bluuebunny/crossref_metadata_2025 huggingface dataset:
Model-Based Approach for Quantitative Evaluation of Spasticity
Authors: Hase Kazunori , Adachi Norimasa , Obinata Goro , Eom Gwang Moon , Kim Chul Seung , Kong Se Jin
Published: March 2009

In the present clinical fields, medical doctors mainly use Modified Ashworth Scale (MAS)
to evaluate spasticity. However, MAS is manual and qualitative method and results depend on doctors.
The purpose of this paper is to propose a method to quantitatively evaluate spasticity using a
neuro-musculo-skeletal model. The proposed model consisted of the muscular activation model,
variable viscoelastic model of the muscles, musculoskeletal model, muscle spindle model and alpha
motoneuron model. This model could represent spasticity patient’s knee pendulum well. A parameter
related with sensitivity of the muscle spindle was a factor to evaluate spasticity quantitatively.
Detecting and Tracking Changes of Morphologies and Mechanical Characteristics in the Lumbar Vertebrae of OVX Rats Using RP Technique and Micro-FE Method
Authors: Woo Dae Gon , Kim Han Sung , Ko Chang Yong , Lee Beob Yi , Tack Gye Rae , Kim Young Ho
Published: March 2009

In the present study, changes of morphologies and mechanical characteristics in the lumbar
vertebrae of the ovariectomised (OVX) rats were investigated and analyzed by Finite Element (FE)
and Rapid-Prototyped (RP) models based on micro-computed tomography (micro-CT). In previous
researches, there were many studies about morphology such as bone mineral density and trabecular
microstructure. However, detecting and tracking local changes were few in the trabecular and cortical
bone of the lumbar vertebrae for the OVX rats. Experimental and simulated studies were used to
investigate mechanical characteristics of the lumbar vertebral bones for the OVX rats. Three
dimensional (3D) geometries of the models (RP and FE models), generated from in-vivo micro-CT
scan data, were obtained from the 4th lumbar of the OVX rats. Three specimens (whole vertebral,
trabecular and cortical bone models) were generated and analyzed in the simulated compression tests.
For further verification, the experimental compression test for RP models ‘instead of real bone
specimens’ was performed to indirectly validate the results of the simulated compression test for the
FE models. The results were similar to those of the compression test simulated by micro-FE analysis.
The present study showed the efficiency of the combined method (FE and RP techniques based on
in-vivo micro-CT) as a nondestructive evaluation.
Application of Modified Grid-Based Approach for Auto Mesh Generation of IT-Related Products
Authors: Park Young Jae , Kim Byung Sun , Ko Han Ok , Chang Yoon Suk , Choi Jae Boong , Kim Young Jin , Lee Joon Seong , Kim C.S.
Published: March 2009

A seamless analysis of IT-related products, such as cellular phone, LCD monitor and note
PC etc., which are thin and complex geometry is one of great concerns in product design. However,
there is a considerable amount of gap between the industrial application and fundamental academic
studies due to a time consuming detailed mesh generation. In order to settle the bottleneck, an auto
mesh generation program based on a modified grid-based approach is proposed in this paper. At first,
base mesh and skin mesh were generated using informations on entities which extracted from an
IGES (Initial Graphics Exchange Specification) file. Secondly, a provisional core mesh with a rough
boundary geometry was constructed by superimposing the skin mesh into the base mesh generated
from CAD model. And then, positions of boundary nodes were redistributed to delineate exact
geometry of the provisional mesh. Finally, good qualified meshes were constructed by moving the
positions of the nodes and splitting elements along boundary edges. In conclusion, it is anticipated
that the developed program can be used as a promising pre-processor for static or dynamic analysis of
various IT-related products.
Proper Light Array Design for the Optimum Nondestructive Evaluation of Fruit’s Internal Quality
Authors: Kang Suk Won , Lee Kang Jin , Son Jae Ryong
Published: March 2009

This study was conducted to develop an accurate quality evaluation system based on optimized factors such as light source array and light power, which are used in non-destructive fruit sorter to obtain the internal quality information of fruits using the near infrared transmittance spectra. It is necessary to provide the proper design guide for the light source part in the existing non-destructive fruit sorters for apples and pears, and to measure the real-time near infrared transmittance spectrum without the leakage of light. The near infrared transmittance spectrum detection system was developed with the light source part which has the power-controllable 12 halogen lamps (100W/12V) with gold coating, light detection part, and transfer line. By using the accurate control of the voltage and current (maximum power is 1.2kW) in light power control part, it is concluded that the minimum power for the internal quality evaluation of apples and pears was over 0.5 kW. To prevent the leakage of light, the array of light source was rearranged and tested. Without changing the tray structure, it is concluded that the leakage of light can be prevented by the proper array of light source and power. For the irradiation for the moving apples and pears, 2 upper lamps and 4 lower lamps combination did not have leakage of light and the correlation coefficient of this combination shows the 0.90 for apples and 0.96 for pears.
Gas Electron Multipliers for Potential Applications to Digital Radiography
Authors: Cho Hyo Sung , Choi Sung Il , Kim Hok Yung , Lee Bong Soo , Kim Sin
Published: March 2009

The gas electron multiplier (GEM), placed in the drift volume of a conventional gas
detector, is a conceptually simple device for producing a large gas gain by concentrating the drift
electric field over a very short distance to the point that electron avalanching occurs. This device
consists of a thin insulating foil of several tens of μm in thickness, covered on each side with a thin
metal layer, with tiny holes, usually 100 μm or less in diameter, and with a spacing of 100-200 μm
through the entire foil, perforated by using chemical etching or high-powered laser beam technique. In
this study, we have investigated its operating properties with various experimental conditions and
demonstrated the possibility of using this device as a digital X-ray imaging sensor, by acquiring X-ray
images based upon the scintillation lights of the GEM with a standard CCD camera.
Asymmetrical Dual Charge EPCM for Delamination Monitoring of CFRP Laminate
Authors: Ueda Masahito , Todoroki Akira
Published: March 2009

CFRP laminate is sensitive to impacts. Even a low impact creates delamination, bringing deterioration of the structural reliability. Monitoring for delamination is, therefore, indispensable to maintain the reliability of a CFRP structure. In this study, asymmetrical dual charge electric potential change method was introduced to estimate a delamination in the CFRP laminate. Delaminations were estimated using response surfaces as solver of the inverse problem. Learning data of response surfaces were calculated by FEM analyses. Actual delaminations in the CFRP laminate were successfully identified.
Design and Characterization of Capacitive Micromachined Ultrasonic Transducer
Authors: Ahn Bong Young , Kim Ki Bok , Park Hae Won , Kim Young Joo , Kwak Yong Seok
Published: March 2009

As cMUTs (capacitive Micromachined Ultrasonic Transducer) offer numerous advantages
over traditional transducers in terms of efficiency, bandwidth, and cost, they are expected to replace
piezoelectric transducers in many applications. In particular, 2D-array cMUTs have aroused great
interest in the medical engineering society because of their ability to materialize a true volumetric
ultrasonic image. In this study, single element cMUTs with 32 x 32 and 64 x 64 cells were
successfully fabricated. The diameter and thickness of the membrane are 35 and 1000 nm,
respectively, with a sacrificial layer thickness of 600 nm. The electric characteristics of the fabricated
cMUT were measured. Tests on the efficiencies of the cMUT in terms of wave generation and in
terms of detection according to the bias and pulse voltage were performed in an air atmosphere.
Effect of SiO2 Cap Layer on Thermal Stability of Nickel and Nickel-Cobalt Silicide
Authors: Han Kil Jin , Cho Yu Jeong , Oh Soon Young , Kim Yong Jin , Lee Won Jae , Lee Hi Deok , Kim Yeong Cheul
Published: March 2009

We investigated the effect of SiOcap layer on the thermal stability of nickel and nickel-cobalt silicide by measuring its sheet resistance. The stability of nickel silicide was deteriorated as a function of annealing temperature, while that of nickel-cobalt silicide was not. In case of both silicides, the SiOcap layer improved the stability. Tensile stress from the difference of thermal expansion coefficients between SiO2 and nickel silicide may suppress the agglomeration of nickel silicide.
Residual Stress Measurement and Evaluation on Ceramics with X-Ray and Indentation Method
Authors: Tokuda Tarou , Wang Rong Gang , Katayama Gonojo , Kido Mitsuo
Published: March 2009

In this report, the indentation method of measurement for residual stress in structural ceramics is discussed. The residual stresses in Al2O3, Si3N4 and ZrO2 ceramics were evaluated with the indentation method. The value obtained by the indentation method was examined as a function of the microstructure, using Al2O3 ceramics differing in microstructure (grain size and aspect ratio). The residual stress values in Al2O3 and Si3N4 obtained by the indentation method at 98 N agreed well with the values obtained by the X-ray method. The residual stress value in ZrO2 obtained by the indentation method was close to the value obtained by the X-ray method, when the indentation load was 294 N. For estimating the residual stress in ZrO2 with the indentation method, the influence of the phase transformation induced by the indentation is added to the original residual stress, when the indentation is small. The value obtained by indentation method differed with the aspect ratio of the grains in Al2O3. It was thought that the origin of the variation was the difference in crack propagation resistance in different materials
A Study of the Quantitative Nondestructive Evaluation Using the Cross Type Magnetic Source and the Magnetic Camera
Authors: Lee Jin Yi , Hwang Ji Seong
Published: March 2009

The magnetic camera using magnetic lens is proposed to satisfy the demands such as obtaining the distribution of the magnetic flux leakage (DMFL) on the high lift-off, and improving sensitivity. However, DMFL is strongly affected by the magnetization direction. Therefore, the DMFL has low intensity when the crack is not perpendicular to the magnetizing direction. Also, quantitative nondestructive evaluation would be difficult. This paper proposes an improved magnetization method to evaluate a crack quantitatively, regardless of the crack direction. The secondary magnetic source, which is perpendicular to the primary magnetic source, is introduced in the scan type magnetic camera. The intensity of two values of ∂B/∂x (1st differential to the magnetization direction) of the DMFL can be used to evaluate the crack volume. The experimental and the numerical analysis results are considered to verify this phenomenon.
Comparisons of Precision Measurement Methods for Metallic Resistivities
Authors: Kang Jeon Hong , Yu Kwang Min , Kim Han Jun , Ryu Je Cheon , Han Sang Ok
Published: March 2009

As widely-used methods to measure metallic resistivities, Four-terminal method, van der Pauw method, Four-Point Probe(FPP) method and eddy current method were compared and analysed to find the method with lowest uncertainty and accurate method for applying nondestructively to industry. STS 316, non-magnetic metal is used as sample for the four methods. Conductivity ratios by the four-terminal method and van der Pauw method had the lowest uncertainty of 0.25 % and the ratios by the FPP method had measurement uncertainty of 0.45 % when probe spacing was more than two times of sample thickness and dc 10 A is applied. Also, the ratio values by the eddy current method had 1 % or more difference from the four-terminal or van der Pauw method and measurement uncertainty was obtained as 0.93 %. From the results, former two methods had the lowest uncertainty but are destructive methods so that those are difficult to apply to the field of industry. The FPP method is an accurate and nondestructive measurement method so that it can be used in the field. The eddy current method is one of nondestructive method but it has the highest uncertainty and low accuracy.
Uncertainty Improvements of Metallic Resistivity Measurements by the Four-Point Probe Method
Authors: Yu Kwang Min , Kang Jeon Hong , Kim Han Jun , Han Kwon Soo , Ryu Je Cheon
Published: March 2009

Besides well-known destructive methods for material degradation, the electrical resistivity method has been used as one of nondestructive evaluation methods because of easy measurement. To use the method, however, careful geometrical corrections and thickness measurements are required. The high current probe assembly and accurate thickness measurement device were developed to improve overall measurement uncertainty. If dual configuration Four-Point Probe method with the developed devices is used, overall measurement uncertainty of electrical resistivity could be reduced to 0.44 % at 95 % confidence level. Proper selection of the probe spacing matched with sample thickness is very important to determine accurate electrical resistivity. When sample thickness is less than probe spacing, it is expected that dual configuration Four-Point Probe technique can be used in nondestructive evaluation of plant equipment materials.
Consideration of Uncertainty in Diagnosis for Railway Arrester
Authors: Kim Hyung Chul , Han Moon Seob , Park Hyun June , Jang Dong Uk , Kil Gyung Suk , Nair Nirmal Kumar
Published: March 2009

This paper presents a method for diagnosis of railway arrester considering uncertainty. Arresters, a protective device that prevents damage due to transient voltages, deteriorate due to the absorption of moisture, repetitive operation during over-voltages and manufacturing defects. Various diagnostic techniques are available for monitoring deterioration of arresters. The technique based on the amplitude of leakage current measures the root mean square or peak values of leakage current components. After measuring the total leakage current, harmonics of leakage current components are analyzed by using a microprocessor based device. The level of leakage current is indicative of the arrester conditions. Harmonics of leakage current components occur due to nonlinear characteristics of railway arrester. Since leakage current contains uncertainty characteristics of power source, the probability density functions of leakage current components can be obtained for ZnO arrester. This paper presents a probabilistic approximation method for the harmonic currents analysis in diagnosis for railway arresters. Mean and variance of harmonic currents in railway system are obtained based on leakage current components. These statistical measures can be helpful to reduce the diagnostic error for railway arrester.
Reliability Analysis of a Robot Manipulator Operation Employing Single Monte-Carlo Simulation
Authors: Choi Dong Hwan , Yoo Hong Hee
Published: March 2009

The operation error of a robot that occurs inevitably due to the manufacturing tolerance needs to be controlled within a certain range to achieve proper performance of the robot system. The reduction of manufacturing tolerance, however, increases the manufacturing cost in return. Therefore, design engineers try to solve the problem of maximizing the tolerance to reduce the manufacturing cost while minimizing the operation error to satisfy the performance requirement. In the present study, a revolute joint model considering uncertainties due to joint clearance is employed to perform a reliability analysis of the robot manipulator operation. The reliability analysis procedure employs single Monte-Carlo simulation and a statistical relation between the tolerance and the operation error. Significant reduction of computing time can be achieved with the proposed method. The present method is especially effective if sensitivity information is hard to be obtained for the analysis.
Probabilistic Reliability Design of Satellite Structures under Launching Environments By Metamodel
Authors: Park Jung Sun , Im Jong Bin , Ro Youg Hee , Lee Soo Yong
Published: March 2009

This paper is focused on a probabilistic design of the honeycomb structure which is a
constituent unit of satellite. The design is considering launching and space environments by kriging
metamodel. The proposed methodology using the kriging metamodel is conducted by stochastic
step-moving method (SSMM) as the criterion of a sequential approximate optimization to satisfy the
global optimum value based on the local optimum value. Also, Design of Experiments (DOE) is used
to reduce computation costs. The honeycomb structure is analyzed for reliability. For the optimal
design, constraints are taken for natural frequency and several stresses that should be considered on
the satellite platform in launching situations. Thermal effects of space environments and wrinkling
are also considered since a structural sandwich is often poor at carrying in-plane compressive loads
and may be inflicted with instability and thermal effect.
A Study on the Surface Characteristics with the Vibration Factor in the Micro-Machine
Authors: Kin Jong Min , Hong Min Sung , Kim Bong Suk , Lee Soo Hun
Published: March 2009

In conventional machining, cutting conditions such as cutting speed, feed rate, and depth of the cut have great influence on the surface roughness. In micro machining, however, the surface shape is affected by not only the machining parameters mentioned earlier but also tool stiffness, system stability, and workpiece properties caused by the miniatured structure and cutting tool. Especially, in a micro-machine system, the difference between the cutting forces in the recursive cuts introduces the vibration easily. A high spindle causes instability of the system, increases the temperature in the cutting process, and also changes the tool’s shape. This study introduces a method to predict the surface shape of the workpiece based on the machining conditions in micro milling. The micro-milled surfaces in different machining conditions are predicted by a computer simulation including the vibration model and the simulated results show good agreement with the experimental results.
Robust Measurement of Damping Ratios of a Railway Contact Wire Using Wavelet Transforms
Authors: Cho Yong Hyeon , Lee Jang Moo , Park Sung Yong , Lee Eung Shin
Published: March 2009

The aim of this paper is to propose a robust method for extracting damping ratios of a
railway contact wire using a continuous wavelet transform (CWT). It is hard to measure the damping
ratios of the contact wire because the contact wire has close natural modes in a low frequency range
and the dynamic signals of the contact wire gathered in the field are easily corrupted by extraneous
noises. The proper choice of the wavelet parameters to decouple the close modes is required in order
to obtain accurate damping ratios for the railway contact wire. In this paper, we investigated CWT
error terms and derived a relation between a frequency resolution and complex Morlet wavelet
parameters. In order to show the accuracy of the proposed method, we extracted damping ratios for
the simulated pure and noisy signals which have close natural modes. According to the results, the
proposed method can provide the damping ratios well agreed with true ones even for the noisy data.
Finally, we applied the proposed method to the contact wire of a conventional railway line in Korea in
order to verify the applicability in the field. The damping ratios extracted from the real data were in
the range from 0.01 to 0.04.
Preparation and Characterization of Nanosized Al2O3 Particles Synthesized by the thermal MOCVD and Plasma CVD
Authors: Kim Hee Joon , Oh Se Woong , Noda Hiroyuki , Chang Ho Jung , Kim Lae Hyun
Published: March 2009

In this paper, nano-sized Al2O3 powders are synthesized by a thermal MOCVD (Metal Organic Chemical Vapor Deposition) combined with plasma. The effect of reaction temperature on the characteristics of the synthesized Al2O3 powders is investigated. The experimental results demonstrate that while the temperature is increased from 200oC to 1000oC, the mean diameter of Al2O3 powders reaches from 400nm to 10nm. Hence, the increment of temperature can promote the synthesis of fine Al2O3 particle. Furthermore, the powder morphologies and crystallite size are also examined by the transmission electron microscopy (TEM) and XRD. Based on TEM observation, it is found that the particles are sphere shape. The XRD analysis shows that the particles are typical γ-Al2O3 crystalline phase over 400oC. Lastly, the effect of plasma on the characteristic of Al2O3 synthesized by thermal MOCVD is also considered.
(110) Silicon Hard Master Fabrication Using Wet Etching for Multi-Mode Planar Optical Splitter
Authors: Jung Yu Min , Kim Yeong Cheul , Seo Hwa Il
Published: March 2009

To fabricate a (110) silicon hard master, we used anisotropic wet etching. The etching
chemical for the silicon wafer was a TMAH 25% solution. We fabricated a 1x4 multimode planar
waveguide splitter using the silicon hard master. Organic-inorganic hybrid materials were used as
core and cladding layers of the planar waveguide splitter. The 15 μm-thick under-cladding layer
was coated on a silicon substrate and baked. After the core layer was coated on the under-cladding
layer, the core pattern was formed by using a hot embossing process at 100 °C and 1-3 kg/cm2. The
propagation loss of the planar waveguide was 0.4 dB/cm and the insertion loss of the 1x4 planar
waveguide splitter was 11.2 dB at the total splitter length of 3.5 cm.
Development of Smart Stress Memory Sensor Using AE Kaiser Effect
Authors: Nambu Shoichi , Tsunawaki Yoshihiko , Enoki Manabu
Published: March 2009

Reliability of structures is an important task to ensure the ease and safety of our life, and
further development of non-destructive evaluation for structures such as bridges and tunnels is
required. Some fatigue sensors that consist of sacrificed specimen have been developed to evaluate
the fatigue damage of structures such as fatigue cyclic number and residual lifetime. However, these
fatigue sensors can be used only when the applied stress amplitude is known. We tried to develop a
new smart stress memory patch that measured both maximum stress and number of fatigue cycles
simultaneously using Kaiser effect of Acoustic Emission (AE) and crack length. In this study, the
characteristics of the smart patch was evaluated. Pure copper was used for this sensor because its good
corrosion resistance, stable crack propagation and detectability of AE near yield point. Fatigue test
was performed under the constant stress amplitude to evaluate the crack propagation behavior using
the relationship between stress intensity factor and crack propagation rate. The obtained curve
between crack length and number of fatigue cycles by these crack propagation behavior was in good
agreement with experimental results. AE measurement after some fatigue tests was performed and
AE was detected at the applied fatigue stress. These results demonstrated that number of fatigue
cycles and the maximum stress could be measured by this fatigue sensor.
Integrity Assessment for Beam-Like Structures by Continuous Wavelet Transform
Authors: Kim Han Sang , Yi Jin Hak , Koo Ki Young , Yun Chung Bang , Huh Yong Hak
Published: March 2009

The integrity assessment method for beam-like structures using continuous wavelet
transform (CWT) is proposed. CWT is applied to the response acceleration of a structure to
decompose the response acceleration correspond to each scale. The curvature difference of the
normalized energy for each member caused by structural degradation clearly indicated the location
of damaged members in the structure. It is shown that the proposed method can identify damaged
members without performing complicated dynamic analyses which usually require significant effort
and time.
The Effect of Joint Conditions on the Longitudinal and Flexural Wave Velocities of a Rock Mass
Authors: Cha Min Su , Sim Young Jong , Cho Gye Chun , Lee Sung Won
Published: March 2009

The behavior of a jointed rock is different from that of an intact rock, and the characteristics
of elastic wave propagation in a jointed rock are different from those of an intact rock. In this study, a
rock resonant column testing device is designed to measure the longitudinal and flexural wave
velocities of jointed rocks under different states of stress. A column of more than 12 rock discs is
stacked on a steel base, which acts as a free-fixed system. This configuration ensures that waves
propagate under an equivalent continuum condition, thereby rendering a constant and unique velocity.
The effect of joint conditions on the wave velocities is investigated through rock resonant column
testings. The results show that velocities are sensitive to the state of stress and increase nonlinearly
with stress. The velocities are also affected by joint conditions such as roughness, spacing, and filling.
The results are useful for rock mass classification based on near-surface geophysical characterization.
Examination of Accuracy of the Singular Stress Field Near a Crack-Tip by Digital Image Correlation
Authors: Machida Kenji , Suzuki Yoshimasa
Published: March 2009

Displacements obtained experimentally normally are including errors that make it impossible to extract stresses strains with high accuracy using the raw displacement data. In the infinitesimal deformation within the elastic region of a steel or an aluminum alloy, the quantity of displacement is less than 1 pixel, and analysis accuracy deteriorates. We have developed a system which employs the 2-D intelligent hybrid method and can analyze the displacement more exactly in the sub-pixel field. By using the Newton-Raphson method in conjunction with 2nd order deformation gradients, it is demonstrated that this method can accurately extract stress intensity factors from a set of measured displacements.
Improvement of the Impact-Echo Method for the Higher Reliability in the Structural Integrity Assessment
Authors: Cho Mi Ra , Kim Ki Bong , Joh Sung Ho , Kang Tae Ho
Published: March 2009

The impact-echo method, which is to evaluate the integrity of concrete and masonry
structures nondestructively, is an excellent method in practical applications, and provides a high
quality of structural integrity assessment. However, in the case of multi-layered systems in which each
layer has different stiffness, the impact-echo method may lack reliability in thickness evaluation,
which demands improvement of the impact-echo method. This study was first dedicated to the
understanding of stress-wave propagation in the impact-echo test, and secondly, the reliability of the
impact-echo method was investigated through the numerical simulation of the impact-echo test. The
investigation included the research on influencing factors such as stiffness contrast between layers
and receiver location. Finally, the research in this paper led to the development of the
phase-difference response (PDR) method, based on the frequency response between two receivers
deployed in a line with an impact source.
Effects of 3D Eddy Current Finite Element Formulations on ECT Signals
Authors: Lee Hyang Beom
Published: March 2009

To obtain the simulated eddy current testing (ECT) signals of steam generator (SG) in nuclear power plant (NPP), nodal-based finite element (FE) analysis with magnetic vector potential (MVP) is usually used. To perform the numerical analysis, we derive the governing equation in terms of MVP and electric scalar potential (ESP) from Maxwell’s equations. To insure the uniqueness of solution, gauge condition has to be considered. In eddy current problems, Coulomb gauge condition (CGC) is usually used. In 2-D or 3-D axis-symmetric analysis, CGC is included during formulation and ESP is eliminated using some special assumption. Because CGC is not used during the formulation in 3-D analysis, we have to include artificially. And because of the heavy computation cost for 3-D analysis modified magnetic vector potential (MMVP) is used by elimination ESP. In this paper, effects of artificial treatment of CGC and elimination of ESP on ECT signal are investigated in order to help for obtaining accurate numerical simulation results.
Prediction of Ultrasonic Signals Captured from a Side-Drilled Hole Using a Rectangular Transducer
Authors: Kim Hak Joon , Song Sung Jin , Schmerr Lester W.
Published: March 2009

For the proper interpretation of ultrasonic measurement results from a side-drilled hole (SDH) using a rectangular transducer, it is very helpful to have a complete ultrasonic measurement model. A highly efficient ultrasonic beam model of a rectangular transducer and an accurate scattering model of a SDH are currently available. However, to develop such a complete measurement model, a reference model for the system efficiency factor is also needed. In this study a reference model suitable for a rectangular transducer is given and combined with existing models to develop a complete ultrasonic measurement model that can the predict ultrasonic signals from a SDH. Based on this model, we have calculated the ultrasonic signals from a SDH at different transducer orientations and compared the model-based predictions with experiments.
Development of a Novel Rod Compression Technique for Characterizing Local Surface Strength
Authors: Lee Yun Hee , Park Jong Seo , Nahm Seung Hoon , Huh Yong Hak
Published: March 2009

A nondestructive rod compression has been proposed as a new strength characterizing technique for in-service components. Using electrical discharge machining, milling machining, and stamping, it was possible to machine small rods, typically about 0.5 mm in both diameter and height on the target surface. Static compressions of the rods were carried out using a flat punch and their deformation behaviors were recorded as load-displacement curves. Referring to initial dimension of the rods, engineering stress-strain curves implying the yield strengths were calculated from the deformation curves. Surface yield strengths from the rod compressions were directly compared with reference compression results and their slight discrepancies were discussed from the influences of pre-deformation and damage of the rod and additive compliance of the base.
Development of Novel Optical Fiber AE Sensor with Multi-Sensing Function
Authors: Cho Hideo , Naruse Takashi , Matsuo Takuma , Takemoto Mikio
Published: March 2009

A novel optical fiber acoustic emission (AE) system with multi-sensing function in single
long fiber was developed and utilized for the estimation of AE sources of model steel plate and
jointed pipes. Multi-sensing function was achieved by dividing the single sensing fiber into several
sensor portions with different resonance frequencies. The resonance frequencies were provided by
winding the sensing fiber around the solid rods (sensor holders) with different diameters. The
monitoring system with three sensors in a 10 m long fiber was demonstrated to detect three wave
packets with different frequencies and correctly estimate the source locations of AEs from artificial
(Nelson-Sue) sources on a 0.9 wide x 1.8 m long steel plate. Here the arrival times of AEs for the
source location were determined by the continuous wavelet transform. Source locations on the steel
plate were determined within a distance error of 53 mm. The system also makes the location of the
pipe with damage possible.
Mixed-Mode Fatigue Crack Growth in Orthotropic Steel Decks
Authors: Choi Dong Ho , Choi Hang Yong , Chung Sang Hwan , Yoo Hoon
Published: March 2009

The strain energy density factor approach under mixed-mode condition is used for the
prediction of crack propagation in the orthotropic steel deck specimen, which is similar to that of
existing suspension bridges. Stress intensity factor approach is used to compare with strain energy
density factor approach for the fatigue crack growth analysis. The stress intensity factors are
computed by numerical extrapolation using cracked models for the different crack length. The study
shows that the fatigue crack propagation under mixed-mode condition is slower than that under
mode I only. Parametric studies on the initial crack length, critical crack length and parameters
related to crack growth equations are performed to show the influence of these parameters on the
fatigue life.
Study on the Control and Fabrication of Thermal Fatigue Crack for Reliability Enhancement of NDT in Reactor Coolant System
Authors: Lee Bo Young , Jin Hyung Kook , An Dae Hwan , Kim Jae Sung , Ryu Duck Hee , Lee Joon Hyun
Published: March 2009

Damages in nuclear facilities during the operation of the Reactor Coolant System (RCS)
are caused by cyclic loadings due to mechanical or thermal fatigue. Therefore, the development of
an integrated technology including fabrication of standard specimens and their practical usage is
needed to enhance the reliability of nondestructive testing for surge lines or main feed water lines.
In this study, thermal fatigue cracks on STS 304 plates (t = 6mm) and tubes (O.D = 89.7mm. t =
7.7mm) for performance demonstration inspection were fabricated for the Reactor Coolant System
(RCS) in nuclear power plants. In case of plates, cyclic thermal changes, from 20 to 450, were
loaded on the V-notched specimens under tensile stressed conditions. The applied tensile stress was
1,700MPa at the notch portion. In the case of tubes, cyclic thermal changes, from 35 to 355,
were applied on the V-notched specimens under compressive stressed conditions. In the case of
plates, the initial crack was generated at 17,000 cycles and the depth of crack was 2.54mm at
22,000 cycles. Unlike the plates, in the case of tubes, the initial crack formed at 14,000 cycles and
the crack penetrated the tube at 25,000 cycles. In this paper, shapes and fractographies of fabricated
thermal fatigue cracks, and the used cyclic thermal loads are presented.
Dispersion Behaviors of Wedge Waves Propagating Along Wedges with Bilinear Cross Sections
Authors: Yang Che Hua , Tsen Chun Zen
Published: March 2009

Wedge waves (WW) are guided acoustic waves propagating along the tip of a wedge,
with energy tightly confined near the apex. Like Lamb waves, wedge waves with displacement field
anti-symmetric about the mid-apex-plane are called anti-symmetric flexural (ASF) modes. This
study is focused on exploring the dispersion behaviors of ASF modes propagating along a bilinear
wedge (BW). A BW is wedge with a cross section of two apex angles, compared with a linear
wedge (LW) having a single apex angle. In the literature, many studies regarding to the dispersion
behaviors of ASF modes are reported for LW, but not for BW. In this study, a laser ultrasonic
technique and finite element simulations are used to investigate the dispersion behavior of BW-ASF
modes. It is found out that a BW-ASF mode is a result of mode coupling between the two LW-ASF
modes of the same order corresponding to the two apex angles of the BW.
Comparison of an Array of EMATs Technique and a Magnetostrictive Sensor Technique for a Guided Wave Inspection of a Pipe
Authors: Cheong Yong Moo , Jung Hyun Kyu , Kim Young Suk
Published: March 2009

The leakage of a pipe in nuclear power plants is a significant concern from the point of
view of nuclear safety. Because of the geometrical complexity of a pipe and an inaccessibility due to a
high radiation, it is difficult to inspect it by the conventional ultrasonic methods. The guided
ultrasonic method can be useful for the inspection of a pipe in those harsh environments. Based on the
analysis of the dispersion curves for a pipe, a torsional vibration mode, T(0,1) was selected for the
detection of cracks. The T(0,1) mode has many advantages, such as a higher sensitivity for a crack
from the viewpoint of its non-dispersion characteristics and its wave structure. The torsional mode
can be generated by using either an array of electromagnetic acoustic transducers (EMATs) technique
or a magnetostrictive sensor technique. The detectability of the cracks was estimated through a series
of experiments with artificial notches on a pipe.
Usefulness of Thermography in Evaluation of Patients with FBSS Following Radiofrequency Dorsal Root Ganglion Lesioning
Authors: Park Jung Yul , Park Juno , Kim Sang Dae , Lim Dong Jun
Published: March 2009

The changes in thermographic pattern were studied, in patients with persistent back and leg pain after surgery, to validate its significance in evaluating the clinical status following percutaneous radiofrequency (PRF) lesioning on dorsal root ganglion. A total of 90 patients with persistent back and leg (52 males, 38 females, mean age 46.2 years) with more than 6 months of duration following lumbar surgeries were enrolled into study. Thermography was performed before and after PRF procedures. PRF procedures were percutaneously done with C-arm guidance and adjustments from physiologic monitoring. Assessments included the clinical symptoms, signs and changes of thermographic pattern before and after PRF procedure. Minimal follow up period was 6 months. All patients tolerated the RF procedures without complications. Thermographic findings before procedures were agreeable to clinical and radiographic findings in 81(90%) of patients. PRF procedure provided substantial improvement of pain (>50% pain reduction) in 69(76.7%) and 63(70%) at 1 and 6 months following procedures. Thermographic findings in 80(88.9%) of these patients seemed to correlate with clinical improvement. However, 12 patients (13.3%) showed no significant thermographic changes despite clinical improvement. Clinical factors that were not statistically significant but were related to better outcome were younger age, unilateral pain, no significant dysesthesia, less number of operations, no instrumentation. Results of this study indicate that thermography may have a specific role in evaluating these patients, especially when comparing with clinical status.
Test and Evaluation of a Newly Built Multi-Purpose Transmission Type Polariscope
Authors: Baek Tae Hyun , Kim Myung Soo
Published: March 2009

A multi-purpose polariscope was developed by applying an electro-mechanical control
system to a diffused transmission-type circular polariscope. A conventional polariscope is only good
for manual control of optical elements. The new polariscope system was devised to be controlled
through two stepping motors and two magnetic clutches. The new polariscope can be used not only
for the point-wise measurement using Tardy compensation technique but also for the full-field fringe
analysis using conventional and/or phase measuring techniques, if applicable. The distributions of
digitally determined unwrapped isoclinics and isochromatics using the digitized images obtained
from the developed polariscope were in close agreement to manual measurements.
Acoustic Emission Monitoring of Ablative Composite Liner Bonded on Steel Nozzle under Static Loading
Authors: Shul Chang Won , Lee Kee Bhum , Kim Jong Hwan , Koo Song Heo
Published: March 2009

AE technique was applied to the structural strength tests of the ablative composite liner
bonded on steel nozzle to figure out the unexpected problem that happened during the flight test. Two
different kinds of specimen, which were specimens with some initial crack and without initial crack
each, were used for the test. AE test methodology and parameters were investigated to assess the
damage of them. NDT using X-ray technique was performed to improve the test reliability before and
after each test. The study revealed that AE technique is a good method to evaluate damage on this
kind of specimen with better accuracy.
Comparison of Computational Crack Path Predictions with Experimental Findings for a SEN-Specimen under Anti-Plane Shear Loading
Authors: Buchholz Friedrich G. , Teichrieb Victor
Published: March 2009

In this paper the rather complex 3D fatigue crack growth behaviour in a SEN-specimen
under anti-plane shear loading is investigated by the aid of the programme ADAPCRACK3D and
by application of a recently developed 3D fracture criterion. It will be shown that the
computationally simulated results of fatigue crack growth in the FE-model of the specimen are in
good agreement with experimental findings for the development of two anti-symmetric cracks,
which originate from the two crack front corner points, that is where the crack front intersects the
two free side surfaces of the laboratory SEN test-specimens. Consequently, also for this case with a
rather complex 3D crack growth of two anti-symmetric cracks, the functionality of the
ADAPCRACK3D-programme and the validity of the proposed 3D fracture criterion can be stated.
Damage and Crack Initiation Behavior of Duplex Stainless Steel during Cyclic Loading
Authors: Chai Guo Cai , Lillbacka Robert
Published: March 2009

Two phase metals during cyclic loading can suffer from non-uniform load or strain
sharing between the phases due to elastic/plastic anisotropy. This can strongly influence the fatigue
damage and crack initiation behavior. In this study, the fatigue damage and crack initiation behavior
of an austenitic-ferritic duplex stainless steel with anneal/quenched and aged conditions has been
studied by both experimental investigations and simulation using multi-scale material modeling. It
was found, both experimentally and via simulations, that the material damage and crack initiation
start in the ferrite phase in the material with the anneal/quenched condition and in either the ferrite
or austenite phase in the material with the aged condition, mainly in the weakest phase if the
deformation hardening is considered.
Low-Cycle Fatigue Behavior of Small Slice Specimens of Zircaloy-4 at Elevated Temperature
Authors: Cai Li Xun , Ye Yu Ming
Published: March 2009

A series of strain fatigue tests were carried out on small bugle-like slice-specimens of
Zr-4 alloy at 20 and 400. According to Elastic and Plastic Finite Element Analysis
and assumption of local damage equivalence, a strain formula was given to transform transverse
strain of the specimen to uniaxial strain. Based on the test results of the alloy and the strain transform
formula, M-C (Manson-Coffin) models to be used for estimating uniaxial fatigue life of Zr-4
alloy were obtained. The results show that, the alloy mainly behaves as cyclic softening at 20 and
as cyclic hardening at 400, and the elevated temperature can lead serious additional fatigue damage
of the alloy and the effect of the elevated temperature impairs gradually with increasing of amplitude
strain. A conclusion is helpful that prediction life by using M-C model based on traditional
strain transform equation is quite conservative when uniaxial strain amplitude is less than 0.5%.
Development of Web-Based Fatigue Analysis System for Machine Components and Structures
Authors: Noh Byeong Wook , Bae Sung In , Ham Kyung Chun
Published: March 2009

A fatigue analysis program to calculate fatigue lives of mechanical components and
structures from FE(Finite Element) results is developed. The useful characteristic of this program is
operated under Web environment. So, any designer who design fatigue strength of components and
structures can use without other program installation. For the assessment of multi-axial fatigue
damage, signed equivalent stress method and critical plane approach have been employed. Each
method is compared and the results of Signed von Mises stress method has similar to the results of
Smith-Waston-Topper's parameter using critical plane approach. The results were compared with
those from commercial program FE-Fatigue6.0 and it was observed that fatigue life and cumulative
damage distribution calculated applying same fatigue resistance curve. The results of calculated
fatigue life using Web based program agree well with those from FE-Fatigue6.0.
Discrete-Continuous Configuration Optimization Methods for Structures Using the Harmony Search Algorithm
Authors: Lee K.S. , Choi Chang Sik
Published: March 2009

This paper proposes an efficient structural optimization methods based on the harmony
search (HS) heuristic algorithm that treat integrated discrete sizing and continuous geometric
variables. The recently developed HS algorithm was conceptualized using the musical process of
searching for a perfect state of harmony. It uses a stochastic random search instead of a gradient
search so derivative information is unnecessary. A benchmark truss example is presented to
demonstrate the effectiveness and robustness of the new method, as compared to current
optimization methods. The numerical results reveal that the proposed method is a powerful search
and design optimization technique for structures with discrete member sizes, and may yield better
solutions than those obtained using current methods.
Quasi-Brittle Fracture of Lamellar γTiAl: Simulation Using a Cohesive Model with Stochastic Approach
Authors: Kabir R. , Cornec Alfred , Brocks Wolfgang
Published: March 2009

Quasi-brittle fracture of fully lamellar two phase (α2+γ)TiAl is investigated both
experimentally and numerically. Fracture tests are conducted at room temperature, which fail in a
quasi-brittle and unstable manner but exhibit significant variations in crack initiation and
propagation prior to unstable failure. Fractographic investigations are performed which elucidate
the micromechanical causes of the macroscopic behaviour. The observed deformation and fracture
behaviours of the specimens are simulated by a finite element model containing cohesive elements
for modelling the material separation. In order to capture the scatter of the macroscopic behaviour, a
stochastic approach is chosen, in which local variations of cohesive parameters are taken into
account. The model can describe and explain the physical phenomena of the specific material.
Large Deformation Dynamic Meshfree Simulation of Damage and Failure in Geomaterials
Authors: Wang Dong Dong
Published: March 2009

An explicit dynamic Galerkin meshfree formulation under the updated Lagrangian
framework is presented to simulate large deformation damage and failure process in geomaterials.
The failure initiation and development are characterized by the pressure sensitive Drucker-Prager
plasticity coupled with the isotropic energy-based damage theory. A stabilized conforming nodal
integration based on non-local gradient smoothing is employed to improve the computational
efficiency and to regularize the material instability arising from strain localization. The capability of
the proposed methodology to model the evolution of dynamic failure in geomaterials is demonstrated
through a numerical example.
Numerical Study on Damage of Half-Infinite Bar
Authors: Zhao Guang Hui , Zhang Nian Mei , Yang Gui Tong
Published: March 2009

Drillstring in oil drilling is simplified as a half-infinite bar. Taking account of
Peierls-Nabarro(P-N) force and viscous effect of solid, dynamic response is simulated under
harmonic driving at the end of the bar. With the physical properties specified, periodic,
quasi-periodic and chaotic motions would appear as a function of the amplitude of external driving.
We find that all the particles of the bar have the same qualitative characters, while vibrating
amplitude decreases along the bar. It appears that particles of the bar reach chaotic motion through
quasi-periodic motion. Investigation of this half-infinite bar will provide references for design of
drillstring to keep motion away from chaotic region.