bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Confinement Condition on Particle Impact Damage in Soda-Lime Glass
Authors: Oh Sang Yeob , Shin Hyung Seop , Suh Chang Min
Published: March 2009

In order to investigate the effect of a confinement condition on the damage induced by a spherical impact, an experimental setup that can impact contact pressure to the specimen through a pressing die was composed. The steel and the WC balls in 3mm diameter impacted to the soda-lime glass specimen with dimension of 33×33×8m in the impact velocity range of 30m/s to 200m/s. Three different conditions are given for the impact damage investigation, which are the case without a pressing die and the cases of p=0MPa and p=200MPa with a pressing die. The stress distribution in the glass specimen by impacting the particle was also evaluated using MARC s/w system. The particle impact produced various kinds of the damage such as the ring and the cone cracks, the radial cracks and the craters. The contact pressure applied to the specimen changed stress fields in the
specimen. The damage zones of the specimen without a pressing die increased as the impact velocity increased. The damage extents in the specimen with the contact pressure of 200MPa were reduced as compared with the case of those without a pressing die.
Effect of Particle Impact Velocity on Cone Crack Shape in Ceramic Material
Authors: Oh Sang Yeob , Shin Hyung Seop
Published: March 2009

The damage behaviors induced in a SiC by a spherical particle impact having a different material and size were investigated. Especially, the influence of the impact velocity of a particle on the cone crack shape developed was mainly discussed. The damage induced by a particle impact was different depending on the material and the size of a particle. The ring cracks on the surface of the specimen were multiplied by increasing the impact velocity of a particle. The steel particle impact
produced the larger ring cracks than that of the SiC particle. In the case of the high velocity impact of the SiC particle, the radial cracks were generated due to the inelastic deformation at the impact site. In the case of the larger particle impact, the morphology of the damages developed were similar to the case of the smaller particle one, but a percussion cone was formed from the back surface of the specimen when the impact velocity exceeded a critical value. The zenithal angle of the cone cracks developed into the SiC decreased monotonically as the particle impact velocity increased. The size and material of a particle influenced more or less on the extent of the cone crack shape. An empirical equation was obtained as a function of impact velocity of the particle, based on the quasi-static zenithal angle of the cone crack. This equation will be helpful to the computational simulation of the residual strength in ceramic components damaged by the particle impact.
Experimental Study on the Wear Behavior of Nuclear Fuel Rod in High Temperature Water Environment
Authors: Lee Young Ho , Kim Hyung Kyu , Jung Youn Ho
Published: March 2009

In this study, the variation of spring characteristics with increasing temperature was
examined and the effect of their variations on the wear behavior of a nuclear fuel rod in both room and high temperature (300°C) water conditions was evaluated. From the results of the load-displacement tests, the spring stiffness was remarkably varied with increasing temperature. The results of the wear tests indicated that the wear damages are decreased at high temperature water when compared with the room temperature result. These results indicated that the removal mechanisms of wear debris at high temperature water are dependent on not only the formation of the wear particle layer but also on the changed contact conditions such as the contact length or area due to the stiffness drops.
High Temperature Creep, Fatigue and Creep/Fatigue Interaction Behavior of γ' Strengthened Austenitic Iron-Base Superalloy
Authors: Xie Xi Shan , Mao Zhengdong , Dong Jian Xin , Hu Yaohe
Published: March 2009

A new modified Nb-containing A-286 γ' strengthened austenitic Fe-base superalloy (14Cr- 28Ni-1.5Mo-1W-2Ti-Nb-Al) designated as GH871 in China characterizes with high level of tensile, stress rupture and low cycle fatigue properties at 650°C. However, the stress rupture ductility is low and the crack propagation rates at 650°C creep or creep/fatigue interaction conditions are high. For ductility and crack propagation behavior improvement vacuum melted GH871 can still keep its high
strength level, also raise stress rupture ductility and simultaneously to decrease crack propagation rates at 650°C. Our results support GH871 to be used as a disk material in high temperature industry.
On the Creep Fracture Toughness of 2¼Cr1Mo Steel
Authors: Xuan Fu Zhen , Tu Shan Tung , Wang Zheng Dong , Gong Jian Ming
Published: March 2009

To assess the failure risk of high temperature structures, it is essential to obtain the creep fracture toughness of materials. In the present paper, Creep crack growth (CCG) tests for 2¼Cr1Mo steel have been carried out by utilizing the side grooved compact tension (CT) specimen and direct current (DC) electrical potential technique. The material parameter of creep fracture toughness, c mat K ,
were obtained from analysis of 11 CCG tests at temperatures of 500 and 565oC. It has been found that for 2¼Cr1Mo steel c mat K decreases with increasing time and increases with elevating temperature. For this reason, the value of c mat K at lower temperature or longer service time can be used to extract a conservative result in the high temperature defect assessment where the accurate value of c mat K is
unavailable. It is also validated from this test that the proposed formula by Ainsworth et al can be adopted in practice.
Experimental Study of the High Temperature Mechanical Behaviors of TLP Bonding of Two Ni-Base Single Crystals
Authors: Li T. , Wang Qing Yuan , Wang Ai Qin , Wen Z.X. , Yue Zhu Feng
Published: March 2009

In this paper, the mechanical behavior of Ni-base single crystals joint created by TLP bonding is presented. Experimental study has been performed on the TLP single crystal under loading conditions of static uniaxial tension, creep and Three-points-bending (T-P-B) at temperature of 850 °C. Specimens made of the base material, Ni-base single crystal specimens without bonding, were also tested under the same loading conditions. The mechanical behaviors of TLP single crystal is compared to the behaviors of base material. It was found that the static strength of the TLP specimens with the boundary normal to the tensile direction was 63% of the strength of the base material. The creep strength and the fracture ductile strength was more than 57% and 55% of that of the single crystal base material, respectively. The macro and micro graphs of fracture surfaces of specimens indicated that the fracture modes of the samples were brittle fracture.
Suggestion of the Delamination Aspect Ratio in GLARE
Authors: Kim Cheol Woong , Song Sam Hong , Oh Dong Joon
Published: March 2009

The applicability of GLARE is restricted due to the frequent delamination of different
materials at interlaminar. The previous researches showed that the major parameter to control the delamination of GLARE was a crack (a). On the other hand, it was also shown that a delamination width (b) could strongly effect on the delamination behavior. Therefore, the aim of this research is to define the delamination behavior using the above correlation. In conclusions, it was shown that the delamination aspect ratio (b/a) was slowly decreased and the delamination area rate (ADR) was increased as the normalized crack size (a/W) was increased. The effect of the delamination shape was strong at the beginning of the cyclic loading but it was gradually diminished.
Influence of Material Composition on Mechanical Properties and Fracture Behavior of Ceramic-Metal Composites
Authors: Tohgo Keiichiro , Kawaguchi Takayuki
Published: March 2009

In order to estimate distribution of mechanical properties and fracture toughness in
ceramic-metal functionally graded materials (FGMs), mechanical properties and fracture behavior have been investigated on non-graded ceramics-metal composites which correspond to each region of FGMs. The materials are fabricated by powder metallurgy using partially stabilized zirconia (PSZ) and stainless steel (SUS 304). Vickers hardness, Young’s modulus and bending fracture strength
were examined on smooth specimens. The Vickers hardness of the composites continuously decreases with an increase in a volume fraction of SUS 304 metal phase, while the Young’s modulus and fracture strength exhibit low values in the composites with balanced composition of each phase. This suggests that the interfacial strength between the ceramic and metal phases is very low. Fracture toughness tests are conducted by three-point-bending on rectangular specimens with a sharp edgenotch. In contrast with the Young’s modulus and fracture strength, the fracture toughness obtained for the composites increases with an increase in a volume fraction of SUS 304 metal phase. The fracture toughness of the composites is slightly lower than that obtained previously by stable crack growth in a PSZ-SUS 304 FGM. The difference in fracture toughness between the composites and FGM seems to be attributed to the residual stress created during fabrication of the FGM.
Electro-Active Papers for Remotely-Driven Smart Actuators
Authors: Kim Jae Hwan , Jung Woo Chul , Song Chun Suk
Published: March 2009

This paper introduces the concept of remotely-driven smart actuator utilized by
electro-active paper (EAPap). The feature of remotely-driven smart actuator offers unique performance and application capabilities and exploit many of these unique capabilities. Since the microwave-driven actuator does not require carry-on-battery, ultra-lightweight, and distributed micro size actuators can be made. A dipole rectifying antenna (rectenna) array receives the microwave and converts it into a DC power. Recently, cellulose based paper has been came across as an lectroactive paper (EAPap) material so as to be used as artificial muscles for biomimetic insects. Since the power requirement of EAPap is less than the safety limit of microwave power in air, the EAPap actuators can be driven by wireless microwave power. This idea is useful for specific applications that require multifunctional capabilities such as smart skin, ultra-lightweight space structures, micro robots, flapping wing for insect-like flying objects and smart wall paper as well. Current research status along with its issues is addressed including a hybrid actuator of EAPap and conducting polymers that will enhance the performance of the actuator.
A Horizontal Vibration Wave Model for High Speed Elevators
Authors: Gang X.Y. , Yao Zhe He , Chen Zi Chen
Published: March 2009

Horizontal vibration has critical influence upon elevators’ ride quality. Based on the
wave theory of one-dimensional string vibration, a horizontal vibration wave model is built to simulate the dynamic performance of a high speed elevator system. Through coordinate transformation, Galerkin’s method is used to discretize the governing partial differential equations into a dumped-mass system, which can be solved effectively with classic methods. Numerical results show that the horizontal vibration behaviors are closely interconnected with the location, velocity and acceleration of elevator cab.
Axial Collapse Characteristics of Aluminum/CFRP Compound Circular Tubes
Authors: Cha Cheon Seok , Lee Kil Sung , Kim Seung Hoon , Chung Jin Oh , Yang In Young
Published: March 2009

Aluminum or CFRP (Carbon Fiber Reinforced Plastics) tube subjected to axial loading sustains load, and absorbs energy during axial collapse. The aluminum tube absorbs energy by stable plastic deformation, while the CFRP tube with higher specific strength and stiffness than those of the aluminum tube absorbs energy by unstable brittle failure. To achieve a synergy effect by combining the two members, aluminum/CFRP compound tubes were manufactured, which are composed of aluminum tubes wrapped with CFRP outside aluminum tubes with different fiber orientation angle of CFRP and number of plies. The axial quasi-static collapse tests were performed for the tubes. The collapse characteristics of the tubes were compared with those of respective aluminum tube and CFRP circular tube. Test results showed that the collapse of the aluminum/CFRP tubes complemented unstable brittle failure of the CFRP tube due to the ductile characteristics of the inner
aluminum tube. The collapse modes and the absorbed energy were influenced by the fiber orientation angle of CFRP and the number of plies. The absorbed energy per unit mass, which is in the light-weigh aspect, was higher in the aluminum/CFRP compound tube than in the aluminum tube or the CFRP tube alone.
Evaluation of the Fracture Characteristics with Thermal Aging on Dissimilar Welds in Reactor Coolant System
Authors: Kwon Jae Do , Woo Seung Wan , Choi Young Hwan
Published: March 2009

A dissimilar weld zone exists between the pipe and nozzle in a primary reactor cooling system (RCS). Thermal aging is observed in cast stainless steel, CF8M used in a pipe as the RCS is exposed for a long period of time to a reactor operating temperature between 290 and 330°C. No effect is observed in low-alloy steel. SA508 cl.3 is used in a nozzle. The artificially accelerated aging specimens are prepared to maintain for a temperature of 430°C for 300, 1800, and 3600hrs, respectively. Then, various mechanical tests such as hardness, tension, impact test, are performed in
virgin and aged specimens in order to determine the existence of dissimilar weld zones. The specimens for elastic-plastic fracture toughness tests are prepared for one type, where a notch is created in the heat affected zone of CF8M. From the experiments, it was found that J-integral values decrease as age increases.
Adhesion Analysis Considering Surface Energy and Surface Stresses
Authors: Koguchi Hideo
Published: March 2009

A new formulation for an adhesive force between a substrate and an indenter is presented. The boundary condition taking into account surface stresses is used for the present analysis. The surface stress is originated from surface energy. A paraboloidal indenter is pressed to the substrate, and then adhesion occurs between both surfaces. Surface energy and surface stress will vary at the adhesion surface, and then the surfaces deform in a concave way. An attractive force occurs to keep the contact of two adhesion surfaces. In the present paper, an effect of surface stress on the adhesive force will be clarified.
Fatigue Life Evaluation of Vehicle Wheel Bolts under Random Loading
Authors: Choi Young Woo , Noh Byeong Wook , Ham Kyung Chun , Bae Sung In
Published: March 2009

The fatigue life of hexagon head and socket head bolts, attached to vehicle a wheel, is assessed and the estimation of the residual life of existing bolts in vehicle wheel is investigated. Field- measured load histories were applied in this test. Tensile tests and fatigue tests were performed to evaluate the effect of tightening torque and to obtain the basic experimental data. A three-dimensional finite element analysis was also performed to evaluate the local stress fields. Miner’s rule was used to predict the fatigue life of bolts. The results indicate the prediction of fatigue life of the bolts was in good agreement with the real life of vehicle wheel bolts in this test.
Automotive Component Fatigue Life Estimation by Frequency Domain Approach
Authors: Jung Do Hyun , Bae Sung In
Published: March 2009

Time domain approach with S-N approach and local strain approach were used for
fatigue life estimation. But these days, using PSD (Power Spectral Density) method is highlighted, because of short amount of time in measurement and analysis. Especially, PSD method is useful for analysis of fatigue failure which is caused by vibration damage, also FRF (Frequency Response Function) is useful for efficient prediction of fatigue life when the same product is employing
different motor vehicle or test condition. In order to estimate fatigue life of compressor for air conditioning, time domain analysis and frequency domain analysis were performed and the results were compared. As a result, results of analysis in frequency domain and time domain were similar. With this, there is recognition of decreasing the period of measuring and analysis in PSD analysis.
Moreover, in case of FRF pursued of a part, using FRF is applicable at fatigue life prediction in different testing condition. There was investigated an analysis method with curtailed analysis period by FRF.
Determination of the Deposition Characteristics and Luminance Decay Mechanisms in OLED and their Implications in Reliability Assessment
Authors: Lee Kwang Ki , Kim Tae Won
Published: March 2009

OLED has many advantages such as possibility to make micro size, tiny driving power, and fast response time with high resolution. However, significant commercial level problems are being recognized resulting from the damage of emitting layer, degradation of organic layers, and generation of dark spot. It is therefore necessary to overcome the problems for the development of high performance products. Deposition characteristic associated with the materials failure in OLED has been determined, firstly, by means of the analysis of the surface morphology and roughness of thin film. Physical vapor deposition technique was employed to develop test specimens, and atomic force microscopy has been used to identify the uniformity of emitting layer. In addition, optimal control set enabling the roughness of thin film surface to be minimized is presented, and the results obtained are compared with the experimental data. Generally good agreement has been achieved. It is known that the luminance decay mechanisms are directly related to the reliability of finished products, and thus further investigation has been carried out using the luminance decay curves. As shown by the results, the luminance decay may be divided into two major components during the failure processes. One is simple exponential during operation and the other is rapid decline in the initial stages of operation. It can be thought that the simple exponential decline is related to a chemical degradation of Hole Transport Layer, whereas the rapid decline is probably due to the generation of an internal electric field.
A Study on Procedures of the Accelerated Life Testing for Hose Assemblies
Authors: Lee Y.B. , Kim Hyoung Eui , Park J.H. , Ko J.M.
Published: March 2009

There are several types of life test method for hose assemblies. The two major tests used for hose assemblies are impulse test and burst test. And magnification adjustment of impulse pressure, heating of testing oil and repetitive motions of bending and straightening of testing hose are also performed for accelerating the life. According to the manufacture process of hose and swaging process of fitting, there is a difference in the life of hose assemblies from minimum 7 times to maximum 40 times during the life test in the same functioning condition. Like this, the life test of
hose which has a wide scope of life distribution gives a problem that observation should take a long time to find out the existence of the bursting from the beginning of the test to the completion of bursting of hose assemblies. Therefore, this research proposes a process of concentrating on the defective section of hose assemblies and maximizing the life acceleration by giving ‘Knockdown stress’ to hose assemblies just until before the hose assemblies get out of order.
Effect of Shock Wave on Reliability of Buried Pipelines
Authors: Lee Ouk Sub , Kim Dong Hyeok
Published: March 2009

The effects of varying distribution type of random variables and environmental,
operational, and design random variables influenced by a shock wave caused from various origins on the failure probability are systematically investigated using the first order reliability method (FORM) for buried pipeline. It is found that the failure probability of the buried pipeline increases with faster P-wave velocity and slower S-wave velocity. The failure probability is estimated to be the largest for the Weibull distribution and the smallest for the lognormal distribution. A set of similar values of the failure probability for the normal distribution and lognormal distribution are noted. The normalized margin is defined and estimated. Furthermore, the normalized margin is used to predict the failure probability simply by using the fitting lines between the failure probability and the normalized margin.
Interference Effect of Interaction Cracks Investigated by Photoelastic and Caustics Methods
Authors: Ezumie Tsutomu , Ueno Kenya
Published: March 2009

The crack, which occurs because of fatigue, should often consider not only the single crack but also plural cracks occurring. In this paper, the material strength when two or more cracks occurred because of fatigue etc. was examined by calculating stress intensity factor K value by using caustics method and the photoelasticity. In general, plural cracks are known KI value decreases compared with the single crack. Therefore, the influence on K value was experimentally examined from the point of the distance between the cracks, the angle, and the crack length and the mode change. As a result, KI value influences destruction in plural in exist only mode I and the mixed mode of mode I and mode Ⅱ like this research cracks. When the crack length becomes long if the distance between the cracks narrows, the decrease of KI value grows. In addition, it has been understood that the decrease of KI value is influenced by a/w on the boundary of d/a=1 (the distance between the cracks is equal to the crack length).
Determination of the Young's Modulus and Loss Factor by Acoustic Bending Vibration Methods
Authors: Shin Su Hyun , Lee Yong Bong , Jung Sung Soo , Lee Doo Hee
Published: March 2009

A new acoustic bending vibration method of determining the resonance frequency,
Young’s modulus and loss factor applicable for both metallic and non-metallic materials is proposed. Measurements were conducted by using both conventional electromagnetic excitation method specified by ASTM E 756 and ISO 6721 and our method for conductive metallic specimen of stainless steel and non-metallic polypropylene specimen. Difference in the mechanical properties observed between both methods is attributed to the presence of a metal disk attached to the non-metallic sample for electromagnetic. However, the good agreement between the results obtained by both methods for the metallic sample ascertains the reliability and advantages of the method.
Buckling Fracture of Two-Dimensional Carbon-Fiber Reinforced Carbon-Matrix Composite
Authors: Ishihara Masahiro , Yamaji Masatoshi , Baba Sinichi , Hanawa Satoshi
Published: March 2009

Due to excellent high temperature resistivity on the strength, carbon fiber reinforced carbon matrix composites are thought to be one of attractive materials in a nuclear engineering field, e.g. the application to control rod sheath and so on in high temperature gas-cooled reactors as well as plasma facing components in fusion reactors. Prevention of the buckling fracture is placed as one of key subjects in the component design of C/C composites. The buckling fracture test was, therefore,
carried out using 2-dimensional C/C composite (2D-C/C composite), and fracture surfaces were observed by SEM. From the buckling fracture test, it was found that there are three kinds of fracture modes; i.e. delamination fracture mode of fiber bundles at low aspect-ratio region, shear fracture mode of fiber bundles at middle aspect-ratio region and shear fracture mode of fiber bundles accompanying by fiber buckling at high aspect-ratio region.
Image Distortion Compensation by Using a Polynomial Model in an X-Ray Digital Tomosynthesis System
Authors: Kim J.Y. , Yoon J.S.
Published: March 2009

X-ray technology has been widely used in a number of industrial applications for monitoring and inspecting inner defects which can hardly be found by normal vision systems as a ball grid array (BGA) or a flip chip array (FCA). Digital tomosynthesis (DT) is one of the most useful X-ray cross-sectional imaging methods for PCB inspection, and it usually uses an X-ray image intensifier.
However, the image intensifier distorts X-ray images severely both of shape and intensity. This distortion breaks the correspondences between those images and prevents us from acquiring accurate cross-section images. Therefore, image distortion compensation is one of the most important issues in realizing a DT system. In this paper, an image distortion compensation method for an X-ray DT
system is presented. It is to use a general distortion polynomial model on two dimensional plane that can cope with arbitrary, complex and various forms of distortion. Experimental results show a great improvement in compensation speed and accuracy.
Acoustic Emission Technique for Detection of Corrosion-Induced Wire Fracture
Authors: Youn Seok Goo , Cho S.K. , Kim Eun Kyum
Published: March 2009

There is currently a need to evaluate the non-destructive techniques that are used to detect the fracture of stressed steel wires in grouted post-tensioned concrete bridges. Although continuous acoustic emission (AE) monitoring technique has been developed to detect wire breaks in unbonded tendons, it is not established as the on-site monitoring tools for grouted post-tensioned concrete bridges. In this study, AE measurements were conducted to detect corrosion-induced wire fractures
inside a grouted post-tensioned beam. The test beam was drilled with 5mm drill bit to expose individual wires and a reservoir filled with corrosive solution of NaCl and NaOH was formed on the side of the beam. During the experiment, the corrosion site was anodically polarized to + 200mV using a potentiostat and it was continuously monitored and the data obtained were processed with an AE monitoring system. The outcome of this research shows that the continuous AE monitoring system successfully identified and located an individual corrosion-induced wire fracture in a fully grouted post-tensioned concrete beam.
An Automated System for Detection of Through-Wall Cracks in Racks in Steam Generator Tubes
Authors: Song Sung Jin , Kim Chang Hwan , Lee Deok Hyun , Choi Myung Sik , Hur Do Haeng , Han Jung Ho
Published: March 2009

Through-wall axial cracks occurred by primary water stress corrosion are one of the serious defects in steam generator (SG) tubes (made of alloy 600) in pressurized water reactors. Therefore, it is necessary to detect and size them by eddy current testing (ECT) conducted during in-service inspection of SG tubes. To address this issue, it has been recently proposed an effective method, namely „M-shape profile“ approach, which relies on the difference in the amplitude between the pancake and plus point coils in a MRPC probe. Even though the M-shape curve approach is straightforward in principle, it requires time-consuming data processing if performed by human operators. In order to get rid of this tedious task, an automated system is developed in the present work. This paper addresses the principle of the M-shape approach together with the automated system and its performances for the detection of natural axial cracks in SG tubes. The results observed in the present work demonstrate the high potential of the developed system as a very promising tool for detecting through-wall cracks in many practical field applications.
Mode Tuning of Guided Wave in a Seamless Stainless Steel Tube Using an Array Transducer
Authors: Kim Young H. , Song Sung Jin , Park Joon Soo , Kim Jae Hee , Eom Heung Seop
Published: March 2009

Ultrasonic guided waves have been widely employed for the long range inspection of
structures such as plates and pipes. In ultrasonic guided waves, however, there are numerous modes with different wave velocities, so that the generation and detection of the appropriate wave mode of the guided wave is one of key techniques in the application of guided waves. In the present work, mode tuning using an array transducer was investigated with hardware implements. For this purpose, 8-channel ultrasonic pulser and their controller which enables sequential activation of each channels with given time delay were developed. Transmitter tuning, group velocity measurements, reciver tuning, mode identification and long range transmission testing were carried out. As a result, the selective tuning of wave mode can be achieved by changing the time interval between adjacent elements of an array transducer.
Nondestructive Evaluation of Welding Residual Stress in Power Plant Facilities Using Instrumented Indentation Technique
Authors: Choi Yeol , Lee Yun Hee , Jang Jae Il , Park Sang Ki , Kim Kwang Ho , Seo Yang Won , Kwon Dong Il
Published: March 2009

The weld joints in power-plant pipelines have long been considered important sites for safety and reliability assessment. In particular, the residual stress in pipeline weldments induced by the welding process must be evaluated accurately before and during service. This study reports an indentation technique for evaluating welding residual stress nondestructively. Indentation load-depth curves were found to shift with the magnitude and direction of the residual stress. Nevertheless,
contact depths in the stress-free and stressed states were constant at a specific indentation load. This means that residual stress induces additional load to keep contact depth constant at the same load. By taking these phenomena into account, welding residual stress was obtained directly from the indentation load-depth curve. In addition, the results were compared with values from the conventional hole-drilling and saw-cutting methods.
A Study on the New Static Photoelastic Experimental Hybrid Method
Authors: Hawong Jai Sug , Teche Konstantin
Published: March 2009

In photoelastic experimental method, until now, we have used the Newton-Raphson
numerical method in analysis of photoelastic experimental data such as the non-linear least square method for the photoelastic expreriment. We used the Hook-Jeeves’ numerical method in stead of Newton-Raphson numerical method for the non-linear least square method for photoelastic experimental method. The new photoelastic experimental hybrid method, that is, the photoelastic experimental hybrid method with Hook-Jeeves’ numerical method has been developed in this
research. Applying the new photoelastic experimental hybrid method to stress concentration problems and plane fracture problems, it’s validity was assured. The new photoelastic experimental hybrid method is more precise and stabler than the photoelastic experimental hybrid method with Newton- Raphson numerical method (the old photoelastic experimental hybrid method)
Evaluation of Elastic and Creep Properties of Perforated Materials by Finite Element Analysis Imposing Periodic Boundary Conditions
Authors: Chung Il Sup , Chai Young Suck
Published: March 2009

In the analysis of materials containing regularly placed in-homogeneities, the evaluation of homogenized properties is an important issue. Common procedure for the homogenization is to define a unit cell, load it somehow, and investigate its structural response. A periodic variation of strain appears when the periodically heterogeneous material is under uniform macro-stress, and therefore, the implementation of this characteristic behavior would be essential to the material characterization based on a unit cell analysis. With the method proposed here, conventional finite element analysis tools can be used with no modification, and it is applicable to the skew-arrayed in-homogeneity problems. The orthotropic elastic and creep properties of materials with voids are examined, and the accuracy and effectiveness are demonstrated.
Thermal Stress Analysis for Air Inlet Part of Ramjet
Authors: Koo Song Heo , Lee Young Shin , Kim Jae Hoon , Kim S.J. , Choi Young Jin
Published: March 2009

The purpose of this study is to estimate structural characteristic for air inlet part of ramjet in condition of flight at 12-15km height. Because air inlet part of ramjet is heated up to 700oK, high temperature properties such as Young’s modulus, thermal expansion coefficients and thermal conductivity coefficients are applied to the analysis. The analysis of transient temperature and thermal stress was performed by the finite element method with nonlinear code ABAQUS. The analysis was performed using several thermal coefficient and material properties to select preliminary design model for flight condition. Thermal boundary conditions were applied at ramjet inlet part until 0.01sec. The results of the analysis recommend tendency of thermal stress and temperature distribution. These are useful to select the structural material and to determine shape of air inlet part which satisfy the structural design safety.
Computer-Aided Static and Dynamic Properties Design of the Frame of Electrical Slag Founding Furnace
Authors: Qu Li Gang , Li Jian Hui , Gao Hang
Published: March 2009

The double-vertical-column frame component, 8780mm high, is the key structure of
Electrical Slag Founding Furnace (ESFF). Due to its structural complexity and crucial functional role in the entire equipment, the frame structure is actually the most sensitive part of cost-effective manufacturing. Properties design, in which both static and dynamic properties are analyzed in order to meet the functionality requirement, is widely believed as important as other production processes, such as requirement identification, conceptualization, DFM and so on. And its deterministic role in cost effective manufacturing has been discussed in many historical literatures. Finite Element Analysis (FEA), one of most powerful engineering tool, has long been employed in designing of the frame component aiming to reduce computational time and improve computational precision, either
in presence of separated tool or as an integrated utility in CAD systems, for a long time. However seamless integration FEM into Computer-Aided-Design is still a challenging topic and one of the bottlenecks of cost-effective design recognized by scientists in the past. Based on a 3D solid model created with the CAD-system-compatible software SolidWorks, Finite Element Analysis (FEA) of the Furnace frame structure was carried out, which provided easily utilized data for the successive manufacturing processes as well as near-instantaneous feedbacks to designing process.
Degradation Evaluation of the Gas Turbine Hot-Gas-Path Component
Authors: Jung Jine Sung , Chang S.Y. , Yoo Keun Bong , Song Gee Wook , Kang Min Sung , Kim M.T.
Published: March 2009

Degradation of the gas turbine hot-gas-path components, the 1st stage blades and vanes, serviced for a period was evaluated by measuring the mechanical properties. For this, tensile and impact tests on these gas turbine parts were performed. Microstructure of the substrate and coating layers were also observed. The mechanical properties of the serviced blades were degraded by about 30% comparing with those of unused ones. In terms of the microstructure, the dissolution of the secondary g’ phase and subsequent coarsening of precipitates were observed in the substrate. And the interdiffusion zone near the coating layer was disappeared.
Application and Standard Error Analysis of the Parametric Methods for Predicting the Creep Life of Type 316LN SS
Authors: Kim Woo Gon , Yoon Song Nam , Ryu Woo Seog
Published: March 2009

To predict the creep-rupture life of type 316LN stainless steels which are major structural components of liquid metal reactors, a number of creep-rupture data were collected through literature survey and experimental data of KAERI. Using the data, the creep-rupture life was analyzed by means of the Larson-Miller, the Orr-Sherby-Dorn and the Manson-Haferd parametric methods. Polynomial equations for predicting the creep life were obtained. In order to analyze the acceptance and use of the parametric methods, standard error values were accurately investigated by statistical process of the creep data. As for the results, the three parametric methods are found to be favorable in predicting the creep life of type 316LN stainless steel. Each method did not generate a large error in the standard error of the estimate with variations of the temperatures, but the Orr-Sherby-Dorn and the
Manson-Haferd methods showed a better agreement than the Larson-Miller one. Especially, at higher the 700oC, the Manson-Haferd method conformed well to the experimental data. The reason is because the Manson-Haferd method includes two constants of ta and Ta.
A Study on the Human Impulse Characteristics with Standing Shooting Posture
Authors: Lee Young Shin , Choi Young Jin , Han Kyu Hyun , Chae Je Wook , Choi Eui Jung , Kim In Woo
Published: March 2009

The rifle impact on human body is affected by the posture of human for rifling. The
interaction human-rifle system influences on a firing accuracy. In this paper, impact analysis of human model for standing posture is carried out. ADAMS code and LifeMOD are used in impact analysis of human model and modeling of the human body, respectively. At the shooting, human model is affected by rifle impact during 0.001 second. Performed simulation time for shooting is 0.3second. Applied constraint condition to human-rifle system is rotating and spherical condition.
As the results, displacement of the rifle and transfer path analysis of impact on human model is presented.
Research on Dynamic Characteristics of Assembled Thin Plates Structure by BEM
Authors: Fang Ying Wu , Huang Yu Mei , Zhang Guang Peng
Published: March 2009

A method of systematic modeling was presented to analyze dynamic characteristics of an assembled thin plates structure. Based on dynamic fundamental solutions of a thin plate, governing boundary equations in the lateral and internal vibration of the thin plate are established by using a boundary element method (BEM). According to assembled conditions on the boundary, dynamic characteristics equations of the assembled thin plates structure are deduced. In order to raise calculating efficiency and avoid complicated programming operation, an approach of frequency scanning is introduced to analyze dynamic characteristics of the assembled thin plates structure. The natural frequencies and modal shapes are obtained fast and effectively. By numerical calculation and experiments given, the established method has not only good precision but also high efficiency.
Study on the Effect of Compressive Residual Stress on Fracture Toughness of Spring Steel
Authors: Huh Sunchul , Park Won Jo , Park Sung Ho , Lee Su Hyoung
Published: March 2009

Recently, the steel parts used at the aerospace and automobile industries are required to be used lightweight parts. Therefore, used material steel have to be a high stress, which is an indispensable condition in this field. At the consideration of parts design, high hardness of the lightweight parts have an benefit of saving fuel and material. A high stress of metal has a point of difference according to the shape of design, external cyclic load and condition of vibration. Fatigue failure phenomena, which happen in metal, bring on danger in human life and property. Therefore, antifatigue failure technology take an important part of current industries. Currently, the shot peening is used for removing the defect from the surface of steel and improving the fatigue strength on surface. Therefore, this paper was investigated the effect on fracture toughness using shot peening which is improve the resistance of crack growth and crack expansion rate by fatigue that make a compressive residual stress on surface.
The Effect of Surface Treatment of Ti-6Al-4V Alloy Specimens
Authors: Son Sun Young , Nishida Shinichi , Hattori Nobusuke , Jang H.D. , Son Y.J.
Published: March 2009

As though titanium and its alloy have specific tensile strength, excellent corrosion
resistance, ect., they have not been widely used until now mainly due to their extremely high processing cost. Therefore, it is considered that the above barrier will become smaller if it is possible to improve the mechanical properties of Ti-alloys by applying surface treatments on properties, especially fatigue strength of about 6kinds of surface treatment Ti-6Al-4V alloys. This is, surface treatments by 2kinds of plasma, 3kinds of DLC (diamond-like carbon) coating and the electroness plating method, have been studied for Ti-6Al-4V alloy . This study presents an analysis of fatigue behavior from the viewpoint of micro-hardness and adhesion work through a new technique in Ti-6Al-4V alloy. In addition, the specimen's surface has been successively observed by the replica method during tests and it seems clear that the fatigue strength is improved by the DLC treatment in comparison with that of the conventional Ti-6Al-4V alloy by about 20% (fatigue limit improvement by 70MPa). Though all the hardness value of these specimens increased, the fatigue
limit improved only in the case of two kinds of specimens by DLC coating.
Effect of Interlayer Thickness on Strength and Fracture of Si3N4 and Inconel600 Joint
Authors: Yang Min , Zou Zeng Da , Song Si Li , Wang Xin Hong
Published: March 2009

In this study, Si3N4 was bonded to Inconel600 with Nb/Cu/Ni interlayer by partial liquid phase diffusion bonding method under vacuum condition. The bonding temperature, bonding time, bonding pressure and cooling velocity was 1403K, 50min, 7.5MPa and 5K/min, respectively. The effects of interlayer thickness on the strength and fracture behaviors of joint were investigated through evaluating the strength of joints based on shear test and observing the fracture morphology by means of SEM. The results showed that the shear strength of joint changed with variation of the interlayer thickness. When the shear strength of joint increased, the location of fracture was changed from the ceramic/interlay interface to the reaction layer.
Effect of Mixing Process on the Fracture Behavior of HA/PLLA Composite Material
Authors: Park Sang Dae , Todo Mitsugu , Arakawa Kazuo , Takenoshita Yasuharu
Published: March 2009

Effect of mixing process on the fracture behavior of HA/PLLA Composites were
investigated. Fracture toughness values of HA/PLLA composites prepared under different mixing time and rotor speed were measured. The fracture surface morphology was also examined by scanning electron microscopy. It was found that the fracture toughness of HA/PLLA composite decreases due to decrease of ductile deformation of PLLA matrix and debonding of interfaces with increase of the rotor speed and mixing time. Effect of mixing process on neat PLLA was also assessed, and it was found that the fracture toughness of PLLA decreases due to such pocess. Disappearance of multiple craze formation and thermal degradation were found to be the primary mechanisms of the toughness degradation.
Effect of Dynamic Strain Aging on Fatigue Softening Process of H68 Brass
Authors: Peng Kai Ping , Chen Wen Zhe , Qian Kuang Wu
Published: March 2009

Studies of the influences of symmetric tensile-compressive low cyclic fatigue behavior and dynamic strain aging (DSA) pre-treatment on H68 brass were made. The results showed that the cyclic softening was the main factor that controlled the fatigue life after various pre-treatments. The process of cyclic softening was believed to be related to the change of dislocation configuration. TEM
observation indicated that the uniform and stable dislocation networks with high density formed after DSA pre-treatment, which increased the deformation stress, decreased the cyclic strain. The cyclic softening was caused by the low dislocation density and elongated cell structure with low energy
Effect of Plastic Working on Fatigue Properties of Ti-6Al-4V Alloy with Notch
Authors: Hattori Nobusuke , Nishida Shinichi , Hara Masahiro , Son Sun Young
Published: March 2009

This study is focused to the effects of plastic working on the fatigue strength of Ti-6Al-4V alloy with notch. In general, the fatigue strength of plastic worked specimen is higher than that of non-worked one. However, the potential of hardening ability of Ti-6Al-4V alloy is very limited. Accordingly, the effect of work hardening on fatigue strength about this material is very small. In addition, the surface of the worked part becomes rougher with increasing plastic deformed value and the fatigue cracks initiate at this part. Consequently, the fatigue limit of the plastic worked specimen is
lower than that of the non-plastic-worked one.
Damage Characterization of Ceramic Matrix Composites (CMCs) during Tensile Testing
Authors: Kim Jeong Guk , Chung Jong Duk , Lee Joon Hyun , Jeong Yeon Uk , Hong Yong Ki , Kim Won Kyung , Pyun Jang Sik , Bae Dae Sung
Published: March 2009

Nondestructive evaluation (NDE) techniques were used for the tensile damage
characterization in ceramic matrix composites (CMCs). Ultrasonic testing (UT) and infrared (IR) thermography were employed to assess defects and/or damage evolution before and during mechanical testing. Prior to tensile testing, a UT C-scan and a xenon flash method were performed to obtain initial defect information in light of UT C-scans and thermal diffusivity maps, respectively. An IR camera was used for in-situ monitoring of progressive damages. The IR camera measured temperature changes during tensile testing. This paper has presented the feasibility of using NDE techniques to interpret structural performance of CMCs.
Microstructure and Toughening Mechanisms in an Al2O3 Ceramic Matrix Composite Dispersed with LiTaO3 Particles
Authors: Zhou Yu , Liu Y.G. , Jia De Chang
Published: March 2009

LiTaO3 (5--25vol%) dispersed Al2O3 matrix composite (LTA) with high relative density were fabricated by hot pressing at 1300°C. The microstructure and mechanical properties of the composite were studied. The main results are as follows: Al2O3 was found to be phase compatible with piezoelectric LiTaO3 during high temperature sintering process. The relative density of the LTA composites was greatly improved by the addition of LiTaO3 particles. Domains are clearly discerned
in LiTaO3 grains in the LTA composite, confirming that LiTaO3 particles remain ferroelectrics. 90 degree domains were observed in LiTaO3 grains constrained strongly by Al2O3 matrix, which has never been found in LiTaO3 single crystal before. Comparing with those of pure Al2O3, sintered at same temperature (1300°C), both the flexural strength and the fracture toughness of the composites are all enhanced. Domain switching is suggested as a new toughening mechanism in the ferroelectric particles dispersed structural ceramics.
Domain Switching and Crack Tip Opening Stress Variation in Ferroelectric Ceramics
Authors: Kim Sang Joo , Kim Yun Jae
Published: March 2009

Evolution of switching zone near a crack tip in ferroelectric ceramics is calculated using the constitutive equations proposed in [1], with an assumption that switching-induced internal fields are minimized by fine domain microstructures and moving charges. A two-dimensional ferroelectric ceramic specimen that has an edge crack and that is poled perpendicular to the crack plane are subjected to external stress and electric fields. Diverse crack tip microstructures are obtained depending on both the history and the ratio of electric and stress loads. It is shown that opposite crack tip opening stresses under the same electric fields are due to opposite distributions of piezoelectric coefficients in the specimens with different crack tip microstructures.