bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of Moisture Content in Powdered Food Using Microwave Free-Space Transmission Technique
Authors: Kim Ki Bok , Park Seon Gun , Kim Ji Yeon , Kim Jong Heon , Lee Chan Joo , Kim Man Soo , Choi Man Yong
Published: March 2009

In this study, microwave free-space transmission technique was applied to measure the
moisture content of powdered food (wheat flour, milk powder, and coffee powder). In frequency
range from 1 to 15 GHz, the microwave attenuation and phase shift due to moisture content of food
samples were measured and analyzed using vector network analyzer, double rigid horn antennas, and
sample holder filled with moist food samples. To estimate the relationship between moisture density
of powdered food and the attenuation and phase shift, correlation analysis was performed. The
correlation coefficients at each food sample were greater than 0.91. The calibration equation for
moisture content measurement having attenuation and phase shift as independent variables at 15 GHz
was developed and evaluated. The coefficient of determination and root mean square for all food
samples were 0.974 and 0.328 % respectively.
Frequency Windowing Technique for Reducing Multi-Path Noise in Free-Field Reciprocity Microphone Calibration Method
Authors: Kwon Hyuck Sang , Suh Sang Joon , Suh Jae Gap
Published: March 2009

The sensitivity of the microphone is determined absolutely by primary calibration
technique based on the reciprocity principle. The free-field calibration has the inherent problem due to
the weak signal received in the microphone. Multi-path noises such as cross-talk and reflections
corrupt the received signal, and thus the sensitivity evaluation is poor. The time selective method has
been widely used as the useful tool to get rid of such noises. However FFT based signal processing
invokes unwanted processing error such as leakage. A well designed frequency window which would
be a kind of low-pass filter would reduce the leakage problem, and it helps to separate multi-path
noises from the directly propagated signal well. The result well shows the advantages in separating
the noises and the availability in the free-field calibration with the enhanced sensitivity evaluation.
Liquid Behavior in Containers with a Liquid-Packing Bag for Liquid Products Subjected to Drop Impact
Authors: Umezaki Eisaku , Shinoda Yuuma , Futase Katsunori
Published: March 2009

The behavior of liquid in containers subjected to impact loads due to free fall was
investigated using a visualization technique. Two types of containers were used. One consisted of a
case made of transparent plastic plates and a liquid-packing bag made of transparent plastic films. The
bag contained about 1,000 ml of liquid. The other was a case made only of transparent plastic plates.
The case contained about 1,000 ml of water. The liquid consisted of water and ethanol. Polyethylene
particles of about 3 mm in diameter were included in the liquid to visualize the movement of liquid in
the containers. The containers were subjected to impact due to free fall, and photographs of the
containers were taken using a high-speed camera. Results indicated that the behavior of liquid in the
container with a liquid-packing bag is different from that of the container without a liquid-packing
bag.
Synthesis and Characterization of Ce-Doped BZT Thin Films Deposited by a RF Magnetron Sputtering Method
Authors: Choi Won Seok , Park Young , Boo Jin Hyo , Yi Junsin , Hong Byung You
Published: March 2009

We investigated the structural and electrical properties of the 0.5% Ce-doped
Ba(ZrxTi1-x)O3 (BZT) thin films with a mole fraction of x=0.2 and a thickness of 150 nm for the
MLCC (Multilayer Ceramic Capacitor) application. Ce-doped BZT films were prepared on
Pt/Ti/SiO2/Si substrates by a RF magnetron sputtering system as a function of Ar/O2 ratio and
substrate temperature. X-ray diffraction patterns were recorded for the samples deposited with three
different substrate temperatures. The thickness and the surface roughness of the films deposited with
different Ar/O2 ratios were measured. The oxygen gas, which was introduced during the film
deposition, had an influence on the growth rate and the roughness of the film. The surface roughness
and dielectric constant of the Ce-doped BZT film varied with Ar to O2 ratios (5:1, 2:1, and 1:1) from
1.21 nm to 2.33 nm and 84 to 149, respectively. The Ce-doped BZT film deposited at lower
temperature has small leakage current and higher breakdown voltage.
Evaluation of Thermal Stress Resistance of Titanium Alloy for the Air Breathing Engine
Authors: Lee Young Shin , Kim Hyun Soo , Choi Young Jin , Kim Jae Hoon
Published: March 2009

This study is conducted in order to estimate the structural characteristics for inlet port of air
breathing engine under flight condition at 12 ~ 15 km height and Mach Number 2 ~ 4. Inlet port of air
breathing engine is heated up from 307 oC to 427 oC, so that is reached plastic zone partially. The
material properties at high temperature such as young’s modulus, thermal expansion coefficients and
thermal conductivity are applied to the analysis. The transient temperature and stress analysis are
performed by the finite element method using nonlinear commercial code ABAQUS. The analysis is
performed for the two materials, Titanium alloy and AISI4130 Steel and two FEM element type, shell
and solid, to select preliminary design model for flight condition. Thermal boundary conditions are
applied at inlet port until 5 s, and these conditions are maintained until 150 s. The results of the
analysis recommend tendency of thermal stress and temperature contour. This study is expected
useful to select the structural material and to determine shape of air inlet port of air breathing engine
which satisfied the structural design safety.
Thermal Properties of a Liquid-Crystalline Polyurethanes Containing Biphenyl Mesogen
Authors: Lee Jong Baek , Lee Kwang Hyun , Kang Byung Chul , Kang Byung Won , Lee Sang Ll , Lee Jin Kyung
Published: March 2009

A new type of thermotropic main-chain liquid crystalline polyurethanes containing
biphenyl units was synthesized by polyaddition reaction of diisocyanates such as 2,6-tolylene
diisocyanate, 2,5-tolylene diisocyanate, 2,4-tolylene diisocyanate, and 1,4-phenylene diisocyanate,
with 4,4′-Bis(11-hydroxyundeyloxy)biphenyl (BP11). The structure of the monomer and the
corresponding polymers were confirmed FT-IR and 1H NMR spectroscopic methods. BP11 exhibited
a smectic type mesophase, however, nematic phase was found for all synthesized liquid crystalline
polyurethanes except for 1,4-phenylene diisocyanate/BP11 based polyurethane. For example,
polyurethane 2,5-TDI/BP11 exhibited monotropic liquid crystallinity in the temperature ranges from
173 to 156 °C on the cooling stage.
High Resolution Electrical Resistance Profiling of Laboratory Soil Specimens
Authors: Lee Jong Sub , Cho Gye Chun , Hong Eun Soo
Published: March 2009

An electrical needle-size probe is developed to effectively assess one-dimensional spatial
variability of laboratory soil specimens in high resolution. A calibration procedure is also presented to
determine resistance from the measured complex impedance. The capability of the developed
electrical needle probes to resolve interfaces and spatial variability is explored using sand specimens
prepared by various conditions. The complex impedance is measured 0.2~0.5 mm for every
specimen. Results show that the coefficient of variation increases as the size of the probe reaches the
size of the particle while a very large ratio of probe size to grain size would decrease the detectability
of local soil variations due to averaging effects and smoothening. The attainable spatial resolution
depends on the needle diameter: submillimetric resolution is typically achieved in laboratory
applications and it can be scaled for field applications. The local electrical parameters permit one to
infer the soil porosity and the electrolyte conductivity.
Inspection of Thin Copper Heat Exchanger Tubes Using SQUID-NDE System
Authors: Hatsukade Yoshimi , Okuno Shinya , Mori Kazuaki , Tanaka Saburo
Published: March 2009

This study is aimed at developing an eddy-current-based SQUID-NDE system for in-situ
inspection of micro flaws on thin copper heat exchanger tubes. The system employs a high
temperature superconductor (HTS-) SQUID gradiometer and a Helmholtz-coil-type inducer. As
specimens, copper tubes 6.35 mm in outer diameter and 0.8 mm in thickness with artificial surface
flaws of several tens μm in depth were inspected using the system. Magnetic response due to a flaw of
10 μm in depth on the tube moving at 32 m/min was successfully detected while applying an
excitation field of 10 μT at 3 kHz to the tube. Numerical simulations were also conducted to evaluate
how many sensors would be required for inspection around the circumference of an entire tube.
A Study on the Evaluation Methods of Running Safety for Railway Vehicle
Authors: Ham Young Sam , Hong Jai Sung , Oh Taek Yul
Published: March 2009

The important factor to evaluate the running safety of a railway vehicle would be the
interaction force between wheel and rail(derailment coefficient), for which is one of important factors
to check the running safety of a railway vehicle that may cause a tragic accident. Especially, a newly
developed vehicle that first runs commercially requires necessarily the measurement and evaluation
of derailment coefficient for securing the safety of a vehicle while measuring the derailment
coefficient in view of securing running safety could be the more important factor than any other
factors. In the meanwhile, it should be also measured the interaction force between wheel and rail in
view of track maintenance as well as running safety because increased weight of a vehicle while it is
running over a railway may cause damages or destruction on track components such as rails, sleepers
and etc consisted of track and any rapid distortion of track. For the reason, the study was intended to
evaluate the curving performance and the running safety from the analyses of dynamic running
properties, manufacturing wheel axes to measure the working operation of wheels/rail, static load test,
derailment coefficient calculated by running test on main track, ratio of wheel unloading, lateral force
tolerance of the vehicle that is newly manufactured and commercially running on Gwangju Urban
Railway and describe the results.
Application of Ultrasonic Test System for Test Performance Improvement of Welding Flaw
Authors: Kim Chang Hyun , Kim Jae Yeol , Song Kyung Seok , Cha Yong Hoon
Published: March 2009

In this research, we used nondestructive test based on ultrasonic test as inspection method, and made up inspection robot in order to control of ultrasonic probe on the SWP surface, and programmed to signal processing code and pattern classifying code by user made programming code. For evaluation of flaw signal is reflected on welding flaw, user-made program codes are composed of signal processing and probability neural network (PNN) and backpropagation neural network (BPNN). And then, we actually confirmed to the theoretical advantage of each neural network method compared probability neural network with backpropagation neural network for classification and recognition rate. For the application of classifier to SWP inspection system, BPNN classifier is adequate in the first stage. And then, the application of PNN classifier is adequate as the next stage. Because of PNN application need enough sample data that is due to probabilistic density function.
Risk Assessment of Axially Loaded Single Piles using RSM-based Reliability Method
Authors: Huh Jung Won , Kwak Kiseok
Published: March 2009

An efficient and accurate hybrid reliability method is developed to quantify the risk of an
axially loaded pile considering pile-soil interaction behavior and uncertainties in various design
variables. It intelligently integrates the concepts of the response surface method, the finite difference
method, the first-order reliability method, and the iterative linear interpolation scheme. Uncertainties
associated with load conditions, material and section properties of the pile and soil properties are
explicitly considered. The algorithm is verified using the Monte Carlo Simulation technique.
A Development of a New Life Test Procedure for Fan Motors
Authors: Shin Wae Gyeong , Lee Soo Hong , Song Young Sik
Published: March 2009

Reliability of automotive parts has been one of the most interesting fields in the automotive industry. Especially small DC motor was issued because of the increasing adoption for passengers’ safety and convenience. For several years, small DC motors have been studied and some problems of a life test method were found out. The field condition was not considered enough in the old life test method. It also needed a lot of test time. For precise life estimation and accelerated life test, new life test procedure was developed based on measured field condition. First, vibration condition on vehicle and latent force on fan motor shaft were measured and correlated with each other. Second, test condition was decided by obtained data. Finally, life of fan motors was estimated by new life test method in shorter test time.
Knee Joint Analysis for Optimal Ligament Surgical Reconstruction Using Three Dimensional Motion Model
Authors: Moon Byung Young , Kang H. K. , Son Kwon , Chung S.W.
Published: March 2009

Anterior cruciate ligament(ACL) is liable to a major injury that often results in a functional impairment requiring surgical reconstruction. The success of reconstruction depends on such factors as attachment positions, initial tension of ligament and surgical methods of fixation. The purpose of this study is to find isometric positions of the substitute during flexion/extension. A threedimensional knee model was constructed from CT images and was used to simulate length change during knee flexion/extension. The results showed that minimum length changes were 1.9~5.8 mm(average 3.6±1.4 mm). The proposed method can be utilized and applied to optimal reconstruction for ACL deficient knee.
The Effect of the Operational Conditions on the Quantitative Leak Rate of Leak Detectors
Authors: Shin Yong Hyeon , Hong Seung Soo , Lim In Tae , Chung Kwang Hwa
Published: March 2009

The Korea Research Institute of Standards and Sciences has developed and maintained leak
standards systems, and has accumulated much data on leak standards that have been disseminated
during calibration and testing services. We have found that the indicative value of a leak detector and
a halogen leak detector varies a lot, depending on the conditions encountered during sniffer mode
operation. Therefore, to measure the reliability of the leak rate or when performing a leak test, proper
test conditions are necessary. In addition, we found that the reliability increased when we used a guide
tube that could influence the flow of air.
Characteristics of Stick Regions in Frictional Vibration with a Compressed Nonlinear Spring
Authors: Shin Ki Hong , Lee Young Sup
Published: March 2009

In-plane characteristics of a single degree of freedom frictional system with a compressed
spring are considered. The compressed spring is vertically installed to the mass moving horizontally
along the friction interface. The compressed spring can introduce a nonlinear negative stiffness into
the in-plane motion. The resulting system has a multiple equilibrium points; an unstable point at the
center and two stable points on either side. It is shown that two stable equilibrium points can be
separated far apart by increasing the compression ratio and the stiffness of the spring. The friction
system is often characterized by stick and slip motions that cause unfavorable effects such as wear,
noise, and chatter etc. It is demonstrated that increasing the compression ratio and the stiffness of the
spring results in decreasing the size of the stick regions.
Preparation and Characterization of Polymer Light Emitting Diodes with ITO/PEDOT:PSS/MEH-PPV/LiF/Al Structure
Authors: Yoo Jae Hyouk , Chang Ho Jung , Gong Su Cheol , Baek In Jae , Lim Hyun Seong , Chang Gee Keun , Chang Young Chol , Kim Hee Joon
Published: March 2009

Polymer light emitting diodes (PLEDs) with ITO/PEDOT:PSS/MEH-PPV/LiF/Al
structures were prepared by spin coating method on the patterned ITO(indium tin oxide)/glass
substrates. MEH-PPV [Poly(2-methoxy-5(2-ethylhexoxy)-1,4-phenylenevinyle)] and PEDOT:PSS
[poly(3,4-ethylenedioxythiophene):poly(styrene sulfolnate)] polymers were used as the light
emitting and hole transport materials. The dependence of the plasma treatment of ITO anode films
on the optical and electrical properties of the PLEDs was investigated. The sheet resistances
increased with increasing the plasma intensities from 40W to 300W in RF power. In contrast, the
surface roughness was improved as the plasma intensity increased. The maximum current density
and luminance were found to be about 97.5 mA/ and 55 cd/m2 at 8 V for the PLED sample
coated on ITO/glass substrate with plasma treatment of 100W for 30s under 40 mtorr O2 pressure.
Reliability of Flip Chip Package with Underfills under Thermal Shock
Authors: Noh Bo In , Jung Seung Boo
Published: March 2009

The thermal fatigue properties of the solder joints with various underfills were evaluated
by thermal shock test. Flip chip package with electroless nickel-immersion gold plated on Cu pad of
FR-4 substrate and the Sn-37Pb solder ball was used. The thermal fatigue crack initiated at the
edges of interface between solder and silicon die. The fatigue property of package with underfill,
which has a higher glass transition temperature (Tg) and lower coefficient of thermal expansion
(CTE) value was better than that of package with underfill having a lower Tg and higher CTE.
Study on Evaluation of AE Signals at Weld Region of SA 516 Steel
Authors: Gyun Na Eui , Hoon Kim , Ono Kanji
Published: March 2009

The purpose of this study is to find out the method to detect AE signals at around the
notch tip and to evaluate the AE signal characteristics for the basemetal, PWHT(post weld heat
treatment) and weldment specimens of SA-516 steel during bend test. AE signals were produced in
the process of plastic deformation. AE signal strength and amplitude of the weldment was the
strongest, followed by PWHT specimen and basemetal. More AE signals were produced from the
weldment because of the oxides, and discontinuous mechanical properties. The stronger AE signal
strength, amplitude and more AE event counts for the weldment were shown.
A Study on Damage Behavior and Strength of Smart Material under Low Temperature Using Acoustic Emission
Authors: Lee Jin Kyung , Park Young Chul , Lee Sang Ll , Lee Joon Hyun , Lee Jong Baek
Published: March 2009

Tensile residual stress happen by difference of coefficients of thermal expansion between
fiber and matrix is one of the serious problems in metal matrix composite (MMC). TiNi alloy fiber
was used to solve the problem of the tensile residual stress as the reinforced material. TiNi alloy fiber
improves the tensile strength of composite by occurring compressive residual stress using shape
memory effect in the matrix. A hot press method was used to create the optimal condition for the
fabrication of shape memory alloy (SMA) composite. The bonding effect between the matrix and the
reinforcement within the SMA composite was strengthened by the cold rolling. The fabricated
composite by these processes can be applied as a part of the aircraft, and this part is operated under
severe flying condition such as low temperature and high pressure. In this study, an acoustic emission
technique was used to quantify the microscopic damage behavior of cold rolled TiNi/Al6061 SMA
composite at low temperature condition. The results showed that the tensile strength of the
TiNi/Al6061 SMA composite increased with the TiNi reinforcement at low temperature condition,
but the strength for the specimen subjected to the cold rolling decreased. AE parameters of AE counts,
amplitude and energy were useful to evaluate the microscopic damage behavior of the composite.
Strain Monitoring and Damage Detection of a Filament Wound Composite Pressure Tank Using Embedded Fiber Bragg Grating Sensors
Authors: Park Sang Wuk , Kang Dong Hoon , Bang H.J. , Park Sang Oh , Kim Chun Gon
Published: March 2009

Composite pressure tanks are rapidly expanding in their range of use. However, for high
pressure flammable or toxic gases, there is less confidence about their reliability. In this study, fiber
Bragg grating (FBG) sensors embedded into a composite pressure tank monitored strain and detected
damage. The sensor heads and fiber optic lines were protected with an acrylate recoating, adhesive
films, PVC tubes and Teflon film to survive under the harsh environment of the filament winding
process. During the quasi-static loading test, the internal strain was measured with embedded FBG
sensor arrays. In order to detect damage occurred during the test, impacts were applied on three
different positions in each side by an impact hammer. The difference between damaged and
undamaged sides in impact response was analyzed. An interrogation system using a
wavelength-swept fiber laser (WSFL) was used for measuring strain, and an erbium-doped fiber
amplifier (EDFA) laser source with a tunable Fabry-Perot filter was used for measuring impact
response.
Biologically Inspired Smart Sensor for Acoustic Emission Detection
Authors: Lee Young Sup , Im Hyoung Jin , Kwon Jaehwa , Yoon Dong Jin
Published: March 2009

This paper presents concept, analysis and experiment of a novel sensor which is based on
biologically inspired approach for acoustic emission (AE) detection. It is known that a conventional
AE sensor consists of a matching layer, piezoelectric transducer, backing layer, supporting electric
circuit and casing. The conventional AE sensors have been widely used to detect defects in various
structures and they have designed as either broadband or resonant type. However, the novel sensor
described in this paper utilizes the concept of hearing organs in animals with the help of micro
electro-mechanical systems (MEMS) technology. The basic design with theoretical investigation
including finite element analysis showed the core hearing element such as a hair cell could be
implemented with the piezoeletric material. Also it is found that the dimensional variety and proper
distribution of such elements inside the sensor are critical parameters to the detectability of AE
signals from structures. Both the broadband and resonant type AE sensors with relevant electric
circuits could be implemented with this novel sensor concept.
Dynamic Characteristics of Novel Ionic-Polymer-Metal-Composites
Authors: Oh Il Kwon , Jeon Jin Han
Published: March 2009

The IPMC, one of new sensing and actuating materials is known for the fast and flexible
bending actuation upon electric fields. In this paper, we investigated the dynamic deformation
characteristics of the novel IPMC according to several fabrication methods. First we studied the effect
of the surface modification of metallic electrodes on the large deformation. Present results show that
the sandblasting method can give more reliable and large deflections than the sandpapering method
under the same control voltage because the platinum electrode can be infiltrated into the
ionic-polymer by the sandblasting method. Second, the IPMC with Li+ counter ions shows more large
deformation than that with any other counter ions. Also, present results show the dynamic hysteresis
according to driving voltages.
Fatigue Reliability Analysis of a Suspension Bridge Using Long-Term Monitoring Data
Authors: Ni Yi Qing , Ye X.W. , Ko Jan Ming
Published: March 2009

A method for probabilistic fatigue life assessment of steel bridges by using long-term
monitoring data is proposed and applied for fatigue reliability analysis of the suspension Tsing Ma
Bridge. In this method, the daily number of cycles for each stress range is obtained from the measured
stress history and its probability distribution is estimated based on statistical analysis of long-term
measurement data. The statistics obtained for all concerned stress ranges is combined with the S−N
relationships stipulated in specifications to conduct a probabilistic assessment of fatigue life with the
use of the Palmgren-Miner rule, from which the mean value and standard deviation of the fatigue life
as well as the failure probability and reliability index versus fatigue life are obtained. The proposed
method is illustrated by using 80-day strain measurement data from the suspension Tsing Ma Bridge
which is instrumented with a long-term structural health monitoring system.
Assessment Model for the Safety and Serviceability of Steel Beams Using Terrestrial LiDAR
Authors: Park Hyo Seon , Lee H.M. , Kwon Y.H. , Seo J.H. , Rhim Hong C.
Published: March 2009

Structural monitoring is concerned with the safety and serviceability of the users of
structures, especially for the case of building structures and infrastructures. When considering the
safety of a structure, the maximum stress in a member due to live load, earthquake, wind, or other
unexpected loadings must be checked not to exceed the stress specified in a code. Although the steel
will not fail at yield, excessively large deflections will deteriorate the serviceability of a structure.
Therefore, to guarantee the safety and serviceability of steel beams, the maximum stress and
deflection in a steel beam must be monitored. However, no practical method has been reported to
monitor both the maximum stress and deflection. In this paper, assessment model for both safety and
serviceability of a steel beam is proposed. The model was tested in an experiment by comparing stress
level estimated by LiDAR system and stress level directly measured from electrical or fiber optic
sensors. The maximum deflection measured from LiDAR system is also compared with the
maximum deflection directly measured from LVDTs. In addition to displacement measurement, the
proposed system can provide information on deformed shapes of steel beams.
Development of Heat Resistant AE Monitoring System Using Optical Fiber Sensor
Authors: Matsuo Takuma , Cho Hideo , Takemoto Mikio
Published: March 2009

We developed an advanced optical fiber Acoustic Emission (AE) monitoring system with
a phase compensation feed back circuit. Two lasers transmitted through the reference and sensing
arms are combined by a 2x2 coupler and detected by two photodiodes as the intensity change of the
interfered laser. Outputs of the photodiodes are then combined in a differential amplifier which
extracts error signal and improves the S/N ratio. The developed system was demonstrated to detect
weak guided wave AE signals such as zero-th order longitudinal cylindrical wave (Lo-mode) with
the S/N ratio higher than that of PZT sensor.
This system was utilized to monitor the oxidation resistance of various alloys during thermal
cycles from 300 K to 1273 K. We detected weak AE signals from micro fractures of growing oxide
films of boiler tube and austenitic stainless steel, but no AE from Inconel 600 tubes. Here the
optical fiber sensor was wound over the tube at 600 K. Both the AE counts and amplitudes during
thermal cycles showed clear tendency depending on the oxidation resistances of the alloys.
FE Model Updating for Health Monitoring of Structures and its Experimental Verification by Damage Detection
Authors: Heo Gwang Hee , Jeon Joon Ryong , Lee Chin Ok , Lee Gui , Lee Woo Sang
Published: March 2009

This paper presents an effective method of FE model updating for health monitoring of structures by applying ambient vibration. And this method is experimented through damage detection and proved to be valid. Experiment about ambient vibration is performed on cantilever beam, and the dynamic characteristics are analyzed by NExT and ERA. The results of such experiments are compared to those of FE analysis, and this comparison enables us to overcome some errors in experiments and analysis. On the basis of improved results by the comparison, model updating is performed in order to construct a basic structure for health monitoring. For model updating, we employ direct matrix updating method (DMUM) and Error matrix method (EMM) in which ambient vibration is easily applied. The model updating by the methods are again evaluated in terms of error ratio of natural frequency, comparing each result before and after updating. Finally, we perform experiments on damage detection to verify the method of updating presented here, and evaluate its performance by eigen-parameter change method. The evaluation proves that the method of FE model updating using ambient vibration is effective for health monitoring of structure, and some further application of this method is suggested.
Evaluation of Residual and Actual Stress Levels of Steel Columns in Existing Building Structures due to Working Loads
Authors: Park Hyo Seon , Lee W.H. , Yun K.S. , Rhim Hong C.
Published: March 2009

A wide variety of residual stress measurement methods can be used to measure the axial
stress in a column. One of the most widely used techniques for measuring residual stress is slotting
method since it is relatively simple and cost-effective to implement at vertical columns in field.
However, the slotting method is considered to be semi-destructive or destructive method depending
on the amount of material to be removed. Therefore, in this paper, optimal depth of slots for
measuring actual stress is presented to minimize the amount of material to be removed. Finite element
method is used to estimate the minimum depth of the slot in H-shaped steel column. By performing
actual saw cutting, optimality of the simulated depth of the slot is investigated.
Assessment of Local Damage Level in Engineered Cementitious Composites (ECC) Using Stress Wave Propagation
Authors: Kim Dong Soo , Lee Kwang Myong , Kim Nam Ryong , Jin Seok Woo
Published: March 2009

Non-destructive tests using impact echo (IE) and pulse velocity measurements (PVM) were conducted to evaluate degradation of elastic properties of cement-based materials during uniaxial compression. Prismatic specimens (100100200 mm) made of ECC (engineered cementitious composites) mixture, were used for the test. The specimens were subjected to monotonic axial loading until failure while resonance frequency and travel time were recorded. Changes in the amplitude, velocity, and frequency were correlated to the increasing damage levels and the feasibility of IE and PVM techniques to evaluate the damage level in ECC was preliminarily assessed.
Magnetoelastic Measurements of Steel Stress under Uniaxial Loading
Authors: Rhim Hong C. , Oh Bo Hwan , Park Hyo Seon
Published: March 2009

An attempt has been made to measure existing steel stress using magnetoelasticity. A
device has been developed and used for the measurement of magnetism in response to the
deformation of a steel bar. The proposed technique can be used for the assessment of existing
reinforced concrete structures by the measurements of steel stress embedded inside concrete. A
traditional technique requires to break the existing steel bar to measure existing strain. However, the
proposed technique is developed to measure the stress without damaging the steel bar. A successful
application of magnetoelasticity depends on the establishment of relationship between elastic and
magnetic response due to loading. To investigate the correlation between the two, steel bars are
loaded in tension under uniaxial loading while the magnetic reading is recorded. Based on the test
results, equations are suggested to predict stress for steel bars with different diameters.
A Study on the Diagnosis Method of Concrete Structures of School Buildings Using Non-Destructive Tests Based on Stress Waves
Authors: Cho Young S. , Lee Han Seung
Published: March 2009

As most of the elementary, junior high, and high school buildings nationwide have been deteriorated since the quantitative increase of the buildings from 1985, many experts present the issues on the possibility of the structural instability of the building as well as the increase of the cost for maintenance of the building. So, it is necessary to examine the necessary structural information of the school buildings during the course of maintaining education facilities, and it is also necessary to establish some credible accessing procedures on the deteriorating school facilities so that the building structural engineers can propose the necessary standards for the proper maintenance and repairing works. To achieve the necessity, researches have been conducted to find out the ways of diagnosing the compressive strength and the durability of the concrete structures by measuring the compression wave velocity of concrete structures and the flaw detection inside the concrete specimens using the impact echo method, a non-destructive test to simulate the structures of school buildings. In this research, it was found that the impact echo method has great potentials in the application of the building structure maintenance and the repairing activities based on the accurate understanding of the existing school facilities that are being deteriorated. More over, school facilities has sometimes no structural design drawings available which NDT methods can contribute to detect the internal structural damages of existing building structures.
Wear Transitions of Tube-Support Materials for a Nuclear Steam Generator through Sliding Wear Test and Fretting Wear Test
Authors: Jeong Sung Hoon , Lee Byoung Jong , Lee Young Ze
Published: March 2009

Tubes in nuclear steam generators are held up by supports because the tubes are long and
slender. Fluid flows of high-pressure and high-temperature in the tubes cause oscillating motions
between tubes and supports. This is called as FIV (flow induced vibration), which causes fretting wear
in contact parts of tube-support. The fretting wear of tube-support can threaten the safety of nuclear
power plant. Therefore, a research about the fretting wear characteristics of tube-support is required.
This work is focused on fretting wear transitions from mild wear to severe wear of tube-support
materials by various loads and relative displacements. The transition is defined on the basis of the
changes in wear amount. To investigate the transition, the fretting wear tester was contrived to
prevent the reduction of relative displacement between tube and support by increasing the load. The
tube and support materials were Inconel 690 and 409 SS, respectively. The results show that the
transition of tube-support wear is caused by the changes of the dominant wear mechanism depending
on the applied load and the relative displacement.
Investigation on Multifrequency Eddy Current Testing Signal Analysis for Nondestructive Inspection of Steam Generator Tubes
Authors: Jung Hee Jun , Song Sung Jin , Kim Chang Hwan , Yoo Joo Young , Choi Young Hwan , Kang Suk Chull , Song Myung Ho
Published: March 2009

For inspection of steam generator tubes in nuclear power plants using eddy current testing,
it is a very crucial task to extract the flaw signal from signals compounded by flaws and supporting
structures. To perform such an important task, the multifrequency eddy current testing method is
widely adopted. In this study, we explore the performance of a linear mixing technique based on the
discrete cosine transform method by experiments. The results obtained using the DCT based method
agree very well to those obtained by commercial software demonstrating the effectiveness of the
approach.
The Evaluation of Material Degradation in Modified 9Cr-1Mo Steel by Electrochemical and Magnetic Property Analysis
Authors: Hyun Yang Ki , Won Soon Ho , Jang Jae Ho , Kim In Bae
Published: March 2009

Evolution of microstructure due to service exposure to high temperature has a strong effect
performance of heat resistant steels. In case of modified 9Cr-1Mo steels, precipitation of Fe2Mo-type
laves phases and coarsening of M23C6-type carbides are the primary cause of degradation of
mechanical properties such as creep resistance, tensile strength and toughness. Therefore creep tests
have been carried out on modified 9Cr-1Mo steels to examine the effect of aging and stress on the
creep strength. Additionally vibrating sample magnetometer is used to measure hysteresis loop.
Optically Encoded Smart Dust from DBR Porous Silicon
Authors: Lee Bong Ju , Kim Sung Gi , Sohn Hong Lae
Published: March 2009

Distributed Bragg reflector (DBR) porous silicons exhibiting unique reflectivity were successfully obtained by an electrochemical etching of silicon wafer using square wave currents. Optically encoded smart dust which retained optical reflectivity was obtained from DBR porous silicon film in organic solution by using ultra-sono method. The size of optically encoded smart dust was measured by field emission scanning electron micrograph (FESEM) and was about 500 nm to few microns depending on the duration of sonication. Investigation for the optical characteristics of smart dust revealed that smart dust could be useful for application such as chemical sensor for detecting organic vapors.
Assessment of Insulation Degradation in Rotating Machines
Authors: Kim Hee Dong
Published: March 2009

To assess the degradation of stator winding insulation in high voltage motor, a total of
forty-eight coils were manufactured. These coils are classified into five groups and there are twelve
strands in each coil. Four coil groups are artificial defects such as shorted turn of strand, internal
separation between conductor and insulation, large void within insulation and removal of
semi-conductive tape. The other coil group is normal. Before ac breakdown test was performed,
nondestructive test that included ac current, dissipation factor and partial discharge (PD) was done
with five coil groups. This paper carried out by comparing the results between nondestructive test and
ac breakdown test. When the values of ac current increase rate, tip-up dissipation factor and PD
magnitude are large, the insulation is occurred the deterioration. AC breakdown voltage is also low in
degraded insulation.
The Effect of Cavity on the Creep Fracture in P92 and P122 Steels and Its Detection by Intelligent Phased Array Ultrasound
Authors: Jeong Chan Seo , Bae Si Yeon , Lim Byeong Soo
Published: March 2009

The results of cavity inspection in uniaxial creep tests and creep crack growth tests were
compared to determine the cavity effect. The quantity of the cavities increased with increasing strain
and crack growth rate as stress and temperature were increased. This resulted in the change of da/dt vs
Ct. The increased rate in the number and size of the cavities in P92 steel with temperature was
relatively fast, resulting in the high rate of da/dt against Ct. In this study, to determine the
characteristics of defects in structure, the sub surface defects of P92 and P122 steels were
investigated by an intelligent phased array ultrasonic inspection system. The system was found to be
capable of detecting the creep crack length and the formation of cavities at the crack tip.
A Study on the Improvement of Durability of a Drive Plate by Investigating the Optimum Peening Intensity
Authors: Lee Kook Jin , Lee Jae Heon , Lee Tae Kun , Cheong Seong Kyun
Published: March 2009

In this paper the life extension of automobile drive plates will be investigated. The material
of specimen is a high carbon steel treated by shot peening, which is most important in the
manufacturing process of drive plates. The optimum shot peening condition was investigated by
changing the feeding speed and exposure time. The fatigue crack was observed at the fracturing
surface of specimens by using scanning electron microscopy (SEM). The distribution of compressive
residual stress induced by shot peening process was investigated by using X-ray diffraction. The
number of cycles to failure increases at the beginning of exposure. The life cycle decreases after
passing some interval of exposure, which will be called as optimum peening zone. Experimental
results show that the residual stress distribution and the number of cycles to failure of a drive plate are
greatly affected by peening process.
Analysis of Fatigue Crack Growth in Weld Specimen Using Three-Dimensional Cohesive Zone Model
Authors: Yang Seung Yong
Published: March 2009

Three-dimensional cohesive zone model was used to simulate the fatigue crack growth of a weld specimen. Damage accumulation was accounted for using a constitutive model. A surface along which the fatigue crack would grow was assumed along the symmetric plane of the specimen and the cohesive elements were applied on the surface. Tensile tests of weld and parent specimens were simulated by the finite element method. Results of fatigue crack growth for the weld and parent specimens were compared and the effect of changing a constitutive parameter on the fatigue crack growth behavior was also checked.
Effect of Local Strain on Low Cycle Fatigue Measured by ESPI System
Authors: Kim Kyung Su , Kim Ki Sung , Lee Kyung Ho , Kwon Jung Min , Park Seong Mo , Lee Nak Hoon
Published: March 2009

Low cycle fatigue cracks are mainly detected at discontinuous welded locations with high
stresses under repeated cyclic static loads due to cargo loading and unloading. Theoretical and
analytical methods have been used to estimate the local stress and strain, which affect the prediction
of fatigue life, but these methods have difficulties considering stress concentration at notched
locations and complicated material behavior of welded joints or heat affected zones. Electronic
speckle pattern interferometry(ESPI) system is a nondestructive and non-contact measurement system,
which can provide relatively accurate full field strain at critical positions such as welded zones and
structurally discontinuous locations. In this study, local strain was measured by ESPI system at the
welded cruciform joint, and then low cycle fatigue test was performed. Effect of local strain on low
cycle fatigue life was examined by using the strain value measured by ESPI. In order to verify the
relations between local strains and fatigue lives, after theoretical local strains and stresses were
calculated by using Neuber’s rule, the measured local strains corresponding the experimental fatigue
lives were compared with the results of Neuber’s rule and established codes of the British standard
and DNV curve.
Measurement for In-Plane Displacement of Tensile Plates with Through-Thickness Circular Hole and Partly Through-Thickness Circular Hole by Use of Speckle Interferometry
Authors: Kim Myung Soo , Baek Tae Hyun
Published: March 2009

Speckle interferometry with phase shifting method is used to measure in-plane
displacements of a steel plate with a partly through-thickness circular hole and a steel plate with a
through-thickness circular hole. The circular hole of steel plate with a partly through-thickness
circular hole is cut on the rear side of the plate, so that it is not visible during experiment. The speckle
noises of fringe patterns acquired by optical experiment are processed with image processing
algorithm of Gaussian blur and the in-plane displacements of the two specimens are obtained by use
of the processed fringe patterns. Also the in-plane displacements of the two specimens are calculated
by use of ANSYS. The results of optical experiments are quite comparable to those of calculation
with ANSYS.
A Characteristic of Scattering Patterns from Defect in a Rail
Authors: Lee Chong Myoung , Rose Joseph L. , Cho Youn Ho
Published: March 2009

Rail represents one of the most important means of transportation. Many nondestructive testing methods have been used to find defects in rail. The guided wave technique is the most efficient because of its long propagation characteristic along the rail. The wave structure of the rail cross-section for a particular loading condition of modes and frequencies is an important feature. The wave structures are examined at different modes and frequencies. The propagation scattering patterns of guided waves from various multiple defects in a rail are also studied using finite element method.
Thermographic Damage Detection of Ceramic Matrix Composites During Tension Testing
Authors: Lee Joon Hyun , Kim Jeong Guk
Published: March 2009

The fracture behavior of Nicalon fiber reinforced calcium aluminosilicate (CAS) glass-ceramic matrix composites (Nicalon/CAS) was investigated with the aid of a nondestructive evaluation (NDE) technique. Infrared (IR) thermography was employed for unidirectional Nicalon/CAS composite specimens. During tensile testing, an IR camera was used for in-situ monitoring of progressive damages of Nicalon/CAS samples. The IR camera provided the temperature changes during tensile testing. Microstructural characterization using scanning electron microscopy (SEM) was performed to investigate the fracture mechanisms of Nicalon/CAS composites. In this investigation, the thermographic NDE technique was used to facilitate a better understanding of the fracture mechanisms of the Nicalon/CAS composites during tensile testing.
Correlations between the Changes of Pain and Temperature by Infrared Thermography in Central Poststroke Pain
Authors: Kim Su Young , Lee Doo Ik , Kim Keon Sik , Kim Dong Ok , Choi Young Kyoo , Choi Do Young , Lim Sabina , Lee Jae Dong , Lee Yun Hoo
Published: March 2009

Central poststroke pain can occur as a result of lesion or dysfunction of the brain from
stroke, and may influence the autonomic nervous system to regulate the vasomotor activity which
could result in the lowered skin temperature. In order to assess CPSP objectively, seventy patients
with CPSP were evaluated as their pain with VAS pain score and the skin temperature of pain site by
infrared thermography before and after pain treatment. And evaluated correlation between changes of
temperature and VAS. The skin temperature of pain site was significantly lower than non-pain before
treatment and improved after treatment(p<0.05), in accordance with significant improvement of VAS
pain scores after treatment(p<0.05). And there was highly correlation between the changes of
temperature and VAS(p<0.05). Therefore, it is suggested that the infrared thermography is very useful
device for the evaluation of CPSP and its treatment.
NDT Analysis of Metal Materials with Internal Defects Using Active Infrared Thermography Method
Authors: Kim Won Tae , Choi Man Yong , Park Jung Hak
Published: March 2009

This study is aimed to analyze the thermal imaging patterns presented by infrared(IR) thermography at which the metal with internal defects are thermally heated. Through the knowledge of non-destructive testing which infrared thermography can be applied to detect the defects inside the materials, there are two materials experimented; one is stainless steel and the other is cast-iron. Thermally, each material of specimens is heated at the base of the material and kept with constant temperature, The artificial defects in the specimen are formulated. Under the shape and location of the defects, temperature profiles are also measured and validated using the computer simulation. It is concluded that the characteristics of thermal patterns obtained from IR thermography are consistent with those of measurement and computations.