bluuebunny/crossref_metadata_2025 huggingface dataset:
Real-Time Geometric Error Compensation in Micro Grooving the Workpiece with Large Surface Area
Authors: Kang D.B. , Son S.M. , Ahn J.H.
Published: March 2009

A workpiece with a large surface area is likely to be uneven due to form error and waviness.
These geometric disturbances can cause inaccurate micro shapes to be formed when micro features
are micro-grooved into the surface and cause the resulting workpiece to fail to function as desired.
Thus, the real-time monitoring and compensation is required to guarantee the form accuracy of micro
features while machining the workpiece with a large surface area. In this study, a method is suggested
for real-time measurement and compensation of geometric errors for the micro grooving of a large
flat surface using a laser displacement sensor placed ahead of the cutting tool. Experimental results
show that the compensated surface profiles fit the measured ones within an allowable tolerance even
at cutting speeds as high as 200 mm/s.
A Vacuum-Compatible Air Bearing: Design Analysis and Optimization
Authors: Khim G.H. , Park Chun Hong , Lee H.S. , Kim S.W.
Published: March 2009

This paper describes the vacuum-compatible air bearing designed with a cascaded exhaust scheme to minimize the leakage of air in a vacuum environment. The design of the air bearing, including the differential exhaust system, required great care because several design parameters, such as the number of exhaust stages, diameter and length of the exhaust tube, pumping speed and ultimate pressure of the vacuum pump, and seal length and gap greatly influenced the leakage of air and thus the degree of vacuum. A leakage analysis was performed to estimate the chamber pressure and an optimization method based on the genetic algorithm was proposed under several constraint conditions. The results showed that the degree of vacuum improved dramatically compared to the initial design, and that the distribution of the spatial design parameters and technical limit of the pumping speed were well achieved.
Theoretical Research on Aerostatic Rectangular Guideways with Finite Difference Method
Authors: Zhang Xiao Feng , Lin Bin
Published: March 2009

The load capacity and stiffness of the aerostatic rectangular guideways, which apply annular orifice restrictor and porous restrictor respectively, were analyzed with finite difference method in this paper. A program for solving the pressure distribution, load capacity and stiffness is programmed with VB. The calculated results show that the rise of supply pressure is good for improving the load capacity and stiffness of guideways. The decrease of the orifice diameter in annular orifice restriction and the permeability in porous restriction is advantageous to improve the stiffness of guideways, but both the corresponding bearing clearance and load capacity decrease. In both the annular restriction and porous restriction, the best film thickness which make the stiffness maximum exists under the definite supply pressure and parameter of the restrictor. Under the same supply pressure, the load capacity and stiffness of porous restriction is higher than the orifice restriction. Meanwhile, the design and manufacture of porous restrictor is simple. The porous restrictor is the perfect restrictor of aerostatic guideways.
Influence of Magnetic Field Distribution on ECM Process
Authors: Ma Bao Ji , Fan Zhi Jian , Stephenson D.J.
Published: March 2009

Based on the concept of the interaction between a magnetic and electric field, a magnetic field was suppressed on the Electrochemical Machining (ECM) setup to improve the copying accuracy of ECM. Mathematical modeling and finite element modeling of the magnetic field was also developed using ANSYS to study the influence of permanent magnet design on the ECM process. The results indicate that by introducing the magnetic field the threshold of electrochemical reaction is decreased and the tracks of ions become complicated which makes the chemical reaction more extensive and more uniform in the inter-electrode gap. The distribution of magnetic field in the gap helps to improve the machining accuracy and the process efficiency, when the permanent magnet is at the end of the electrodes. Experiments have been carried out to validate the results of finite element analysis and the effect of a magnetic field on the ECM process is discussed.
Numerical Evaluation of Micro- to Macroscopic Mechanical Behavior of Plastic Foam
Authors: Riku Isamu , Mimura Koji
Published: March 2009

In this study, we employ the two-dimensional homogenization model based on molecular
chain network theory to investigate the micro- to macroscopic mechanical behavior of plastic foam
under macroscopic uniform compression. A parametric study is performed to quantify the effect of
a characteristic value of matrix, distribution and initial volume fraction of voids, and the
macroscopic triaxiality of loading condition on the deformation behavior of the foam. The results
suggest that the onset of localized shear band at the ligament between voids together with the
microscopic buckling of the ligament leads to the macroscopic yield of the foam. The initial
modulus and the macroscopic yield stress of the foam have no dependence on the characteristic
value of matrix. Furthermore, as the microscopic buckling of the ligament is promoted in case of
high initial volume fraction of voids and high triaxiality loading condition, the macroscopic yield
point appears at early deformation stage. After the macroscopic yield, macroscopic strain hardening
appears in the macroscopic response and a remarkable strain hardening is shown in case of high
initial volume fraction of voids and high triaxiality loading condition due to the considerable
increase of the density of the foam in these cases.
Metallo-Thermo-Mechanical Simulation of Carburized Quenching Process by Several Codes - A Benchmark Project -
Authors: Inoue Tatsuo , Watanabe Youichi , Okamura Kazuo , Narazaki Michiharu , Shichino Hayato , Ju Dong Ying , Kanamori Hideo , Ichitani Katsumi
Published: March 2009

As one of the activities carried out by our group of IMS-VHT (Virtual Heat Treatment tool
for monitoring and optimising HT process), results of a benchmark project on the simulation of
carburized quenching process is summarized. Several programs available for taking into account the
metallo-thermo-mechanical coupling had been employed for the simulation for a cylinder, ring as
well as a helical gear by use of common data of material properties and cooling characteristics.
Comparison of the simulated values of distortion, residual stresses and profile of induced phases with
the experimental data is made with some discussions.
Experimental Study on Mechanical Property of Steel Reinforced Concrete Short Columns of T-Shaped
Authors: Li Zhe , Zhang Xiao Feng , Zhao Yan Feng , Wang De Fa
Published: March 2009

The horizontal press performance of column is deteriorated because of special-shaped
section. Moreover, because the antiseismic performance of columns is worse, it is only used in
regions where seismic intensity is lower. So the main problem is to enhance the ductility. This test
study on mechanical performance has been carried out through fourteen SRCTSSC and RCTSSC.
The study focuses on the impact of test axial pressure ratio(nt), hooped reinforcement ratio(ρv),
shear span ratio(λ) and steel ratio(ρss) to the shear strength and the antiseismic performance of
SRCTSSC. It can be concluded that the shear strength of SRCTSSC is increasing with the
increasing of nt and ρss , but the degree of increasing is small when nt is a certainty value, and that
the shear strength of SRCTSSC is decreasing with increasing of λ; The shear resistance formula of
T-shaped column is derived through tests, the calculated results are in correspondence with those of
the tests. It also can be concluded that the hysteretic loops of the SRCTSSC are full and the
hysteretic behaviors are improved and that the displacement ductility is increasing with increasing
of ρv and ρss , but decreasing with the increasing of nt and the degree of variety in high axial pressure
ratio is larger than in low axial pressure ratio. If steel bars are added, the shear strength and
displacement ductility of SRCTSSC is increased in a large degree, and the capacity of energy
dissipation is also enhanced. This test, for applying the special-shape column to higher intensity
region, has the certain instructive significance.
Numerical Simulation for Stress-Induced Phase Transformation of SMAs Tube under Tension
Authors: Hu Zhen Dong , Sun Qing Ping , Zhong Zheng
Published: March 2009

Recent uniaxial tension tests have shown that stress-induced phase transformation in
NiTi SMAs tubes can lead to helical-type localized deformation and propagation phenomena. Based
on detailed experimental observation and possible deformation mechanism, a trilinear stress-strain
relationship with intrinsic strain softening is employed to represent the material constitutive
behavior in this paper, and a 3-D finite deformation simulation is performed to model the tube
under tension by using nonlinear FEM. The simulations successfully reproduce the nucleation and
evolution of the helical-type martensite band during stress-induced transformation observed in the
experiments.
Superelastic Deformation Properties of TiNi Shape Memory Alloy
Authors: Pieczyska Elzbieta , Nowacki W.K. , Sakuragi T. , Tobushi Hisaaki
Published: March 2009

The characteristics of energy storage and dissipation in TiNi shape memory alloys were
investigated experimentally based on the superelastic properties under various thermomechanical
loading conditions. The results obtained can be summarized as follows. (1) The recoverable strain
energy increases in proportion to the rise in temperature, but the dissipated work per unit volume
depends slightly on temperature. In the case of low strain rates, the recoverable strain energy and
dissipated work do not depend on both the strain rate and the temperature-controlled condition. (2)
In the case of high strain rates, while the recoverable strain energy decreases and the dissipated
work increases in proportion to the rise in strain rate under the temperature-controlled condition, the
recoverable strain energy increases and the dissipated work decreases under the temperatureuncontrolled
condition.
Influence of Soil Dilatancy on Soil Nail Pull-Out Resistance in Completely Decomposed Granite Fill
Authors: Su Li Jun , Yin Jian Hua , Liao Hong Jian
Published: March 2009

Soil nailing, developed from the New Austrian Tunnelling Method, has been widely used
in many countries and regions in the world since the 1970’s. This technique is used to stabilize in situ
soil mass by installing a large number of closely spaced unstressed inclusions into the soil mass to
increase its strength and stability. Since the mid 1970’s, several design methods have been proposed
based on laboratory and field tests. Among the design criteria in these methods, the pull-out resistance
of a soil nail is a key parameter that controls the stability assessment of soil nail structure. In the
previous investigations, the soil dilatancy was found to be an important factor that influences the soil
nail pull-out resistance especially for drill-and-grout soil nails. In order to study the influence of soil
dilatancy on soil nail pull-out resistance, laboratory pull-out tests and numerical parametric studies
have been carried out for soil nails in Completely Decomposed Granite (CDG) fill. The results show
that the soil dilatancy has a significant influence on the soil nail pull-out resistance.
Elastoplastic Behavior of Particle Reinforced Composites Considering the Effect of Interfacial Debonding
Authors: Ning Jian Guo , Jiang Fang
Published: March 2009

Based on Mori-Tanaka’s concept of average stress in the matrix and Eshelby’s equivalent
inclusions theory, the stress or strain of the matrix, the reinforced particles and the composite are
derived under a prescribed traction boundary conditions. The plastic strains and strains due to
thermal mismatch between matrix and reinforced phase are considered as eigenstrains. The matrix
and composite are postulated isotropic and the matrix satisfies isotropic hardening law. The
interface debonding is decided by the tensile strength of the particles whose debonding probability
is described by Weibull distribution function. Then the overall elastoplastic constitutive relation of
spherical particle-reinforced metal matrix composite is derived by secant modulus method
considering the interface debonding. The theoretical uniaxial stress-strain bebavior of the composite
agrees well with the experimental curves.
Deformation Analysis of Partially Saturated Soil in Slopes
Authors: Zhou Cheng
Published: March 2009

Anisotropic visco-plastic constitutive model and generalized pore pressure are
incorporated in the equation between irreversible downwards velocity and visco-plastic strain rate.
The solution to velocity is obtained and by use of it the progressively destructurated deformation of
partially saturated natural soil in slopes is analyzed to investigate the influence of anisotropy,
viscosity, degrees of structure and destructuration, and partial saturation. The solutions are verified
by use of the observed field behavior of a natural slope.
An Elastoplastic Model for Granular Materials Exhibiting Particle Crushing
Authors: Sun De An , Huang Wen Xiong , Sheng Dai Chao , Yamamoto Haruyuki
Published: March 2009

A practical elastoplastic constitutive model for granular materials is presented. And the
model is suitable for description of the material behaviour for a wide range of stresses, including those
sufficient to cause particle crushing. With a limited number of model parameters, the model can
predict the confining-pressure dependent stress-strain relation and shear strength of granular materials
in three-dimensional stresses, especially of variation of shear strength and dilatancy characteristics
due to particle crushing under high confining pressure. The model parameters, which have clear
physical meanings, can be determined from the results of isotropic compression test and conventional
triaxial compression tests. The model performance is demonstrated for triaxial compression tests of a
sand for a wide range of the confining-pressure from 0.2MPa to 8.0MPa.
Stress Testing of Individual Steel Strands in a Multiple-Cable Single Borehole Anchorage for Geotechnical Engineering
Authors: Li Shao Jun , Feng Xia Ting , Chen Bing Rui
Published: March 2009

Multiple-cable single borehole anchorages are widely used in China, accepted and
regarded as a very effective method for slope protection, landslide remediation and foundation ditch
support. This paper presents a new method for testing tensional stresses of individual steel strands
within anchor cables in single boreholes. A rig has been designed to permit testing of cables within
a single borehole, including two special features: a metal plate that distributes tension between
strands of a cable and a sensing device that measures the stress in each individual strand. The
feasibility of the method has been demonstrated by an in situ tensional stress test on anchor cables
at a landslide remediation site that successfully measured the forces on individual steel strands
fastened to different anchorage segments within a borehole. The steel cable strands displayed nonlinear
extension characteristics; and the length of anchorage segments and grout strength met design
criteria. The results confirm that this design of anchorage is satisfactory and can provide valuable
data for future design and construction.
Nonlinear Analysis of R/C Frame under Static and Cyclic Loadings
Authors: Zhou Lin Cong , Chen Long Zhu
Published: March 2009

This paper proposes a reliable and computationally efficient finite-element model (Partial
Fiber Model) for the nonlinear analysis of reinforced concrete (R/C) frames under static and cyclic
loading conditions that induce multiaxial bending and axial forces. The beam-column member is
composed of three parts: middle elastic and two plastic regions at the two ends of beam. The plastic
regions are discretized into longitudinal steel reinforcement and concrete fiber elements. The
nonlinear behaviors of the elements are derived from the nonlinear stress-strain relations of the steel
and concrete fibers. The global stiffness matrix of beam-column can be deduced from those of
mentioned three parts. Numerical examples are calculated to prove the accuracy and efficiency of
the model. The results of nonlinear analysis show the validity of the model to describe the nonlinear
response of frame subjected to static and cyclic loadings.
Assessing the Flaws in Welded Seam of Header of a 300MW Steam Turbine Generator Unit
Authors: Song Li , Yang Shui Cheng , Wei Feng Tao
Published: March 2009

The flaws such as crack or slag inclusion, in the welded seam of header of a 300MW
steam turbine generator unit, were detected by the ultrasonic non-destructive inspection. Based
on the crack modeling, the finite element method (FEM) was used to calculate and analyze the
displacement field, stress field and stress intensity factors of the cracks under the conditions of
warm start, cold start and normal operation, and the residual service life was predicted.
Analyzing results showed that these flaws would not bring about primary brittle fracture and
propagation of crack was harmless to safe in operation.
Effect of Dimensional Tolerance on Displacements and Stresses of Wedged-Ring Joint Structure
Authors: Zhao Rong Guo , Luo Wen Bo , Chen Zhong Fu , Xu Bin , Yin Yi Hui
Published: March 2009

The effect of geometric clearances on the stress and deformation distributions of a
wedged-ring joint structure is studied, five cases of dimensional tolerance of each contact surface,
i.e., the maximum, minimum, mean of maximum and minimum, mean of maximum and mean, and
mean of minimum and mean are investigated, and the probable states that the wedged-rings attach
with the upper cylinder or attach with the lower cylinder radially in the assembly process are
considered as well. The results of finite element numerical simulations indicate that in the design
tolerance zone, the effects of geometric clearances between contact surfaces on the displacement
and stress distributions of the structural components are weak. Only when the wedged-rings attach
tightly with the upper cylinder or with the lower cylinder, the displacement and stress distributions
in the joint of the structure occur a dramatic variation, and the assembly processing measure making
the wedged-rings attaching tightly with the lower cylinder can be adopted to effectively decrease
the stresses and deformations in the joint of the structure.
A Study on Friction Stir Process of Magnesium Alloy AZ31 Sheet
Authors: Hsu Hung Hsiou , Hwang Yeong Maw
Published: March 2009

Friction stir processes (FSP) are important for enhancing mechanical properties of metal
sheets, such as the tensile strength, the elongation, etc. The stress distribution of the tool pin is
affected by the thermo-mechanical characteristics of the workpiece in FSP. Recently, magnesium
alloy AZ31 is widely used in machine industries due to the light-weight material property. In this
paper, a thermo-mechanical model for FSP using three dimensional FEM analyses is proposed for
exploring temperature distributions, strain distributions and stress distributions of the workpiece. The
heat generated from the plastic deformation and the friction between the head tool and workpiece is
considered as the heat source in the simulation of the FSP process. A commercial finite element code
– DEFORM 3D is used to carry out the simulation of the plastic deformation of AZ31 sheets during
the FSP. The analytical results of temperature, strain and stress distributions of the workpiece and
head tool can provide useful knowledge for tool pin design in FSP
Viscoplastic Behavior of Acrylic Adhesive in Butt-Joint at Various Temperatures under Complex Loading : Experimentation and Modelling
Authors: Yoshida Tetsuya , Oishi Takayuki , Takiguchi Michihiro , Yoshida Fusahito
Published: March 2009

The effects of temperature and strain rate on flow stress of a highly ductile acrylic adhesive
were investigated by performing tensile lap shear experiments on an adhesively bonded single-lap
joint, as well as torsion experiments on a tubular butt-joint at temperatures ranging from 10 to 40oC at
various shear strain rates. The flow stress decreases considerably with decreasing strain rate and with
temperature rise. The stress-strain responses under multi-axial stress conditions were also examined
by performing combined tension-torsion experiments on the butt-joint. A constitutive model of
temperature-dependent elasto-viscoplasticity that describes multi-axial stress-strain behavior of the
adhesive is presented.
Evaluation of the Interfacial Properties in Polymer Matrix Composite: Experiments and Elasto-Plastic Shear-Lag Analysis
Authors: Kimura Souta , Koyanagi Jun , Hama Takayuki , Kawada Hiroyuki
Published: March 2009

An energy-based analysis has been developed to evaluate interfacial adhesion between
fiber and matrix in a single fiber composite over the years. However, the value of the energy-based
parameter, e.g. an energy release rate, depends on a stress distribution predicted by a model
employed. In the case of carbon fiber-reinforced plastics (CFRP), laser Raman spectroscopy (LRS)
is significantly effective to validate the stress distribution predicted. The fragmentation tests with a
model of carbon fiber-reinforced epoxy composite are performed, and LRS is used to detect a
distribution of the fiber axial strain. An elasto-plastic shear-lag analysis methodology is employed,
and a stress distribution is predicted under various approximations of s-s curve of the matrix resin
and compared with the experimental results. Our recent energy-balance method, including an
energy dissipation induced by plastic deformation around an interfacial debonding tip, is used to
calculate an energy release rate to initiate an interfacial debonding (interfacial energy). An effect of
the difference between the approximations on the value of the interfacial energy is discussed.
High Density Bands of GN Dislocations Formed by Multi Body Interaction in Compatible Type Multi Crystal Models
Authors: Kondou Ryouji , Ohashi Tetsuya
Published: March 2009

Slip deformation phenomena in compatible type multi crystal models subjected to
tensile load are analyzed by a finite element crystal plasticity analysis code, and accumulation of
geometrically-necessary and statistically-stored dislocations (GNDs and SSDs) are evaluated in
detail. Crystal orientations for the grains are chosen so that mutual constraint of deformation
through grain boundary planes does not take place. We call these models as compatible type multi
crystals, because “compatibility requirements” at grain boundaries are automatically maintained by
slip deformation only on the primary systems and uniform deformation is expected to occur in each
grain. Results of the analysis, however, show non-uniform deformation with high density of
GNDs accumulated in a form of band. Growth of such kind of structure of GNDs caused localized
accumulation of SSDs at grain boundary triple junctions. Mechanism for the band-shaped
accumulation of GNDs in the compatible type multi crystals are discussed from the viewpoint of
multi body interactions which arise from shape change of crystal grains after slip deformation.
Destructive and Ultrasonic Investigations of Damage Development in Metallic Materials
Authors: Kowalewski Zbigniew L. , Mackiewicz Sławomir , Szelażek Jacek
Published: March 2009

Damage development due to creep under uniaxial tension at elevated temperatures is
assessed using destructive and non-destructive methods in steels, commonly used in power plants or
chemical industry, and in aluminium alloy used in aircrafts for responsible elements. The results
obtained using two different destructive methods for assessments of damage development are
critically discussed. In the first method the specimens of steel after different amounts of creep
prestraining were stretched up to failure and variations of the selected tension parameters were taken
into account for damage identification. In the second one, a damage degree was evaluated by
studying variations of an initial yield locus position in the stress space and by determination of the
yield loci dimensions. The ultrasonic investigations were selected as the non-destructive method for
damage development evaluation.
Three-Dimensional Numerical Manifold Method Based on Hexahedron Element with Full First-Order Cover Function and its Application in Underground Excavation
Authors: Zhang Y.H. , Sheng Qian , Cheng Y.M.
Published: March 2009

In this paper, three-dimensional(3D) Numerical Manifold Method (NNM) based on
hexahedron element cover with full first-order cover function is proposed and the shape function of
C8 isoparametric element in FEM is used as the cover weight function. All sub-matrices in
equilibrium equations, including stiffness matrix, initial stress matrix, point force matrix, surface
force matrix, body force matrix, inertia force matrix, contact matrix and friction matrix, are derived.
Different with 2D contact, the direction of shear stiffness and friction force can not be easily
defined in 3D contact. A new iterative method based on vector theory to detect the contact
direction is developed. The application of 3D NMM in underground excavation is also presented
and show good agreement with real engineering.
Numerical Investigation of Flexural Properties of Sheet Metals Subjected to Embossing and Restoration Process
Authors: Namoco Jr Consorcio S. , Iizuka Takashi , Hatanaka Nobuo , Takakura Norio , Yamaguchi Katsuhiko
Published: March 2009

In this study, numerical simulations of flexural tests of sheet metals subjected to
embossing and restoration process are carried out using LS-DYNA3D. Several models are created
varying the number, position, and pitch of the emboss or restoration points. The emboss height and
sheet thickness are also varied. Results show that improvement in rigidity of sheet metals can be
optimized by taking into considerations several parameters as discussed in this paper.
Influence of Tensile Pre-Strain on the Torsional Fatigue Crack Behaviors of a Structural Steel
Authors: Zhou Cong Ling , Nishida Shinichi , Hattori Nobusuke
Published: March 2009

Structural steel is widely used in engineering even in nowadays and many new materials
have been developed or are under developing. As one of the most common type, torsional fatigue
properties are normally calculated from the rotating bending fatigue properties. In this study, the
torsional fatigue properties of a structural carbon steel (S45C) with different tensile pre-strain ratio
is investigated, especially on the effects of Mode II crack before it branches under different stress
amplitudes. Based on the experimental results and microstructure observation, the main results
obtained are: (1)Torsional fatigue strength is increased after tensile pre-strain deformation, and the
fatigue limits increase with increasing of tensile pre-strain ratio, the highest improvement can be up
to 125% of that of the plain specimen. (2) Torsioanl fatigue cracks initiate from the torsional slip
lines in ferrite grains, and there is no obvious effect by the tensile pre-strain. With increasing of
tensile pre-strain ratio, the fatigue crack initiation life ratio becomes later and the growth rate
becomes faster. (3) The mode II crack length along the axial direction becomes longer with
increasing of tensile pre-strain ratio, and the crack branch direction does not affected by the tensile
pre-strain. Moreover, the length along axial direction is not affected by the stress amplitude change
for specimens with the same tensile pre-strain ratio. (4) The length of non-propagating crack
becomes shorter with increasing of tensile pre-strain ratio.
Evaluation of Fracture Surface of 11/4Cr-1/2Mo Steel by Residual Magnetization Induced from Inverse-Magnetostrictive Effect
Authors: Hase Hiroichi , Kotake Shigeo , Ohota Mitsuhiro , Kawakami Hiroshi , Suzuki Yasuyuki
Published: March 2009

In this study, we propose a new technique to evaluate some properties during fracture
propagation, such as stress at the crack surface and the propagating-route by measuring distributions
of leaked magnetic flux vector from the residual magnetization in the vicinity of the fracture surface.
The technique involves the application of an inverse-magnetostrictive effect in ferromagnetic
materials, such as tempered 11/4Cr-1/2Mo steels below the ductile-brittle transition temperature.
The maximum magnetic flux density was increased with impact absorption energy measured by
Charpy impact test. The highest magnetic flux density located at the crack starting point, where a
fish-eye type surface morphology was observed in fractographic analysis. It indicates the highest
stress for fracture initiation at this point. According to the analysis, the change in the magnetic flux
vectors corresponds with the direction of crack propagation, which was well explained from the
magnetostrictive properties of iron. The measurement of magnetic flux density distribution will be
useful for the fractographic analysis to discuss the in-situ phenomena that are difficult to obtain in
previous methods.
Preform Design for Formability Enhancement of Tube Hydroforming Process Using Deformation History
Authors: Song Woo Jin , Choi Han Ho , Kim Keun Hwan , Park Sung Ho , Kim Jeong , Kang Beom Soo
Published: March 2009

Preform design in tube hydroforming implies the design of an intermediate shape between
initial tube and the final product enabling to be fabricated without defects and excessive loss of
material. A carefully selected preform can contribute significantly to reduce production cost and
improve formability, since thinned sections may not be able to endure internal pressure during
expansion whereas excessive thickening may lead to wrinkles. Generally, preform design in
hydroforming was mainly carried out through the trial-and-error approach. Even though a series of
numerical simulations for several predetermined preformed shapes were conducted, optimum
configuration could not be obtained and could not be suggested the general procedure for preform
design as well. In this work, a simple numerical approach to the preform design for formability
enhancement was introduced based on the deformation history during forward hydroforming
simulation. The proposed approach was implemented to a hydroforming process of an automobile
subframe component in order to be satisfied the required specification after hydroforming, and the
conceptual application has been proved to be successful on its effectiveness and feasibility. Therefore,
it is shown that preform design approach proposed in this study will provide one of feasible methods
to satisfy the increasing practical demands for improvement of the formability in hydroforming
processes.
Computer Aided Simulation of the Rheology Forging Process for Aluminum Alloys and its Experimental Investigation
Authors: Kang C.G. , Seo P.K. , Bae J.W.
Published: March 2009

Rheology forming is a novel processing method of semi-solid processing, which is
different from traditional mold forging and conventional casting process. The rheological behavior of
metallic alloys containing both solid and liquid phases was investigated with the low and high solid
fraction ranges. Its obvious advantages are easier to produce complex work pieces because of
excellent forming ability, more flexible to shape, and more compact in the inner quality for its high
pressure. This research paper presents the theory of the rheology forming process and the results of the
finite element simulation of rheology forming for aluminum alloys. In this proposed theoretical
models for the rheology forming process involve simultaneous calculations performed with solid
phase deformation and the liquid phase flow analysis. To analyze the rheology process, the new flow
stress curves of rheology aluminum alloys and the viscosity for the simulation of two-phase flow
phenomena have been proposed with as a function of temperature.
Deformation Analysis of Co-Extrusion Process of Aluminum Alloy and Copper Alloy
Authors: Jang Dong Hwan , Hwang Beong Bok
Published: March 2009

This paper is concerned with the analysis of plastic deformation of bimetal co-extrusion
process. Extrusion is related to large deformation of material and leads to non-homogeneous
deformation within work-piece material. The mechanism of plastic deformation during the composite
rod extrusion is much more complicated than that in single metal extrusion. Deformation patterns of
co-extrusion of two different materials are characterized by several process parameters. In this paper,
the analysis is focused to investigate the effect of contact conditions along the interface between two
different materials. The rigid-plastic finite element method was applied to the analysis of co-extrusion
process. The selected materials are AA 1100 aluminum alloy as hard material and CDA 110 as soft
one. This type of material selection was to examine the effect of hard core and soft sleeve and vice
versa in terms of deformation pattern. The initial composite billets were prepared by inserting the core
material in tight (0.023mm) and weak (0.012mm) interference bonding, respectively. Four different
cases of co-extrusion process in terms of material combination and interference bonding were
simulated to investigate the effect of material arrangement between core and sleeve, and of bonding
on the plastic zones. It is concluded from the simulation results that the plastic zones in this
co-extrusion process are not influenced much by the selection of material arrangements or bonding
condition between construction materials. However, it was seen from the simulation results that the
extrusion ratio of each construction material, i.e. homogeneity of co-extrusion, depends much on the
material arrangement and the bonding condition.
Deformation Behavior of Dual-Phase LTSP Ti3Al Based Alloy
Authors: Yang K.L. , Huang J.C.
Published: March 2009

Ti3Al based alloys have been widely reported for their admirable superplasticity in the
temperature range of 900-1000oC. However, the superplastic behavior of temperature lower than
900oC was seldom reported. Dual phase (α2+β) Ti3Al-10Nb alloy has shown superior superplastic
elongation of 1500% at 960oC and 2x10-4 s-1. In this paper, it aims to investigate the superplastic
behavior at lower temperature (700-900oC). The relationship of texture characteristics, phase
transformation phenomena, and deformation mechanism at lower temperature (below 900oC) are
studied. The optimum low-temperature superplastic condition with an elongation of 333% was
occurred at 850oC and 5x10-4 s-1. With abundant hexagonal α2’ laths formed inside the β grains, the
major accommodation process via dislocation slip across the β grains is impeded. It leads to
premature failure and lower tensile elongations at lower temperature. Moreover, with the minor
operating of grain rotations and grain boundary sliding, the texture intensity decreases significantly
at temperature 850oC.
The 3D Modeling of Dies Based on UG and Numerical Simulation of the Heat Rheological Forming of Titanium Alloy Vane Disk
Authors: Luo Ying She , Yu Min , Peng Xiang Hua
Published: March 2009

The heat rheological forming of the TC11 titanium alloy vane disk has been studied. The
dies of rheological forming were 3D-modeled based on UG and the heat rheological forming of the
TC11 titanium alloy under a certain temperature and a low strain rate was analyzed by DEFORM 3D
based on variation principle of rigid viscoplastic non-compressed material. A series of results
including rheological forming procedure, equivalent strain field, temperature field and load-stroke
curves of punch and cavity die, were obtained by finite element method. The deformation
characteristic of the TC11 titanium alloy was well known and its heat rheological forming process
and parameters were determined. Moreover, the local underfilled phenomenon in practical
manufacture was predicted and analyzed, and we found that the defects could be restricted by
reducing the forming velocity.
Protection against Slippage between Roll and Material in the Rolling of Lumber
Authors: Kawase Tadahiro , Shiozaki Hiroyuki , Iwauchi Toshitaka
Published: March 2009

During lumber rolling, a fixation
device is typically installed just behind the
work roll to set up the delivery thickness
and to fix the thickness reduction. However,
the accompanying resistance force into the
fixation device can cause slippage between
the roll and material, indicating a bound for
the rolling conditions. Slippage can be
avoided by decreasing the resistance force
or by adding a pushing force on the lumber
from the entry side of the rolling mill. This
paper experimentally investigated the effects of these horizontal forces on the rolling force and roll
torque. From these results, the roll torque was found to be directly affected by the horizontal forces,
but the rolling force was not affected. Secondly, a new parameter μeq was introduced and a condition
of non-slippage, in which μeq must be less than the coefficient of static friction to avoid slippage, was
proposed. This condition was then used to predict and to protect against slippage by identifying when
this condition was violated and then applying a horizontal force to decrease μeq.
Evaluation of Adhesive Properties of Arc PVD Coatings on Non-Nitrided and Nitrided Various Substrates
Authors: Lee Jung Min , Ko Dae Cheol , Kim Byung Min
Published: March 2009

This paper was designed to assess the adhesive properties of hard coatings made by
physical vapor depositions on various substrates (AISI D2, AISI H-13 and M2) with and without an
intermediate nitrided layer. An estimation of adhesion was carried out using the scratch test, where
adhesion is measured by the critical load (Lc). This value was determined as the normal force affecting
the indenter and causing the coating detachment as well as the acoustic emission signal containing the
information on the extent of coating damage. The scratch track after the scratch test was also
examined with an optical microscope to observe the failure modes of each coating. Hard coatings TiN,
CrN and TiAlN were chosen for this study. Results of the test showed that harder substrates and
coatings give higher values of critical loads.
Optimum Design of Forming Sequence of One-Piece Automobile Steel Wheels without Welding Using Finite Element Simulation
Authors: Abe Y. , Watanabe J. , Mori Kenichiro
Published: March 2009

A forming sequence of one-piece automobile steel wheels without welding was designed.
In this forming process, the one-piece wheel was formed from a circular blank only by multi-stage
stamping operations, and a deeply drawn cup was formed into the wheel. Two humps of the rim
flange for fixing the tire were formed in the flaring and flanging stages. The humps of the rim in the
opening and outer side were formed by buckling the inner flange of the rim, and by swelling the outer
flange with an upper die having a short land, respectively. In addition, the number of stages was
considerably reduced from 16 stages to only 9 stages by combining the deep drawing and ironing
stages and by adding a holding die in the flaring stages. The forming sequence of the one-piece wheels
was evaluated by both finite element simulation and miniature experiment.
A Thermodynamically Consistent Eulerian Description of Finite Elastoplasticity
Authors: Bruhns Otto T.
Published: March 2009

Recently it has been demonstrated that the classical Prandtl/Reuss theory based on the
additive split of the deformation rate contrary to what is believed so far is possible to establish a
consistent Eulerian rate formulation for finite elastoplasticity. Here, we attempt to place this Eulerian
formulation on the thermodynamic grounds by extending it to a general case with thermal effects.
Modeling of Large-Strain Cyclic Plasticity for Accurate Springback Simulation
Authors: Yoshida Fusahito , Uemori Takeshi , Abe S.
Published: March 2009

This paper describes a model of large-strain cyclic plasticity and its verification by
some experiments of cyclic plasticity and biaxial stretching. The performance of this model in
springback simulation is discussed by comparing the calculated results for S-rail forming with the
experimental data on high strength steel sheet (HSS) of 980MPa-TS. The results of numerical
simulations of the springback agree well with the corresponding experimental data, including the
torsion-type springback appearing in S-rail forming.
Mechanical Alloying of Ti-Al-Si-C Powders, their Thermal Stability, Phase Evolution, and Synthesis and Deformation of In Situ Produced Titanium Aluminide Composites
Authors: Rao Kamineni Pitcheswara , Vyas A.
Published: March 2009

Addition of silicon promotes the development of a stable phase Ti5Si3 through thermomechanical
treatment in TiAl-based alloys develop, while carbon seems to be a promising element
for generating both solid solution effect and dispersion strengthening by precipitation of TiC or
Ti2AlC during subsequent processing of such alloys. In this study, elemental powder mixture of
58Ti-30Al-6Si-6C (at%) was selected to find the structural changes during mechanical alloying
(MA) process in order to understand the mechanism of alloying as well as study the subsequent
thermal stability and evolution of phases. The results obtained would be useful towards in situ
synthesis of titanium aluminide composites that are targeted to serve applications involving high
tempearture. Such route will enable precipitation of harder Ti5Si3 and TiC particles within a matrix
of TiAl through hot isostatic pressing (HIP).
Firstly, MA of the chosen powder mix was performed up to 40 hours. The structural evolution
of MA powders and/or annealed powders was characterized by X-ray diffraction (XRD). The
stability of milled powders was investigated by differential scanning calorimetry (DSC) to study the
phase transformations. Then, 10% of MA powder or the so called ‘precursor’ was incorporated into
Ti-45Al-2Cr-4Nb-1.5Mn (at%) baseline matrix or baseline elemental powder, and was packed into
stainless steel tubes after thorough blending. The sealed tubes were subjected to HIPing under a
pressure of 150 MPa at 1100°C for 4 hours, followed by furnace cooling to room temperature.
After HIPing, the resulted composites were annealed at 1150°C for 4 hours. The composites were
evaluated for their mechanical properties and deformability at room and elevated temperatures. The
results indicate that the synthesized composites have indicated extensive workability at a
temperature of 800 oC as well as good mechanical proporties up to this temperature.
Plasticity in the Mechanical Behaviour of Cardiovascular Stents during Stent Preparation (Crimping) and Placement (Expansion)
Authors: De Beule Matthieu , Mortier Peter , Van Impe Rudy , Verhegghe Benedict , Segers Patrick , Verdonck Pascal
Published: March 2009

In Western countries, cardiovascular disease is the most common cause of death, often
related to atherosclerosis which can lead to a narrowing of the arteries. To restore perfusion of
downstream tissues, an intravascular stent (i.e. a small tube-like structure) can be deployed in the
obstructed vessel. The vast majority of stents are balloon expandable and crimped on a folded
balloon to obtain a low profile for deliverability and lesion access. Several studies have exploited
the finite element method to gain insight in their mechanical behaviour or to study the vascular
reaction to stent deployment. However, to date – to the best of our knowledge – none of them
include the balloon itself in its actual folded shape. Furthermore, literature on the effect of the
crimping process on the expansion behaviour of the stent is even scarcer. Our numerical results -
accounting for the presence of the balloon in its actual folded shape - correspond very well with data
provided by the manufacturer and consequently our approach could be the basis for new realistic
computational models of angioplasty procedures. The plastic deformation, prior to the stent
expansion and induced by the crimping procedure, has a minor influence on the overall expansion
behaviour of the stent but nevertheless influences the maximum von Mises stress and nominal
strain. The maximum von Mises stress drops from 440 N/mm² to 426 N/mm² and the maximum
nominal strain value lowers from 0.23 to 0.22 at the end of the expansion phase when neglecting the
presence of the residual stresses. Depending on the context in which to use the developed
mathematical models, the crimping phase can be discarded from the simulations in order to speed
up the analyses.
Plastic Flow Joining by Shot Peening
Authors: Harada Yasunori , Fukaura Kenzo
Published: March 2009

In this study, plastic flow joining using a shot peening process was investigated. Surface
treatment is necessary to improve the surface properties. Shot peening is one of the surface
treatments. Since the surface of substrate is hit repeatedly with a large number of shots, the substrate
undergoes a large plastic deformation near its surface. Therefore, plastic flow characterized by a
shear droop occurs at the edge of the substrate due to shot peening. If an implant made of a dissimilar
material is set in a hollow space on the surface of the substrate and then shot-peened, it can be joined
to the substrate due to the peening droop generated by the large plastic deformation during shot
peening. In this method, the availability of the plastic flow, i.e., the peening droop makes the joining
of the implant possible. In the experiment, a compressed-air-type shot peening machine was
employed. To examine experimentally the influence of working temperature on bondability,
equipment with a heating furnace was produced. The influence of processing conditions on the
joining of the implant and the substrate was examined. The joint strength increased with the kinetic
energy of shots and processing temperature. The improved implant with a step was effective in
improving in bondability. The dissimilar material was also successfully joined to a thin sheet by using
of the interaction of peening droops. It was found that the present method using the peening droop
was effective for joining the dissimilar materials.
Thermal Imprint Process of Parylene for MEMS Applications
Authors: Youn Sung Won , Goto Hiroshi , Takahashi Masaharu , Ogiwara M. , Maeda Ryutaro
Published: March 2009

This study investigated a thermal imprint technique to pattern parylene microstructures
over an area of 2525 mm2. A nickel mold having arrays of 25 m-high, 10 m-wide and 1 mm-long
lines with 10 m spacing was fabricated using the deep RIE silicon etching followed by the
electroplating process. Imprint tests were then carried out under different conditions of temperature,
imprint-hold time and applied pressure to investigate a thermal imprint condition for the complete
filling of parylene. Good release results without damage or deformation in parylene microstructures
were achieved by the help of a release agent in the imprint temperature range of 160 oC to 250oC. With
increasing temperature, the depths of imprinted structures increased and their distribution came to be
homogeneous. Complete filling was obtained under the imprint temperature of 250oC, applied load of
195 kgf (3 MPa) and imprint hold time of 1800 s.