bluuebunny/crossref_metadata_2025 huggingface dataset:
Textures Evolution of Rolled AA5182 Alloy Sheets after Annealing
Authors: Kim Kee Joo , Kim Joo Sung
Published: March 2009

To fabricate the aluminum alloys with good drawability, the textures evolution of the
AA5182 sheets after rolling and subsequent annealing was studied. The measurement of the
deformation textures was carried out for the sheets with high reduction ratio and the change of the
recrystallization texture was investigated after heat-treatments of the rolled sheets. Rolling without
lubrication and subsequent annealing led to the formation of favorable rot-CND {001}<110> and
γ-fiber ND//<111> textures in AA5182 sheets. From the results, the γ-fiber ND//<111> component
well evolved during rolling at high reduction ratio. Among shear deformation textures, the γ-fiber
ND//<111> was not rotated in holding time until 7,200 seconds at 350. The Monte-Carlo technique
was used and could be representatively simulated textures evolution during recrystallization.
Structural Safety Evaluations of Bogie Frames for Rubber-Tired AGT Vehichles
Authors: Kim Yeon Su , Park Sung Hyuk , Jeong Rag Gyo , Lim Tae Kon
Published: March 2009

This study was aimed at evaluating the structural safety of the new bogie frames for
Korean-standardized rubber-tired AGT vehicles. The guidance frame and the rotation frame were
designed according to Korean-standardized specifications for rubber-tired AGT vehicles, and their
stresses were analyzed by using the finite element method. Based on the results of the analysis,
dynamic stresses were measured while the train was running under various conditions in the test track.
Analytical and experimental results verified the structural safety of the new bogie frames.
Formulation of Reliability-Based Fatigue Assessment of a Car Body for a High Speed Train Passing Through Tunnels
Authors: Park Choo Soo , Seo Sung Il , Choi Sung Hoon , Mok Jin Yong
Published: March 2009

In designing the structures of railway rolling stocks, deterministic methods associated with
the concept of a safety factor have been traditionally used. The deterministic approaches based on the
mean values of applied loads and material properties have been used as safety verification for the
design of the car body structures. The uncertainties in the applied loading for the high speed train and
the strength of new materials in the structure require the application of probabilistic approaches to
ensure fatigue safety in the desired system. Pressure loadings acting on the car body when the train
passes through tunnels show reflected pressure waves for high-speed trains and they may cause a
fatigue failure in vehicle bodies. In this paper, it is proposed that a fatigue design and assessment
method based on a structural reliability that deals with the loading of pressure variations on a railway
vehicle reflected in tunnels and the strength variations of material. Equation for the fatigue reliability
index has been formulated to calculate the reliability assessment of a vehicle body under fluctuating
pressure loadings in a tunnel. Considered in this formulation are the pressure distribution
characteristics, the fatigue strength distribution characteristics, and the concept of stress-transfer
functions due to the pressure loading.
Application of the Refined Mesh Method for the Strength Estimation around Openings
Authors: Lee Kyung Seok , Song Jae Young , Kim Kyung Su , Kim Sung Chan , Kim Jung Hee
Published: March 2009

It is not easy to solve the troubles around the openings at the detail design stage, because
there are a lot of concerning locations. There are not also clear design rules of classification societies.
For more detailed strength analysis around holes on the longitudinal girder or transverse web below
deck plate, it is also very difficult to decide the boundary condition (B.C) at both ends. Grillage
analysis, which considers B.C and more detailed member arrangement, is used in simple analysis.
Furthermore, refined mesh method, which use a part of member in the strength analysis, is used to
decide S.I.Fs around holes. Component loads are applied to a refined mesh model separately and
S.I.Fs according to component loading are calculated. S/F and B/M are decided from the grillage
analysis and S.I.F for a given hole location is deduced from database and the results of grillage
analysis.
Development of a Partial Blockage Detection Algorithm through Temperature Fluctuation Analyses in a Liquid Metal Reactor
Authors: Seong Seung Hwan , Jeon Won Dae , Hur Seop , Kim Seong O
Published: March 2009

If an assembly is partially blocked, the temperature in the upper plenum fluctuates at an early stage without a significant temperature increase. Therefore, the temperature fluctuation in the upper plenum can detect a partial blockage of an assembly. For developing the detection algorithm for a partial blockage, we numerically analyzed the temperature fluctuation in the upper plenum due to a partial blockage in an assembly. For analyzing the time dependent turbulence variables, the LES (Large Eddy Simulation) turbulence model in a commercial code was used. After analyzing the temperature fluctuations in the upper plenum, we studied the change of its characteristics according to the blocked conditions through some FFT analyses and statistical analyses. We found that the change of the skewness of the temperature fluctuation was the most significant parameter to detect a partial blockage and that its highest frequency is about 15Hz at 10cm beyond the exit of the assembly. Also, we have suggested that the resolution of the thermocouple should be less than 2 K in order to measure the fluctuated values of the temperature and that the response time of the thermocouple was less than 30ms.
Reliability-Based Assessment of Bridges Using Long-Term Monitoring Data
Authors: Ni Yi Qing , Hua X.G. , Ko Jan Ming
Published: March 2009

In this paper a method for safety and condition assessment of bridge components based on
long-term monitoring data and reliability analysis is proposed with the target to provide quantitative
information to bridge managers for decision making on optimizing and prioritizing bridge inspection
and maintenance. In the proposed method, the probability density function (PDF) of the load effect is
obtained directly from continuous strain measurement, while the PDF of the resistance is determined
using the material strength and its variation coefficient prescribed in provisions or obtained by
material tests, and further revised with the damage identification results. Then the safety indices of
structural components are estimated using the first-order reliability method (FORM), which can be
readily used to decide bridge inspection/maintenance strategy because the correspondence between
the safety index and the required maintenance action has been established. This method can
incorporate the identified structural damage in a probabilistic manner into the safety index evaluation.
Case studies of two truss bridge structures have been provided to illustrate the proposed method.
Embedded Fibre Bragg Grating Sensors for Internal Fatigue Damage Monitoring in Polymeric Composites
Authors: Shin C.S. , Chiang C.C.
Published: March 2009

This work aims at assessing the use of embedded fiber Bragg grating to monitor the
internal damage evolution in polymeric composite during fatigue loading . The results suggested
that the embedded FBGs have good potentials to detect the appearance of damage and to
differentiate the damage types. The evolution in light spectrum during fatigue may be divided into
four stages when compared against X-ray, C-scan and optical microscope (OM) results. These
stages are associated with (1) matrix cracking in 90o lamina; (2) fiber splitting in the ±45o laminae;
(3) fiber splitting in the 0o lamina ; and (4) delamination.
Calibration of an Impact Device and Its Application to the Normalized Spectral Analysis of Impact-Echo Tests
Authors: Lin Yi Ching , Yang Chun Kuei , Cheng Chia Chi
Published: March 2009

The objective of this paper is to introduce an impact device made by embedding a
piezoelectric sensor into a steel sphere and to develop a calibration method for measuring the impact
force. The force-time function of impact can be used to normalize the spectrum obtained from an
impact-echo test. Furthermore, an approach was proposed to make the normalized spectrum
dimensionless. A new technique based on the dimensionless normalized spectrum is developed to
quantitatively evaluate the difference in acoustic impedance at the interface between two dissimilar
materials. The impact-echo test results show that the dimensionless normalized spectrum is capable
of identifying the degree of the difference in acoustic impedance at the interface between two
dissimilar materials.
Nondestructive Characterization Hydrogen-Charged Zircaloy with a Laser Ultrasound Technique
Authors: Yang Che Hua , Lai Yu An
Published: March 2009

A laser ultrasound technique (LUT) is reported for nondestructive characterization of hydrogen concentration (HC) in Zr-4 cladding tubes. With the LUT, ultrasonic waves propagating in the Zircaloy tubes with different HC are generated and detected remotely by optical means. By measuring the dispersion spectra with the LUT, relations between the dispersion spectra and the HC of the Zircaloy tubes are established. HC ranging from 0 to 1200 ppm in the Zircaloy tubes are successfully discriminated by the LUT with a resolution of 200 ppm.
Prediction and Analysis of ECT Signals due to Tube Defects near Support Plate in Steam Generator
Authors: Shin Young Kil , Song Sung Chul , Jung Hee Sung , Lee Yun Tai
Published: March 2009

In this paper, absolute and differential eddy current signals from various shapes and sizes of
defects in the steam generator tube are numerically predicted and their slope characteristics are
investigated. The signal variations due to frequency increase are also observed. Then, the analysis of
mixed defect signals affected by a ferromagnetic support plate is attempted. Axisymmetric finite
element modeling is used for signal prediction and the slope angle of signal is used importantly in
analyzing the signal. Results show that differential signals are useful for locating the position of a
defect inside the support plate hole, while absolute signals are easy to presume and interpret even
though the effect of support plate is mixed in the signal. Understanding of respective signal
characteristics and relationship between them will be helpful for more reliable defect characterization.
Research on the Method for Drill Pipe Thread Inspection
Authors: Ding Jin Feng , Kang Yi Hua , Wu Xin Jun
Published: March 2009

Failure of the drill pipe thread is always a very serious problem which may result in serious accidents and rework during the drilling of oil wells. Rupture crack of the drill pipe thread may result in great economic and labour losses, so they need to be inspected periodically. As the drill pipe thread is not a smooth surface and is in the end area of drill pipes, it is very difficult to be inspected by traditional Non-destructive testing (NDT) methods. According to the experiment results and the requirement of the working conditions in the field, a local MFL inspection method, which is the most adaptive inspection method, is determined. Laboratory testing and field experience show that this inspection method can detect the crack as small as 0.6mm (depth) in the thread root and thus reduces the risks of drilling failure. This local MFL inspection method can inspect flaws of the drill pipe thread that occur in practice exactly and quickly, and it has very wide application perspectives.
Study for Evaluation of Surface Cracks on Tribological Coatings Failure in Contacting Systems
Authors: Moon Byung Young , Kim Byeong Soo , Kang H. K. , Chung S.W.
Published: March 2009

The use of linear and second order stress extrapolation to obtain KI and KII in
two-dimensional finite element models of a thick plate containing an edge crack was examined. Three
loading cases were studied, including classical Mode I and Mode II problems and a problem of
tribological contact. Linear extrapolation was observed to yield accurate predictions of KI in cases of
dominant Mode I loading. In Mode II situations, notably where the crack faces experienced
compressive normal stresses, second order extrapolation was observed to improve estimates of KII
Corrosion Fatigue Characteristics of Artificially Degraded CF8A Steel in 3.5 WT.% NaCl Solution
Authors: Jang Seong Cheol , Bae Dong Ho , Lee Gyu Young
Published: March 2009

CF8A steel is a material of the piping system in nuclear power plant. In order to evaluate
its fracture characteristics and degradation by corrosion, electrochemical corrosion and corrosion
fatigue characteristics were evaluated. CF8A steel was artificially degraded at 400°C for 3 months.
Corrosion rate of degraded CF8A steel in NaCl solution of room temperature increases with
concentration of NaCl solution increase. However, concentration of NaCl solution will be more than
4.0wt.%, it shows decreasing tendency. Crack growth rates of degraded and not-degraded CF8A
steel in air condition do not show remarkable difference. However, in 3.5wt.% NaCl solution, it
showed higher than that of in air.
Process Integration of Fatigue Analysis for Welded Bogie Frames
Authors: Han Seung Ho , Bang Je Sung , Rim Chae Whan , Lee Kwang Soon , Lee Kwang Ki , Song See Yeob
Published: March 2009

The automation of fatigue durability analysis for welded bogie frames according to the
UIC-code is proposed by using the ModelCenter, which enables several tools used in fatigue
durability analysis to be integrated, i.e. I-DEAS, ANSYS and BFAP, and an iterative analysis of
geometrical changes in transom support bracket to be performed. In additions wrapping programs to
control I/O-data and interfaces of these tools were developed. The developed automation technique
brings not only a significant decrease in man-hour required for durability analysis, but also provides a
platform for multidisciplinary engineering activities.
Evaluation of SCC Distribution by Means of Focusing Ultrasonic Angle Beam
Authors: Abe Toshihiko , Endo Hisashi , Takagi Toshiyuki , Uchimoto Tetsuya
Published: March 2009

Fatigue cracks and SCC (Stress Corrosion Cracking) on a back surface were detected, and
the shape of cracks were evaluated using a surface wave generated by focusing angle beam
ultrasound. Internal ultrasonic images showed a little shorter length than optical images. Cross section
of the fatigue crack and internal distribution of complicated shaped SCC were estimated.
Life Prediction of High Pressure Steam Turbine Rotor
Authors: Song Gee Wook , Kim Bum Shin , Hyun Jung Seob
Published: March 2009

The operation mode of thermal power plants has been changed from the base load to duty
cycle. From the changeover, fossil power plants cannot avoid frequent thermal transient state, for
example, start up and stop, which results in thermal fatigue damage at the heavy section components.
The rotor is the highest capital cost component in steam turbine and requires long outage for replacing
the new one. For optimized power plant operation life and inspection management of rotor is
necessary. It is known as general that start-up and shutdown operation greatly affect on steam turbine
life. The start-up operation condition is especially severe because of the rapid temperature and
rotational speed increase, which causes damage and reduction of main components life of steam
turbine. The start-up stress of rotor which is directly related life is composed of thermal and rotational
stresses. The thermal stress is due to the variation of steam flow temperature and rotational stress is
due to the rotation speed of itself.
In this paper, the analysis method of start-up stress of rotor which considers simultaneously
temperature and rotation speed transition is proposed, which includes a case study regarding 500MW
fossil power plant steam turbine rotor. Also, the method of damage quantitative estimation of fatigue
damage to operation condition is described. The method can be applied to find weak points to the
fatigue damage. Using the method, total life consumption can be obtained, and can be also used for
determining future operation mode and the life extension of old fossil power units.
SH Guided Wave Scattering in a Structure with Thickness Variation
Authors: Cho Youn Ho , Rose Joseph L. , Kwun He Geon
Published: March 2009

Presented in this paper is a numerical approach to extract useful features of SH guided
wave scattering in a Plate-like structure with thickness variation. The problem statement is chosen to
establish a physically based guideline for mode selection and data analyses in power industry
application. The hybrid BEM technique with absorbing boundaries on the structure cross-sections is
proposed to calculate reflection and transmission from thickness variation. Sample numerical data is
presented as a function of incident mode, frequency and defect geometry. Mode optimization is
proposed to enhance penetration power and quantify geometry change based on various interesting
features including reverberation pattern of scattering fields.
A Study on the Fracture Characteristics of Plasma-Treated Graphite/Epoxy Laminated Composites
Authors: Kim M.H. , Rhee Kyong Yop , Paik Young Nam , Ryu S.H.
Published: March 2009

For a present study, the surfaces of graphite/epoxy prepregs were modified using plasma
treatment to improve the delamination resistance behavior of graphite/epoxy laminated composites.
The optimal treatment time was determined by measuring the change of contact angle with treatment
time. Unidirectional DCB (double cantilever beam) specimens were used in the mode I delamination
fracture tests. The delamination resistance curve of regular (untreated) specimen was compared with
that of plasma-treated specimen in order to determine the effect of prepreg treatment on the resistance
behavior. It was found that contact angle was changed from ~64° to ~47° depending on the treatment
time. The contact angle was a minimum for a 30 min treatment time. It was also found that
delamination resistance behavior of graphite/epoxy composites was improved about 20%.
The Penetration Characteristics of CF/Epoxy Curved Sheller According to Stacking Sequence
Authors: Yang In Young , Cho Young Jea , Kim Young Nam , Heo Uk , Park Sang Guk , Im Kwang Hee , Kim Ji Hoon , Sim Jae Ki
Published: March 2009

Carbon fiber reinforced plastics, among the advanced composite material watched with
keen interests today, is widely used as structural components requiring light weight property because
of its high specific strength as well as high specific rigidity. However, this material has a drawback of
weakness against a transverse impact loading acting toward the direction of its stacked thickness,
which requires different design parameters other than those used for general metal products in actual
application. In connection with this point of view, this study utilized specimen of laminated
composite material shell having certain radius of curvature considering actual structural component
made of laminated CFRP composite material. Penetration experiment was conducted by measuring
time of penetration of steel ball between two points where ballistic-screen sensors were attached on
front and reverse side of the specimen with the air gun under air pressure that is adjusted by the
pressure gauge attached to. Critical penetration energy was found by measuring kinetic energies of the
steel ball before and after the penetration. In order to identify crack pattern and penetration mode
generated inside the specimen after the experimental penetration, this study used digitalized optical
microscope. Through this study, therefore, penetration characteristics by changes in number of layers,
by different stacking sequences as well as penetration mode have been observed.
Mechanical Property and Oxidation Behavior of LPS-SiC Materials
Authors: Lee Sang Ll , Shin Yun Seok , Lee Jin Kyung , Lee Jong Baek , Park Jun Young
Published: March 2009

The microstructure and the mechanical property of liquid phase sintered (LPS) SiC
materials with oxide secondary phases have been investigated. The strength variation of LPS-SiC
materials exposed at the elevated temperatures has been also examined. LPS-SiC materials were
sintered at the different temperatures using two types of Al2O3/Y2O3 compositional ratio. The
characterization of LPS-SiC materials was investigated by means of SEM with EDS, three point
bending test and indentation test. The LPS-SiC material with a density of about 3.2 Mg/m3
represented a flexural strength of about 800 MPa and a fracture toughness of about 9.0 MPa⋅√m.
Characterization of Delamination in Laminated Composites Based on Damage Indices
Authors: Kim Heung Soo , Kim Jae Hwan , Choi Seung Bok
Published: March 2009

A modal strain based damage index is proposed to investigate the damage effects of discrete delaminations in a laminated composite structure. The Fermi-Dirac distribution function is incorporated with an improved layerwise laminate theory to model smooth transition of the displacement and the strain fields at the delaminated interfaces. Modal analysis is conducted to investigate dynamic effects of delamination in a laminated structure and to obtain modal strains. The damage index is calculated based on fundamental modal strains of laminated structures. The damage effects of laminated structures are investigated using arbitrary size, number, location and boundary conditions of discrete delaminations.
Detectability of Bearing Failure of Composite Bolted Joints by Electric Resistance Change Method
Authors: Shimamura Yoshinobu , Oda Keiko , Todoroki Akira , Ueda Masahito
Published: March 2009

Bolted joints are widely used for composite structures. As is well known, excessive bearing load gives rise to bearing failure at hole boundaries. Detecting bearing failure is important for assuring integrity of composite structures. Since conventional nondestructive inspection methods are expensive, cumbersome, time-consuming, and not suitable for health monitoring, a simple, low-cost inspection method for bearing failure must be developed. Authors have demonstrated the feasibility of detecting bearing failure by using an electric resistance change method. In this study, more detailed analyses were carried out to investigate the detectability in terms of the damage size and the distance between damage and electrodes. The results show that bearing failure of less than 10mm square causes the electric resistance change of a few hundred ppm and thus can be easily detected, and that the electrodes can be mounted more than 10 mm far from a bolt hole.
Finite Element Fracture Mechanics Study of Pre-Northridge Connections
Authors: Liu Hong Bo , Zhai Chang Hai , Shao Yong Song , Xie Li Li
Published: March 2009

The objective was to quantify the variation of stress intensity factor to weld root flaw sizes
in steel frame connections. Finite-element analyses were used to study fracture toughness in welded
beam-column connections. Investigations of fracture behavior mainly focused on the standard
pre-Northridge connection geometry. Finite element analysis was performed using the ANSYS
computer program. Stress intensity factor was calculated through a J-integral approach. Results show
that stress intensity factor is not uniform and is largest in the middle of beam flange. Stress intensity
factor increases nearly linear with the increase of flaw size. Backing bars have little effect on weld
fractures.
Evaluation of Fatigue Strength Improvement of Ship Structural Details by Weld Toe Grinding
Authors: Kim Myung Hyun , Kang Sung Won , Lee Jae Myung , Kim Wha Soo
Published: March 2009

In order to strengthen or repair the welded structural members or fatigue damaged areas,
various surface treatment methods such as grinding, shot peening and/or hammer peening are
commonly employed among other methods available. While the weld toe grinding method is known
to give 3~4 times of fatigue strength improvement, this improvement may significantly vary
according to weld bead shapes and loading modes. In this context, a series of fatigue tests is carried
out for three types of test specimens that are typically found in ship structures. Weld burr grinding is
carried out using an electric grinder in order to remove surface defects and improve weld bead
profiles. The test results are compared with the same type of test specimen without applying the
fatigue improvement technique in order to obtain a quantitative measure of the fatigue strength
improvement. Moreover, structural stress method is employed to evaluate the effectiveness of the
method in evaluating the fatigue strength improvement of welded structures.
Fractography and Crack Initiation of Very-High-Cycle Fatigue for a High Carbon Low Alloy Steel
Authors: Zhou Cheng En , Qian Gui An , Hong You Shi
Published: March 2009

Very-High-Cycle Fatigue (VHCF) is the phenomenon of fatigue damage and failure of
metallic materials or structures subjected to 108 cycles of fatigue loading and beyond. This paper
attempts to investigate the VHCF behavior and mechanism of a high strength low alloy steel (main
composition: C-1% and Cr-1.5%; quenched at 1108K and tempered at 453K). The fractography of
fatigue failure was observed by optical microscopy and scanning electron microscopy. The
observations reveal that, for the number of cycles to fatigue failure between 106 and 4×108 cycles,
fatigue cracks almost initiated in the interior of specimen and originated at non-metallic inclusions.
An “optical dark area” (ODA) around initiation site is observed when fatigue initiation from
interior. ODA size increases with the decrease of fatigue stress, and becomes more roundness.
Fracture mechanics analysis gives the stress intensity factor of ODA, which is nearly equivalent to
the corresponding fatigue threshold of the test material. The results indicate that the fatigue life of
specimens with crack origin at the interior of specimen is longer than that with crack origin at
specimen surface. The experimental results and the fatigue mechanism were further analyzed in
terms of fracture mechanics and fracture physics, suggesting that the primary propagation of fatigue
crack within the fish-eye local region is the main characteristics of VHCF.
Finite Element Analysis of Contact Stress for Particle Reinforced Composites
Authors: Cho Young Tae , Lee Choong Ho , Im Kwang Hee , Hwang In Nam
Published: March 2009

General structures or machines are firmly connected by bolts so that they have many
contact surfaces. Between these contact surfaces, there is a movement that vibrates with tiny
amplitude, which causes friction, leading to fretting damage. This damage causes a remarkable
reduction in the fatigue strength of the structures sub-materials, leading to remarkable fall-down of
life span of machines and structures. The particle reinforced composites under research in the
aerospace and automobile industries, theoretical analysis and research on fretting fatigue involved
with contact are needed, but there are few domestic studies. Therefore, this study is to identify
cracking damage, its initiation, growth direction and location by considering the strength load and
contact (surface/surface) in particle reinforced composites. So it performed a study on ellipsoidal
particle reinforced composites that have contact force under tensile load. This study performed a
theoretical analysis and a fretting test to identify damage mechanism to industrial structures as well as
aerospace and automobile industries according to expanded coverage of application and development
of the composites.
Strain Measurement in the Depth of the Order of Millimeter Using High Energy White X-Rays
Authors: Hirata Tomoyuki , Shibano Junichi , Shobu Takahisa , Suzuki Kenji , Kaneko Hiroshi , Kobayashi Michiaki
Published: March 2009

The strain in the bulk of material was evaluated using high energy white X-rays from a
synchrotron radiation source of SPring-8 in Japan. An austenitic stainless steel (JIS-SUS304L) was
used for a specimen. The specimen of 5 mm thickness was subjected to the bending. The internal strain
of it could be measured using white X-rays which range of energy from 60 keV to 125 keV. The
measurement of the internal strain with a high accuracy was accomplished using the strain data from
several lattice planes of γ-Fe simultaneously. Furthermore, the measurement error of strain could be
decreased by using the diffracted beam with high energy, high peak count and the similar profile with
the Gaussian distribution. The results showed that the high energy white X-rays is effective for the
internal strain measurement in the depth of the order of millimeter.
Effects of Water Jet Peening on Fatigue Properties of SPA-H and SPCC Steel
Authors: Jia Wei Ping , Ju Dong Ying , Shimamoto Akira
Published: March 2009

An experimental study of high pressure water jet peening treatment on SPA-H and SPCC
steel was conducted to study the effects of cavitation impacts of high-speed water on fatigue crack
initiation and propagation of notched specimens. Pull-pull fatigue tests’ condition was 350 MPa
maximum stress amplitude, 0.1 stress ratio and 10Hz frequency, while in-situ observation by SEM
was employed. It was found that fatigue life of water jet peening treated SPA-H specimens has been
obviously elongated by comparison with specimens without this treatment. However, for SPCC
steel specimens, by comparison with those without water jet peening treatment, fatigue life was a
little elongated, almost the same and obviously shortened corresponding to water jet peening
treatment time of 5, 10 and 15 minute, respectively. High pressure water jet caused surface
corrosion for SPCC low carbon steel, while with almost the same carbon content, copper, chromium
and nickel elements increased anti-corrosion properties of SPA-H steel. These resulted in the
different fatigue life of SPA-H and SPCC steel. In-situ observation on the crack tips approved above
analysis.
Contact-Driven Crack Formation in Dental Ceramic Materials
Authors: Li Wei , Li Qing , Loughran Jeffery , Swain Michael , Ichim Ionut , Fujisawa Naoki
Published: March 2009

Natural human tooth consists of multiple layered quasi-brittle biomaterials, which make
dental restorations experience a complex stress state under masticatory contact loading. As such,
many restorations are prone to failure and a constant effort is made to improve the mechanical
characteristics of the restorative materials. Clinical observations have shown that improved
strengths and fracture toughness in ceramic materials do not necessarily lead to an anticipated
higher functional longevity of the restoration. While substantial experimental investigations have
been carried out to identify the contact induced fracture in such multi-layer material systems,
numerical modelling of this event was largely unexplored. This paper presents a new numerical
method to account for micro-damage driven fracture in various multi-layered biomaterial structures.
In this study, a Rankine constitutive model is adopted and the crack initiation and propagation are
automatically implemented in an explicit finite element (FE) framework. The effects of indenter
radius, surface curvature and thickness of layered biomaterials on the cracking patterns are
investigated. The results show good agreement with the experimental studies in literature.
Isotropic Damage Analysis of Elastic Solids Using Meshless BEM
Authors: Gao Xiao Wei , Zhang Chuan Zeng
Published: March 2009

In this paper, an isotropic elastic damage analysis is presented by using a meshless boundary element method (BEM) without internal cells. First, nonlinear boundary-domain integral equations are derived by using the fundamental solutions for undamaged, homogeneous, isotropic and linear elastic solids and the concept of normalized displacements, which results in boundary-domain integral equations without an involvement of the displacement gradients in the domain-integral. Then, the arising domain-integral due to the damage effects is converted into a boundary integral by approximating the normalized displacements in the domain-integral by a series of prescribed radial basis functions (RBF) and using the radial integration method (RIM). The damage variable used in the paper is the ratio of the damaged area to the total area of the material, and an exponential evolution equation for the damage variable is adopted. A numerical example is given to demonstrate the efficiency of the present meshless BEM.
A Study of Damage in Aluminum Dual-Wall Structure by Hypervelocity Impact of AL-Spheres
Authors: Guan Gong Shun , Pang Bao Jun , Chi Run Qiang , Zhu Yao
Published: March 2009

In order to simulate and study the hypervelocity impact of space debris on dual-wall structure
of spacecrafts, firstly a non-powder two-stage light gas gun was used to launch AL-sphere projectiles.
Damage modes in rear wall of dual-wall structure were obtained, and while the law of damage in rear
wall depends on projectile diameter and impact velocity were proposed. Finally, numerical
simulation method was used to study the law of damage in rear wall. By experiment and numerical
simulation of hypervelocity impact on the dual-wall structure by Al-spheres, and it is found that
AUTODYN-2D SPH is an effective method of predicting damage in rear wall from hypervelocity
impact. By numerical simulation of projectile diameter, projectile velocity and the space between
bumper and back wall effect on damage in rear wall by hypervelocity impact, and fitting curves with
simulation results, the law of damage in rear wall and dominant factors effect damage in rear wall by
hypervelocity impact were proposed.
Cumulative Damage-Based Stiffness Reliability Analysis of the Stochastic Structural System
Authors: Yan Xin Chi , Zhao Wei Tao
Published: March 2009

Based on the understanding of passive impact of crack induced by fatigue load on
ultimate stress and the relation of material strength and elastic modulus, the paper gives expression
of residual elastic modulus with the form of cumulative damage and analyzes its digital character.
The reliability index is calculated by using advanced first order second moment reliability method
and the stochastic finite element method because the structures are stochastic, the significant failure
modes are identified by using the advanced branch and bound method, and the reliability of
structural system is evaluated by PNET method. A numerical example is indicated that the fatigue
reliability index of structural system can fulfils the demand of fatigue reliability in the design life,
but the stiffness reliability index of structural system descends with the increase of the service life,
and the stiffness reliability index can not fulfils the demand of the design when life over one third of
the whole service life, it shows that the cumulative damage influence to structural stiffness
reliability analysis can’t be ignored.
The Analysis of Fracture and Damage Mechanics on the Wellbore Stability
Authors: Wang Yong , Tang Li Qiang , Yang Yong
Published: March 2009

In this paper, the conception of natural fracture stress in rocks is given according to mesomechanics analysis. The quantitative analysis about wellbore collapse and stratum fracture is made and the density range of drilling fluid is determined. The result is the same as the conclusion which was given by the traditional Mohr-Coulomb criterion in petroleum engineering. The new method of combining mesomechanics with fracture mechanics is used to study the wellbore stability in petroleum engineering, which can reveal the nature of the rock deformation mechanism and provide theoretical reference to design of the drilling engineering.
Fatigue Damage Analysis on Crack Growth and Fatigue Life of Welded Bridge Members with Initial Crack
Authors: Zhou Tai Quan , Chan Tommy Hung Tin , Hua Yuan
Published: March 2009

The behavior of crack growth with a view to fatigue damage accumulation on the tip of
cracks is discussed. Fatigue life of welded components with initial crack in bridges under traffic
loading is investigated. The study is presented in two parts. Firstly, a new model of fatigue crack
growth for welded bridge member under traffic loading is presented. And the calculate method of
the stress intensity factor necessary for evaluation of the fatigue life of welded bridge members with
cracks is discussed. Based on the concept of continuum damage accumulated on the tip of fatigue
cracks, the fatigue damage law suitable for steel bridge member under traffic loading is modified to
consider the crack growth. The proposed fatigue crack growth can describe the relationship between
the cracking count rate and the effective stress intensity factor. The proposed fatigue crack growth
model is then applied to calculate the crack growth and the fatigue life of two types of welded
components with fatigue experimental results. The stress intensity factors are modified by the factor
of geometric shape for the welded components in order to reflect the influence of the welding type
and geometry on the stress intensity factor. The calculated and measured fatigue lives are generally
in good agreement, at some of the initial conditions of cracking, for a welded component widely
used in steel bridges.
Prediction of Cleavage Fracture in the Ductile-to-Brittle Transition Region of Pressure Vessel Steels: A Probabilistic Model
Authors: Gao Xiao Sheng , Zhang Gui Hua , Srivatsan T.S.
Published: March 2009

This paper presents a modified Weibull stress model, which accounts for the effects of
plastic strain and stress triaxiality at the crack tip region. The proposed model is applied to predict
cleavage fracture in a modified A508 pressure vessel steel. It is demonstrated that the Weibull
modulus (m) remains constant in the temperature range considered, while the threshold Weibull
stress (σw-min) decreases with an increase in temperature due to reduction of the yield stress and the
scale parameter of the Weibull model (σu) increases with temperature reflecting the influences of
temperature on both material flow properties and toughness. The proposed model accurately
predicts the scatter of the measured fracture toughness data and the strong effects of constraint and
temperature on cleavage fracture toughness.
The Prediction of Fatigue Crack Opening Behavior Using Cyclic Crack Tip Opening Displacement by Finite Element Analysis
Authors: Choi Hyeon Chang
Published: March 2009

An elastic-plastic finite element analysis (FEA) is performed to examine the opening behavior of fatigue crack, where the contact elements are used in the mesh of the crack tip area. The relationship between fatigue crack opening behavior and cyclic crack tip opening displacement was studied in the previous study. In this paper, we investigate the effect of the element size when predict fatigue crack opening behavior using the cyclic crack tip opening displacement obtained from FEA. The cyclic crack tip opening displacement is well related to fatigue crack opening behavior.
Digital Image Based Simulation on Failure Process of Heterogeneous Brittle Materials
Authors: Zhu Wan Cheng , Duan Jin Chao , Tang Chun An , Wang Shan Yong
Published: March 2009

Rock and concrete are typical heterogeneous material that the meso-scale heterogeneity may have a significant effect on their macro-scale mechanical responses. In this work, a digital image-based (DIB) technique is employed to characterize and quantify the heterogeneity of concrete, and the obtained data is directly imported into a numerical code named RFPA (Rock Failure Process Analysis) to study the effect of heterogeneity on the failure process of concrete. The upgraded RFPA is capable to simulate the progressive failure of brittle materials such as rock and concrete, representing both the growth of existing fractures and the formation of new fractures, obviating the need to identify crack tips and their interaction explicitly. The simulated results are in reasonable agreement with experimental measurements and phenomenological observations reported in previous studies.
On Damage Evaluation Method of the Ferromagnetic Material Based on Weak Magnetic Field Detection Technology
Authors: Yu Feng Yun , Zhang Chuan Xu , Wu Miao
Published: March 2009

The increase of magnetic field of ferromagnetic components under service load and
geomagnetic field is induced by the residual magnetic induction and spontaneous magnetization.
The stress concentration positions can be found by detecting the magnetic field and the fracture can
be avoided. The variation of the residual magnetic intensity of bearing carriers under different
damage conditions is studied in this paper; the statistical characteristic of the residual magnetic
intensity of the specimens in different residual deformations is got, and a concept of residual
magnetic intensity standard deviation is put forward with a lot of experiments and in-depth theoretic
analysis. The results indicate that the curves of residual magnetic intensity standard deviation
appear obvious turning points when the specimens reach the yield point in different original
magnetic field conditions, and that the function between residual magnetic intensities standard
deviation, tensile load and strain is established. Therefore, the plastic deformation can be judged by
the variation of the magnetic field in their service process, and the damage level can be evaluated
consequently, which gives a new reliable method to estimate the deformation of ferromagnetic
material.
Modeling and Simulation of Hydraulic Fracturing Propagation in Permeable Reservoirs
Authors: Lian Zhi Long , Wang Xiu Xi , Wu Heng An , Xue Bing , Zhang J. , Zhang Shi Cheng
Published: March 2009

Numerical simulation of hydraulic fracturing propagations in the permeable reservoirs was
carried out with the finite element analysis software (ABAQUS). A model of coupling the stress
equilibrium and fluid continuity equations was proposed and implemented. The nonuniform of sink
pore pressure on the fracture surfaces which changes associated with the propagation of fracture was
described by a self-developed subroutine through the FLOW in ABAQUS. Samples under different
conditions were conducted for studying the rules of the propagation of hydraulic fracturing. The
results show that the permeability at the fracture tip is more serious than any other places of the
fracture face. The model also illustrates that the fracture geometry is mainly determined by the
minimal in-situ stress. The model can be used to simulate the effects of hydraulic fracturing pressures
and injection rates on fracture propagation. The results are of much significance for the design of
hydraulic fracturing treatments.
Study of Three-Dimensional Stress Distribution and Damage Characterization of Bolt Composite Joint
Authors: Liu Yong Shou , Shao Xiao Jun , Yue Zhu Feng
Published: March 2009

A 3D finite element model of bolt composite joint has been established to determine the stress distribution on the contact surface. The effects of clamping torque and friction on the contact stress and interlaminar normal stress are considered. From the analysis results, contact stress is bared mainly by the 0° layer. The distribution and magnitude of contact stress are conducted by friction. The effect of clamping torque on interlaminar normal stress is very strong. A 3D damage user subroutine is added to the FEM to simulate the damage of joint. By the means of damage simulation, the initiation and progression direction of three types damage are predicted. Matrix cracking and fiber-matrix shear occur at first, and fiber buckling is founded subsequently. The matrix cracking and fiber-matrix debonding initiate at circumferential angle 45°and 135°, and fiber buckling initiate at the 0° layer on the bearing plane. The friction and bolt clamping torque can restrain damage initiation and development.
Bifurcation and Chaos of the Rectangular Moderate Thickness Cracked Plates on an Elastic Foundation
Authors: Xiao Yong Gang
Published: March 2009

Based on Reissner plate theory and using Hamilton variational principle, the nonlinear
equations of motion are derived for the moderate thickness rectangular plates with transverse
surface penetrating crack on an elastic foundation under the action of periodic load. The suitable
expressions of trial functions satisfied all boundary conditions and crack’s continuous conditions are
proposed. By using the Galerkin method and the Runge-Kutta integration method, the nonlinear
equations are solved. The possible bifurcation and chaos of the system are analyzed under the action
of external load. In numerical calculation, the influences of the different location and depth of crack
and external load on the bifurcation and chaos of the rectangular moderate thickness plates with
freely supported boundary are discussed.
Remaining Life Evaluation and Maintenance of Service-Exposed HP-Nb Reformer Tubes
Authors: Jiang Yong , Gong Jian Ming , Tu Shan Tung
Published: March 2009

This paper is aimed at investigating the damage and remaining life of a whole HP-Nb
hydrogen reformer tube serviced for 12 years. The damage and remaining life evaluation of
different parts of the tube were made using metallographic examination, ambient and high
temperature uniaxial tensile tests, creep rupture tests and damage mechanics analysis. The results
showed that different parts of the tube have the different damage and remaining life due to different
service temperature, higher the service temperature, severer the damage and shorter the remaining
life. Based on these research results, a case of local maintenance of the reformer tube was
introduced.
A Short Fatigue Crack Growth Law for 1Cr18Ni9Ti Weld Metal
Authors: Zhao Yong Xiang , Yang Bing , Zhang Wei Hua
Published: March 2009

A series of uniaxial-compression tests were conducted on some representative brittle rock specimens, such as granite, marble and dolerite. A multi-channel, high-speed AE signal acquiring and analyzing system was employed to acquire and record the characteristics of AE events and demonstrate the temporal and spatial distribution of these events during the rupture-brewing process. The test result showed that in the primary stage, many low amplitude AE events were developed rapidly and distributed randomly throughout the entire specimens. In the second stage, the number of AE increased much slower than that in the first stage, while the amplitude of most AE events became greater. Contrarily to the primary stage, AE events clustered in the middle area of the specimen and distributed vertically conformed to the orientation of compression. The most distinct characteristic of this stage was a vacant gap formed approximately in the central part of the specimen. In the last stage, the number of AE events increased sharply and their magnitude increased accordingly. The final failure location coincidently inhabited the aforementioned gap. The main conclusion is that most macrocracks are developed from the surrounding microcracks existed earlier and their positions occupy the earlier formed gaps, and the AE activity usually becomes quite acute before the main rupture occurs.
Evolution of Porous Structure and Fatigue Behavior of C/C Composites
Authors: Liao Xiao Ling , Xu Wen Feng , Li He Jun
Published: March 2009

Porous structure is an important component in C/C composites, which directly affects the fatigue behavior of materials. Therefore, it is necessary to discuss the evolution of porous structure in C/C composites under the fatigue loading. In present work, the character of porous structure in original C/C composites was summarized and the evolution of porous structure after fatigue loading was analyzed. The positive effect of the porous structure evolution after fatigue loading on the reinforcing behavior of fatigue was proposed as well, which could provide a basis for further studies on the fatigue mechanisms of C/C composites.