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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
Selecting the target year
A Study on Fatigue Design Automation of Plug- and Ring-type Gas-welded Joints of STS301L Taking Welded Residual Stress into Account
Baek, Seung-Yeb ; Yun, Ki-Ho ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 9, 2010, Pages 1137~1143
DOI : 10.3795/KSME-A.2010.34.9.1137
This paper presents a fatigue design method for plug- and ring-type gas-welded joints, which takes into account the effects of welding residual stress. To develop this method, we simulated the gas-welding process by performing nonlinear finite element analysis (FEA) To validate the FEA results, numerically calculated residual stresses in the gas welds were then compared with experimental results obtained by the hole-drilling method. To evaluate the fatigue strength of plug- and ring-type gas-welded joints influenced by welding residual stresses, the use of stress amplitude
, which includes the welding residual stress in gas welds, is proposed
on the basis of a modified Goodman equation that includes the residual stress effects. Using the stress amplitude
at the hot spot point of gas weld, the relations obtained as the fatigue test results for plug and ring type gas welded joints having various dimensions and shapes were systematically rearranged to obtain the
relationship. It was found that more systematic and accurate evaluation of the fatigue strength of plug- and ring-type gas-welded joints can be achieved by using
Design and Simulation of Small Bio-Inspired Jumping Robot
Ho, Thanhtam ; Choi, Sung-Hac ; Lee, Sang-Yoon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 9, 2010, Pages 1145~1151
DOI : 10.3795/KSME-A.2010.34.9.1145
In this paper, we discuss the design and simulation of a jumping-robot mechanism that is actuated by SMA (shape memory alloy) wires. We propose a jumping-robot mechanism; the structure of the robot is inspired by the musculoskeletal system of vertebrates, including humans. Each robot leg consists of three parts (a thigh, shank, and foot) and three kinds of muscles (gluteus maximus, rectus femoris, and gastrocnemius). The jumping capability of the robot model was tested by means of computer simulations, and it was found that the robot can jump to about four times its own height. This robot model was also compared with another model with a simpler structure, and the performance of the former, which was based on the biomimetic design, was 3.3 times better than that of the latter in terms of the jumping height. The simulation results also verified that SMA wires can be suitable actuators for small jumping robots.
Optimization of Design Variables of Detection Algorithm for Loss of Balance Using a Linear Internal Model
Kim, Kwang-Hoon ; Kim, In-Su ; Son, Kwon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 9, 2010, Pages 1153~1160
DOI : 10.3795/KSME-A.2010.34.9.1153
The detection algorithm for loss of balance had three main parts: one for processing data, another for constructing an internal model, and a third for detecting the loss of balance. The part related to the internal model is the most important part of the algorithm. The purpose of this study is to evaluate the effect of variables associated with the internal model on the success rate of the algorithm. The internal model depends on the type of linearization adopted and the operating period of the algorithm. The design variables were evaluated by performing sensitivity analysis of the variables of the internal model in order to obtain the success rate of the algorithm. The results showed that the most sensitive variable was the period and the period of 0.3 s yielded the highest success rate of 97.1%. Further, the ranges of the design variables that can facilitate a success rate of over 95% are presented.
Experimental Study of the Effect of Shortening of Life of Tapered Roller Bearings when Subjected to Excessive Axial Pre-Load
Park, Jong-Won ; Kim, Hyoung-Eui ; Kim, Jong-Ock ; Sim, Yang-Jin ; Jung, Won-Wook ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 9, 2010, Pages 1161~1166
DOI : 10.3795/KSME-A.2010.34.9.1161
Tapered roller bearings are core components of rotating machine parts and are simultaneously subjected to axial and radial loads. Life-shortening effect was particularly evident in the case of tapered roller bearings used in the input and output shafts of transmission; this shortening of life was a result of excessive axial pre-load, which is common in the transmission assembly line. In this study, we derived an equation for evaluating the life of tapered roller bearings subjected to excessive pre-load by using accelerated life test data. The DOE(Design Of Experiment) method and FEA(Finite Element Analysis) was used for determining the condition for performing an accelerated life test. This equation for evaluating the service life of the bearings was derived by analyzing the Weibull distribution of the test results. Using the derived equation the life evaluated was 6-7 times longer than that evaluated by the conventional
bearing-life equation. The results of this study will be helpful in predicting the life of tapered roller bearings subjected to excessive pre-load and in designing reliable rotating machines.
A Study on Forming of Silencer Case Using Virtual Tryout Method
Ko, Dae-Lim ; Lee, Kyung-Sick ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 9, 2010, Pages 1167~1173
DOI : 10.3795/KSME-A.2010.34.9.1167
Forming of a silencer case was studied using a virtual tryout method. First, the appropriate blank shape was determined by cutting off the undeformed part of the rectangular blank. Then drawbeads were designed such that the formation of wrinkles on the shoulders and pipe connection can be prevented. Finally, the shape bead was designed such that fracture and formation of wrinkles around the pipe connection can be avoided. The prototype of the silencer case was manufactured in accordance with the conditions of the virtual tryout process. By comparing the formability of the prototype with the results of finite element analysis, it was found that the forming of the prototype agreed well with the results of analysis.
Study on the Lateral Dynamic Crush Strength of a Spacer Grid Assembly for a LWR Nuclear Fuel Assembly
Song, Kee-Nam ; Lee, Sang-Hoon ; Lee, Soo-Bum ; Lee, Jae-Jun ; Park, Gyung-Jin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 9, 2010, Pages 1175~1183
DOI : 10.3795/KSME-A.2010.34.9.1175
A spacer grid assembly is one of the most important structural components in a Light Water Reactor(LWR) nuclear fuel assembly. In the case of the Zircaloy spacer grid assembly, the primary design consideration is to ensure that lateral dynamic crush strength of the spacer grid assembly is sufficient to resist design basis loads and thereby prevent seismic accidents, without a significant increase in the hydraulic head loss for the reactor coolant in the reactor core. In this study, factors affecting the lateral dynamic crush strength of a spacer grid assembly were analyzed by performing lateral dynamic crush tests and finite element analyses. Further, an effective and economical method to enhance the lateral dynamic crush strength of the spacer grid assembly is proposed.
Fatigue Life and Stress Spectrum of Wing Structure of Aircraft
Kang, Ki-Weon ; Koh, Seung-Ki ; Choi, Dong-Soo ; Kim, Tae-Sung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 9, 2010, Pages 1185~1191
DOI : 10.3795/KSME-A.2010.34.9.1185
Aged aircraft have several cracks as a results of long-term service, and these cracks affect the safety and decrease the rate of operation of the aircraft. To solve these problems, crack propagation analysis should be performed to determine the service life at fatigue critical location(FCL). It is, however, almost impossible to obtain the stress spectrum, which is crucial for crack propagation analysis of the FCLs of wing structure of aged aircraft. In this study, to analyze the fatigue crack propagation behavior at the FCL of an aged aircraft, first finite element analysis is performed for a 3D geometry model of the aircraft wing structure, which is obtained using CATIA based on the paper drawings. Then, the transfer function and stress-spectrum of the FCL are derived using the load factor data and the FEA results. Finally, the crack propagation rates of the FCL are evaluated using the commercial software, NASGRO 6.0.
Vibration Fatigue Analysis for Multi-Point Spot-Welded SPCC Structure Considering Change of Dynamic Response
Kang, Ki-Weon ; Chang, Il-Joo ; Kim, Jung-Kyu ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 9, 2010, Pages 1193~1199
DOI : 10.3795/KSME-A.2010.34.9.1193
Spot welding is the primary method of joining sheet metals in the automotive industry. As automobiles are subjected to fatigue loading, some spot welds may fracture before the whole system has failed. This local fracture of spot welds may lead to change in the dynamic response and consequently affect fatigue behavior of an automobile. Therefore, this change in dynamic response should be taken into consideration to assess the fatigue life of structures subjected to spectrum loading, such as automobiles. In this study, vibration fatigue analysis was performed by taking into consideration the change in the dynamic response due to accumulated damage at spot-welded parts. Fatigue tests were carried out on tensile-shear spot-welded specimens under constant amplitude loading condition. And the fatigue life of spot welds under spectrum loading was predicted using vibration fatigue analysis method based on finite element analysis.
Development of a Fatigue Testing System for Micro-Specimens
Kim, Chung-Youb ; Sharpe, W.N. ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 9, 2010, Pages 1201~1207
DOI : 10.3795/KSME-A.2010.34.9.1201
In this study, a fatigue testing system capable of performing load-controlled tension-tension tests for micro-specimens was developed by using an electro-magnetic actuator. Using this system, fatigue testing as well as tensile testing can be performed over a wide range of loading frequencies. Further, a new laser interferometric strain/displacement gage was used during fatigue testing to obtain high-resolution measurements of the cyclic deformation of thin films. Since the testing machine and the displacement gage are stable and show quick responses, the displacement can be measured instantaneously and continuously during fatigue testing, and high-resolution results can be obtained.
Mechanical Properties of Elastomeric Composites with Atmospheric-Pressure Flame Plasma Treated Multi-Walled Carbon Nanotubes and Carbon Black
Sung, Jong-Hwan ; Lee, Dong-Joo ; Ryu, Sang-Ryeoul ; Cho, Yi-Seok ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 9, 2010, Pages 1209~1215
DOI : 10.3795/KSME-A.2010.34.9.1209
The effects of multi-walled carbon nanotube (MWCNT) content, carbon black (CB) content, atmospheric-pressure flame plasma (APFP) treatment, and acid treatment on the mechanical properties of elastomeric composites were investigated. For pure or filled rubbers with the given amount of CB (20 and 40 phr), the tensile strength and modulus of the elastomeric composites increase similarly with the MWCNT content. A composite with APFP-treated MWCNTs shows a hardening effect (high strength, high modulus, and high ductility) unlike the one with untreated MWCNTs. On the other hand, a composite with APFP-treated CB shows a softening effect (high strength, low modulus, and high ductility), which is unlike a composite with untreated CB. As the refluxing time increases from 1 h to 2 h and the sulfuric acid concentration increases from 60% to 90%, the tensile strength and modulus of a composite decrease. Thus, it is found that the MWCNT content, CB content, APFP treatment, sulfuric acid concentration, and refluxing time have an important effect on the mechanical properties of NBR composites.
Design Concept and Technology Development of a Double-Wall-Tube Steam Generator
Nam, Ho-Yun ; Choi, Byoung-Hae ; Kim, Jong-Bum ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 9, 2010, Pages 1217~1225
DOI : 10.3795/KSME-A.2010.34.9.1217
The possibility of a sodium-water reaction occurring in a conventional single-wall-tube steam generator in an SFR is a major problem. To improve the reliability of a steam generator, a double-wall-tube steam generator that can reduce the possibility of the occurrence of a sodium-water reaction is being developed. Current developments are focusing on improving the heat-transfer capability of a double-wall tube; further, the development of a leak-detection method to detect the occurrence of a sodium-water reaction during the reactor operation is also underway. In this study, new concepts, which will solve the above-mentioned problems, have been developed. Accordingly, a double-wall tube has been designed, fabricated, and mechanically tested for the purpose.
Cracking Near a Hole on a Heat- Resistant Alloy Subjected to Thermo-Mechanical Cycling
Li, Feng-Xun ; Kang, Ki-Ju ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 9, 2010, Pages 1227~1233
DOI : 10.3795/KSME-A.2010.34.9.1227
In the hot section of a gas turbine, the turbine blades were protected from high temperature by providing a thermal barrier coating (TBC) as well as by cooling air flowing through internal passages within the blades. The cooling air then passed through discrete holes on the blade surface, creating a film of cooling air that further protects the surface from the hot mainstream flow. The holes are subjected to stresses resulting from the lateral growth of thermally grown oxide, the thermal expansion misfit between the constituent layers, and the centrifugal force due to high-speed revolution; these stresses often result in cracking. In this study, the deformation and cracks occurring near a hole on a heat-resistant alloy subjected to thermo-mechanical cycling were investigated. The experiment showed that cracks formed around the hole depending on the applied stress level and the number of cycles. These results could be explained by our analytic solution.
Design and Construction of a Loom for Obtaining Ultra-Light Metal Structure
Kim, Pan-Su ; Kang, Ki-Ju ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 9, 2010, Pages 1235~1240
DOI : 10.3795/KSME-A.2010.34.9.1235
Wire-woven Bulk Kagome (WBK) is fabricated by assembling helically formed wires in six directions. To date, WBK samples have been assembled manually. For industrial application, the assembly process must be automated. Furthermore, if WBK is to be fabricated using flexible wires that cannot maintain their helical shape during fabrication, a specialized automatic machine, i.e., a loom needs to be developed. In this work, we designed and constructed a loom for fabricating WBKs using flexible wires. This loom is operated by one rotation of the upper plate, two translations of the insertion device, and insertion of wires. So-called "comb devices" are placed between multiple layers of Kagome nets to prevent the wires that are already in place from getting entangled with those that are being inserted. This loom can be also used to fabricate semi-WBKs composed of helically formed wires and rigid straight wires.
High-Temperature Structural-Analysis Model of Process Heat Exchanger for Helium Gas Loop (I)
Song, Kee-Nam ; Lee, Heong-Yeon ; Kim, Yong-Wan ; Hong, Seong-Duk ; Park, Hong-Yoon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 9, 2010, Pages 1241~1248
DOI : 10.3795/KSME-A.2010.34.9.1241
In large-scale production of hydrogen, a PHE (Process Heat Exchanger) is a key component because the heat required to carry out the Sulfur-Iodine chemical reaction that yields hydrogen is transferred from a VHTR (Very High Temperature Reactor) by the PHE. Korea Atomic Energy Research Institute established a helium gas loop for conducting performance test of components that are used in the VHTR. In this study, as a part of high-temperature structural-integrity evaluation of a designed PHE prototype that is scheduled to be tested in the helium gas loop, we carried out high-temperature structural-analysis modeling, thermal analysis, and thermal-expansion analysis for the designed PHE prototype. An appropriate constraint condition is proposed at the end of the in-flow and out-flow pipelines of the primary and secondary coolants and the proposed constraint condition will be applied to the design of the performance-test loop setup for the designed PHE prototype.
A Study of the Variation in Intensifier Performance Characteristics Varying with Pressure and Temperature
Kim, Hyoung-Eui ; Lee, Gi-Chun ; Kim, Jae-Hoon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 9, 2010, Pages 1249~1255
DOI : 10.3795/KSME-A.2010.34.9.1249
An ultra high- pressure system generally consists of a hydraulic power unit, an oil supply unit, an electrical power supply device, and an electrical control device. The hydraulic power unit supplies the hydraulic power to the intensifier to create generate ultra high pressure. The intensifier amplifies increases the pressure using the oil supplied from by the hydraulic power unit. The electrical supply devices and control devices maintain are provided for the electric motors, valves, and sensors. In this study, instead of a flow-control device, a pressure-control type device was mounted on a manifold block in the hydraulic power unit instead of the flow-control type. A servo valve was fitted in the intensifier, and the performance characteristics of the intensifier varied according to the variations of in the pressure cycle and with the temperature of the operating oil in the hydraulic power unit.
Evaluation of Vibration Fatigue Life of Shipboard Equipment Made of Aluminum Alloy A356
Cho, Ki-Dae ; Kim, Jie-Eok ; Yang, Sung-Chul ; Jung, Hwa-Young ; Kang, Ki-Weon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 9, 2010, Pages 1257~1263
DOI : 10.3795/KSME-A.2010.34.9.1257
The naval structure exposes to environmental vibration of shafted propeller propulsion and engine vibration. The shipboard equipments are developed compliance to MIL-STD-167-1A. For this purpose, vibration fatigue life of shipboard equipment for long lives should be estimate via an analytical approach and vibration test. In this paper, High cycle fatigue strength of cast aluminum alloy A356 using shipboard equipment was evaluated by 14 S-N method. The stress applied on the structure is evaluated by an analytical method(frequency response analysis with sinusoidal input and a fatigue evaluation) to simulate a MIL-STD-167-1A test. The frequency with the maximum equivalent stress is shown by Max. test frequency and the vibration fatigue life of shipboard equipment was estimated by Miner's rule.
Development and Application of Life-Assessment Guidelines for Fossil-Fuel Power Plant Facilities in Korea
Choi, Woo-Sung ; Song, Gee-Wook ; Kim, Bum-Shin ; Hyun, Jung-Seob ; Heo, Jae-Sil ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 9, 2010, Pages 1265~1272
DOI : 10.3795/KSME-A.2010.34.9.1265
In view of the frequent start-ups and load changes in the recent past, there is a need for fossil-fuel power plants to be more efficient and reliable for long-term operation. Under high-temperature and high-pressure conditions, severe creep and fatigue damages can occur in major plant facilities, particularly, turbines and boilers. For highly stable operation and better maintenance, various techniques that facilitate a systematic assessment of the service life of critical facilities have been developed. However, to date, in Korea, to evaluate the remaining life of major facilities of fossil power plant, qualitative or semiquantitative analyses are carried out without following any standard guidelines or procedure. In this study, a standard code for assessing the remaining life of major plant facilities is proposed. This code takes into account creep and fatigue damage, which are generally accepted as dominant causes of damage to facilities. KEPIC (Korea Electric Power Industry code) is scheduled to include this guideline in 2010.
Development of an Integrity Evaluation System (WIES) for Fuel Channels in CANDU Reactors
Choi, Sung-Nam ; Kim, Hyung-Nam ; Yoo, Hyun-Joo ; Kwon, Dong-Kee ; Hwang, Won-Gul ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 9, 2010, Pages 1273~1279
DOI : 10.3795/KSME-A.2010.34.9.1273
Pressure tubes at the CANada Deuterium Uranium (CANDU) nuclear power plants are periodically inspected in accordance with the CSA N285.4 code. If flaws that do not satisfy the criteria given in CSA N285.4 are detected, the code permits a fitness-for-service assessment to determine the acceptability of the flawed pressure tubes. In this paper, the Wolsong In-service Evaluation System (WIES) is introduced; this system has been developed for the assessment of the flawed pressure tubes and is based on CSA N285.8. Since the system evaluates the integrity of flawed pressure tubes exactly and promptly during an in-service inspection, it will help in operating the Wolsong nuclear power plants without prolonging the outage period.
RCM Based Failure-Prediction System for Equipment
Song, Gee-Wook ; Kim, Bum-Shin ; Choi, Woo-Sung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 9, 2010, Pages 1281~1286
DOI : 10.3795/KSME-A.2010.34.9.1281
Power plants have many components and equipment. It is difficult for operators to know the time of failure or the equipment that fails. Plants incur heavy economic losses due to unexpected failure. The equipment in power plants is constantly monitored by various sensors and instruments. However, prevention of failure is very difficult. Therefore, engineers are developing many types of failure-alarm systems that can detect the abnormal functioning of equipment. Such failure-alarm systems inform only about the abnormal functioning of equipment and do not indicate the cause of failure or the parts that have failed. In this study, we have developed a failure-prediction system that can provide details on the cause of trouble and the maintenance method.
Analysis of Photoelastic Stress Field Around Inclined Crack Tip by Using Hybrid Technique
Chen, Lei ; Seo, Jin ; Lee, Byung-Hee ; Kim, Myung-Soo ; Baek, Tae-Hyun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 9, 2010, Pages 1287~1292
DOI : 10.3795/KSME-A.2010.34.9.1287
In this paper, a hybrid technique is presented. First, the isochromatic fringe data of a given set of points are calculated by the finite element method and are used as input data in complex variable formulations. Then the numerical model of the specimen with a central inclined crack is transformed from the physical plane to the complex plane by conformal mapping. The stress field is analyzed and the mixed-mode stress intensity factors are calculated for this complex plane. The stress intensity factors are calculated by the finite element method as well as by a theoretical method and compared with each other. In order to conveniently compare these values with each other, both actual and regenerated photoelastic fringe patterns are multiplied by a factor of two and sharpened by digital image processing.
Behavior of Elastic and Plastic Limit Loads of Thinned Elbows Observed During Real-Scale Failure Test Under Combined Load
Lee, Sung-Ho ; Lee, Jeong-Keun ; Park, Chi-Yong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 9, 2010, Pages 1293~1298
DOI : 10.3795/KSME-A.2010.34.9.1293
In most power plants, wall thinning in carbon-steel pipes due to flow-accelerated corrosion is one of the major aging phenomena, and it reduces the load-carrying capacity of the piping system. Various types of wall-thinning defects were manufactured in real-scale elbows, and monotonic in-plane bending tests were performed under internal pressure to evaluate the failure behavior of the elbows. In this paper, the behavior of elastic and plastic limit leads of locally thinned elbows in a real-scale failure test is presented. The loads determined on the basis of TES (twice elastic slope) were considered to be the limit loads of locally thinned elbows so that the integrity of the thinned elbows could be maintained, even when a small amount of plastic deformation might have occurred.
Experimental Investigation of Working Fracture in Silicon Steel Strip Occurring Due to Change in Roll-Gap Profile in Cold Rolling
Byon, Sang-Min ; Lee, Jae-Hyeon ; Kim, Sang-Rok ; Choi, Hyeon-Sik ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 9, 2010, Pages 1299~1304
DOI : 10.3795/KSME-A.2010.34.9.1299
We examined the working fracture behavior of a silicon-steel strip caused by deformation deviation by performing a pilot rolling test. The deformation deviation resulted in the edges (or center portion) of the strip being stretched and the other parts being compressed in the rolling direction; this was because of different degrees of deformation in these parts. We designed roll grooves shape to reflect the role of roll bending, which generates waviness in the strip in an actual cold rolling process, into the pilot rolling test. The material used in the rolling test was highsilicon steel (about 3%). The results of the test showed that the type of fracture in the strip specimen varied with the magnitude of the deformation deviation. The tensile stress produced at the strip edges because of the center waviness in the rolling direction was a crucial factor that resulted in edge cracking and a zigzag-shaped fracture at the center.
Robust Optimal Design of Disc Brake Based on Response Surface Model Considering Standard Normal Distribution of Shape Tolerance
Lee, Kwang-Ki ; Lee, Yong-Bum ; Han, Seung-Ho ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 9, 2010, Pages 1305~1310
DOI : 10.3795/KSME-A.2010.34.9.1305
In a practical design process, the method of extracting the design space information of the complex system for verifying, improving, and optimizing the design process by taking into account the design variables and their shape tolerance is very important. Finite element analysis has been successfully implemented and integrated with design of experiment such as D-Optimal array; thus, a response surface model and optimization tools have been obtained, and design variables can be optimized by using the model and these tools. Then, to guarantee the robustness of the design variables, a robust design should be additionally performed by taking into account the statistical variation of the shape tolerance of the optimized design variables. In this study, a new approach based on the use of the response surface model is proposed; in this approach, the standard normal distribution of the shape tolerance is considered. By adopting this approach, it is possible to simultaneously optimize variables and perform a robust design. This approach can serve as a means of efficiently modeling the trade-off among many conflicting goals in the applications of finite element analysis. A case study on the robust optimal design of disc brakes under thermal loadings was carried out to solve multiple objective functions and determine the constraints of the design variables, such as a thermal deformation and weight.
Finite Element Analysis of Straight Slot Welding and Characteristics of the Weld Residual Stress Distribution
Park, Chi-Yong ; Lee, Kyoung-Soo ; Kim, Maan-Won ; Song, Ki-Oh ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 9, 2010, Pages 1311~1316
DOI : 10.3795/KSME-A.2010.34.9.1311
In this study, straight slot welding was carried out using a 316L stainless steel test block, and numerical simulation of the slot weld process was performed using finite element analysis. Data on the residual stress were obtained at equally spaced points on the top surface of the test block along directions parallel and perpendicular to the welding direction. After electrolytic polishing of the top surface of the block, the residual stress was measured by the X-ray diffraction method. The calculated weld residual stresses were compared with the measured data, and they were in good agreement with the data. The weld residual stress distribution inside the plate was determined from the results of finite element analysis, and the characteristics of the distribution were discussed in detail in this paper.
Distribution Characteristics of Weld Residual Stress on Butt Welded Dissimilar Metal Plate
Lee, Kyoung-Soo ; Park, Chi-Yong ; Kim, Maan-Won ; Park, Jai-Hak ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 9, 2010, Pages 1317~1323
DOI : 10.3795/KSME-A.2010.34.9.1317
In this study, the weld residual stress distribution at a dissimilar-metal welded plate of low alloy carbon steel and stainless steel, which are widely used in nuclear power plants, was characterized. A plate mock-up with butt welding was fabricated using SA 508 low alloy steel and Type 304 stainless steel plates and the residual stresses were measured by the X-ray diffraction method after electrolytic polishing of the plate specimen. Finite element analysis was carried out in order to simulate the butt welding of dissimilar metal plate, and the calculated weld residual stress distribution was compared with that obtained from the measured data. The characteristics of the three-dimensional residual stress distribution in a butt weld of dissimilar metal plates were investigated by comparing the measured and calculated residual stress data.
Determination of Maintenance Period and Failure Probability for Turbine Using Maintenance Record
Song, Gee-Wook ; Koo, Jae-Raeyang ; Choi, Woo-Sung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 9, 2010, Pages 1325~1330
DOI : 10.3795/KSME-A.2010.34.9.1325
The breakdown of any critical component of a turbine results in the outage of power plants. Unexpected failure decreases equipment utilization and causes enormous economic losses. Currently, we conduct conservative preventive maintenance for a maintenance period that is proposed by a vendor. In the rapidly changing business environment, reliability-based maintenance is required in order to remain competitive and reduce maintenance costs while maintaining the reliability of equipment. In order to determine an appropriate maintenance period for guaranteeing reliability, we must determine the failure probability by carefully analyzing the failure history of the equipment. In this study, we created a database of failure history for power-plant turbines, predicted the best repair time using the Weibull function, and investigated how the appropriate maintenance cycle can be determined.
Optimization of Preventative Maintenance Cycle for Equipments of Pumped-Storage Power Plant by Taking into Account Reliability and Economical Efficiency
Kim, Jong-Sung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 34, issue 9, 2010, Pages 1331~1338
DOI : 10.3795/KSME-A.2010.34.9.1331
Recently, the need for improving the economical efficiency of pumped-storage power plants has increased because of the decrease in the availability of electricity caused by an increase in the consumption of electricity at night. Therefore, a preventative maintenance cycle, especially an overhaul cycle, is required. Unconditional extension cannot be implemented because it may cause unanticipated failures due to insufficient maintenance. Therefore, in this study, a methodology for optimizing the preventative maintenance cycle by taking into account both reliability and economical efficiency is presented; this methodology has been developed by reviewing previous studies on reliability and considering the characteristics of pumped-storage power plants. Finally, an extended overhaul cycle is derived by applying this methodology to a domestic pumped-storage power plant.