bluuebunny/crossref_metadata_2025 huggingface dataset:
The Detection and Imaging of Internal Defect Using ESPI-Based Strain Analysis
Authors: Lee Tae Hun , Jhang Kyung Young
Published: March 2009

Optical NDE (Nondestructive Evaluation) techniques such as ESPI (Electronic Speckle Pattern Interferometer) and shearography that are non-contact and real-time method are used to detect the defects in material. However, ESPI measurement is affected by disturbance such as rigid body motion, and has difficulty in recognizing the real shape and size of the defect. Shearography also involves several problems like it needs several operator-dependent factors including the amount of shearing and shearing direction for the quantitative analysis of internal defect, and it does not show the exact shape of the defect. In order to overcome these problems and evaluate the internal defect quantitatively in this study, the imaging of the inner defect based on the ESPI technique is proposed. In this method, the external perturbative load such as thermal load is induced to the specimen, and the deformation distribution of the specimen is measured by ESPI. Then the distribution of the shear strain energy is obtained by the strain analysis of the ESPI measurement result. On the edge of the defect, the shear strain energy is concentrated, so we can obtain the outline of the internal defect by following the peak point of the shear strain energy distribution. This method makes it possible to evaluate the size and shape of the defect quantitatively without operator-dependent factors.
Matrix Crack Detection of CFRP Laminates in Cryogenic Temperature Using Electrical Resistance Change Method
Authors: Todoroki Akira , Omagari Kazuomi , Ueda Masahito
Published: March 2009

For a cryogenic fuel tank of a next generation rocket, a Carbon Fiber Reinforced Plastic (CFRP) laminated composite tank is one of the key technologies. For the fuel tank made from the laminated composites, matrix cracks are significant problems that cause leak of the fuel. In the present paper, electrical resistance change method is adopted to monitor the matrix cracking of the CFRP laminate. Previous studies show that tension load in fiber direction causes electrical resistance increase due to the piezoresistivity of the carbon fibers, and fiber breakages also cause the electrical resistance increase of the CFRP laminates. In order to distinguish the electrical resistance changes due to matrix cracking from those due to the piezoresistivity and the fiber breakages, residual electrical resistance change under the complete unloading condition is employed in the present study. Experimental investigations were performed using cross-ply laminates in cryogenic temperature. As a result, it can be revealed that the residual electrical resistance change is a useful indicator for matrix crack monitoring of the cross-ply CFRP laminates.
An Optical Method for the Detection of In-Plane Motion of Acoustic Waves Propagating in Solids
Authors: Yang Che Hua , Tsai Yua Ching
Published: March 2009

A new interference-based optical technique called in-plane displacement interferometer
(IPDI) is introduced for the detection of in-plane (IP) motion of ultrasonic waves. The IPDI
employs a tiny square indentation of about 30 microns in width on the sample surface and a
relatively simple optical arrangement for the detection of IP motion of ultrasonics waves. With the
IPDI, measurement of IP motions of Lamb waves propagating along a thin brass foil is
demonstrated. Dispersion relations for the S0 mode dominated by in-plane motion in the low fd
(frequency times thickness) regime is obtained with the IPDI.
3D Motion Analysis on the Hallux Valgus by Using the Multi-Segment Foot Model
Authors: Hwang Sung Jae , Choi Hue Seok , Lee Kyung Tae , Kim Young Ho
Published: March 2009

The purpose of this study is to quantitatively evaluate foot motions in the normal and hallux
valgus(HV) patients using a proposed multi-segment foot model. Results showed that HV patients
exhibited relatively smaller flexion/extension, especially in terminal stance. An early abduction at the
ankle during terminal stance was also noted in HV patients, which resulted in an excessive abduction
in subtalar joint. In HV patients, medial MP joints exhibited excessive amount of adduction during
terminal stance. In HV patients, hallux MP joint and talocrural joint exhibited excessive external
rotation over the whole period of gait cycle. Understanding the detailed foot motions by the present
multi-segment foot model would be very useful to diagnose and to treat patients with various foot
diseases.
Residual Stress and Damage Evolution in TBCs by Optical Method
Authors: Wang Feng Hui , Zhang Yong , Wang Hong
Published: March 2009

In recently years, ruby fluorescence spectroscopy has been demonstrated as a powerful technique for monitoring residual stress evolution in the thermally grown oxide scale in thermal barrier coatings(TBC) systems. The measured residual stresses, in turn can be used to monitor evolution of damage in the coatings. Effective use of this technology for real time damage monitoring require the identification of strength in measured stresses that can be used as indicators of damage evolution.the present work focuses on studying the evolution of residual stresses in TBC systems during oxidation. The coating are atmospheric plasma sprayed (APS), the residual stress were measured at different oxidation time and to identify critical features so as to be used as indicators of failure in TBCs.
A Numerical Study on Thermal Strain Control of Aluminum Alloy Mold for Tire Manufacturing
Authors: Oh Yool Kwon , Yang Ho Dong , Kim Yong Bum
Published: March 2009

In the present study, numerical work applying a finite element method (FEM) is used to
analyze the characteristics of aluminum (Al) alloy mold for thermal strain control. In the concrete, the
temperature distribution on the inside of Al alloy mold, the contraction rate and stress occurred by
temperature variations are investigated to predict the accurate measurement variation of Al alloy mold
during the cooling process. In addition, the numerical result of the Al alloy mold were compared with
those of mild steel mold in order to obtain the improvement and good quality of mold. In the end, the
numerical results such as temperature distributions, contraction rate and stress are presented to help to
make the effective and the best mold products. Besides, the introduced technique of numerical
analysis applying a FEM is very useful and important things in the fracture and damage mechanics,
especially needs the accuracy improvement such as Al alloy mold products.
Initial Damage Detection Based on Elastic Modulus Randomness
Authors: Liu Fu Shun , Li Hua Jun , Yu Guang Ming , Liu Yan Chun , Wang Wei Ying
Published: March 2009

A damage detection method reflecting initial damage of the elastic structure is presented.
It is based on the idea that the damage will decrease the structure stiffness. From eigenvalue issue,
regard Poison ratio and elastic modulus as a constant and a random variable, respectively, and in
terms of known data and a combination of the FEM, then equations solving random modulus of the
undamaged and the damaged structure are obtained, respectively. Based on the element damage
indicator, initial damage of the structure can be detected. At last, a five-storey shearing structure is
simulated, and the results indicate that initial damage situation can be accurately calculated, and
initial damage locations can be estimated based on the proposed method, which is simple and
effective, and contributes to the application in Engineering.
Application of Non-Linear Notch Mechanics to Biaxial Stress Problems
Authors: Teranishi T. , Nisitani Hironobu , Ushijima Kuniharu
Published: March 2009

In this study, it was made clear that the non-linear notch mechanics is useful not only in
the case of uniaxial tension but also in the case of biaxial tension. The difference of both cases is as
follows. In the former the plastic strain field near a notch root is determined by εp
y0,FEM (plastic
strain at a notch root) and ρ (notch root radius) alone, but in the latter case it is determined by
εp
y0,FEM, ρ and stress ratio k=σxn/σyn.
Stress Intensity Factor in Alumina-Zirconia Composites by a Hybrid Finite Element Method
Authors: Alfano Marco , Furgiule F. , Maletta Carmine
Published: March 2009

The present paper describes a numerical method which is able to calculate the stress
intensity factor in two dimensional heterogeneous materials under mechanical and thermal loads.
The proposed method uses two hybrid element formulations to model the second phase
heterogeneities of the material and the crack tips. The method was used to analyse alumina-zirconia
ceramic materials, and the effects due to the zirconia t→m phase transformation and the thermal
stresses, which develop during the cooling stage of sintering, were taken into account in calculating
the stress intensity factor.
The Effect of Compressive Residual Stress on the Fatigue Characteristics of Al6061
Authors: Park Won Jo , Huh Sun Chul , Lee Kang Young , Park Sung Ho , Hwang Hwa Sik
Published: March 2009

Recently, the steel parts used at the aerospace and automobile industries are required to be
used high stress more than ever before in need of the weight down. Therefore, used material steel have
to be a high stress, which is an indispensable condition in this field. At the consideration of parts
design, high hardness of the lightweight parts has an benefit of saving fuel and material. In this study,
the surface conditions are measured to know the influence on fatigue properties by shot peening. In
this study, the optimum shot peening condition is investigated. Fatigue test was accomplished to
investigate the effects of compressive residual stress by shot peening on fatigue characteristics. Test
results show the fatigue characteristics were increased by optimum peening condition. But the fatigue
characteristics were decreased by under peening or over peening condition.
Effective Material Properties of Damaged Elastic Solids
Authors: Lee Usik , Youn Deokki
Published: March 2009

By using a continuum modeling approach based on the equivalent elliptical crack
representation of a local damage and the strain energy equivalence principle, the effective elastic
compliances and the effective engineering constants are derived in closed forms in terms of the
virgin (undamaged) elastic properties and a scalar damage variable for damaged two- and threedimensional
isotropic solids. It is shown that the effective Young’s modulus in the direction normal
to the crack surfaces is always smaller than its intact value.
Thermal and Mechanical Effects on the Flexible Polymer Substrate
Authors: Tseng Ming Chun , Yu Hsin Her , Hwang Shug June , Lin Chien Chang , Lee Kuang Chyi
Published: March 2009

A novel flexible polymer was used for the new generation display panel, which was
prepared by thermal annealing treatments. Atomic force microscope (AFM) and visible
spectroscopy were employed to measure the surface roughness and the optical transparency of the
substrates. Mechanical cycles bending were carried on the flexible substrates in this study. Surface
morphology of the substrates after bending was observed by scanning electron microscope (SEM).
The performances of the OLED device were compared for the samples with and without cycles
bending.
Asymptotic Analysis of Boundary-Induced Size Dependence of Fracture Properties
Authors: Duan Kai , Hu Xiao Zhi
Published: March 2009

The recently-developed boundary effect concept and associated asymptotic model are used to explain the size effect phenomena in fracture of quasi-brittle materials. It is demonstrated that the size dependence of the fracture toughness and strength of quasi-brittle materials is indeed due to the influences of specimen boundaries on the failure mode and therefore, on the strength of the specimen. To verify the boundary effect concept, fracture tests on a high strength concrete reported by Karihaloo et al are analysed and predicted using the asymptotic model. The results show that the predictions of the asymptotic boundary effect model agree very well with those experimental results.
An Overview of the Surveillance Measurements Made to Support the Integrity of Magnox Steel Reactor Pressure Vessels
Authors: Moskovic Robert , Wootton M.R. , Flewitt Peter E.J.
Published: March 2009

As part of the requirement to demonstrate safe operation of the steel reactor pressure vessels for the UK Magnox fleet, surveillance samples were installed at the time of construction. These were representative of the steels and weld metals used for the manufacture of the vessels. The history of sample removal and mechanical property testing is briefly reviewed. The factors leading to changes in the fracture resistance and tensile properties will be discussed. The link is described between the mechanisms leading to changes in mechanical properties and the statistically based approach adopted to predict values of fracture toughness for the neutron dose and temperatures at key vessel locations. Predictions are compared with test results obtained from samples removed from a decommissioned reactor and also surveillance and accelerated radiation samples removed towards the end of reactor life.
A Bi-Material Wedge – a Model for the Prediction of Failure Initiation at Shape and Material Discontinuities
Authors: Klusák Jan , Knésl Zdeněk
Published: March 2009

Geometrical and material discontinuities in constructions lead to singular stress
concentrations and consequently to a crack initiation. The model of a bi-material wedge makes it
possible to analyse such construction points to assess their stability. The presented approach is
based on the knowledge of the strain energy density factor distribution in the concentrator vicinity.
Analysis of Premature Rip-Off Failure Mechanism of Reinforced Concrete Beams Strengthened with FRPs
Authors: Park Cheol Woo , Sim Jong Sung , Park Sung Jae
Published: March 2009

Various types and forms of FRP materials have been applied for structural strengthening
of reinforced concrete (RC) beams. When CFRP plates are used, however, a premature failure used
to occur before strengthening effect appears adequately. This is primarily due to the rip-off of CFRP
plate attached on RC beams. Despite of numerous studies on the rip-off failure of externally
strengthened RC beams, the failure mechanism is not clearly explained yet. Investigations from the
literatures have shown that the rip-off failure is dependant on vertical and shear stresses at the level
of main reinforcements in RC beams. This study suggests an analytical model to investigate the ripoff
failure load based on the stresses at the level of main reinforcements. The proposed model is
relatively simple and produces very comparable results to the test data. Therefore, it is anticipated
that the proposed model can be successfully used to provide further information on the rip-off
failure mechanisms and its prevention.
Interfacial Fracture Toughness of Adhesively Bonded Joints
Authors: Alfano Marco , Furgiuele Franco , Maletta Carmine
Published: March 2009

The aim of the present paper is to evaluate the interfacial fracture toughness of an Al/Epoxy adhesive system with a crack lying at the interface. A cracked lap shear specimen loaded in four point bending is adopted and the fracture toughness is pointed out in terms of the critical complex stress intensity factor. To this aim numerical analyses of the fracture specimen have been carried out using a commercial finite element code. In addition, fracture surfaces are analyzed and the locus of failure is discussed.
Crack Identification by Jointly Time-Frequency Analysis
Authors: Feng Xin , Zhou Jing
Published: March 2009

A novel approach for crack identification based on jointly time-frequency analysis is
presented in the paper. A bilinear stiffness model for the breathing crack was introduced to
represent the nonlinear dynamics of a cracked beam. The nonlinearity of the dynamic responses due
to the crack opening-closing is used to identify the occurrence of the crack. The Wigner-Wille
distribution technique is applied to analyze the response signals and the instantaneous frequency is
extracted as damage-sensitive feature. The numerical simulations of a breathing crack model were
carried out to validate the possibility and effectiveness of the proposed approach. The effects of
crack severity and sampling frequency on crack identification were also studied in the simulations
respectively. The results show that the proposed method can effectively identify the crack with
slight severity without any baseline model or data, and the better the identification obtains as the
larger the sampling frequency. The study demonstrates that the proposed approach by using of
jointly time-frequency analysis is a promising technique for crack identification.
Structural Damage Identification Using Wavelet Packet Analysis and Neural Network
Authors: Fei Qing Guo , Li Ai Qun , Miao Chang Qing , Li Zhi Jun
Published: March 2009

This paper describes a study on damage identification using wavelet packet analysis and
neural networks. The identification procedure could be divided into three steps. First, structure
responses are decomposed into wavelet packet components. Then, the component energies are used
to define damage feature and to train neural network models. Finally, in combination with the feature
of the damaged structure response, the trained models are employed to determine the occurrence, the
location and the qualification of the damage. The emphasis of this study is put on multi-damage case.
Relevant issues are studied in detail especially the selection of training samples for multi-damage
identification oriented neural network training. A frame model is utilized in the simulation cases to
study the sampling techniques and the multi-damage identification. Uniform design is determined to
be the most suitable sampling technique through simulation results. Identifications of multi-damage
cases of the frame including different levels of damage at various locations are investigated. The
results show that damages are successfully identified in all cases.
Experimental Studies of Through-Wafer Copper Interconnect in Wafer Level MEMS Packaging
Authors: Choa Sung Hoon
Published: March 2009

In this paper, mechanical reliability issues of copper through-wafer interconnection are
investigated numerically and experimentally. Several factors which could induce via hole cracking
failure are investigated such as thermal expansion mismatch, via etch profile, copper diffusion
phenomenon, and cleaning process. Improvement methods are also suggested.
Plane Electromechanical Fieldes in a Piezoelectric Material with a Crack
Authors: Liu Shu Hong , Wu Meng , Duan Shu Min , Wang Hong Jun
Published: March 2009

A two-dimensional electromechanical analysis is performed on a transversely isotropic
piezoelectric material containing a crack based on the impermeable electric boundary condition. By
introducing stress function, a general solution is provided in terms of triangle series. It is shown that
the stress and electric displacement are all of 1/2 order singularity in front of the crack tip. In
addition, the electromechanical fields in the vicinity of the crack when subjected to uniform tensile
mechanical load are obtained using boundary collocation method.
Mode III Yoffe Dynamic Crack in an Infinite Length Strip for Orthotropic Anisotropy Functionally Graded Material
Authors: Jin Cheng , Li Xin Gang , Lü Nian Chun
Published: March 2009

A moving crack in an infinite strip of orthotropic anisotropy functionally graded material (FGM) with free boundary subjected to anti-plane shear loading is considered. The shear moduli in two directions of FGM are assumed to be of exponential form. The dynamic stress intensity factor is obtained by utilizing integral transforms and dual-integral equations. The numerical results show the relationships among the dynamic stress intensity factor and crack velocity, the height of the strip, gradient parameters and nonhomogeneous coefficients.
Vibration Analysis of Non-Uniform Beams with an Arbitrary Number of Cracks
Authors: Yu Zhi Gang , Chu Fu Lei , Cheng Yue
Published: March 2009

In this paper, a method is presented to facilitate the computation of dynamic properties of
non-uniform beams with any number of cracks. Based on the Frobenius method, an analytical
solution of vibration equation of non-uniform beams is obtained. In combination with the line
spring model of crack, the transfer matrices for non-uniform beam element and crack are
established respectively. Then the global transfer matrix can be simply formulated, from which the
frequency equation in the form of 2×2 determinant is derived. Due to the decrease in the
determinant order as compared with previously developed procedures, significant savings in the
computational task would be achieved by the present method.
Fracture Behaviour and Temper Embrittlement Induced by NGS of Phosphorus
Authors: Li Qing Fen , Li Li , Zhou Hui Min
Published: March 2009

The non-equilibrium grain-boundary segregation (NGS) isotherms and its kinetics serve
to provide a more complete understanding of inter-granular segregation behavior in relation to
mechanical properties, not only for the engineering steels but also for a wide range of structural
alloys. The NGS of phosphorus and temper embrittlement dynamics on the same heat treatment
condition at the same isothermal holding time in two Cr-Mo steels, 12Cr1MoV and 2.25Cr1Mo,
was experimentally studied. The fracture behaviour was also observed by tensile tests in situ in a
scanning electron microscope (SEM). Results show that both the concentration of phosphorus
atoms in grain boundaries and the degree of embrittlement reaches a maximum at the critical time.
It can be satisfactorily elucidated by the temper embrittlement mechanism of NGS caused by
cooling from solution temperature to isothermal holding temperature.
A Theoretical Model for Nondestructive Evaluation of Damage of Adhesive Joints
Authors: Shui Guo Shuang , Wang Yue Sheng , Qu Jian Min
Published: March 2009

In this paper, a new theoretical model is developed to characterize the damage of the
adhesive joint. Elastic modulus of adhesive joints is an important parameter to represent damage
characteristics. Based on the fact that the thickness of the adhesive layer is very small, it is
reasonable to believe that damage will decrease the tension modulus of the adhesive joint while the
compression modulus will keep unchanged. Modeling the adhesive joint as an interface with
different modulus in tension and compression, and applying integral transform method, we solve the
associated nonlinear boundary problem to obtain the nonlinear ultrasonic waves transmitting through
the adhesive layer. With this nonlinear ultrasonic wave, variation of elastic modulus and damage
variable of the adhesive layer are thereafter characterized nondestructively by a nonlinear
coefficient.
Study on Characteristics of Damage Mechanics of Ductile Iron
Authors: Jiang Zhi Qiang , Feng Xi Lan , Shi Jin Fa
Published: March 2009

The damage characteristics of ferrite ductile cast-iron under uniaxial stress has been
studied through measuring electric resistance. The results showed that the damage in ductile cast-iron
happens when the applied stress is more than a certain extent, and the damage value increases with
stress. The evolutional law of damage value as a function of stress was obtained. The damage
threshold of ductile cast-iron exists and increases with nodularity, but this threshold is always below
the yield strength, which has related significant reference to the design of machinery structure and the
choice of materials. The critical damage value is not related to the nodularity, which is about
0.06~0.068 under the present test condition.
Experimental Investigation of Typical Environmental Corrosion Influence on Fatigue Life in 2024-T3 Aluminium Alloy
Authors: Bao Rui , Zhang Jian Yu , Fei Bin Jun
Published: March 2009

The influence of environmental corrosion on fatigue life of 2024-T3 aluminum alloy is
investigated in this paper. Experiments with center-hole specimens and CC(T) specimens are
conducted and reported. The test result shows that the corrosion influence is becoming serious
while the environmental causticity is increasing, and the influence on crack initiation life is greater
than that on crack propagation life. Analysis of the test data also indicates that the environmental
causticity enlarges the dispersivity of fatigue life. Using the corrosion-modification-factor obtained
by eigenvalue or mean value to prediction the fatigue life with high reliability will cause an
unconservative conclusion.
Contact Damage and Damage Tolerance of Dental Ceramics
Authors: Qiu Yan , Bao Yi Wang , Liu Yi Hong
Published: March 2009

Surface and subsurface contact damage in dental ceramics and the influence of microstructure on damage tolerance were investigated in this study through indentation methods. The dependence of the damage tolerance on common materials properties was discussed. A simple expression to estimate quantitatively the damage tolerance via basic material parameters, based on the features of damage tolerance and fracture mechanics is confirmed. And the residual strength of damaged specimen was measured via three-point bending tests.
Application of Fractional Spline Wavelet in Detection of Abrupt Information from Fault Gear System
Authors: Shen Yong Jun , Yang Shao Pu , Ma Bing Yu
Published: March 2009

In this paper the Fractional Spline Wavelet Transform (FrSWT) is introduced based on the definitions and properties of the fractional B-spline and the symmetric fractional B-spline. Then the computation process and approximation properties of the FrSWT are also discussed and especially, the truncation error of computation is obtained analytically. At last, the FrSWT is applied to detect the abrupt information in the simulated and measured signal of fault gear system.
Fatigue Reliability Evaluation of Old Steel Bridges Based on Probabilistic Fracture Mechanics
Authors: Wang Chun Sheng , Nie Jian Guo , Chen Ai Rong , Chen Wei Zhen , Xu Yue
Published: March 2009

There are many old steel bridges on Chinese transportation lines, which keep their normal
traffic service function. The old bridges are often required to carry an increasing volume of traffic and
heavier vehicles than the original design, so bridge management departments pay more attention to
the actual remaining fatigue life of such structures. Based on probabilistic fracture mechanics theory,
the member and the system fatigue failure evaluation models for old steel bridges are all proposed,
and the fatigue reliability analysis program is developed using Monte-Carlo. As a case study, the
evaluation models are used to predicate the fatigue reliability of Zhejiang Street Bridge. According to
evaluation results, the probabilistic remaining fatigue life, safe inspection intervals and maintenance
strategy are determined.
Characteristics of Low Temperature Brittle Fracture Surface of High Nitrogen Austenitic Steel
Authors: Liu Shi Cheng , Liu Shi Yong , Liu De Yi
Published: March 2009

Fracture surface and crack propagation in low temperature brittle fracture (LTBF) of an
18Cr-18Mn-0.7N high nitrogen austenitic steel (HNAS) were examined by means of scanning
electronic microscopy, and compared with behaviours of LTBF of low carbon steel. Similar to BCC
low carbon steel, the HNAS experienced a typical ductile-to-brittle transition (DBT) with decreasing
temperature, and the appearance of the fracture surface transited from fibrous to granular.
Dual-surface observation revealed that there were three types of fracture modes in LTBF of the
HNAS: annealing twin boundary fracture, intergranular fracture, and transgranular fracture. The
annealing twin boundary fracture facets were parallel to {111} planes, and were fairly flat and
smooth, with a pattern of three sets of parallel straight-lines intersecting at 60. There were also bent
steps that originated and terminated at grain boundaries. The transgranular fracture facets were coarse
and uneven, with uniformly distributed small pits and partially river pattern on them. The
intergranular fracture facets were smoothly curved ones on which more than three sets of parallel
deformation structure trace lines were observed. Careful observation on crack propagation
demonstrated that during LTBF of the HNAS, microcracks formed firstly at grain boundary and
annealing twin boundary, and then these microcracks came together and coalesced to induce crack
propagation through grains, resulting in a fracture appearance with shiny facets distributing in dull
facets.
Investigation on Creep Damage of Natural Gas Storage in Salt Rock Layer
Authors: Chen Feng , Yang Chun He , Zhang Chao , Bai Shi Wei
Published: March 2009

To research the creep behavior of salt rock, the uniaxial and triaxial creep experiments
were carried out under different deviatoric stresses and same confining pressure or different confining
pressures and same deviatoric stress. The experiment results showed that the analysis on the creep
damage of salt rock should consider the influence of confining pressure and deviatoric stress. By
introducing the damage variable to the Norton Power law of salt rock, a new constitutive law of salt
rock was presented. The damage equivalent stress was the function of the confining pressure and the
deviatoric stress in the new constitutive law. The constitutive law can embody the steady creep and
accelerative creep of salt rock, in which the parameters are obtained by simulating the experimental
data of salt rock in some salt mine. The theoretic results are in good agreement with the experimental
results.
The new constitutive law was embedded in the three dimension numerical codes. The natural gas
storage in the salt mine was analyzed by the new constitutive law. The evolvement law of damage
bound and the displacement law around the natural gas storage were studied under the minimal
natural gas storage pressure. The continuous operating time of the natural gas storage was also
analyzed under the pressure. The research conclusions are expected to be applied in the natural gas
storage projects in salt rock layer.
Analysis of Cracks and Stresses of Welded Attachments on Full-Scale Plate Girder under Fatigue Loading
Authors: Lee Myung Gu , Lee Seung Yong , Park Cheol Woo
Published: March 2009

In steel structure systems such as plate girder bridges and framed structures, fatigue
damage used to occur at welded areas rather than primary structural members. These damages and
behaviors of the welded attachments need to be extensively investigated so that the fatigue design
criterion can effectively control the fatigue damage of steel structure systems. This study utilized a
full-scale plate girder on which various welding attachments were mounted. The welded attachments
investigated herein included flange gussets, web gussets, vertical stiffeners, and cover plates. The
fatigue cracks initiated at the longitudinal end of joint area of the weld bead and the parent metal
where stress was significantly concentrated. The initiated fatigue cracks developed along the weld
path and then, propagated to the parent metal in the direction perpendicular to the principal stress.
The fatigue cracks developed even under a compressive stress when a significant residual stress was
experienced from the welding. The fatigue strengths of the each welded attachment were evaluated
and compared with the current fatigue design specifications in AASHTO [1] and JSSC [2].
Fracture Analysis and Mechanical Property of AZ91D Magnesium Alloy Chips Prepared by Solid State Recycling
Authors: Ji Ze Sheng , Hu Mao Liang , Chen Xiao Yu
Published: March 2009

AZ91D magnesium alloy is prepared by hot extrusion of recycled machined chips and its fractures and mechanical properties are investigated at various extrusion conditions. Cold-press is employed to prepare extrusion billets of AZ91D magnesium alloy chips, and then the billets are hot extruded at 573K-723K with an extrusion ratio of 11:1. The results show that tensile strength and elongation of the extrusion magnesium alloy with the extrusion temperature of 673K and the extrusion rate of 0.08mm/s can reach 380MPa and 6%, respectively. Fracture surface presents a mix mechanism of dimple-like fracture and gliding fracture. Due to grain refinement by cold-press and hot extrusion, mechanical properties of extruded rods are much higher than those of as-cast AZ91D magnesium alloy. Also, much lower energy consumption is necessary for this recycling compared to the conventional casting process. Solid state recycling is an efficient method for magnesium alloy chips recycling.
Plastic Zone Study by Means of Tri-Dimensional Finite Element Models on Fatigue Crack Closure
Authors: González-Herrera Antonio , Garcia-Manrique J. , Cordero A. , Zapatero Jose
Published: March 2009

This paper focuses on the study of the plastic zone in fatigue crack closure based on the
results obtained by means of 3D Finite Element Analysis (FEA). These results show the crack
behavior through the thickness. The plastic zone is visualized and quantified. It does not correspond
to the classical shape. The plastic zone in the interior surface is similar to those obtained in 2D plane
strain conditions and a reduced effect of closure is observed. However, close to the external surface,
2D plane stress results are not reproduced, the plastic zone size is smaller and an important change is
observed. This transition is developed in a thin external portion of the specimen and it can only be
captured if a fine mesh of the thickness is done.
A Constitutive Damage Model for Dynamic Response of Dry/Water-Saturated Granite with Application to Study on Stress Waves
Authors: Zhou Zhong , Wang Xiao Jun
Published: March 2009

A damage constitutive model of dry/water-saturated granite is proposed within the framework of continuum mechanics and mixture theory, and the model allows for the simulation of the effects of micro-cracks, micro-pores and saturated water. By implementing the model into wave propagation code, one dimensional stain waves in dry granite induced by a rectangular impulsive loading and spherical waves in water-saturated granite due to underground explosion are studied. The simulation results demonstrate the main features of the model, and it is shown that the theoretical model developed is valid for study on the characteristics of stress waves in rock medium.
Flexural Failure Analysis of Concrete Beams Reinforced with Newly Developed Deformed GFRP Bars
Authors: Sim Jong Sung , Park Cheol Woo , Ju Min Kwan
Published: March 2009

Traditional concrete structures with steel reinforcing bars shall gradually deteriorate owing to external loadings and environmental attacks. Fiber reinforced polymer (FRP) is one of the most attractive alternative material for steel since it provides excellent tensile strength and much higher corrosion resistance as well as lower self-weight. This study utilized a newly developed FRP rebar that uses glass fibers in core and chopped glass fibers to make rips on the surface of rebar. Flexural test was performed on concrete beam specimens reinforced with the developed GFRP rebar at various reinforcement ratios. The stiffness of the beams reinforced with GFRP was lower than those with steel rebar. The ultimate strength, however, was improved by using the GFRP rather than the steel rebar. The rip-shaped surface provided better bonding between the GFRP rods and concrete and no significant slip/debonding was observed. In addition, the load and deflection increased gradually until the complete failure without apparent yielding. The current equations for estimating the ultimate moment was too conservative by underestimating values. However, as the reinforcement ratio increased, the difference calculated values became closer to the measured.
Rehabilitation of Reinforce Concrete Frames with Reinforced Concrete Infills
Authors: Choi Chang Sik , Lee Hye Yeon
Published: March 2009

The purpose of this study is to understand the fundamental resistance mechanism and the
shear strength of the frame with the reinforced concrete infill wall by comparing analytical with
experimental results. For this, one-story and one-bay four specimens were manufactured with variables;
Lightly Reinforced Concrete Frame (LRCF), monolith placing Shear Wall (SW), CIP Infill Wall
(CIW-1) and CIP Infill Wall reinforced with diagonal rebar (CIW-2). The addition of the RC infill wall
was significantly improved the strength and the stiffness. Compared with specimen LRCF, ultimate
strength and initial stiffness of infills was improved 4 and 6 times, respectively. The case of specimen
CIW-2, structural performance was improved remarkably by placing a diagonal rebar.
Mechanics Characteristics and Failure Criteria of Concrete Confined by One-Way Lateral Stress after Suffering High Temperature
Authors: Qin Li Kun , Song Yu Pu , Wang Yu Jie , Zhao De Shen , Yao Jia Wei
Published: March 2009

Biaxial compressive tests of plain concrete specimens under normal temperature and suffering high temperature(200600 )were completed under four lateral constant stress rates. The tests were completed by using the large static-dynamic triaxial test system for concrete in the State Key Laboratory of Coastal and Offshore Engineering, Dalian University of Technology. The biaxial compressive strength and deformation characteristics of concrete confined by lateral stress after suffering different temperature were studied in a systematic way. On the basis of the tests, the failure criterion of concrete subjected to constant lateral compressive stress after suffering different temperature was established in the Octahedral stress space. The conclusions can provide the testing and theoretical basis for deeper study of the concrete construction subjected to biaxial compressive combined loads suffering different temperature such as chimney, building after fire and safety shell for nuclear reactor.
Effects of Matrix Ductility on Damage Tolerance of Diagonally Reinforced Coupling Beams
Authors: Yun Hyun Do , Kim Sun Woo , Cheon Esther , Park Wan Shin
Published: March 2009

This paper investigates the effect of the ductile deformation behavior of high
performance hybrid fiber-reinforced cement-based composites (HPHFRCCs) on the shear behavior
and damage of diagonally reinforced coupling beams under reversed cyclic loading. The effects of
matrix ductility on deflections, crack widths, crack patterns, failure modes, and ultimate shear load
of the coupling beams have been examined. The combination of a ductile cement-based matrix and
steel reinforcement is found to result in improved energy dissipation capacity and damage-tolerant
inelastic deformation behavior. Test results showed that the coupling beam constructed with an
HPHFRCC material exhibited excellent strength, deformation capacity, and damage tolerance
capacity, in comparison with the regular reinforced concrete beam.
Semi-Analytical Finite Element Method for Bilinear Cohesive Crack Model in Mode I Crack Propagation
Authors: Wang Cheng Qiang , Chen Zhong Hua , Zheng Chang Liang
Published: March 2009

Based on the Hamiltonian theory and method of elasticity, a ring and a circular
hyper-analytical-elements are constructed and formulated. The hyper-analytical-elements give a
precise description of the displacement and stress fields in the vicinity of crack tip for the bilinear
cohesive crack model. The new analytical element can be implemented into finite element method
program systems to solve crack propagation problems for plane structures with arbitrary shapes and
loads. Numerical results for typical problems show that the method is simple, efficient and accurate.
Computation of Effective Fatigue Thresholds Based on a New Concept of Crack Closure
Authors: Horníková Jana , Šandera Pavel , Pokluda Jaroslav
Published: March 2009

A new theoretical concept of crack closure under plain strain was applied to assess the
effective fatigue threshold under various loading condition for selected aluminium and titanium
alloys of different microstructures. The concept is based on the long-range effect of geometrically
necessary dislocations remaining in the wake of propagating fatigue cracks. Calculated threshold
values FKeff,th for 7475 aluminium alloy are about 1.9 MPa.m1/2 (in vacuum) and 1 MPa.m1/2 (in
air), and about 2.5 MPa.m1/2 and 3.3 MPa.m1/2 for c-titanium and Ti-2.5%Cu, respectively. All
calculated values are nearly independent on both the microstructure and the applied stress ratio and
they are in a good agreement with experimental data.
Experimental Research on Crack Propagation in U71Mn and U75V Rail Steels
Authors: Li Jing Jing , Guo Ya Fang , Wang Yue Sheng , Tian Chang Hai
Published: March 2009

In this paper, the continuous in-situ observations of the fatigue crack growth in U71Mn and
U75V rail steel are made by using the scanning electronic microscope (SEM). The microstructure
patterns of cracks under the mode I fatigue loads and quasi-static loads are presented. The results
indicate that the short fatigue crack growth in rail steel is a quasi-cleavage fracture. The ductility and
the performance of fatigue resistance of U71Mn rail steel are better than those of U75V rail steel.
Plastic Deformation of Rivet in Cylindrical Structure
Authors: Lee Jong Woong , Kong Cheol Won , Eun Se Won , Park Jae Sung , Jang Young Soon , Yi Yeong Moo
Published: March 2009

Many methods can be used to assemble large mechanical structures. Using rivets is one of these methods. Rivets are lighter than bolts and allows for efficient assembly. The cylindrical structure has a discontinuous rivet assembled region. So concentration load operates in the edge of discontinuous assembled region. This paper evaluates the force placed upon rivets used to assemble cylindrical structures and strength of structures assembled with rivets. Plastic deformation of rivets occurs at 4 kN and rivets are destroyed at 7 kN. However, rivets are designed to transfer load to neighboring rivets when they are overloaded. Structural test were accomplished using tension and bending load condition. The structural tests showed that plastic deformation first occurs in the fastening where the rivet meets the outside of the cylinder and a number of rivets exhibited this type of deformation. The secondary phase of deformation occurs in the fastening where the rivet meets the inside of the cylinder. Despite the plastic deformation, the structural tests showed that the rivets succeeded in redistributing load to neighboring rivets and as a result, no rivets were destroyed.
Fatigue Life Evaluation of Bolt Having Tightening Torque under Random Loading
Authors: Choi Young Woo , Noh Byeong Wook , Song Jung I. , Bae Sung In
Published: March 2009

The fatigue life of hexagon head and socket head bolts, attached to vehicle a wheel, is
assessed and the estimation of the residual life of existing bolts in vehicle wheel is investigated. Fieldmeasured
load histories were applied in this test. Tensile tests and fatigue tests were performed to
evaluate the effect of tightening torque and to obtain the basic experimental data. Miner’s rule was
used to predict the fatigue life of bolts. The results indicate the prediction of fatigue life of the bolts
was in good agreement with the real life of vehicle wheel bolts in this test.
A Nonhomogeneous Piezoelectric Material Plate with a Moving Crack
Authors: Wang Bao Lin , Han Jie Cai
Published: March 2009

This paper investigates a moving crack in a nonhomogeneous piezoelectric material
(NPM) plate. The mechanical and electrical properties of the plate are considered for a class of
functional forms for which closed-form expressions for the moving crack tip electromechanical
fields are obtained. Effect of material non-homogeneity and crack moving velocity on the crack tip
fields are discussed. The crack moving velocity can increase or decrease the stress intensity factor.
The cleavage stress, τθz, however, is always an increasing function of crack moving velocity.
Plastic Dissipation and Temperature Field around a Steady Running Crack
Authors: Luo Wen Bo , Yang Ting Qing
Published: March 2009

Temperature field is formed due to heat dissipation when material is subjected to irreversible deformation. In this paper, the heat dissipation in the crack-tip plastic zone was considered. By considering the propagating crack-tip plastic zone as a running heat source and constructing a reasonable heat source density distribution function, the temperature field around a steady running crack was obtained. It is shown that temperature rise is dependent on the crack growth speed and the material parameters. The maximum temperature rise reaches to >50 oC in our example calculations for a steady running crack in PMMA.
Three Phase Micromechanical Modeling for a Shape Memory Alloy Reinforced Composite
Authors: Zhu Yu Ping , Dui Guan Suo
Published: March 2009

In this paper, combined the micromechanical and the thermodynamic theory, a three phase
model for the SMA composite is developed, in which the composite is considered as the austenitic
phase, the product phase (martensite) and the matrix phase. In the present model, the interaction
among the three phases is analyzed. From the micromechanical analysis, the macroscopic free energy
function is found. Then macroscopic transformation strain, effective elastic compliance, macroscopic
constitutive model are derived.Compared with the traditional two-phase method, non-linearity of
SMA need not be considered. The method is not only simply but also the interaction among the three
phases is considered. As an application of above model, we consider the case of a composite with
NiTi/epoxy, illustrate the predicted stress-strain response of it under isothermal loading and
unloading conditions and analyses the effects of temperature and fiber volume on macroscopic
mechanical property. By comparing with references, it is shown that the results are credible. It is
helpful to design the intelligent composite.
Nonlocal Theory Solution for Mode III in an Infinite Strip of FGMs
Authors: Bi Xian Shun , Liu Bao Liang
Published: March 2009

This article provides a theoretical and numerical treatment of a crack subjected to an
anti-plane shear loading in an infinite strip of FGMs. The crack situated in the mid-plane of strip
moves at a constant velocity. It is assumed that the shear moduli varies continuously in the
thickness direction and is to be of exponential form. The mixed boundary value problem is reduced
to a pair dual integral equations by means of nonlocal elasticity theory and integral transform
method. The stress field and displacement field for the strip are solved near the tip of the crack by
using Schmidt’s method. Then the influences of the characteristic length, graded parameters and
crack velocity on the stress at crack tip are studied. Unlike the classical elasticity solution, the
magnitude of stress at the crack tip is finite, and it is found that the maximum stress increases with
the crack velocity as the strip length is decreased, and the maximum stress decreases with the
characteristic length as the graded parameters is increased.
Dynamic Fracture of Mode I Crack in Orthotropic Composites Studied by Caustics Method
Authors: Gong Ke Zhuang , Qin Wei Zhong , Li Zheng , Fu Bin
Published: March 2009

In this paper, the optical method of caustics is developed to apply in dynamic fracture
problems of orthotropic materials. The initial curve and the caustics formulas about mode-I crack
are derived first from the distribution of stress field to determine the dynamic stress intensity factor
(SIF). Meanwhile, dynamic caustics experiments are performed to study the dynamic fracture
process of orthotropic materials, during which the dynamic fracture toughness and the velocity of
crack propagation are calculated directly from the series of caustics patterns. Moreover, typical
mesoanalysis of fracture section are done by a scanning electron microscope (SEM), revealing the
fracture mechanism of fiber reinforced material.