that of conventional pipe-shaped door impact beam. A weight reduction of 34% was also achieved.