bluuebunny/crossref_metadata_2025 huggingface dataset:
Damage Tolerance Evaluation of Cracked Tubular Joints Subjected to Fatigue Loading
Authors: Murthy A. Rama Chandra , Palani G.S. , Iyer Nagesh R.
Published: November 2010

This paper presents methodologies for damage tolerance evaluation of tubular T- and Y-joints by using linear elastic fracture mechanics (LEFM) principles. The damage tolerance evaluation is in terms of crack growth analysis and remaining life prediction of tubular joints. Stress intensity factor (SIF) for T-butt plates which can be used for computation of SIF for tubular joints has been evaluated as per BS: 7910. It is observed from the literature that the expressions given in BS: 7910 for computation of SIF have not been used for remaining life prediction of tubular joints. In this paper, these expressions have been used for analytical prediction of remaining life of tubular T- and Y- joints subjected to constant amplitude loading (CAL) and variable amplitude loading (VAL). Wheeler residual stress model has been employed to represent the retardation effects due to tensile overloads. It is observed that remaining life predicted for T- and Y-joints under CAL are found to be in good agreement with those of experimental values reported in the literature. In the case of VAL, it is observed that crack growth retardation increases with increase of OLR resulting in higher predicted remaining life. It has also been observed that the predicted remaining life is influenced by the number of OLs and occurrence of OL. Early occurrence of OL causes the higher remaining life compared to later OLs.
Correlation Analysis of Evaluation Indexes for Freeze-Thaw Damage of Lightweight Aggregate Concrete
Authors: Mao Ji Ze , Liu Zong Min , Ayuta Koichi , Yin Wan Jie
Published: November 2010

Freeze-thaw damage is one of the most representative damages in concrete durability. In this
study, rapid freezing and thawing tests were conducted to investigate the freeze-thaw resistance and
analyze the correlation of the evaluation indexes of lightweight aggregate concrete with different
water-cement ratios. The high correlation was confirmed between the length change and relative
dynamic modulus of elasticity of lightweight aggregate concrete. The relative dynamic modulus of
elasticity decreased with the increase of concrete length. However, the correlation was different
according to the water-cement ratio values of lightweight aggregate concrete. The higher water-cement
ratios, the lower expansion values of lightweight aggregate concrete when the relative dynamic modulus
of elasticity decreased to the same degree under freezing and thawing action.
Fracture and Damage Mechanism of RC Pile Group Foundation under Low Reversed Cyclic Loading
Authors: Zhou Mi , Zhang Yue , Yuan Wan Cheng
Published: November 2010

This document explains and demonstrates experimental activity on 4 scale-models of elevated pile cap foundation belonging to a long span continuous bridge. The foundation was composed of 9 piles, pile cap and pier and the special soil box was built to consider soil-pile-superstructure interaction. According to the test result, the development rule of the failure mode, the failure form, the load-displacement hysteretic loops and the plastic hinges mechanism etc. for specimens were summarized. Moreover, the energy dissipation capacity and the viscous damping ratio were gained. The test also provided the data to quantitatively assessment the positive effect of steel protective pipe for RC pile. Fiber beam-column finite element model considering the modified Park-Ang damage index was built in OpenSees. This damage model was proposed to consider the loading path, the pronounced pinching effect of concrete and bond-slip of the reinforcing bars in the paper. In calculation strength degradation and stiffness degradation effects were both embodied. The skeleton curves of test and numerical analysis are both consistent by comparing.
Influence of Steel Fibre Reinforcement on the Shear Resistance and Crack Pattern Formation of Self-Compacting Concrete Beams
Authors: Helincks Peter , de Corte Wouter , Boel Veerle , de Schutter Geert
Published: November 2010

This paper presents the results of experimental tests carried out on steel fibre reinforced self-compacting concrete (SFR-SCC) beams without stirrups. Sixteen beams are cast using four mixtures of SCC with different steel fibre content, while the longitudinal reinforcement is kept constant in all test members. The beams are subjected to four point bending tests at a shear span-to-depth ratio of 2. The ultimate shear stress is recorded, as well as the crack pattern and the mid-span beam deflection. Test results show that as fibre content increases, higher ultimate shear stresses are achieved. When fibres are included, test members exhibit an increase in ductility and a more extensive crack pattern is observed. The experimental values of the ultimate shear stresses are also compared with theoretical values as given by empirical expressions in literature.
Interaction of Multiple Circular Inclusions and a Linear Crack by SH-Wave
Authors: Li Hong Liang , Li Hong
Published: November 2010

Multiple circular inclusions exists widely in natural media, engineering materials and modern municipal construction, and defects are usually found around the inclusions. When composite material with multiple circular inclusions and a crack is impacted by dynamic load, the scattering field will be produced. The problem of scattering of SH waves by multiple circular inclusions and a linear crack is one of the important and interesting questions in mechanical engineering and civil engineering for the latest decade. It is hard to obtain analytic solutions except for several simple conditions. In this paper, the method of Green’s function is used to investigate the problem of dynamic stress concentration of multiple circular inclusions and a linear crack for incident SH wave. The train of thoughts for this problem is that: Firstly, a Green’s function is constructed for the problem, which is a fundamental solution of displacement field for an elastic space possessing multiple circular inclusions while bearing out-of-plane harmonic line source force at any point: Secondly, in terms of the solution of SH-wave’s scattering by an elastic space with multiple circular inclusions, anti-plane stresses which are the same in quantity but opposite in direction to those mentioned before, are loaded at the region where the crack is in existent actually; Finally, the expressions of the displacement and stress are given when multiple circular inclusions and a linear crack exist at the same time. Then, by using the expression, an example is provided to show the effect of multiple circular inclusions and crack on the dynamic stress concentration.
Electrostatic Tractions at Crack Faces Taking into Account Full Piezoelectric Field Coupling
Authors: Ricoeur Andreas
Published: November 2010

Cracks in piezoelectric solids have been subject to fracture mechanical investigations for more than 30 years. In the early years of research, boundary conditions at crack faces have been adopted from pure mechanical systems assuming traction free boundaries. From the electrostatic point of view, cracks have been assumed to be either free of surface charge or fully permeable. Later, limited permeable crack boundary conditions have become popular among the community, however still assuming traction-free crack faces. Recently, the theoretical framework has been extended including electrostatically induced mechanical tractions into crack models yielding a significant crack closure effect. However, these models are still simple neglecting e.g. piezoelectric field coupling. As one consequence, the tractions do not depend on the direction of the electric field with respect to the direction of material polarization. Here, an extended model is presented, entirely accounting for the piezoelectric coupling effect. In this case, the crack closure effect depends on the electric field direction. Additionally, the model yields a new shear effect.
Heat Transfer Analysis for FGMs Using SPH-CSPM
Authors: Rong Gui Ming , Kisu Hiroyuki
Published: November 2010

The solution of heat transfer problems for functional graded materials (FGMs) by smoothed
particle hydrodynamics, in which the thermal conductivity is a function of the spatial coordinates
and the temperature, is discussed for both steady and non-steady problems under various boundary
conditions. The boundary is treated using the corrective smoothed particle method to heighten the
accuracy. Several calculations are performed to test the validity of the formulation. As an example of
practical application, the problem of FGM cylindrical plates subjected to thermal shock is calculated,
in which the thermal conductivity is temperature dependent and the heat transfer coefficient is varied
in radial direction.
3-Dimensional Finite Element Analysis of a Vibrating Bellows with a Large Diameter
Authors: Kim Jae Hyun , Kim Jung Yup , Jang Bong Kyun , Kim Kyung Shik , Choi Byung Ik , Jun Sang Hyun , Kim Jun Ho
Published: November 2010

In this study, we propose a simplification scheme for modeling a complex bellows structure. Using 3-dimensional finite element analysis, vibration modes and natural frequencies are analyzed. The analysis results are compared with those measured by telemetry system of acceleration. It is found that bending mode of vibration can be activated even a low operation frequency and this leads to uneven distribution of stress. The uneven distribution of stress can be a possible cause for the early failure of a bellows with a large diameter.
3D Lattice Fracture Model: Theory and Computer Implementation
Authors: Qian Z. , Schlangen Erik , Ye Guang , van Breugel Klaas
Published: November 2010

The lattice fracture model is presented in this paper, which is intended to simulate the fracture processes in multiphase materials to obtain the mechanical behavior in terms of load-displacement diagram and the cracks propagation. The basic procedures of lattice fracture analysis is that imposing a prescribed displacement on a lattice structure, finding the critical lattice element with the highest stress/strength ratio, removing it from the system and repeating until the system fails globally. One of the challenges in computer implementation of 3D lattice fracture model is the huge demand for computer memory. Matrix free technique is adopted to solve this problem.
Study on Spalling of Extremely Heated FRC by Free Hexagons
Authors: Prochazka Petr P. , Valek Martin V. , Peskova Sarka
Published: November 2010

Fiber reinforced concrete (FRC) exposed to extremely elevated temperature is of great concern in tunnel structures, for example. In the paper a study on spalling on the face of FRC block being subjected to fire of 12000C in duration of 2 hours is to be presented from both theoretical and experimental views. The experiments have been conducted in a furnace its dimensions are to be specified in the paper and the theoretical considerations start with a discrete element method based on free hexagons. The latter method assumes a “soft contact” between hexagonal particles, i.e. springs simulate either tensile and shear contacts in the normal concrete or FRC, where fibers over-bridge possible cracks appearing during cooling process after removing the source of fire. Since the experimental blocks are loaded only by change of temperature and no other type of loading is considered (volume weight of the block is neglected), the “soft contact” is fully sufficient to describe the mechanical behavior of the material. The results from numerical procedure and experimental are compared and the mechanical properties of the material are tuned accordingly.
Variation of Structural Capacity of Reinforced Concrete Slab Due to the Repeated Cyclic Loading Idealized for Thermal Load
Authors: Seo Soo Yeon , Yoon Seung Joe , Yoon Hyun Do
Published: November 2010

A variation of temperature by sunlight acting on a RC roof slab causes a change of stress in concrete since it expands during summer and is compressed during winter. This behavior repeats annually and affects structural capacity of member for both serviceability and ultimate level. In this paper, a variation of cyclic temperature loading is calculated by analyzing the weather data of Korea for 20 years. In addition, an experimental work is planned to find the long term effect of temperature change. Four RC slabs are made with same dimension. Test parameters are loading duration (10, 20, 30 years).
Observation of stiffness variations according to cyclic loading duration shows that the serious stiffness drop happens after 10 year's cyclic loading at summer while after 30 year's loading at winter. From the failure test, maximum strength of specimen that experienced repeated preloading was approximately 12% less than standard specimen without any repeated preloading.
Component-Wise Meshing Approach and Evaluation of Bonding Strategy on the Interface of Components for Assembled Finite Element Analysis of Structures
Authors: Yamada Tomonori , Kushida Noriyuki , Araya Fumimasa , Nishida Akemi , Nakajima Norihiro
Published: November 2010

The finite elements are extensively utilized to solve various problems in engineering fields with the growth of computing technologies. However, there is a lack of methodology for analyses of huge assembled structures. The mechanics on the interface of each components, for instance, contact, bolt joint and welding in assembly is a key issue for important huge structure such as nuclear power plants. On the other hand, it is well known that as finite element models become large and complex, construction of detailed mesh becomes a bottleneck in the CAE procedures. To solve these problems, the authors would like to introduce component-wise meshing approach and bonding strategy on the interface of components. In order to assemble component-wise meshes, the penalty method is introduced not only to constrain the displacements, but also to introduce classical spring connection on the joint interface, although penalty method is claimed that it is not suitable for iterative solver. In this paper, the convergence performance of an iterative solver with penalty method is investigated and the detailed component-wise distributed computation scheme is described with numerical examples.
Relaxation of Stress Concentration of a Crack by Stop Drilling Holes and Additional Holes and Its Practical Prediction
Authors: Miyazaki Tatsujiro
Published: November 2010

It is well known that a stress concentration of a crack can be relaxed by drilling a hole at the crack
tip. The repair method is called a stop drilling procedure and often used to repair aircrafts, machines and so on.
Then, when two additional holes are drilled near the stop drilling hole so as to face each other symmetrically,
the stress concentration of the stop drilling hole can be relaxed further, and a fatigue life is extended. However,
the size and the location of the additional hole suitable for repairing the fatigue damage are not clarified yet. In
this paper, finite element simulations were performed on various plates containing the small center crack at
which the stop drilling holes and the additional holes were drilled, and influences of the additional hole on the
relaxation effect of the stress concentration of the stop drilling hole were investigated. Then, the size and the
location of such additional hole that the stress concentration of the stop drilling hole is minimized were
examined.
Shear Response of Three-Dimensional Micro-Lattice Structures
Authors: Ushijima Kuniharu , Cantwell Wesley J. , Chen Dai Heng
Published: November 2010

In this paper, the shear response of three-dimensional micro-lattice structures was investigated based on numerical stress analysis, FEM. The mechanical properties strongly depend on the number of unit cell in three directions x,y,z, and for a flat structure (number of cells in y-direction Ny=1), the deformation pattern observed in the structure can be classified into two types. The shear modulus G*for a flat structure obtained by FEM can be estimated by the elementary beam theory with a good accuracy. Also, for a flat structure with slender struts, the collapse is occurred by elastic buckling, and that with relatively thicker struts, the collapse strength agrees well with the theoretical result. Moreover, for the case of the cubic structure, if the structure has the same number of unit cell in x- and z- directions (numbers of cells in two directions Nx=Nz=M), the shear modulus G* shows a unit curve regardless of the number M, so that the modulus can be estimated by using the curve for various cubic structures.
Evaluation of Fundamental UHPC Properties According to the Shape of Steel Fiber
Authors: Ryu Gum Sung , Kang Su Tae , Park Jung Jun , Koh Kyung Taek , Kim Sung Wook
Published: November 2010

This paper intends to examine the effects if the length and shape of steel fibers on the mechanical characteristics of ultra-high performance concrete (UHPC). Accordingly, the length (l) of the steel fibers with diameter (d) of 0.2 mm is varied as 13 mm, 16.3 mm and 19.5 mm and their corresponding aspect ratios (l/d) are 65, 82 and 98. Straight and wave-shaped fibers are adopted to manufacture UHPC. Thereafter, the effects of the aspect ratio and characteristics of the wave-shape of the steel fibers on the strength characteristics of UHPC are examined through compressive and flexural strength tests. The results showed small differences in the workability and compressive behavior but revealed that changing the length of the fibers and increasing the aspect ratio are improving the flexural behavior of UHPC. Specifically, the flexural strength was enhanced by 25% and the flexural toughness by 30%. Compared to rectilinear fibers, the adoption of wave-shaped fibers is seen to degrade the flexural behavior regardless of the aspect ratio. Consequently, using straight steel fibers and adopting larger aspect ratio seems advisable to improve the toughness of UHPC.
Mechanical Characteristics Analysis of Alkali-Activated Fly Ash Cementitious Materials
Authors: Ryu Gum Sung , Kang Hyun Jin , Kang Su Tae , Koh Gyung Taek , Lee Jang Hwa
Published: November 2010

Recently, research on alkali-activated concrete that does not use cement as binder has been actively conducted. This alkali-activated concrete is a cement zero concrete which, instead of cement, is activated by alkali solution using fly ash known to be rich of Si and Al and enables to reduce effectively the emission of CO2 gas. This paper presents a basic study for the manufacture of cementless concrete using 100% of fly ash. To that goal, the mechanical characteristics of cementless concrete is evaluated according to the age and the variation of the molar concentration of the alkali activator with focus on the identification of the reaction mechanism. The experimental results show that larger molar concentration elutes larger quantities of Si4+ and Al3+. Specifically, approximately twice larger quantities of Si4+ and Al3+ were eluted for molar concentrations of 9M and 12M than 6M. The formation of gel at the surface of fly ash appeared to be caused by the stronger activation of fly ash in higher alkali environment. The resulting compressive strengths per age indicated that the strength of concrete could be controlled according to the molar concentration of NaOH. Moreover, results also demonstrated that a molar concentration of 9M for NaOH seems to be appropriate to secure a strength superior to 40MPa as the reference for high strength concrete in ordinary concrete.
The Influence of Chemical Admixtures on the Autogenous Shrinkage Ultra-High Performance Concrete
Authors: Park Jung Jun , Kim Sung Wook , Ryu Gum Sung , Lee Kwang Myung
Published: November 2010

Ultra-high performance concrete (UHPC) is a material developing remarkable performance with compressive strength of about 200 MPa and flexural strength of approximately 30 MPa on which research is actively conducted today. However, UHPC is also characterized by a mixing composed of a high specific quantity of binder that is a W/B ratio of about 0.2, which requires to examine the effects of the autogenous shrinkage. Accordingly, this study investigates the effects of the use of expansive additive and water reducing agent on the autogenous shrinkage of UHPC at early age. To that goal, autogenous shrinkage test and ultrasonic pulse velocity (UPV) monitoring are conducted for a mixing of UHPC using expansive additive and shrinkage reducing agent. The experimental results reveal that the autogenous shrinkage of UHPC reduces by 24% for a mix of UHPC adopting both 7.5% of expansive additive and 1% of shrinkage reducing agent compared to the mix without admixture. Furthermore, this mix is seen to compensate the autogenous shrinkage occurring at early age when UHPC develops its largest stiffness in view of the UPV evolution curve. At that time, the shrinkage stress seems to be extremely softened.
Computer Modelling of Crack Propagation in Porous Reactor Core Graphite
Authors: Schlangen Erik , Flewitt Peter E.J. , Smith Gillian E. , Crocker A.G. , Hodgkins Andrew
Published: November 2010

This study aims to develop computer models, with a microstructure representative of the PGA graphite, to contribute to the understanding of the relationship between the amount of porosity, the load-displacement behaviour and crack propagation. The project is in two linked parts, the first provides a model of the porous graphite which is then introduced into a lattice type finite element model to provide the load-displacement and crack propagation predictions. Microstructures consisting of matrix and pores with added aligned filler particles, typical of needle coke, were studied. The purpose was to isolate the effect of filler particles on fracture strength and the fracture path. In the paper crack paths and fracture mechanisms are discussed for different amounts of porosity and various filler particle arrangements.
Study on Spins and Deformation Rate of Solid Circular Shafts at Finite Torsion Deformation
Authors: Yang Li Hong , Zou Guang Ping , Zhang Xue Yi
Published: November 2010

Torsion experiments should be adopted to characterize large strain elasto-plastic behavior of material instead of traditional uni-axial tension experiments due to the plastic stability of specimen in torsion deformation. Study on spins and deformation rate in finite torsion deformation is the key to determine the material parameters by torsion experiments and understand the finite deformation characteristics of material. In this paper, five spins and deformation rate in torsion deformation with solid circular shafts are investigated in cylinder coordinates. The expressions of the deformation rate and spins, namely the material spin, the relative spin, the spin of the frame of the deformation rate, logarithmic spin and instantaneous spin considering the effect of stress, are deduced by analyzing the finite torsion deformation. The comparisons are made among all spins obtained in this paper. The results obtained in this paper are the basis of analyzing the large strain constitutive relationship based on torsion experiments with solid circular shafts.
Optimum Mixture Design of Bottom Ash Based Alkali-Activated Mortar Using Artificial Neural Networks
Authors: Kang Su Tae , Kang Hyun Jin , Ryu Gum Sung , Koh Gyung Taek , Lee Jang Hwa
Published: November 2010

Bottom ash based alkali-activated mortar is prepared by incorporating sodium hydroxide and sodium silicate with some additional water if needed, and is activated with temperature curing. This research was conducted to derive an optimum mixture design of the bottom ash based alkali-activated mortar. The experimental studies were first performed to estimate the effect of the added water content, alkali activator to bottom ash ratio, sodium silicate to sodium hydroxide ratio as well as curing temperature on workability and strength. In order to optimize the mix proportion, based on the experimental results, artificial neural networks were introduced.
Relationship between Microscopic Structures and Compressive Strength of Alkali-Activated Fly Ash Mortar
Authors: Kang Hyun Jin , Ryu Gum Sung , Koh Gyung Taek , Kang Su Tae , Park Jung Jun
Published: November 2010

This paper evaluates the relationship between the compressive strength and microscopic structure of geopolymer mortar using 100% of fly ash instead of cement. The experimental variable is the curing temperature, which may influence the compressive strength of the geopolymer. The compressive strength, porosity, XRD, SEM and EDS are examined after 48 hours of curing at 30, 60 and 90°C. The resulting compressive strength at 60°C appeared to be the largest. In order to evaluate the voids produced during the polymerization, the porosity was measured and showed also the largest value after curing at 60°C during 48 hours. Furthermore, SEM and EDS analyses verified clear improvement of the microstructure after 48 hours of curing at 60°C. Such result can be explained by the variation of the Si-Al ratio according to the curing conditions, which revealed to be lower for curing at 30 and 90°C than at 60°C and demonstrated that the curing temperature has significantly effect on the compressive strength of the geopolymer.
Investigation of Surface Crack Types under Axial Compression Loading for a Case-Hardening Steel
Authors: Klocke Fritz , Timmer A. , Schongen F.
Published: November 2010

During cold-forming operations the formability of the materials can be reached due to the low process temperature, leading to crack initiation. For the investigated case-hardening steel 16MnCrS5 longitudinal cracks and shear cracks are identified as the main crack types. The evolution of both crack types is determined by scanning electron microscope (SEM)-investigations and a simplified finite element method (FEM)-model. The results reveal that the initiation point of shear cracks is located at the surface. In contrast thereto longitudinal cracks emanate from second phase particles in the rim zone.
Effect of Humidity on Fatigue Strength of Age-Hardened Al Alloy under Rotating Bending
Authors: Kawagoishi Norio , Kariya K. , Nu Yan , Furumoto S. , Kondo Eiji
Published: November 2010

In order to investigate the effect of humidity on fatigue strength of an extruded and age-hardened Al alloy 7075-T6, rotating bending fatigue tests were carried out using plain specimens in environments of controlled relative humidity of 25%, 50%, 75% and 85% and distilled water. The cross section of the alloy has a marked texture of (111) plane. Although fatigue strength was decreased by high humidity, the decrease by high humidity was very small when the humidity was lower than about 60% -70% and fatigue strength was largely decreased over the humidity. Both of initiation and propagation of a crack were accelerated by high humidity. In high humidity, a crack propagated in a shear mode macroscopically and it was ductile in company with many glide planes and voids microscopically. That is, the propagation was not a tensile mode with brittle facets even in water. The shear mode propagation inclined about 35° to the extruded direction and fracture surface was (100) plane, meaning that the shear mode propagation of a crack was mainly caused by the marked texture of the alloy. The propagation mode of a crack was affected by not only environment but also stress level.
Nonlinear Propagation of Amplitude-Modulated Ultrasonic Wave in Composite Material
Authors: Biwa Shiro , Nagae Kazuyoshi , Inserra Claude , Matsumoto Eiji
Published: November 2010

Some nonlinear effects in the ultrasonic wave propagation in a unidirectional carbon/carbon (C/C) composite were examined experimentally. High-power amplitude-modulated longitudinal ultrasonic waves were sent to the C/C composite sample, and the nonlinear generation of low-frequency components was observed. Due to the heterogeneity and pre-existing damage of the composite, the carrier-wave component undergoes severe attenuation, and the low-frequency components were dominant in some situations. Such low-frequency components are found to grow in a nonlinear manner, and can be a useful source of information characterizing the nonlinearity of the material.
Stereophotogrametric Determination of Crack Initiation and Propagation in Tooth Root
Authors: Aberšek Boris , Gubeljak Nenad , Predan Jožef , Flašker Jože
Published: November 2010

For designing machines and devices the dimensioning with respect to service life is increasingly taken into account. This applies also for gearing which are still today one of very important components of almost all machines. The problem of determination of the service life of gearing is directly related to geometry of gears, multiaxial loadings, materials and appropriate models for prediction of the crack propagation.Obviously gears and gearing belong to the real complex structure, by correctly selected and carefully planned experiments we obtained results with which we can confirm and justified the mathematical model for calculating different parameters, i.e. service life.
Retrofitting Effect of Unreinforced Masonry Walls Using FRPs
Authors: Bae B.I. , Park B.K. , Choi Hyun Ki , Choi Chang Sik
Published: November 2010

Unreinforced masonry buildings have significant portion of existing and historical buildings around the world. Recent earthquakes have shown the needs of seismic retrofitting for these types of buildings. There are many types of retrofitting materials for URM(unreinforced masonry buildings) such as shotcrete, ECC and FRPs. Many engineers use many types of fiber reinforced polymers because these types of material enhance the shear strength of wall without expansion of wall sectional area and additional weight of total structure. However, the complexity of mechanical behavior of masonry shear wall and the lack of experimental data of masonry wall which was retrofitted by FRPs may cause the problem that engineers hard to determine the retrofitting level. Determining and providing the information for retrofitting effect of FRPs for masonry shear wall, this paper investigate in-plane shear behavior of URM and retrofitted masonry shear walls using two types of different FRP materials. Specimens were designed to idealize the wall of low rise apartment which was built in 1970s Korea with no seismic reinforcements and have 1 aspect ratio. Retrofitting materials were carbon FRP and Hybrid sheet which have different elastic modulus and ultimate strain. Consequently, this study will evaluate the structural capacity of masonry shear wall and retrofitting effect of FRP sheet for in plane shear behavior comparing with evaluation method for reinforced concrete beam which was retrofitted by FRPs.
Wedge-Splitting Test – Determination of Minimal Starting Notch Length for Various Cement Based Composites Part I: Cohesive Crack Modelling
Authors: Veselý Václav , Řoutil Ladislav , Seitl Stanislav
Published: November 2010

The geometric proportions of cube-shaped specimens subjected to wedge-splitting tests are numerically studied in the paper. The minimal notch length for specimens made of cement based composites varying in characteristic length of the material (a measure of material brittle-ness/heterogeneity) is verified using finite element method code with an implemented cohesive crack model (ATENA). The problem of assigning the crack initiation point (the notch tip vs. the groove corner in the load-imposing area of the specimen) is solved numerically also using both the theory of linear elastic fracture mechanics and the theory of the fracture mechanics of generalized singular stress concentrators in the second part of the two-part paper. Results ob-tained by the different approaches are compared. The minimal notch length is recommended.
Flexural Capacities of One-Way Hollow Slab with Donut Type Hollow Sphere
Authors: Kim Byoung Hoon , Chung Joo Hong , Choi Hyun Ki , Lee Seung Chang , Choi Chang Sik
Published: November 2010

This paper presents the flexural capacities of one-way hollow slab with donut type hollow sphere. Recently, various types of slab systems which can reduce self-weight of slabs have been studied as the height and width of building structures rapidly increase. A biaxial hollow slab system is widely known as one of the effective slab system which can reduce self-weight of slab. A biaxial hollow slab has hollow spheres within slabs in order to reduce self-weight of slabs. The capacities of biaxial hollow slab are influenced by the shapes, volume and materials of hollow spheres. According to analytical studies, the hollow slab with donut type hollow sphere had good flexural capacities such as strength, stiffness and deflection. To verify the flexural capacities of this hollow slab, flexural tests were performed on the one-way hollow slabs. Five test specimens were used for test parameters. One was conventional RC slab and others were hollow slabs. The test parameters included two different shapes and materials of plastic balls. The shape parameters were donut and non-donut forms. And the material parameters were general plastic and glass fiber plastic.
Punching Shear Strength of Biaxial Hollow Slab with Donut Type Hollow Sphere
Authors: Chung Joo Hong , Choi Hyun Ki , Lee Seung Chang , Choi Chang Sik
Published: November 2010

This paper presents the punching shear capacities of biaxial hollow slab with donut type hollow sphere. Recently, various types of slab systems which can reduce self-weight of slabs have been studied as the height and width of building structures rapidly increase. A biaxial hollow slab system is widely known as one of the effective slab system which can reduce self-weight of slab. According to previous studies, the hollow slab has weakness in slab-column connection. In addition, the present code does not provide a clear computation method for the punching shear strength of hollow slab. In this study, the special type of cage was used to improve punching shear capacities and fix the hollow spheres in critical section. To verify the punching shear capacities of this biaxial hollow slab, punching shear tests were performed. Four test specimens were used for test parameters. One was conventional RC slab and three were hollow slabs. The test parameter was the areas of critical section which were determined by the number of hollow spheres in critical section.
Experimental Study on Behavior of Flexural Member with Lab-Spliced GFRP Bar
Authors: Choi Yun Cheul , Choi Hyun Ki , Choi Chang Sik
Published: November 2010

The use of glass-fiber-reinforced polymer (GFRP) bars to replace steel reinforcement in concrete structures is a relatively new technique. GFRP bars possess mechanical properties different from steel bars, including high tensile strength combined with low elastic modulus and elastic brittle stress–strain relationship. Therefore, design procedures should account for these properties. This paper presents the experimental moment deflection relations of GFRP reinforced beam which are spliced. Test variables were lab-spliced length of GFRP rebar. A total of 6 concrete beams reinforced with steel and GFRP rebar tested. Three concrete beams reinforced with spliced GFRP rebar and 1 reference beams reinforced with non-spliced GFRP rebar was tested. All the specimens had a span of 4000mm, provided with 12.7mm nominal diameter steel and GFRP rebar. All test specimens were tested under 2-point loads so that the spliced region is subject to constant moment. The experimental results show that the splice length of GFRP increased with the ultimate load increasing and decreased with stiffness.
Variational Principle of Carbon Nanotubes with Temperature Changes Based on Nonlocal Euler-Bernoulli Beam Model
Authors: Fan Tao
Published: November 2010

In this paper, the CNTS are considered as the Euler-Bernoulli beams which have been used in many references about the CNTS. Taken the thermal-mechanical coupling and small scale effect into account, the variational principle for the CNTS is presented by the variational integral method. With the derivation of the varitional principle, the vibration governing equation is illustrated, which will be benefit for the numerical simulation with finite element method in further investigations. From the stationary value conditions deduced by the variational principle, the influences of the temperature changes and the thermal expansion coefficients based on nonlocal Euler-Bernoulli beam model are presented.
Fatigue Life Prediction Strategies for High-Heat-Load Components
Authors: Xiao W.L. , Chen H.B. , Jin J.F.
Published: November 2010

High-heat-load components such as photon shutters and masks made of Glidcop Al-15 are subjected to intense thermal cycles from the X-ray beams at the third generation light sources. This paper presents thermal fatigue life prediction results of high-heat-load components at the beam line front end of Shanghai Synchrotron Radiation Facility (SSRF) under different power conditions. Used in this analysis are four typical multiaxial fatigue life prediction models, i.e. the maximum principal strain model, equivalent vonMises strain model, maximum shear strain model and critical plane approach. Detailed comparisons among them were implemented from various aspects including applicable conditions, physical meanings and resultant veracities. Critical plane approach was finally determined to be more appropriate method for dealing with multiaxial fatigue of high-heat-load components. To obtain the multiaxial stress-strain fields, nonlinear finite element analysis (FEA) was performed with commercial software ANSYS.
Mechanical Approach for Predicting Fretting Fatigue Strength
Authors: Jayaprakash M. , Mutoh Yoshiharu , Asai K. , Ichikawa Kunihiro , Sakurai Shigeo
Published: November 2010

Stress distribution at the contact edge is known to have a dominant influence on fretting fatigue strength. Stresses acting on the contact surface are tangential stress and compressive stress. In the present study, fretting fatigue strengths of 12 Cr steel specimen under two different mean stresses have been predicted based on the generalized tangential stress range - compressive stress range diagram. The generalized tangential stress range - compressive stress range diagram was obtained by carrying out fretting fatigue tests and finite element analysis using various steel specimens with various geometries of contact pad from the previous studies. The predicted fretting fatigue strengths were in good agreement with the experimental results.
Understanding and Modeling of Stress Corrosion Cracking (SCC)
Authors: Choi Byoung Ho , Chudnovsky Alexander
Published: November 2010

Stress corrosion cracking (SCC) is a brittle fracture of a ductile material under severe environment. Due to the complexity of mechano-chemical degradation during SCC formation, the scientific community is still far from the complete understanding of this phenomenon. Moreover, it is commonly misunderstood that polymeric materials is ‘SCC-free’, but it should be noticed that SCC is universal phenomenon for all engineering materials including polymers. In this paper, the similarity and differences of SCC in different materials, such as carbon steels and engineering polymers, are observed and reported. The SCC modeling in carbon steels and engineering polymers is also compared and discussed.
Study on Fatigue Traffic Loading for Highway Bridges in China
Authors: Yue F. , Ren X.S. , Chen M. , Miao Y.Y. , Li M.Y. , Hao Z.G.
Published: November 2010

This paper is focused on developing fatigue-load model for highway bridges based on the measurements data of WIM (Weigh-in-Motion) in China. In this paper, based on the analysis of vehicle flow data collected from six toll stations on Jing-Fu Highway which is one of the busiest highways in China, spring festival index and month index of vehicle flow are obtained. The finite element models are established, and the vehicle flows are modelled by using Monte Carlo method as dynamic load applied on the nodes of the models. This paper presents a fatigue truck model for Jing-Fu Highway bridges, which may also be used for other highway bridges in China. In order to validate the model, strain time histories were obtained through field strain measurements for 3 existing bridges on this highway. In addition, comparison among the model introduced in this paper and the models in foreign codes as well as the models developed by other researchers is presented.
Measurement of Crystal Grain Size of Austenitic Stainless Steels under Low-Cycle Fatigue by EBSD Techniques
Authors: Mori Takayuki , Yamada Teruaki , Kuroda Masatoshi , Kamaya Masayuki
Published: November 2010

Electron backscatter diffraction (EBSD) in conjunction with scanning electron microscopy was used to assess the fatigue damage induced in stainless steels. The parameter of the crystal grain size was devised in order to evaluate the fatigue damage in terms of the crystal grain size. It was concluded that the fatigue damage could be evaluated by the EBSD measurements using the relationship between the total strain range, the number of cycles and the crystal grain size.
Wedge-Splitting Test – Determination of Minimal Starting Notch Length for Various Cement Based Composites Part II: Crack and Notch Fracture Mechanics Approaches
Authors: Seitl Stanislav , Klusák Jan , Veselý Václav , Řoutil Ladislav
Published: November 2010

The paper focuses on the geometrical proportions of cube-shaped quasi-brittle specimens subjected to a wedge-splitting test (WST). The minimal/optimal initial crack/notch length for successful performance of WST on these specimens is studied numerically (ANSYS). This second part of the paper treats the problem asymptotically, i.e. from the point of view of a very fine grained silicate composite material with negligible characteristic length which describes the level of the material brittleness (i.e. brittle). The problem of competition of the crack initiation point between the notch tip and the groove corner in the load-imposing area of the specimen is solved using theories of both linear elastic fracture mechanics and fracture mechanics of generalized singular stress concentrators. The numerically obtained crack/notch length is compared to results of numerical simulations using cohesive crack model reported in the first part of the paper. The minimal notch length is recommended.
Preliminary Finite Element Analysis of Shot Peening for Austenitic Stainless Steels
Authors: Yamada Teruaki , Kuroda Masatoshi , Mori Kazuya
Published: November 2010

In this study, the preliminary finite element analysis of shot peening was carried out in order to investigate the fundamental mechanism of shot peening for stainless steels. For numerical simulations with high-rate deformation such as shot peening, rate-dependence plasticity models are necessary to get better analysis results. Therefore the stress-strain relation at high-strain rates of austenitic stainless steels were obtained by split Hopkinson pressure bar (SHPB) tests. The parameters of Johnson-Cook plasticity model were determined from the result, and then the finite element analysis of shot peening was carried out using the parameters. Consequently, the compressive residual stress was created beneath the surface of the target but was changed to the tensile residual stress with an increase in the depth.
Research on the Propagation Pattern of 3-D Initial Crack in Rock-Like Material under Uniaxial Tension
Authors: Yang L. , Jiang Y. , Li Shu Cai , Li B.
Published: November 2010

Experiments and numerical simulations were conducted to investigate the propagation patterns of pre-existing 3-D elliptical crack in rock-like material under uniaxial tension. Research results demonstrated that as the load was increased, the wrapping wing cracks initiated near the front of long axis of crack, with the lateral growth of initial crack close to the front of short axis. A distortion surface formed from the growth of initial crack leaded to the macro fracture of samples. The distribution laws of mixed-mode stress intensity factor (SIF) along crack contour were derived with FRANC3D, and propagation process of 3-D crack under tension was simulated. It was concluded that propagation patterns of 3-D crack under tension were quite different from compressive cases, mainly in aspects of growth orientation and velocity.
Modelling of Cyclic Plasticity and Crack Propagation
Authors: Čanžar Predrag , Tonković Zdenko , Kodvanj Janos , Bakić Ante , Tomičević Z.
Published: November 2010

An experimental and numerical study of the cyclic deformation and low-cycle fatigue behaviour of the aluminium alloy AlCu5BiPb–T8 is presented. The experimental program included monotonic tensile tests, symmetric and unsymmetric strain-controlled fatigue tests, fracture toughness tests, as well as fatigue crack initiation and propagation tests. Within the framework of numerical investigations an efficient algorithm for modelling of cyclic plasticity is proposed. This algorithm is implemented into the finite element program ABAQUS and applied to the analysis of a crack growth near the notch. The accuracy of the computational procedure is tested by comparing the computed results with the real experimental data.
Mechanical Property Enhancement for Al Based Metal Matrix Composites
Authors: Humphries Sam R. , Wuhrer Richard , Booth N.G. , Yeung Wing Yiu , Ouyang Qiu Bao , Qin J. , Zhang D.
Published: November 2010

An enhanced nucleation heat treatment process was employed to refine the grain structure of 7075Al/ 7wt.% SiCp metal matrix composite material. The grain structure of the metal matrix composite was investigated. The resulting microstructures were compared. It was found that a fine grained microstructure developed after the rapid heat treatment process. An increase in hardness was achieved, with hardness increasing from 129 HV in the cold extruded state to 137 – 153 HV after the heat treatment process.
Acoustic Monitoring of Hydraulic Fracture Propagation in Pre-Fractured Natural Rocks
Authors: Meng C. , De Pater C.J.
Published: November 2010

Active acoustic monitoring can capture two types of fracture behavior in rock samples, opening and closure of an existing fracture and tip movement of a propagating fracture. The first type is related to wave transmission across the fracture interface. The second one is related to the travel times of waves that diffract at the fracture tip. A series of experiment has been conducted with an acoustic system that has transducers mounted on the loading frames of a tri-axial cell situated in the Rock Mechanics Laboratory, TUDelft, the Netherlands. The existing fractures are formed by cleaving the rock samples into layers and putting them back together. The propagating fractures were created by hydraulic fracturing via bore-hole injection. The tests in this study featured both cleaved and hydraulic fractures, and aimed to characterize the interaction between them. This paper focus on the data processing that is adapted to these special tests and comparison between the monitored and recovered fractures.