Go to the main menu
Skip to content
Go to bottom
REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
> Journal Vol & Issue
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 28, Issue 12 - Dec 2004
Volume 28, Issue 11 - Nov 2004
Volume 28, Issue 10 - Oct 2004
Volume 28, Issue 9 - Sep 2004
Volume 28, Issue 8 - Aug 2004
Volume 28, Issue 7 - Jul 2004
Volume 28, Issue 6 - Jun 2004
Volume 28, Issue 5 - May 2004
Volume 28, Issue 4 - Apr 2004
Volume 28, Issue 3 - Mar 2004
Volume 28, Issue 2 - Feb 2004
Volume 28, Issue 1 - Jan 2004
Selecting the target year
Active Compliance Control for the Rehabilitation Robot with Cable Driven Transmission
Kang, Sang-Hoon ; Chang, Pyung-Hun ; Park, Hyung-Soon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 28, issue 12, 2004, Pages 1823~1832
DOI : 10.3795/KSME-A.2004.28.12.1823
In this paper, we proposed a TDC based F/T sensorless active compliance control algorithm for a rehabilitation robot (KARES II). The preference of compliance of the disabled is presented by clinical testing at Korea National Rehabilitation Center with the disabled. The KARES II was designed to work 12 predefined tasks which are very essential for helping the disabled. Among the tasks, some contact tasks between the robot and the disabled exist. Therefore, TDC based F/T sensorless compliance control algorithm is developed for these tasks without additional cost. We verified the proposed algorithm with experiment. Also for the practical use, suitable compliance for contact tasks is chosen by clinical testing at Korea National Rehabilitation Center.
Robust Backstepping Control Using Time Delay Estimation
Kim, Seong-Tae ; Chang, Pyung-Hun ; Kang, Sang-Hoon ;
Transactions of the Korean Society of Mechanical Engineers A, volume 28, issue 12, 2004, Pages 1833~1844
DOI : 10.3795/KSME-A.2004.28.12.1833
A controller is proposed for the robust backstepping control of a class of nonlinear multiple-input multiple-output (MIMO) systems which can be converted to a strict feedback form. The proposed robust backstepping control scheme follows a systematic procedure for the design of control laws and uses time delay estimation (TDE) to estimate the uncertainties such as parameter variations, unknown disturbances, and unmodeled dynamics, etc. The proposed controller can be also applied to nonlinear MIMO systems with unmatched uncertainties. Stability analysis of the closed-loop system which contains the plant and the proposed controller is also studied and hereby a sufficient stability condition for the closed-loop system is proposed. The simulation results show that the control scheme works well with uncertainties and the proposed stability condition is valid. The controller is experimentally verified on a single-link flexible arm to show the effectiveness of the proposed scheme in the complicated systems with uncertainties.
Forward Kinematic Analysis of Casing Oscillator
Nam, Yun-Joo ; Park, Myeong-Kwan ;
Transactions of the Korean Society of Mechanical Engineers A, volume 28, issue 12, 2004, Pages 1845~1855
DOI : 10.3795/KSME-A.2004.28.12.1845
This paper presents the forward kinematics of the Casing Oscillator that is a construction machine. The Structure of the Casing Oscillator is similar to those of 4 degree-of-freedom mechanisms with a redundancy. With analytical (geometrical) methods, the solutions of the forward position kinematics problem are significantly found by both solving an 8
-order polynomial equation in one unknown variable and using one over-constraint geometrical equation which can be derived under the condition of a redundancy. The proposed forward kinematics has closed-form solutions and allows Auto-Balancing control of the moving platform in real time. Numerical examples are presented and the results are verified by an inverse kinematics analysis.
A Comparative Study of the Fatigue Behavior of SnAgCu and SnPb Solder Joints
Kim, Il-Ho ; Park, Tae-Sang ; Lee, Soon-Bok ;
Transactions of the Korean Society of Mechanical Engineers A, volume 28, issue 12, 2004, Pages 1856~1863
DOI : 10.3795/KSME-A.2004.28.12.1856
In the last 50 years, lead-contained solder materials have been the most popular interconnect materials used in the electronics industry. Recently, lead-free solders are about to replace lead-contained solders for preventing environmental pollutions. However, the reliability of lead-free solders is not yet satisfactory. Several researchers reported that lead-contained solders have a good fatigue property. The others published that the lead-free solders have a longer thermal fatigue life. In this paper, the reason for the contradictory results published on the estimation of fatigue life of lead-free solder is investigated. In the present study, fatigue behavior of 63Sn37Pb, and two types of lead-free solder joints were compared using pseudo-power cycling testing method, which provides more realistic load cycling than chamber cycling method does. Pseudo-power cycling test was performed in various temperature ranges to evaluating the shear strain effect. A nonlinear finite element model was used to simulate the thermally induced visco-plastic deformation of solder ball joint in BGA packages. It was found that lead-free solder joints have a good fatigue property in the small temperature range condition. That condition induce small strain amplitude. However in the large temperature range condition, lead-contained solder joints have a longer fatigue life.
Effect of Temperature and Water Immersion on Strength Properties of Spot Welded Zincked Steel Plates
Seo, Do-Won ; Choi, Jun-Yong ; Lim, Jae-Kyoo ;
Transactions of the Korean Society of Mechanical Engineers A, volume 28, issue 12, 2004, Pages 1864~1870
DOI : 10.3795/KSME-A.2004.28.12.1864
A spot welded structures have an influence on a diverse climatic situation, for instance temperature, humidity and precipitation. In addition factors of environmental pollution such as acid rain, that courses corrosion, have the tendency to increase. But spot welded structures strength is affected by humidity and environment temperature. Therefore, it is important to evaluate effect of temperature and water immersion on strength properties of spot welded part. In this study, the strength distribution of spot welded plates is evaluated the environmental temperature of zinc coated steel plates. Test is conducted with welded part immersed in distilled and synthetic sea water. Specimens are immersed into water for 10, 100, 500 and 1000 hours to evaluate the offsets of water immersion time on tensile-shear strength under the conditions of -40, 0, 20 and 5
. From this result, spot welded specimens with 5 mm clearance have lower tensile-shear strength in the distilled water or synthetic sea water than without clearance. And they have lower tensile-shear strength under -4
and over 5
Fabrication of Microneedle Array Using Inclined LIGA Process
Moon, Sang-Jun ; Lee, Seung-S. ;
Transactions of the Korean Society of Mechanical Engineers A, volume 28, issue 12, 2004, Pages 1871~1876
DOI : 10.3795/KSME-A.2004.28.12.1871
We demonstrate a novel fabrication technology for the microneedle array that can be used in the medical test field, which is transdermal drug delivery and blood analyte sampling. Previous researchers have used silicon-processed micromachining, a reactive ion etching, and molding techniques for the fabrication of microneedle array. However, these fabrication techniques have somewhat limitations apply to the microneedle array fabrication according to its application. Inclined LIGA process is suggested to overcome these problems. This process provides easier, sharper and longer out-of-plane microneedle array structure than conventional silicon-processed fabrication method did. Additionally, because of the advantage of the LIGA process based on mold fabrication for mass production, the polymer, PMMA(PolyMethylMethAcrylate), based microneedle array is useful as the mold base of nickel electroplating process; on the other hand, silicon-processed microneedle array is used in itself. In this research, we fabricate different types of out-of-plane microneedle array, which have different shape of tip, base and hole structure, using the inclined LIGA process. The fabricated microneedles have proper mechanical strength, height and sharpness to puncture human hand epidermis or dermis with less pain and without needle tip break during penetrating the skin.
A Study on FEM of the Bearing Girder in the Large Vessel Engine Structure
Park, Young-Joon ; Shim, Mun-Bo ; Kim, Hyun-Jun ; Suh, Myung-Won ;
Transactions of the Korean Society of Mechanical Engineers A, volume 28, issue 12, 2004, Pages 1877~1885
DOI : 10.3795/KSME-A.2004.28.12.1877
The purpose of this study is to show pressure distribution of the bearing girder in large vessel engine and to consider finite elements analysis using the pressure distribution. Various kinds of the exciting forces act on a bearing girder. And at the same time, it is necessary to consider the contact between a crankshaft and a bearing girder because a bearing girder supports a crankshaft. However it is to need the computer resource with much time if we apply the contact element to a complex solid model and perform a repeated analysis. Thus we have accomplished a contact analysis in the simplistic finite element model of the bearing girder. After that we take a pressure distribution, and apply this to actual finite element model and accomplish finite element analysis. The result of stresses and strains has been produced using superposition method. The concept of superposition method is to find the resultant deflection of several loads acting on a member as the sum of contributions of individual loads. The results were compared with measured results and were verified to be accurate. Resulting analyzed strain favorably coincides with measured strain. The experiment result justifies this paper method.
Motion Analysis of Scissors Type Bucket and Schemes for Improving Ore Scooping Performance
Park, Sang-Deok ; Kang, Min-Sung ; Won, Dae-Heui ; Kim, Tae-Ju ;
Transactions of the Korean Society of Mechanical Engineers A, volume 28, issue 12, 2004, Pages 1886~1896
DOI : 10.3795/KSME-A.2004.28.12.1886
Various types of buckets are used as unloading facilities for raw material at unloading wharfs. Scissors type buckets, among them, has been being used widely because of their short cycle time and structural simplicity. However, the scooping capacity, especially for hardened remainder ore, of some buckets are unsatisfactory because of poor design concept of the buckets. In this study, the effects of the design parameters on the scooping performance of the buckets are investigated under kinematic and dynamic analysis. Further, the schemes and design guidelines for designing new scissors type buckets are also presented to improve ore scooping capacity for hardened remainder ore.
A Study on the Near-Field Stresses and Displacement of a Stationary Interfacial Crack in Two Dissimilar Isotropic Bimaterials
Shin, Dong-Chul ; Hawong, Jai-Sug ; Nam, Jeong-Hwan ;
Transactions of the Korean Society of Mechanical Engineers A, volume 28, issue 12, 2004, Pages 1897~1905
DOI : 10.3795/KSME-A.2004.28.12.1897
In many part of machines or structures that made of bimaterial bonded with two dissimilar materials, most failures occur at their interface. Therefore, the accurate analysis of fracture characteristics and the evaluation of mechanical strength for interfacial crack are essential when we design those structures. In this research, stress and displacement components in the vicinity of stationary interfacial crack tip in the two dissimilar isotropic bimaterials are established. Hereafter, the stress components established in this research can be applied to the photoelastic hybrid method which can be used to analyze the fracture behavior of the two dissimilar isotropic bimaterials.
A New Experimental Technique for Calibration of Frictional Force in Atomic Force Microscopy
Choi, Duk-Hyun ; Hwang, Woon-Bong ; Yoon, Eui-Sung ;
Transactions of the Korean Society of Mechanical Engineers A, volume 28, issue 12, 2004, Pages 1906~1913
DOI : 10.3795/KSME-A.2004.28.12.1906
A new method has been proposed for the calibration of frictional forces in atomic force microscopy. Angle conversion factor is defined using the relationship between torsional angle and frictional signal. Once the factor is obtained from a cantilever, it can be applied to other cantilevers without additional experiments. Moment balance equations on the flat surface and top edge of a commercial step grating are used to obtain angle conversion factor. Proposed method is verified through another step grating test and frictional behavior of Mica.
Optimum Design of a Helicopter Tailrotor Driveshaft Using Flexible Matrix Composite
Shin, Eung-Soo ; Hong, Eul-Pyo ; Lee, Kee-Nyeong ; Kim, Ock-Hyun ;
Transactions of the Korean Society of Mechanical Engineers A, volume 28, issue 12, 2004, Pages 1914~1922
DOI : 10.3795/KSME-A.2004.28.12.1914
This paper provides a comprehensive study of optimum design of a helicopter tailrotor driveshaft made of the flexible matrix composites (FMCs). Since the driveshaft transmits power while subjected to large bending deformation due to aerodynamic loadings, the FMCs can be ideal for enhancing the drivetrain performance by absorbing the lateral deformation without shaft segmentation. However, the increased lateral flexibility and high internal damping of the FMCs may induce whirling instability at supercritical operating conditions. Thus, the purpose of optimization in this paper is to find a set of tailored FMC parameters that compromise between the lateral flexibility and the whirling stability while satisfying several criteria such as torsional buckling safety and the maximum shaft temperature at steadystate conditions. At first, the drivetrain was modeled based on the finite element method and the classical laminate theory with complex modulus approach. Then, an objective function was defined as a combination of an allowable bending deformation and external damping and a genetic algorithm was applied to search for an optimum set with respect to ply angles and stack sequences. Results show that an optimum laminate consists of two groups of layers: (i) one has ply angles well below 45
and the other far above 45
and (ii) the number of layers with low ply angles is much bigger than that with high ply angles. It is also found that a thick FMC shaft is desirable for both lateral flexibility and whirling stability. The genetic algorithm was effective in converging to several local optimums, whose laminates exhibit similar patterns as mentioned above.
Digital Microflow Controllers Using Fluidic Digital-to-Analog Converters with Binary-Weighted Flow Resistor Network
Yoon, Sang-Hee ; Cho, Young-Ho ;
Transactions of the Korean Society of Mechanical Engineers A, volume 28, issue 12, 2004, Pages 1923~1930
DOI : 10.3795/KSME-A.2004.28.12.1923
This paper presents digital microflow controllers(DMFC), where a fluidic digital-to-analog converter(DAC) is used to achieve high-linearity, fine-level flow control for applications to precision biomedical dosing systems. The fluidic DAC, composed of binary-weighted flow resistance, controls the flow-rate based on the ratio of the flow resistance to achieve high-precision flow-rate control. The binary-weighted flow resistance has been specified by a serial or a parallel connection of an identical flow resistor to improve the linearity of the flow-rate control, thereby making the flow-resistance ratio insensitive to the size uncertainty in flow resistors due to micromachining errors. We have designed and fabricated three different types of 4-digit DMFC: Prototype S and P are composed of the serial and the parallel combinations of an identical flow resistor, while Prototype V is based on the width-varied flow resistors. In the experimental study, we perform a static test for DMFC at the forward and backward flow conditions as well as a dynamic tests at pulsating flow conditions. The fabricated DMFC shows the nonlinearity of 5.0% and the flow-rate levels of 16(2
) for the digital control of 4(N) valves. Among the 4-digit DMFC fabricated with micromachining errors, Prototypes S and P show 27.2% and 27.6% of the flow-rate deviation measured from Prototype V, respectively; thus verifying that Prototypes S and P are less sensitive to the micromachining error than Prototype V.V.
Comparison Study on Structural Dynamic Modelings Employing Single Reference Frame
Kim, Jung-Min ; Yoo, Hong-Hee ;
Transactions of the Korean Society of Mechanical Engineers A, volume 28, issue 12, 2004, Pages 1931~1936
DOI : 10.3795/KSME-A.2004.28.12.1931
In this paper, modeling methods for the structural dynamic analysis employing single reference frame are presented and their modal and transient analysis results are compared. The geometric stiffening effects often occur when structures undergo large overall motion. These effects were considered in several structural previous modeling methods but the role of reference frame has never been scrutinized. In this study, modeling methods employing single reference frame are presented, and their numerical results are compared. The results show that discrepancy between the two modeling methods increases as the eccentricity of the structural system and the magnitude of the large overall motion increase.
Design, Fabrication and Test of Piezoelectric Actuator Using U-Shape PZT Strips and Lever Structure for Lateral Stroke Amplification
Transactions of the Korean Society of Mechanical Engineers A, volume 28, issue 12, 2004, Pages 1937~1941
DOI : 10.3795/KSME-A.2004.28.12.1937
We present lateral actuated piezoelectric actuator using U-shaped PZT strip and lever structure for the RF switch application. In the previous study of RF switch, they used horizontal contact switch fabricated by thin film metals. However, thin film metals could not generate large contact force due to low stiffness. In this work, we suggest lateral contact switch which makes large contact force by increasing stiffness. In addition, we use PZT actuator for the high force actuation. Generally actuator using thin film PZT moves to the vertical direction due to the neutral axis shift. Therefore we need lateral motion generation mechanism based on the thin film PZT actuator. In order to increase lateral motion of thin film PZT actuator, we use U-shaped PZT actuator using residual stress control. Also, thin film PZT actuator can generate very small lateral motion of 120
/V for d
mode, thus we suggest lever structure to increase stroke amplification. From the experimental study, fabricated PZT actuator shows maximum lateral displacement of 1
, and break down voltage of the thin film PZT actuator is above 16V,
Analysis of Novel Magnetic-Spring Actuators for Portable Units
Transactions of the Korean Society of Mechanical Engineers A, volume 28, issue 12, 2004, Pages 1942~1949
DOI : 10.3795/KSME-A.2004.28.12.1942
SLA(Scanned Linear Array) is a portable display unit for implementing next-generation virtual realities, utilizes a design that light generated by a line of LEDs is reflected from the rapidly oscillating mirror to generate a raster display. Reaction forces generated by the motions of the mirror and counter-balance mass cancel each other at the device base, reducing vibration. Metal leaf springs have been extensively applied in such portable units. Magnetic springs have been developed and adopted that can replace the metal spring and can avoid many disadvantages of metal springs. We model and analyze the dynamics of the structure with magnetic springs and present the simulation and experimental analysis results, which can be utilized for identifying and eliminating possible problem sources in removing shaking forces and moments, and oscillating the mirror at the required amplitude and frequency. Finally, we present the improved novel magnetic actuator model which can be applied in portable display units.
Evaluation of Effective In-Plane Elastic Properties by Imposing Periodic Displacement Boundary Conditions
Transactions of the Korean Society of Mechanical Engineers A, volume 28, issue 12, 2004, Pages 1950~1957
DOI : 10.3795/KSME-A.2004.28.12.1950
Analysis for structures composed of materials containing regularly spaced in-homogeneities is usually executed by using averaged material properties. In order to evaluate the effective properties, a unit cell is defined and loaded somehow, and its response is investigated. The imposed loading, however, should accord to the status of unit cells immersed in the macroscopic structure to secure the accuracy of the properties. In this study, mathematical description for the periodicity of the displacement field is derived and its direct implementation into FE models of unit cell is attempted. Conventional finite element code needs no modification, and only the boundary of unit cell should be constrained in a way that the periodicity is preserved. The proposed method is applicable to skew arrayed in-homogeneity problems. Homogenized in-plane elastic properties are evaluated for a few representative cases and the accuracy is examined.
Rapid Fabrication of Large-Sized Solid Shape using 3D Scanner and Variable Lamination Manufacturing : Case Study of Mount Rushmore Memorial
Transactions of the Korean Society of Mechanical Engineers A, volume 28, issue 12, 2004, Pages 1958~1967
DOI : 10.3795/KSME-A.2004.28.12.1958
This paper describes the method to rapidly fabricate the large-sized physical model with the envelope model size of more than 600 mm
600 mm using two type semi-automatic VLM-ST processes in connection with the reverse engineering technology. The fabrication procedure of the large-sized solid shape is as follows: (1) Generation of STL data from 3D scan data using 3D scanner, (2) generation of shell-type STL data by Boolean operation, (3) division of shell-type STL data into several pieces by solid splitting, (4) generation of USL data for each piece with VLM-Slicer, (5) fabrication of each piece by cutting and stacking according to USL data using VLM-ST apparatus, (6) completion of a shell-type prototype by zigzag stacking and assembly for each piece, (7) completion of a 3D solid shape by foam backing, (8) surface finish of a completed 3D solid shape by coating and sanding. In order to examine the applicability of the proposed method, the miniature of the Mount Rushmore Memorial has been fabricated. The envelope model size of the miniature of the Mount Rushmore Memorial is 1,453 mm
853 mm in size. From the result of the fabricated miniature of the Mount Rushmore Memorial, it has been shown that the method to fabricate the large object using two type semi-automatic VLM-ST processes in connection with the reverse engineering technology are very fast and efficient.
Evaluation of Mechanical Properties with Thermal Aging in CF8M/SA508 Welds
Transactions of the Korean Society of Mechanical Engineers A, volume 28, issue 12, 2004, Pages 1968~1973
DOI : 10.3795/KSME-A.2004.28.12.1968
Structural degradations are often experienced on the components of nuclear power plants in reactor pressure vessels (RPV) and steam generators (SG) when these components are exposed to high temperature and high pressure for a long period of time. Such conditions result in the change of microstructures and of mechanical properties of materials, which requires an evaluation of the safeguards related to structural integrity. In a primary reactor cooling system (RCS), a dissimilar weld zone exists between cast stainless steel (CF8M) in a pipe and low-alloy steel (SA508 cl.3) in a nozzle. Thermal aging is observed in CF8M as the RCS is exposed for a long period of time under the operating temperature between 290 and 33
. Under the same conditions, it is well known that degradation is not observed in low alloy steel. An investigation of the effect of thermal aging on the various mechanical properties of the dissimilar weld zone is required. The purpose of the present investigation is to find the effect of thermal aging on the dissimilar weld zone. The specimens are prepared by an artificially accelerated aging technique maintained for various times at 43
, respectively. Then, The various mechanical test for the dissimilar welds are performed.
Numerical Analysis of Impact Force Transfer Characteristics of Court Sport Shoes to Surface Condition
Transactions of the Korean Society of Mechanical Engineers A, volume 28, issue 12, 2004, Pages 1974~1981
DOI : 10.3795/KSME-A.2004.28.12.1974
This paper is concerned with the numerical investigation of the transfer characteristics of the landing impact force exerted on court sport shoes to the sport surface condition. The reaction force occurred by the impact between court sport shoes and sport surface is absorbed by shoes to some extent, but the remaining impact force is to transfer the human body from the sole of a foot. We consider four surface conditions, asphalt, urethane, clay and wood court surfaces. For the dynamic response analysis, we construct a coupled leg-shoes FEM model and create the multi-layered composite surface model. The numerical simulations are performed by an explicit nonlinear finite element method. Through the numerical experiments, we examine the transfer characteristics of the landing impact force to the surface condition.
Measurement of Principal Stress Direction by Photoelastic Phase Shifting Method
Transactions of the Korean Society of Mechanical Engineers A, volume 28, issue 12, 2004, Pages 1982~1989
DOI : 10.3795/KSME-A.2004.28.12.1982
In photoelasticity, the directions of principal stresses are given by isoclinic fringe patterns. In this study, photoelastic theory is represented by Jones calculus and the photoelastic 8-step phase shifting method is described. A feasibility study using computer simulation is done to get isoclinics from photoelastic fringes of a circular disk under diametral compression. Fringe patterns of the disk are generated from the stress-optic law. The magnitudes of isoclinics obtained from the fringe patterns of computer simulation and experiment are compared with those of theory. The results are close between them. Then, the 8-step phase shifting method is applied to get distributions of isoclinics along the specified lines of a cuved beam plate under tensile load. Experimental results obtained from the phase shifting method were compared with those of finite element analysis (ANSYS). It is confirmed that measurement of isoclinic distributions is possible by use of photoelasitc phase shifting method.
Mechanically Modulated Nonlinear Digital Microactuators for Purified Digital Stroke and Nano-Precision Actuation
Transactions of the Korean Society of Mechanical Engineers A, volume 28, issue 12, 2004, Pages 1990~1996
DOI : 10.3795/KSME-A.2004.28.12.1990
This paper presents a nonlinearly modulated digital actuator (NMDA) for producing nano-precision digital stroke. The NMDA, composed of a digital microactuator and a nonlinear micromechanical modulator, purifies the stroke of the digital actuator in order to generate the high-precision displacement output required for nano-positioning devices. The function and concept of the nonlinear micromechanical modulator are equivalent to those of the nonlinear electrical limiters. The linear and nonlinear modulators, having an identical input and output strokes of 15.2
, are designed, fabricated and tested, respectively. The linear and nonlinear modulators are linked to identical digital actuators in order to compare the characteristics of the linearly modulated microactuator (LMDA) and NMDA. In addition, an identical linear modulator is attached to the output ports of LMDA and NMDA. The NMDA shows the repeatability of 12.3
2.9nm, superior to that of 27.8
2.9nm achieved by LMDA. When the identical linear modulator is connected to LMDA and NMDA, the final modulated output from NMDA shows the repeatability of 10.3
7.2nm, superior to that of 15.7
7.7nm from LMDA. We experimentally verify the displacement purifying capability of the nonlinear mechanical modulator, applicable to nano-precision positioning devices and systems.
Nanomechanical Protein Detectors Using Electrothermal Nano-gap Actuators
Transactions of the Korean Society of Mechanical Engineers A, volume 28, issue 12, 2004, Pages 1997~2003
DOI : 10.3795/KSME-A.2004.28.12.1997
This paper presents a new method and an associated device, capable of detecting protein presence and size from the shift of the mechanical stiffness changing points due to the presence and size of proteins in a nano-gap actuator. Compared to the conventional resonant detection method, the present nanomechanical stiffness detection method shows higher precision for protein detection. The present method also offers simple and inexpensive protein detection devices by removing labeling process and optical components. We design and fabricate the nanomechanical protein detector using an electrothermal actuator with a nano-gap. In the experimental study, we measure the stiffness changing points and their coordinate shift from the devices with and without target proteins. The fabricated device detects the protein presence and the protein size of 14.0
7.4nm based on the coordinate shift of stiffness changing points. We experimentally verify the protein presence and size detection capability of the nanomechanical protein detector for applications to high-precision biomolecule detection.
Variation of Eddy Current Signal According to the Defect Shape, Defect Depth and Radial Load in CFRP Tube
Transactions of the Korean Society of Mechanical Engineers A, volume 28, issue 12, 2004, Pages 2004~2011
DOI : 10.3795/KSME-A.2004.28.12.2004
The applicability of the ultrasonic C-scan inspection is restricted due to the deterioration of mechanical properties of specimen during the test. Therefore, the aim of this research is applied to Eddy Current (EC) test substitute for the C-scan inspection in CFRP tube containing defects. This research is to evaluate the EC signals for the inspection of CFRP tube containing various circular hole defects (20% to 100% depth to the specimen thickness) using the unloading specimen and radial loading specimen. This study was considered the following points; 1) Analysis of EC signals for the inspection of saw-cut defect and circular hole defect, 2) The evaluation of defect depths and EC signals relationship. 3) Variation of EC signal owing to the radial load. In conclusions, the high frequency such as 300∼500 kHz made it possible to the inspection of 40% to 100% defects. Particularly, in case of 20% defect, the EC signal was not detected due to the noise of micro-crack and delamination. While the depth of the hole defects were decreasing, the difference of the phase angle between unloading specimen and radial loading specimen was gradually increasing.
Vibration Analysis for the In-plane Motions of a Semi-Circular Pipe Conveying Fluid Considering the Geometric Nonlinearity
Transactions of the Korean Society of Mechanical Engineers A, volume 28, issue 12, 2004, Pages 2012~2018
DOI : 10.3795/KSME-A.2004.28.12.2012
The vibration of a semi-circular pipe conveying fluid is studied when the pipe is clamped at both ends. To consider the geometric nonlinearity, this study adopts the Lagrange strain theory for large deformation and the extensible dynamics based on the Euler-Bernoulli beam theory for slenderness assumption. By using the Hamilton principle, the non-linear partial differential equations are derived for the in-plane motions of the pipe, considering the fluid inertia forces as a kind of non-conservative forces. The linear and non-linear terms in the governing equations are compared with those in the previous study, and some significant differences are discussed. To investigate the dynamic characteristics of the system, the discretized equations of motion are derived from the Galerkin method. The natural frequencies varying with the flow velocity are computed from the two cases, which one is the linear problem and the other is the linearized problem in the neighborhood of the equilibrium position. Finally, the time responses at various flow velocities are directly computed by using the generalized-
method. From these results, we should consider the geometric nonlinearity to analyze dynamics of a semi-circular pipe conveying fluid more precisely.
The Least-Squares Meshfree Method for the Analysis of Rigid-Plastic Deformation
Transactions of the Korean Society of Mechanical Engineers A, volume 28, issue 12, 2004, Pages 2019~2031
DOI : 10.3795/KSME-A.2004.28.12.2019
The least-squares formulation for rigid-plasticity based on J
-flow rule and infinitesimal theory and its meshfree implementation using moving least-squares approximation are proposed. In the least-squares formulation the squared residuals of the constitutive and equilibrium equations are minimized. Those residuals are represented in a form of first-order differential system using the velocity and stress components as independent variables. For the enforcement of the boundary and frictional contact conditions, penalty scheme is employed. Also the reshaping of nodal supports is introduced to avoid the difficulties due to the severe local deformation near the contact interface. The proposed least-squares meshfree method does not require any structure of extrinsic cells during the whole process of analysis. Through some numerical examples of metal forming processes, the validity and effectiveness of the method are investigated.