bluuebunny/crossref_metadata_2025 huggingface dataset:
Assessment of Indentation Fracture Toughness Based on a Direct Measurement of Crack-Driving Residual Stress
Authors: Lee Yun Hee , Takashima Kazuki , Higo Yakichi , Kwon Dong Il
Published: March 2009

A direct measurement of the crack-driving stress has been attempted by applying a
nanoindentation-combined, stress-probing technique to the expected crack routes ahead of a Vickers impression. The nanoindentation curves close to the remnant indent were compared to those of an unstressed bare sample and were interpreted into quantitative stress values. In detail, from the difference of two stress distributions measured from uncracked and cracked indentation corners, the driving stress for the radial cracking was estimated; a rapid decaying response with a distance to the Vickers indent center with the peak value 406.7MPa. The fracture toughness of soda-lime glass, estimated by taking into account the results measured in this study was 0.74 ± 0.15 2 / 1 m MPa × and was comparable with that of the literature.
Experimental Study on the Mechanical Properties of Satin Carbon Fabric/Epoxy Composites
Authors: Liu J.C. , Wang Tie Jun , Zhang W.
Published: March 2009

Effect of resin content on the mechanical properties of satin carbon fabric/epoxy composites is studied in this paper. Mechanical properties of the satin carbon fabric/epoxy composites are experimentally measured. The compressive strength and conversion ratio of strength of carbon fiber in the fabric composites are measured and compared with the experimental data of composite laminates reinforced by unidirectional fiber tape.
The Influence of Residual Stresses by Shot Peening on Fatigue Strength of the Automobile's Coil Spring
Authors: Bae Dong Ho , Lee Gyu Young , Jung Won Seok , Park S.C. , Jung Won Wook
Published: March 2009

Durability assessment for the suspension system of the vehicle is very important.
Particularly, corrosion fatigue strength of coil spring depends on many factors including mechanical and environmental properties. In this paper, residual stresses by multiple shot peening were analyzed using finite element analysis, and evaluated its effect on corrosion fatigue strength. And also, a corrosion fatigue design criterion for coil spring of light commercial vehicle (LCV) based on proving ground response was proposed.
Evaluation on Small Punch Creep Test by Finite Element Method
Authors: Zhai Peng Cheng , Chen Gang , Hashida Toshiyuki , Zhang Qing Jie
Published: March 2009

The Small Punch Creep Tests (SP-C tests) are simulated by a Finite Element Method (FEM). The objective of the present study is to establish a foundation for the SP-C test method by investigating the deformation and stress state of the SP-C test specimen. The emphasis is placed on the dependence relation of the creep strain and the stress on the measurable quantities, such as applied loads and the central deflections. Simulation works are conducted for two different materials, one is
the tungsten-alloyed 9% Cr ferritic steel and the other is 12Cr1MoV steel. The numerical results for the central deflection versus time curves are quantitatively similar to the experimental results obtained on tungsten-alloyed 9% Cr ferritic steels. From the numerical results, the relationship between the central deflection and the equivalent creep strain is approximately independent of load, temperature, and material properties. The magnitude of the equivalent stress in the central region of
the SP-C specimen shows no significant change with respect to time at the secondary creep stage, an approximate equation is proposed for the assessment of the equivalent stress in the SP-C specimen. As a farther result, the high temperature creep properties of the 12Cr1MoV steel and tungsten-alloyed 9% Cr ferritic steel are appraised by numerical simulation. The results are in good agreement with the results from the standard test method. The results indicate that the small punch test technique is an effective method for the evaluation of the high-temperature creep properties of materials.
Evaluation of Creep-Fatigue Life Using Backscattering of Rayleigh Surface Wave
Authors: Lim Byeong Soo , Kim Bum Joon , Song Sung Jin , Kim Young H.
Published: March 2009

The application of nondestructive evaluation to creep-fatigue damage was examined in this paper. Generally, as the hold time of static load increases, the degradation of material becomes more rapid and the creep-fatigue life decreases. Therefore, in the evaluation of creep-fatigue strength and life of high-pressure vessel such as main steam pipe at high temperature is very important in power plants. In this study, the creep-fatigue behavior of P92 steel was evaluated nondestructively by the backscattered ultrasound using the creep-fatigue specimens. The results obtained by Rayleigh surface wave of backscattered ultrasound were compared and analyzed with the experimental parameters. Also, the relation between the SDA (slope of degraded area) and creep-fatigue life was examined. From the result of nondestructive test, we suggest that SDA would be used as the new parameter for
the evaluation of creep-fatigue damage. As the degradation increased, the SDA decreased and also the creep-fatigue life decreased.
The Evaluation of Tensile Properties at High Temperatures Using a Ring Specimen
Authors: Seok Chang Sung , Bae Bong Kook , Koo Jae Mean , Park Jae Sil , Huh Yong
Published: March 2009

In the case of inner pressurized pipe, the hoop stress mainly causes the failure of pipe. For evaluating the hoop tensile properties of pipes, a ring test is used although it has an inevitable shortcoming of disturbance by the bending. Arsene suggested a central piece-inserted ring test for reducing the bending. At high temperatures, the friction between the specimen and the central piece exerts a serious influence on the results, so an effect on friction should be considered in the analysis. In this study, for the evaluation of the hoop properties using the central piece-inserted ring model of Arsene, we performed the ring tensile tests at several temperatures. From the ring tensile tests and numerical analysis the load-displacement conversion relationship of ring specimen (LCRR) was determined. We could obtain the hoop tensile properties by means of applying the LCRR to the results of the ring tensile test. From the result, it was observed that the strength decreased as the temperature increased, and the elongation dropped a little around 400°C.
Effect of Thickness on Grain Growth in Electrodeposited Copper Film by Cyclic Stressing
Authors: Iino Y.
Published: March 2009

Effect of thickness on grain growth in Copper electrodeposits by cyclic stressing was studied by metallographic observation. The thickness of the film was 1µm to 20µm and the number of stress cycles was 3 × 106. Recrystallization by annealing in the films was also examined for comparison. The results show that the nucleation of the grains by cyclic stressing decreases significantly with decreasing thickness, while the grain growth rate is almost independent of thickness. The recrystallized grain size by annealing decreases with decreasing film thickness and is always smaller than the film thickness. The difference in the structural change by cyclic stressing and by annealing is discussed. When the crystal growth caused by cyclic stressing is used as a strain analysis method, the optimum thickness of the deposits is about 10µm.
Effects of Microstructure on Material Behaviors of Solder Alloys
Authors: Hwang Tae Kyung , Lee Soon Bok
Published: March 2009

The leading candidates for replacing lead-contained solders are near ternary eutectic Sn/Ag/Cu alloys. The electronic industry has begun to study both the process behavior and the reliability assessment of these alloys in detail to figure out their applicability to electronic devices and products. In recent publications, the solidification behavior and the fatigue life of the accelerated thermal cycle test have been reported in terms of microstructure variations such as the formation of large Ag3Sn plates and their effects. In this study, coupon type bulk specimens have been made for uniaxial tensile test by casting. To consider the effects of microstructure, casting cooling rates were controlled to 0.02-2.0 oC/sec. Eutectic Sn/Pb and near eutectic lead-free solder materials – Sn/Ag/Cu and Sn/Cu alloys – were used in mechanical testing. Also, nanoindentation tests were performed to
measure Young’s modulus of materials having different microstructures. Tensile tests were performed at 3 different strain rates and then acquired 0.2% offset proof stress, ultimate tensile strength and elongation to failure.
Fabrication of Bi-Te Based Thermoelectric Semiconductors by Using Hybrid Powders
Authors: Lim Cheol Ho , Kim Ki Tae , Kim Yong Hwan , Cho Dong Choul , Lee Young Sup , Lee C.H.
Published: March 2009

P-type Bi0.5Sb1.5Te3 compounds doped with 3wt% Te were fabricated by spark plasma sintering and their mechanical and thermoelectric properties were investigated. The sintered compounds with the bending strength of more than 50MPa and the figure-of-merit 2.9×10-3/K were obtained by controlling the mixing ratio of large powders (PL) and small powders (PS). Compared with the conventionally prepared single crystal thermoelectric materials, the bending strength was increased up to more than three times and the figure-of-merit Z was similar those of single crystals. It is expected that the mechanical properties could be improved by using hybrid powders without degradation of thermoelectric properties.
Development of Small Punch Test for EAC Evaluation
Authors: Isselin Jerome , Wang Sheng Chun , Komazaki Shinichi , Shoji Tetsuo
Published: March 2009

We are developing a Small-Punch SCC testing apparatus with an in-situ observation
system applied to high temperature water and high pressure. This new testing apparatus is used to evaluate the Environmentally Assisted Cracking effect. A constant loading rate was carried out with different values of speed, of water flow rate and different polishing of the sample. In BWR (Boiling Water Reactor) conditions (9MPa and 288°C) it was found that the loading rate, water flow rate and surface preparation of the sample have some influence if the test is performed during a short time (maximum 4 days). After the test, by SEM observation, studying the secondary microcracks, it is possible to find all the sequences of EAC process. The in-situ observation system permits to study the strain of the sample during the test.
Effect of Grain Boundary Microchemistry on IGSCC of Alloy 132 in a Simulated BWR Environment
Authors: Takeda Yo-ichi , Yamauchi Hiroyuki , Peng Qunjia , Shoji Tetsuo
Published: March 2009

The effects of cold working and heat treatment on caustic stress corrosion cracking (SCC) of mill annealed (MA) alloy 800M in boiling solution of 50%NaOH+0.3%SiO2+0.3%Na2S2O3 were investigated by means of microstructure examination, tensile test, X-ray stress analysis, SCC testing of C-rings, Auger electron spectroscopy (AES), scanning electron microscopy (SEM) and metallography.
The microstructure of alloy 800M under tested conditions was austenite. With a strain of 25% by cold working, the grains of alloy 800M became longer, yield strength (YS) and ultimate tensile strength (UTS) increased, elongation (δ ) decreased, residual stress and the susceptibility to SCC increased. With increasing temperature of heat treatment of alloy 800M with cold working, the grains became bigger , residual stress, YS and UTS decreased and δ increased, the susceptibility to SCC of alloy 800M decreased. In boiling caustic solution, SCC cracks on the surfaces of C-ring specimens polarized potentiostatically at –20mV/SCE initiated from pitting and propagated along grain boundaries. AES analysis indicated that the surface films on MA alloy 800M were enriched in nickel and depleted in iron and chromium.
Synthesis and Luminescence Properties of Chalcopyrite-Type CuAlS2
Authors: Kuroki Yuichiro , Okamoto Tomoichiro , Takata Masasuke
Published: March 2009

Copper aluminum disulfide (CuAlS2) powders were synthesized in an evacuated ampoule at elevated temperatures. X-ray diffraction analysis revealed that the powders heated at temperatures higher than 800oC were single-phase CuAlS2. In the cathodoluminescence (CL) spectra measured at room temperature, the powders heated at temperatures higher than 600oC exhibited a visible emission peak at approximately 1.8 eV and a distinct ultraviolet emission peak at 3.45 eV. The powder heated at 700oC showed the maximum intensity of ultraviolet emission which is considered to be associated with excitons.
Processing and Electrical Properties of KNbO3 Ferroelectric Dense Ceramics Added with Small Amount of Bi2O3 and MnCO3
Authors: Yoshida Takeru , Nagata Hajime , Takenaka Tadashi
Published: March 2009

Doping a small quantity of additive Bi2O3 is effective in suppressing the deliquescence of KNbO3 ceramics. When an optimized ball-milling process was included, dense and nondeliquescent KNbO3 ceramics were obtained by a conventional firing process. However, the presence of Bi prevented grain growth (<0.2 μm) and it was one of the causes of low ferroelectricity. Moreover, the insufficient resistivity made the poling treatment difficult. In order to improve the electric properties, a small quantity of additive MnCO3 was also doped into KNbO3 with 0.5 mass% Bi2O3. Codoping of KNbO3 with MnCO3 and Bi2O3 (abbreviated to KNBixMny; x = 0~1.0, y = 0~1.0 in mass%) improved the ferroelectricity of samples, and it also had an effect on the resistivity and densification of sintered bodies. Well-saturated P-E hysteresis loops were observed with any amount of Mn and the largest remanent polarization Pr was about 16 μC/cm2. The piezoelectric properties of KNBi0.5Mn0.3, which had the highest piezoelectricity in this study, are an electromechanical coupling factor k33 and piezoelectric constant d33 of 0.30 and 101 pC/N, respectively.
Construction Technology of Durable Concrete in Permafrost District
Authors: Du Bing , Yi Quan Xin
Published: March 2009

Aiming at influencing factors in the abominable natural environment in permafrost
district of Qinghai-Tibet railway, according to different requirements on concrete’s durability performance which exerted by different climatic conditions and different environment of Qinghai-Tibet railway, the design and the construction on site of durable concrete was investigated.
Application of Molten Slag Fine Aggregate Concrete Using Superplasticizer
Authors: Otsuka Shuzo , Nakata Yoshihisa , Saito Takeshi , Takahashi Hiroki , Tobinai Keishi , Kemi Torao
Published: March 2009

With increasing number of melting-solidification plants for the domestic wastes and incineration ashes, the resulting molten slag is now expected as a recycled aggregate for concrete in Japan, while application examples until now are limited to non-loadbearing pre-cast concrete and concrete secondary products. This study deals with a full-scale application of molten slag recycled fine aggregate. Starting with the inspection of monthly variations in quality of molten slag fine aggregate in a plant, construction of a full-scale structure was attempted using the recycled aggregate concrete with a superplasticizer. During construction, pumpability of the recycled concrete was examined and the quality of hardened concrete in the structure was evaluated. It was shown that quality variation of the molten slag fine aggregate during eight months was sufficiently small, and pumpability as well as concrete quality in structure showed no significant difference with those of the ordinary concrete.
On Building Crumb Rubber Concrete Test Sites
Authors: Zhu Han
Published: March 2009

Presence of crumb rubber can change the concrete characteristics in a significant way. This article presents some experience of building crumb rubber concrete (CRC) test sites, and the data of on-site measurement with respect to slump and air content of fresh CRC samples.
Influence of Boundary Conditions on Pore Percolation in Model Cement Paste
Authors: Chen Hui Su , Stroeven Piet , Ye Guang , Stroeven Martijn
Published: March 2009

Fresh model cement mixtures, with the same w/c ratio and particle size distribution, were simulated by the SPACE system that is based on a dynamic mixing algorithm. Thereupon, they were hydrated by the HYMOSTRUC 3D system. Boundary conditions were varied, rendering possible assessment of their influence on percolation of capillary porosity by serial sectioning and using the overlap of slices. Simulation results revealed increases in total porosity and in connected fraction of
capillary pores due to the existence of aggregate. The de-percolation threshold of capillary porosity was found not only related to total porosity and image resolution, but also governed by the spatial distribution of capillary pores.
Static Loading Investigation on Well Cover of Reactive Powder Concrete
Authors: Xing Feng , Deng Liang Peng , Cao Zheng Liang , Huang Li Dong
Published: March 2009

Reactive powder concrete (RPC), which is a new cement-based composite material with ultra-high strength, low-brittleness, excellent durability, is adopted to make well covers. In addition, static loading tests of the well covers are carried out. The test results show that the loading capacity of the RPC well covers can meet the requirements for different situations, such as the special roads, the city motorway, footway, various parking places, etc.
Experimental Study and Finite Element Analysis on RPC Footwalk Braces
Authors: Yan Zhi Gang , Yan Gui Ping
Published: March 2009

In this paper, a series of Reactive powder concrete (RPC) footwalk braces without conventional steel bars are designed for the Qing-Zang railway. Experimental studies on the braces are conducted in order to test the mechanical character of the braces. Totally eight RPC footwalk braces are experimentally
measured with static load. According to the analysis of the experimental results, the ratio of the crack load got from the experiment to the design load is 2.54 and the deflection ductile coefficient is 2.32. The experimental results show that the mechanical performance of RPC footwalk braces can satisfy the engineering requirements and there is enough safety margin for footwalk braces. A three-dimensional finite element analysis (FEA) is also carried out and the results of FEA are compared with that of the experiments. The results show that the FEA method can be used in designing the RPC footwalk braces.
Inhibiting Effect of Mineral Powder on Sulfate Attack of Cement Mortar
Authors: Niu Quan Lin , Feng Nai Qian
Published: March 2009

ASTM C1012 and GB2420 method were employed to evaluate the inhibiting effect of
different mineral admixtures on sulfate attack of cement mortar, and the mass loss of mortar specimens after drying-wetting cycles was measured for comparison. It is shown that all the mineral admixtures, including ground blast furnace slag (SL), fly ash (FA), natural zeolite (NZ) and metakaolin (MK) were effective in decreasing the 15-week expansion and increasing the corrosion resistance coefficient of the specimens immersed in Na2SO4 solution. The wetting and drying test however, showed inconsistent result, as both physical and chemical attack may soon occur due to quick accumulation of sulfate by capillary absorption instead of diffusion mechanism.
A Comparison Study of Surface Hardening by Grinding Versus Machining
Authors: Liu Zhan Qiang , Ai Xing , Wang Zhao Hui
Published: March 2009

This paper presents a comparison study of surface hardening by grinding versus machining. The technological, economical and ecological merits of machining hardening and grind-hardening process for steels are described. The mechanisms of machining hardening and grind-hardening of steels are investigated and compared. The phase transformation, plastic deformation and white layer
generation are the principal factors contributing to the hardened surface layer by machining and grinding. The influences of the process parameters on the penetrated hardness are given for both grind-hardening and machining hardening operations. The future development trends of the grind-hardening and machining hardening are also presented.
Studies on the Grinding Characteristics of SiC Particle Reinforced Aluminum-Based MMCs
Authors: Sun Fang Hong , Li X.K. , Wang Y. , Chen Ming
Published: March 2009

SiC-particle-reinforced aluminum-based metal matrix composite is one of the important composites among the metal matrix composites, for their various advantages such as lightweight, high specific modulus, specific strength, wear resistance and high temperature resistance. The precision machining of these advanced materials will not be possible without the solution of the
grindability problem, which resists wide spread engineering application of PRAlMMCs as precise parts. This paper investigates the grinding performance and burn mechanism of SiC-particle-reinforced aluminum-based MMCs through thesystematical grinding experiments. Grinding characteristics of these MMCs including grinding force, grinding temperature, morphology of ground surface, surface roughness, residual stress, and chemical composition of the surface layer are obtained and analyzed by the various advanced measuring method. Experiment
results reveal the varieties of grinding force, grinding temperature and surface integrity with the onset of grinding burn. The grinding burn mechanism can be unveiled by the varieties of grinding properties. Grinding experiments are conducted under different grinding conditions so as to explore the appropriate grinding parameters to obtain good surface integrity. The research results are of great significance for high efficiency and precision grinding of MMCs, thus promote the wide application of these advanced materials on the precise and wearable components.
Mechanism Analysis of Improving Grinding Quality with Machining Fluids of Oil Filmed Water Droplets
Authors: Wang A.L. , Wei Y.Q. , Zhu X.J. , Wang Jan Yong , Zheng Z.Z. , Sun Xu Dong , Liu Z.Z.
Published: March 2009

Green machining fluids of oil-filmed water-droplets (OW) can be produced by means of combined mist-jet with cooled air, minimum naturally dissoluble oils (botanic or ester oils) and little water, which are beneficial to realize zero-emission machining and thoroughly eliminate the influences of the conventional water-miscible machining fluids on the operators’ health and the eco-environments as well as save energy consumption and lower in production costs. In this study, grinding performances and mechanism analyses of green machining fluids are investigated by comparison to the conventional ones such as emulsion flood coolant on the plane NC grinder. The investigations have further shown that green machining fluids can improve grinding quality in comparison with emulsion flood coolant due to good lubrication and cooling effects, which are applicable to many situations of machining processes.
The Principle of Magnetic Abrasive Finishing under Rotating Electromagnetic Field and Its Application in Surface Finishing of Heavy Crankshaft
Authors: Yao P.X. , Chen H.L. , Wang Jian Mei , Yang Shu Cai , Zhang Y.X.
Published: March 2009

Magnetic abrasive finishing (MAF) is a processing technology using magnetic abrasive grain (MAG) under magnetic field to finish surface of workpiece. The magnetic fields used in MAF include permanent magnetic field and electromagnetic field. Two conditions must be taken into consideration in the finishing surface of workpiece. One is the sufficient cutting force; the other is the relative moving
speed between MAG and workpiece. The principle of step-motor rotating magnetic field is used to produce rotating magnetic field (RMF) in this paper. RMF brings MAG to rotate and keeps workpiece immovable. Meanwhile, the coins vibrate within a definite angle range and reciprocate in axial direction so as to process the outer cylindrical surfaces. Yoke iron is made of two halves so that the coins for
rotating magnetic field will be keyed to some section of heavy crankshaft, thus realizing cylindrical surface finishing on the heavy crankshaft. MAG are of importance to MAF . Six performance indexes related to MAG are suggested by studying on process parameters.
Drive Control of Dithering Table for Grinding
Authors: Ruan Jian , Pei X. , Yu Z.Q. , Li S. , Yuan Ju Long
Published: March 2009

In grinding viscous materials, such as stainless steel, aluminum and many polymeric
materials, the application of a dither on the workpieces proves to be an effective way to enhance the quality of surface finish. A linear stepper motor is utilized for this purpose. By means of the PWM control to the adjacent phase coils, the linear stepper can drive the sliding table to make reciprocating motion and also to produce a desired dither signal, while the grinding is undertaken to the attached workpiece. In this paper, a linear stepper motor is introduced to drive the sliding table and a modulated control strategy is used to control the linear stepper continuously, which
also generates an additional dither on the sliding table and the attached workpiece. The dither amplitude can be adjusted by means of the modulated frequency. Experiments are designed to measure the practical dither signals and to verify the effectiveness of improving surface finish quality using a dither. It is demonstrated by both theoretical and experimental results that by means of proposed table drive, a rather wide band of dither signal can be acquired and can meet the most demand of viscous material grinding.
Dynamic Mechanical Properties of MWNTs/Phenolic Nanocomposites
Authors: Yeh Meng Kao , Tai Nyan Hwa , Liu Jia Hau
Published: March 2009

Two different types of multi-walled carbon nanotube (MWNT), the dispersed and the network MWNTs, were used to reinforce the phenolic resin. The MWNTs/phenolic nanocomposites were tested by a dynamic mechanical analyzer (DMA) to characterize their dynamic mechanical properties. The results showed that increasing the MWNT content can increase the storage modulus, the loss modulus and the glassy transition temperature of the MWNTs/phenolic nanocomposites. A subambient loss transition is seen in the nanocomposites with network MWNTs which results in a better impact resistance property in the nanocomposites. The glassy transition temperature of the nanocomposites with network MWNTs is higher than that of nanocomposites with dispersed MWNTs. The MWNT additive in phenolic resin can be used to improve the dynamic mechanical properties of the MWNTs/phenolic nanocomposites. The tensile failure morphologies of MWNTs/phenolic nanocomposites were also examined using field emission scanning electron microscope (FESEM) to explain the difference between the two types of nanocomposites.
Design of Micro-Actuators Using Compliant Mechanism
Authors: Yoo Jeong Hoon , Min Seung Jae
Published: March 2009

Recent trend on the research for the storage devices are focusing the realization of the small size and the increase of the recording density. This study is on the development of the design process of the swing arm type actuator composed of two actuators for tracking and focusing that can be widely used in the mobile storage devices. The coarse actuator for tracking is activated by the voice coil motor (VCM) and the fine actuator is activated by PZT. For the design of such actuators, it is required to maximize the sensitivity (force/unit current) as well as to satisfy the dynamic constraints. This research is focusing to increase the sensitivity of the actuator. As a design methodology, topology optimization to design a compliant mechanism can be used for the design of the coarse actuator as
well as the fine actuator since increasing the sensitivity is correlated with maximizing the deformation at a certain point for specified exciting forces. For the coarse actuator design, it is necessary to optimize the VCM to maximize the magnetic force: therefore, the parameter optimization technique is applied for the VCM design. Based on the VCM design, the structural part is designed not only for maximizing the sensitivity but also considering the dynamic characteristics. For the fine actuator
design, the compliant mechanism excited by the pressure from PZT is designed by topology optimization to increase the sensitivity. The resulted design is expected to manufacture the prototype of small form factor actuators.
Time-Temperature Equivalence for Rocks
Authors: Liu Quan Sheng , Wang Chong Ge , Xu X.C. , Yamaguchi Tsutomu
Published: March 2009

Based on the theory of irreversible process thermodynamics, non-linear stress-strain-temperature equations are derived, together with an expression for time-temperature equivalence. In addition, an equation of shift factor for time-temperature equivalence is also obtained. The parameters in the equations are experimentally determined and the main curves for creep compliance and cohesion of TGP granite are obtained by a series of creep tests. It is proved that both deformation and strength of the TGP granite follow the time-temperature equivalent principle.
On the Active Failure Surface in the Backfilled Clay behind Rigid Retaining Wall in Slope Engineering
Authors: Xu X.C. , Jiao Yu Yong
Published: March 2009

In the classical Coulomb’s earth pressure theory, the failure surface in the backfilled clay behind rigid retaining wall in slope engineering is assumed a plane. However, it has been proved by a number of laboratory and field tests that this failure surface is actually a curving surface. In this paper, based on the vertical differential element method and the variational principle, a new analytic solution to determine the actual failure surface in the backfilled clay is derived, and the effects of the backfilled clay’s properties as well as the effects of the retaining wall’s smoothness are discussed. The result obtained from the proposed approach is compared with Coulomb’s earth pressure theory.
Impact Damage and Strength Reduction Behavior of Honeycomb Sandwich Structure Subjected to Low Velocity Impact
Authors: Kang Ki Weon , Kim Jung Kyu , Kim Heung Seob
Published: March 2009

The goals of the paper are to identify the impact damage and strength reduction behavior of sandwich structure, composed of carbon/epoxy laminates skin and Nomex core with two kinds of thickness (10 and 20mm). For these, low velocity impact tests were conducted using the instrumented impact-testing machine and damages are inspected by SAM. And then, subsequent static tests are conducted under flexural loading to identify the strength reduction behavior of the impacted sandwich structures. The impact damages are mainly delamination in carbon/epoxy skin and their behavior is mostly independent of core thickness. Also, their energy absorbing behavior is identified through calculating the energy absorbed by impact damage. Finally, the strength reduction behavior is evaluated through Caprino’s model, which was proposed on the unidirectional laminates.
Penetration Fracture Characteristics of CFRP Curved Shells According to Oblique Impact
Authors: Yang In Young , Cho Young Jea , Im Kwang Hee , Cha Cheon Seok , Kim Young Nam
Published: March 2009

CFRP (Carbon Fiber Reinforced Plastics) of the advanced composite materials as structural materials for vehicles, has a wide application in light weighs structural materials of airplanes, ships and automobiles because of high strength and stiffness. However, there is a design variable to be considered in practical application of the laminate composite material, that is, this material is vulnerable to transverse impact. This paper aims at evaluating the effects of curvature and oblique impact on the penetration characteristics of composite laminate shells. They are stacked to [02/902]S, [03/903]S and [02/903/0]S, [0/902/0]S and their interlaminar number two and four. Those specimens were prepared to varied curvature radius (R=100, 150, 200mm and ∞). They are cured by heating to the appropriate hardening temperature (130oC) by means of a heater at the vacuum bag of the autoclave. Test specimens were prepared with dimensions 100mm×140mm. When the specimen is subjected to transverse impact by a steel ball, the velocity of the steel ball was measured both before and after impact by determining the time for it to pass two ballistic-screen sensors located a known
distance apart. In general, the critical penetration energy increased as the curvature increased, interface decreased and slope angle on the impact surface increased.
Probabilistic Approach for Reliability Estimation of Corroded Pipelines
Authors: Lee Ouk Sub , Kim Dong Hyeok , Myoung No Hoon , Hwang Si Won
Published: March 2009

Pipelines widely used for the transportation of varying fluids from one place to another should be maintained in good condition to avoid, if possible, the occurrence of corrosion in pipelines to keep its reliability in terms of fracture and damage. The reliability of buried pipelines with corrosion defects is estimated using the failure probability. The FORM (first order reliability method) is utilized to estimate the failure probability of buried pipeline with various formulas for external stress in pipe and three different corrosion models. In this paper, it is recognized that the failure
probability increases not only with increasing exposure time, operating pressure and diameter of pipe but also with decreasing wall thickness and yield stress of pipe material in three different corrosion models. And the effects of the scattering of random variables regarding reliability of pipelines on failure probability are investigated, systematically. Furthermore, the target safety level is used to determine the level of safe of corroded pipeline and the effects of varying boundary conditions on target safety level are also estimated.
Computational Analysis of the Effects of Microstructures on Damage and Fracture in Heterogeneous Materials
Authors: Mishnaevsky Leon
Published: March 2009

3D FE (finite element) simulations of the deformation and damage evolution of particle reinforced composites are carried out for different microstructures of the composites. Several new methods and programs for the automatic reconstruction of 3D microstructures of composites on the basis of the geometrical description of microstructures as well as on the basis of the voxel array data have been developed and tested. Different methods of reconstruction and generation of finite element models of 3D microstructures of composite materials (geometry-based and voxel array based) are discussed and compared. It was shown that FE analyses of the elasto-plastic deformation and damage of composite materials using the microstructural models of materials generated with these methods yield very close results. Numerical testing of composites with random, regular, clustered and gradient arrangements of spherical particles is carried out. The fraction of failed particles and the tensile stress-strain curves were determined numerically for each of the microstructures. It was found that the rate of damage growth as well as the critical applied strain, at which the damage growth in particles begins, depend on the particle arrangement, and increase in the following order: gradient < random < regular < clustered microstructure.
Solder Joint Reliability Analysis of WLCSP Based on Inelastic Analysis
Authors: Chang Chia Lung , Lin Tzu-Jen , Huang Kenny
Published: March 2009

Nonlinear finite element analysis is performed to evaluate the reliability of the solder
joint of wafer level chip scale package (WLCSP) under accelerated temperature cycling test. The solder joint is subjected to the inelastic strain that is generated during the temperature cycling test due to the thermal expansion mismatch between the various materials of the package and PCB (printed circuit board). The equivalent stress, equivalent inelastic strain, total shear strain, and hysteresis loop of the solder joint are determined in the simulation. The equivalent inelastic strain
and total shear strain range of the joint are obtained as damage criterion to predict the solder fatigue. Both Coffin-Manson and Modified Coffin-Manson fatigue life prediction models are used to estimate the thermal fatigue life of WLCSP solder joints under temperature cycling test. Also, the effects of the material properties of the stress buffer layer (SBL) on the fatigue life of the solder joint are discussed.
Optimum Design of a Planar 3-DOF Ultra-Precision Positioning Mechanism Using a Booster
Authors: Han Seok Yoon , Kim J.O. , Park J.Y. , Yi Byung Ju , Chung G.B.
Published: March 2009

Ultra-precision positioning systems basically require high natural frequency and
sufficient workspace. To cope with this requirement, flexure hinge mechanisms have been proposed. However, previous designs have difficulty satisfying the functional requirements of the system due to problems in the modeling and optimization process since they are coupled. Therefore, this paper performs optimum design of a planar 3-D ultra-precision positioning mechanism using a booster based on axiomatic design. Based on preliminary kinematic analysis and dynamic modeling of the system, an optimum design is conducted. To examine the effectiveness of the optimal parameters obtained by a theoretical approach, a simulation is performed by FEM. The simulation result shows that a natural frequency of 200.53Hz and a workspace of 200 μm x 200 μm can be ensured, which is in very close agreement with the specified goal of design.
Comparison of Mechanical Properties of Compression and Injection Molded PEEK/Carbon Fiber Reinforced Composites
Authors: Lee Dong Joo
Published: March 2009

The tensile, fatigue and creep properties of carbon fiber filled poly(ether-ether-ketone) or PEEK were compared by employing injection and compression molding processes. The specimens with different initial fiber lengths were fabricated using compression and injection molding methods. The effects of fiber length on mechanical properties are evident in cases of specimens made by compression molding. But, the injection molded samples show no differences in tensile and fatigue strengths contingent on the initial fiber length. Similarly, the effects of fiber volume
fraction on tensile and fatigue strengths are more evident for the compression molded specimens than the injection molded specimen. For the creep properties, even the injection molded specimens show some improvement for long reinforcing fibers especially as temperature is increased. When the influence of time and temperature is considered, the effects of fiber length on mechanical properties are very significant. Also, these results represent the significant fiber damage during
injection molding.
Micromechanical Characterization Parameters for a New Failure Criterion for Composite Structures
Authors: Yudhanto A. , Tay Tong Earn , Tan Vincent B.C.
Published: March 2009

Strain Invariant Failure Theory (SIFT) is a newly-developed failure criterion for composite structures [8, 9]. SIFT comprises two main features, namely micromechanical finite element modification and critical strain invariant parameters. Micromechanical finite element modification is performed to incorporate residual strains between fibers and matrix into homogenized finite element lamina solution. The presence of residual strains takes into account the mechanical and thermal (environmental) effects. Critical strain invariant parameters can be obtained from simple tensile test by carefully observing the occurrence of damage initiation in composite constituent. Strain tensors extracted from experiment are substituted into strain invariant parameters of i J1 (first invariant of strain; i = f, m—fiber, matrix) and i vm ε (equivalent strain or von Mises strain; subscript vm stands for von Mises). As noted in [8, 9], three critical strain invariants were found to be the onset of composite failure for carbon-fiber/epoxy system; they are m J1−cr , f vm−cr ε and m vm−cr ε . Micromechanical characterization parameters aim to provide general insight on the critical state of strains in which damage initiation locus may be determined by using SIFT critical parameters. Micromechanical model was subjected to six different loading conditions (three normal deformations and three shear deformations) and strain tensors (ε1, ε2, ε3, ε12, ε13, ε23) were extracted from finite element analysis. Micromechanical characterization parameters were obtained by normalizing the strain invariants of micromechanics analysis with respect to critical strain invariant. Important issues such as effect of fiber volume fraction and fiber packing arrangement are briefly discussed.
Stress Analysis in Single and Multi Fastened Single-Lap Composite Joints
Authors: Chun Heoung Jae , Choi J.M. , Byun Joon Hyung
Published: March 2009

The use of composite materials in many engineering structures has increased recently. The structures are jointed together by single or multiple bolted mechanical fastening to transfer the loads from one member to another. Applications of such joints require adequate knowledge of stress distribution in the vicinity of the boundary of pin hole. In this study, stress analysis is conducted with finite element method to study the stress distributions in the vicinities of both single-pin and multi-pin loaded holes of multi-axial warp knit fabric composite laminates. The perfect fit condition and contact with friction between the pin and hole without lateral constrain are assumed in the analysis. Effects of friction, stacking sequence, ratio of edge distance over hole diameter, ratio of width over hole diameter, number of pins, number of rows, number of column and hole patterns are evaluated. The results show they have a significant influence on joint performance.
Strength Anisotropy Estimation of Plain-Weave Fabrics by Pseudo-Continuum Model
Authors: Kuwazuru Osamu , Yoshikawa Nobuhiro
Published: March 2009

The anisotropy of the tensile strength of plain-weave fabric is numerically evaluated by the finite element simulations. The plain-weave fabrics show complicated deformation behavior that is quite different from that of the continuum. The mechanics of woven fabric is not sophisticated yet enough to evaluate the strength and fracture mechanism in arbitrary stress conditions. The opacity of the tensile strength significantly diminishes the material reliability for the advanced use of fabrics. This study addresses the ideal tensile strength in arbitrary directions by using the pseudo-continuum model, which we have proposed to predict the deformation behavior and fiber stresses of the plain-weave fabrics. In this study, the numerical simulations of uniaxial extension in various directions are carried out by one finite element subjected to ideally uniform deformation, and we predict the breaking loads and elongations corresponding to the ultimate strength of the fiber.
Effect of Silicon on Strength and Fracture Surfaces of Aluminium–Silicon Casting and Heat Treated Alloys
Authors: Haque Mohammad M. , Syahriah Nur I. , Ismail Ahmad Faris
Published: March 2009

Aluminium-silicon alloys having different silicon contents (13, 20 and 27 percent) were used in the present study. The molten alloys were poured in to a mild steel die to cast tensile test bars. Then tensile and hardness tests were performed in order to analyze the properties and fracture surfaces of the cast specimens. Results show that as silicon content increases, the alloy becomes harder and less ductile. At the same time, the presence of alloying and impurity elements in the alloys forms complex compounds and intermetallic phases. They present deleterious effects on the strength of the alloys, causing a lowering of the energy required to fracture the test specimens with little permanent extension. However, heat treatment operations altered the structures and properties of the aluminium-silicon alloys. Heating to higher temperature, then quenching, ageing and tempering make the alloys stronger up to 13% silicon and beyond that limit the alloys become weaker, fracturing at
lower load. The appearance of fracture surfaces after tensile testing showed these differences. This investigation also suggests that for the aluminium-silicon alloys containing 20% and 27% silicon do not require any expensive and time consuming thermal treatment operations, since properties do not improve with such treatments.
Cool Storage of Human Tissue Engineered Bone for Bone Regeneration Therapy
Authors: Satoh N. , Yoshikawa Takafumi , Miyazaki Kazuhide , Shigematsu Hideki , Ueda Y. , Koizumi M. , Takakura Yoshinori
Published: March 2009

Availability, storage and transportation of engineered bone tissue fabricated in vitro are major practical problems associated with adequate use of bone replacement grafts for the treatment of bone diseases. The ability to maintain viable engineered bone tissue would facilitate future clinical applications. In the present study, we investigated time required for transportation of engineered bone removed from cool storage, from the culture room to the operating room; and examined effects of cool storage on survival of engineered bone tissue. Bone marrowcells were
obtained from the iliac bone of a 60-year-old male affected with lumbar spondylosis, and then incubated in standard medium. After two weeks in primary culture, cultured cells were trypsinized, and a concentrated cell suspension was incubated with a porous beta-TCP block. After 3 weeks of subculture with the osteogenic medium containing dexamethasone etc., engineered bone tissue was
collected, stored for 0, 6, 12, 24 hours at 4 °C, and was subcutaneously implanted into the back of nude mice. Six weeks after implantation, implants were harvested. Before and after implantation, significant activity could be detected in all animals. In in vitro and in vivo situations, osteogenic activity of engineered bone tissue could be maintained even after 24 hours. These results provided information on appropriate storage conditions for engineered bone tissue.
Morphological Characterization of Femur and Parietal Bone Mineral of Rats at Different Ages
Authors: Bertazzo S. , Bertran Celso A. , Camilli J.A.
Published: March 2009

Some microscopy studies on the mineral phase of bone have been carried out either utilizing Optical or Scanning Electron Microscopy (SEM), generally around 1000x magnification, to observe the interaction between cells and bone mineral. Other studies have been utilizing Transmission Electron Microscopy (TEM), generally around 1000000x magnification, to observe the fundamental particles that form bone mineral. The literature lacks works that utilize Scanning Electron Microscopy
around 10000x magnification, particularly suitable for the study of structures composed by the aggregation of fundamental particles. The objective of this work was to study the morphologic differences between the mineral phase of femur and parietal bone of Wistar rats. Observation of the micrographs showed that the microscopic morphology of the mineral phase of femur was very similar
to that of the parietal bone. It was also possible to notice that the morphology of the mineral phases varied with age, yet this variation was practically the same for the material obtained from the two types of bones.
Bioactive Organic-Inorganic Hybrids Prepared from Poly(Vinyl Alcohol) via Modification with Metal Oxides and Calcium Salt
Authors: You Caihong , Miyazaki Toshiki , Ishida Eiichi , Ashizuka Masahiro , Ohtsuki Chikara
Published: March 2009

Organic polymers with ability of apatite formation in body environment are expected as novel bone substitutes having not only bone-bonding ability, i.e. bioactivity, but also mechanical performance analogous to natural bone. Several metal oxides have been found to be effective for the apatite deposition in body environment. In addition, release of calcium ions from the materials significantly enhances it. In this study, we attempted to synthesize bioactive organic-inorganic hybrids from poly(vinyl alcohol) (PVA) by incorporation of titanium oxide or zirconium oxide as
well as calcium salt. Ability of apatite formation on the hybrids was examined in vitro using simulated body fluid (SBF, Kokubo solution). Apatite deposition was observed to occur on the surfaces of PVA/titanium oxide hybrids in SBF, when their compositions were appropriately controlled.