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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 25, Issue 12 - Dec 2001
Volume 25, Issue 11 - Nov 2001
Volume 25, Issue 10 - Oct 2001
Volume 25, Issue 9 - Sep 2001
Volume 25, Issue 8 - Aug 2001
Volume 25, Issue 7 - Jul 2001
Volume 25, Issue 6 - Jun 2001
Volume 25, Issue 5 - May 2001
Volume 25, Issue 4 - Apr 2001
Volume 25, Issue 3 - Mar 2001
Volume 25, Issue 2 - Feb 2001
Volume 25, Issue 1 - Jan 2001
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Vibrational Analysis of Rotor Model considering the Dynamic Characteristics of the Support Structure
Choe, Bok-Rok ; Park, Jin-Mu ;
Transactions of the Korean Society of Mechanical Engineers A, volume 25, issue 4, 2001, Pages 555~563
DOI : 10.22634/KSME-A.2001.25.4.555
Support dynamics are often important in rotordynamic analyses. It may well happen in real situation of machines such as centrifugal pumps or turbines operating on flexible structure. This paper presents the applications of the impedance coupling method and the improved rotor model for including the support effects on the interaction with the rotor. The impedance coupling techniques are based on the FRFs of each substructure. Its dynamic stiffness matrix can be assembled to generate the system matrix, which satisfy the constraint conditions in the connection coordinates. And, the improved rotor uses the simplified spring-mass models as support properties. The equivalent support models are directly incorporated into the finite element rotor model. To verify the suggested analytical procedures, the results are compared to those of the pump system.
The Fiber Damage and Mechanical Properties of Short-fiber Reinforced Composite Depending on Nozzle Size Variations in Injection/Mold Sides
Lee, In-Seop ; Lee, Dong-Ju ;
Transactions of the Korean Society of Mechanical Engineers A, volume 25, issue 4, 2001, Pages 564~573
DOI : 10.22634/KSME-A.2001.25.4.564
The mechanical properties of short carbon/glass fiber reinforced polypropylene are experimentally measured as functions of fiber content and nozzle diameter. Also, these properties are compared with the survival rate of reinforced fibers and fiber volume fraction using image analysis after pyrolytic decomposition. The survival rate of fiber aspect ratio as well as fiber volume fraction is influenced by injection processing condition, the used materials and mold conditions such as diameter of nozzle, etc. In this study, the survival rate of fiber aspect ratio is investigated by nozzle size variations in injection/mold sides. It is found that the survival rate of glass fiber is higher that the survival rate of glass fiber is higher than that of carbon fiber. Both tensile modulus and strength of short-fiber reinforced polypropylene are improved s the fiber volume fraction and nozzle diameter are increased.
A Time-Domain Finite Element Formulation for Transient Dynamic Linear Elasticity
Sim, U-Jin ; Lee, Seong-Hui ;
Transactions of the Korean Society of Mechanical Engineers A, volume 25, issue 4, 2001, Pages 574~581
DOI : 10.22634/KSME-A.2001.25.4.574
Transient linear elastodynamic problems are numerically analyzed in a time-domain by the Finite Element Method, for which the variational formulation based upon the equations of motion in convolution integral is newly derived. This formulation is implicit and does not include the time derivative terms so that the computation procedure is simple and less assumptions are required comparing to the conventional time-domain dynamic numerical algorithms, being able to get the improved numerical accuracy and stability. That formulation is expanded using the semi-discrete approximation to obtain the finite element equations. In the temporal approximation, the time axis is divided equally and constant and linear time variations are assumed in those intervals. It is found that unconditionally stable numerical results are obtained in case of the constant time variation. Some numerical examples are given to show the versatility of the presented formulation.
A New Anisoparametric Out-of-Plane Deformable Curved Beam Element
Yu, Jae-Hyeong ; Yu, Seung-Won ; Min, Ok-Gi ;
Transactions of the Korean Society of Mechanical Engineers A, volume 25, issue 4, 2001, Pages 582~591
DOI : 10.22634/KSME-A.2001.25.4.582
It is known that the reduced integration, modified shape function, anisoparametric and non-conforming element can reduce the error induced by stiffness locking phenomenon in the finite element analysis. In this study, we propose new anisoparametric curved beam element. The new element based on reduced minimization theory is composed of different shape functions in each displacement field. By the substitution of this modified shape function, the unmatched coefficient that cause stiffness locking in the constraint energy is eliminated. To confirm the availability of this new model, we performed numerical tests for a simple model. As a result of numerical test, the undulate stress patterns are disappeared in static analysis, and displacements and stresses are close to exact solution. Not only in the static analysis but also in the eigen analysis of free vibrated curved beam model, this element shows successful convergent results.
The Mixture Ratio Effect of Epoxy Resin, Curing Agent and Accelerator on the Fatigue Behavior of FRMLs
Song, Sam-Hong ; Kim, Cheol-Ung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 25, issue 4, 2001, Pages 592~601
DOI : 10.22634/KSME-A.2001.25.4.592
Fiber reinforced metal laminates(FRMLs) are new types of hybrid materials. FRMLs consists of high strength metal(Al 5052-H34) and laminated fiber with structural adhesive bond. The mixture ratio effect of epoxy resin
accelerator on the fatigue behavior of FRMLs was investigated in this study. The epoxy, diglycidylether of bisphenol A(DGEBA), was cured by methylene dianiline(MDA) with or without an accelerator(K-54). Eight different kinds of resin mixture ratios were selected for the test ; five kinds of FRMLs(1) and three others of FRMLs(2). The relationship between da/dN and ΔK with variation of resin mixture ratio was studied. FRMLs(1) and FRMLs(2) indicated approximately 2 times and 2.2 times more improved maximum bending strengths in comparison with those of Al 5052-H34. The resin mixture ratio <1:1> in case of FRMLs(1) indicated the maximum fatigue life, while the resin mixture ratio <1:1:0.2> in case of FRMLs(2) indicated the maximum fatigue life. As results, FRMLs(2) turned out to have more effective characteristics on the fatigue properties and the bending strength than those of FRMLs(1).
Finite Element Analysis of Air Springs with Fiber-Reinforced Rubber Composites Using 3-D Shell Elements
Lee, Hyoung-Wook ; Huh, Hoon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 25, issue 4, 2001, Pages 602~609
DOI : 10.22634/KSME-A.2001.25.4.602
This paper is concerned with the orthotropic problem of diaphragm-type air springs which consist of rubber linings, nylon reinforced rubber composite and bead ring. The analysis is carried out with a finite element method developed to consider the orthotropic properties, geometric nonlinearity using four-node degenerated shell element with reduced integration. Physical stabilization scheme is used to control the zeroenergy mode of the element. The analysis includes an inflation analysis and a lateral analysis of an air spring for the deformed shape and the spring load with respect to the vertical and l ateral deflection. Numerical results demonstrate the variation of the outer diameter, the fold height, the vertical force and the lateral force with respect to the inflation pressure and the lateral deflection.
Development of Kinematic Analysis Technique for Structural Design of Single Arm type Pantograph
Jeong, Gyeong-Ryeol ; Park, Su-Hong ; Kim, Hwi-Jun ; Bae, Jeong-Chan ;
Transactions of the Korean Society of Mechanical Engineers A, volume 25, issue 4, 2001, Pages 610~618
DOI : 10.22634/KSME-A.2001.25.4.610
Pantograph, which collects current from cartenary system, is one of the important parts of high-speed train. Kinematic analysis is one of the key technologies for pantograph design and includes joint trajectories, reaction forces, and the required moment of main shaft calculations. The kinematic analysis, however, is very complex and time-consuming process. In this study PC based pantograph kinematic analysis software using graphical user interface tool was developed for the easy evaluations of kinematic characteristics necessary in pantograph design process.
A Viscoelastic Constitutive Model of Rubber Under Small Oscillatory Loads Superimposed on Large static Deformation
Kim, Bong-Gyu ; Yun, Seong-Gi ;
Transactions of the Korean Society of Mechanical Engineers A, volume 25, issue 4, 2001, Pages 619~628
DOI : 10.22634/KSME-A.2001.25.4.619
A viscoelastic constitutive equation of rubber is proposed under small oscillatory load superimposed on large static deformation. The proposed model is derived through linearization of Simos nonlinear viscoelastic constitutive model and reference configuration transformation. Statically pre-deformed state is used as reference configuration. The model is extended to a generalized viscoelastic constitutive equation including widely-used Mormans model. Static deformation correction factor is introduced to consider the influence of pre-strain on the relaxation function. The model is tested for dynamic behavior of rubbers with different carbon black fractions. It is shown that the constitutive equation with static deformation correction factor agrees well with test results.
Development of Experimental Setup for Impact Punching in Brittle Materials and Analysis of Punching Mechanism
Sin, Hyeong-Seop ; Kim, Jin-Han ; O, Sang-Yeop ;
Transactions of the Korean Society of Mechanical Engineers A, volume 25, issue 4, 2001, Pages 629~636
DOI : 10.22634/KSME-A.2001.25.4.629
In order to investigate the possibility of impact punching in brittle materials, an experimental setup was developed. In the setup, a long bar as a punch was used to apply the impact load to the specimen plate and measure the applied impact force during the impact punching process. Impact punching tests with various shape of punches were performed in soda-lime glass and silicon wafer under a different level of contact pressure. The damage appearance after the impact punching was examined according to the applied contact pressure. The minimum contact pressure required for a complete punching in glass specimens without development of radial cracks around the punched hole was sought at each condition. The minimum contact pressure increased with increasing the thickness of specimens and decreasing the end radius of punches. The profile of impact forces was measured during the impact punching experiment, and it could explain well the behavior of the punching process in brittle material plates. The measured impact force increased with increasing the contact pressure applied to the plates.
Axiomatic Design of Mold System for Advance of Foaming Magnitude
Hwang, Yun-Dong ; Cha, Seong-Un ;
Transactions of the Korean Society of Mechanical Engineers A, volume 25, issue 4, 2001, Pages 637~644
DOI : 10.22634/KSME-A.2001.25.4.637
Polymer materials have a lot of merits including the low cost and the easiness of forming. For these reasons they are widely using at many manufacturing industries. Microcellular foaming process appeared at MIT in 1980s to save a quantity of material and increase mechanical properties. There are many process variables in appling microcellular foaming process to the conventional injection molding process. They can be solved by using Axiomatic Design Method which is very useful design method for designing a new product. Its main character is scientific and analytical. The information about the thickness of cavity plays an important role in making an effective foam. The goal of this research is to design mold system for advance of foaming magnitude with axiomatic design method. There is a relation between the change of cavitys thickness and foaming magnitude made after inserting a gas. R/t is a conception that indicate proportion between radius and thickness of cavity in mold system. By means of SEM observation of side surface of cavity sample, foaming magnitude of polymer in microcellular foaming process is decreasing gradually as the value of R/t is increasing. In this paper, an advanced mold system was presented by mapping the relation between functional requirements and design parameters.
Shape Optimization of a Rotating Cantilever Beam Considering Its Modal and Stress Characteristics
Yun, Yeong-Hun ; Yu, Hong-Hui ;
Transactions of the Korean Society of Mechanical Engineers A, volume 25, issue 4, 2001, Pages 645~653
DOI : 10.22634/KSME-A.2001.25.4.645
It is well known that natural frequencies increase when a cantilever beam rotates about the axis perpendicular to its longitudinal axis. Such phenomena that are caused by centrifugal inertia forces are often referred to as the stiffening effects. Occasionally it is necessary to control the variation of a natural frequency or the maximum stress of a rotating beam. By changing the thickness of the rotating beam, the modal or the stress characteristics can be changed. The thickness of the rotating beam is assumed to be a cubic spline function in the present work. An optimization method is employed to find the optimal thickness shape of the rotating beam. This method can be utilized for the design of rotating structures such as turbine blades and aircraft rotary wings.
Fatigue Properties of Rail Steel Under Constant Amplitude Loading and Variable Amplitude Loading
Kim, Cheol-Su ; Kim, Jeong-Gyu ;
Transactions of the Korean Society of Mechanical Engineers A, volume 25, issue 4, 2001, Pages 654~661
DOI : 10.22634/KSME-A.2001.25.4.654
In this study, fatigue growth behavior of the transverse crack, which was the most dangerous damage among the various types of rail defects, was investigated using the notched keyhole specimen under constant amplitude loadings. Fatigue limit of smooth specimen in rail steel at R=0 was 110MPa, and the fatigue crack initiation life in the region of the low stress amplitude (ie. long life) occupied the major portion of the total fatigue life. The fatigue strength under variable amplitude loading was converted to the equivalent fatigue strength based upon. Miners rule, which was estimated approximately 9% lower than that under constant amplitude loading. Also, in the low ΔK(sub)rms region (
21MPa√m), fatigue crack growth rate (da/dN) under constant amplitude loading was higher than that under variable amplitude loading, whereas the tendency was reversed in the high ΔK(sub)rms region. It is believed that this behavior is due to the transition of fracture appearance.
Overload Analysis and
Based Fatigue Life Prediction of Spot-Welded Auto Seat Belt Anchors
Choe, Jin-Yong ; Lee, Hyeong-Il ;
Transactions of the Korean Society of Mechanical Engineers A, volume 25, issue 4, 2001, Pages 662~670
DOI : 10.22634/KSME-A.2001.25.4.662
We evaluate the effectiveness and validity of J(sub)e, which comprehensively describes the effects of specimen geometry and loading type, in predicting the fatigue life of auto seat belt anchor panel. We first simplify the heat affected zone model to reduce the number of finite elements. We then establish finite element models reflecting the actual overload behavior of 3 types of seat belt anchor specimens. Using finite element models elaborately established, we obtain the effective crack driving parameter J(sub)e composed of its ductility-dependent modal components. It is confirmed that the J(sub)e concept successfully predicts the fatigue life of multi-spot welded panel structures represented by auto seat belt anchors here.
Global Optimization of Composite Structures Using Triangular Patch Algorithm
O, Seung-Hwan ; Lee, Byeong-Chae ;
Transactions of the Korean Society of Mechanical Engineers A, volume 25, issue 4, 2001, Pages 671~684
DOI : 10.22634/KSME-A.2001.25.4.671
Several design problems of composite structures are studied via a global optimizer based on attraction regions. MSC/NASTRAN is adopted for static and eigenvalue analysis. The method of modified feasible direction in DOT is used for local optimization. Through the review of global optimization algorithms, the triangular patch algorithm is selected because the algorithm is known to be efficient, robust and powerful for general nonlinear optimization problems. For general applicability, various mechanical properties are considered as design objectives; strain energy, eigenvalue, weight, displacement, and buckling load. In all cases considered, the triangular patch algorithm results in a lot of optimum points and useful design patterns, that are not easy by local algorithms or conventional global algorithms can be determined.
Development of a Stance and Swing Phase Control Transfemoral Prosthesis
Kim, Sin-Gi ; Kim, Gyeong-Hun ; Mun, Mu-Seong ; Lee, Sun-Geol ; Baek, Yeong-Nam ;
Transactions of the Korean Society of Mechanical Engineers A, volume 25, issue 4, 2001, Pages 685~694
DOI : 10.22634/KSME-A.2001.25.4.685
In this study, a transfemoral prosthesis system of which both stance phase and swing phase are controllable has been developed for the recovery of the biomechanical function of the amputated leg. It consists of a 5 bar link mechanism, a hydraulic-rubber knee damper for stance phase control and a pneumatic cylinder controlled via a microprocessor for stance phase control. The mechanical characteristics of the knee damper which absorbs the impact energy generated at the heel contact were investigated. The characteristics of the pneumatic cylinder essential for the speed adaptation of the prosthesis during swing phase were also studied for its mechanical characteristics. The prosthesis was subject to the clinical tests, and the gait characteristics obtained were very close to those of normal subjects. The stance and swing controlled prosthesis that were developed in this study showed good stability during the stance phase and showed good controllability during the swing phase.
Drop/Impact Simulation and Experimental Verification of Mobile Phone
Kim, Jin-Gon ; Lee, Jun-Yeong ; Lee, Sin-Yeong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 25, issue 4, 2001, Pages 695~702
DOI : 10.22634/KSME-A.2001.25.4.695
In this paper, the drop/impact simulation for a mobile phone has been carried out with the explicit code LS-DYNA and its validation has been experimentally verified. The small size of this kind of electronics products makes it time-consuming, and difficult to conduct drop tests to detect the failure mechanism and identify their drop behaviors. Strict drop/impact performance criteria of such hand held electronic products as mobile phones play an important role in their design because these products must withstand both normal and unexpected shock. Usually, the product durability on drop impact depends on designers experience. The present reliable methodology of drop/impact simulation provides an efficient and powerful vehicle to improve the design quality and reduce the design period.
Mixed-Mode Stress intensity Factors for Elliptical Corner Cracks in Mechanical Joints by Weight Function Method
Heo, Seong-Pil ; Yang, Won-Ho ; Kim, Cheol ;
Transactions of the Korean Society of Mechanical Engineers A, volume 25, issue 4, 2001, Pages 703~713
DOI : 10.22634/KSME-A.2001.25.4.703
Mechanical joints such as bolted or riveted joints are widely used in structural components and the reliable determination of the stress intensity factors for corner cracks in mechanical joints is needed to evaluate the safety and fatigue life. This paper analyzes the mixed-mode stress intensity factors of surface and deepest points for quarter elliptical corner cracks in mechanical joints by weight function method and the coefficients included in weight function are determined by finite element analyses for reference loadings. The extended form of the weight function method for two-dimensional mixed-mode to three-dimensional is presented and the number of terms in weight function is determined by comparing the results for the different number of terms. The amount of clearance is an important factor in evaluating the severity of elliptical corner cracks in mechanical joints and even horizontal crack normal to the applied load is under mixed-mode in the case that clearance exists.
Some Remarks on the Spherical Indentation Theory
Lee, Jin-Haeng ; Lee, Hyeong-Il ; Song, Won-Geun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 25, issue 4, 2001, Pages 714~724
DOI : 10.22634/KSME-A.2001.25.4.714
In this work, some inaccuracies and limitation of prior indentation theory, which is based on the deformation theory of plasticity and experimental observations, are first investigated. Then effects of major material properties on the configuration of indentation load-deflection curve are examined via incremental plasticity theory based finite element analyses. It is confirmed that subindenter deformation and stress-strain distribution from the deformation theory of plasticity are quite dissimilar to those from incremental theory of plasticity. We finally suggest the optimal data acquisition location, where the strain gradient is the least and the effect of friction is negligible. This data acquisition point increases the strain range by a factor of five.
Optimum Design of Head Slider with Ultra-Thin Air-Lubricated Spacing for Enhanced Flying Characteristics
Gang, Tae-Sik ; Choe, Dong-Hun ; Jeong, Tae-Geon ; Park, No-Yeol ; Lee, Seong-Chang ;
Transactions of the Korean Society of Mechanical Engineers A, volume 25, issue 4, 2001, Pages 725~733
DOI : 10.22634/KSME-A.2001.25.4.725
Flying attitudes of the slider, which are flying height, pitch and roll, are affected by the air flow velocity, the skew angle, and the manufacturing tolerances. Traditional designs of the air bearing surface have considered only the flying performances for the variations in the air flow velocity and the skew angle, which are determined by the radial position. In this study, we present the new shape design of the air bearing surface by considering the track seek performance and the air bearing stiffness as well as the traditional design requirements. The optimization technique is used to improve the dynamic characteristics and operating performance of the newly proposed air bearing surface shape design further. The optimized configuration is obtained automatically and the optimally designed sliders show the enhanced flying and dynamic characteristics.
Calculation of Stres Intensity Factor in Arbitrarily Shaped Plane Crack by Mobius Transformation
An, Deuk-Man ;
Transactions of the Korean Society of Mechanical Engineers A, volume 25, issue 4, 2001, Pages 734~740
DOI : 10.22634/KSME-A.2001.25.4.734
In this paper the stress intensity factor under uniform pressure in the arbitrarily-shaped plane crack configuration transformed elliptic crack by Mobius mapping are determined. Using Dysons formula Boussinesq-Papkovich potentials for mode I deformation are constructed. In the example the stress intensity factors are approximately calculated by least square method.
Application of enhanced Reference Stress Method to Nuclear Piping LBB Analysis : Finite Element Validation
Heo, Nam-Su ; Kim, Yun-Jae ; Kim, Yeong-Jin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 25, issue 4, 2001, Pages 741~747
DOI : 10.22634/KSME-A.2001.25.4.741
Three-dimensional, elastic-plastic finite element analyses for circumferential through-wall cracked pipes are performed using actual tensile data of stainless steels, for two purposes. The first one is to validate the recently-proposed enhanced reference stress (ERS) method to estimate the J-integral and COD for circumferential through-wall cracked pipes. The second one is to compare those results with the GE/EPRI estimations. It is found that the J-integral and COD estimations according to the GE/EPRI method can be very sensitive to how the stress-strain data are fitted using the Ramberg-Osgood relation. Moreover, no tendency can be found regarding the most appropriate fitting range for the Ramberg-Osgood fit. On the contrary, the J-integral and COD estimations based on the ERS method give more accurate results than the GE/EPRI estimation. The present results provide confidence in applying the proposed method to the Leak-Before-Break(LBB) analysis.
A Study of Rotor Vibration Reduction using Fuzzy Magnetic Damper System
Lee, Hyeong-Bok ; Kim, Yeong-Bae ;
Transactions of the Korean Society of Mechanical Engineers A, volume 25, issue 4, 2001, Pages 748~755
DOI : 10.22634/KSME-A.2001.25.4.748
This paper concerns rotor vibration reduction using magnetic damper system. The fuzzy control logic is utilized to fulfill desired motion. The fuzzy system structure and membership function were first determined by simulation results. The researched control logic contains two fuzzy controller : reference position variation according to the rotor whirling status and error compensation algorithm to minimize the rotor vibration due to unbalance and unstable fluid film force. The Sugeno type output membership function was utilized by several trials and optimized membership function constants were selected from experiments. The experimental results show that the proposed method effectively control and reduce the rotor vibration with fluid film bearings.
Evaluation of the Crack Tip Stress Distribution Considering Constraint Effects in the Reactor Pressure Vessel
Kim, Jin-Su ; Choe, Jae-Bung ; Kim, Yeong-Jin ;
Transactions of the Korean Society of Mechanical Engineers A, volume 25, issue 4, 2001, Pages 756~763
DOI : 10.22634/KSME-A.2001.25.4.756
In the process of integrity evaluation for nuclear power plant components, a series of fracture mechanics evaluation on surface cracks in reactor pressure vessel(RPV) must be conducted. These fracture mechanics evaluation are based on stress intensity factor, K. However, under pressurized thermal shock(PTS) conditions, the combination of thermal and mechanical stress by steep temperature gradient and internal pressure causes considerably high tensile stress at the inside of RPV wall. Besides, the internal pressure during the normal operation produces high tensile stress at the RPV wall. As a result, cracks on inner surface of RPVs may experience elastic-plastic behavior which can be explained with J-integral. In such a case, however, J-integral may possibly lose its validity due to constraint effect. In this paper, in order to verify the suitability of J-integral, tow dimensional finite element analyses were applied for various surface cracks. A total of 18 crack geometries were analyzed, and
stresses were obtained by comparing resulting HRR stress distribution with corresponding actual stress distributions. In conclusion, HRR stress fields were found to overestimate the actual crack-tip stress field due to constraint effect.