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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
Editor in Chief :
Volume & Issues
Volume 26, Issue 12 - Dec 2002
Volume 26, Issue 11 - Nov 2002
Volume 26, Issue 10 - Oct 2002
Volume 26, Issue 9 - Sep 2002
Volume 26, Issue 8 - Aug 2002
Volume 26, Issue 7 - Jul 2002
Volume 26, Issue 6 - Jun 2002
Volume 26, Issue 5 - May 2002
Volume 26, Issue 4 - Apr 2002
Volume 26, Issue 3 - Mar 2002
Volume 26, Issue 2 - Feb 2002
Volume 26, Issue 1 - Jan 2002
Selecting the target year
Effect of Interface Hole Shape on Dynamic Interface Crack Propagation
Yin, Hai-Long ; Lee, Ouk-Sub ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 7, 2002, Pages 1217~1222
DOI : 10.3795/KSME-A.2002.26.7.1217
The dynamic photoelasticity with the aid of Cranz-Shardin type high speed camera system is utilized to record the dynamically propagating behavior of the interface crack. This paper investigates the effects of the hole (existed along the path of the crack propagation) shape on the dynamic interface crack propagation behavior by comparing the experimental isochromatic fringes to the theoretical stress fields.
Fabrication and Characterization of TiNi Shape Memory Alloy Fiber Reinforced 6061 Aluminum Matrix Composite by Using Hot Press
Park, Dong-Sung ; Lee, Jun-Hee ; Lee, Guy-Chang ; Park, Young-Chul ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 7, 2002, Pages 1223~1231
DOI : 10.3795/KSME-A.2002.26.7.1223
Al alloy matrix composite with TiNi shape memory fiber as reinforcement has been fabricated by hot pressing to investigate microstructures and mechanical properties. The analysis of SEM and EDS showed that the composites have shown good interface bonding. The stress-strain behavior of the composites was evaluated at temperatures between 363K and room temperature as a function of prestrain, and it showed that the yield stress at 363K was higher than that of the room temperature. Especially, the yield stress of this composite increases with increasing the amount of prestrain, and it also depends on the volume fraction of fiber and heat treatment. The smartness of the composite is given due to the shape memory effect of the TiNi fiber which generates compressive residual stress in the matrix material when heated after being prestrained. Microstructural observation has revealed that interfacial reactions occur between the matrix and fiber, creating two intermetallic layers.
Optimization of the design variables of linear motor by FEM
Shin, Soo-Hyun ; Lee, Sang-Ryong ; Jung, Jae-Han ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 7, 2002, Pages 1232~1240
DOI : 10.3795/KSME-A.2002.26.7.1232
Recently, linear motors are applied to many small precision products. Thus high generating power with small size is required of it. In order to increase the motor efficiency, the design variables need to be optimized. In this study, Vector Fields FEM software, OPERA-3d, was used for simulating linear motor. The thrust and magnetic flux density at the air-gap center were simulated and compared with the experimental results. Taguchi method was applied to investigate the effects of each variables. As a result, the thickness of conductor and magnet was important for the thrust but the thickness of the yoke. The temperature of the conductor was determined by finding the thermal conductivity that was determined by experimentation. Correlation equation relating to the thrust and temperature was proposed by Latin square and Least Square method. The optimum design variables were determined by correlation equation, and compared with simulation results. According to this analysis, thrust force of linear motor was improved about 7% comparing with conventional model.
Degradation Damage Evaluation for Turbine Structural Components by Electrochemical Reactivation Polarization Test
Kwon, Il-Hyun ; Baek, Seung-Se ; Lyu, Dae-Young ; Yu, Hyo-Sun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 7, 2002, Pages 1241~1249
DOI : 10.3795/KSME-A.2002.26.7.1241
The extent of materials deterioration can be evaluated accurately by mechanical test such as impact test or creep test. But it is almost impossible to extract a large test specimen from in-service components. Thus material degradation evaluation by non-destructive method is earnestly required. In this paper, the material degradation for virgin and several aged materials of a Cr-Mo-V steel, which is an candidated as structural material of the turbine casing components for electric power plant, is nondestructively evaluated by reactivation polarization testing method. And, the results obtained from the test are compared with those in small punch(SP) tests recommended as a semi-nondestructive testing method using miniaturized specimen. In contrast to the aged materials up to 1,000hrs which exhibit the degradation behaviors with increased
, the improvement of mechanical property can be observed on the 2,000hrs and 3,000hrs aged materials. This is because of the softening of material due to the carbide precipitation, the increase of ferritic structures and the recovery of dislocation microstructure by long-time heat treatment. The reactivation rates(
) calculated by reactivation current densityt (
) and charge(
) in the polarization curves exhibit a good correlation with
J-T Characterization of Stress Fields Along 3D Semi-Elliptical Interfacial Crack Front
Choi, Ho-Seung ; Lee, Hyung-Yil ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 7, 2002, Pages 1250~1261
DOI : 10.3795/KSME-A.2002.26.7.1250
Many research works have validated the J-T approach to elastic-plastic crack-tip stress fields in a variety of plane strain specimens. To generalize the validity of J-T method, further investigations are however needed for more practical 3D structures than the idealized plane strain specimens. In this work, we perform 3D finite element (FE) modeling of welded plate and straight pipe, and accompanying elastic, elastic-plastic FE analyses. Manual 3D modeling is almost prohibitive, since the models contain semi-elliptical interfacial cracks which require singular elements. To overcome this kind of barrier, we develop a program generating the meshes for semi-elliptical interfacial cracks. We then compare the detailed 3D FE stress fields to those predicted with J-T two parameters. Thereby we extend the validity of J-T application to 3D structures and infer some useful informations for the design or assessment of pipe welds.
Evaluation of 1Cr-1Mo-0.25V Steel Degradation Using Magnetic Barkhausen Noise
Lee, Jong-Min ; Ahn, Bong-Young ; Nahm, Seung-Hoon ; Lee, Seung-Seok ; Lee, Ouk-Sub ; Nam, Young-Hyun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 7, 2002, Pages 1262~1269
DOI : 10.3795/KSME-A.2002.26.7.1262
It is inevitable to evaluate the life of turbine rotor because the operating periods of power plants need to be extended. For the test, seven kinds of specimens with different degradation levels were prepared by the isothermal heat treatment at
. Magnetic methods utilizing Barkhausen noise coercive force(
) were applied to detect the degradation caused by thermal aging. Magnetic property of material is related with domain dynamics and that is affected by the microstructure of material. Therefore
is very sensitive to the microstructure change of the material. With the increase of degradation,
was decreased and this phenomenon is considered due to precipitations and grain size. The result was compared with Vickers hardness(
) and coercive force(
) to detect the relative variation, and was related with
and YS to estimate the change of the mechanical properties with the degradation.
Evaluation of Thin Film Residual Stress through the Theoretical Analysis of Nanoindentation Curve
Lee, Yun-Hee ; Jang, Jae-Il ; Kwon, Dong-Il ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 7, 2002, Pages 1270~1279
DOI : 10.3795/KSME-A.2002.26.7.1270
Residual stress is a dominant obstacle to efficient production and safe usage of device by deteriorating the mechanical strength and failure properties. Therefore, we proposed a new thin film stress-analyzing technique using a nanoindentation method. For this aim, the shape change in the indentation load-depth curve during the stress-relief in film was theoretically modeled. The change in indentation depth by load-controlled stress relaxation process was related to the increase or decrease in the applied load using the elastic flat punch theory. Finally, the residual stress in thin film was calculated from the changed applied load based on the equivalent stress interaction model. The evaluated stresses for diamond-like carbon films from this nanoindentation analysis were consistent with the results from the conventional curvature method.
Effect of Nozzle Scanning in Micro Grooving of Glass by Powder Blasting
Kim, Kwang-Hyun ; Choi, Jong-Sun ; Park, Dong-Sam ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 7, 2002, Pages 1280~1287
DOI : 10.3795/KSME-A.2002.26.7.1280
The old technique of sandblasting which has been used for decoration of glass surface has recently been developed into a powder blasting technique for brittle materials such as glass, silicon and ceramics, capable of producing micro structures larger than
m. This paper describes the performance of powder blasting technique in micro-line grooving of glass and the effect of the number of nozzle scanning on the depth and width of line groove. Experimental results showed that increasing the no. of nozzle scanning resulted in the increase of depth and width in grooves. Increase of width which may cause several problems in the precision machining results from wear of mask film. Therefore, well-controlled masking process is the most important factor for micro machining of glass with accuracy.
Design and Fabrication of 6-Component Forces and Moments Sensor Using a Column Structure
Shin, Hong-Ho ; Kim, Jong-Ho ; Park, Yon-Kyu ; Joo, Jin-Won ; Kang, Dae-Im ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 7, 2002, Pages 1288~1295
DOI : 10.3795/KSME-A.2002.26.7.1288
The column-type sensing element in building and mechanical construction parts was designed as three forces and three moments sensor by attaching strain gages approximately. Compared to conventional multi-component sensor, the designed sensor has high stiffness and low cost. The radius of the column was designed analytically and compared with finite element analysis. The interference errors between components were minimized by using addition and subtraction procedure of signals. The fabricated sensor was tested by using a deadweight force standard machine and a six-component force calibration machine. The calibration results showed that the 6-component forces and moments sensor had interference error less than 7.3 % between
components, and 5.0 % in case of other components.
A Linkage-type Locomotive Mechanism for Colonoscopes
Kim, Kyoung-Dae ; Lim, Hun-Young ; Park, Jong-Oh ; Hong, Yeh-Sun ; Kim, Byung-Kyu ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 7, 2002, Pages 1296~1301
DOI : 10.3795/KSME-A.2002.26.7.1296
In recent years, the pathology in the colon grows up annually since people of all ages prefer to have less fiber and more fat food. Therefore, the colonoscopy is generalized in developed countries. But it requires much time to acquire a dexterous skill to perform an operation and the procedure is painful to the patient. Therefore, some studies on the development of autonomous colonoscope are carried out. In this paper, we propose a new and simple locomotive mechanism that can be propelled by elliptic motion of a leg. It has several legs that have constant phase difference each other and those legs are disposed along the upper and lower of the body. In order to evaluate the performance of locomotive mechanism, we carried out the simulations of moving characteristics and the experiments in the colon of a dead pig.
Thermo-mechanical and Flexural Analysis of WB-PBGA Package Using Moire Interferometry
Han, Bong-Tae ; Joo, Jin-Won ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 7, 2002, Pages 1302~1308
DOI : 10.3795/KSME-A.2002.26.7.1302
Thermo-mechanical and flexural behavior of a wire-bond plastic ball grid array (WB-PBGA) package are characterized by high sensitive moire interferometry. Moire fringe patterns are recorded and analyzed for several bending loads and temperatures. At the temperature higher than
, the inelastic deformation in solder balls become more dominant, so that the bending of the molding compound decreases while temperature increases. The deformation caused by thermally induced bending is compared with that caused by mechanical bending. The strain results show that the solder ball located at the edge of the chip has largest shear strain by the thermal load while the maximum average shear strain by the bending moment occurs in the end solder.
Effect of the Parameter of the Suspension System on the the Vertical Vibration of the Passenger Vehicle
Hur, Hyun-Moo ; Kwon, Young-Pil ; Choi, Kyung-Jin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 7, 2002, Pages 1309~1316
DOI : 10.3795/KSME-A.2002.26.7.1309
The purpose of this study is to analyze the effects of the parameters of the suspension system in railway rolling-stock for KT-23 type passenger vehicle. According to the results of simulation and the field test, Optimal condition was obtained for the stiffness ratio of the primary spring and the secondary of the suspension system. When the stiffness ratio was increased, the vibration was increased on the car body and decreased on the bogie, and ride quality are getting worse because of increase of the vertical natural frequency of the car body. The results of this study are usefull to improve the technology of the ride quality of KT-23 type vehicle.
Analysis of Creep Effective Stress in Austenitic Heat Resistant Steel
Nam, Ki-Woo ; Park, In-Duck ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 7, 2002, Pages 1317~1323
DOI : 10.3795/KSME-A.2002.26.7.1317
This paper describes the comparison of calculated effective stress with experimental one in austenitic heat resistant steels, STS310J1TB and STS310S with and without a small amount of Nb and N. Based on a solute atoms diffusion model, contribution from soluble nitrogen to the high-temperature strength was numerically examined for austenitic heat-resisting Fe-Cr-Ni-N(STS310J1TB) and Fe-Cr-Ni (STS310S) alloys. The solute atmosphere dragging stress of dislocation was calculated in optional dislocation velocity of STS310J1TB and STS310S at
. As a result of the numerical calculation, the solute atmosphere dragging stress of STS310J1TB was about 50 times larger than that of STS310S. When the temperature became high, the maximum value of solute atmosphere dragging stress was small and the velocity of moving dislocation was fast. From the relationship between the dislocation rate and the solute atmosphere dragging stress, the relation of both was proportional and the inclination is about 1 in the level with low velocity of moving dislocation. From above results, the mechanism of dislocation movement in STS310J1TB was the solute atmosphere dragging stress. The solute atmosphere dragging stress, which was calculated from the numerical calculation was close to the effect stress in stress relaxation tests.
Densification Behavior of Aluminum Alloy Powder Mixed with Zirconia Powder Inclusion Under Cold Compaction
Ryu, Hyun-Seok ; Lee, Sung-Chul ; Kim, Ki-Tae ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 7, 2002, Pages 1324~1331
DOI : 10.3795/KSME-A.2002.26.7.1324
Densification behavior of composite powders was investigated during cold compaction. Experimental data were obtained for aluminum alloy powder mixed with zirconia powder inclusion under triaxial compression. The Cap model with constraint factors was implemented into a finite element program (ABAQUS) to simulate compaction responses of composite powders during cold compaction. Finite element results were compared with experimental data for densification behavior of composite powders under cold isostatic pressing and die compaction. The agreements between experimental data and finite element calculations from the Cap model with constraint factors were good.
An Nondestructive Evaluation of Degraded Damage for Superaustenitic Stainless Steel
Kwon, Il-Hyun ; Baek, Seung-Se ; Iino, Y. ; Yu, Hyo-Sun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 7, 2002, Pages 1332~1339
DOI : 10.3795/KSME-A.2002.26.7.1332
This research was undertaken to clarify effects of thermal aging on electrochemical and mechanical properties of superaustenitic stainless steel and to detect the material degradation nondestructively. The steel was artificially aged at
and the mechanical properties were investigated at
using small punch(SP) test. Also, the change in electrochemical properties caused by effects of thermal aging on superaustenitic stainless steel was investigated using electrochemical anodic polarization test in a KOH electrolyte. Carbides and
precipitated in the grain boundaries seem to deteriorate the mechanical properties by decreasing cohesive strength in the grain boundaries and to promote the current density observed in electrochemical polarization curves, The electrochemical and mechanical properties of superaustenitic stainless steel decreased significantly in the specimen aged at
corresponding to the sensitization temperature for conventional austenitic stainless steels.
Finite Element Analysis of the Effect of Centering Groove on Tip Test
Kang, Seong-Hoon ; Im, Yong-Taek ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 7, 2002, Pages 1340~1347
DOI : 10.3795/KSME-A.2002.26.7.1340
Finite element simulations are being widely used to increase the efficiency and effectiveness of design of bulk metal forming processes. In such simulations, proper consideration of friction condition is crucial in obtaining reliable results. For this purpose, tip test based on backward extrusion was proposed recently. In this lest, a cylindrical billet is positioned in a shallow groove of a counter punch for centering purpose and formation of a radial tip is induced on the extruded end of the workpiece. In this study, the effect of centering groove on tip test was investigated. The quantitative ratio of the shear friction factors between the punch and die was numerically determined depending on the shape of centering groove. Also, surface expansion and pressure distribution along the punch and die were considered in order to better understand the reason that friction condition at the punch compared to the one of die was more severe.
Application of Design of Experiments and Numerical Analysis to Optimal Design for Injection Molding Processes of Electrical Parts
Ahn, Jong-Ho ; Choi, Sang-Ryun ; Park, Keun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 7, 2002, Pages 1348~1356
DOI : 10.3795/KSME-A.2002.26.7.1348
The present work concerns the optimal design for injection molding processes by using the design of experiments (DOE) and numerical analysis. The DOE approaches is planned to be able to consider two-way interaction, and have been applied progressively for both mold design and process design. Numerical analyses have been carried out as a design of experiments for mold parameters such as runner specifications and cooling channel configurations. In order to determine optimal process parameters, experiments have been performed for various process conditions with the DOE scheduling. As a result, the quality and productivity of the product have been improved, and the proposed approach can be successfully reflected on the industrial injection molding process of precision electronics parts.
The Study on the Development of Composite Robot Hand for TFT-LCD Glass Transport
Choi, Gi-Han ; Han, Chang-Woo ; Lee, Sang-Ryong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 7, 2002, Pages 1357~1365
DOI : 10.3795/KSME-A.2002.26.7.1357
A robot hand is used to transport the glass substrate in TFT-LCD manufacturing process. Carbon/epoxy composite is one of the best materials for this kind of robot hand application, due to their lightweight, high stiffness, and good damping characteristics. Major requirement of the robot hand is given as allowable deflection under weight loading of glass substrate and robot hand itself. In this thesis, a carbon/epoxy robot hand was analyzed using finite element method and beam theory to determine the deflection of the hand under the loading that is equivalent to actual weight. Because natural frequency is one of the major interests in robot hand design for TFT-LCD manufacturing process, modal analysis is also conducted using finite element method and beam theory. A robot hand was manufactured, and actual deflection and natural frequency were measured to verify the analysis results and compliance to requirement. The test results showed good agreement with analysis results.
Experimental Investigation on the Flow Control in Forward-Backward Extrusion of Piston-Pin for Automobile
Park, Jong-Nam ; Park, Tae-Joon ; Kim, Dong-Hwan ; Kim, Byung-Min ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 7, 2002, Pages 1366~1375
DOI : 10.3795/KSME-A.2002.26.7.1366
In cold forging of piston-pin for automobile parts, the flow defect appears by the dead metal zone. This appearance evidently happens in products with a thin piercing thickness for the dimension accuracy and the decrease of material loss. The best method that can prevent flow defect is removing dead metal zone. The purpose of this study is to investigate the material flow behavior of forward-backward extruded piston-pin through the relative velocity ratio and the stroke control of upper moving punch & container using the flow control forming technique. The finite element simulations are applied to analyse the flow defect, then the results are compared with the plasticine model material experiments. The model experiment results are in good agreement with the FE simulation ones.
Seismic Qualification of the Air Cleaning Units for Nuclear Power Plant Ulchin 5&6
Kim, Jin-Young ; Rhee, Hui-Nam ; Lee, Joon-Keun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 7, 2002, Pages 1376~1383
DOI : 10.3795/KSME-A.2002.26.7.1376
Seismic qualification of the Air Cleaning Units for nuclear power plant Ulchin 5&6 has been performed with the guideline of ASME Section III and IEEE 344 code. By using the structural and geometrical similarity analysis, the three models to be analyzed are condensed into a single model and, at the same time, the excitation forces and other operating loads for each model are encompassed with respect to different loading conditions. As the fundamental frequencies of the structure are found to be less than 33Hz, which is the upper frequency limit of the seismic load, response spectrum analysis using ANSYS is performed in order to combine the modal stresses within the frequency limit. In order to confirm the structural and electric stability of the major components, modal analysis theory is adopted to derive the required response spectrum at the component locations. As the all combined stresses obtained from the above procedures are less than allowable stresses and no mechanical or electrical failures are found from the seismic testing, the authors confirm the safety of the nuclear equipments Air Cleaning Units studied in this paper.
Modeling of Single Fiber Pull-Out Experiment Considering the Effects of Transverse Isotropy
Seol, Il-Chan ; Lee, Choon-Yeol ; Chai, Young-Suck ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 7, 2002, Pages 1384~1392
DOI : 10.3795/KSME-A.2002.26.7.1384
Single fiber pull-out technique has been commonly used to characterize the mechanical behavior of interface in fiber reinforced composite materials. An improved analysis considering the effects of transversely isotropic properties of fiber and the effects of thermal residual stresses in both radial and axial directions along the fiber/matrix interface is developed for the single fiber pull-out test. Although the stress transfer properties across the interface is not much affected by considering the transversely isotropic properties of fiber, interfacial debonding is notably encouraged by the effect. The interfacial shear stress that plays an important role in interfacial debonding is very much affected by the component of axial thermal residual stress in the bonded region, which can induce a two-way debonding mechanism.
Evaluation of Dynamic Characteristics of Rubber Materials Using a Double Cantilever Sandwich Beam Method
Kim, Kwang-Woo ; Choi, Nak-Sam ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 7, 2002, Pages 1393~1400
DOI : 10.3795/KSME-A.2002.26.7.1393
A double cantilever sandwich-beam method has been applied to the evaluation of the frequency dependence of dynamic elastic modulus and material loss factor of EPDM rubbers. The flexural vibration of a double cantilever sandwich-beam specimen with an inserted rubber layer was studied using a finite element simulation in combination with the sine-sweep test. Effects of the rubber layer length on the dynamic characteristics were also investigated: reliable values were measured when the length of the inserted rubber layer was larger than and equal to 50% of the effective specimen length. The values were compared with those obtained by the dynamic mechanical analysis and the simple resonant test. Relationships of the dynamic characteristics of rubbers with frequency could be determined using the least square error method.
An Investigation of Vehicle-to-Vehicle Distance Control Laws Using Hardware-in-the Loop Simulation
Yi, Kyong-Su ; Lee, Chan-Kyu ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 7, 2002, Pages 1401~1407
DOI : 10.3795/KSME-A.2002.26.7.1401
This paper represents an investigation of the vehicle-to-vehicle distance control system using Hardware-in-the-Loop Simulation(HiLS). Control logic is primarily developed and tested with a specially equipped test vehicle. Establishment of an efficient and low cost development tool is a very important issue, and test vehicle approach is costly and time consuming. HiLS method is useful in the investigation of driver assistance and active safety systems. The HiLS system consists of a stepper motor for throttle control, a hydraulic brake system with an electronic vacuum booster, an electronic controller unit, a data logging computer which are used to save vehicle states and signals of actuator through a CAN and a simulation computer using mathematical vehicle model. Adaptation of a CAN instead of RS-232 Serial Interface for communication is a trend in the automotive industry. Since this environment is the same as a test vehicle, a control logic verified in laboratory can be easily transferred to a test vehicle.
A Study on the Improvement of Shape Optimization associated with the Modification of a Finite Element
Sung, Jin-Il ; Yoo, Jeong-Hoon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 7, 2002, Pages 1408~1415
DOI : 10.3795/KSME-A.2002.26.7.1408
In this paper, we investigate the effect and the importance of the accuracy of finite element analysis in the shape optimization based on the finite element method and improve the existing finite element which has inaccuracy in some cases. And then, the shape optimization is performed by using the improved finite element. One of the main stream to improve finite element is the prevention of locking phenomenon. In case of bending dominant problems, finite element solutions cannot be reliable because of shear locking phenomenon. In the process of shape optimization, the mesh distortion is large due to the change of the structure outline. So, we have to raise the accuracy of finite element analysis for the large mesh distortion. We cannot guarantee the accurate result unless the finite element itself is accurate or the finite elements are remeshed. So, we approach to more accurate shape optimization to diminish these inaccuracies by improving the existing finite element. The shape optimization using the modified finite element is applied to a two and three dimensional simple beam. Results show that the modified finite element has improved the optimization results.
Effects of Combined Environmental Factors on Mechanical and Thermal Analysis Properties of Graphite/Epoxy Composites
Lee, Sang-Jin ; Lee, Jong-Keun ; Yoon, Sung-Ho ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 7, 2002, Pages 1416~1425
DOI : 10.3795/KSME-A.2002.26.7.1416
In this study, the effects of combined environmental factors on mechanical and thermal analysis properties of graphite/epoxy composites were evaluated by the use of an accelerated aging test. Environmental factors such as temperature, moisture. and ultraviolet were considered. A xenon-arc lamp was utilized for ultraviolet light. and exposure times of up to 3000 hours were applied. Several types of specimens - tensile. bending, and shear specimens those are transverse to the fiber direction, and bending specimens those are parallel to the tiber direction - were used to investigate the effects of environmental factors on mechanical properties of the composites. Also, glass transition temperature, storage shear modulus, loss shear modulus, and tan
were measured as a function of exposure times through a dynamic mechanical analyzer. In addition. a suitable testing method for determining the effect of environmental factors on mechanical properties is suggested by comparing the results from using two different types of strain measuring sensors. Finally, composite surfaces exposed to environmental factors were examined using a scanning electron microscope.
Numerical Simulation of High-Velocity Oblique Impacts of Yawed Long Rod Projectile Against Thin-Plate
Yoo, Yo-Han ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 7, 2002, Pages 1426~1437
DOI : 10.3795/KSME-A.2002.26.7.1426
Using the Lagrangian explicit time-integration finite element code NET3D which can treat three-dimensional high-velocity impact problems, oblique penetration processes of long rod projectile with yaw against thin plate are simulated. Through the comparison of simulation result with experimental result and other code`s computational result, the adaptability and accuracy of NET3D is evaluated under the complex situation in which yaw angle and oblique angle exist simultaneously. Main research contents to be handled in this paper include the followings. First, the accuracy and efficiency estimation of NET3D code result obtained from the oblique penetration simulations of long rod projectile with yaw against thin plate. Second, the effect of increasing impact velocity. Third, the effect of initial yaw for the spaced-plate target. Residual velocities, residual lengths, angular velocities, and final deformed configurations obtained from the NET3D computations are compared with the experimental results and other code`s computational results such as Eulerian code MESA and Lagrangian code EPIC. As a result of comparisons, it has been found that NET3D code is superior to EPIC code and MESA code in the prediction capability of residual velocity and residual length of penetrator. The key features obtained from the experiment can be successfully reproduced through NET3D simulations. Throughout the study, the applicability and accuracy of NET3D as a metallic armor system design tool is verified.
Design and Performance Evaluation of Impact Type Actuator Using Magnetic Force
Min, Hyun-Jin ; Lim, Hyung-Jun ; Kim, Byung-Kyu ; Kim, Soo-Hyun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 7, 2002, Pages 1438~1445
DOI : 10.3795/KSME-A.2002.26.7.1438
For robotic endoscope, some researchers suggest pneumatic actuators based on inchworm motion. But, the existing endoscopes have not been replaced completely because human intestine is very sensitive and susceptible to damage. We design and test a new locomotion of robotic endoscope that allows safe maneuverability in the human intestine. The actuating mechanism is composed of two solenoids at each side and a single permanent magnet. When the current direction is reversed, repulsive force and attractive at the opposition side propels permanent magnet. Impact force against robotic endoscope transfers momentum from moving magnet to endoscope capsule. The direction and moving speed of the actuator can be controlled by adjustment of impact force. Modeling and simulation experiments are carried out to predict the performance of the actuator. Simulations show that force profile of permanent magnet is the dominant factor for the characteristic of the actuator. The results of simulations are verified by comparing with the experimental results.
Unmanned Turning Process Control Based on Spindle-Motor Power Characteristics
Pak, Chang-Ho ; Hong, Sung-Hahm ; Lee, Byeong-Huee ; Huh, Kun-Soo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 7, 2002, Pages 1446~1452
DOI : 10.3795/KSME-A.2002.26.7.1446
In the turning process, the feed is usually selected by a machining operator considering workpiece, cutting tool and depth of cut. Even if this selection can avoid power saturation or tool breakage, it is usually conservative compared to the capacity of the machine tools and can reduce the productivity significantly. This paper proposes a selection method of the feed and the reference cutting force based on MRR(material removal rate), maximum spindle power and specific energy. In order to estimate and control cutting force accurately in transient and steady state, this study utilizes a synthesized cutting force estimation method and a Fuzzy controller. The experimental results show that these systems can be useful for the unmanned turning process.
Evaluation of Creep Fatigue Crack Growth Behavior of 9Cr Steel Employing Creep Reversal Parameter
Ma, Young-Wha ; Baek, Un-Bong ; Yoon, Kee-Bong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 26, issue 7, 2002, Pages 1453~1460
DOI : 10.3795/KSME-A.2002.26.7.1453
Creep-fatigue crack growth models have been proposed employing
as a crack tip parameter characterizing the time-dependent crack growth. The basic assumptions made in these previous models were ideal creep reversal conditions such as no creep reversal and complete creep reversal condition. Due to this assumption, the applicability of the models was limited since they did not consider partial creep reversal condition which is usually observed in many engineering metals at high temperature. In this paper the creep reversal parameter, Temperature;
, which was defined by Grover, is critically evaluated to quantity the extent of partial creep reversal at the crack tip. This approach does not rely on any simplifying assumptions regarding the extent of the amount of creep reversal during the unloading part of a trapezoidal fatigue cycles. It is shown that the
value calculated for 9Cr steel agrees well with the experimentally measured one. It is argued that the extent of improvement is not significant when the result is compared with that of the conventional model which has an assumption of full creep reversal behavior.