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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
Selecting the target year
Lubrication Characteristics of Micro-Textured Slider Bearing: Effect of Dimple Density
Park, Tae Jo ; Lee, Joon Oh ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 4, 2013, Pages 437~442
DOI : 10.3795/KSME-A.2013.37.4.437
In recent times, surface texturing methods have been widely applied to reduce friction and improve the reliability of machine components such as parallel thrust bearings, mechanical face seals, and piston rings. In this study, a numerical analysis is carried out to investigate the effect of uniformly spaced hemispherical dimples on the lubrication characteristics of a slider bearing using a commercial computational fluid dynamics (CFD) code, FLUENT. The pressure distributions, load capacity, leakage flowrate, and friction force are strongly affected by the dimple diameter and the number of dimples. In particular, the load capacity and friction force decrease linearly with the dimple density whereas the leakage increases. These results can be used for designing the optimum dimple characteristics in order to improve the lubrication performance of slider bearings, for which further studies are required.
Ultrasound Thermography Technique for Detecting Micro Defects in Vehicle Engine Block
Kim, Sung Hyun ; Kim, Jae Yeol ; Choi, Seung Hyun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 4, 2013, Pages 443~446
DOI : 10.3795/KSME-A.2013.37.4.443
An infrared thermography technique can be used to inspect a large area simultaneously and to detect defects such as cracks or delaminations in real time. Infrared thermography is a technique in which visual images are formed from the infrared range from subjects according to their thermal radiation. The molecules of all objects are disturbed by heat, and the molecular motion becomes more active when the temperature rises and less active when the temperature falls. In this study, the applicability and feasibility of ultrasound thermography for detecting defects in an engine block, which is a key component in the automobile industry, were verified. A nondestructive reliability test was conducted to study the defects, after which the results were analyzed.
Evaluation of Two Robot Vision Control Algorithms Developed Based on N-R and EKF Methods for Slender Bar Placement
Son, Jae Kyung ; Jang, Wan Shik ; Hong, Sung Mun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 4, 2013, Pages 447~459
DOI : 10.3795/KSME-A.2013.37.4.447
Many problems need to be solved before vision systems can actually be applied in industry, such as the precision of the kinematics model of the robot control algorithm based on visual information, active compensation of the camera`s focal length and orientation during the movement of the robot, and understanding the mapping of the physical 3-D space into 2-D camera coordinates. An algorithm is proposed to enable robot to move actively even if the relative positions between the camera and the robot is unknown. To solve the correction problem, this study proposes vision system model with six camera parameters. To develop the robot vision control algorithm, the N-R and EKF methods are applied to the vision system model. Finally, the position accuracy and processing time of the two algorithms developed based based on the EKF and the N-R methods are compared experimentally by making the robot perform slender bar placement task.
Reliability and Sensitivity Analysis for Laminated Composite Plate Using Response Surface Method
Lee, Seokje ; Jang, Moon-Ho ; Kim, Jae-Ki ; Moon, Jung-Won ; Kim, In-Gul ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 4, 2013, Pages 461~466
DOI : 10.3795/KSME-A.2013.37.4.461
Advanced fiber-reinforced laminated composites are widely used in various fields of engineering to reduce weight. The material property of each ply is well known; specifically, it is known that ply is less reliable than metallic materials and very sensitive to the loading direction. Therefore, it is important to consider this uncertainty in the design of laminated composites. In this study, reliability analysis is conducted using COMSOL and MATLAB interactions for a laminated composite plate for the case in which the tip deflection is the design requirement and the material property is a random variable. Furthermore, the efficiency and accuracy of the approximation method is identified, and a probabilistic sensitivity analysis is conducted. As a result, we can prove the applicability of the advanced design method for the stabilizer of an underwater vehicle.
Experimental and Finite Element Study of Tribological Characteristics of SU-8 Thin Film
Yang, Woo Yul ; Shin, Myounggeun ; Kim, Hyung Man ; Han, Sangchul ; Sung, In-Ha ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 4, 2013, Pages 467~473
DOI : 10.3795/KSME-A.2013.37.4.467
In this study, two-dimensional finite element models were developed and experiments were conducted using an atomic force microscope to investigate the tribological characteristics of an SU-8 layer coated on a patterned wafer for microsystem applications. The results revealed that both the adhesion and the friction forces measured by the atomic force microscope were lower for the SU-8 coated surface than for the bare silicon surface. This is attributed to the hydrophobicity of SU-8. Another important result derived from the finite element analysis was the critical load required to fracture the SU-8 film with respect to the thickness. The critical loads for thicknesses of 200, 400, and 800 nm were approximately 13, 22, and 28 mN, respectively, which corresponded to a Hertzian contact pressure of 1.2-1.8 GPa. These results will aid in the design of a suitable SU-8 thickness for microsystem components that are in contact with one another.
Controller Parameters Design of Direct Drive Servo Valve Using Genetic Algorithm and Complex Method
Lee, Seong Rae ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 4, 2013, Pages 475~481
DOI : 10.3795/KSME-A.2013.37.4.475
The control system of a direct drive servo valve is a nonlinear system, and the flow force effect on the spool motion is significant and dependent on the load pressure. To satisfy the control system design requirements, the optimal parameters of the lead-lag controller and the derivative feedback controller are searched for using a genetic algorithm and a complex constrained direct search type method. The obtained controller parameters successfully perform their role to satisfy the control system design requirements.
Evaluation of Formability and Mechanical Characteristic for Hot Forming Quenching in Sheet Forming of Al6061 Alloy
Ko, Dae Hoon ; Kim, Jae Hong ; Lee, Chan Joo ; Ko, Dae Cheol ; Kim, Byung Min ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 4, 2013, Pages 483~490
DOI : 10.3795/KSME-A.2013.37.4.483
In aluminum sheet metal forming, the conventional forming methods of T4 or T6 heat-treated sheets result in low formability and dimensional accuracy. This study suggests a new forming method for aluminum sheets called as hot forming quenching (HFQ) that solves the problems faced in the conventional method. HFQ combines the heat treatment and forming processes through the forming die during the quenching of a solid solution. To evaluate the application of HFQ to the sheet forming of aluminum, an Erichsen and V-bending test are performed in this study to measure the dimensional accuracy and formability, which are then compared with those of the conventional forming method. Furthermore, the strength and hardness of the products formed by HFQ are measured to confirm the degradation in mechanical properties compared with the conventional forming method, which shows the validity of the application of HFQ to aluminum sheet metal forming.
Finite Element Simulation of Fracture Toughness Test
Chu, Seok Jae ; Liu, Conghao ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 4, 2013, Pages 491~496
DOI : 10.3795/KSME-A.2013.37.4.491
Finite element simulations of tensile tests were performed to determine the equivalent stress - equivalent plastic strain curves, critical equivalent stresses, and critical equivalent plastic strains. Then, the curves were used as inputs to finite element simulations of fracture toughness tests to determine the plane strain fracture toughness. The critical COD was taken as the COD when the equivalent plastic strain at the crack tip reached a critical value, and it was used as a crack growth criterion. The relationship between the critical COD and the critical equivalent plastic strain or the reduction of area was found. The relationship between the plane strain fracture toughness and the product of the critical equivalent stress and the critical equivalent plastic strain was also found.
Interlaminar Fracture Toughness of Hybrid Composites Inserted with Different Kinds of Non-Woven Tissues : Part I-Mode I
Jeong, Jong-Seol ; Cheong, Seong-Kyun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 4, 2013, Pages 497~502
DOI : 10.3795/KSME-A.2013.37.4.497
In this study, the interlaminar fracture toughness in mode I of a hybrid composite inserted with different types of non-woven tissues was determined. The interlaminar fracture toughness in mode I is obtained by a double cantilever beam test. The experiment is performed using three types of non-woven tissues: 8
of carbon tissue, 10
of glass tissue, and 8
of polyester tissue. Considering a specimen with no non-woven tissue as a reference, the interlaminar fracture toughness in mode I of specimens inserted with non-woven carbon and glass tissues decreases by as much as 6.3% and 11.4%, respectively. However, the fracture toughness of a hybrid composite specimen inserted with non-woven polyester tissue increases by as much as 69.4%. It is considered that the specimen inserted with non-woven polyester tissue becomes cheaper, and lighter, and the value of the fracture toughness becomes much greater than that of the non-woven carbon tissue.
Evaluation of Compressive Residual Strength in Composite Material Under Impact Damage
Ahn, Sang Soo ; Hong, Suk Woo ; Koo, Jae Mean ; Seok, Chang Sung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 4, 2013, Pages 503~509
DOI : 10.3795/KSME-A.2013.37.4.503
Carbon fiber reinforced plastics (CFRPs), a composite material, are generally vulnerable to compressive load and impact damage in a direction perpendicular to the surface of the material. In particular, during the operation of an aircraft, impact damages caused by bird collisions or falling tools reduce the strength of the aircraft structure. In this study, after impact damages were applied to CFRP specimens with various impact energies and impactor diameters, the compressive residual strength of the impact-damaged specimen was evaluated by performing a compression test. Furthermore, a prediction model for the compressive residual strength is proposed according to the variation in the impact energy by comparing the test results.
Comparative Study of Performance of Switching Control and Synchronous Notch Filter Control for Active Magnetic Bearings
Yoo, Seong Yeol ; Noh, Myounggyu ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 4, 2013, Pages 511~519
DOI : 10.3795/KSME-A.2013.37.4.511
Switching controllers for active magnetic bearings are claimed to minimize the copper losses because they do not use bias currents. In this study, we compare the performances of the switching controller with those of the widely used proportional-derivative (PD) controller. The PD controller is combined with a synchronous notch filter to reduce the effect of the unbalance disturbance. For a fair and objective comparison, the PD controller is designed systematically. The switching controller is designed so that the dynamics of the two controllers are almost identical. A system model is developed. This model includes the flexible modes of the rotor and the dynamics of the sensors and amplifiers. The simulation results show that the switching controller indeed reduces the copper loss at lower speeds. However, it fails to operate around the speed close to the bending mode of the rotor.
Element and Crack Geometry Sensitivities of Finite Element Analysis Results of Linear Elastic Stress Intensity Factor for Surface Cracked Straight Pipes
Ryu, Dongil ; Bae, Kyung-Dong ; Je, Jin-Ho ; An, Joong-Hyok ; Kim, Yun-Jae ; Song, Tae-Kwang ; Kim, Yong-Beum ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 4, 2013, Pages 521~527
DOI : 10.3795/KSME-A.2013.37.4.521
This study provides the elastic stress intensity factors, K, for circumferential and longitudinal surface cracked straight pipes under single or combined loads of internal pressure, bending, and torsion based on three-dimensional (3D) finite element (FE) analyses. FE results are compared with two different types of defect assessment codes (API-579-1 and RCC-MR A16) to prove the accuracy of the FE results and the differences between the codes. Through the 3D FE analysis, it is found that the stress intensity factors are sensitive to the number of elements, which they were believed to not be sensitive to because of path independence. Differences were also found between the FE analysis results for crack defining methods and the results obtained by two different types of defect assessment codes.
Mechanical Behavior of New Thin Sandwich Panel Subjected to Bending
Lee, Jung-In ; Kang, Ki-Ju ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 4, 2013, Pages 529~535
DOI : 10.3795/KSME-A.2013.37.4.529
A new thin sandwich panel composed of an aluminum expanded metal core adhesively jointed with stainless steel face sheets is introduced, and its mechanical behavior under three-point bending is investigated. The strength and stiffness are analyzed theoretically, and the press-formability and strength enhancement are evaluated experimentally. The specimens with the specific configurations exhibit face yielding well before face-core separation, which means that the sandwich panel can be formed by a press without failure. The measured load levels corresponding to the face yielding and the face-core separation agree fairly well with the theoretical estimations. For a given weight, the sandwich panel is superior to a solid panel in terms of strength, stiffness, and press-formability.
Compliant Mechanism Topology Optimization of Metal O-Ring
Kim, Geun-Hong ; Lee, Young-Shin ; Yang, Hyung-Lyeol ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 4, 2013, Pages 537~545
DOI : 10.3795/KSME-A.2013.37.4.537
The elastic recovery of a metal seal is a factor that can be used to assess its sealing performance. In this study, a compliant mechanism topology optimization has been performed to find a structure of a metal O-ring seal that can maintain excellent sealing performance with a maximized elastic recovery over extended operation. An evolutionary structural optimization (ESO) was used as a topology optimization algorithm with two different types of objective functions considering both flexibility and stiffness. In particular, a circular design domain was adopted to consider the outer shape of the metal O-ring seal. The elastic recovery of the optimal topology was calculated and compared to that of a commercial product.
Study of Hot Spinning Process for Head of CNG Storage Vessel
Lee, Hyun Woo ; Jung, Sung Yuen ; Kim, Chul ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 4, 2013, Pages 547~554
DOI : 10.3795/KSME-A.2013.37.4.547
The fuel storage vessel installed in CNG vehicles can be largely divided into 3 parts: head, cylinder, and dome. Studies of the cylinder and dome parts have already been performed, but sufficient design data is not available about the head part. Therefore, expert field engineers heavily depend upon trial-and-error methods. Therefore, FE analysis is performed to review the hot spinning process for forming the head part of the CNG vessel using the Arbitrary Lagrangian-Eulerian (ALE) method. The effects of forming factors on the load were analyzed. The values of the factors were chosen to avoid defects in the head part and buckling, and the forming feasibility of the head part was investigated. Furthermore, a bursting test was performed to evaluate the safety of the storage vessel.
Moving Support Elements for Dynamic Finite Element Analysis of Statically Determinate Beams Subjected to Support Motions
Kim, Yong-Woo ; Jhung, Myung Jo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 4, 2013, Pages 555~567
DOI : 10.3795/KSME-A.2013.37.4.555
A finite element formulation for a Rayleigh-damped Bernoulli-Euler beam subjected to support motions, which accompanies quasi-static rigid-body motion, is presented by using the quasi-static decomposition method. Moving support beam elements, one of whose nodes is coincident with the moving support, are developed to represent the effect of a moving support. Statically determinate beams subjected to support motions can be modeled successfully by using moving support elements. Examples of cantilever and simply-supported beams subjected to support motions are illustrated, and the numerical results are compared with the analytical solutions. The comparison shows good agreement.
Drug Bottle Delivery Robot Capable of Smartphone-Based Control and Image Process and Combining Wheel and Quadruped
Lee, Sang Young ; Kim, Hyun Su ; Kim, Young Long ; Hong, Seok Ho ; Kim, Dong Hwan ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 4, 2013, Pages 569~579
DOI : 10.3795/KSME-A.2013.37.4.569
Robot control and image processing using a smartphone and Wi-Fi communication is introduced. The robot has a wheel and quadruped mechanism that is transformed according to the environment and is mainly used for drug bottle delivery. The captured image on the camera is transmitted to the smartphone in the form of stream data, and the image data is processed in the smartphone to enable the robot to identify an object and to control the robot itself. A network was constructed so that only image data from the stream data was used, and an image processing scheme to identify the drug bottle and deliver it to a person using a robot arm is also presented. In this study, image processing techniques and algorithms were purely implemented on a smartphone with considerable computational power and multiple functions rather than a computer, which contributes to the intelligence and miniaturization of the robot system.
Effect of Damper Between Maglev Vehicles on Curve Negotiation
Kim, Ki-Jung ; Han, Hyung-Suk ; Kim, Chang-Hyun ; Yang, Seok-Jo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 37, issue 4, 2013, Pages 581~587
DOI : 10.3795/KSME-A.2013.37.4.581
In a magnetic train set composed of more than two cars, the installation of dampers between cars is carefully considered for improving both the ride quality and the safety, particularly during curve negotiation. In this study, a dynamic simulation of the ride quality and curve negotiation of a Maglev vehicle was carried out. The dynamic model is developed based on multibody dynamics. The presented full vehicle multibody dynamic model integrates the electromagnet model and its control algorithm. By using this model, the effects of the dampers are numerically analyzed. The proposed damper is installed on the vehicle and tested to analyze its effects. In this study, the simulation and measured results of the vehicle behavior and ride quality are discussed.