bluuebunny/crossref_metadata_2025 huggingface dataset:
The Improvement of High Cycle Fatigue Properties of AC4CH Alloy with Shot Peening Treatment
Authors: Masaki Kiyotaka , Ochi Yasuo , Matsumura Takashi
Published: March 2009

In order to investigate the effect of SP treatment on the high cycle fatigue properties such as fatigue strength, crack initiation and propagation behaviors, rotating bending fatigue tests on shot-peening (SP) treated AC4CH aluminum alloy were carried out. The fatigue properties of the SP-treated material were compared with fatigue properties of the non-peened material, the hot isostatic pressure (HIP) treated material and the semi-liquid (SL) die casting material. the main conclusions obtained were, (1) The fatigue properties of SP-treated material is most excellent in all materials. (2) The fatigue life property of AC4CH alloys is significantly affected by fatigue crack initiation behavior. The reason why the SP-treated material has longer fatigue life than those of other material is that it has no cast defects near the surface by the effect of SP treatment. (3) The reason of
fatigue life improvement by SP treatment is decrease of fatigue crack propagation rate.
Treatment of Cut Slope and Analysis of its Reliability
Authors: Chen Jing Xi , Zhang Guang , Wu Haitao
Published: March 2009

This paper sums up the measures to treat cut slope in expressway and puts forward a new method to calculate the slope relability by the application of Dynamic Programming.
A Study on the Evaluation of Creep Degradation of High Temperature Pipeline Steel by Non-Destructive Test
Authors: Lee Sang Guk
Published: March 2009

In this paper, artificial creep degradation test and ultrasonic measurement for their creep degraded specimens (Cr-Mo alloy steel) were carried out for the purpose of evaluation for creep damage. Absolute measuring method of quantitative ultrasonic measurement for material degradation was established, and long-term creep degradation tests using creep life prediction formula were carried out. As a result of ultrasonic tests for crept specimens, we conformed that both the sound
velocity decreased and attenuation coefficient linearly increased in proportion to the increase of creep life fraction (fc). In frequency and noise analysis, it was conformed that the high frequency side spectra and central frequency components shift to low frequency band, and bandwidths decrease as increasing creep damage in backwall echo. And also, the ultrasonic noise linearly increased in proportion to the increase of creep degradation.
Degradation Evaluation of 2.25Cr-1Mo Steel Using Nondestructive Method
Authors: Park Jong Seo , Baek Un Bong , Kim Jeong Min , Nahm Seung Hoon , Ahn Bong Young
Published: March 2009

Several nondestructive evaluation methods were attempted for the estimation of the creep damage of degraded 2.25Cr-1Mo steel. The specimens of three different aging periods were prepared by an isothermal heat treatment at 430°C, 482°C, and 515°C. The effect of probe configuration on the electrical resistivity was studied. Single configuration method and dual-configuration method were utilized for measuring electrical resistivity. The electrical resistivity was determined by a standard DC four-point probe method at 24±0.5°C. Indentation test, magnetic characteristics test and ultrasonic test were carried out to investigate the correlation between the major characteristics and aging parameter. Unlike the electrical resistivity characteristics, ultrasonic attenuation coefficient and indentation characteristics did not show a relation to Larson-Miller parameter. However, a correlation between the electrical resistivity and aging parameter was identified, which allows one to estimate the extent of material degradation.
Pattern Classification of Acoustic Emission Signals during Wood Drying by Principal Component Analysis and Artificial Neural Network
Authors: Kim Ki Bok , Kang Ho Yang , Yoon Dong-Jin , Choi Man Yong
Published: March 2009

This study was performed to classify the acoustic emission (AE) signal due to surface check and water movement of the flat-sawn boards of oak (Quercus Variablilis) during drying using the principle component analysis (PCA) and artificial neural network (ANN). To reduce the multicollinearity among AE parameters such as peak amplitude, ring-down count, event duration, ring-down count divided by event duration, energy, rise time, and peak amplitude divided by rise time and to extract the significant AE parameters, correlation analysis was performed. Over 96 % of the variance of AE parameters could be accounted for by the first and second principal components. An ANN was successfully used to classify the AE signals into two patterns. The ANN classifier based on PCA appeared to be a promising tool to classify the AE signals from wood drying.
Experimental Study on the Infrared Information of Metal Specimen when Loaded
Authors: Wang Lai Gui , Wu Chunbin , He Feng , Wang Shu Hong
Published: March 2009

Metal materials especially steel or cast iron are used extensively in many types of
construction such as buildings, bridges, cranes, vehicles and so on, so detection or prediction of metal failure is very important, but deformation of metal material often deliveries heat energy which can be detected by infrared imager. The test specimen is installed between the two grips of the testing machine and then loaded in tension and in compression. The IR913A infrared imager is used to observe the deformation of metal specimen. The high-sensitive infrared thermal images of metal specimen in the different phase of deformation are obtained. The paper theoretically analyzes the
reason from the thermodynamics and plastic mechanics, the conclusions are drawn as follows: 1) When applying loads, temperature field on the surface of metal specimen is changing, the local rise of temperature is remarkable, this can be observed from the infrared thermal images. 2) From the infrared thermal images, rising temperatures are found in the regions of stress concentrations. 3) When the test specimen approaches to failure or appears fracture, there is a remarkable change that can be shown from the infrared thermal images with remarkable colors.
Quality Monitoring of Thermally Degraded Stationary Gas Turbine Blade Material by Surface Wave Technique
Authors: Byeon Jai Won , Kim C.S. , Song J.H. , Kwun S.I.
Published: March 2009

For the quality monitoring and reliable application of stationary gas turbine blade (vane), near surface damages in the isothermally degraded vein material (i.e., cobalt based superalloy) were characterized by ultrasonic surface wave technique. Surface wave velocity and attenuation were measured for the artificially degraded specimens at 1100°C, together with microstructural analysis and micro-hardness measurement. Surface wave velocity increased with thermal degradation time, which was attributed to the increasing depletion of solute chromium near the surface. Strong frequency dependence of surface wave velocity was observed in the specimens with surface depletion layer. Attenuation coefficient of surface wave increased with increasing degradation time. The potential of ultrasonic surface wave technique to assess near surface damages in vein material was discussed with an emphasis on the relationship between the microstructural damage and the governing principles of ultrasonic response.
An Active Piezo Array Sensor for Elastic Wave Detection
Authors: Lee Young Sup , Yoon Dong-Jin , Lee Sang Il , Kwon Jaehwa
Published: March 2009

This paper describes an array sensor of piezoceramic PZT discs with flexible covering layers, which is designed to detect surface elastic waves in structures, such as Rayleigh waves. The sensor is distinguished from conventional “passive” sensors for elastic waves detection because it
possesses an ability to actuate an “active” pulse. This indicates that the function of active pulse generation ensures the diagnosis of the structures, where the sensor attached or embedded into, can be accomplished in a smart way including an easy inspection of faults. Actually the sensor has been inspired from human sensory systems in order to apply for smart structure sensing. They utilized 6mm
diameter and 0.25mm thick PZT discs for the active array sensor. The performance of the sensor was demonstrated at various experiments of some metal and composite structures that the sensor can be applied for the health monitoring of the advanced smart structure system.
Characteristics of Patch Type Smart-Piezo-Sensor for Smart Structures
Authors: Yoon Dong-Jin , Lee Sang Il , Kwon Jaehwa , Lee Young Sup
Published: March 2009

Structural health monitoring (SHM) is a new technology that has been increasingly evaluated by the industry as a potential approach to improve the cost and ease of structural inspection. Piezoelectric smart active layer (SAL) sensor was fabricated to verify the applicability of finding cracks and conducting source location in a various materials. A crack detection and source location works were done in three kinds of test condition such as aluminum plates with crack for patch type SAL sensor, a smart airplane with embedding SAL sensor, and a concrete beam with real crack for practical application. From this experimental study, the evaluation algorithm for the arrival time delay and decrease of signal amplitude was suggested in this paper. Consequently, it was found that the SAL sensor and detection algorithm developed in this study can be effectively used to detect and
monitor damages in the both existing structures and new designed smart structures.
Fatigue Crack Propagation Behavior and Degradation Characteristics of STS316L by Nondestructive Evaluation
Authors: Park So Soon , Ahn Seok Hwan , Moon Chang Kwon , Nam Ki Woo
Published: March 2009

Structural health monitoring (SHM) is a new technology that has been increasingly evaluated by the industry as a potential approach to improve the cost and ease of structural inspection. Piezoelectric smart active layer (SAL) sensor was fabricated to verify the applicability of finding cracks and conducting source location in a various materials. A crack detection and source location works were done in three kinds of test condition such as aluminum plates with crack for patch type SAL sensor, a smart airplane with embedding SAL sensor, and a concrete beam with real crack for practical application. From this experimental study, the evaluation algorithm for the arrival time delay and decrease of signal amplitude was suggested in this paper. Consequently, it was found that the SAL sensor and detection algorithm developed in this study can be effectively used to detect and
monitor damages in the both existing structures and new designed smart structures.
Change of the Pulsed Eddy Current Signals by the Variation of the Thickness of an Aluminum Specimen
Authors: Lee Jeong Ki , Suh Dong Man , Lee Seung Seok
Published: March 2009

The conventional eddy current testing uses a sinusoidal signal with very narrow frequency bandwidth. Whereas, the pulsed eddy current method uses a pulse signal with a broad frequency bandwidth. This allows multi-frequency eddy current testing, and the penetration depth is greater than that of the conventional eddy current testing. In this work, the pulsed eddy current instrument was developed for evaluating the metal loss. The developed instrument was consist of the pulse generator generating the square pulse of maximum 40 V, the amplifier controlled to 52dB, the A/D converter of 16bit 20MHz, and the industrial personal computer for operating with Windows program. And, the probe for the pulsed eddy current was designed as the pancake type in which the sensing coil was located in the driving coil. The peak voltage did not linearly increase with the voltage of the step pulse. For the driving coil with inductance of 670µH, the peak voltage linearly increased with the step pulse voltage to 30V. But, for the other driving coils with the inductance of 1.7mH, 2.7mH, 3.6mH, 22mH, the peak voltage linearly increased with the step pulse voltage to 20V. The output signals of the sensing coil rapidly increased when the step pulse driving voltage was off, and the latter part of the sensing coil output voltage exponentially decreased with a time. The decrement value of the output
signals of sensing coil increased with the thickness of the aluminum test piece.
Elastic Wave Signal Characteristics of SiC Ceramics with Crack Healing Ability by Wavelet Analysis
Authors: Kim Jin Wook , Park B.W. , Ahn Seok Hwan , Nam Ki Woo
Published: March 2009

This paper reports for signal characteristics of before-and-after healing treatment SiC ceramics with crack healing ability. The elastic wave signals generated during the compress load by a Vickers indenter on the brittle materials were recorded in real time, and the waveforms of the individual signals were examined and classified based on their spectral characteristics. The compress loads were applied with the range from 9.8N to 294N. In a bulk SiC specimen, the AE signals occurred only when the load was compressive loading and unloading. But, in the after crack healing specimen of 294N only, even though the external compressive load was stopped and kept on holding constant load states, the AE signals occurred irregularly and continuously. The results of the WT and frequency analysis showed that these existed as the property of frequency in the limited range between 100kHz and about 200kHz. Three-point bending test was performed for the cracked and healed SiC specimens. Consequently the bending strength of the crack healed specimens was recovered completely, but most of the samples with the crack healed showed that the properties of the dominant frequency were comparatively lower than that of the bulk SiC samples. The classification of the wave signals can be used to develop algorithms for autonomous health monitoring systems of brittle
material structures.
Effect of Particle Size on Fracture Toughness of Spherical-Silica Particle Filled Epoxy Composites
Authors: Kwon Soon Chul , Adachi Tadaharu , Araki Wakako , Yamaji Akihiko
Published: March 2009

We investigated the particle size effects on the fracture toughness of epoxy resin
composites reinforced with spherical-silica particles. The silica particles had different mean particle diameters of between 1.56 and 0.24µm and were filled with bisphenol A-type epoxy resin under different mixture ratios of small and large particles and a constant volume fraction for all particles of 0.30. As the content with the added smaller particle increased, the viscosity of each composite before curing remarkably increased. We conducted the single edge notched bending test (SENB) to measure the mode I fracture toughness of each composite. The fracture surface with the small particle content exhibited more rough areas than the surface with larger particles. The fracture toughness increased below the small particle content of 0.8 and saturated above it. Therefore, near the small particle
content of 0.8, the composite had a relatively low viscosity and a high fracture toughness.
The Crack Growth Evaluation of A335 P22 Steels by Acoustic Emission
Authors: Song Gee Wook , Hyun Jung Seob , Chang Sung Ho , Kim Bum Shin
Published: March 2009

Acoustic emission (AE) technique was used to investigate fatigue crack growth on compact tension specimens of aging materials at room temperature. Test materials have been sampled steam pipe serviced the actual operation conditions for a long time in fossil power plant. The compact tension test specimens were subjected to load stress ratios of 0.33, 0.5, and 0.66. All the fatigue tests
were performed at a frequency of 1Hz. The test results indicate that acoustic emission counts show reasonable correlation with crack propagation rates for applied stress ratios. When the crack growth rates increase, AE’s counts and energies show increment. Also, the higher stress ratios, the faster crack propagation rates. Based on these relationships it may be possible to predict the remaining service life of fatigue-damaged steam pipes.
Structural Health Monitoring Systems for a Steel Structure Using an Ambient Vibration
Authors: Heo Gwang Hee , Lee Giu , Yun Hyun Do , Choi Man Yong , Lee Myoung Won
Published: March 2009

This study aims at identifying the structural dynamic characteristics using an ambient
vibration, and developing a health monitoring system which adopts damage detecting algorithms. One of the main problems for this system design is to measure long-time dynamic response signals and simultaneously estimate the structural dynamic properties. In order to be suitable for a long-time monitoring, we conduct an ambient dynamic testing for a 3-floor moment resistance steel structure and analyze structural dynamic characteristics using time domain estimation techniques. Also, a
damage detecting test is performed to evaluate damage state by various detecting algorithms (modal correlation method (MAC & COMAC), eigen-parameter change method). Finally, this paper suggests the optimal algorithms for the identification of the structural damage locations and damage quantities with all such comparisons. The algorithms presented in this paper prove to be applicable in structural health monitoring of structures.
A Study of Comparison on the Stress Intensity Factor of a High Polymer Material with Cracks, Holes and Inclusions
Authors: Sasaki Syuutei , Ezumie Tsutomu
Published: March 2009

In modern society, we can see various large structures such as large buildings, ships, bridges that have been constructed using metal, polymers and polymer alloys. Many other new materials are being developed and invented in the world. These materials are made on automatic line systems in factories. These are tested under the rigorous and sever conditions, and shipped on demand. After rigorous testing, however, materials often contain cracks, holes or inclusions. The intensity stress generates on top of the crack and may cause accidents. Holes or inclusions in the material have negative effects on the rigidity and the safety. Many researchers use the high polymer materil for the purpose of the analyzing about cracks, holes and inclusions. The crack, the empty hole and the inclusion become of one of the cause of the fracture and the accident. The authors think that the various problems about cracks, holes and includes are not studied enough. They tried to examine the relation ship of the details of stress intensity factor of the high polymer materials by means of the caustic method and the photoelastic method. This paper discusses the causes and effects of mutual interference of cracks, holes and inclusions in the materials.
Structural Health Monitoring of Composite Laminates by Using Embedded FBG Optical Fiber Sensors
Authors: Kim Won Seok , Kim Sang Hoon , Lee Jung Ju
Published: March 2009

In this paper, a new Structural Health Monitoring (SHM) technique for composite
laminates through the use of embedded FBG sensors is presented. This method monitors the ply stress states of a laminate and compares them with failure criteria continuously during structures’ service time. The ply stress state of each ply composing the composite laminate can be obtained by embedding three FBG sensors in the laminate based on the classical lamination theory. In this study
FBG sensor embedded graphite/epoxy composite laminate specimens were fabricated. With ply stress states being monitored, tension and fatigue tests were performed until laminates’ failure. Experimental results show that laminates experience fracture when the ply stress states are beyond the boundaries of failure criteria. Embedded FBG sensors had good fracture strain and reliability. Therefore, critical damage can be detected by the ply stress states which are close to the boundaries of failure criteria.
Real-Time Displacement Monitoring System for High Temperature Steam Pipe of Fossil Power Plant
Authors: Hyun Jung Seob , Song Gee Wook , Cho Sun Young , Lee Young Shin
Published: March 2009

Most domestic fossil power plants have exceeded 100,000hours of operation with the severe operating condition. Also, cyclic operation of the plant subjects the piping system to mechanical and thermal fatigue mechanisms and poor of defective support assemblies can impose massive loads onto the piping system and induce unstable piping displacement. In order to prevent the serious damage and failure of the piping system in fossil power plants, 3-dimensional displacement measurement system was developed for the on-line monitoring. Displacement measurement system was developed with LVDT and rotary encoder type sensors. This system was installed and operated on a real power plant successfully.
Contact Fatigue Life Prediction under EHL Contact
Authors: Kim Tae Wan , Lee Sang Don , Cho Yong Joo
Published: March 2009

In this study, the simulation of contact fatigue based on stress analysis is conducted under Elastohydrodynamic Lubrication (EHL) state. To predict a crack initiation life accurately, it is necessary to calculate contact stress and subsurface stresses accurately. Contact stresses are obtained by contact analysis of a semi-infinite solid based on the use of influence functions and the subsurface
stress is obtained using rectangular patch solutions. The numerical algorithm using newton-rapson method was constructed to calculate the EHL pressure. Based on these stress values, three multiaxial high-cycle fatigue criteria are used. As a result, the effects of EHL on contact fatigue life are calculated.
Ultrasonic Transmission Characteristics of Continuous Casting Slab for Medium Carbon Steel
Authors: Lee Jun Youn , Lee Soon Bok , Yi Jae Kyung
Published: March 2009

Until now, surface defects of continuous casting slab have been removed by the enforced surface scarfing to produce high quality steel materials. An evaluation technique for surface and internal defects of slab is required to enhance the production of medium carbon steels and acquire defect-map. Accordingly as a preliminary step, longitudinal wave testing and Rayleigh wave testing were carried out on slab specimens of medium carbon steel to get basic transmission characteristics of ultrasonic waves. This research provides as basic data for on-line defect estimation using a laser ultrasonic or EMAT in non-contact ultrasonic detecting techniques in future.
Inversion of Eddy Current Test Signals Obtained from Steam Generator Tubes
Authors: Kim Young H. , Song Sung Jin , Hur Jin Soo , Kim Eui Lae , Yim Chang Jae , Choi Young Hwan , Kang Suk Chull , Song Myung Ho
Published: March 2009

Eddy current testing (ECT) is widely used in in-service inspection as well as pre-service inspection of the steam generator (SG) tubes in nuclear power plant of pressurized water reactor type. The interpretation of ECT signals, however, is truly a difficult task so that the reliability enhancement of signal interpretation is strongly desired. An enhanced interpretation tools for ECT signals have been developed by the novel combination of neural networks and finite element modeling for quantitative flaw characterization SG tubes. A database was constructed using synthetic ECT signals generated by the finite element models and principal component analysis (PCA) was adopted in order to optimize the feature set of ECT signals. The improvement in the performances by the features with PCA and the excellent performance for the experimental ECT signals demonstrate the high potential of the developed inversion tools for reliable interpretation of eddy current signals. To explore the possibility of applying the developed approach in practical inspection, we developed an automated system (laboratory prototype) that can acquire experimental ECT signals from SG tubes and carry out the quantitative flaw characterization in a real time fashion by applying the approach developed in the present work.
Molecular Dynamics Simulation of Nanoindentation on Folded Chain Crystal of Polyethylene
Authors: Yashiro Kisaragi , Furuta Atsushi , Tomita Yoshihiro
Published: March 2009

Nanoindentation tests on a folded chain crystal of polyethylene are implemented with the molecular dynamics simulation. The orthorhombic crystal is made of the planar zig-zag chains and has the thickness of about 10nm. The ideal Berkovich indenter is plunged into upper surface of the crystal down to 2nm with the constant loading rate of 200m/s or 2000m/s. After the holding time of 1000fs at the maximum depth, the indenter is then pulled up with the same speed. The results are summarized as follows; a) The indentation of 2000m/s remains the residual depression while that of
200m/s recovers the hollow, b) No elastic component is found in the deformation under the both rate of 200m/s and 2000m/s, c) The crystal deforms statically under the indentation of 200m/s while that of 2000m/s shows delayed response.
Interaction of Mechanical Loading with Residual Stresses in Pressure Vessels
Authors: Hadidi-Moud Saeid , Truman Christopher E. , Smith David John
Published: March 2009

Assessment of the integrity of structures such as reactor pressure vessels is a critical issue in relevant industries. In a full integrity assessment, the presence of initial residual stresses (RS) needs to be taken into account. An initial RS field is introduced into a type 316 stainless steel cylindrical vessel with no defects and to one with a partial circumferential crack on its outer surface. Relaxation of RS following several proof load cycles, in form of internal pressure, applied to the vessel is explored using finite element simulations. It is found that the proof loading process generally relaxes the RS and is proved to be beneficial to both cracked and un-cracked vessels with or without the presence of initial RS. Interaction of residual stresses with warm pre-stressing is further investigated using A533B steel at room and low temperature subjected to axial loading. The results are compared
with similar analyses but with no introduction of an initial RS field to explore the interaction effects on fracture resistance, as well as the role of partial crack on the RS distribution / redistribution. The differences are discussed and illustrated.
UV-Irradiation Effects on Interfacial Strength between Thin Ceramic Film and Polymer Substrate
Authors: Omiya Masaki , Inoue Hirotsugu , Kishimoto Kikuo , Yanaka Masaaki , Ihashi Noritaka
Published: March 2009

This aim of this study is to investigate the effect of UV (Ultra Violet ray) irradiation on the interfacial adhesion strength between thin ceramic films and polymer substrate. Electric conductive films based on polymer substrates have attracted attention for use in flexible optoelectronic devices. It is well known that the mechanical properties of polymeric materials are degraded by UV irradiation.
Therefore, it is considered that the UV irradiation also affects the interfacial adhesion strength between ceramic coating and polymer substrate. The interfacial adhesion strength was measured by Multi-stages peel test. The results show that the interfacial strength decreases with UV irradiation. However, if a filter layer is installed between ceramic and polymer substrate, the degradation ratio becomes small.
Bending Performance Evaluation of Reinforced Aluminum Square Tube Beams Considering Local Buckling Behavior
Authors: Lee Sung Hyuk , Choi Nak Sam
Published: March 2009

Bending performances of aluminum square tube beams reinforced by aluminum plates under three point bending loads have been evaluated using experimental tests combined with theoretical and finite element analyses. Basic properties of aluminum materials used for initial input data of the finite element simulation were obtained from the true stress-true strain curves of specimens which had bean extracted from the Al tube beams. True stresses were determined from applied loads and cross-sectional area records of a tensile specimen with a rectangular cross-section by real-time photographing. True strains were obtained from in-situ local elongation measurements of the specimen gage portion by the multi-point scanning laser extensometer. Four kinds of aluminum tube beam specimens adhered by aluminum plates were employed. The bending deformation behaviors up to the maximum load described by the numerical simulation were in good agreement
with experimental ones. An aluminum tube beam strengthened by aluminum plate on the upper web showed an excellent bending capability.
A Study on the Demonstration Experiment of the Solar Hot Water Heater for Dwellings
Authors: Yang Dong Jo , Kim Jae Yeol , Han Jae Ho
Published: March 2009

The main purpose of this investigation was to evaluate the performance of the solar hot water heater for dwellings in a long period of time. In order to evaluate the performance, there were 11 solar hot water heaters located in Gwangju Chosun University examined for their performance in 30 month period as a long term. The specific monitoring systems of each heater were constructed for the demonstrational research and the data base associated to each monitoring systems were assembled for an extensive analysis for variety of data obtained. The demonstrational experiments were conducted through following the routine procedures of 4 specific tests (the replicated drainage test, the daily drain test, the daily agitation test, the short-term test). The performance evaluation was based on the performances in insulating and solar collecting and the experimental routines and the performance experiments had incorporated the consumers’ use and need of the product. The ultimate goals of this investigation were to achieve consumers’ trust on the products and to promote the extensive distributions of the solar hot water heaters. The demonstrational research of this investigation was to evaluate the performance of the solar hot water heater for the residents for a long period of time. This research will be continued extensively.
LCD Glass Cleaning by Atmospheric Pressure Glow Discharge Plasma
Authors: Cho Jung Hee , Kim J.W. , Kim K.S. , Lee W.Y. , Kim Sae Hoon , Choi Won Youl
Published: March 2009

We report on a novel method for the surface modification of indium tin oxide (ITO) in LCD glass by direct exposure to a dielectric barrier discharge (DBD) at atmospheric pressure and room temperature. To remove the organic contaminants from the surfaces of ITO film in LCD glass, the atmospheric pressure RF glow discharge plasma was used. Argon (Ar) and oxygen (O2) were used as the carrier gas and reactive gas, respectively. The addition of O2 gas to Ar decreased the contact angle of water and increased the surface cleaning rate due to the increase of oxygen radicals in the plasma. The chemical characteristics of ITO surface after the plama treatment were investigated using X-ray photoelectron spectroscopy (XPS), and new carboxyl group bond was produced. The contact
angle of 64° before the plasma treatment was decreased to 7° in the processing condition with oxygen flow rate of 50 sccm, treatment speed of 100mm/sec, and input power of 300W. These hydrophilic effect will be very useful in the manufacturing processes of LCD glass.
Mechanical Properties of Photosensitive Polyimide Film by Nanoindentation and Microtensile Test
Authors: Hur Shin , Hong Sung In , Shin Dong Kil
Published: March 2009

A free-standing photosensitive polyimide film with thickness of 10µm is fabricated with the different curing temperatures using a micro fabrication process. The microtensile specimens of a strip type are made to facilitate a tensile testing. The Young’s modulus and yield strength of photosensitive polyimide film are measured with various strain rates from 10-4 /s to 10-3 /s by using a microtensile test. Also, the hardness and Young’s modulus of polyimide films are obtained from nanoindentation test. Finally, the mechanical properties measured from microtensile test are compared with those from nanoindentation test.
The Charpy Notch Impact Test of X70 Pipeline Steel with Delamination Cracks
Authors: Yang Zheng , Huo Chun Yong , Guo Wanlin
Published: March 2009

The effects of thickness, notch orientation and delamination cracks on the impact
toughness of X70 pipeline steel are investigated experimentally by use of the instrumented Charpy impact tests at different temperatures. The couple effect of delamination cracks, thickness, notch orientation and temperature is discovered. The delamination cracks have certain direction, and their amount and size are related to the temperature and the specimen thickness. Though the delaminating
orientations of T-S and T-L specimen are not same, the reasons for both T-S and T-L specimen delaminating are that the weak interfaces in the specimens are pulled apart by the stress perpendicular to them. The delamination cracks can improve the actual impact toughness of X70 pipeline steel both T-L and T-S specimens. The effect of delamination cracks on the actual impact toughness changes with the thickness and the temperature. The couple effect of wall thickness, defect orientation and working temperature of pipeline must be taken into account in safe assessment of pipeline.
An Experimental Measurement of Toughness Locus for a Ductile Material
Authors: Kim Dong Hak , Lee Jeong Hyun , Kim Ho Dong , Kang Ki Ju
Published: March 2009

A toughness locus Jc-Q for a ductile steel, SA106 Grade C used in the main steam piping of nuclear power plants, has been experimentally evaluated. Along with the standard fracture test procedure for J-R curve, Q as the second parameter governing stress triaxiality nearby the crack tip is measured from the displacements nearby the side necking which occurs near the crack tip on the lateral surface of a fracture specimen. The displacements nearby the side necking are measured from
the digital images taken during the fracture experiment based on Stereoscopic Digital Photography (SDP) and high resolution Digital Image Correlation (DIC) software. The crack length is monitored by Direct Current Potential Drop (DCPD) method and the J-R curve is determined according to ASTM standard E1737-96. The effects of crack length, specimen geometry and thickness of specimen are studied, which are included in the toughness locus Jc-Q.
Evaluation of Ductile-Brittle Transition of Fracture Toughness by Material Degradation
Authors: Seok Chang Sung , Kim Hyung Ick , Kim Dae Jin , Bae Bong Kook , Kim Sang Pil
Published: March 2009

When huge energy transfer systems like nuclear power plants and steam power plants are operated for long times at high temperatures, mechanical properties change and ductile-brittle transition temperature increases by degradation. So we must estimate the degradation in order to assess safety, life expectancy, and other operation parameters. The sub-sized specimen test method using the surveillance specimen, and BI (Ball Indentation) method were developed for evaluating the integrity of metallic components. In this study, we will present the evaluation of the ductile-brittle transition temperature using the BI test and the sub-sized specimen test. The four classes of the thermally aged 1Cr-1Mo-0.25V specimens were prepared using an artificially accelerated aging method. The tensile test, the fracture toughness test, and the BI test were performed. The results of the fracture toughness tests using the sub-sized specimens were compared with those of the BI test. The evaluation technique of the ductile-brittle transition temperature using the BI test was also discussed. Our results show that the ductile-brittle transition temperatures rose as the aging time increased. We suggested that the fracture toughness results of the sub-sized specimen test and the IEF results of the BI test could be used in the estimation of the ductile-brittle transition temperature as material
degrades.
Evaluation of Fatigue Characteristic of a Real Waterworks Pipe
Authors: Seok Chang Sung , Park Jae Sil , Kim Hyung Ick , Lee Young Min , Cho Won Hak , Song Weon Keun
Published: March 2009

The fatigue characteristic of a material or a structure is derived from fatigue tests of
standard specimens. However, many researches have reported that test results of standard specimens are very different from those of real structures or components. One reason for this difference is the constraint effects according to the geometrical difference. Therefore, to calculate more accurate fatigue life, the constraint effect must be considered by comparing test results of standard specimens with those of real structures or components. Another reason for this difference is the surface condition. All surfaces of a standard specimen are polished to obtain similar conditions in a fatigue test. However, in a piping system, surface conditions of components are different from each other and very different from that of a standard specimen. Because fatigue life is effected by a surface condition, to evaluate the fatigue life of a piping system, fatigue tests must be conducted with a specimen extracted from a pipe with the same surface condition. The objective of this paper is to evaluate the fatigue characteristic of a real waterworks pipe by conducting fatigue tests with standard specimens and non-standard specimens of base metal and weld metal. Standard fatigue specimens and non-standard specimens were extracted from a steel pipe used in waterworks. Also, fatigue tests of pipes used in water service were carried out and then compared with those of standard specimens and non-standard specimens. From these results the relation between the S-N diagram of a specimen and that of a pipe specimen was evaluated.
A Study on Fatigue Properties of Sc Added Al 2519 Alloy
Authors: Baek Un Bong , Park Jong Seo , Chung In Hyun , Nahm Seung Hoon , Ma Young Hwa , Lee Yong Yun
Published: March 2009

The high cycle fatigue properties of two kinds of wrought Al 2519 alloys without and with scandium of 0.10% were investigated. The fatigue strength was determined at R = 0.1 under constant amplitude loading conditions in air. The alloy with scandium of 0.10% showed a little lower tensile yield strength and higher fatigue strength values. The fine grained Al-0.10Sc alloy exhibited a higher resistance against fatigue crack nucleation despite the lower yield stress in comparison to the coarse
grained Al 2519 alloy. The results can be explained mainly with the microstructural differences between both alloys. This results are due to the presence of coherent Al3 (Sc, Zr) precipitates and a very fine subgrain structure.
An Experimental Study on Fatigue Crack Propagation under Cyclic Loading with Multiple Overloads
Authors: Kim Kyung Su , Cho Dong In , Ahn Jae Wook , Choi Seung Bok
Published: March 2009

For many fatigue-critical parts of machines and structures, the load history under operating conditions generally involves variable amplitude loading rather than constant amplitude loading. An accurate prediction of fatigue crack propagation life under variable amplitude loading requires a thorough evaluation of the load interaction effects. In this study, fatigue tests under both constant and variable amplitude loading were carried out to investigate the overload effects on fatigue crack propagation of the notched specimens. Strain distributions around the crack tip before and after a tensile overloading were measured using the ESPI (Electronic Speckle Pattern Interferometry) system. The size of the plastic zone was determined from the measured strain distributions. The study proposes a crack propagation prediction model that incorporates the overload ratio effect. A comparative work for the overload ratio effect demonstrated that the prediction by the proposed model was in good agreement with the experimental results. The prediction of fatigue crack propagation including multiple overloads with the proposed model show also a good agreement with test results.
Assessment for Structural Stiffness and Fatigue Life on Self-Piercing Rivet of Car Bodies
Authors: Kim Min Gun , Kim Jin Hak , Lee Kun Chan , Yi Won
Published: March 2009

The highest structural stiffness of an SPR joint was exhibited in the specimen constituted with 5J32 and ASPH, and the lowest stiffness in that constituted with the single 5J32 combination. Even though the structural stiffness of an SPR joint specimen is roughly the same with another type of joint, the fatigue life is different according to sheet material and its thickness. The results of numerical analysis are nearly identical to those of experiments. Thus, it can be that FEM modeling in accordance with FEMFAT is effective in assessing the stiffness and fatigue life of SPR joints, and can be an alternative to experimental analysis.
A Study on the Monitoring of Nano Scale EHL Film Formation with Ultra Low Aspect Ratio
Authors: Jang Si Youl , Kong Hyun Sang
Published: March 2009

The measurement of ultra low aspect ratio fluid film thickness is very crucial technique both for the verification of lubrication media characteristics and for the clearance design in many precision components such as MEMS, precision bearings and other slideways. Many technologies are applied to the measurement of ultra low aspect ratio fluid film thickness (i.e. elastohydrodynamic lubrication film thickness). In particular, in-situ optical interferometric method has many advantages in making the actual contact behaviors realized with the experimental apparatus. This measurement method also does the monitoring of the surface defects and fractures happening during the contact behavior, which are delicately influenced by the surface conditions such as load, velocity, lubricant
media as well as surface roughness. Careful selection of incident lights greatly enhances the fringe resolutions up to ~1.0 nanometer scale with digital image processing technology. In this work, it is found that coaxial aligning trichromatic incident light filtering system developed by the author can provide much finer resolution of ultra low aspect ratio fluid film thickness than monochromatic or dichromatic incident lights, because it has much more spectrums of color components to be discriminated according the variations of film thickness. For the measured interferometric images of ultra low aspect ratio fluid film thickness it is shown how the film thickness is finely digitalized and measured in nanometer scale with digital image processing technology and space layer method. The developed measurement system can make it possible to visualize the contact deformations and possible fractures of contacting surface under the repeated loading condition.
The Failure and Falling of the Rock Mass in the Underground Mining
Authors: Zhao Wen , Wu Shiyue , Zhu Wan Cheng
Published: March 2009

In this paper, the process of failure and falling of the rock masses in the underground mining is studied; and the relationship between the processes of failure and falling of rock masses is proposed based on the rockmass strength theory. Research indicates that the failures of the rock and rock masses are probably not at all in common. Even though the rock masses go into the plastic condition, even to the extent that come into being in the failure, they do not surely fall. Hence, the mechanical properties of rock mass, especially after the failure, still need to be further researched. The laneway and the stope in the mining engineering are the temporary engineering, the load- carrying ability of the rock masses should be bought into play as far as possible, and therefore the stabilization during failure process is a significant for the supporting in the underground mine under safety prerequisite. Since 1 million m3 of the mined-out area is formed by mine for many year at Xishimen iron mine in China, and the gob roof is only 54m from the ground, the mined-out area is potentially dangerous to the underground mine. This paper analyzes the pattern of the stability and falling process in the mined-out area based on the theoretical analysis and numerical calculation, in order to obtains the falling criterion of the roof rock masses and stabilize the mined-out area. The predicted falling shape and range of the mined-out area is compared well with the in-situ observations. This contribution has also been popularized in many mines of China.
Nonlinear Vibration Characteristics of Fatigue Damaged Reinforced Concrete Structures
Authors: Kim Jin Ho
Published: March 2009

In this paper, nonlinear vibration techniques were applied to investigate stages of
progressive damage in three vibration isolation systems induced by dynamic loadings. Analytical models for reinforced concrete structures of three isolation systems were developed based on FEM with discrete crack concept. Vibration response spectra and the spectra of forces transmitted through the isolators were computed with respect to stationary dynamic loads. In addition, fatigue properties of concrete structures were examined for given materials’ properties and given geometries. The results indicated that the proposed isolation system 3 can improve fatigue resistance by extending fatigue life and changing the failure mode from shear to flexure.
Numerical Study of Elastic-Brittle Failure of Notched Openings in Rocks
Authors: Wang Shan Yong , Au S.K. , Lam K.C. , Tang Chun An
Published: March 2009

Borehole breakout is the process by which portions of borehole or tunnel wall fracture or spall when subjected to compressive stresses. The stress-strain characteristics of rock during loading and unloading confining pressure are studied firstly. To overcome the difficulties in analytical model studies, a numerical code, RFPA2D (Rock Failure Process Analysis), developed by CRISR, Northeastern University, China, is used to investigate the progressive failure of breakout around
tunnel. The heterogeneity of rock was also taken into account in the software. The numerical simulation reproduces the formation notch in rocks by the growth, interaction and coalescence of randomly distributed macrocracks. It is illustrated from the numerical simulated results that breakout direction of tunnel is parallel with the minor stress tensor in the plane perpendicular to the borehole axis. Specifically due to the inclusion of heterogeneity, some peculiarities are studied both in the evolution of fracture and the influence of borehole on the peak intensity of specimen as well as the AE event patterns.
Analytic Analysis of the Influence of Friction on the Temperature Field of Rock Specimens
Authors: Liu Xiang Feng , Wang Lai Gui , Yu Yong Jiang
Published: March 2009

When the coal (rock) specimens are tested with infrared, one can observe that the specimens’ temperature field is changing. Commonly, causes of the changes are due to specimens’ plastic deformation and crack extension. But many coherent documents indicate that most specimens even has high temperature field after the peak strength. This paper put a forward that the influence of friction between the fracture planes on the specimens’ temperature field could not be ignored. Meanwhile, the paper gives a simple friction model of two blocks,. In the model, the friction surface plays the different roles to the two blocks as moving heat source and fixed heat source respectively. Those different heat sources have different effect on the blocks’ temperature field. In the end, analytic solutions of temperature change at any point of two blocks that caused by friction are given.
Verification of Prediction Method for Electromigration Failure Using Angled Polycrystalline Line
Authors: Uno S. , Hasegawa Masuyuki , Sasagawa K. , Saka Masumi
Published: March 2009

Electromigration is one of the main damage mechanisms of interconnecting metal lines. Recently, a governing parameter for electromigration damage in passivated polycrystalline lines, AFD* gen, was formulated, and a prediction method for electromigration failure in passivated polycrystalline line was developed using AFD*
gen. This method requires only the film characteristics of the metal line and the application is not limited by a line shape and operating condition. The usefulness of the method has been shown using the straight-shaped lines. Using the ymmetrically and asymmetrically angled lines experiments are performed, and the line-shape dependency of the lifetime obtained by the prediction method is verified comparing with the results obtained from the experiment.