bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrogen Effect on Fatigue Strength of Structural Steels
Authors: Ebara Ryuichiro
Published: March 2009

In this paper hydrogen effect on fatigue strength of structural steels is mainly reviewed on the basis of the author's experimental results. The emphasis is focused upon the hydrogen related corrosion fatigue crack propagation behavior of the ship structural steels and their welded joints in sour crude oil environment. It can be concluded that the environment enhancement of the fatigue crack propagation rate in sour crude oil is dependent of hydrogen evolved by reaction of H2S and H2O in the sour crude oil with structural steels.
Frictional Sliding of Microcracks under Compression
Authors: Feng Xi Qiao , Wang Xi Shu
Published: March 2009

It is of interest to understand damage and failure mechanisms of microcracks and their evolution as a function of loading history, especially in the case of complex loading. Owing to their superior mechanical and physical properties, carbon nanotubes (CNTs) seem to hold a great promise as an ideal reinforcing material for composites of high-strength and low-density. HOWEVER, In most of the experimental results, only modest improvements in the strength and stiffness have been achieved by incorporating carbon nanotubes in polymers. There are many factors that influence the overall mechanical property of CNT-reinforced composites, e.g. the weak bonding between CNTs and matrix, the waviness and agglomeration of CNTs. In the present paper, we use the Mori-Tanaka method to evaluate the effect of these factors on the moduli of CNTs-CNT-reinforced composites. It is established that the waviness and agglomeration may significantly reduce the stiffening effect of CNTs, while the interface between the matrix and CNTs influence the moduli of CNTs-reinforced composites little.In this paper, the frictional sliding of microcracks under complex triaxial loading is analyzed, and the obtained results are incorporated into the constitutive relation of microcrack-weakened brittle materials.
Fatigue Design of Leaf Spring Based on Proving Ground
Authors: Sohn Il Seon , Bae Dong Ho , Jung Won Seok , Park S.J.
Published: March 2009

The suspension system of vehicle is directly influenced to ride and handling. Therefore, suspension part should have enough endurance during its lifetime to protect passenger. Spring is one of major suspension part of vehicle. Thus, in this paper, a fatigue design method for leaf spring based on proving ground response was proposed. At first, stress and displacement of leaf spring are measured through the proving ground test. And next, the maximum load acting on leaf spring assembly under driving condition was defined from the road load response. On the base of these results, fatigue tests for leaf spring assembly and 3-point bending fatigue tests for material of leaf spring were carried out. From the above, the maximum load-fatigue life relation of leaf spring material and assembly was defined, and 3-point bending test result has good agreement with leaf spring assembly fatigue test result. Thus, it is expect that economical fatigue design criterion for leaf spring assembly can be determined from fatigue data of simple smooth specimen by 3 point bending fatigue tests.
A Prediction Method of Corrosion Degradation and Corrosion Fatigue Strength of TMCP Steel
Authors: Bae Dong Ho , Park J.H.
Published: March 2009

In order to develop a corrosion fatigue design method and estimate reliability of TMCP steel using as the material of heavy industries and plants, its electrochemical corrosion characteristics and determination of corrosion fatigue design criterion were investigated. And, a corrosion fatigue design method of TMCP steel was also investigated. From the results, the corrosion characteristic of TMCP steel is very susceptible in 3.5wt.% NaCl solution. Its susceptibility was linearly increased with the solution temperature increase. Corrosion fatigue strength in 25°C, 3.5wt.% NaCl solution is very lower than that of in air. And also, it was decreased with loading frequency decrease in the same environment. It was found that corrosion fatigue strength and life of TMCP steel is predictable by using the S-N curve of fatigue strength in air. Therefore, it is expected that the developed corrosion fatigue design method for TMCP steel will be useful for safe design and reliability assessment of the industrial facilities and structures.
A Structure Nondestructive Evaluation Using Laser-Generated Ultrasonic Application
Authors: Kim Jae Yeol , Yoon S.U. , Jang Kyeung Cheun , Ko Myung Soo , An Jae Sin
Published: March 2009

In the present study, a Nd;YAG Laser (pulse type) was used to emit ultrasonic signals to a test material. In addition, a total ultrasonic investigation system was designed by adopting a Fabry-Perot interferometer, which receives ultrasonic signals without any contact. For non-destructive test SM45C, which contains some flaws was used as a test material. Because it is easy to align light beam in receiver, and the length of the light beam does not change much even if convex mirror leans towards one side, confocal Fabry-Perot interferometer, which has stable frequency, and PI control are used to correct interfered and unstable signals from temperature, fluctuation and time shift of laser frequency. Stable signals are always obtained by the feedback of PI circuit signals in the confocal Fabry-Perot interferometer. The type, size and position of flaws inside the test material were examined by achieving the stabilization of an interferometer. This study presented a useful method, which could quantitatively investigate the fault of objects by using a Fabry-Perot interferometer.
Nondestructive Evaluation and Fracture Mechanism of Smart Material
Authors: Lee Jin Kyung , Park Young Chul , Lee Joon Hyun , Lee Sang Ll , Hur Kwan Do
Published: March 2009

Tensile residual stress occurring due to the difference of coefficients of thermal expansion between fiber and matrix is one of the serious problems in metal matrix composites (MMC). In this study, TiNi alloy fiber was used to solve the problem of the tensile residual stress of TiNi/Al6061 shape memory alloy(SMA) composite as the reinforced material. TiNi alloy fiber improves the tensile strength of a composite by inducing compressive residual stress in the matrix using its shape memory effect. The fixture was made to hold TiNi shape memory fiber uniformly. Some tensile test
specimens with several volume fractions are made by the hot pressing method under the optimum processing condition. In order to generate the compressive residual stress in TiNi/Al6061 SMA composite, 1%, 3% and 5% pre-strain was added in advance. It was evaluated the effect of compressive residual stress corresponding to pre-strains variation using the acoustic emission(AE)
technique. AE technique was also used to clarify the damage behavior and the microscopic failure mechanism of TiNi/Al6061 SMA composite. In addition, a two-dimensional AE source location technique was applied to measure the position of the crack initiation and propagation in composites.
UT System Composition and Welding Flaw Classification for SWP Stability Estimation
Authors: Kim Jae Yeol , Yoo Young Tae , Song Kyung Seok , Kim Chang Hyun , Yang Dong Jo
Published: March 2009

The purpose of this research is stability estimation of plant structure through classification and
recognition about welding flaw in SWP(Spiral Welding Pipe). And, In this research, we used
nondestructive test based on ultrasonic test as inspection method, and made up inspection robot in
order to control of ultrasonic probe on the SWP surface, and programmed to signal processing code
and pattern classifying code by user made programming code. Inspection robot is simply
constructed as 2-axes because of welding bead with fixed pitch. So, inspection of welding part can
be possible as composition of inspection part for tracking on welding line. For evaluation of flaw
signal is reflected on welding flaw, user-made program codes are composed of signal processing
and Bayesian classifier and perceptron neural network and back-propagation neural network. And
then, we confirmed to superiority of neural network method compared with Bayesian classifier for
classification and recognition rate. According to this result, we selected back-propagation neural
network as classification and recognition method about the system of SWP stability Estimation[2].
Through this process, we proved efficiency on the system of SWP stability Estimation, and
constructed on the base of the system of SWP stability Estimation for the application in industrial
fields.
Temperature Joint Study of Reinforced Concrete Frame and Bent
Authors: Song Li , Liao Hong Jian , Wu Sheng Xing
Published: March 2009

This paper devoted to studying temperature joint in structures of reinforced concrete frame
and bent. A nonlinear analysis program is made and improved specially for the study of reinforced
concrete frame and bent under temperature load. Some reasonable values of joint distance are
obtained for the frame and bent under high, middle and low temperature, and a design method of
super-length reinforced concrete frame and bent under temperature load is presented.
Fracture Characterization of MoSi2 Based Composites
Authors: Lee Sang Ll , Jin J.O. , Park J.S. , Lee Jong K. , Min Byeong Hyeon , Yoon Han Ki , Park J.Y.
Published: March 2009

This study dealt with the characterization of MoSi2 based composites containing three types of additive materials such as SiC, NbSi2 and ZrO2 particles have been investigated, based on the detailed examination of their microstructures and fracture surfaces. The effects of reinforcing
materials on the high temperature strength of MoSi2 based composites have been also examined. MoSi2 based composites were fabricated by the hot press process under the vacuum atmosphere. The volume fraction of reinforcing materials in the composite system was fixed as 20 %. The
microstructures and the mechanical properties of MoSi2 based composites were investigated by means of SEM, EDS, XRD and three point bending test.
A Study on the Dimensional Stability of Interior Composite Panel Made by Vacuum Bagging and Hand Lay-Up Fabrication Method
Authors: Kim Yun Hae , Eum Soo Hyun , Choi Byung Kyu , Kim Jin Chun , Kwon S.C. , Dutta P.K.
Published: March 2009

Recently, composites are widely used for interior panel of the transportation facilities such as
railway vehicle, ships and aircraft, etc. These interior composites panels are often made by vacuum
bagging, hand lay-up method and autoclave, etc. In this study, we carried out tests for the
evaluation of material properties of the panels under more severe conditions than real environment
to evaluate the dimension stability of the interior composite panels. Two sets of panels, one made
by hand lay-up method with glass mat/polyester resin (Type 1), and the other, by vacuum bagging
method with epoxy prepreg/NOMEX (Type 2) are exposed to the low temperature, high
temperature and room temperature. And then we measured the dimensions of the strained panels.
To monitor the characteristics of cured resin, we used DSC (Differential Scanning Calorimeter). It
was observed that Type 2 has higher mechanical properties and dimensional stability than Type 1.
Predictions of Elastic Properties of Multi-Axial Warp Knitted Fabric Composites
Authors: Chun Heoung Jae , Ryu K.S. , Byun Joon Hyung
Published: March 2009

An analytical model was proposed to predict the elastic properties of multi-axial warp
knitted (MWK) fabric composites for three-dimensional structures. The characteristics of MWK fabric composites are the assemblage of multilayers of rovings in the warp, weft and bias directions for in-plane reinforcement and out-of-plane stitches by knitting rovings to provide through-the- thickness reinforcement. For analysis, a representative volume of the MWK fabric composite was identified. The geometric limitations, effects of stitch fibers and design parameters of MWK
composites are considered in the model. Then, the elastic properties of MWK fabric composites are predicted by using an averaging method. The experiments are also conducted on the MWK fabric composites to compare the predicted results with the experimental results for the verification of suggested model. The predicted elastic properties are in reasonably good agreement with the experimental values. Finally the effects of design parameters of the MWK fabric composites are discussed.
Effect of Surface Nano-Crystallization on Microstructure and Mechanic Properties of Commercial Pure Titanium
Authors: Wen Ai Ling , Ren R.M. , Wang Sheng Wu , Nishida Shinichi
Published: March 2009

The paper investigated nano-crystallization on surface layer of commercial pure titanium by using high-energy shot peening. The grain size and the microstructure in deformed surface layer by high-energy shot peening are analyzed with X-ray diffraction and TEM etc. In addition, the variations of surface microhardness are examined after high-energy shot peening. The results described that the nano-crystalline surface layer have been formed in commercial pure titanium with a structure of hexagonal closet packet, by high-energy shot peening. The surface microhardness increases and the grain size in nano-crystalline surface layer diminishes, with increasing the time in high-energy shot peening. The minimum nano-crystalline grain size is approximately 40 nm.
Measurement of Elastic Constants for Composite Materials by 3-Point Bending, Twisting and Impact Sound Test
Authors: Yoshida Tsutomu , Matsui Shin-ichi , Hoshino Mitsuo , Sakata Masaru
Published: March 2009

Analyzing a sound produced by an impact of a fallen ball upon a small rectangular bar specimen, elastic moduli of engineering ceramic composites can be determined. In this paper,three-points bending and torsional test devices which employed the specimen for the impactsound test were designed. Using the devices, elastic moduli of various materials were mea-sured applying deformation theory. The elastic constants evaluated by the impact sound testwere compared with those measured by the devices. They agreed well. A reliable measure-ment system was developed for elastic constants of anisotropic materials.
Influence of the Material and Thickness of the Specimen on an Infrared Stress Image
Authors: Machida Kenji , Gheni Mamtimin
Published: March 2009

The thickness dependency of the temperature image obtained by an infrared thermography was investigated using specimens with three kinds of materials and four kinds of the thickness of the specimen. Only the sum of the principal stresses which is the first invariant of stress tensor is measured, and it is impossible to measure individual stress components directly. Then, the infrared hybrid method was developed to separate individual stress components. Although the form of the
contour line of low stress side differs greatly, the distribution form of high stress side was considerably alike. The stress intensity factor of material with low thermal conductivity can be estimated with high accuracy by the infrared hybrid method. On the crack problem, it was elucidated that the influence of thermal conduction is large and an inverse problem analysis is required.
Effects of Major Parameters on the P-T Limit Curve Construction of Embrittled Reactor Vessel
Authors: Jung Sung Gyu , Park In Gyu , Lee Chang Soon , Jhung Myung Jo
Published: March 2009

To prevent the potential failure of the reactor pressure vessel (RPV), it is requested to operate RPV according to the pressure-temperature (P-T) limit curve during the heat-up and cool-down process. The procedure to make the P-T limit curve was suggested in the ASME Code but it has been known to be too conservative for some cases. In this paper, the conservatism of the ASME Code Sec. XI, App. G was investigated by performing a series of sensitivity analyses. The effects of six parameters such as crack depth, crack orientation, clad thickness, fracture toughness, cooling rate, and neutron fluence were analyzed. The results of P-T limit curves are compared to one another.
Influence of Imperfect Interface on the Propagation of Love Waves in Piezoelectric Layered Structures
Authors: Jin Feng , Kishimoto Kikuo , Qing H. , Inoue Hisahiro , Tateno Takashi
Published: March 2009

Layered structures, especially thin film/coating substrate system play important roles in micro-electro-mechanical system (MEMS) and microelectronics packages. Many surface acoustic wave (SAW) devices/sensors adopt the layered structures to achieve high performance that with a piezoelectric layer deposited on the substrate.
Recently, much work has been carried out concerning the propagation behavior of surface waves in piezoelectric layered structures, in which the piezoelectric layers are bonded perfectly with the substrate materials. Actually, due to the thermal mismatch, the unavoidable initial stress in the piezoelectric layer and the brittleness nature of piezoelectric ceramics, imperfections exist in the interfaces of these layered structures. Due to the penetration properties of surface waves, the
imperfect interfaces may influence the propagation behavior of surface waves. Up to now, little attention has been paid to the propagation behavior of surface waves in layered piezoelectric structures that the imperfect interfaces are taken into account.
The propagation behavior of Love waves in a piezoelectric layered structure with imperfect interface is taken into account. Solutions of the mechanical displacement and electrical potential function are obtained for the piezoelectric layer and substrate, respectively, by solving the coupled electromechanical field equations. Effect of imperfect interface on the phase velocity of Love wave propagation is discussed in detail.
Results obtained indicate that imperfect interface can greatly influence the propagation of Love waves under some certain conditions. The potential application of these results in the field of mechanical behavior of materials is also shown.
Development of a Material Constitutive for High-Rate Using a Combined Experiment/Computation Method
Authors: Lu J.F. , Zhuang Zhuo , Shimamura K.
Published: March 2009

To describe the high-rate behaviour of metals, a revised form of the classic Johnson-Cook strength model with unknown material constants has been used. The 1D stress-strain relations as well as the effects of strain, strain rate and temperature are examined by Split Hopkinson Pressure Bar (SHPB) test. The undetermined material constants are solved using a variable-dissociation method. The element failure criterion based on maximum equivalent strain is also introduced to estimate the material failure behavior under high strain rate. A corresponding user-defined material subroutine (UMAT) has been developed for revised Johnson-Cook model, which is implemented into ABAQUS. Using this implicit scheme, several groups of finite element simulations under different strain rates are completed in ABAQUS/Standard. The results agree well with the test data and other results by explicit code.
A Study on Dynamic Fracture Behavior of Magnesium Alloys under Biaxial Stress
Authors: Shimamoto Akira , Kubota Ryo
Published: March 2009

In this study, dynamic behavior of the crack under dynamic biaxial stress was investigated concerning of these situations. Specimen shape was assumed to be a biaxial fracture, and the load device was with a hydraulic high-speed biaxial experiment device, which this laboratory had developed. Dynamic stress intensity factors and strain behaviors in the crack tip, angle of the pre-crack and crack propagation direction, and relate about the dynamic fracture toughness value under a dynamic biaxial stress was studied.
Mixed Mode Effects on the Interfacial Crack Propagation
Authors: Choi B.S. , Lee Chia Yen , Chai Young Suck
Published: March 2009

Initiation and propagation of interfacial crack along bimaterial interface are considered in this study. A series of interfacial crack initiation and propagation experiments are conducted using the biaxial loading device for various mixed modes. Normal crack opening displacement (NCOD) is measured near crack front by a crack opening interferometry and used for extracting fracture parameters. From mixed mode interfacial crack initiation experiments, large increase in toughness
with shear components is observed. Initial velocity of crack propagation is very dependent upon the mode-mixes. It increased with positive mode-mix due to the increase of stress singularities ahead of crack front and decreased with negative mode-mix resulting from the increase of the degree of compressive stress behind the crack front. Crack propagation was less accelerated with positive mode-mix than the negative mode-mix.
Observation of Heat Cycle Delamination Process with Surface Strain Measurement in Thermal Barrier Coating
Authors: Waki Hiroyuki , Nishikawa Izuru , Ogura K.
Published: March 2009

A surface strain measurement approach to understanding of delamination processes of thermal barrier coatings (TBCs) under heat cycle conditions was described in this paper. Heat cycle tests between the high temperature ranged from 1473K to 1073K and the relatively low temperature (573K) was carried out on thermal barrier coated type 304 stainless steel specimens. 8mass%Y2O3-
ZrO2 and Al2O3 coatings were used for the TBCs. The surface strain behavior during the heat cycle test was measured using a laser speckle strain/displacement gauge (SSDG). It was found that the thermal expansion of a substrate was almost reflected on a surface strain if a delamination wasn't initiated, while the value of a surface strain decreased to the value of the thermal expansion of a ceramics-coating if the delamination of the ceramics-coating was initiated. The state of a subsurface delamination was able to be nondestructively inferred by the surface strain behavior. The delamination life of a ceramics-coating in the specimen with a low-pressure-plasma-sprayed (LPPS)
bond-coating was found to be longer than that with an atmospheric-plasma-sprayed (APS) bond-coating. The large roughness of a bond-coating was also found to be effective in improving the delamination life of a ceramics-coating owing to the restriction of a crack propagation parallel to the interface between the ceramics-coating and the bond-coating.
The Effect of an Imperfect Interface on the Singular Stress Field of an Orthotropic Bimaterial Wedge
Authors: Leungvichcharoen Somsak , Wijeyewickrema Anil C.
Published: March 2009

In this analysis, the effect of an imperfect interface on the stress singularity of an orthotropic elastic bimaterial wedge subjected to traction free boundary conditions, is investigated, where the planes of symmetry are aligned, and one symmetry plane is along the interface and another symmetry plane coincides with the cross-sectional plane. The Stroh formalism with the method of separation of variables are used to obtain the relevant expressions for displacements and stresses. At the interface, only the interfacial tractions and the displacement normal to the interface are assumed to be continuous. The imperfect bond is modeled using a local coordinate system, where each tangential traction component in this local coordinate system is directly proportional to the corresponding displacement discontinuity and inversely proportional to the distance from the wedge apex. The order of singularity is computed numerically for graphite/epoxy wedges and presented for various imperfect interface conditions. The numerical results agree with the available results for the fully bonded case. It is expected that when the axes of local and global coordinate systems are aligned, that the in-plane and antiplane problems are uncoupled, and this feature also can be seen in the numerical results.
Anti-Plane Interface Edge Crack between Two Dissimilar Piezoelectric Blocks
Authors: Liu Shu Hong , Zou Z.Z. , Xu B.Q. , Zhang Z.G.
Published: March 2009

The problem of an interface edge crack between two dissimilar piezoelectric materials is analyzed under the conditions of anti-plane shear and in-plane electrical loading. The crack is considered to be traction-free, but electric permeable one across which the normal component of the electric displacement are continuous. A series form of electromechanical solution and field intensity factors are obtained. The results show that all fields including strain, stress, electric field strength and electric displacement are singular in the front of crack tip. At last, the stress intensity factor is solved by the boundary collocation method (BCM), numerical results are given and discussed.
A 3D Finite Element Model of a Knee for Joint Contact Stress Analysis during Sport Activities
Authors: Bratianu Constantin , Rinderu Paul , Gruionu Lucian
Published: March 2009

A 3D finite element model of a human knee was constructed to study the response of
articular tissues to loads applied to the surface of the femur similar to normal and extreme movements of the joint as in sports activities. A solid model of the femoral and tibial cartilages and menisci were built from post mortem MR images of human knee at full extension using the Pro/Engineer software package. The knee kinematics data was registered for this model and successive articular surface positions were obtained as a function of flexion angle. The cartilage and menisci were modeled as nonlinear orthotropic materials and contact elements were used to
compose the contact layer between articular surfaces. The model determined average contact areas and stress values, which were then compared with published experimental results for equivalent boundary conditions. The presence of menisci increased the contact area in the knee joint, thus creating lower contact stresses on the cartilage than those measured experimentally. Validation of results allows the utilization of 3D knee model for determining the contact areas and the contact stress field for diverse bones positions simulating sports activities.
Development of Orthotropic Beam Element Using a Consistent Higher Order Deformation Theory
Authors: Lim Jae Kyoo , Han Seok Yoon
Published: March 2009

In order to analyze beam structures more accurately and effectively, a two-node orthotropic beam element is proposed. This beam element is formulated using a consistent higher order deformation theory of orthotropic beams of which the transverse normal deformation can be effectively estimated. The stiffness matrix and the vector of equivalent nodal forces of the beam element are derived explicitly by the Galerkin method. In order to examine the reliability and the characteristics
of the beam element, the analytical and the finite element solutions of a simple cantilevered beam are compared with each other. As a result, the following conclusions are obtained; (1) the accuracy of the suggested orthotropic beam element is very excellent and so the transverse normal deformation and shear stress of an orthotropic beam can be effectively estimated. (2) It can be used
for accurately analyzing the general beam structures regardless of the Euler's or the Timoshenko's beam.
Application of Numerical Manifold Method to P-Version Adaptive Analyses
Authors: Zhang Guang , Chen Jing Xi , Pan Dong Zi
Published: March 2009

This present paper makes preliminary discussions on the application of Numerical Manifold Method to P- version adaptive analysis and deduces the displacement functions with various orders in elements and the expression of element's stiffness matrix, and codes the program for adaptive analysis with language C. Two numerical examples are studied and their results verity that the method and programs being given on this paper are accurate.
Application of Fracture Mechanics to Arch Dam Analysis
Authors: Yang Shui Cheng , Song Li , Liao Hong Jian
Published: March 2009

The authors present a procedure for the analysis of the stability and propagation of cracks in arch dams based on linear elastic fracture mechanics. A finite element method was used to calculate the stress intensity factors(KⅠ, KⅡ and KⅢ) of crack in the concrete arch dam, and fracture analysis for arch dams was carried out, which based on the criterion of three-dimensional mixed mode fracture of concrete from the experiment. The analysis method can be applied to evaluate the safety of the arch dam and improve the design for arch dam.
A Fractional Two-Step Finite Element Formulation for Unsteady Free Surface Flow Using ALE Method
Authors: Li Q. , Liu H.Z. , Zhuang Zhuo , Yamaguchi S. , Toyoda Masao
Published: March 2009

A numerical algorithm using equal-order linear finite element and fractional two-step method is presented in this paper, which is used for analysis of incompressible viscous fluid flow with free surface problems. In order to avoid severe mesh distortions, ALE method is used for dealing with the free surface sloshing. For numerical integration, the fractional step method is employed, which is useful because the same linear interpolation functions for both velocity and pressure could be carried out in the finite element formulation. The present algorithm has been applied to some examples and proved to be accurate and more efficient.
Equivalent Finite Element Modeling of Thick Composite Structures for Analysis of Composite Hingeless Hub System
Authors: Park Hoon Cheol , Rachmadini Yanti , Lim Sang Min , Lee Sang Ki , Yoon Kwang Joon , Joo Gene , Kim Deog Kwan , Lee Myeong Kyu , Hong Dan Bi
Published: March 2009

Finite element analysis for thick composite structures is rather complicated. Two-dimensional modeling, which is relatively easy to make, can cause inaccurate result since the plane stress condition cannot be applied, while three-dimensional modeling is hard to make. In the three- dimensional modeling, it is difficult to model all the layers with different material properties and ply orientation in the structure. In this paper, an equivalent modeling is proposed and numerically tested for analysis of thick composite structures. The method has been verified for the modeling of
composite plate and circular composite tube in order to find their bending deflection and natural frequency. MSC/NASTRAN and PATRAN are used for the calculation. It has been confirmed that three-dimensional analysis must be conducted for thick structures and the equivalent modeling is proven to be accurate when layers with same characteristics are properly grouped.
The proposed modeling technique has been applied to analyze hingeless composite rotor hub system designed by Korea Aerospace Research Institute (KARI). Detailed three-dimensional modeling for this structure is almost impossible to make due to its complex geometry of thick composite structures. Using the proposed equivalent modeling technique, failure analysis was performed based on stress/strain criterion and the safety of each part was checked. Deflection of the
hub system was validated comparing with the result from the simple analytical beam model, and the numerical result will be used for the next design cycle of the composite hub system.
A Study on the Stability Analysis According to Hinge Condition of Micro Stage for Micro Cutting Machine
Authors: Kim Jae Yeol , Kwac Lee Ku , Han Jae Ho
Published: March 2009

Recently, the world is preparing for new revolution, called, ‘IT(Information Technology), NT(Nano-Technology), and BT(Bio-Technology).’ NT can be applied to various fields such as semiconductor-micro technology. Ultra precision processing is required for NT in the field of mechanical engineering. Because of radical advancement of electronic and photonics industry, necessity of ultra precision processing is on the increase for the manufacture of various kernel parts. In this paper, stability of ultra precision cutting unit is investigated and this unit is the kernel unit in ultra precision processing machine. According to alteration of shape and material of hinge, stability investigation is performed.
Hinge shapes of micro stage in UPCU (Ultra Precision Cutting Unit) are designed in two types, where, hinge shapes are composed of round and rectangularity. Elasticity and strength are analyzed on micro stage with respect to hinge shapes by FE analysis.
The micro stage in ultra precision processing machine has to keep hinge shape under cutting condition with 3-component force (cutting component, axial component, and radial component) and to reduce modification against cutting force. Then we investigated its elasticity and strength under these conditions. The material of the micro stage is generally used for duralumin with small thermal deformation. Since the elasticity and the strength quiet become important, the stability of the micro stage is investigated. Used materials are composed of aluminum of low strength and cooper with medium strength and spring steel with high strength.
Through this stability investigation, trials and errors are reduced in design and manufacture at the same time, and we are accumulated foundation data for a unit control.
Buckling of Functionally Graded Circular/Annular Plates Based on the First-Order Shear Deformation Plate Theory
Authors: Ma L.S. , Wang Tie Jun
Published: March 2009

Based on the first-order shear deformation theory of plate, governing equations for the axisymmetric buckling of functionally graded circular/annular plates are derived. The coupled deflections and rotations in the pre-buckling state of the plates are neglected in analysis. The material properties vary continuously through the thickness of the plate, and obey a power law distribution of the volume fraction of the constituents. The resulting differential equations are numerically solved by using a shooting method. The critical buckling loads of circular and annular plates are obtained, which are compared with those obtained from the classical plate theory. Effects of material properties, ratio of inter to outer radius, ratio of plate thickness to outer radius, and boundary conditions on the buckling behavior of FGM plates are discussed.
Elastic Web Buckling Strength of Pultruded Flexural Members
Authors: Yoon Soon Jong , Jung Jae Ho , Jang Won Sup
Published: March 2009

This paper presents the analytical investigations pertaining to the elastic buckling behavior of orthotropic composite plates. By the pultrusion process the structural shapes composed of orthotropic plate components are readily available in the construction market. When the member is utilized for the flexure, lateral-torsional buckling and local buckling behaviors must be taken into consideration. In the local buckling analysis, flange and web local buckling analyses must be conducted in the design of such a member. For finding the web buckling strength, the buckling
equation for the orthotropic plate under linearly distributed in-plane forces is derived by using the Rayleigh-Ritz method. The boundary conditions of plate are assumed that the loaded edges are simply supported and the unloaded edges are simply supported or fixedly supported. The buckling coefficient of a plate having different orthogonal mechanical properties is found by using the numerical technique and the minimum buckling coefficient is suggested. In addition, simplified form of equation for predicting the minimum buckling coefficient for the plate is proposed. Brief discussion on the design criteria relating to the web local buckling is also provided.
Elastic Local Buckling of Transversely Isotropic Thin-Walled Compression Members with Varying Thickness
Authors: Jeong S.K. , Yoon Soon Jong , Cho Sun Kyu
Published: March 2009

The problem addressed in this paper is the elastic local buckling of thin-walled compression members whose plate components are tapered in thickness along the longitudinal direction. In the design of structural system in construction, shipbuilding, and aerospace industries, such structural plate components are frequently encountered. The elastic buckling analysis of transversely isotropic plates with varying thickness and various boundary conditions is performed to derive the buckling equation of thin-walled members composed of tapered plate components. In the analytical solution, the energy approach is adopted. The analytical results are presented in a graphical form in which the plate buckling coefficients are suggested with respect to the width ratio of plate elements and the degree of taper. In addition, using the buckling equations of plates with specific boundary conditions, the simplified form of equation for the local buckling coefficient of structural members
such as L-section, T-section, and Box-section is suggested.
An Analysis of the Local Buckling Collapse Behavior of an Aluminum Square Tube under Concentrated Bending Moment Loads
Authors: Lee Sung Hyuk , Choi Nak Sam
Published: March 2009

To analyze the bending collapse behavior of an aluminum square tube under the bending moment load, a finite element simulation for the four-point bending test has been performed. Using an aluminum tube beam specimen partly inserted with two steel bars, local buckling deformation near the center of the tube beam was induced. Simulated moment-rotation angle curve obtained during the post-collapse period of the aluminum tube with steel bars were in good agreement with experimental result, which was comparable to the result obtained from Kecman's theory. Using a
combination of the four-point bending test and its finite-element simulation, analysis of the local buckling and the bending collapse behavior of an aluminum tube beam could be quantitatively accomplished.
Thermo-Mechanical Behaviors of Ceramic-Coated Structures in Outer Space Using Partial Model Technique
Authors: Kwon Young Doo , Choo S.W. , Lee J.K. , Kim J.Y.
Published: March 2009

Generally, structures used in outer space are subjected to severe situations, including sublimation, a strong evaporation of lubricants, thermal stresses, high temperature gradients, irradiation, impact from microscopic meteorites, and other factors. Recently, various kinds of coatings have been applied to structural parts under heavy contact stresses to ensure a longer wear-free life and/or reduce the friction coefficients. Accordingly, the current study applied FEM to analyze space parts with a coating layer thermo-mechanically subjected to a contact load.
First, a steady state temperature distribution of the space part was obtained, then a quasi-static external load was applied. Thereafter, the total solution was computed and the thermal strain subtracted to obtain the mechanical strains for determining the stresses of the individual part. When using FEM, the model needs to discretize into many sub-domain finite elements. Since the difference, however, in the dimension between the coating layer and the substrate is so large, the analysis needs to be considered carefully. Consequently, the problem was analyzed in two steps. First, the whole model was analyzed using rather coarse meshes, then a small region was cut near the loading point and analyzed using very fine meshes. This method is based on Saint-Venant's principle. Finally, the effect of a thermal load on the stress of a space part with a coating layer was checked with and without cracks in the substrate. Accordingly, the results demonstrate the stresses on a space part under a thermo-mechanical load, along with the effects of various coating materials and a crack in the substrate on the stress distribution.
Stress Intensity Factors of an Infinite Solid with Two Cavities having a Crack Emanating from the Cavity under Tension
Authors: Nisitani Hironobu , Teranishi T. , Fukuyama K.
Published: March 2009

It is important to know the stress intensity factor of a circumferential crack emanating from the cavity, because in some cases the fatigue strength of metals is affected by the existence of an internal cavity or an inclusion. Recently a method for calculating the highly accurate values of stress intensity factors was proposed by H. Nisitani, based on the usefulness of the stress values at a crack tip calculated by FEM. This method is called the crack tip stress method. In this study, the crack tip stress method is applied to the problem of an infinite solid having two cavities with a circumferential crack emanating from the cavity subjected to tension. The accuracy of the crack tip stress method was discussed based on some values obtained by the body force method. Moreover, a simple method for calculating the stress intensity factor of this problem was presented.
Dimple Fracture Simulation of Fracture Specimen under Different Constraint Conditions
Authors: Kikuchi Masanori , Sasaki Jun , Ishihara Takehito
Published: March 2009

Three kinds of fracture specimens are tested under different constraint conditions. One is 3PB(Three Point Bending) specimen, another is CCT(Center Cracked Tension) specimen, and the third one is called CCB(Center Cracked Bending) specimen. By the SEM (Scanning Electron Microscope) observation, it is shown that the roughness of fracture surface is different from each other largely. They are the effect of constraint condition. The dimple fracture process is simulated by the finite element method using Gurson's constitutive equation, and the crack tip stress fields are obtained. The distributions of stress triaxiality components are qualitatively agree with the experimental results. The J-R curves obtained also qualitatively agree with those of experiments, and the fracture surface roughness is well simulated.
Dislocation Dynamics Simulation of Grain Boundary Effects on Yield Behavior of Metals
Authors: Takahashi Akiyuki , Soneda Naoki , Nomoto A. , Yagawa G.
Published: March 2009

This paper describes dislocation dynamics simulation of grain boundary effects on yield behavior of metals, such as α-Fe bcc metal. Since the stress field arising from the grain boundary has not been well understood yet, the geometrical effect of the grain boundary can be handled in the simulation by the use of rigid boundary condition. The dislocation pileups can be observed near the grain boundary in the result of the DD simulation. And the yield stress in the crystal having the grain boundary becomes larger than that in the crystal having free surface. This result tells us that the Hall-Petch effect can actually describe well the effects of the grain boundary on the yield behavior of metals.
Quantitative Analysis on Parameters of a Defect with Speckle Interferometry and Finite Element Optimization Method
Authors: Wang Kai , Li Xi De
Published: March 2009

Quantitative nondestructive testing (QNDT) is required for the in-service inspection of high-cost structures whose failure could lead tragic consequences. The optical methods are widely used for NDT and NDE. However, most of them base on the qualitative detection of the partial fringes induced by the defects. The defect characteristic parameters (DCPs), such as coordinates and types, are easily obtained, but it is difficult to obtain other parameters, e.g. the defect size and embedded depth due to the non-unique relation between the DCPs and the deformation of detected defects. In this paper, the optical method, design optimization and FEM are combined to accomplish QNDT. Three types of defects are inspected and their DCPs values are obtained quantitatively. Moreover, factors that influence detection accuracy of the DCPs are also discussed.
Development of a Knowledge-Based Information Management System for Plant Maintenance
Authors: Park Young Jae , Lee Sang Min , Yim H.S. , Choi Jae Boong , Kim Young Jin , Roh E.C. , Lee B.I.
Published: March 2009

In this paper, a knowledge-based information system for the plant operation of steel making company has been proposed. The system, which is named as K-VRS(Knowledge-based Virtual Reality System), provides a connection between ERP plant maintenance module and knowledge-based engineering methodologies, and thus, enables network-based highly effective plant maintenance process. The developed system is expected to play a great role for more efficient and safer plant maintenance.
Sensitivity Analysis of Joints' Effects on Damage Zones in Surrounding Rockmass
Authors: Chen Jing Xi , Zhang Guang , Hu Bin
Published: March 2009

This present paper, taking a large-scale underwater power station in China as background engineering works, carries out sensitivity analyses of various parameters of jointed rockmass on the scope of damage zones in the rockmass surrounding the works. It gives major sensitivity parameters and discusses the trend and possibility of these parameters’ effect on the damage zone of surrounding rocks as well as makes some suggestions on the exploration and construction
Electrochemical Potentiodynamic Reactivation: Development and Applications of the EPR Test
Authors: Číhal Vladimír , Štefec Rudolf , Shoji Tetsuo , Watanabe Yutaka , Kain Vivenakand
Published: March 2009

The EPR test, designed to examine of the susceptibility to nonuniform, primarily intergranular corrosion, ranks among the more successful testing technique developments relating to stainless steels and alloys. One of its numerous advantages is that it lends itself to non-destructive, on-site examination. EPR enjoyed wide expansion over the years since first conceived by Čihal in 1969. Recent EPR measurements tend to focus on (1) double and/or single loop EPR as a modern technique used to establish the resistance of stainless steels and
alloys to intergranular corrosion; (2) detecting integranular corrosion (IGC) and intergranular stress corrosion cracking (IGSCC) susceptibility in alloy steels and nickel alloys for nuclear engineering applications; and (3) studies of grain boundary precipitation and other minute local changes to alloy composition and structure.
Effects of Environmental Factors on the Electronic Properties of Interfacial Oxide Film on 304L Stainless Steel in High Temperature Pure Water
Authors: Lu Zhan Peng , Takeda Yo-ichi , Shoji Tetsuo
Published: March 2009

The electronic properties of the interfacial oxide film formed on 304L stainless steel in high temperature water are investigated by contact electric resistance (CER) measurements. Tests are performed in pure water with a wide range of dissolved oxygen (DO) content at 200, 250, and 288°C. The electrochemical potential (ECP) moves in the noble direction and CER increases when increasing DO. Results show that DO content has a dominant effect on the electronic properties of
oxide film. The change of oxide film properties can also be attributed to the variation of the electrochemical potential, which is directly affected by DO content. Critical potentials exist for the formation and reduction of oxide films in high temperature water. Multiple steps are found for the reduction of oxide films due to de-aeration in 200, 250, and 288°C water, implying the presence of multiple-layer interfacial oxide films. The film reduction process is relatively slower than the film formation process. Present results show that even in high purity water, a moderate change of DO
content can result in different surface conditions. Dissolved hydrogen has a moderate effect on interfacial surface films in deaerated water. In-situ monitoring of the oxide film properties by CER technique provides information on the interfacial reactions that are related to the SCC behavior of materials in high temperature water environments.
Development of Novel Non-Destructive Inspection Technique Using High-Frequency Signal Transmission Characteristics
Authors: Baba Toshimitsu , Ogawa Kazuhiro , Shoji Tetsuo
Published: March 2009

A novel non-destructive inspection (NDI) technique that utilizes high-frequency signal transmission characteristics was developed as a more reliable, faster and cheaper NDI technique. This technique forms a transmission circuit that includes the specimen, and detects the signals generated by any surface breaking-defect.
In this research, quantitative measurement of closed fatigue cracks was implemented via a newly developed probe. The greatest advantage of this technique is that there is no significant difference in detection of defects in either paramagnetic materials or in ferromagnetic materials. Therefore, the potential effects of corrosion, ferrite content, or deformation martensite on the measurement signals are minimized, and a better S/N ratio can be expected. This technique can also be used to measure
the size of defects in components, including welded components, and its detection sensitivity is less than 1 mm for surface breaking-defects.