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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 24, Issue 12 - Dec 2000
Volume 24, Issue 11 - Nov 2000
Volume 24, Issue 10 - Oct 2000
Volume 24, Issue 9 - Sep 2000
Volume 24, Issue 8 - Aug 2000
Volume 24, Issue 7 - Jul 2000
Volume 24, Issue 6 - Jun 2000
Volume 24, Issue 5 - May 2000
Volume 24, Issue 4 - Apr 2000
Volume 24, Issue 3 - Mar 2000
Volume 24, Issue 2 - Feb 2000
Volume 24, Issue 1 - Jan 2000
Selecting the target year
A Study on Biomechanical Noise Reduction Technique Using Length Information
Gang, Sin-Gil ; Yun, Yong-San ; Park, Jae-Hui ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1643~1649
DOI : 10.22634/KSME-A.2000.24.7.1643
When markers attached to body segment are captured by camera, they generally have many noises due to intrinsic biomechanical characteristics. In this study, one technique to reduce these noises is suggested, which constructs a local coordinates of the markers using time-mean lengths of the measured markers and calculates a linear transformation matrix of the interesting body using least square error technique. This matrix is decomposed into two matrices of rotation and flexibility. Suggested method does well for 3 markers or more, and shows consistent results without regard to choice of reference axis.
Dynamic Bulging Behavior Analysis by Finite Difference Method in High Speed Continuous Casting of Thin Slab
Jeong, Yeong-Jin ; Sin, Geon ; Jo, Gi-Hyeon ; Gang, Chung-Gil ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1650~1660
DOI : 10.22634/KSME-A.2000.24.7.1650
Continuous casting process has been adopted increasingly in recent years to save both energy and labor. It has experienced a rapid development in the production of semi-finished steel products, rep lacing the conventional route of ingot casting and rolling. In order to achieve this merit, however, more studies about the mechanism between roll and slab are needed. In this paper, a dynamic bulging in steel cast slabs was simulated by considering the solidification and heat transfer. This study is to prevent internal cracks of a slab in a bending and unbending zone. The value of moving strand shell bulging between two supporting rollers under the ferrostatic pressure and slab-self weight has been calculated in terms of creep and elasto-plasticity. The strain and strain rate distributions in solidified shell undergoing a series of bulging are calculated with working boundary conditions.
Multi-Objective Optimum Shape Design of Rotor-Bearing System with Dynamic Constraints Using Immune-Genetic Algorithm
Choe, Byeong-Geun ; Yang, Bo-Seok ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1661~1672
DOI : 10.22634/KSME-A.2000.24.7.1661
An immune system has powerful abilities such as memory, recognition and learning how to respond to invading antigens, and has been applied to many engineering algorithms in recent year. In this pap er, the combined optimization algorithm (Immune- Genetic Algorithm: IGA) is proposed for multi-optimization problems by introducing the capability of the immune system that controls the proliferation of clones to the genetic algorithm. The optimizing ability of the proposed combined algorithm is identified by comparing the result of optimization with simple genetic algorithm for two dimensional multi-peak function which have many local optimums. Also the new combined algorithm is applied to minimize the total weight of the shaft and the transmitted forces at the bearings. The inner diameter oil the shaft and the bearing stiffness are chosen as the design variables. The dynamic characteristics are determined by applying the generalized FEM. The results show that the combined algorithm and reduce both the weight of the shaft and the transmitted forces at the bearing with dynamic conatriants.
Evaluation of Degradation Behavior of the Long-Term Serviced Boiler Header
Gwon, Jae-Do ; Bae, Yong-Tak ; Choe, Seong-Jong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1673~1680
DOI : 10.22634/KSME-A.2000.24.7.1673
The degradation of a boiler header constructed by a material, 1Cr-0.5Mo steel in a fossil power plant is observed when the header is exposed for a long period to the high temperature and pressure. The present investigations are for evaluating the effect of the degradation on the material, such as its strength changes. Reheat-treated metal is used to compare the mechanical properties of the degraded and that of reheat-treated materials. Through the investigation, following results are obtained 1) the area ratio of ferrite in the reheat-treated material is larger than that of the degraded material, 2) the hardness and tensile strength of the degraded material are lower than that of the reheat-treated material, 3) the ductile-brittle transition temperature(DBTT) increased toward high temperature region, 4) the fatigue crack growth rate(FCGR) of the degraded material is higher than that of the reheat-treated material in the region of low ΔK value while FCGR of the both materials are similar in high ΔK region.
Prediction of Surface Topography by Dynamic Model in High Speed End Milling
Lee, Gi-Yong ; Ha, Geon-Ho ; Gang, Myeong-Chang ; Lee, Deuk-U ; Kim, Jeong-Seok ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1681~1688
DOI : 10.22634/KSME-A.2000.24.7.1681
A dynamic model for the prediction of surface topography in high speed end milling process is developed. In this model the effect of tool runout, tool deflection and spindle vibration were taken in to account. An equivalent diameter of end mill is obtained by finite element method and tool deflection experiment. A modal parameter of machine tool is extracted by using frequency response function. The tool deflection, spindle vibration chip thickness and cutting force were calculated in dynamic cutting condition. The tooth pass is calculated at the current angular position for each point of contact between the tool and the workpiece. The new dynamic model for surface predition are compared with several investigated model. It is shown that new dynamic model is more effective to predict surface topography than other suggested models. In high speed end milling, the tool vibration has more effect on surface topography than the tool deflection.
Adaptive Control of Flexible-Link Robots
Lee, Ho-Hun ; Kim, Hyeon-Gi ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1689~1696
DOI : 10.22634/KSME-A.2000.24.7.1689
This paper proposes a new adaptive control scheme for flexible-link robots. A model-based nonlinear control scheme is designed based on a V-shape Lyapunov function, and then the nonlinear control i s extended to a model-based adaptive control to cope with parametric uncertainties in the dynamic model. The proposed control guarantees the global exponential or global asymptotic stability of the overall control system with all internal signals bounded. The effectiveness of the proposed control is shown by computer simulation.
Effects of the Glass Fiber Characteristics on the Mechanical Properties of Thermoplastic Composite
Lee, Jung-Hui ; Lee, Jeong-Gwon ; Lee, Gyeong-Yeop ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1697~1702
DOI : 10.22634/KSME-A.2000.24.7.1697
This study has been performed to investigate the effects of glass fiber characteristics on the mechanical properties of thermoplastic composite. The surface of glass fiber was coated with the silan e to enhance the bonding strength between fiber and matrix. A micro-droplet pull-off test was performed to investigate the influence of the silane concentration on the bonding strength. The maximum bonding strength was observed around 10.8% silane concentration. In order to examine the influence of the fiber length and fiber content on the properties of the composite, the composite materials involving tile fiber lengths of 5mm, 10mm, 15mm 20mm, and 25mm were tested. The composites used contain 20%, 30%, and 40% by weight of glass fibers. Tension and flexural tests were performed to investigate their mechanical properties of the composites. The tensile strength and tensile modulus of the composite increase with increasing the glass fiber content. The tensile modulus increases slightly with increasing the fiber length. The maximum tensile strength is observed around the fiber length of 15-20mm. The flexural modulus and strength also increase slightly with increasing the fiber length.
Microstructural Morphology of Molded Thin Composites of Thermotropic Liquid Crystalline Polymer and Polyamide 6
Choe, Nak-Sam ; Choe, Gi-Yeong ; Ha, Seong-Gyu ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1703~1711
DOI : 10.22634/KSME-A.2000.24.7.1703
Microstructural morphology of molded composites of thermotropic liquid crystalline polymer(LCP) and polyamide 6 (PA6) has been studied as a function of epoxy fraction. Injection-moulding of a thin composite plaque at a temperature below the melting point of the LCP fibrils by suing the extruded LCP/PA6 pellets produced multi-layered structures: 1) the surface skin layer with thickness of 65-120 ym exhibiting a transverse orientation, 2) the sub-skin layer with an orientation perpendicular to the surface skin, i.e. in the flow direction, 3) the core layer with arc-curved flow patterns. Similar microstructural orientations were observed in the respective layers for the composite plaques with different fractions of epoxy.
Dynamic Analysis of Constrained Multibody Systems Undergoing Collision with Friction
Park, Jeong-Hun ; Hwang, Yo-Ha ; Yu, Hong-Hui ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1712~1720
DOI : 10.22634/KSME-A.2000.24.7.1712
An Eccentric Degenerated Shell Element for the Geometrically Nonlinear Analysis of Stiffened Structures
Lee, Won-Jae ; Lee, Byeong-Chae ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1721~1730
DOI : 10.22634/KSME-A.2000.24.7.1721
An eccentric degenerated shell element with geometric non-linearity for the precise and efficient analysis of stiffened shell structures is developed. To deal with the eccentricity, we define the e ccentric shell and the master shell that constitute one combined shell. It is assumed that the sections remain plane after deformation. The internal force vector and the tangent stiffness matrix based on the virtual work principle in the natural coordinate system are derived. To enhance the robustness of the element, assumed strain method for transverse shear and membrane strains is used. Through numerical experiments the effectiveness of the proposed element is demonstrated.
Fault Diagnosis of Gear Chain Using Vibration Signal
Bae, Beom-Won ; Choe, Yeon-Seon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1731~1739
DOI : 10.22634/KSME-A.2000.24.7.1731
The Vibration signals of a gear driving system is often associated with gear tooth faults. Many studies have been done on the detection of impulsive vibration signals, which characterize the breaka ge of a gear tooth. Also, most of the studies on gear fault diagnosis are only about the fault existence at one gear-pair. This study concerns on the several possible faults of a geared motor that has three gear pairs. The measurement and analysis on the vibration signals of a running geared motor shows the relationship between the gear faults and the vibration signals. This study also shows that adaptive interference canceling technique can be appropriately applicable to detect which gear-pair has the fault, and that wavelet is better than spectrogram to figure out the gear fault.
Shakedown Analysis of Shaft in Bearing-Shaft Assembly
Park, Heung-Geun ; Park, Jin-Mu ; O, Yun-Chan ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1740~1747
DOI : 10.22634/KSME-A.2000.24.7.1740
Under repeated rolling, initial plastic deformation introduces residual stresses which render the steady cyclic state purely elastic. This is called the process of shakedown. Many studies have been done about the shakedown in semi-infinite half space using calculated Hertizian pressure. In this paper shakedown processes in a shaft are studied by finite element analyses of a two dimensional(plane strain) model with elastic-linear-kinematic-hardening-plastic material subjected to repeated, frictionless rolling contact. Symmetric and non-symmetric pressure distributions are obtained using a simplified model of the bearing-shaft assembly. The rolling contact is simulated by repeatedly translating both pressure distributions along the surface of the shaft. By the influence of the non-symmetric pressure, larger residual radial tensile stress is generated in the immediate subsurface layer, which may make a crack propagate and, the subsurface undergoes a zigzag plastic deformation during the shakedown process, which may lead to a crack initiation.
Measurement Technique of Cutting Temperatures Using Implanted Thermocouples in Ball End-Milling
Lee, Deuk-U ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1748~1752
DOI : 10.22634/KSME-A.2000.24.7.1748
In this paper, the measurement technique of cutting temperatures of shear zone using implanted thermocouples is proposed in ball end milling. K-type thermocouple implanted in the hole of workpieces is directly cut in order to measure temperatures of the shear zone in cutting process. Experiments are performed for a nickel based superalloy(Inconel 718) using a ball nose end mill. The results show that the cutting temperature in shear zone is about 3200C at the cutting speed of 90m/min with dry.
Inverse Analysis Approach to Flow Stress Evaluation by Small Punch Test
Cheon, Jin-Sik ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1753~1762
DOI : 10.22634/KSME-A.2000.24.7.1753
An inverse method is presented to obtain material's flow properties by using small punch test. This procedure employs, as the objective function of inverse analysis, the balance of measured load-di splacement response and calculated one during deformation. In order to guarantee convergence to global minimum, simulated annealing method was adopted to optimize the current objective function. In addition, artificial neural network was used to predict the load-displacement response under given material parameters which is the most time consuming and limits applications of global optimization methods to these kinds of problems. By implementing the simulated annealing for optimization along with calculating load-displacement curve by neural network, material parameters were identified irrespective of initial values within very short time for simulated test data. We also tested the present method for error-containing experimental data and showed that the flow properties of material were well predicted.
Adaptive Finite Element Mesh Construction for Optimal Design of Spot Welding
Park, Jang-Won ; Chae, Su-Won ; Lee, Tae-Su ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1763~1770
DOI : 10.22634/KSME-A.2000.24.7.1763
A finite element interface system for the design of optimal spot welding locations has been developed. In order to find out the optimal locations of spot welding points, iterative finite element an alyses are necessary, and thus automatic generation of finite element model for the structures with spot welded pointsis required. In this interface system, quadrilateral shell elements are automatically generated for finite element analysis of spot welded structured, which employs a domain decomposition methodand adaptive mesh(h-method).
A Study on the Mechanical Strength Change by Thermal Aging of 2.25Cr-1Mo Steel
Yang, Hyeon-Tae ; Kim, Sang-Tae ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1771~1778
DOI : 10.22634/KSME-A.2000.24.7.1771
The purpose of this study is to investigate the thermal embrittlement and the mechanical properties of 2.25Cr-1Mo steel aged at high temperature for the extended periods. Original, aged artificiall y and used material were tested to obtain the tensile strength, hardness and impact absorbed energy. Tensile strength, hardness and impact absorbed energy decreased with the increasing aging time. The carbide morphology with the thermal embrittlement was found to contribute to the mechanical property change by X-Ray diffraction method.
Development of Integrated System for Virtual Design and Performance Testing of Automobile Seat
Im, O-Gang ; Yu, Wan-Seok ; Jeong, Yung-Ho ; Kim, Gwang-Seok ; Lee, Jin-Sik ; No, Hyo-Cheol ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1779~1786
DOI : 10.22634/KSME-A.2000.24.7.1779
Most of traditional design processes of mechanical parts are regarded as sequential and discrete, since different kinds of softwas should be introduced. In this paper, we develop an integrated fram ework for virtual design and performance testing of an automobile seat. The system is composed of four modules, i.e. CAD, static analysis, dynamic analysis, and draft drawing module. In the CAD module, PRO/ENGINEER 3D seat model is created using parameters to be modified with the result of static and dynamic analysis. In the static analysis, headrest tere used in each design stage make it difficult to feedback their results to upstream process. These discrete processes may result in time loss and cost rise. In recent years, life cycle of product is reduced. To have competence with others, new concept design processt is simulated using ANSYS. In the dynamic analysis module, FMVSS201 test is simulated using DADS. Overall data flow is controlled by Motif. The advantage of the system is that even a novice can perform and review the whole design process, without a good hand at professional design/analysis S/W in each stage. The system also provides a virtual design space, where engineers in different development stage can access common data of design models. The concept could be applied to other fields and it could reduce time and money required in design process.
An Experimental Study on The Removal of Weldline by Moving Core Method
Yun, Gyeong-Hwan ; Jo, Gwang-Hwan ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1787~1794
DOI : 10.22634/KSME-A.2000.24.7.1787
Injection molding is one of the most popular processes in plastic industry. Despite the significant progresses in technical point of view there are still problems to be solved in injection molding process. One of these problems is well-known weldline. A weldline is formed when the two flow front seperates and rejoins during the filling process. The flow front separation is caused by an obstruction in the cavity such as core, inserts and multiple gates. The typical occurrence of weldlines is one of the most undesirable phenomena in injection molding because the molded product's appearance is damaged and its strength is reduced considerably. A major factor which weakens the strength is the V-notch structure in its surface and parallel molecular orientation in inner structure. Several methods were tried to remove the weldline in injection-molded parts, but in fail. In the present paper a new technique to remove the weldline is proposed. This technique is named as ,'moving core method
Analytical Analysis of Cogging Torque in Motors of Permanent MagneticType
Go, Hong-Seok ; Kim, Gwang-Jun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1795~1800
DOI : 10.22634/KSME-A.2000.24.7.1795
One of the principal sources of vibration and noise in permanent magnetic machines is cogging torque, which is induced by interaction between the rotor poles and the stator teeth. For its analysis, using finite element analysis is very time consuming and the calculation of performance factors is extremely sensitive to the discretization. Especially, Maxwell stress tensor method is sensitive to the location of integral path. In this paper, a cogging permeance fuction is defined and replaced by the straight line. And it is assumed that the flux density acting on the stator's tooth side is the euqal to the flux density of the slot area. Using this definition and assumption, analytical calculation of cogging torque is presented and validated. And several reduction method is introduced.
Topology Optimization of a HDD Actuator Arm
Chang, Su-Young ; Youn, Sung-Kie ; Kim, Cheol-Soon ; Oh, Dong-Ho ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1801~1809
DOI : 10.22634/KSME-A.2000.24.7.1801
A study on the topology optimization of Hard-Disk-Driver(HDD) actuator arm in free vibration is presented. The purpose of this research is to increasse the natural frequency of the first lateral mode of the HDD actuator arm under the constraint of total moment of inertia, so as to facilitate the position control of high speed actuator am. The first lateral mode is an important factor in the position control process. Thus the topology optimization for 2-D model of the HDD actuator arm is considered. A new objective function corresponding to multieigenvalue optimization is suggested to improve the solution of the eigenvalue optimization problem. The material density of the structure is treated as the design variable and the intermediate density is penalized. The effects of different element types and material property functions on the final topology are studied. When the problem is discretized using 8-node element of a uniform density, the smoothly-varying density field is obtained without checker-board patterns incurred. As a result of the study an improved design of the HDD actuator arm is suggested. Dynamic characteristics of the suggested design are compared computationally with those of the old design. With the same amount of the moment of inertia, the natural frequency of the first lateral mode or the suggested design is subsequently increased over the existing one.
Statistical Properties for Tensile strength of Composite Materials Patched with AFRP on 2024-T3 Aluminum Alloy plate
Yun, Han-Gi ; An, Won-Gi ; Heo, Seon-Cheol ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1810~1816
DOI : 10.22634/KSME-A.2000.24.7.1810
A hybrid composite APAL(Aramid Patched Aluminum alloy) , consisting of Al 2024-T3 aluminum alloy plate sandwiched between two aramid/epoxy laminates, was developed. The characteristics of tensile s trength were investigated and statistical properties of tensile strength were studied in terms of Weibull distribution probability with number of AFRP laminates. The tensile strength of APAL was inproportional to number of AFRP laminates and followed the two-parametic Weibull distribution.
Study on the Evaluation of Fracture Toughness at Welded Zone for the Pipe Steel by
Na, Ui-Gyun ; Yu, Hyo-Seon ; O, Seok-Hyeong ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1817~1825
DOI : 10.22634/KSME-A.2000.24.7.1817
The purpose of this study is to examine the fracture toughness of the welded pipe from the viewpoint of FATT for the S38 and S42 steels used widely as the pipe material. Post weld heat treatment(PW HT) was carried out like following conditions: temperature of 67
, I hour of holding time and cooling in furnace. Fracture toughness was obtained by measuring the crack opening displacement(COD) of the notched specimens over the range of temperature from -14
. Hardness values at fusion line near around were the highest and the microstructures at welded zone were coarsened. Regardless of the pipe materials, COD and temperature curves of the as-welds were moved toward higher temperature compared with those of the parents. However, COD and temperature curves of the PWHT specimens were positioned at lower temperature compared with those of the as-welds. The more heat input causes to decrease the COD values at the constant temperature. It was verified through the recrystallization treatment that PWHT was attributed to move toward lower temperature region considerably due to the improved plastic deformation at the same applied COD value of 0.3mm and softening effect. In case of the weldment of S38 steel, cleavage fracture was observed at -105
unlike the structural steels, in which brittle fracture mode was generally shown at - 196
Bending Vibration Analysis of a Rotating Cantilever Beam Employing Finite Element Method
Park, Jeong-Hun ; Yu, Hong-Hui ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1826~1832
DOI : 10.22634/KSME-A.2000.24.7.1826
A modelling method for the bending vibration analysis of rotating cantilever beams employing finite element method is presented in this paper. Different from the conventional modelling method in wh ich only Cartesian deformation variables are used, a non-Cartesian deformation variable is introduced and approximated to derive the equations of motion. Numerical results obtained by using the presented modelling method are compared to those obtained by using other methods in the related literature, and the accuracy of the presented method is verified through the comparison study. The presented modelling method is superior to other previous methods in a sense that several advantages of the previous methods are incorporated into the presented method.
Modeling Creep Behavior and Life by Damage Mechanics
Sin, Chang-Hwan ; Jeong, Il-Seop ; Chae, Yeong-Seok ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1833~1840
DOI : 10.22634/KSME-A.2000.24.7.1833
Commercially pure copper is tested to obtain creep curves at 2500C. Constitutive relations adopting continuum damage mechanics concept is found to be appropriate to model the creep defor mation up to the tertiary stage. Microscopic observation by SEM reveals that creep condition induces cavities and microcracks subsequently. The constitutive equations along with evaluated creep parameters are implemented into finite element analysis code. The analysis reproduces creep curves under step loading as well as constant loading with reasonable accuracy. Distribution and evolution of damage under creep loading are numerically simulated for two different types of notched specimen. Predicted creep life agrees quite well with rupture test results. The influence of mesh size at notch tip on rupture time prediction is studied, and a degree of refinement is suggested for the specific notched specimens.
Fatigue Crack Growth Behavior of Ni-Cr-Mo Steel under Acid Fog Environment
Kim, Min-Geon ; Im, Yong-Ho ; Kim, Man-Gu ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1841~1846
DOI : 10.22634/KSME-A.2000.24.7.1841
To examine the effect of acid fog on the corrosion fatigue behavior in structural steel, fatigue tests under acid fog atmosphere were carried out in comparison with distilled water. The corrosive c omponents contained in acid fog pile up the corrosion products on crack face and show a crack branching and crack tip blunting. Therefore, due to these workings crack growth rate was reduced by decreasing the effective stress range in crack tip rather than under distilled water. Also the effect of sulfuric acid, which is the main component of acid fog, and testing speed on fatigue crack growth were examined. It was found that corrosion behavior was remarkably dependent upon pH and Hz rather than components of acid fog. According as pH and testing speed decrease below a specific value, crack growth was accelerated in comparison with distilled water. This reveals that due to liquid having strong acidity and slow speed of test the crack face dissolution was promoted, so crack closure was disturbed in the process of stress descent.
2 D Computer Simulation of Laser-Generated Ultrasonic Wave
Kim, Gyeong-Jo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1847~1853
DOI : 10.22634/KSME-A.2000.24.7.1847
A computer simulation technique for 2-dimensional laser generated ultrasonic waves was developed for visualization and investigation of ultrasonic propagation in solids. The technique is similar to a finite difference method (FDM) and a mass-particle model method, but uses a new nodal calculation method based on fundamental consideration of an elastic wave equation. By this method, the propagation behavior oflaser generated ultrasonic wave in thermoelastic and ablation mode is visualized and shows good agreement with previous experimental result or the numerical analysis result by Green function.
Design and Sensitivity Analysis of Input Shaping Filter in the Z-domain
Park, Un-Hwan ; Lee, Jae-Won ; Im, Byeong-Deok ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1854~1862
DOI : 10.22634/KSME-A.2000.24.7.1854
Input shaping method is to convolute input shaper, which is sequence of impulses, with reference input command not to excite the natural frequency of system. To reduce residual vibration for the ch ange of frequency, the number of impulses should be increased. Until now, amplitudes and time interval of those has been searched from the derivative of residual vibration. However, if time interval of impulses is fixed as the half of vibration period of system, input shaper H(z) in z-domain becomes (I-pz-1)n/K in which increasing n is the mean that robustness for change of parameter is improved. Also, design of many types of input shapers in z-domain is very easy because sensitivity curve is displayed with
100. In the z-domain, EI(Extra-Insensitive) input shaper could be designed without solving nonlinear simultaneous equations as design in continuous time domain. In addition to, the design possibility of input shaper for a damped system was shown.
A Study on the Dynamic Energy Release Rate of an Orthotropic Strip with a Half Infinite Crack and Large Anistropic Ratio
Baek, Un-Cheol ; Hwang, Jae-Seok ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1863~1870
DOI : 10.22634/KSME-A.2000.24.7.1863
When an impact stress is applied on the external boundary of double cantilever beam of orthotropic material which crack length is greater than specimen hight and anistropic ratio is very high, dyna mic energy release rate is derived, and the relationship between dynamic energy release rate and crack propagating velocity is studied. Dynamic energy release rate to static energy release rate is decreased with increasment of crack propagating velocity. The relationships between dynamic energy release rate and vertical strain have a similar pattern with those between static energy release rate and vertical strain. When normalized time(Cstla) is greater than or equal to 2, dynamic energy release rate approaches to a constant value.
Development of Tire Lateral Force Monitoring System Using SKFMEC
Kim, Jun-Yeong ; Heo, Geon-Su ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1871~1877
DOI : 10.22634/KSME-A.2000.24.7.1871
Longitudinal and lateral forces acting at tire are known to be closely related to the tractive ability, braking characteristics, handling stability and maneuverability of ground vehicles. However, it is not feasible in the operating vehicles to measure the tire forces directly because of high cost of sensors, limitations in sensor technology, interference with the tire rotation and harsh environment. In this paper, in order to develop tire force monitoring system, a new vehicle dynamics monitoring model is proposed including the roll motion. Based on the monitoring model, tire force monitoring system is designed to estimate the lateral tire force acting at each tire. A newly proposed SKFMEC (Scaled Kalman Filter with Model Emr Compensator) method is developed utilizing the conventional EKF (Extended Kalman Filter) method. Tire force estimation performance of the SKFMEC method is evaluated in the Matlab simulations where true tire force data is generated from a 14 DOF vehicle model with a combined-slip Magic Formula tire model.
Efficiency of a Symbolic Computation Method for the Real Time Simulation
Choe, Dae-Han ; Yu, Wan-Seok ;
Transactions of the Korean Society of Mechanical Engineers A, volume 24, issue 7, 2000, Pages 1878~1884
DOI : 10.22634/KSME-A.2000.24.7.1878
In multibody dynamic analysis, one of the most important problems is to reduce computation times for real time simulation. In this paper, a symbolic computation method is implemented and tested for each dynamic analysis step. Applying symbolic formulations to the vehicle dynamics program AutoDyn7, the effectiveness of the symbolic computation method is verified.