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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Transactions of the Korean Society of Mechanical Engineers A
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Journal DOI :
The Korean Society of Mechanical Engineers
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Volume & Issues
Volume 38, Issue 12 - Dec 2014
Volume 38, Issue 11 - Nov 2014
Volume 38, Issue 10 - Oct 2014
Volume 38, Issue 9 - Sep 2014
Volume 38, Issue 8 - Aug 2014
Volume 38, Issue 7 - Jul 2014
Volume 38, Issue 6 - Jun 2014
Volume 38, Issue 5 - May 2014
Volume 38, Issue 4 - Apr 2014
Volume 38, Issue 3 - Mar 2014
Volume 38, Issue 2 - Feb 2014
Volume 38, Issue 1 - Jan 2014
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Effect of Specimen Orientation on Fatigue Crack Growth Behavior in Friction Stir Welded Al7075-T651 Joints
Jeong, Yeui Han ; Kim, Seon Jin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 12, 2014, Pages 1317~1323
DOI : 10.3795/KSME-A.2014.38.12.1317
The aim of this paper is to investigate the effects of crack orientation on fatigue crack growth behavior in friction stir welded (FSWed) Al 7075-T651. Fatigue crack growth testing was conducted on compact tension (CT) specimens machined from the friction stir welds and the base metal under constant stress intensity factor range control. Tests were performed with the crack propagating nominally perpendicular to the weld line (termed the TL specimen) and the crack propagating in a parallel direction of the weld line (termed the LT specimen), and with three different constant stress intensity factor ranges. Both these specimen orientations were found to have a considerable effect on the fatigue crack growth behavior. Paris`s law was adopted for the analysis of experimental results; the exponent m of the WM-LT specimen was determined to be 3.56, which was the largest value in this experimental conditions.
Dispersion Pattern Simulation of Tungsten Impactors According to Mass and Shape of Explosives
Sakong, Jae ; Woo, Sung-Choong ; Bae, Yong-Woon ; Choi, Yeoun-Jin ; Cha, Jung-Phil ; Ga, In-Han ; Kim, Tae-Won ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 12, 2014, Pages 1325~1333
DOI : 10.3795/KSME-A.2014.38.12.1325
The dispersion pattern of a near miss neutralizer has a great effect on the disablement of a threatening projectile. This study numerically investigated the dispersion pattern of cylindrical tungsten impactors by an explosion in the near miss neutralizer. The mass and shape of the explosive were considered as influencing factors on the dispersion pattern. The explosives were set using two shape models: a parallel shape with the same upper and lower thicknesses and a tapered shape with different upper and lower thicknesses. In the simulation results, the dispersed impactors formed a ring-shaped pattern on a two-dimensional plane in an arbitrary space. In addition, the fire net area increased with the explosive mass when the explosive shapes were identical. In particular, the tapered shape explosive formed a larger fire net area than the parallel shape explosive. Based on the analysis of the fire net area along with the dispersion density, both the explosive mass and shape representing the physical characteristics should be considered for controlling the dispersion pattern of impactors in a near miss neutralizer.
Investigation of Impact Detection Characteristics of Piezoelectric Paint According to Boundary Conditions
Park, Seung-Bok ; Han, Dae-Hyun ; Kang, Lae-Hyong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 12, 2014, Pages 1335~1343
DOI : 10.3795/KSME-A.2014.38.12.1335
Piezoelectric paint can be used to monitor vibrations or impacts occurring in large engineering structures such as ships and airplanes. This study investigated the impact detection characteristics of a piezoelectric paint sensor and possible errors in detecting impacts according to boundary conditions. The piezoelectric paint sensor used in this study was coated on an aluminum plate with four different electrode areas. After the occurrence of the poling process, the output voltages from the paint sensors were obtained when impact occurred in a certain sensor region. The experimental results revealed a large difference in magnitudes between the sensor signal in the impact region and those in the other regions, and this relation was maintained regardless of the changes in the boundary conditions.
Prediction of Spring Rate and Initial Failure Load due to Material Properties of Composite Leaf Spring
Oh, Sung Ha ; Choi, Bok Lok ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 12, 2014, Pages 1345~1350
DOI : 10.3795/KSME-A.2014.38.12.1345
This paper presented analysis methods for adapting E-glass fiber/epoxy composite (GFRP) materials to an automotive leaf spring. It focused on the static behaviors of the leaf spring due to the material composition and its fiber orientation. The material properties of the GFRP composite were directly measured based on the ASTM standard test. A reverse implementation was performed to obtain the complete set of in-situ fiber and matrix properties from the ply test results. Next, the spring rates of the composite leaf spring were examined according to the variation of material parameters such as the fiber angles and resin contents of the composite material. Finally, progressive failure analysis was conducted to identify the initial failure load by means of an elastic stress analysis and specific damage criteria. As a result, it was found that damage first occurred along the edge of the leaf spring owing to the shear stresses.
Numerical and Experimental Analysis for Disc Brake Squeal Induced by Caliper Mode
Choi, Hoil ; Kang, Jaeyoung ; Gil, Hojong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 12, 2014, Pages 1351~1358
DOI : 10.3795/KSME-A.2014.38.12.1351
This study numerically simulates brake squeal and validates it experimentally by using a lab-scaled brake dynamometer. The system frequencies of the disc brake are traced with respect to the brake pressure by using a modal test and FEM. Then, the squeal frequencies measured from the brake dynamometer are found to correspond to the brake system mode with the dominant displacement of the caliper and pad. Furthermore, a complex eigenvalue analysis conducted using the finite element model confirms that the caliper mode generating the rotational displacement of the pad becomes unstable owing to the negative friction-velocity slope.
A Study on the 1-Way FSI Analysis for Shutter of Side Jet Thruster
Ko, Jun Bok ; Seo, Min Kyo ; Lee, Kyeong Ho ; Baek, Ki Bong ; Cho, Seung Hwan ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 12, 2014, Pages 1359~1365
DOI : 10.3795/KSME-A.2014.38.12.1359
In this study, 1-way fluid structure interaction analysis(FSI) for the shutter, component of side jet thruster was performed to evaluate the safety. Driving torque to open nozzle, thermal and high pressure load of hot gas was applied to shutter. Thus, the shutter must be designed to endure this load during combustion. We carried out computational fluid dynamics analysis to obtain the pressure, temperature, and heat transfer coefficient of hot gas of side jet thruster. We then used the data as the load condition for a thermal structural analysis using a mapping method. The locations with the maximum stress and temperature distributions were found. We compared the maximum stress with the tensile stress of shutter material according to temperature to evaluate the safety. We also analyzed the radial deformation of the shutter to set the proper interface gap with the side jet thruster parts.
The Study on Weldability of Boron Steel and Hot-Stamped Steel by Using Laser Heat Source (I) - Laser Weldability of Al-Si Coated Boron Steel Used for Hot Stamping Process -
Kim, Jong Do ; Choi, So Young ; Lee, Su Jin ; Suh, Jeong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 12, 2014, Pages 1367~1372
DOI : 10.3795/KSME-A.2014.38.12.1367
As the awareness of the environmental crisis has recently increased around the world, numerous studies in the transport industry have been conducted to solve this problem through lightweight car bodies. The hot-stamping process has been presented as solution to achieve a light weight. Hot-stamping is a method that is used to obtain ultra-high strength steel (1,500 MPa or greater) by simultaneously forming and cooling boron steel in a press die after heating it to a temperature of
or above. This study involved a, fundamental examination of laser parameters to investigate the laser weldability of boron steel. As a result, the following optimum parameters for the shielding gas were found: Q
The Study on Weldability of Boron Steel and Hot-Stamped Steel by Using Laser Heat Source (II) - Laser Weldability of Hot Stamping Steel with Ultra-High Strength -
Kim, Jong Do ; Choi, So Young ; Park, In Duck ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 12, 2014, Pages 1373~1377
DOI : 10.3795/KSME-A.2014.38.12.1373
Hot-stamping is a method of obtaining ultrahigh-strength steel by simultaneously forming and cooling boron steel in a press die after it has been heated at
or above. After heat treatment, boron steel has a strength of 1500 MPa or more. This material ensures a high level of quality because it overcomes the spring-back phenomenon, which is a problem associated with high-strength steel materials, and the degree of dimensional precision is improved by 90 or more because of the good formability compared with existing types of steel. In this study, the welding characteristics were identified through the butt and lap welding of hot-stamped steel using a disk laser. Full penetration was obtained at a faster speed with butt welding compared to lap welding, and a white band was observed in every specimen.
Life Prediction of Elastomeric U Seals in Hydraulic/Pneumatic Actuators Using NSWC Handbook
Shin, Jung Hun ; Chang, Mu Seong ; Kim, Sung Hyun ; Jung, Dong Soo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 12, 2014, Pages 1379~1385
DOI : 10.3795/KSME-A.2014.38.12.1379
Even the rough prediction of the product test time before the lifetime test of mechanical component begins would be of use in estimating cost and deciding how to keep up with the test. The reliability predictions of mechanical components are difficult because failure or degradation mechanisms are complicated, and few plausible databases are available for lifetime prediction. Therefore, this study conducted lifetime predictions of elastomeric U seals that were respectively installed in a hydraulic actuator and a pneumatic actuator using lifetime models and a field database based on failure physics and an actual test database obtained from the NSWC handbook. To validate the results, the predicted failure rates were compared with the actual lifetime test results acquired in the lab durability tests. Finally, this study discussed an engineering procedure to determine the coefficients in the failure rate models and analyzed the sensitivity of each influential parameter on the seal lifetime.
Material Stress Fringe Constant Measurement of Specimen under Pure Bending Load by Use of Photoelastic Phase Shifting Method
Liu, Guan Yong ; Kim, Myung Soo ; Baek, Tae Hyun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 12, 2014, Pages 1387~1394
DOI : 10.3795/KSME-A.2014.38.12.1387
In a photoelastic experiment, it is necessary to know the material stress fringe constant of the photoelastic specimen to determine the stresses from the measured isochromatic fringe orders. The material stress fringe constant can be obtained using a simple tension specimen and/or a circular disk under diametric compression. In these methods, there is generally a need to apply numerous loads to the specimen in response to the relationship of the fringe order. Then, the least squares method is used to obtain the material constant. In this paper, the fringe orders that appear on a four-point bending specimen are used to determine the fringe constant. This method requires four photoelastic fringes obtained from a circular polariscope by rotating the analyzer to 0,
radians. Using the four-point bending specimen to determine the material stress fringe constant has an advantage because measurements can be made at different locations by applying a constant load. The stress fringe constant measured with this method is within the range suggested by the manufacturer of the photoelastic material.
Performance Evaluation of Inertial Balance for Measuring Mass in Microgravity
Jang, Hyun-Jin ; Lee, Joo-Hee ; Choi, Jae-Hyuk ; Park, Seul-Hyun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 12, 2014, Pages 1395~1401
DOI : 10.3795/KSME-A.2014.38.12.1395
In an effort to develop and implement an inertial balance with high performance, the response characteristics of a load cell, which are some of the critical parameters for optimal system design, were evaluated using a sample object of approximately 100 g under microgravity conditions. To this end, a 15-m drop-tower was used to produce microgravity conditions, and the response characteristics of the load cell were investigated in terms of the variations in the magnitude of the deceleration of the sample object, noting that the mass of a living animal should be determined in microgravity. An analysis of the ratio of the inertial forces clearly demonstrated that the average velocity of a load cell plate should be higher than 0.5 m/s to meet the design requirements.
Basic Study on Performance Comparison of Structural Optimization Software Systems
Choi, Wook Han ; Huang, Cheng Guo ; Park, Gyung-Jin ; Kim, Tai-Kyung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 12, 2014, Pages 1403~1413
DOI : 10.3795/KSME-A.2014.38.12.1403
Structural optimization is widely accepted in industrial fields. Structural optimization pursues improved performance of the structures. Recently, structural optimization is actively utilized due to the well-developed commercial design software systems. Three popular commercial structural optimization systems are investigated and compared. They are MSC.Nastran, Genesis and OptiStruct. The performance of the systems is analyzed based on the quality of the optimum solution and the computational time. Linear static response size, shape and topology optimizations are explored and compared with some test examples. For fair comparison, the systems are run in the same environment and the optimization parameters affecting the performance are unified. The optimization results are analyzed and the performances and characteristics of each software system are discussed.
Evaluation of Tensile Property of Austenitic Alloys Exposed to High-Temperature S-CO
Kim, Hyunmyung ; Lee, Ho Jung ; Jang, Changheui ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 12, 2014, Pages 1415~1420
DOI : 10.3795/KSME-A.2014.38.12.1415
) Brayton cycle has been considered to replace the current steam Rankine cycle in Sodium-cooled Fast Reactor (SFR) in order to improve the inherent safety and thermal efficiency. Several austenitic alloys are considered as the structural materials for high temperature
environment.. Microstructural change after long-term exposure to high temperature
environment could affect to the mechanical properties. In this study, candidate materials (austenitic stainless steels and Alloy 800HT) were exposed to
to assess oxidation resistance and the change in tensile properties. Loss of ductility was observed for some austenitic stainless steels even after 250 h exposure. The contribution of
environment on such changes was analyzed based on the characterization of the surface oxide and carburization of the materials in which 316H and 800H showed different oxidation behaviors.
Evaluation of High-Temperature Tensile Property of Diffusion Bond of Austenitic Alloys for S-CO
Cycle Heat Exchangers
Hong, Sunghoon ; Sah, Injin ; Jang, Changheui ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 12, 2014, Pages 1421~1426
DOI : 10.3795/KSME-A.2014.38.12.1421
To improve the inherent safety of the sodium-cooled fast reactor (SFR), the supercritical
) Brayton cycle is being considered as an alternative power conversion system to steam the Rankine cycle. In the
system, a PCHE (printed circuit heat exchanger) is being considered. In this type of heat exchangers, diffusion bonding is used for joining the thin plates. In this study, the diffusion bonding characteristics of various austenitic alloys were evaluated. The tensile properties were measured at temperatures starting from the room temperature up to
. For the 316H and 347H types of stainless steel, the tensile ductility was well maintained up to
. However, the Incoloy 800HT showed lower strength and ductility at all temperatures. The microstructure near the bond line was examined to understand the reason for the loss of ductility at high temperatures.
Evaluation of the Mechanical Characteristics According to the Curvature of Thermal Barrier Coating
Lee, Jeng-Min ; Seok, Chang-Sung ; Koo, Jae-Mean ; Kim, Sung Hyuk ; Zhen, Guo ; Tao, Shen ; Moon, Wonki ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 12, 2014, Pages 1427~1430
DOI : 10.3795/KSME-A.2014.38.12.1427
A thermal barrier coating (TBC) prevents heat directly transferring from a high-temperature flame to a substrate. The TBC system comprises a top coating and bond coating. TBC technology reduces the substrate surface temperature by about
. In the TBC system, internal stress is generated by the difference in thermal expansion coefficients of the substrate and coating. The internal stress also differs according to the shape and position of the blade. In this study, finite element analysis was performed for different curvatures of coin-shaped specimens, which are commonly used for thermal fatigue tests, and the changes in internal stress of the TBC system were compared. Based on the results, the curvature at which the minimum stress occurs was derived, and the thermal stress was confirmed to increase with the difference between a given curvature and the curvature with the minimum stress.
Durability Evaluation of Thermal Barrier Coating (TBC) According to Growth of Thermally Grown Oxide (TGO)
Song, Hyun Woo ; Moon, Byung Woo ; Choi, Jae Gu ; Choi, Won Suk ; Song, Dongju ; Koo, Jae-Mean ; Seok, Chang-Sung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 12, 2014, Pages 1431~1434
DOI : 10.3795/KSME-A.2014.38.12.1431
The thermal barrier coating (TBC) applied to a gas turbine can be damaged by repeated thermal fatigue during operation, so an evaluation of its durability is needed. Thermally grown oxide (TGO) is generated inside the TBC in a high-temperature environment. The growth of TGO is known to be the main cause of damage to the TBC. Therefore, the durability of TBC should be evaluated according to the growth of TGO. In this research, Kim et al.`s work on the growth of TGO with aging was used as a basis for finite element analysis. The relationship between stress and aging was derived from the finite element analysis results. The durability of the TBC with aging was evaluated through a comparison between the results of the finite element analysis and a bond strength test.
Compressive Fracture Behavior of ATJ Graphite for Rocket Nozzle
Choi, Hoon Seok ; Seo, Bo Hwi ; Kim, Jae Hoon ; Moon, Soon Il ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 12, 2014, Pages 1435~1440
DOI : 10.3795/KSME-A.2014.38.12.1435
The effects of the specimen size and temperature on the compressive strength of ATJ graphite were investigated. Compressive tests were conducted in accordance with ASTM C 965 at room temperature,
. Three types of cylindrical specimen at room temperature were used in uniaxial tests, where the diameter-to - length ratios were one to two for the ASTM standard specimen, one to one for the Type I specimen, and one to 0.5 for the Type II specimen. Two kinds of cylindrical specimens, with and without antioxidant coating, were tested at elevated temperature. The Compressive strength of the expanded specimens(Type I, II) were slightly higher than that of standard specimen at room temperature. The compressive strength of a specimen with antioxidant coating increased as the temperature increased to
. In contrast, that of the non-coated specimen decreases sharply due to the oxidation of the specimen.
Investigation into Crack-Tip Constraint of Curved Wide-Plate using Q-Stress
Lee, Hwee-Sueng ; Huh, Nam-Su ; Kim, Ki-Seok ; Shim, Sang-Hoon ; Cho, Woo-Yeon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 38, issue 12, 2014, Pages 1441~1446
DOI : 10.3795/KSME-A.2014.38.12.1441
In the present paper, the effects of the thickness and width of a curved wide-plate, the crack length, and the strain hardening exponent on the crack-tip constraint of the curved wide-plate were investigated. To accomplish this, detailed three-dimensional elastic-plastic finite element (FE) analyses were performed considering various geometric and material variables. The material was characterized by the Ramberg-Osgood relationship, and the Q-stress was employed as a crack-tip constraint parameter. Based on the present FE results, the variations in the Q-stress of the curved wide-plate with the geometric variables and material properties were evaluated. This revealed that the effect of out-of-plane constraint conditions on the crack-tip constraint was closely related to the in-plane constraint conditions, and out-of-plane constraint conditions affected the crack-tip constraint more than in-plane constraint conditions.