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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
Journal Basic Information
Journal DOI :
The Korean Society of Mechanical Engineers
Editor in Chief :
Volume & Issues
Volume 23, Issue 11 - Nov 1999
Volume 23, Issue 7 - Jul 1999
Volume 23, Issue 6 - Jun 1999
Volume 23, Issue 11 - 00 1999
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Chaoticity Evaluation of Ultrasonic Signals in Welding Defects by 6dB Drop Method
Yi, Won ; Yun, In-Sik ;
Transactions of the Korean Society of Mechanical Engineers A, volume 23, issue 7, 1999, Pages 1065~1074
DOI : 10.22634/KSME-A.19220.127.116.115
This study proposes the analysis and evaluation method of time series ultrasonic signal using the chaotic feature extraction for ultrasonic pattern recognition. Features extracted from time series data using the chaotic time series signal analysis quantitatively welding defects. For this purpose analysis objective in this study is fractal dimension and Lyapunov exponent. Trajectory changes in the strange attractor indicated that even same type of defects carried substantial difference in chaoticity resulting from distance shills such as 0.5 and 1.0 skip distance. Such differences in chaoticity enables the evaluation of unique features of defects in the weld zone. In experiment fractal(correlation) dimension and Lyapunov exponent extracted from 6dB ultrasonic defect signals of weld zone showed chaoticity. In quantitative chaotic feature extraction, feature values(mean values) of 4.2690 and 0.0907 in the case of porosity and 4.2432 and 0.0888 in the case of incomplete penetration were proposed on the basis of fractal dimension and Lyapunov exponent. Proposed chaotic feature extraction in this study enhances ultrasonic pattern recognition results from defect signals of weld zone such as vertical hole.
Three-Dimensional Flow Analysis for Compression Molding of Unidirectional Fiber-Reinforced Polymeric Composites with Slip Between Mold and Material
Yoon, Doo-Hyun ; Jo, Seon-Hyung ; Kim, E-Gon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 23, issue 7, 1999, Pages 1075~1084
DOI : 10.22634/KSME-A.1918.104.22.1685
The family of unidirectional continuous fiber reinforced polymeric composites are currently used in automotive bumper beams and load floors. The material properties and mechanical characteristics of the compression molded parts are determined by the curing behavior, fiber orientation and formation of knit lines, which are in turn determined by the mold filling parameters. In this paper, a new model is presented which can be used to predict the 3-dimensional flow under consideration of the slip of mold-composites and anisotropic viscosity of composites during compression molding of unidirectional fiber reinforced thermoplastics for isothermal state. The composites is treated as an incompressible Newtonian fluid. The effects of longitudinal/transverse viscosity ratio A and slip parameter
on the buldging phenomenon and mold filling patterns are also discussed.
Thickness Effects of Coupling Agent on Residual Bending Stress in
Kong, Do-Il ; Park, Chan-Eon ; Hong, Seung-Taek ; Yang, Hoon-Chul ; Kim, Ki-Tae ;
Transactions of the Korean Society of Mechanical Engineers A, volume 23, issue 7, 1999, Pages 1085~1093
DOI : 10.22634/KSME-A.1922.214.171.1245
Thickness effects of coupling agent on residual bending stress were investigated in
joints during thermal cycling. Thickness and peel strength of
-APS coupling agent were measured and correlated with solution concentration and residual bending stress. The variation of residual bending stress with temperature was also measured for various thicknesses of the coupling agent. Finite element results were compared with experimental data for residual bending stress in
Experimental Evaluation on the Thermal Stress Due to Ice Plugging of Tubes in Nuclear Power Plant
Park, Young-Don ; Lee, Min-Woo ; Ku, Tae-Wan ; Kim, Kui-Soon ; Kang, Beom-Soo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 23, issue 7, 1999, Pages 1094~1103
DOI : 10.22634/KSME-A.19126.96.36.1994
Ice-plugging of tube in nuclear power plant has been widely used for the purpose of preventing flow of the tube temporarily like a valve. Most common plugging method employs Liquid Nitrogen Gas of
. According to the change of tube materials and its dimension, the thermal stress caused from the application of the frozen gas can be varied. In this research, a series of experiments have been carried out to inspect the effect of tube geometry on thermal stresses induced due to ice-plugging. Two typical dimension of stainless and mild steels of 3 and 6 inch diameters were used for the experiments. Each critical spots were checked using strain rosette gages. Another inspection was made on the pressure and temperature of the fluid. It is shown that significant thermal stress level which can cause plastic deformation of failure has not been noticed in this series of experiments.
Development of Composite Brake Pedal for KTX-1 and Tests for Structural Certification
Joe, Chee-Ryong ; Kim, Hyun-Su ; Kim, Kwang-Su ;
Transactions of the Korean Society of Mechanical Engineers A, volume 23, issue 7, 1999, Pages 1104~1111
DOI : 10.22634/KSME-A.19188.8.131.524
A brake pedal for the flight control system of the Korean primary trainer is developed using composite material. The development includes the structural design, stress analysis, manufacturing and the qualification tests. A FEM analysis is used for the structural design and stress analysis. Autoclaving process is used to fabricate the composite brake pedal. For the qualification tests, modular fixtures are developed and applied. It is shown that the composite brake pedal developed meets all the structural integrity requirements specified in the military specification for aircraft parts.
Effect of Reverse Cyclic Loading on the Fracture Resistance Curve of Nuclear Piping Material
Weon, Jong-Il ; Seok, Chang-Sung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 23, issue 7, 1999, Pages 1112~1119
DOI : 10.22634/KSME-A.19184.108.40.2062
Fracture resistance(J-R) curves, which are used for the elastic-plastic fracture mechanics analyses, are known to be dependent on the cyclic loading history. The objective of this paper is to study the effect of reverse cyclic loading on J-R curves in CT specimens. The effect of two parameters was observed on the J-R curves during the reverse cyclic loading. One was the minimum-to-maximum load ratio(R) and the other was the incremental plastic displacement(
), which is related to the amount of crack growth that occurs in a cycle. Fracture resistance test on CT specimens with varying load ratio and incremental plastic displacement were performed. For the SA 516 Gr. 70 steel, the results showed that the J-R curves were decreased with decreasing the load ratio and the incremental plastic displacement. When the load ratio was set to -1, the results of the J-R curves and the
value were about
percent of those for the monotonic loading condition. Also on condition that the incremental plastic displacement reached 1/40, the J-R curves and the
value were about
percent of those for the incremental plastic displacement of 1/10.
Finite Element Analysis of Creep Crack Growth Behavior Including Primary Creep Rate
Choi, Hyeon-Chang ;
Transactions of the Korean Society of Mechanical Engineers A, volume 23, issue 7, 1999, Pages 1120~1128
DOI : 10.22634/KSME-A.19220.127.116.110
An elastic-viscoplastic finite element analysis is performed to investigate detailed growth behavior of creep cracks and the numerical results are compared with experimental results. In Cr-Mo steel stress fields obtained from the crack growth method by mesh translation were compared with both cases that the secondary creep rate is only used as creep material property and the primary creep rate is included. Analytical stress fields, Riedel-Rice(RR) field, Hart-Hui-Riedel(HR) field and Prime(named in here) field, and the results obtained by numerical method were evaluated in details. Time vs. stress at crack tip was showed and crack tip stress fields were plotted. These results were compared with analytical stress fields. There is no difference of stress distribution at remote region between the case of 1st creep rate+2nd creep rate and the case of 2nd creep rate only. In case of slow velocity of crack growth, the effect of 1st creep rate is larger than the one of fast crack growth rate. Stress fields at crack tip region we, in order, Prime field, HR field and RR field from crack tip.
Two-Wavelength Phase-Shifting Projection
Topography for Measurement of Three-Dimensional Profiles with High Step Discontinuities
Kim, Seung-Woo ; Oh, Jung-Taek ; Jung, Moon-Sik ; Choi, Yi-Bae ;
Transactions of the Korean Society of Mechanical Engineers A, volume 23, issue 7, 1999, Pages 1129~1138
DOI : 10.22634/KSME-A.1918.104.22.1689
] technique is now being extensively investigated as a fast non-contact means of three-dimensional profile measurement especially for reverse engineering. One problem with
technique is so called
-ambiguity problem that limits the maximum step height difference between two neighboring sampling points to be less than half the equivalent wavelength of
fringes. In this investigation, a new two-wavelength scheme of projection
topography is proposed and tested to cope with the
-ambiguity problem. Experimental results are discussed to assess the new method in measuring large objects with high step discontinuities.
An Analysis of Crack Growth Rate Due to Variation of Fatigue Crack Growth Resistance
Kim, Seon-Jin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 23, issue 7, 1999, Pages 1139~1146
DOI : 10.22634/KSME-A.1922.214.171.1249
Reliability analysis of structures based on fracture mechanics requires knowledge on statistical characteristics of the parameter C and m in the fatigue crack growth law,
. The purpose of the present study is to investigate if it is possible to predict fatigue crack growth rate by only the fluctuation of the parameter C. In this study, Paris-Erdogan law is adopted, where the author treat the parameter C as random and m as constant. The fluctuation of crack growth rate is assumed only due to the parameter C. The growth resistance coefficient of material to fatigue crack growth (Z=1/C) was treated as a spatial stochastic process, which varies randomly on the crack path. The theoretical crack growth rates at various stress intensity factor range are discussed. Constant
fatigue crack growth tests were performed on the structural steel, SM45C. The experimental data were analyzed to determine the autocorrelation function and Weibull distributions of the fatigue crack growth resistance. And also, the effect of the parameter m of Paris' law due to variation of fatigue crack growth resistance was discussed.
Evaluation of Fracture Resistance Characteristics of SA 508 CL.1a Carbon Steel for Piping System
Seok, Chang-Sung ; Kang, Byoung-Gu ;
Transactions of the Korean Society of Mechanical Engineers A, volume 23, issue 7, 1999, Pages 1147~1154
DOI : 10.22634/KSME-A.19126.96.36.1997
The objective of this paper is to evaluate the fracture resistance characteristics of SA508 CL.1a carbon steel, and their associated welds manufactured for primary coolant piping system of nuclear power plants. The effect of various parameters such as pipe size, welding method and chemical composition on the material properties were discussed. Test results showed that the offset of pipe size on tincture toughness was negligible, while the effect of welding method on fracture toughness was significant. In addition, Fracture toughness for carbon steel was influenced by silicon contents due to the different steel refining processes.
Human Vibration Measurement for Passenger Car and Seat Characteristics Optimization
Cho, Young-Gun ; Yoon, Yong-San ;
Transactions of the Korean Society of Mechanical Engineers A, volume 23, issue 7, 1999, Pages 1155~1163
DOI : 10.22634/KSME-A.19188.8.131.525
This study deals with the vibration ride quality for passenger car when running on straight highway at the speed of 70km/h. Ten accelerations were measured at four positions, three axes each at the feet, hip, and head, and one axis at the back. Five seats that have different static sponge stiffness were used, and two subjects were participated. These accelerations were analyzed to produce the ride values such as component ride value and overall ride value. It was hard to see the difference of ride value by the change of sponge stiffness. However we could rank the ride quality by the total vibration exposed to passengers. From the transfer function between the hip and the foot, the fundamental mode was observed to be around 5.8Hz. Also the transfer function between the head and hip was studied. The optimal damping ratio of the seat was calculated according to the seat natural frequency with human weighting filter which makes the optimal damping ratio different from that without weighting filter.
A Stochastic Analysis for Crack Growth Retardation Behavior and Prediction of Retardation Cycle Under Single Overload
Shim, Dong-Suk ; Kim, Jung-Kyu ;
Transactions of the Korean Society of Mechanical Engineers A, volume 23, issue 7, 1999, Pages 1164~1172
DOI : 10.22634/KSME-A.19184.108.40.2064
In this study, to investigate the fatigue crack retardation behavior and the variability of retardation cycles, fatigue crack growth tests were conducted on 7075-T6 aluminum alloy under single tensile overload. A retardation coefficient, D was introduced to describe fatigue crack retardation behavior and a random variable, Z to describe the variability of fatigue crack growth. The retardation coefficient was separately formulated according to retardation behavior which is composed of delayed retardation part and retardation part. The random variable, Z was evaluated from experimental data which was obtained from fatigue crack growth tests under constant amplitude load. Using these variables, a probabilistic model was developed on the basis of the modified Forman's equation, and retardation behavior and cycles were predicted under certain overload condition. The predicted retardation curve well agrees with the trend of experimental crack retardation behavior. And this model well predicts the scatter of experimental retardation cycles.
Tri-axial Stress Analysis of Composite Materials for X-ray Stress Measurement
Boo, Myung-Hwan ; Park, Young-Chul ; Hirose, Yukio ;
Transactions of the Korean Society of Mechanical Engineers A, volume 23, issue 7, 1999, Pages 1173~1181
DOI : 10.22634/KSME-A.19220.127.116.113
In X-ray stress measurements for uni-directionally deformed surfaces such as grinding, a strongly curved
diagram, so called
-splitter, has been observed recently. It has been known that this is caused by the residual shear stress induced in the deformed layer by external forces. In this case it is necessary to consider this enough for ceramics and composite materials with tri-axial stress analysis. However, sufficient studies have not been done about the tri-axial stress analysis of the macro stress and micro. stress on each phase of the composite materials. The result of obtaining is as follows. 1.
-splitter does not appear in the vertical direction though
-splitter appears in grinding direction in WC-Co cemented carbides. The reversal of
-splitter to each phase does not appear. 2.
-splitter caused in WC-Co cemented carbides has a close relation in dislocation which accumulates in WC phase and phase transformation caused in Co phase. 3. The residual stress on the surface of grinding of each phase is in the state of the compression stress.
An Experimental Study on the Fracture Behavior of Nuclear Piping System with a Circumferential Crack(I) - Estimation of Crack Behavior in Straight Piping -
Choi, Young-Hwan ; Park, Youn-Won ; Wilkowski, Gery ;
Transactions of the Korean Society of Mechanical Engineers A, volume 23, issue 7, 1999, Pages 1182~1195
DOI : 10.22634/KSME-A.1918.104.22.1682
The purpose of this study is to investigate experimentally the effects of both seismic loading and crack length on the fracture behavior of piping system with a circumferential crack in nuclear power plants. The experiments were performed using both large scale piping system facility and 4 points bending test machine under PWR operating conditions. The difference in the load carrying capacities between cracked piping and non-cracked piping was also investigated using the results from experiments and numerical calculations. The results obtained from the experiments and estimation are as follows : (1) The safety margin under seismic loading is larger than those under quasi static loading or simple cyclic loading. (2) There was no significant effect of crack length on tincture behavior of piping system with both a surface crack and a through-wall crack. (3) The load carrying capacity in cracked piping was reduced by factors of 7 to 46 compared to non-cracked piping.
Dynamic Edger Control for the Precise Width Control at the Head, and Tail Ends of Hot Strip
Chun, Myung-Sik ; Yi, Joon-Jeong ; Moon, Young-Hoon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 23, issue 7, 1999, Pages 1196~1204
DOI : 10.22634/KSME-A.1922.214.171.1246
adaption of the model predictions is highly desirable. In general, the width deviation at the head and tail ends of strip may be different from that of the steady state region. Therefore, the dynamic edger corrections can be used to compensate the width deviations which would otherwise occur. For the precise width control, the effect of edger roll gap and rolling conditions on the width deviation of head and tail ends of strip has been investigated and the effective method to decrease width deviation has been proposed. On-line application of dynamic edger control method in this study shows about 50% width compensation at the head end of the strip, and near perfect compensation at the tail end of strip.
Development of a Quadrilateral Enhanced Assumed Strain Element for Efficient and Accurate Thermal Stress Analysis
Ko, Jin-Hwan ; Lee, Byung-Chai ;
Transactions of the Korean Society of Mechanical Engineers A, volume 23, issue 7, 1999, Pages 1205~1214
DOI : 10.22634/KSME-A.19126.96.36.1995
A new quadrilateral plane stress element is developed for efficient and accurate analysis of thermal stress problems. It is convenient to use the same mesh and the same shape functions for thermal analysis and stress analysis. But, because of the inconsistency between deformation related strain field and thermal strain field, oscillatory responses and considerable errors in stresses are resulted in. To avoid undesired oscillations, strain approximation is enhanced by supplementing several assumed strain terms based on the variational principle. Thermal deformation is incorporated into the generalized mixed variational principle for displacement, strain and stress fields, and basic equations for the modified enhanced assumed strain method are derived. For the stress approximation of bilinear elements, the
version of Pian and Sumihara is adopted. The numerical results for several problems show that the present element behaves well and reduces oscillatory responses. it also results in almost the same magnitude of error as compared with the quadratic element.
Prediction of Fracture Appearance Transition Temperature(FATT) to Steel by Ultrasonic and Barkhausen Noise Method
Nam, Young-Hyun ; Seong, Un-Hak ;
Transactions of the Korean Society of Mechanical Engineers A, volume 23, issue 7, 1999, Pages 1215~1222
DOI : 10.22634/KSME-A.19188.8.131.525
It is advantageous to use an NDE method to assess the mechanical properties of materials since the conventional method is time-consuming and sometimes requires cutting of sample from the material/component. This paper shows that the ultrasonic and the Barkhausen noise(BHN) methods can be used to accurately characterize forged reactor vessels. The attenuation coefficient of the ultrasonic wave was changed with heat treatment temperature and condition[as-quenched, tempered, PWHT]. The RMS[root mean square] voltage of Barkhausen noise depended on heat treatment temperature and conditions. The fracture appearance transition temperature(FATT) can be predicted using nondestructive evaluation methods.
A Study on the Global Optimization Technique Based upon Molecular Dynamics
Choi, Deok-Kee ; Kim, Jae-Yoon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 23, issue 7, 1999, Pages 1223~1230
DOI : 10.22634/KSME-A.19184.108.40.2063
This paper addresses a novel optimization technique based on molecular dynamics simulation which has been utilized for physical model simulation at various disciplines. In this study, objective functions are considered to be potential functions, which depict molecular interactions. Comparisons of typical optimization method such as the steepest descent and the present method for several test functions are made. The present method shows applicability and stability in finding a global optimum.
Tooth Durability Evaluation of n Cylindrical Worm Gear by Contact Line Analysis
Cheon, Gill-Jeong ; Han, Dong-Chul ;
Transactions of the Korean Society of Mechanical Engineers A, volume 23, issue 7, 1999, Pages 1231~1237
DOI : 10.22634/KSME-A.19220.127.116.111
Applying the conjugate contact condition, contact lines of a cylindrical worm gear has been calculated. The characteristics of tooth contact were analyzed and the pitting resistance were also assessed. It has been verified that: i) the length of contact is shortest on the 1st tooth of the front region, ii) the contact region is more narrow in the recess side than in the access side, iii) the contact region is more narrow in worm than in worm wheel. Hence, the pitting resistance is weakest in the recess side of the 1st contacting worm tooth.
Measurement of Static Tooth Fillet Strain and Transmission Error of a Cylindrical Worm Gear
Lee, Dong-Hwan ; Cheon, Gill-Jeong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 23, issue 7, 1999, Pages 1238~1244
DOI : 10.22634/KSME-A.1918.104.22.1688
Using a cylindrical worm gear under the actual condition of static loading, tooth fillet strains and transmission errors have been measured. The maximum strain occurs on the filet region of the center of the 1st mating tooth. Tooth fillet strain changes most sensitively according to the variations of the center distance and recess side eccentricity than the access side eccentricity. Even the no-backlash worm gear shows the transmission errors.
Sliding Wear Behavior of
Chae, Young-Hun ; Park, Byung-Hee ; Kim, Seock-Sam ;
Transactions of the Korean Society of Mechanical Engineers A, volume 23, issue 7, 1999, Pages 1245~1252
DOI : 10.22634/KSME-A.1922.214.171.1245
The sliding wear behavior of
coating deposited on steel(SM45C) was investigated under lubrication. The parameters of sliding wear are normal loads, coating thickness. As a result, the wear resistance of
coating was remarkably greater than that of
coating. The optimized coating thickness was found to be
to ensure good anti-wear. The bond coating played important role in decreasing residual stress. The residual stress had much influence on wear mechanism. These results were correlated with the stress state of coating and the microstructure of coating.