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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 20, Issue 12 - Dec 1996
Volume 20, Issue 11 - Nov 1996
Volume 20, Issue 10 - Oct 1996
Volume 20, Issue 9 - Sep 1996
Volume 20, Issue 8 - Aug 1996
Volume 20, Issue 7 - Jul 1996
Volume 20, Issue 6 - Jun 1996
Volume 20, Issue 5 - May 1996
Volume 20, Issue 4 - Apr 1996
Volume 20, Issue 3 - Mar 1996
Volume 20, Issue 2 - Feb 1996
Volume 20, Issue 1 - Jan 1996
Selecting the target year
A Robust Disturbance Observer for Uncertain Linear Systmes
Kim, Jun-Sik ; O, Jun-Ho ;
Transactions of the Korean Society of Mechanical Engineers A, volume 20, issue 9, 1996, Pages 2731~2743
DOI : 10.22634/KSME-A.1918.104.22.16831
When modeling error is large of plant is time-varying, it is hard to obtain good robust performance and robust stability by conventional contorl methods. Here, we need to design a robust controller bearing modeling error. In this paper, based on recently developed Time Delay Control(TDC) and Disturbance Observer the output feedback Robust Disturbance Observer(RDO), which is easily combined with general linear control, is proposed. Proposed RDO is derived from extending the main idea of Disturbance Observer to multi-input multi-output linear system. RDO solves robust stability problem of Disturbance Observer and has the robust performance same as nominal performance. RDO controlled dual stage positioning system shows excellent robust performance.
Dynamic Behavior of Rotating Shaft System Corresponding to Operating Modes
Kim, Sang-Hwan ;
Transactions of the Korean Society of Mechanical Engineers A, volume 20, issue 9, 1996, Pages 2744~2751
DOI : 10.22634/KSME-A.1922.214.171.12444
In case of limited power supply, a rotating shaft system may not reach its operating speed that is greater than its critical speed, but the speed oscillates with small ampllitude near critical speed. As a result, it is considered that the operating mode plays an important role in the smooth start of machines. In order to investigate the dynamic behaviors of the rotating shaft system at the beginning stage, one has derived the equations of motion whose degrees of freedom is three, two translations and one rotation. The simultaneous differential equations are numerically solved by using runge-Kutta method, and thus the small time step length could be required corresponding to the stability of solution. Three types of operating modes dependent upon the driving torque rate have been numerically investigated according to the maximum displacement of shaft center. The first type of relation is linear, the second type is composed of two linear curves recommended by machine manufacturer, and the last one is the proposed torque curve reflecting the frequency response curve of one degree of freedom system. For the second type of modes, it is found that the optimal range of intermediate speed to the critical speed lies between 0.8 and 0.9. In addition to that, the maximum displacement can be reduced more if the third type of mode is utilized.
A Study of Weld Pool width Control in Gas Tungsten Arc Welding Using the Digital Image Processing
Kim, Dong-Cheol ; Rhee, Sehun ; Um, Ki-Woan ;
Transactions of the Korean Society of Mechanical Engineers A, volume 20, issue 9, 1996, Pages 2760~2769
DOI : 10.22634/KSME-A.19126.96.36.19960
The feedback control systems of welding process using visual information can improve weld qualities. However, it is very difficult to get the visual information of weld pool since the light intensity of welding arc is much stronger than that of the weld pool. To explore the possibility of extending the capability of automatic welding machines, a study of a closed loop controlled welding system consisted of a GTA welding machine, a vision system, a stepping motor system and a digital computer was undertaken. Particularly, in this system, a CCD camera with a long wavelength pass filter was used to get a better weld pool image. Subsequently, an image analysis technique has been developed to measure the weld pool width. Using this weld pool width measurement, a colsed loop control system adjusted welding speed to maintain a constant weld pool width.
Effective Longitudinal Shear Modulus of Continuous Fiber-Reinforced 2-Phase Composites
Lee, Dong-Ju ; Jeong, Tae-Hyeon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 20, issue 9, 1996, Pages 2770~2781
DOI : 10.22634/KSME-A.19188.8.131.5270
Longitudinal shear modulus of continuous fiber reinforced 2-phase composites is predicted by theoretical and numerical analysis methods. In this paper, circular, hexagonal and rectangular shapes of reinforced fiber are considered using unit cell concept. And fiber array is regular rectangular and hexagonal fiber arrangement. Longitudinal shear modulus is a function of fiber distribution pattern and fiber volume change. It is found that the rectangular array has a higher longitudinal shear modulus than the hexagonal one. Also, the rectangular fiber shape in lower fiber volume fraction and the circular fiber shape in higher fiber volume fraction show the higher longitudinal shear modulus. And it has been found that the theoretical and numerical predictions of the longitudinal shear modulus give a good agreement with the experimental data at lower fiber volume fraction. Both the distance and stress transfer between the fibers are discussed as the major determing factors.
Effective Longitudinal Shear Modulus of Continuous Fiber-Reinforced 3-Phase Composites
Jeong, Tae-Heon ; Lee, Dong-Joo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 20, issue 9, 1996, Pages 2782~2791
DOI : 10.22634/KSME-A.19184.108.40.20682
The effective longitudinal shear modulus(LSM) of continuous composites is studied theoretically and numerically using 3-phase unit cell model. Circular, hexagonal and rectangular shapes of reinforced fiber are considered to predict the shear modulus as a function of elastic modulus of each phase and volume fraction of interphase and reinforced fiber. It is found that rectangular fiber shape in low fiber volume fraction(
<30%) and circular fiber shape in high volume fraction(
>40%) shows the higher longitudinal shear modulus. Also the obtained values of LSM for rectangular array and by numerical analysis are higher than those of hexagonal array and by theoretical analysis respectively. The reinforcing effects of interphase are more significant in cases of higher fiber volume fraction and circular fiber shape. Not only the spatial distribution and shape of reinforcing fiber but also the volume of interphase have a pronounced effects on the overall LSM. It is also found that the tangent moduous of 2-and 3-phase polymer matrix composites is insensitive to the shape and distribution of reinforcing fibers.
Elastic Work Factor of CLS Specimen and Determination of
for Graphite/Peek Composites by Using the Elastic Work Factor
Lee, Gyeong-Yeop ;
Transactions of the Korean Society of Mechanical Engineers A, volume 20, issue 9, 1996, Pages 2792~2799
DOI : 10.22634/KSME-A.19220.127.116.1192
It was shown in the previous study that the numerically derived elastic work factor for CLS specimen was independent of fiber direction for a unidirectional case. Also, it was proposed the elastic work factor could be used to determine energy release rate from a single test record. In the present study, elastic work factor was derived from a simple beam theory to investigate its dependence on material property and geometric condition. Also, the elastic work factor of CLS specimen was applied experimentally to determine critical energy release rate in order to prove its validity determining critical energy release rate from a single specimen. For this purpose, critical energy release rate determined using the elastic work factor was compared with that determined by the compliance method. The results showed that while elastic work factor is affected by
it is independent of fiber angle for a unidirectional case. It was also found that critical energy release rates determined by both methods are comparable each other, thus elastic work factor approach can be used to determine energy release rate from a single test specimen.
Free Vibration Analysis of a Stepped Cantilever Beam with a Mass and a Spring at the End
Yu, Chun-Seung ; Hong, Dong-Pyo ; Chung, Tae-Jin ; Chung, Kil-To ;
Transactions of the Korean Society of Mechanical Engineers A, volume 20, issue 9, 1996, Pages 2812~2818
DOI : 10.22634/KSME-A.1918.104.22.16812
A cantilever beam with a mass and a spring at the end can be use to model a miniature flexible arm. It is necessary to know the natural frequencies and mode shapes to discuss its free vibration, especially when modal analysis is employed. A beam is clamped-free. In this paper we look at the lateral vibration of beams that have step changes in the properties of their cross sections. The frequency equation is derived by Bernoulli-Euler formulation and is sloved by the separation of variable. The parameters of the beam, 'mass and spring stiffness' are defined as nondimensionalized parameters for wide application of the results. According to the change of eigenvalues and mode shape are presented for this beam. The results presented are the eigenvalues and the natural frequencies for the first three modes of vibration. Results show that the parameters have a significant effect on the natural frequency.
Rotated Bending Fatigue Strength in Aged 1Cr-1Mo-0.25V Steel at Elevated Temperature
Suh, Chang-Min ; Huh, Jeong-Hoon ; Namh, Seung-Hoon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 20, issue 9, 1996, Pages 2819~2832
DOI : 10.22634/KSME-A.1922.214.171.12419
The estimation of the remaining life for the aged components in power plant as well as chemical and petroleum plants has been recently concerned. The raw materials used in this study are the 1Cr-1Mo-0.25V steel which intensified P and S compositions along with the nominal compositions of ASTM A 470 standard. Five kinds of specimens with the different degradation levels were prepared by isothermal aging heat treatment at 630.deg.C. The mechanical properties and rotated bending fatigue strength of virgin and aged 1Cr-1Mo-0.25V steel have been investigated through the hardness, tensile, fatigue test, SEM fractograph and EDS analysis at 538.deg.C and room temperature, respectively. Thus the data of aged specimens were compared with those of virgin specimen to evaluate the aging effects. The main results obtained in this study are as follows ; The decrease of the yield and tensile strength due to degradation was distinguished until 50, 000hrs simulated service time. And it was confirmed that the considerable amount of P, Mn, Cr and S was precipitated at the grain boundary of aged material through the SEM and EDS analysis. The rotated bendingd fatigue strength at 538.deg.C of virgin, 25, 000, 50, 000, 75, 000 and 100, 000 hrs aged material was decreased 44.6 %, 49.6 %, 51.5 %, 52.4% and 53.8% than that of virgin material at 10
cycles of room temperature, respectively. The major cracks of virgin and aged materials mainly initiated at the inclusions including Si, P and Mn compositions which were located at the outer periphery of the specimen.n.
Sensitivity Analysis and Optimization of Nonlinear Vehicle Frame Structures
Won, Chong-Jin ; Lee, Jong-Sun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 20, issue 9, 1996, Pages 2833~2842
DOI : 10.22634/KSME-A.19126.96.36.19933
This paper is to practice optimal rigidity design by the strain energy density estimation method for static buckling and sizing design sensitivity analysis for dynamic buckling of a nonlinear vehicle frame structure from those results. Using these sizing design sensitivity resutls, an optimization of a nonlinear vehicle frame structure with dynamic buckling constraint is carrried out with the graient projection method.
Analysis of Shape Change of a Surface Crack during Stable Fatigue Growth
Chu, Seok-Jae ;
Transactions of the Korean Society of Mechanical Engineers A, volume 20, issue 9, 1996, Pages 2843~2853
DOI : 10.22634/KSME-A.19188.8.131.5243
The multi-point procedure is developed to predict the shape change of a semi-elliptical surface crack during stable fatigue crack growth. 3-D stress intensity factors along a crack front are calculated using the simplified 3-D J-intergral. Crack growth rate coefficient in the Paris law is assumed to be constant along the crack growth. Crack growth rate is set to be the distance between the two parallel tangent lines on the two semi-elliptic crack fronts before and after crack growth.
Configuration Control of Vaiable-Geometry Truss Structures
Roh, Tae-Hwan ; Kim, Tae-Ik ; Park, Hyun-Chul ; Kwon, Young-Doo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 20, issue 9, 1996, Pages 2854~2865
DOI : 10.22634/KSME-A.19184.108.40.20654
The concept of variable-geometry truss structure(VGTS) is introduced as a class of actively controlled adaptive structure. VGTS can purposefully vary its geometric configurations by changing the lengths of some members of the structure. General kinematics and inverse kinematics of a statically determinate VGTS(variable geometry truss structure) are studied. The solution technique is based on the Jacobian matrix obtained via joint equilibrium equations. Pseudoinverse control method is applied to resolve the redundancy of a large VGTS. two types of actuator layout of octahedral type VGTS, VG truss and Stewart platform, are compared. Introducing the concept of performance index, Stewart platform based layout was found to has less consumption energy and manipulation time. A functional VGTS model with 3 octahedral modules is designed and manufactured for the labaratory demonstration. Six vertically located length-variable members are used to create general 6 d.o.f. motions.
A Study on the Grinding Characteristics of Stainless Steel Using Intermittent Grinding Wheel
Kweun, O-Byung ; Kim, Jeong-Du ;
Transactions of the Korean Society of Mechanical Engineers A, volume 20, issue 9, 1996, Pages 2866~2874
DOI : 10.22634/KSME-A.19220.127.116.1166
In the grinding of difficult-to-materials, the major problmes of conventional grinding are grinding burn, wheel wear, grinding surface crack, loading and glazing, When a conventioanl grinding wheel is used, wheel wear and grinding surface crack easily occur in low heat conductive material and annealed steel. Intermittent grinding is suitable for diffcult-to-matrical such as stainless steel, titanium alloy, aluminum alloy and copper alloy. The purpose of this paper is to develop a new type intermittent wheel of the grinding system for improving the problem of stainless steel grinding, to observe the effect of intermittent grinding on surface quality and grinding characteristics of stainless steel grinding using intermittent grinding wheel. The characteristics of intermittent grinding system improve surface quality, low grinding temperature and low loading.
Dynamic Behavior Analysis of Stiffened Cylindrical Shell Filled with Fluid
Youm, Ki-Un ; Yoon, Kyung-Ho ; Lee, Young-Shin ; Kim, Jong-Kiun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 20, issue 9, 1996, Pages 2875~2886
DOI : 10.22634/KSME-A.1918.104.22.16875
This work present the experimental resutls for the free vibration of unstiffened, stiffened cylindrical shell filled with air, half water and full water. The natural frequencies and mode shapes of unstiffened, stiffened cylindrical shell are obtained experimentally also. The natural frequencies of stiffened cylindrical shell were generally highter than those of unstiffened cylindrical shell and natural requencies were decreased as cylindrical shell was filled with water. The effect of circumferential stiffener in the first mode was shown that natural frequency more increased 25% at air environment, 29% at half water environment and 37% at full water than those of unstiffened cylindrical shell, respectively. Also, the natural frequencies were decreased according to the added mass effect of fluid in the shell of unstiffened and stiffened cylindrical shell. The six mode shape results of all cases are simular and given. The natural frequencies are determined for a wide range of parameters : e.g. unstiffened shell, and filled with air, half and full water. The effects of varying the parameters on the free vibration frequencies and mode shapes are discussed.
A Solution of Variational Inequalities and A Priori Error Estimations in Contact Problems with Finite Element Method
Lee, Choon-Yeol ;
Transactions of the Korean Society of Mechanical Engineers A, volume 20, issue 9, 1996, Pages 2887~2893
DOI : 10.22634/KSME-A.1922.214.171.12487
Governing equations infrictional contact problems are introduced using variational inequality formulations which are regularized to overcome the diffculties of non-differentiability of the friction functional. Also finite element approximations and a priori error estimations are derived based on those formulations. Numerical simulations are performed illustrating the theoretical results.
Study on Plugging Criteria for Thru-wall Axial Crack in Roll Transition Zone of Steam Generator Tube
Park, Myeong-Gyu ; Kim, Yeong-Jong ; Jeon, Jang-Hwan ; Kim, Jong-Min ; Park, Jun-Su ;
Transactions of the Korean Society of Mechanical Engineers A, volume 20, issue 9, 1996, Pages 2894~2900
DOI : 10.22634/KSME-A.19126.96.36.19994
The stream generator tubes represent an integral part of a major barrier against the fission product release to the environment. So, the rupture of these tubes could permit flow of reactor coolant into the secondary system and injure the safety of reactor coolant system. Therefore, if the crack was detected during In-Service Inspection of tubes the cracked tube should be evaluated by the pulgging criteria and plugged or not. In this study, the fracture mechanics evaluation is carried out on the thru-wall axial crack due to Primary Water Stress Corrosion Cracking in the roll transition aone of steam generator tube to help the assurence the integrity of tubes and estabilish the plugging criteria. Due to the Inconel which is used as tube material is more ductile than others, the plastic instability repture theory was used to calculate the critical and allowable crack length. Based on Leak Before Break concept the leak rate for the critical crack length and the allowable leak rate are compared and the safety of tubes was given.
A Study on the Characteristics of Automatic Flatness Control System for Cold Rolling
Kim, Moon-Kyung ; Jeon, Eon-Chan ; Kim, Soon-Kyung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 20, issue 9, 1996, Pages 2901~2907
DOI : 10.22634/KSME-A.19188.8.131.5201
Flatness of cold rolled strip is vital to the quality of the product and productivity of the mill. Therefore, in recent year requirement for flatness control in strip rolling have become increasingly severe. The necessity for more accurate automatic gauge control and automatic flatness control(AFC) has increased by customer's requirement for cold rolled steel sheets with thinner gauge and better flatness quality. In this paper, the performance and functions of AFC system installed on the 4 hi-reversing mill has been investigated under actual conditions. The test results are as follows : The more strip thickness is thick, the smaller the I-value. The I-value is a strain measured by stressometer. Complex distributions of strip tension are controlled to remove not only a quarter buckle but also a simple center wave and edge wave. The defects caused by poor flatness have been drastically decreased. And a proper coolant temperature for work roll cooling system on the AFC system is about