bluuebunny/crossref_metadata_2025 huggingface dataset:
Structural Topology Design Considering Reliability
Authors: Min Seung Jae , Bang Seung Hyun
Published: March 2009

In the design optimization process design variables are selected in the deterministic way though those have uncertainties in nature. To consider variances in design variables reliability-based design optimization problem is formulated by introducing the probability distribution function. The concept of reliability has been applied to the topology optimization based on a reliability index approach or a performance measure approach. Since these approaches, called double-loop singlevariable approach, requires the nested optimization problem to obtain the most probable point in the probabilistic design domain, the time for the entire process makes the practical use infeasible. In this work, new reliability-based topology optimization method is proposed by utilizing single-loop singlevariable approach, which approximates searching the most probable point analytically, to reduce the time cost and dealing with several constraints to handle practical design requirements. The density method in topology optimization including SLP (Sequential Linear Programming) algorithm is implemented with object-oriented programming. To examine uncertainties in the topology design of a structure, the modulus of elasticity of the material and applied loadings are considered as probabilistic design variables. The results of a design example show that the proposed method provides efficiency curtailing the time for the optimization process and accuracy satisfying the specified reliability.
A Unified Method for the Prediction of the Fatigue Strength of Small-Hole-Containing Components under Combined Loading
Authors: Ishimoto Isao , Endo Masahiro
Published: March 2009

A unified method is presented for the prediction of the fatigue strength of steel components containing small holes and being subjected to combined loading. Materials investigated were an annealed 0.37% carbon steel and a quenched and tempered Cr-Mo steel. Combined axial and torsional fatigue loading tests were carried out using specimens containing a small hole, which was introduced into the surface by drilling. The diameter of holes equaled the depth and was either 100µm
or 500µm. The non-propagating cracks emanating in the radial direction from the holes were observed at the fatigue limit. When the loading condition is the same, they were on a plane that inclined at the same angle with respect to the specimen axis, regardless of the size of holes. This result suggested that the fatigue strength would be controlled by the Mode I threshold condition for propagation of a crack initiated on a critical plane. A criterion connecting uniaxial fatigue strength with multiaxial fatigue strength was proposed based upon the assumption that at the threshold level, the variation of the stress intensity factor of a Mode I crack initiated under combined loading equaled that under uniaxial loading. The predictive method proposed based upon this criterion is practical in that no fatigue test is necessary in making predictions. For the various conditions of in-phase and out-of-phase fatigue loadings with an imposed mean or static load, experimental results agreed well with predictions.
On Nondestructive Evaluation of Wood Materials Using Ultrasonic Techniques
Authors: Yang In Young , Im Kwang Hee , Hsu David K. , Kim Sun Kyu , Soug Sung Jin , Cho Hyeon , Park Je Woong , Kim Young Nam
Published: March 2009

In this work, a wood material was nondestructively characterized and a technique was developed to measure ultrasonic velocity in wood using automated data acquisition software. It is desirable to perform nondestructive evaluation (NDE) to assess material properties and absorption of wood because wood is a natural composite and often inhomogeneity. Several ultrasonic techniques were applied to wood for the evaluation of variations material properties. The variation of ultrasonic
velocity was measured and found to be somewhat consistent with those in infiltrated area in the course of nature absorption. Low frequency (1MHz) through-transmission scans based on both amplitude and time-of-flight of the ultrasonic pulse were used for mapping out the material property inhomogeneity. These results were compared with those obtained by dry-coupling ultrasonics. A good correlation was found between ultrasonic velocity (a pulse overlap and peak-delay measurement
method) and C-scan image signal based on peak-to-peak amplitude.
Modeling of Characteristics of Magneto-Optical Sensor Using FEM and Dipole Model for Nondestructive Evaluation
Authors: Lee Jin Yi , Hwang Ji Seoung , Shoji Tetsuo , Lim Jae Kyoo
Published: March 2009

The magneto-optical nondestructive inspection system (hereafter refer to as RMO system) using magneto-optical sensor (hereafter refer to as MO sensor) offers the benefits of providing image data and LMF information at the same time. Therefore this system makes it possible to carry out remote and high speed inspection of cracks from the intensity of the reflected light and to estimate the
shape of a crack more effectively than by already existing methods. In other words, the shape of crack could be evaluated using image data, and crack depth can be determined by calculating the intensity of reflected light. The purposes of this study were to confirm the vertical components of leakage magnetic flux from a crack using RMO system and to verify the effects of MO sensor using the finite element method and dipole model calculation. The effectiveness of these analysis methods was compared with experiments using a RMO system and several types and sizes of the crack on plate specimens. The volume of a crack could be estimated using the optical intensity regardless of the shape of cracks.
Prediction of Ultrasonic Guided Wave Dispersion in Bent Pipes Using Finite Element Analysis and 2-D Fourier Transform
Authors: Song Sung Jin , Kim Young H. , Park Joon Soo , Yu Hyung Ju , Cheong Yong Moo , Jung Hyun Kyu , Lee Dong Hun
Published: March 2009

In this paper, the dispersion curves of a bent cylindrical pipe are obtained by using the 3-dimensional finite element modeling and 2-dimenstional Fourier transform. The transient responses of the bent pipe are calculated by using a general-purpose finite element program, and the displacements are extracted at a series of sequential points as a function of spatial position and time, u(x,t). Then 2-dimentional FFT of u (x,t) offers U (k,ω), the relation between wave number and angular frequency so that the phase velocity and group velocity can be calculated. In addition, verification of the result is made by the mode identification using wavelet transform. The modes invoked by both methods agree very well.
Effect of Water Absorption Rates on Fracture Toughness of Sisal Textile Fiber Reinforced Composites
Authors: Jeon Yang Bae , Seo Do Won , Lim Jae Kyoo
Published: March 2009

Using natural fibers that are inexpensive, lightweight and biodegradable, as the
reinforcement for composites is difficult due to their poor interfacial properties between hydrophilic fiber and hydrophobic polymer matrices. It is necessary to evaluate fracture toughness of natural fiber reinforced composites according to water absorption rates to improve mechanical performance of those. In this study, compact tension fracture test was conducted to evaluate fracture toughness with
the various specimens. The value of fracture toughness has the tendency to decrease as water absorption rate increases. And different surface treatment methods and different polymer matrices have influence on the value of fracture toughness.
Ultrasonic Linear and Nonlinear Parameters in Cyclically Deformed Cu and Cu-35Zn Alloy
Authors: Kim C.S. , Kim Yong Hwan , Kim Il Ho
Published: March 2009

The cyclic deformation in Cu and Cu-35Zn alloy were studied using ultrasonic
nondestructive evaluation (NDE) technique to measure the ultrasonic velocity, attenuation coefficient and a nonlinear parameter. These materials were cyclically deformed under total strain amplitude control to investigate their ultrasonic reaction to different dislocation substructures, depending on the stacking fault energy difference. The microstructure evolution was observed using a transmission
electron microscope, and the ultrasonic NDE parameter was measured after several cycles of fatigue deformation, in order to clarify the relationship between them. In both materials, the ultrasonic velocity was observed to decrease as the fatigue life fraction increased, which was attributed to the increasing dislocation density caused by the cyclic deformation. In the case of Cu, with its cell structure evolving during cyclic deformation, the rate of increase of the ultrasonic attenuation
coefficient and the ultrasonic nonlinear parameter was higher than that observed in the case of the Cu-35Zn alloy with its planar array structure. This result implies that the dislocation cell structure is more sensitive to the ultrasonic parameter changes than the planar array structure formed during cyclic deformation.
A Study on the Behavior of Ultrasonic Guided Wave Mode in a Pipe Using a Comb Transducer
Authors: Park Ik Keun , Kim Yong Kwon , Cho Youn Ho , Song Won Joon , Ahn Yeon Shik , Cho Yong Sang , Jung Gye Jo
Published: March 2009

A preliminary study of the behavior of ultrasonic guided wave mode in a pipe using a comb transducer for maintenance inspection of power plant facilities has been verified experimentally. Guided wave mode identification is carried out in a pipe using time-frequency analysis methods such as wavelet transform (WT) and short time Fourier transform (STFT), compared with theoretically calculated group velocity dispersion curves for longitudinal and flexural mode. The results are in good agreement with analytical predictions and show the effectiveness of using the time-frequency analysis method to identify the individual guided wave modes. And, It was found out that longitudinal mode (0, 1) is affected by mode conversion less than the other modes. Therefore, L (0, 1) is selected as a optimal mode for evaluating location of the surface defect in a pipe.
Group Velocity of Lamb Wave S0 Mode in Laminated Unidirectional CFRP Plates
Authors: Lee Jeong Ki , Kim Young H. , Kim Ho Chul
Published: March 2009

The elastic waves in the isotropic plate are dispersive waves with the characteristics of Lamb wave, however, S0 symmetric mode is less dispersive in the frequency region less than the first cut-off frequency. In the anisotropic plates such as CFRP plates, the propagation velocities vary with the directions as well as the dispersion of the Lamb wave, and the phase velocity direction does not accord with the group velocity direction. The phase velocity direction is equivalent the wave vector direction, while the group velocity direction is equivalent the energy flow direction. In this work, the group velocity dispersion curves were obtained by the dispersion relation of the Lamb wave in unidirectional CFRP plate with an orthotropic structure. The group velocities of the S0 symmetric mode in the frequency region less than the first cut-off frequency were corrected by applying the slowness surface. The propagation velocities of Lamb wave were decided by measuring the arrival time of the Lamb wave signals received with the two pinducers varying the propagating direction in the laminated unidirectional CFRP plates of 8, 16 and 24 plies having a volume fraction of 67%. The measured velocities are better agreement with corrected group velocity curve, except near the fiber direction at the cusp region. When the propagating direction is not accorded with the principal axis,
the direction of the group velocities inclines toward the fiber direction in the unidirectional CFRP plates, suggesting that the energy propagates preferentially toward fiber direction.
Joint Reaction Forces during the Recovery of Postural Balance of Human Body
Authors: Seo Min Jwa , Choi Hyeon Ki
Published: March 2009

The purpose of this study was to calculate three dimensional angular displacements,
moments and joint reaction forces (JRF) of the ankle joint during the waist pulling, and to assess the ankle JRF according to different perturbation modes and different levels of perturbation magnitude. Ankle joint model was assumed 3-D ball and socket joint which is capable of three rotational movements. We used 6 camera motion analysis system, force plate and waist pulling system. Two different waist pulling systems were adopted for forward sway with three magnitudes each. From
motion data and ground reaction forces, we could calculate 3-D angular displacements, moments and JRF during the recovery of postural balance control. From the experiment using mass-falling perturbation, joint moments were larger than those from the experiment with milder perturbation using air cylinder pulling system. However, joint reaction forces were similar nevertheless the difference in joint moment. From the results, we could conjecture that the human body employs different strategies to protect joints by decreasing joint reaction forces, like using the joint movements or compensating JRF by distributing the forces on surrounding soft tissues. The results of this study provide us important insights for understanding the relationship between balance control and ankle injury mechanism.
Finite Element Simulation of Grinding Stress for a Fiber Optic Connector (Ceramic Ferrule)
Authors: Suh Chang Min , Jung Ki Sang
Published: March 2009

Ceramic ferrule that is a major part of the optic connectors requires a high level of precision in a grinding chamfer. After the grinding chamfer, there is a problem in that the subsurface damages cannot be removed. The objective of this study was to analyze the grinding force and the associated stress generated in a ceramic ferrule during cylindrically grinding chamfer using Finite Element Analysis (FEA). A two-dimensional finite element model was constructed with the grinding parameters and the mechanical properties of the ferrule as input variables. The size of the geometric
model was the same with the ceramic ferrule. The experimental results achieved by the SEM photograph were compared with those from the FEM. The FEM results were in correlation with those of the experiments.
On the Study of Effective Breadth for Stiffened Plate under Flexible Support Condition
Authors: Kim Kyung Su , Kim Sung Chan , Kim Dae Ho , Lee Chang Hwan , Kim Jung Hee , Choi Seung Bok
Published: March 2009

The effective breadth of a stiffened plate under bending was investigated. The design parameter of an effective breadth was used when a stiffened plate subjected to a lateral loading was considered. Due to the lateral loads there was shear transmission through the plate from the stiffener, which leads to a non-uniform longitudinal stress distribution across the plate width the effective breadth that takes into account a shear lag can be calculated by the simple beam theory. For a tanker,
the existing effective breadth concept has been used when longitudinal stiffeners are fixed at adjacent web frames. However, the effective breadth of each classification’s formula can’t be applied to flexible support condition such as the one prevailing in Ro-Ro vessel. The effective breadth according to the rules of several classification societies was compared and a way to get an accurate
analysis as suggested.
Influence of Nitriding Treatment on Practical Properties of Eutectoid Steel
Authors: Sun Wen Xian , Nishida Shinichi , Hattori Nobusuke , Zhou Cong Ling
Published: March 2009

The present study focused to the effect of ion nitriding on fatigue properties of eutectoid steel. Two different temperatures (550°C and 500°C) and two different types of specimens (smooth and notched ones) were used in this study to investigate the mechanism of modification. Residual stress and EPMA analysis were used to derive the quantity relationship among case depth, residual stress and fatigue strength. The results confirmed the efficiency of ion nitriding in improving the
fatigue properties of eutectoid steel. Surface hardening, refined microstructure and compressive stress were the three main factors being responsible for the modification of fatigue properties.
Assessment of Geometry Independent Fracture Resistance Characteristics Based on Local Approach
Authors: Chang Yoon Suk , Lee T.R. , Choi Jae Boong , Kim Young Jin
Published: March 2009

The influences of stress triaxiality on ductile fracture have been emphasized to explain the geometry independent fracture resistance characteristics of specimens and structures during past two decades. For the estimation of this material behavior, two-parameter global approach and local approach can be used as case by case manner. Recently, the interests for the local approach and micro-mechanical damage model are increased again due to progress of computational environments.
In this paper, the applicability of the local approach has been assessed through a series of finite element analyses incorporating both modified GTN model and Rousselier model. The ductile crack growth behaviors are examined to guarantee the transferability on different sizes and geometries of C(T) specimens and SE(T) specimens. The material fitting constants are determined from calibration
of tensile tests and numerical analyses results, and used to simulate the fracture behaviors of typical specimens. Then, a comparison is drawn between the numerically estimated crack resistance curves and experimentally determined ones. The comparison results show a good agreement and the two damage models are regarded as promising solutions for ductile crack growth simulation.
The Effect of Sample Preparation upon the Fracture Toughness of Microsized TiAl
Authors: Halford T.P. , Rudinal D. , Takashima Kazuki , Higo Yakichi
Published: March 2009

The effective fracture toughness testing of materials intended for application in MicroElectroMechanical Systems (MEMS) devices is required in order to improve understanding of how they may be expected to perform upon the micro scale. γ-TiAl based materials are being considered for application in MEMS devices required to operate at elevated temperatures. The effect of different preparation methods upon resulting fracture toughness and development of testing methods for these devices is therefore of importance. Micro-sized cantilevers of the γ-TiAl alloy
“Alloy 7” (Ti-46Al-5Nb-1W) were therefore prepared using either mechanical or chemical final stage polishing and subsequently used to evaluate fracture toughness. The effectiveness of the evaluation of micro-sized samples of γ-TiAl in this manner is considered, as well as the effects of the different processing methods and variations in properties according to lamellar orientation.
Effect of Strain Rate Variation on Fatigue Life of Spot Welded Joint
Authors: Song Joon Hyuk , Yu Hyu Sun , Kang Hee Yong , Yang Sung Mo
Published: March 2009

Resistance spot welding is used extensively to fasten sheet for automotive applications. In many components, these welds should maintain their integrity under severe loading conditions. However fatigue strength of the spot welded joint is considerably lower than base metal due to stress concentration at the nugget edge, and is influenced by its geometrical and mechanical factors such as welding condition and etc. In this paper, it is estimated that effect of strain rate variation on fatigue life of spot welded joint. The analytical method proposed to overcome above difficult using lethargy coefficient concept for evaluating the fatigue life cycle of spot welded joint. The reliability of the life cycle is completed by comparing with the life cycle obtained by fatigue test for the specimen with the welding current. And the above procedure is numerically extended to get the life of dynamic strain rate region.
A Study on Fracture Toughness of 9Al2O32B·2O3/AC4CH Alloy Composites
Authors: Park Won Jo , Kim Chu Yong , Huh Sunchul , Lee Kwang Young
Published: March 2009

An aluminum borate whisker (Al18B4O33w) was recognized as an attractive reinforcement for the aluminum alloy, It is good strength, high wear resistance, good thermal stability and low cost, comparable with those of other whiskers such as SiC and Al2O3. In general, aluminum borate whisker reinforced AC4CH alloy composites have been produced by squeeze casting process, which is capable of promoting the higher specific mechanical properties. α+Al18B4O33w/AC4CH (α: SiO2, Al2O3, TiO2sol) composites were fabricated by squeezecasting method in which the molten aluminum infiltrated into the whisker preform. The primary objective of this study was to establish the influence of the fracture toughness of α+Al18B4O33w reinforced composite by different containing inorganic binder. In addition, the fracture mechanism was evaluated through the scanning electron micrographs.
As results, fracture toughness the composite containing TiO2 sol was shows plane about 9.28Mpa-m0.5. TiO2 inorganic binder can enhance fracture toughness of the Al18B4O33w reinforced composite. In order to obtain Al18B4O33w reinforced aluminum composites to have good fracture toughness use of TiO2 inorganic binder is recommend.
Experimental Study on Fatigue Crack Growth in a Titanium Alloy
Authors: Li Qing Fen , Wang Peng , Liu Dong , Wang Jun , Liu Hong Juan , Wang Yan Bo
Published: March 2009

A series of test for the fatigue crack growth rate da/dN and the threshold ΔKth values were performed with CT specimens on a ship-condenser material titanium alloy plate and rolled ring. Base metal, welded joint and HAZ (heat affected zone) materials were used to make different test specimens. Specimens made from the titanium plate were cut along L-T direction, those made from rolled ring were obtained along C-R and L-R direction respectively. Results show that the fatigue crack growth rate value of welded joint is much higher than those of base metal and HAZ material. The da/dN values of C-R direction specimens are much higher than those of L-R direction specimens, whereas the ΔKth values are lower. It means that welding process may lead to a great reduction in the fatigue property for titanium alloy and the effect of crack orientation on fatigue property is not negligible for titanium alloy. To select a proper orientation of titanium material is therefore very important in engineering practice. Results also indicate that a simplified method can be used to calculate the ΔKth values for titanium material, that is, ΔKth values may be calculated directly from the da/dN expression in a zone near the threshold and the laborious measurements of ΔKth may therefore be saved.
Fatigue Properties of Non-Loosening Bolt with Double Screw Mechanism
Authors: Nishida Shinichi , Hattori Nobusuke , Iwakiri H. , Uchisako A.
Published: March 2009

Prevention of slack in fastening bolt has been an important researching subject since fatigue failure can be generally caused by loosening nut. According to the above reason, the super lock bolt with double screw mechanism, which is non-loosening, has been developed for preventing such kind of bolt failure. The objects of the present study are as follows: (1) To clarify the fatigue strength characteristics. (2) To investigate the initiation and propagation behaviour of fatigue crack regarding to the thread root of first pitch. In addition, the mechanism of “fatigue strength of super lock bolt” is also discussed in this paper and it is confirmed that this bolt shows excellent fatigue strength and non-loosening properties.
Numerical Approach to Investigating Pre-Existed Cracks in Rocks
Authors: Wang Shu Hong , Sun Huo Ran , Xu Tao , Yang Tian Hong , Wang En'de
Published: March 2009

Rock failure analysis is an important research in investigating the behavior of rocks,
especially its failure process. And a rock sample, which contains pre-existing cracks, is a typical sample to investigate the rock failure behavior which under tension or compression, because almost all the natural materials exist micro-flaws more or less. This mode is closed to the natural material character. By using Rock Failure Process Analysis code, RFPA2D, we present a numerical simulation and similar materials experiment on rock samples with two pre-existing cracks in uniaxial
compression were conducted to investigate the initiation, propagation, coalescence of cracks and failure mechanism of rock. Numerical simulations visually reproduce the process of crack initiation, propagation and coalescence in rock, which are well tallied with experiments in laboratory.
Numerical Study on Shear Strength and Failure Pattern of Jointed Rock under Shear Testing
Authors: Zhang Hou Quan , Song Li , Liu Junjie , Xu Tao , Chen Xiong , Liang Zheng Zhao
Published: March 2009

The purpose of this paper is to investigate shear strength and failure pattern of rock
containing two parallel open joints with different horizontal separations using RFPA2D (rock failure process analysis) code. Specimens are placed in a direct shear box. The upper is invariably loaded with normal stress 0.15MPa, the left is controlled by a constant increasing horizontal displacement 0.002mm/step. The whole shear failure process is visually represented and the failure pattern in reasonable accordance with previous experimental results is obtained. In general, only mixed mode (tensile and shear) is observed for the failure pattern in the numerical tests. Tensile cracks initiate from the tips of pre-existing joints respectively with an initiation angle of about 45°, then propagate towards another joint in a single stria; Shear cracks occur in the further process and the main direction of shear failure surface is roughly parallel to shear loading. The failure pattern of bridged rock is mainly controlled by the joint separation and the roughness of wavy shear failure surface is different, which is mostly influenced by the joint separation in the same way. The peak shear load, related to the failure patterns, decreases with the increase of joint separation, but the shear strength of intact rock is invariable.
Web-Based Expert System in Fatigue and Fracture Analysis
Authors: Ren Zheng Yi , Li Qing Fen , Zhu Hai Tao , Shu Hai-sheng , Long Ping
Published: March 2009

An expert system in fatigue and fracture analysis based on Web is developed in this paper. The system consists of six functional parts: a general inference engine, some knowledge bases, a context, an interpretation engine, a bases administration system and the interface (includes browser, Web-server, etc.). It can simulate a human expert to make analysis and design scheme for some typical structural components: pressure vessels, huge rotation constructions, welded structures, etc. It is an open system which may be broadened and perfected to cover a wider range of application through the modification and enlargement of the knowledge and data bases on Web.
Effect of Hydrogen Absorption on the Mechanical Properties of Palladium
Authors: Yamaya Midori , Futakawa Masatoshi , Date Hidefumi
Published: March 2009

The mechanical properties of palladium (Pd) wire absorbed hydrogen were evaluated by the quasi-static tension test and indentation test. The electrolytic method was used for hydrogen absorption. Pd wire with a diameter of 1mm was used. The electrolyte was a sulfuric acid solution and the current density used in the electrolytic method was 200mAcm-2. The hydrogen absorption ratio defined by the molecular ratio (H/Pd) of hydrogen and palladium was controlled by the absorption time. The gauge length for the tension test was 20mm. The ultimate tensile strength increased with the increase of the absorption ratio. On the other hand, the increase of the ratio decreased the strain hardening parameter and fracture strain. A model considering the specimen absorbed hydrogen and a composite material constructed in a concentric configuration was suggested to estimate the hydrogen absorption area and mechanical properties. The indentation test was conducted to clarify the evolution of the embrittlement due to the hydrogen absorption microscopically and determine the absorption area precisely. Vickers hardness clearly increased with the increase of the hydrogen absorption ratio. The hardness distribution was measured to detect the boundary of the absorption and non-absorption area using a Berkovich indenter that is smaller than a Vickers indenter. The hardness boundary of the absorption and non-absorption of the specimen with the hydrogen absorption ratio of 22 percent was observed experimentally at the position around 100-150μm from the outside of the specimen. The position of the boundary estimated using the model was 85μm from the outside of the specimen. When the stress-strain curves of the specimen with the unknown hydrogen absorption ratio were measured, the hydrogen absorption ratio could be estimated using the proposed model.
Effects of Water Absorption Cycles on Fracture Toughness in Laminated CFRP Composites
Authors: Choi Jun Yong , Seo Do Won , Lim Jae Kyoo
Published: March 2009

Composite materials have drawn a lot of attention in recent years due to their being in expensive, lightweight and biodegradable. The polyetherimide has been successfully used as an effective toughening modifier for polyfuctional epoxy resins for aerospace use. The material used in this study was solvent-impregnated carbon-fiber fabric reinforced polyetherimide. In this study, effects of water absorption cycles on fracture toughness in carbon fiber reinforced composites (CFRP)
have been investigated according to various absorption cycles. As a result, strength of CFRP composite was decreased according to increasing water absorption cycles.
Robust Design of Lamination on Flexural Properties of CFRP
Authors: Kanemitsu Manabu , Nakayasu Hidetoshi
Published: March 2009

A new method is proposed in this paper for robust deign of configuration of multiple layers. The present design tool may enable the designers to estimate the flexural strength for the target combination of lamina. In line with these objectives, an experimental analysis was performed for 3 kinds of combinations of the number of orientation angles and 21 kinds of configurations of the symmetric 26 layers. The experimental results are compared with the theoretical considerations. From the viewpoint of robust design of configurations, the relation between flexural fracture strength and equivalent engineering modulus was also investigated. Finally, the procedure of practical robust design of composite laminate is also proposed.
The Effect of a Honeycomb Core on the Mechanical Properties of Composite Sandwich Plates
Authors: Kong Cheol Won , Eun Se Won , Park Jae Sung , Lee Ho Sung , Jang Young Soon , Yi Yeong Moo , Cho Gwang Rae
Published: March 2009

When comparing composite sandwich analysis with an exact solution, the results of finite element modeling with an ANSYS shell 91 element agreed well with the exact solution. The practical applications of the shell 91 element are demonstrated with a four-point bend test conducted on sandwich beam specimens. The specimens comprised carbon/epoxy fabric face sheets and a honeycomb core. Two kinds of honeycomb cores were used to fabricate the composite sandwich specimens: an aluminum one and a glass/phenolic one. The predictions with the shell 91 element were also agreed well with the experimental results. A variety of tests was conducted; namely, a long beam flexural test, a short beam shear test, a flatwise tensile test, a flatwise compression test and an edge compression test. The sandwich plate with the aluminum honeycomb core had a specific bending stiffness that was 1.7 to 2.0 times higher than that of the sandwich plate with the glass/ phenolic honeycomb core.
Mechanical Properties and Microstructure of SUS304 Brazed Joint with Ni-Based Filler Metals Added Cr Powder
Authors: Shohji Ikuo , Takayama Satoshi , Nakazawa Takanori , Matsumoto Ken , Hikita Masanori
Published: March 2009

In the brazed joint of stainless steel with BNi-2 filler, brittle Cr-B compounds form in the vicinity of the centerline of the brazed joint. These compounds cause a decrease in joint strength. In this study, BNi-2 filler supplemented with Cr powder has been used in brazing stainless steel in orde r to disperse brittle Cr-B compounds uniformly in the brazed joint and improve joint strength. The mechanical properties and microstructures of the brazed joints were investigated. Moreover, a comp arison of the brazed joint with that using the BNi-2 filler was conducted.
Diffusion Bonding of Al 6061 Alloys Using an Eutectic Reaction of Al-Ag-Cu
Authors: Lee Young Sup , Lim Cheol Ho , Lee C.H. , Seo K.W. , Shin Seung Y. , Lee Chang Hee
Published: March 2009

In this study, a diffusion bonding of aluminium alloy A6061 was preformed using an
Ag-28Cu filler metal in order to conduct eutectic brazing. Melting mechanism was surveyed. Interface behaviors of the brazed joints were observed after brazing and T6 solution treatment. Also, tensile property of the brazed joints was examined. During diffusion bonding of Al6061 alloys with Ag-28Cu filler metal, eutectic melts were formed by eutectic reaction between Al6061 and Ag-28Cu filler metal. It was found that the reaction layer consist of two phases formed at the interface between
AA6061 and Ag-28Cu filler metal. EPMA analysis revealed that two phases in the reaction layers consist of Ag-rich phase and Cu-rich phase. Tensile strength was 300 MPa after ageing treatment at 175°C.
Influence of Surface Finish of Cu Electrode on Shear Strength and Microstructure of Solder Joint with Sn-3Ag-0.5Cu
Authors: Shohji Ikuo , Goto Hiroki , Nakamura Kiyotomo , Ookubo Toshikazu
Published: March 2009

An influence of a surface finish of a Cu electrode on joint properties of a lead-free solder joint with Sn-3mass%Ag-0.5mass%Cu has been investigated. As the surface treatment method, Ni/Au electroplating, Au electroplating and organic solderability preservative (OSP) treatments were conducted to Cu electrodes. A heat exposure treatment was conducted at 150°C up to 500h in order to investigate the reliability of the solder joint under heat exposure conditions. Ball shear test was performed to examine joint strength. Microstructural observation was conducted to investigate growth kinetics of a reaction layer formed at a joint interface and microstructural revolution in the solder layer.
Effect of Fiber Orientation on the Tensile Strength in Fiber-Reinforced Polymeric Composite Materials
Authors: Kim Jin Woo , Lee Jung Ju , Lee Dong Gi
Published: March 2009

The study for strength calculation of one way fiber-reinforced composites and the study measuring precisely fiber orientation distribution were presented. However, because the DB that can predict mechanical properties of composite material and fiber orientation distribution by the fiber content ratio was not constructed, we need the systematic study for that. Therefore, in this study, we investigated what effect the fiber content ratio and fiber orientation distribution have on the strength of composite sheet after making fiber reinforced polymeric composite sheet by changing fiber orientation distribution with the fiber content ratio. The result of this study will become a guide to design data of the most suitable parts design or fiber reinforced polymeric composite sheet that uses the fiber reinforced polymeric composite sheet in industry spot, because it was conducted in terms of developing products. We studied the effect the fiber orientation distribution has on tensile strength of fiber reinforced polymeric composite material and achieved this results below. We can say that the increasing range of the value of fiber reinforced polymeric composite’s tensile strength in the direction of fiber orientation is getting wider as the fiber content ratio increases. It shows that the value of fiber reinforced polymeric composite’s tensile strength in the direction of fiber orientation 90° is similar with the value of polypropylene’s intensity when fiber orientation function is J= 0.7, regardless of the fiber content ratio. Tensile strength of fiber reinforced polymeric composite is affected by the fiber orientation distribution more than by the fiber content ratio.
Mesoscopic Modeling of Deformation Behavior of Semi-Crystalline Polymer
Authors: Uchida M. , Tomita Yoshihiro
Published: March 2009

In present study, we clarify the micro- to mesoscopic deformation behavior of semicrystalline polymer unit cell by using large deformation finite element homogenization method. Crystalline plasticity theory with penalty method for enforcing the inextensibility of chain direction and nonaffine molecular chain network theory were applied to the representation of the deformation behavior of crystalline and amorphous phases, respectively, in composite microstructure of semicrystalline
polymer. The different directional tension and compression are applied to the 2-
dimensional plane strain semi-crystalline unit cell model. A series of computational simulation clarified highly anisotropic deformation behavior of microstructure of semi-crystalline polymer, which is caused by rotation of chain direction and lamella interface, and manifests as a substantial hardening/softening. This anisotropy for tensile deformation is higher than that for compressive deformation.
Development of a Torsion-Free Brake Shoe Holder Hanger for the Bogie of Railway Freight Car
Authors: Ham Young Sam , Hong Jai Sung , Oh Taek Yul , Paik Young Nam
Published: March 2009

Among welded structure bogies used for high speed freight cars, failures in an end beam have been found in a number of bogies manufactured in between 1999 and 2000. A freight car suffers from a harsher loading condition and it uses a tread brake without a secondary suspension system. It is presumed that the cause of the failure on the end beam is not the vertical loading by the cargo and the vehicle but the force exerted by the brake. The failure at the end beam makes the brake system useless and can cause a derailment in the worst case. In this study, we propose a simple torsion-free brake shoe holder hanger to remove torsion of hanger bracket. Also performed are the finite element analysis and the on-board test for the developed part. Comparison tests verified the applicability of the torsion-free brake shoe holder hanger.
The Development of Dunnage for Transportation of a Steel Roll Coil
Authors: Kim Hang Woo , Han Jae Ho , Kwac Lee Ku
Published: March 2009

Ironwork, especially steel roll coil, is usually transported to the customers over land or by sea. For fast and safe transportation of steel roll coil without damaging it, it is necessary that steel roll coil is surely fixed. These days, apitong, which is fully imported from abroad, is being used to fix the steel roll coil. However, because of apitong harshness, it often damages the coil that would be hard to fix. Recovering damaged coil is almost impossible, and we have to look for a new type of dunnage,
which would be able to substitute apitong. This paper discusses various types of reinforcement, as well as rectangular and trapezoid dunnages. We will consider how rolling occurs and what happens when the carrier starts and stops moving. Thus, it will be possible to design a dunnage, which would not damage ironwork and had better recovery and softness than the existing apitong.
Creep, Tensile and Oxidation Properties of Ti-4wt%Fe-(0~2)wt%Si Alloys
Authors: Lim Byeong Soo , Kim Bum Joon , Bae Si Yon , Kim J.W. , Lee Dong Bok
Published: March 2009

New Ti-base alloys were designed to replace conventional expensive elements with low cost elements of iron and silicon. The prepared Ti-4wt%Fe-(0~4)wt%Si alloys were creep tested at 600oC in air, tensile tested at room temperature and 400oC in air, and exposed to hot air for oxidation tests between 700 and 1000oC. When compared to the Ti-6Al-4V alloy, Ti-4wt%Fe-(0.5~2)wt%Si alloys displayed poorer creep resistance, but exhibited good tensile properties and superior oxidation
resistance.
Estimation of Creep Crack Growth Properties Using Circumferential Notched Round Bar Specimen for 12CrWCoB Rotor Steel
Authors: Ha Je Chang , Lee Joon Hyun , Tabuchi Masaaki , Yokobori Jr. A.Toshimitsu
Published: March 2009

Most heat resisting materials in structural components are used under multi-axial stress conditions and under such conditions ductile materials often exhibit brittle manner and low creep ductility at elevated temperature. Creep crack initiation and growth properties are also affected by multi-axial stress and it is important to evaluate these effects when laboratory data are applied to structural components. Creep crack growth tests using circumferential notched round bar specimens are a simple method to investigate multi-axial stress effects without using complicated test facilities. Creep crack growth tests have been performed using a 12CrWCoB turbine rotor steel. In order to investigate the effects of multi-axial stress on creep crack growth properties, the tests were conducted for various notch depths at 650°C. The circumferential notched round bar specimen showed brittle crack growth behaviour under multi-axial stress conditions. Creep crack growth rate was characterized in terms of the C* parameter. A 12CrWCoB turbine rotor steel has been tested using circumferential notched round bar specimens with different multi-axiality. Circumferential notched round bar specimens show increased brittle creep crack growth behaviour due to the multi-axial stress condition. Creep crack growth
properties could be predicted by allowing for the decrease of creep ductility under multi-axial conditions.
The Strength and Hardness of Metal Matrix Composites by Binder Additives
Authors: Park Won Jo , Jung Hae Young , Huh Sunchul , Yoon Han Ki , Lee Kang Kil
Published: March 2009

20 vol.% aluminum borate whisker (Al18B4O33w) reinforced AC4CH alloy composite was fabricated by squeeze casting method. The matrix is controlled its impurities, which make metal alloys, especially AC4CH alloy that is made by restraining 0.2% Iron and aluminum to make a matrix material. The perform of composite materials was made from Al18B4O33w with 5% regulated three kinds of inorganic binders, SiO2, Al2O3 and TiO2 sol, respectively and then sintered at 1373K. The composites were obtained by squeeze cast infiltration of the molten alloy to the perform. Then it was squeeze casting into the matrix. The status of adhesions of whisker perform was Observed by SEM. Micro-Vickers hardness and tensile properties at the room temperature were estimated. Al18B4O33w/ AC4CH composites containing TiO2 sol has excellent properties on tensile properties and microvickers hardness compared with the other composites without inorganic binder, containing SiO2 and Al2O3 sol inorganic binder.
Influence of Containerless Solidification on Hardness in Multifunctional Titanium Based Alloys
Authors: Aoyama Tomotsugu , Kawamura Haruki , Kotake Shigeo , Suzuki Yasuyuki
Published: March 2009

A novel synthesis procedure of multifunctional Ti based alloy was suggested under
containerless processing using an electromagnetic levitation furnace. In this method, necessary condition to synthesize the alloys with ability of a dislocation-free plastic deformation was determined. That was supported by microstructural observation, hardness measurement and X-ray analysis of the alloys solidified from several undercoolings. The maximum undercooling of the alloy melt was up to 120K. Synthesized alloys that met the condition showed refined microstructures, increase of d-value of (110) plane and a tiny deviation of hardness by cold-working Others partially occurred stress-induced transformation.
Measuring Residual Stress with the Indentation Method in Struc­tural Ceramics
Authors: Tokuda Tarou , Wang Rong Gang , Kido Mitsuo , Katayama Gonojo
Published: March 2009

This study deals with the indentation method of measuring residual stress in structural ceramics. First we investigate the appropriate pretreatment for measuring fracture toughness (basis value, KC) while avoiding any influence from residual stress, which is important when estimating residual stress using the indentation method. Based on the fracture toughness value, the residual stresses in Al2O3, Si3N4 and ZrO2 ceramics are estimated using the indentation method. Phase transformation is a problem when estimating residual stress using the indentation method with ZrO2 ceramics. Residual stresses in Al2O3 and Si3N4 can be largely eliminated by annealing the specimen after hand grinding. Consequently, it is thought that this treatment method is effective for determining the basis value KC. The estimated residual stress values in Al2O3 and Si3N4 obtained by the indentation method at 98 N corresponded closely to the values obtained wih X-rays. The residual stress value obtained by the indentation method for ZrO2 was close to the value obtained through the X-ray method, when the indentation load was 294 N. When estimating the residual stress in ZrO2 using the indentation method, the influence of the phase transformation caused by the indentation is added onto the original residual stress, when the indentation is small. The influence becomes smaller
when the indentation load is large. If the applied indentation load is between 294 N and 490 N, the indentation method is effective for estimating the residual stresses in Al2O3, Si3N4 and ZrO2 ceramics.
A New Specimen for Measuring the Interfacial Toughness of Al-0.5%Cu Thin Film on Si Substrate
Authors: Jeon Insu , Omiya Masaki , Inoue Hirotsugu , Kishimoto Kikuo , Asahina Tadashi
Published: March 2009

A new specimen is proposed to measure the interfacial toughness between the Al-0.5%Cu thin film and the Si substrate. The plain and general micro-fabrication processes are sufficient to fabricate the specimen. With the help of the finite element method and the concepts of the linear elastic fracture mechanics, the detailed structure for this specimen is modeled and evaluated. The results obtained from this research show that the proposed specimen provides efficient and convenient method to measure the interfacial toughness between the Al-Cu thin film and the Si
substrate.
Measurement of Continuous Micro-Tensile Strain Using Micro-ESPI Technique
Authors: Huh Yong Hak , Kim Dong Iel , Kee Chang Doo
Published: March 2009

To determine the micro-mechanical properties for micro/nano materials, it may be essential to measure the strain/deformation during micro-mechanical testing. Therefore, in this study, continuous measurement of in-plane tensile strain in micro-sized specimens of thin film materials was introduced using the micro-ESPI technique. TiN and Au thin films 1 and 0.47µm thick, respectively, were deposited on the silicon wafer and fabricated into the micro-sized tensile specimens by the electromachining process. The micro-tensile loading system and micro-ESPI system
were developed to measure the tensile strain during micro-tensile loading. Micro-tensile stress-strain curves for these materials were determined using the algorithm for continuous strain measurement. Furthermore, the new algorithm for enhancing the sensitivity to measurement of in-plane tensile strain was suggested. Using the algorithm, micro-tensile strain data between interfringes were calculated. It is shown that the algorithm for enhancement of the sensitivity suggested in this study makes the sensitivity to the in-plane tensile strain increase.
The Study on Fatigue Life of Interconnect with Respect to Geometrical Shape of Supporting Structure and Load Conditions in MEMS
Authors: Shim Jae Joon , Han Geun Jo , Kim Kwang Young , Yun Doo Pyo , Ok Chul Ho , Lee Sang Suk
Published: March 2009

Recently, application of semiconductor sensors has widely spreaded into various industries becasuse those have several merits like easy miniaturization and batch production etc. But external conditions such as thermal and repetitive load have a bad effect on sensors’s lifetime. Therefore, lots of studies related with the fatigue of microelectromechnical systems (MEMS) have been conducted. Especially, this paper was focused on fatigue life of aluminum interconnect in the supporting
structure of sensor under cyclic thermal load and on the approximation equation defining the critical temperature to ensure required operating life using FEM simulation.