bluuebunny/crossref_metadata_2025 huggingface dataset:
Residual Stress Estimation with Identification of Stress Directionality Using Instrumented Indentation Technique
Authors: Han Jae Hwan , Lee Jung Suk , Lee Yun Hee , Choi Min Jae , Lee Gyu Jei , Kim Kwang Ho , Kwon Dong Il
Published: March 2009

The instrumented indentation technique (IIT) has recently attracted significant research
interest because it is nondestructive and easy to perform, and can characterize materials on local
scales. Residual stress can be determined by analyzing the indentation load-depth curve from IIT.
However, this technique using a symmetric indenter is limited to an equibiaxial residual stress state.
In this study, we determine the directionality of the non-equibiaxial residual stress by using the
Knoop indentation technique. Different indentation load-depth curves are obtained at nonequibiaxial
residual stresses depending on the Knoop indentation direction. A model for Knoop
indentation was developed through experiments and theoretical analysis.
Deformation Behavior of Magnesium Single Crystals in C-Axis Compression
Authors: Kitahara Takaaki , Ando Shinji , Tsushida Masayuki , Kitahara Hiromoto , Tonda Hideki
Published: March 2009

In general, deformation behavior of magnesium in compression is different from tensile.
To investigate deformation behavior of magnesium single crystals, c-axis compression was
performed. The crystals were yielded by second order pyramidal slip, and the yield stress shows
anomalous temperature dependence (increased with increasing temperature) between 203K and
293K. Yield stress of c-axis compression is bigger than that of a-axis tensile. {10-13} twin and
{11-24} twin occurred at 77293K and 77473K respectively. Fracture surface at 77293K was
{11-24} and at 473K was {11-22}.
Welding of High Carbon Steel without Transformation
Authors: Fujii Hidetoshi , Cui Ling , Nogi Kiyoshi
Published: March 2009

A high carbon steel joint, S70C (0.72wt%C) was successfully friction stir welded without
any postheat treatments. There are two methods for obtaining proper joint properties. The first method
is to decrease the peak temperature to below A1, and the other method to decrease the cooling rate to
less than the lower critical cooling rate. As a result, the ultimate tensile strength of 1214 MPa, 0.2 %
proof strength of 700 MPa and elongation of 40% were obtained for a joint.
Two Methods for Determination of Fatigue Crack Propagation Limit Curves and their Application for Different Materials
Authors: Lukács János
Published: March 2009

There are different documents containing fatigue crack propagation limit or design curves
and rules for the prediction of crack growth. The research work aimed to characterise the fatigue crack
propagation resistance of different materials using limit curves and determination of limit curves
under different loading conditions, based on statistical analysis of test results and the Paris-Erdogan
law. With the help of the characteristic values of threshold stress intensity factor range (Kth), two
constants of Paris-Erdogan law (C and n), fatigue fracture toughness (Kfc) or fracture toughness (KIc)
two reliable method can be proposed. The limit curves calculated by both methods represent a
compromise of rational risk (not the most disadvantageous case is considered) and striving for safety
(uncertainty is known).
Prevention of Dicing-Induced Damage in Semiconductor Wafers
Authors: Lee Seong Min
Published: March 2009

Semiconductor devices are usually formed on a single silicon wafer during a batch processing method. Individual devices are separated from the wafer during the wafer sawing or dicing step. Subsequent packaging processes are then performed on the individual devices, whose edge portions are very susceptible to mechanical damage from the sawing process. Defects formed along device edges due to the dicing saw blade often provide potential sites for serious reliability problems. If the scribing area is reduced, the number of the separated devices from a single wafer increases, which results in productivity improvement. However, the closer the scribing position of the saw blade comes to the active device pattern, the greater possibility of sawing-induced damage to the active pattern is. Thus, this work shows methods to reduce the negative impact of the saw blade while maintaining close proximity of the scribe lines to the IC devices. In particular, this work suggests that a decrease in the size of the diamond particles embedded in the saw blade and in the rotation speed of the saw blade might contribute to the prevention of sawing-induced damage to device patterns.
Superplastic Behavior of Ultrafine Grained Al Alloys Fabricated by Severe Plastic Deformation
Authors: Hwang Duck Young , Kwon Kion , Shin Dong Hyuk , Park Kyung Tae , Ko Young Gun , Lee Chong Soo
Published: March 2009

Ultrafine grained (UFG) 5083 Al and 5154 Al alloys were prepared by equal channel
angular pressing (ECAP) with an effective strain of ~ 4 or ~ 8. This investigation was aimed at
examining the effect of the ECAP strain and post-rolling inducing different microstructure in these
alloys on the deformation mechanisms at low temperature superplastic (LTS) and high strain
superplastic (HSRS) regimes. The sample after 4 passes (a strain of ∼ 4) did not exhibit LTS, but
superplastic elongations were obtained in the sample after 8 passes (a strain of ∼ 8). An analysis of
the mechanical data in light of the standard deformation mechanisms revealed that deformation of
the sample after 4 passes was governed by dislocation climb while grain boundary sliding attributed
to LTS of the sample after 8 passes. In addition, the 5154 Al alloy processed by ECAP and postrolling
was capable of enhancing HSRS elongation significantly. An analysis revealed that the
deformation mode was changed from dislocation viscous glide to grain boundary sliding by
additional ECAP strain and post-rolling.
A Stage Based on Voice Coil Motor with High Speed and Long Range for Laser Micro/Nano Fabrication
Authors: Kim Ki Hyun , Gweon Dae Gab , Jung Hyun Soo , Lee Soo Hun , Hong Min Sung , Lee Moon G.
Published: March 2009

Design of design of X-Y-Theta fine stage using VCM (voice coil motor) is presented in this
paper. This fine stage is combined with linear DC motor. Long range, high speed and high precision
of the stage is obtained by using dual servo control for laser micro/nano machining. A novel structure
of VCM for the fine stage is proposed. The fine stage can have 3 DOF(X-Y-Theta) motion by four
VCM actuators which are located on the same plane. The X-Y-Theta fine stage is designed to have
high acceleration for high throughput. Based on the design, the stage is fabricated. The designed stage
has the acceleration of 5m/s2 with 45kg total mass. In addition, this actuator is feedback controlled
using HP laser interferometer. The reaction force between the coarse and fine stage of the dual servo
is compensated by force compensator.
An Adaptive Wavelet Finite Element Method with High-Order B-Spline Basis Functions
Authors: Tanaka Satoyuki , Okada Hiroshi
Published: March 2009

In this paper, an adaptive strategy based on a B-spline wavelet Galerkin method is
discussed. The authors have developed the wavelet Galerkin Method which utilizes quadratic and
cubic B-spline scaling function/wavelet as its basis functions. The developed B-spline Galerkin
Method has been proven to be very accurate in the analyses of elastostatics. Then the authors added a
capability to adaptively adjust the special resolution of the basis functions by adding the wavelet basis
functions where the resolution needs to be enhanced.
Transformation Plasticity and the Effect on Quenching Process Simulation
Authors: Inoue Tatsuo , Tanaka Tomohiro , Ju Dong Ying , Mukai Ryuji
Published: March 2009

Mechanism of transformation plasticity (TP) is discussed from continuum mechanics
viewpoint, and derivation of TP law from the unified thermo-mechanical and transformation
plasticity constitutive equation. Result of identified TP coefficient for a chromium steel (JIS SCr420)
by use of multi-functional testing machine is introduced as one of the material data together with other
data to the simulation of a quenching process by use of newly developed code COSMAP. The
simulated distribution of temperature, phases and stress/distortion are compared with the
experimentally measured values to verify the accuracy.
New Image Processing Tools for Structural Dynamic Monitoring
Authors: Morlier Joseph , Salom P. , Bos F.
Published: March 2009

This paper presents an introduction to structural damage assessment using image processing on real data (non ideal conditions). Our contribution is much more a groundwork than a classical experimental validation. After measuring the bridge dynamic parameter on a small resolution video, we conjointly present advantages and limitations of our method. Finally we introduce several “computer vision” based rules and focus on the technical ability to detect damage using camera and video motion estimation.
Structural Identification and Health Monitoring on the Historical Architectural Heritage
Authors: de Stefano Alessandro
Published: March 2009

Architectural heritage is a resource and a fundamental part of the cultural European background; it also causes concern, due to the huge investment needed to maintain it, or even to repair it after environmental injuries. The Author is general coordinator of an Italian National research project aimed to formulate new guidelines for structural health monitoring and survey of historical and monumental structures. The Project programme traces a general strategy to build maintenance related monitoring procedures, to face the problems of data uncertainties, to propose robust approaches. This paper shows the general path traced for that project, just now at its start-up phase, but the main attention is addressed to the robust approaches to dynamic testing and model updating.
A Numerical Determination of Acoustic Emission Sensor Response in Plates Using Dispersion Curves
Authors: Pullin Rhys , Theobald Pete T. , Holford Karen M. , Evans S.L.
Published: March 2009

This paper reports on a method for numerically modelling acoustic emission signals in simple plate geometries using dispersion curves. It is demonstrated how, by using a known source to sensor distance, it is possible to determine the arrival of the frequencies of the individual AE modes at the sensor face. Assumptions based on sensor frequency response and the amplitude of individual modes allow for an approximation of each mode arriving at the sensor face. These modes are then summed to provide a numerical model of the expected signal. Results of the model are compared with a recorded signal and show good correlation, this is further demonstrated by comparing the wavelet transforms of the modelled and recorded signal.
Distributions of Local Damage Variable and Local Plastic Tensile Strain and Precursors to Failure of Quasi-Brittle Pure Bending Beam
Authors: Wang X.B.
Published: March 2009

For many quasi-brittle materials (such as rock, ceramic and concrete) in pure bending state,
the material on the tensile side will fail firstly since the compressive strength can be ten times the
tensile strength. After tensile strain localization zone is initiated in the midspan of the beam, its
propagation direction will be perpendicular to the neutral axis. In the paper, using nonlocal theory or
gradient-dependent plasticity, the distributions of local plastic tensile strain and local damage variable
in tensile strain localization zone of a pure bending beam are analyzed theoretically. The evolutions of
the maximum local plastic tensile strain, the maximum local damage variable and the bending
moment with tensile stress acting on the tensile side are presented through examples. The
distributions of local plastic tensile strain and local damage variable in tensile strain localization zone
are highly nonuniform due to microstructural effect. When the maximum bending moment is reached,
the maximum local damage variable is proportional to the ratio of elastic modulus to elastoplastic
modulus, while the maximum local plastic tensile strain is inversely proportional to elastic modulus
and elastoplastic modulus. For quasi-brittle materials, the elastoplastic modulus that is a constitutive
parameter equal to the absolute value of the slope of tensile stress-tensile strain curve in
strain-softening stage is much higher. The present theoretical results mean that the precursors to
failure are less apparent for extremely brittle materials.
Incipient Crack Identification in Beam Structures Using the Slope of the Anti-Resonance Curve
Authors: Wang Dan Sheng , Zhu Hong Ping , He Bo
Published: March 2009

Crack damage brings a serious threat to the safety of mechanical and civil structures, and
the problem of incipient damage identification of structures has been paying attention as a puzzle by
many researchers in recent years. To seek for an alternative solution of the problem, a method for
incipient crack localization using the slope of the anti-resonance curve is proposed in this paper.
The method makes use of the driving-point mechanical impedance characteristics of cracked beams
stimulated by harmonic force. To characterize the local discontinuity due to the presence of crack, a
simplified rotational spring model is presented to model the crack. Subsequently, the proposed
method is verified by a numerical example of cracked beam under simple support or cantilever
boundary conditions.
Experience and Technologies in NDT of Ropes
Authors: Carriatore Vincenzo , Canova Aldo , Vallan Alberto , Vusini Bruno
Published: March 2009

This paper deals with recent developments in non-destructive tests on operating steel wire
ropes, with the aim of analyzing their conditions and residual resistance. The instruments for
executing magneto-inductive tests on wire ropes - employed in cableways, chairlifts, mine elevators
and, occasionally, in equipment for handling material in harbours (e.g. gantry cranes and portainers)
– are commonly composed of three parts: the revealing device (detector); power supply; and a
recorder, equipped with an amplification apparatus and paper rolls for printing the results. The
system proposed in this work is composed of an innovative magnetic detector where the traditional
paper recording system is substituted with a software interface that allows a digital recording of the
signal. The performances in terms of accuracy and linearity of the proposed detector are tested
through proper laboratory set up and are presented and discussed.
Cyclic Plasticity of a Cracked Structure Subjected to Mixed Mode Loading
Authors: Pommier Sylvie
Published: March 2009

Cyclic plasticity in the crack tip region is at the origin of various history effects in fatigue.
For instance, fatigue crack growth in mode I is delayed after the application of an overload because
of the existence of compressive residual stresses in the overload’s plastic zone. Moreover, if the
overload’s ratio is large enough, the crack may grow under mixed mode condition until it has gone
round the overload’s plastic zone. Thus, crack tip plasticity modifies both the kinetics and the
crack’s plane. Therefore modeling the growth of a fatigue crack under complex loading conditions
requires considering the effects of crack tip plasticity. Finite element analyses are useful for
analyzing crack tip plasticity under various loading conditions. However, the simulation of mixed
mode fatigue crack growth by elastic-plastic finite element computations leads to huge computation
costs, in particular if the crack doesn’t remain planer. Therefore, in this paper, the finite element
method is employed only to build a global constitutive model for crack tip plasticity under mixed
mode loading conditions. Then this model can be employed, independently of any FE computation,
in a mixed mode fatigue crack growth criterion including memory effects inherited from crack tip
plasticity. This model is developed within the framework of the thermodynamics of dissipative
processes and includes internal variables that allow modeling the effect of internal stresses and to
account for memory effects. The model was developed initially for pure mode I conditions. It was
identified and validated for a 0.48%C carbon steel. It was shown that the model allows modeling
fatigue crack growth under various variable amplitude loading conditions [1]. The present paper
aims at showing that a similar approach can be applied for mixed mode loading conditions so as to
model, finally, mixed mode fatigue crack growth.
Molecule Mechanics Simulation on the Deformation and Damage Process in POSS Nanocomposite
Authors: Sun Yi , Zeng Fan Lin
Published: March 2009

The deformation and damage process of POSS nanocomposite is investigated by molecule
mechanics (MM) simulation. Firstly, the nano-scale models of two kinds of homopolymers, pure
polystyrene (PS) and polystyrene attached with 5 mol% propyl-POSS (P-POSS-PS) were built. Then
the mechanical behaviors of these two kinds of hybrid materials under focused uniaxial tensile
loading and the remote uniaxial tensile loading are examined by MM simulations. It is found that a
small quantity of POSS can observably increase the tensile modulus of the normal polymers. During
tensile loadings, micro voids appear in the polymer matrix. With the increase of deformation, the
micro voids become bigger and then connect to form the damage in bigger area. The POSS monomers
prevent these micro voids from coalescence and thus retarding the formation of the damage. This
would be helpful in understanding the reinforcement mechanism of POSS and provide important
referential message for the applications of POSS.
Progressive Failure Analysis of Composite Pressure Vessels by Finite Element Method
Authors: Tong Li Li , Wang Zhen Qing , Chen S.H. , Sun Bao Hua
Published: March 2009

The progressive failure analysis of composite pressure vessel under hydrostatic pressure
has been carried out. The composite pressure vessel has been modeled by using layer structural
shell element. After the failure of the weakest ply, the stiffness is reduced by either fiber failure or
matrix failure. The stiffness of failed element has been totally discarded and other element are
considered to remain unchanged after the weakest ply failure. The stress of the laminate at the same
point is evaluated again to see if the laminate can carry additional load. This ply-by-ply analysis
progresses until the ultimate strength of the pressure vessels is reached. A parametric study has been
done on the progressive failure analysis.
Crack Growth Process of Ni-Single Crystal with Cathodic Hydrogen Charging
Authors: Matsui H. , Takano Noriyuki
Published: March 2009

Notched tensile tests {orientation: tensile axis [001], direction of notching [010]or[110] }
were performed to investigate the crack growth process in Ni-single crystal with hydrogen cathodic
charging. Y-shaped hillocks and striation-like patterns were observed on the fracture surfaces of
hydrogen embrittled specimens using the scanning electron microscope (SEM). The Y-shaped
hillocks are exactly matched on both fracture surfaces of a specimen. In addition, cleavage fracture
is occurred between a Y-shaped hillock and next one. It means that the cleavage fracture is occurred
at first, and the Y-shaped hillock is secondary formed. It is considered that the striation-like pattern
is formed by the localized slips and cleavage fracture between them. Peach-Koehler’s law leads that
the dislocations on the equivalent slip systems with (111　)　[101] are subjected to the highest force of
all dislocations at the crack tip. Furthermore, Ni-hydride was not observed on the surface of
specimen just after charging hydrogen. Thus, it was concluded that Y-shaped hillock and
striation-like pattern were occurred in Ni-single crystal with charging hydrogen under condition that
Ni-hydride is not formed.
Fatigue Analysis of Forged Aerospace Components Based on Micro Structural Parameters
Authors: Riedler Martin , Stockinger Martin , Stoschka Michael , Eichlseder Wilfried
Published: March 2009

With the objective of creating a simulation model for the lifetime calculation of
forged aerospace components it is necessary to clarify the damage mechanisms in the
materials used. This has been researched for the Ni-base alloy Inconel 718 by varying the
forging parameter effective plastic strain rate, which is realised by using three types of
equipment: hydraulic press, screw press and hammer. Specimens processed at the screw press
show the highest lifetime by keeping all other forging parameters unvaried. Micro structural
investigations show that the amount and morphology of dominant as-large-as grains play a
important role. This methodology is currently investigated for Ti-6Al-4V. Lifetime tests show
that besides effective strain and anisotropy the influence of morphology is important. As soon
as the model status allows lifetime analyses the thermo-mechanical process (forging and heat
treatment) can be developed depending on the desired lifetime specifications in order to
realise an interdisciplinary lifetime optimisation of forgings. A further aim is the use of basic
coherences of safe-life and fail-safe approaches in the low and high cycle fatigue region in
order to reasonable handle with flaws and defects at the edge layer.
Patternanalysis of the Severity of Multiple Crack Arrays
Authors: Horst Peter
Published: March 2009

Multiple Site Damage (MSD) is a typical problem of aging aircraft structures. On the
other hand a similar situation may occur, if damages in the vicinity of the crack tip of a large crack
is investigated. In some preceding papers the author has shown the possibility to assess the
criticality of a MSD-scenario by comparing certain data compression measures of the crack scenario
in an early stage. All of these scenarios were linked to cracks in one row of fasteners of equal
distance, and the method was used in conjunction with the Monte-Carlo Simulation. The idea of
using such ways to assess multiple crack scenarios is extended now in the paper presented here. The
investigations are extended now in the sense that, the scenarios are more complex as they include
large cracks and small cracks in the vicinity of the crack, where no fixed distance of the cracks is
foreseen. The attempt is made to relate such results to experimental data on residual strength and
therefore, to relate them to sophisticated models like the Gurson model.
Failure Assessment and Reliability Analysis of CFRP Composite Pressure Vessel
Authors: Shen Jun , Zhang M.L. , Hou D.Y.
Published: March 2009

A new approach for progressive failure and reliability analysis of carbon fiber reinforced
polymeric (CFRP) composite pressure vessel with many base random variables is developed in the
paper. The elastic constants of CFRP lamina and geometric parameters of the vessel are selected as
the base design variables. CFRP lamina specimen and pressure vessel were manufactured and tested
in order to obtain statistics of design variables. The limit state function for progressive failure
analysis was set up. Then the progressive failure and reliability analysis of the vessel were
performed according to the stiffness degradation model based on Monte Carlo simulation procedure
using MATLAB. The distributions of failure loads and the probability of failure of the vessel were
obtained. The feasibility and accuracy of the proposed method is validated by good agreement
between the simulation and experimental results. Further analysis indicates that the lamina tensile
strength in the fiber direction and hoop layer thickness of the vessel have significant influence on
the probability of failure of composite pressure vessel.
Investigation of the Dynamic Damage of the Rocks Subjected to Short Pulse Laser
Authors: Xu Song Lin , Xi Dao Ying , Tang Zhi Ping , Du Yun
Published: March 2009

Some preliminary experiments are conducted to investigate the responses of granite，
marble and red stone in the states of natural，water-saturation and oil-saturated under the shock of
short pulse laser. The 3D contour of ablation pit and the preliminary relations of the ablation
contour to the number of laser pulses are obtained. The results show that some cracks generate at
local places for the shock of laser，and the degree of ablation of the oil-saturated rocks is more
severe than that of the natural and water saturated rocks. However，further work should be
conducted to control the direction，sizes and number of cracks generated under the shock of laser.
Study on Crack Propagation Behavior of Asphalt Concrete under Uniaxial Compression Load by Using CT
Authors: Xie Tao , Qiu Yan Jun , Jiang Ze Zhong , Lan Bo
Published: March 2009

Various asphalt pavement distresses, such as longitudinal cracking, thermal (transverse)
cracking, and reflective cracking, are directly related to the fracture properties of the asphalt
materials used in the pavement layers. The fracture resistance of asphalt materials significantly
influences the service life of asphalt pavements and consequently affects the maintenance and
rehabilitation costs of the pavement network. Therefore, there is significant interest in
understanding the mechanism of fracture in asphalt pavements and in developing analysis tools that
would lead to the selection of asphalt materials with increased fracture resistance. This paper
reports a research effort of dynamic observation of the micro-fracture process of asphalt mixture
under uniaxial compressed condition by using CT (computerized tomography) method. CT images
were analyzed to investigate the process of micro-fracture of asphalt concrete. Research results
show that the abnormal belt of density damage of asphalt concrete is the initiation belt of cracking
and the turning point in the curve of stress and density distress increment is the point of cracking
failure of asphalt concrete.
Stochastic Improvement of the Residual Strength of a Stiffened Panel
Authors: Caputo Francesco , Lamanna Giuseppe , Soprano Alessandro
Published: March 2009

The objective of robust design is to optimize the mean of a given target variable and to
minimize the variability that results from uncertainty represented by “noise” factors. A recent
strategy for robust design is based on stochastic processes, which has resulted in a new design
technique called “stochastic design improvement” (SDI). In this work a home-made procedure is
presented, which is based on the SDI technique and which is illustrated with reference to a case
study which aims to increase the residual strength of a cracked stiffened aluminum panel.
The Influence of Loading Ratio on Fatigue Crack Propagation Through a Bi-Material Interface
Authors: Náhlík Luboš , Hutař Pavel , Knésl Zdeněk
Published: March 2009

The paper is devoted to fatigue crack propagation in layered materials. The influence of
plasticity induced crack closure on threshold values for fatigue crack propagation through interfaces
between different materials layers is studied. The main aim was to estimate the influence of the
loading ratio R on threshold values for crack propagation through a bi-material interface as a
function of the elastic mismatch of both materials. The finite element method (FEM) is used for
numerical calculations. Results obtained for different loading ratios, materials, boundary conditions
and magnitude of applied loading can be generalized and used for the design of composite bodies
with different material layers.
Hopf Bifurcation and Chaos Synchronization for a Class of Mechanical Centrifugal Flywheel Governor System
Authors: Chu Yan Dong , Zhang Jian Gang , Li Xian Feng , Chang Ying Xiang
Published: March 2009

Chaos and chaos synchronization of the centrifugal flywheel governor system are studied
in this paper. By mechanics analyzing, the dynamical equation of the centrifugal flywheel governor
system are established. Because of the non-linear terms of the system, the system exhibit both
regular and chaotic motions. The evolution from Hopf bifurcation to chaos is shown by the
bifurcation diagrams and a series of Poincaré sections under different sets of system parameters,
and the bifurcation diagrams are verified by the related Lyapunov exponent spectra. This paper
addresses control for the chaos synchronization of feedback control laws in two coupled
non-autonomous chaotic systems with different coupling terms, which is demonstrated and verified
by Lyapunov exponent spectra and phase portraits. Finally, numerical simulations are presented to
show the effectiveness of the proposed chaos synchronization scheme.
The Hysteretic Energy Analysis of Inelastic Structures during the Earthquake
Authors: Zhai Chang Hai , Liu Hong Bo , Li Ning , Xie Li Li
Published: March 2009

The hysteretic energy is an important parameter to measure the plastic cumulative damage
of structures during earthquake. In this paper, with a great number of ground motions collected in the
1999 Chi-Chi, Taiwan, earthquake, the main features of constant-ductility hysteretic energy spectra is
analyzed. And the effects of site condition, structural period, ductility level, damping on hysteretic
energy are investigated. It is concluded that for a given period, spectra decrease with ductility ratio
increases. And as the ductility ratio increase, the spectra will be closer. In the short-period region
(about less than 0.8s), spectra are strongly dependent on the structural period. In the long-period
region, spectra tend to be constant. The limiting period depends on the ductility ratio and the local site
conditions. The damping has similar effect on spectra for all the structural period regardless ductility
ratio.
Numerical Investigations of Corner Singularities in Cracked Bodies
Authors: Hutař Pavel , Náhlík Luboš , Knésl Zdeněk
Published: March 2009

The influence of corner singularity on the distribution of the stresses around the crack
front for a three-dimensional structure is described in this paper. The distribution of stress
singularity through the thickness of the middle tension specimen provides us an indication of crack
behaviour close to a free surface. An estimation of the region where the change of singularity
exponent plays an important role in fatigue crack propagation rate was carried out. A decrease in
fatigue crack propagation rate close to the free surface was found. The lower fatigue crack
propagation rate in the boundary layer in comparison with the interior of the specimen leads to a
change of intersecting angle between crack and free surface and depends on Poisson’s ratio.
Structural Damage Survey Using Nondestructive Tests Based on Stress Waves
Authors: Cho Young Sang , Hong Seong Uk
Published: March 2009

The impact echo method has been widely used to evaluate the integrity of concrete
structures. This paper is to study damage detection technique of concrete members using impact
echo method, one of the nondestructive tests based on stress waves. Stress wave propagation
behavior is to be studied based on wave mechanics in concrete media. Based on the theoretical
study, nondestructive tests using stress waves will be conducted to observe the wave behavior on
structural damages. For the damage detection of concrete structures, a mock-up specimen was
prepared, and various tests were conducted for the study of the behavior of stress waves. The
concrete slab of the flaw detection consist of 5 types; the first group for the thickness presumption,
the second group for the position of the voids, the third group for the position of the re-bars, the
fourth group for the position conduit, and the fifth group for the position of the crack. Test results
are evaluated and summarized to verify if the nondestructive tests can survey damages in the
concrete structures in this paper.
Study of Optimized Steel Truss Design Using Neural Network to Resist Lateral Loads
Authors: Cho Young Sang , Xia Lin , Hong Seong Uk , Kim Seong B. , Bae Jun S.
Published: March 2009

Structural optimization is widely adopted in the design of structures with the
development of computer aided design (CAD) and the development of computer technique recently.
By applying the artificial neural network to structural optimization, designers can gain the design
scheme of structures more feasibly and easily. In this paper, the genetic algorithm (GA) used in the
error back-propagation (BP) network is applied to get the optimization result of the structural
system. And the training pair of BP neural network is obtained from the structural analysis using a
finite element program. The case study of 10 member truss structure using GA and BP will be
helpful to reduce the cost of structures which is related to weight and the dynamic performance of
optimization under the lateral load.
Study on the Mechanical Properties of Reinforcement Damaged by Reinforcement Corrosion
Authors: Lee Han Seung , Kyung Je Woon , Lee Sung Bok
Published: March 2009

This study was carried out to investigate quantitatively the relationship between the degree
of reinforcement corrosion and the mechanical properties of reinforcement. In the experiment, the
tensile test of corroded reinforcement was conducted at the different stage of the degree of
reinforcement corrosion. As a result, it was found that the chloride-induced corrosion induce the
pitting and the corrosion using electrical current induce the uniform corrosion. As the degree of
reinforcement corrosion increased, the nominal yield point and nominal elastic modulus both
decreased. Also, there were very high correlations between the degree of reinforcement corrosion and
the mechanical properties of reinforcement. We could make the material constitutive laws for the
mechanical properties of reinforcement as a function of the degree of reinforcement corrosion to
analyze the damaged RC members with reinforcement corrosion using finite element method.
Effect of Carbon Fiber Sheets on Flexural Strengthening of RC Beams Damaged by Corrosion of Tension Rebar
Authors: Lee Han Seung , Shin Sang Heon , Kyung Je Woon
Published: March 2009

RC beam with corroded tension rebars were strengthened with carbon fiber sheets(CFS)
and were subjected to static loading tests to investigate the flexural strengthening effect of CFS. The
test results confirmed that CFS are effective in reducing stresses to be carried by tension rebars and
increasing flexural strength. Since the deformation capacity of the strengthened specimens was
increased by anchoring the CFS and since the maximum strength of the specimens was determined by
detachment or rupture of CFS, the flexural strength of the strengthened specimens could be calculated
from an existing formula. Experimentally determined load-deflection relationships for RC beams
were reproduced accurately through a FEM analysis modeling the bond elements between the
concrete and the CFS. Practical application of the CFS sheeting method to RC beams requires
improvement of the strength of bond between CFS and concrete.
Friction Coefficient in High Tension Bolt Joints Using a Zn/Al Metal Spray Corrosion Resistance Method
Authors: Kim Tae Soo , Lee Han Seung , Tae Sung Ho , Oh Sung Ok
Published: March 2009

In recent years, the friction coefficient decline in the joints of steel structures caused by
corrosion has drawn public attention. Therefore, this study investigated the friction coefficient and
surface roughness of high tension bolt joints using a Zn/Al metal spraying corrosion resistance
method to estimate the application possibility of the Zn/Al metal spraying corrosion resistance
method on the joints of steel structures. According to results, the friction coefficient of Zn/Al metal
spraying was 0.50 or more. In addition, the friction coefficient increased according to the decrease in
surface roughness (Sm/Rz). Therefore, the Zn/Al metal spraying is applicable to a corrosion
resistance method for high tension bolt joints.
A Unified Fatigue Life Calculation Model for Notched Components Based on Elastic-Plastic Fracture Mechanics
Authors: Savaidis G. , Savaidis A. , Hertel O. , Vormwald Michael
Published: March 2009

Based on Dankert’s et al. [1] initial model for the elastic-plastic evaluation of fatigue
crack growth in sheets providing elliptical notches, a generalized procedure enabling an improved
evaluation of the effective ranges of the crack driving force (i.e. the J-Integral) as well as the
application to arbitrary notched components has been developed [2]. The present paper presents the
basic topics of the calculation model as well as its verification using experimental results from
notched specimens with various notch shapes subjected to cyclic loading with various load ratios.
Local and Non-Local Approaches to Fatigue of Weldments: State of the Art and Possible Developments
Authors: Tovo Roberto , Livieri Paolo
Published: March 2009

This paper attempts to critically review some numerical methods for fatigue strength
assessment of welded joints by means of stress analysis tools (usually FE models). In particular, it
focuses on the significance of geometrical model, by distinguishing beams from shells and solids,
more than distinguishing among nominal, structural and notch stress type. In addition, basing on
continuous mechanics theories, a distinction between “local” and “non-local” stress approaches is
proposed. Finally the advantages of notch stress approaches are showed by commenting also
problems connected to multiaxiality and three-dimensionality of stress states.
Predicting Fatigue in Welded Joints: New Theories and some Practical Experience
Authors: Taylor David
Published: March 2009

A few years ago we showed that the Theory of Critical Distances (TCD) and the Crack
Modelling Method (CMM) could be used to predict the behaviour of welded joints of various
geometries, in both steel and aluminum alloys. However we found that there were certain kinds of
joints for which our methods, and also other methods which are commonly used, consistently underpredicted
the fatigue strengths. Some explanations are suggested for this problem. Finally, mention
is made of some of failure investigations in which the author has been involved, to illustrate the
complexities which arise in real-world situations.
On the Influence of the Corner Singularity on Kinking Mixed-Mode Crack Propagation
Authors: Schütte Henning , Molla-Abbasi Kianoush
Published: March 2009

The aim of the presentation is to highlight the influence of the kink, developing at the
beginning of mixed-mode crack growth, on the propagation behavior of the crack. Le et al. [1] have
shown that the variational principle of a body containing a crack results in the principle of
maximum energy release rate incorporating the stress intensity factors of the kinked crack. Here the
influence of the kink and the kinking angle, resulting in a singular field around the corner, on the
crack growth is analyzed. The generalized stress intensity factors at the kinks corner are computed
with the help of a FEM strategy. The influence of these on the T-stresses and the plastic energy
dissipated at the kink is determined using a small scale yielding approach. The impact of these
results on mixed-mode crack propagation is discussed.
Variation of Ultimate Concrete Strain at RC Columns Subjected to Axial Loads with Bi-Directional Eccentricities
Authors: Yoo S.H. , Shin S.W.
Published: March 2009

The distribution of stress in a nonrectangular compressed area, such as a section under a
biaxial moment, is different than that of a rectangular compressed area. The properties of the
compressive stress distribution of concrete have only a minor effect on the pure bending moment
capacity of reinforced concrete beams, but they are important influencing factors for columns
subjected to a combined axial load and a biaxial bending moment. The variation of ultimate strain
of concrete according to the angle and depth of a neutral axis was investigated. Thus, the modified
rectangular stress block (MRSB) model for nonrectangular compressed areas is formulated and
compared to the experimental results and the existing RSB model. The MRSB method is able to
provide more accurate predictions of test results for the biaxial bending moment strength than the
RSB method.
Finite Element Analysis of a Polymer- Polymer Sliding Contact for Schallamach Wave and Wear
Authors: Ashraf Muhammad Azeem , Sobhi-Najafabadi Bijan , Göl Özdemir , Sugumar D.
Published: March 2009

Sliding polymer-polymer surface contacts, due to their inherent elastic properties, exhibit
detachment waves also termed as Schallamach waves. Such waves effect the initiation and
propagation of wear along the sliding contacts. This paper presents quasi steady-state analysis of
such a sliding contact using finite element. The contact is modeled and nodal solutions for pressure
are obtained for small sliding steps. Analysis of orthogonal pressure components at the contact
nodes reveals the formation of Schallamach wave phenomenon. Further, appropriate wear law is
used for calculation of wear at nodal level.
Fatigue Life Analysis of Al 8090 Helicopter Fuselage Panels
Authors: Giglio Marco , Manes Andrea , Fossati Massimo
Published: March 2009

Considering the aerospace structures, the advantages of Al-Li alloys in comparison with
conventional aluminium alloys comprise relatively low densities, high elastic modulus, excellent
fatigue and toughness properties, and superior fatigue crack growth resistance. Unfortunately, these
alloys have some disadvantages due to highly anisotropic mechanical properties and due to a very
high crack growth rate for microstructurally short cracks. This could mean relatively early cracking
in high stress regions such as rivet holes in helicopter fuselage panels. Consequently a more
accurate approach in fatigue life analysis is requested. Considering that the 8090 T81 aluminium
alloy has been widely used in an helicopter structure, in particular in the bolted connection between
the stringers and the modular joint frame in the rear of the fuselage, it is extremely important to
found a reliable procedure for the fatigue life assessment of the component. Thus, using the results
of experimental tests made on panel specimens, a FE general model and two submodels of the
critical zone (involved in fatigue damage during the tests) have been modelled in order to
investigate the complex state of stress near the rivets holes. These stress values obtained have been
elaborated for a fatigue assessment.
Experimental Study of Interior Slab-Column Connections Subjected to Vertical Shear and Cyclic Moment Transfer
Authors: Choi Myung Shin , Cho In Jung , Han Byum Seok , Ahn Jong Mun , Shin S.W.
Published: March 2009

An experimental investigation was conducted to study the seismic behavior of slabcolumn
connections under vertical shear and cyclic lateral load. Test variables include gravity shear
ratio (V /V0 g ) and flexural reinforcement ratio (ρ ) of slab within an effective slab width between
lines that are one and one-half slab thickness ( c 3h 2 + ). The strength and ductility of the test
specimens were evaluated in accordance with gravity shear ratios and slab reinforcement ratios. The
shear strength of the test slabs was compared with the predictions by ACI 318-05.
Fracture Moment Strength of Reduced Beam Section with Bolted Web Connections
Authors: Moon Ki Hoon , Han Sang Whan , Jung Ji Eun
Published: March 2009

Reduced Beam Section (RBS) moment connections are developed for Special Moment
Resisting Frames (SMRF). According to the beam web attachment the column flange RBS
connections are classified into Reduced Beam Section with Bolted web connections (RBS-B), and
the Reduced Beam Section with Welded web connections (RBS-W). Beam flanges are welded to
the column. Regardless of different web attachment details in RBS-B and RBS-W connections
current design procedures (FEMA 350) assumes that they could develop plastic moment of the
beam gross section. In current design procedures, RBS-B connections should provide the sufficient
strength that can reach the plastic moment capacity of the connected beam. However, some
experimental researches reported that the beams in RBS-B connections fractured before the
connection reached its plastic moment capacity. Such undesirable fracture shows that RBS-B
connections have less strength than RBS-W connections. And if RBS-B connections designed in
current design procedures, it might fail in a brittle manner and not satisfy SMRF due to undesirable
fracture. Thus, this study develops a new set of equations for accurately computing the moment
strength of RBS-B connections. The proposed strength equation accurately predicts connection
moment capacity for RBS-B connections.
Deterioration of Concrete Due to Combined Reaction of Carbonation and Chloride Penetration: Experimental Study
Authors: Yoon In Seok
Published: March 2009

In most studies, deterioration of concrete due to carbonation or chloride penetration is
investigated separately. However, the deterioration of concrete is normally caused by the
combination. The purpose of this study is to investigate the interaction between carbonation and
chloride penetration and their effects on concrete. This was examined experimentally under various
boundary conditions. For concrete under the double condition, the risk of deterioration due to
carbonation was not severe. However, it was found that the carbonation of concrete could
significantly accelerate chloride penetration. As a result, chloride penetration in combination with
carbonation can cause harmful deterioration of concrete.
Interface Crack in Anisotropic Solids under Impact Loading
Authors: Wünsche Michael , Zhang Chuan Zeng , Sladek Jan , Sladek Vladimir , Hirose Sohichi
Published: March 2009

In this paper, transient dynamic crack analysis in two-dimensional, layered, anisotropic
and linear elastic solids is presented. For this purpose, a time-domain boundary element method
(BEM) is developed. The homogeneous and anisotropic layers are modeled by the multi-domain
BEM formulation. Time-domain elastodynamic fundamental solutions for linear elastic and
anisotropic solids are applied in the present BEM. The spatial discretization of the boundary integral
equations is performed by a Galerkin-method while a collocation method is implemented for the
temporal discretization of the arising convolution integrals. An explicit time-stepping scheme is
developed to compute the discrete boundary data and the crack-opening-displacements (CODs). To
show the effects of the material anisotropy and the dynamic loading on the dynamic stress intensity
factors, numerical examples are presented and discussed.
Comparison of Seismic Behaviors of Interior Joints in PT and RC Flat Plate Systems
Authors: Park Young Mi , Han Sang Whan , Ryu Jong Hyuk
Published: March 2009

The purpose of this study is to compare the seismic behaviors of interior post-tensioned
(PT) and reinforced concrete (RC) flat plate slab-column connections designed to resist only gravity
loads. In general, flat plate systems have been used to support gravity loads, which should be
constructed with lateral system such as shear walls or moment frames. Flat plate systems should
retain the ability to undergo the lateral drift associated with the lateral system without loss of
gravity load carrying capacity. Although these systems are common, relatively little experimental
study has been conducted to assess actual behavior under lateral loads. Therefore, this study was
undertaken to assess the seismic performance of two PT and one RC slab-column interior
connection under high gravity loads. This study observed that PT connections had a better seismic
performance than corresponding RC connections in terms strength, deformability, energy
absorption.
A Modified Technique for FEM Stress Analysis in Practical Problem
Authors: Ushijima Kuniharu , Nisitani Hironobu
Published: March 2009

Finite element method (FEM) is used widely for various structural problems. However, in
general, it is difficult to guarantee the accuracy of results obtained by commercial software of FEM. In
this paper, a practical finite element technique for calculating the stress concentration factors with
high accuracy is proposed in consideration of physical meaning of stress concentration, and applied to
a 2-dimentional stress problem.