bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation of Damage Scenarios in an FRP Composite Suspension Footbridge
Authors: Votsis R.A. , Abdel Wahab M.M. , Chryssanthopoulos M.K.
Published: March 2009

Simulations of damage scenarios were carried out using a finite element model of a newly constructed FRP composite footbridge, the Wilcott footbridge. This footbridge represents a new generation of suspension footbridges that have lightweight decks made of pultruded glass fibre reinforced polymer (GFRP) composite elements. It offers several advantages over conventional steel or concrete footbridges, e.g. speed of installation, high resistance to corrosion and saving in weight and foundations. On the other hand, its lightness and slenderness make it more sensitive to dynamic effects, both at serviceability and ultimate limit states. A finite element model using 3-D beam elements was constructed and damage scenarios were simulated and introduced in the model. The natural frequencies, mode shapes as well as time responses due to pedestrian loading were predicted. Different size of delamination in the composite deck was simulated at various locations along the bridge. The sensitivity of natural frequencies and mode shapes due to delamination were assessed by comparing the results of the damaged deck to those of the reference intact deck. The effect of changes in the cables’ initial strains on the modal parameters was also examined, and the sensitivity of modal parameters to cable degradation was assessed.
Multidisciplinary Software Developments in a Power Transformers Scenario
Authors: Mariño Perfecto , Poza Francisco , Otero Santiago , Machado Fernando
Published: March 2009

Power transformers’ failures carry great costs to electric companies. To diminish this problem in four working 40 MVA transformers, the authors have implemented the measurement system of a failure prediction tool, which is the basis of a predictive maintenance infrastructure. The prediction models obtain their inputs from sensors, whose values must be conditioned, sampled and filtered before feeding the forecasting algorithms. Applying Data Warehouse tech- niques, the models have been provided with an abstraction of sensors the authors have called Virtual Cards. By means of these virtual devices, models have access to clean data, both fresh and historic, from the set of sensors they need. Besides, several characteristics of the data flow coming from the Virtual Cards, such as the sample rate or the set of sensors itself, can be dynamically reconfigured. A replication scheme was implemented to allow the distribution of demanding processing tasks and the remote management of the prediction applications.
An Analysis about Response of Small Structure Suffered Underwater Explosion
Authors: Wan Q. , Jiang W.K. , Zhao Z.P.
Published: March 2009

According to the characteristics of anti-explosion analysis about the small cylindrical shell structure under water, in which the wave scattering is so great that it cannot be ignored, an approximate procedure is proposed to analyze the shock load of the structure suffered underwater explosion. The shock wave is decomposed as the summation of plane harmonic waves with various frequencies, then the scattered acoustic field around the cylindrical structure is studied, by which the overall pressure distribution on the surface of the structure can be obtained. The average overall pressure of the structure suffered underwater explosion can be calculated also, which can be considered as the underwater explosive load. An underwater explosion trial is done in a lake to validate the proposed procedure, and the results show that the overall pressure distribution on the surface predicated by the procedure theoretically nicely agree with the results of trial. Then, the time history of stresses from the trial is quite close to that from numeric simulation. The procedure is understood easily, and can be applied in analyzing the time history of stresses of small cylindrical structures impacted by shock wave, in which the wave scattering of structures plays a key part.
Vibration-Based Condition Monitoring of Smart Prefabricated Concrete Elements
Authors: Zonta Daniele , Pozzi Matteo , Forti Marco , Zanon Paolo
Published: March 2009

The University of Trento is promoting a research effort aimed at developing an innovative distributed construction system based on smart prefabricated concrete elements that can allow real-time assessment of the condition of bridge structures. So far, two reduced-scale prototypes have been produced, each consisting of a 0.2×0.3×5.6m RC beam specifically designed for permanent instrumentation with 8 long-gauge Fiber Optics Sensors (FOS) at the lower edge. The sensors employed are FBG-based and can measure finite displacements both in statics and dynamics. The acquisition module uses a single commercial interrogation unit and a softwarecontrolled optical switch, allowing acquisition of dynamic multi-channel signals from FBG-FOS, with a sample frequency of 625 Hz per channel. The performance of the system is undergoing validation in the laboratory. The scope of the experiment is to correlate changes in the dynamic response of the beams with different damage scenarios, using a direct modal strain approach. Each specimen is dynamically characterized in the undamaged state and in different condition states, simulating different cracking levels. The location and the extent of damage are evaluated through the calculation of damage indices which take into account changes in frequency and in strain-modeshapes. This paper presents in detail the results of the experiment as conducted on one of these prototypes and demonstrates how the damage distribution detected by the system is fully compatible with the damage extent appraised by inspection.
Gearbox Fault Diagnosis Using Adaptive Redundant Second Generation Wavelet
Authors: Jiang Hongkai , He Zheng Jia , Duan Chendong , Chen Xue Feng
Published: March 2009

Vibration signals acquired from a gearbox usually are complex, and it is difficult to detect the symptoms of an inherent fault in a gearbox. In this paper, an adaptive redundant second generation wavelet (ARSGW) based on second generation wavelet (SGW) is developed. It adopts data-based optimization algorithm to design the initial prediction operator and update operator at each scale. The initial operators are interpolated with zero, and then the redundant prediction operator and update operator are obtained. The splitting step in ARSGW is removed, the approximation signal at each scale is predicted and updated with redundant prediction operator and update operator directly, and the length of approximation signal and detail signal at every scale remains the same, ARSGW eliminates translation variance of SGW. Since the redundant prediction operator and update operator lock on to the dominant structure of the signal, ARSGW can well reveal the characteristics of the signal in time domain. ARSGW is found to be very effective in detection of symptoms from the vibration signal of a large air compressor gearbox with impact rub fault. SGW is also used to analyze the same signal for comparison, no modulation signals and periodic impulses appear at any scale.
A Two-Color Heterodyne Interferometer Based on Diffraction Grating for Displacement Measurement
Authors: Wu G.H. , Cai Z.J. , Zeng Li Jiang
Published: March 2009

A two-color heterodyne interferometer based on the movement of the optical diffraction grating is proposed. The method allows us to measure the phase of synthetic wavelength f s directly and with high accuracy to extend the range of unambiguity for interferometric measurements by using two close wavelengths. Our experiment results show that the uncertainty in displacement measurement caused by the uncertainty in f s is 0.20 µm, smaller than the half of a single wavelength we used. The fringe order of a single wavelength can be determined without ambiguity. The uncertainty in displacement measurement can be improved further by using a single wavelength.
A New Method for the Development of Frequency Standards for the Optical Wavelength Range of 243nm
Authors: Izrailov E.K. , Ezhov V.F.
Published: March 2009

A new method and devices for cooling of atomic hydrogen up to the values less than 100 µK aimed for the development of the optical frequency standard with significantly improved parameters (Δν/ν£1 x 10-16) is discussed. The method exploits the unique properties of atomic hydrogen such as atomic hydrogen does not condense at temperatures as low as 20µK and can not be heated by IR radiation in the absence of atom-wall collisions. Therefore, the most efficient and well-known gas cooling technique can be employed, namely, the adiabatic expansion of the volume occupied by the gas. This approach is used in a cryogenic gas expansion machine. It is suggested to use the adiabatic expansion of the volume of the magnetic atomic trap containing atomic gaseous hydrogen for embodiment of this idea.
A Coaxiality Measurement Method for Hole Using Non-Diffracting Beam Technology
Authors: Zhang X.B. , Jiang X.Q. , Li Z.
Published: March 2009

Combining the non-diffracting beam datum-line method with the roundness measuring technology, a high precision coaxiality measurement method for a hole whose diameter is more than 40mm is proposed. The principle of the measuring system is introduced and error analysis and test to verify it are presented. The measuring uncertainty of this coaxiality system is less than 1µm when the measuring range is within 1.5m. The measuring uncertainty of error of roundness is less than 0.4µm when the error measuring range is -200~+200µm. This system has many advantages and it can be applied widely for coaxiality measurement.
Effects of Rotation Angle on the Circular Test of Geometric Errors
Authors: Liu H.L.
Published: March 2009

DBB was originally manufactured and proposed for checking the accuracy of NC machine tools. The device can also be used to study the relations between motion error of trace and the machine motion error for the purpose of error compensation. The nominal angle obtained through rotation feed rate and sampling time was adopted instead of actual angle which cannot be measured by the device. This project examined in details the effect of the angle deviation problem caused by non-perpendicularity between the movements in axis X and axis Y. The analysis and calculation verified that a squareness deviation would lead to more than 3 times error at some special points, decreasing the accuracy of NC machines for error compensation. For this reason, a device called as Two-Dimensional Ball Bar is proposed based on the DBB.
A New Method for the Measurement of Dynamic Angular Errors of a Photoelectric Shaft Encoder
Authors: Cao X.D. , Fan T.Q. , Geng L.H.
Published: March 2009

A new method for measurement of dynamic angular error of photoelectric shaft encoder using trigger photoelectric collimator is proposed. The photoelectric shaft encoder rotates at an invariable or variable speed less than forty degrees per second. The dynamic angular error is measured. The standard uncertainty of this method is less than 0.5 arc second.
A Real-Time and On-Line Visual System for Seamless Steel Pipe Linearity Measurement
Authors: Liu C.J. , Yang Xue You , Zhu Ji Gui , Ye S.H.
Published: March 2009

Linearity is a very important parameter for seamless steel pipes. A real-time and on-line visual measurement system for seamless steel pipe linearity is presented. The system consists of several structured-light visual sensors. Each sensor can achieve the coordinate of the center of partial steel pipe in its local coordinate system. Through global calibration, all coordinates measured can be transformed into an integrated coordinate system. The linearity error of steel pipe can be assessed. This method can fulfill 100% on-line and real-time linearity measurement. A pair structure-light sensor is designed to improve accuracy and a suspension-wires method for sensor calibration and global calibration is used. Through experiments, it shows that the method not only meets the need of precise calibration but also significantly improves the efficiency and feasibility.
On-Line Industrial 3D Measurement Techniques for Large Volume Objects
Authors: Zhu Ji Gui , Ye S.H. , Yang Xue You , Qu Xing Hua , Liu C.J. , Wu B.
Published: March 2009

Rapid progress in modern manufacturing demands for better measurement technique with on-line characteristics. This paper presents a systematic visual solution for on-line industrial 3D measurement. The solution comprises two parts, a multi-sensor visual inspecting station (MSVIS) and a digital close-range visual inspecting station (DCVIS). MSVIS is an integrated system with many sensors. It can meet the requirement of application with sparse measuring points distributed within a large volume. DCVIS only contains two digital cameras with one or more projectors. It has high relative accuracy and a small set up volume and is suitable for applications with dense measuring points. The combined use of MSVIS and DCVIS can provide a general solution for on-line industrial 3D measurement.
Spline Filters for Surface Texture Analysis
Authors: Krystek Michael Paul
Published: March 2009

Linear filters are widely used for smoothing measurement data in dimensional metrology and surface texture analysis. In the past, the use of linear filters was mainly limited to Gaussian or even 2RC filters. Recent advances in spline filter theory have paved the way for the development of more flexible and powerful linear filters. This paper deals with the general characteristics of these filters.
A New Three-Dimensional Profilometer for Surface Profile Measurement Using Digital Fringe Projection and Phase Shifting
Authors: Chen Liang Chia , Tsai S.H. , Fan Kuang Chao
Published: March 2009

The development of a three-dimensional surface profilometer using digital fringe projection technology and phase-shifting principle is presented. Accurate and high-speed three-dimensional profile measurement plays a key role in determining the success of process automation and productivity. By integrating a digital micromirror device (DMD) with the developed system, exclusive advantages in projecting flexible and accurate structured-light patterns onto the object surface to be measured can be obtained. Furthermore, the developed system consists of a specially designed micro-projecting optical unit for generating flexibly optimal structured-light to accommodate requirements in terms of measurement range and resolution. Its wide angle image detection design also improves measurement resolution for detecting deformed fringe patterns. This resolves the problem in capturing effective deformed fringe patterns for phase shifting, especially when a coaxial optical layout of a stereomicroscope is employed. Experimental results verified that the maximum error was within a reasonable range of the measured depth. The developed system and the method can provide a useful and effective tool for 3D full field surface measurement ranging from µm up to cm scale.
Development of a Large Range Nanometer Level Profilometer with Controlled Contact Force
Authors: Yang L. , Gao Y. , Wang Xuang Ze , Xie T.
Published: March 2009

A nanometer profilometer in which the measuring force can be controlled is proposed.
The key part is the nanometer profiling core, which consists of a voice coil motor with a short and movable voice coil and an inductive transducer. According to the A/D value of the transducer signal, the measuring force can be adjusted to approximately µN level by use of a PID control algorithm. The advantages of contact type and non-contact type profilometer are possessed by the proposed instrument.
Artificial Life for Pavement Distress Survey
Authors: Wang Qi , Zhang Hui
Published: March 2009

Automatic recognition of road distresses is of considerable interest since it facilitates road maintenance. We propose the use of artificial life for pavement distress survey. All artificial organisms in the artificial life algorithm exhibit the principle of cooperation which can be found in computer virtues and the hunting process of predators. Experimental results demonstrate that the proposed approach has a strong effect on noise removal such as elimination of oil stains and removal of dark spots which is one of the most difficult problems in pavement distress survey
Temperature Effect on the Stability of CuO Nanofluids Based on Measured Particle Distribution
Authors: Chang Ho , Lo Chih Hung , Tsung Tsing Tshih , Cho Y.Y. , Tien D.C. , Chen Liang Chia , Thai C.H.
Published: March 2009

This study aims to investigate the temperature effect on particle size of copper oxide
nanofluid produced under optimal parameters of the Arc Spray Nanoparticle Synthesis System (ASNSS) developed in this research. The purpose is to understand the aggregation feature of copper oxide nanofluid in a higher-than-room-temperature environment and to analyze its size change and the motion behavior of suspended nanoparticles. This study employs an ambient temperature controller to maintain the environment temperature within the scope of normal fluid work temperature to obtain data on the change in suspended particles of copper oxide nanofluid under varying temperatures and through change of time. Experimental result shows that the particle size distribution of copper oxide nanofluid changes when the temperature rises due to the slight absorption and aggregation phenomena between particles, and that the change in environmental temperature can accelerate the aggregation of copper oxide nanofluid, which can affect its stability in application. However, the change in particle size distribution will gradually stabilize for a longer duration of constant temperature.
A High Sensitivity Pressure Sensing System with Fiber Bragg Grating Using the Transverse Strain Characteristics of a Straight Bourdon Tube
Authors: Jiao M.X. , Zhao E.G. , Liu Y.M. , Qi R.L.
Published: March 2009

A high sensitivity pressure sensing system with a fiber Bragg grating (FBG) using the transverse strain characteristic of a straight bourdon tube (SBT) is presented and demonstrated for the first time to our knowledge. The transverse strain of the SBT makes the FBG tensioned. The pressure can be determined by measuring the shift of the Bragg wavelength. The experimentally obtained results indicate that the shift of the Bragg wavelength changes linearly with the applied pressure and the sensitive coefficients of pressure are approximately 6.22x10-3MPa-1. This represents a sensitivity value approximately 9.66x10-3pm/Pa. The pressure sensing system shows little hysteresis error.
A DDS Waveform Generator for Electromagnetic Non-Destructive Testing
Authors: Cao X.H. , Luo F.L. , Bai F.T. , Zhang Y.H.
Published: March 2009

A direct digital synthesis (DDS) waveform generator for electromagnetic non-destructive testing (NDT) is presented in order to improve the measurement quality. The advantage and disadvantage of analogue and digital circuit waveform generators are analyzed. The DDS technique is preferred. The principle of DDS technique is introduced and the hardware and software design of a DDS waveform generator is described. The characteristics of the waveform generator based on a DDS chip AD7008 are that the signal frequency is of high stability, high precision and high resolution. Furthermore, the amplitude, frequency and phase can be continuously adjusted. An experimental electromagnetic NDT system is built and the testing results are analyzed. The system uses digitally generated sine waves as exciting, reference and demodulation signals. Experimental results show that the DDS waveform generator improves the signal-to-noise ratio. This kind of wave generation circuit is used not only in NDT but also in other instruments, such as electrical impedance tomography (EIT), which need signals with high stability, high precision and high resolution.
3D Digital Measurement of Large Scale Objects Based on Viscous Target
Authors: Wu B. , Zhu Ji Gui , Yang Xue You , Xue T. , Ye S.H.
Published: March 2009

For 3D digital measurement of large scale objects, image mosaic is the key technology to achieve whole measurement for a small measuring field of the sensor unit. A viscous-target-based three-dimensional image mosaic technology is proposed. The screw theory is introduced to realize the spatial image mosaic. The method permits an automatic identification of targets and a better matching for the feature coded technology. In experiments, the method was proved to be valid, with a relatively high precision on three-dimensional image mosaic. The relative error of the space length measurement is less than 0.6%.
The Constitutive Behavior of Metallic Foams Using Nanoindentation Technique and FE Modeling
Authors: Kim Am Kee , Hasan Md Anwarul , Choen Seong Sick , Lee Hak Joo
Published: March 2009

Nanoindentation data measured on the cell-wall of Al-alloy foams were analyzed to obtain the material properties of the cell wall. Using the obtained material properties, stress-strain curve of the foam in uniaxial compression was constructed by finite element modeling. The model developed for the analysis was a multiple cell model which utilized the unit cells as the basic building block of the foam. Both the in-plane and through-thickness density variations of the foam were considered in the model. The through-thickness density variation which is a function of casting or foaming process was represented using different densities for different foam layers, while the in-plane density variation which arises from internal defects (such as porosities, second phase particle, inclusions etc.) was assumed to follow a statistical probability distribution of Gaussian type. Uniaxial compression test was performed and the finite element analysis result was compared with the experimental result. The numerical model used in the study overpredicted the crushing strength of foams indicating that the model needs to be improved for predicting the real foam properties with better accuracy.
Influence of Stress Parallel to Crack Plan on Subcritical Crack Propagation in Glass under Biaxial Stress
Authors: Li Wei Hong , Wang Li Jiu , Tang Chun An , Bao Yi Wang , Chen Xiong , Xu Shuang
Published: March 2009

The aim of this study is to demonstrate the influence of the stress parallel to the crack plane on subcritical crack growth in brittle materials by using a numerical code MFPA2D. The mechanism of this influence is also discussed. The curves of subcritical crack extension vs. strain of brittle materials under uniaxial and biaxial stress were obtained through numerical tests with acoustic emission consideration. The results showed that the tensile stress parallel to the crack plane has the effect on crack arrest, while the compressive stress parallel to the crack plane plays important role in crack opening process. The numerical results were consistent with experimental observed result, which shows the reliability of the numerical method, and provides theoretic foundation for failure analysis and life estimation of brittle materials.
The Effects of Residual Stress of Contact Fatigue Life for Railway Wheels
Authors: Seo Jung Won , Goo Byeong Choon , Chung Heung Chai , Choi Jae Boong , Kim Young Jin
Published: March 2009

Railway wheels and axles belong to the most critical components in railway vehicles. The service conditions of railway vehicles became more severe in recent years due to the increase of speed. Therefore, a more precise evaluation of railway wheel life and safety has been requested. Wheel/rail contact fatigue and thermal cracks due to braking are two major mechanisms of the railway wheel failure. One of the main sources of the contact zone failure is the residual stress. The residual stress on wheel is formed during the manufacturing process which includes a heat
treatment, and then, is changed in the process of braking which results in wheel/rail contact stress and thermal stress. In this paper, an evaluation procedure for the contact fatigue life of railway wheel including residual stress is proposed. Also, the cyclic stress history for fatigue analysis is simulated by applying finite element analysis for the moving contact load. As a result, a fatigue life estimation methodology is proposed for railway wheels which includes the effects of residual
stresses due to heat treatment, braking and repeated contact load, respectively.
Plasticity-Induced Martensitic Phase Transformation in Fatigue of Unnotched SUS304 Plates
Authors: Iwasaki Yoshifumi , Nakasone Yuji
Published: March 2009

The present study has investigated plasticity-induced martensitic phase transformation in fatigue of unnotched SUS304 plates. Martensitic phase transformation occurred in uunotched SUS304 plate specimens fatigued at room temperature in air. Volume fraction Va’ of a’ martensite in the uunotched portion of fatigued specimens was measured by ferrite scope. The relations between the maximum value of Va’, Va’max, and the number of load cycles N were represented by reverse sigmoidal curves for all the applied stress range Ds levels tested in this study. For the most portion of fatigue life, the value of Va’max remained almost constant. This value was increased with increase in the value of Ds. The spatial distribution of Va’ in the specimens varied with N: i.e., continued cycling of stress made a’ transformation localized near the central portion of specimens where the Va’ value reached as high as 35-40%. This value is more than doubled compared to the highest Va’ value found in the tensile tests of SUS304 at room temperature in air. Invisible cracks of 200µm in length were found in the high Va’ value region. These results imply that the measurement of Va’ in fatigued SUS304 components may detect crack initiation sites and may predict residual fatigue life.
A Biomimetic Method of Hydroxyapatite Powders Synthesized in Simulated Body Fluid
Authors: Wang Feng , Li Mu Sen
Published: March 2009

Hydroxyapatite (HA) powders were directly synthesized in simulated body fluid (SBF) at 37°C, without the need for high-temperature calcified. These powders were found to contain trace amount of CO32-, Cl-, Na+ and K+ impurities, originated from the of SBF solutions during their deposition. The characterizations of the synthesized HA powders were performed by X-ray diffraction (XRD), Fourier-transformed infra-red spectroscopy (FTIR) and Transmission electron microscope (TEM). The experimental results showed that the HA synthesized by the SBF route might be more close to that human bone in structure and compositions. Furthermore, the processes flow for HA synthesis was optimized and the synthesized mechanism was also discussed.
Friction and Wear Characteristics for Automotive Leaf Spring Materials due to the Influence of the Residual Stress
Authors: Oh Se Doo , Jung Won Wook , Bae Dong Ho , Lee Young Ze
Published: March 2009

In this paper, the effects of the residual stresses on the life of structural engineering
components were investigated to predict the wear-life. Residual stresses are usually created by the surface treatment, such as shot peening or deep rolling. The objective of the experimental investigation was focused on the influence of friction and wear characteristics due to the residual stress under dry sliding condition and the measurement of the interleaf friction. Test specimens were made of SUP9, the leaf spring material. The residual stresses were created on their surface by shot peening treatment. Residual stress profiles were measured on the surface and subsurface by means of X-ray diffraction method. Also, the sliding tests were carried out under the different contact pressure and the same sliding velocity of 0.035m/s in order to investigate the friction and wear characteristics of leaf surfaces. Leaf spring assembly tests were performed by the ultimate tensile machine with sticking strain gauges on the leaf surfaces in order to evaluate interleaf friction characteristics. We compared friction coefficients, wear volumes and wear rates of the shot-peened specimens with those of the unpeened specimens, and evaluated the effects of residual stress on the tribological characteristics. We obtained the load-displacement curves, and measured interleaf friction force and interleaf friction coefficient of leaf spring assembly from these curves.
Tribological Behavior of Multilayered WC-Ti1-xAlxN Coatings Deposited by Cathodic Arc Deposition Process on High Speed Steel
Authors: Cho Chung Woo , Jeong Sung Hoon , Ahn Seung Ho , Kim Jung Gu , Lee Young Ze
Published: March 2009

Four different multilayered coatings with different Al concentrations were deposited on AISI D2 steel. The prepared coating samples were designated as WC-Ti0.6Al0.4N, WC-Ti0.53Al0.47N, WC-Ti0.5Al0.5N and WC-Ti0.43Al0.57N. The multilayered coatings were investigated with respect to coating surface and cross-sectional morphology, roughness, adhesion, hardness, porosity and tribological behavior. Especially, wear tests of four multilayered coatings were performed by using a ball-on-disc configuration with a linear sliding speed of 0.017 m/sec and a load of 5.38N. The tests were carried out at room temperature in air by employing AISI 52100 steel ball (HR = 66) with a diameter of 10mm. The surface morphology and topography of the wear scars of samples and balls have been determined by using scanning electron spectroscopy (SEM). Results have showed an improved wear resistance of the WC-Ti1-xAlxN coatings with increasing Al concentration.
Effects of Matrix on Mechanical Property Test Bamboo Fiber Composite Materials
Authors: Lim Jae Kyoo , Song Jun Hee , Choi Jun Yong , Kim Hyo Jin
Published: March 2009

In recent years, the use of natural fibers as reinforcements in polymer composites to
replace synthetic fibers like glass is presently receiving increasing attention. Because of their increasing use combined with high demand, the cost of thermosetting resin has increased rapidly over the past decades. However the widely used synthetic fillers such as glass fiber are very expensive compared to natural fibers. Natural fiber-reinforced thermosetting composites are more economized to produce than the original thermosetting. Moreover the use of natural fiber in thermosetting composites is highly beneficial, because the use of natural fibers will be increased. In this study, a bamboo fiber-reinforced thermoplastic composite that made the RTM was evaluated to mechanical properties.
A Model for Determining Crack Opening Stress Intensity Factor Ratio under Tri-Axial Stress State
Authors: He Yu Ting , Li Feng , Shi Rong , Zhang G.Q. , Ernst L.J. , Fu X.J.
Published: March 2009

When studying 3D fatigue crack growth behaviors of materials, to determine the crack opening stress intensity factor ratio is the key issue. Elastic-plastic Fracture Mechanics theory and physical mechanism of cracks’ closure phenomena caused by plastic deformation are employed here. A model for determining the crack opening stress intensity factor ratio under tri-axial stress state is presented. The comparison of the present model with available data and models shows quite good agreement.
Numerical Approach to Fracture of Glass under Biaxial Stress
Authors: Li Wei Hong , Wang Li Jiu , Tang Chun An , Bao Yi Wang , Wang Li Ding , Xu Shuang
Published: March 2009

The fracture behavior of brittle materials under biaxial plane stress has been investigated by means of numerical simulation method with software MFPA2D (Material Failure Process Analysis). The aims of this study are to clarify the fracture dependence of brittle material on biaxial plane stress state. The observation of crack initiation and fracture behavior reveals that the biaxial stresses have strong influence on the fracture properties of glass. Thus, the fracture criterion by the stress intensity factor was questioned for the biaxial plane stress issues. It is confirmed that the tensile stress parallel to the crack plane is an important factor affecting crack arrest, while the compressive stress parallel to the crack plane contributes to crack opening.
Z-Parameter Method for Life Prediction in Low Carbon Steels
Authors: Han Shuang Qi , Zhao Jie , Wang Lai , Gao Hong Bo
Published: March 2009

In this paper, a Z-parameter method is proposed to relate creep rupture data and
microstructure deterioration of three low carbon steels: Cr5Mo, 12Cr1MoV and 20 steels. A new analytic expression of the Larson-Miller parameter verse stress is supposed as: P =Z + C1 lgσ + C2 σ, where C1 and C2 are constants which determine the shape of the curves and related to materials, and the value of parameter Z represents the magnitude deviated from the master curve which corresponds with the deterioration in rupture properties. As the deterioration in rupture properties closely connects with the degradation of microstructure, namely the spheroidization of carbides in pearlite style steel, a linear relationships have been found between the value of Z-parameter and the level of spheroidization E which can be expressed as: Z = a1 + a2 E.
The Assessment of Influence of the Design Factors on the Reliability of BGA Solder Joints
Authors: Jin Jae Chul , Yu Qiang , Shibutani Tadahiro , Abe Hirokazu , Shiratori Masaki
Published: March 2009

In recent years, package downsizing has become one of biggest trends in packaging technologies because of miniaturization and the high integration of electronic devices. As a result, the reliability of fatigue life has been prioritized as an important concern, since the thermal expansion difference between a package and printed circuit board causes thermal fatigue. But, the reliability of thermal fatigue life may be lowered by the dispersion of design factors such as the dimensions,
shapes, and material properties of package systems. Also, the fracture modes (fatigue fracture, brittle destruction in the interface, and compound destruction, and so on) will be affected by these dispersion factors. Although this dispersion should be reduced in order to improve the reliability, reducing all dispersion is inefficient and time-consuming. So, the factors that greatly contribute to thermal fatigue life have to be reduced. In this study, evaluations of the influence of various design factors on the reliability of soldered joints of a BGA (Ball Grid Array) were carried out, and got each influence. With the results, design engineers can rate each factor’s effect on reliability and assess the reliability of their design beginning at the concept design stage. Consequently, it will be possible to avoid almost all reliability problems from the beginning. Also, by rating the factors, the design period can be shortened
Stress Corrosion Cracking Life Estimation of Hold-Down Spring Screw for Nuclear Fuel Assembly
Authors: Koh Seung Kee
Published: March 2009

Hold-down spring screw fractures due to primary water stress corrosion cracking were observed in nuclear fuel assemblies. The screw fastens hold-down springs that are required to maintain the nuclear fuel assembly in contact with upper core plate and permit thermal and irradiation-induced length changes. In order to investigate the primary causes of the screw fractures, the finite element stress analysis and fracture mechanics analysis were performed on the hold-down spring assembly. The elastic-plastic finite element analysis showed that the local stresses at the critical regions of head-shank fillet and thread root significantly exceeded the yield strength of the screw material, resulting in local plastic deformation. Preloading on the screw applied for tightening had beneficial effects on the screw strength by reducing the stress level at the critical regions, compared to the screw without preload. Calculated deflections and strains at the hold-down springs using the finite element analysis were in very close agreements with the experimentally measured
deflections and strains. Primary water stress corrosion cracking (PWSCC) life of the Inconel 600 screw was predicted by integrating the Scott’s model and resulted in a life of 1.42years, which was fairly close to the field experience. Cracks were expected to originate at the threaded region of the screw and propagated to the opposite side of the spring, which was confirmed by the fractographic analysis of the fractured screws.
Reliability Assessment on Thickness Effect in Fatigue Crack Growth
Authors: Kim Seon Jin , Kong Yu Sik , Kwon Sang Woo
Published: March 2009

The evaluation of specimen thickness effect of fatigue crack growth life by the simulation of probabilistic fatigue crack growth is presented. In this paper, the material resistance to fatigue crack growth is treated as a spatial stochastic process, which varies randomly on the crack surface. Using the previous experimental data, the non-Gaussian (eventually Weibull, in this report) random
fields simulation method is applied. This method is useful to estimate the probability distribution of fatigue crack growth life and the variability due to specimen thickness by simulating material resistance to fatigue crack growth along a crack path.
Development of a Fiber-Optic AE Sensor for On-Line Monitoring System
Authors: Nam Jae Young , Choi Jae Boong , Kim Young Jin
Published: March 2009

The objective of this paper is to develop a fiber-optic acoustic emission(AE) sensor applicable to on-line monitoring systems which is suitable for long-distance signal transmission. An AE sensor was developed by use of a fiber-optic cantilever and an extrinsic Fabry-Perot interferometer(EFPI). The efficiency of signal processing was improved by driving the high frequency AE signals into the low frequency ones. In order to verify the developed sensor, the tensile and the pencil lead fracture(PLF) tests were performed including the experiment showing the Kaiser effect. From tests, AE signals were successfully detected in the elastic-plastic deformation range, especially higher signals at the crack propagation. The developed sensor is expected to be used for an on-line monitoring of crack propagation in mechanical systems.
Sub-Surface Crack Detection by Using Laser Induced Transient Stress Wave Propagation
Authors: Park Won Su , Lee Joon Hyun , Cho Youn Ho
Published: March 2009

In this study we attempt to investigate the possibility of detecting sub-surface crack and the understanding of the propagating phenomena of transient stress waves due to impact in thick aluminum plate by the simultaneous measurement of longitudinal and shear creeping and Rayleigh wave resulted from the mode conversion of laser induced transient stress wave impact. The propagation of the transient stress wave generated by laser irradiation is affected by the sub-surface crack and the result is analyzed. It was observed that the longitudinal and shear creeping wave velocities are varied depending on the depth of sub-surface crack. In addition, the variation of
amplitude ratio generated by propagating the stress wave is investigated. The longitudinal creeping wave velocity in the presence of the sub-surface crack is somewhat faster than in case of non-crack. And the shear creeping wave velocities represent large variations which are shown nearly 2nd order quadratic curve shape as the sub-surface crack depth increase under the same experimental condition.
The results of this study are very useful for the nondestructive evaluation of the surface layer in thick structures by non-contact method and the opposing and the structures difficult to access.
Development of Eddy Current Test for the Fatigue Behavior in Carbon/Epoxy Tube
Authors: Kim Cheol Woong , Song Sam Hong , Yoon Kwang Joon , Lee Jeong Soon , Ann Houng Kun , Jang Kwan Seob , Um Tae Gun
Published: March 2009

The researches using the Eddy Current Test (ECT) were limited for the particle reinforced metal base composites. It had been impossible to inspect the eddy current since the carbon/epoxy tube had the low electric conductivity of resin layer. However, it has been successful for our previous research to inspect the defect using the EC. In the case of loading to carbon/epoxy tube, the researches of relationship between the failure behavior and the variation of EC signals have not been carried out. Therefore, this research focused on the comparison and the evaluation of the EC signals according to the variation of the defect depth using the unloading and the radial-loading carbon/ epoxy tube. We obtained results are as follow. Firstly, reviewing the stress distribution of carbon/ epoxy tube under the radial-loading, it was known that the defect depth did not have strongly influence on the stress distribution. Therefore, it was believed that the stress distribution was not
directly related to the signals of the EC. Secondly, the EC signals similar to that of the unloading specimens could be obtained from the radial-loading specimen of 80 % defect depth. Thirdly, regardless of the unloading and the radial-loading specimens, the defect of 80 % and 100 % depths had the similar phase angles and Lissajous figures. Finally, it was guessed that the length of microcracks distributed at the whole specimens under the radial-loading was less than 60 % defect depth.
Ultrasonic Detection of Fiber Orientation in Composite Laminates for Use of Vehicular Structures
Authors: Park Je Woong , Im Kwang Hee , Hsu David K. , Na Seung Woo , Kim Young Nam , Yang In Young
Published: March 2009

The layup of a CFRP (carbon-fiber reinforced plastics) composite laminates affects the properties of the laminate, including stiffness, strength and thermal behavior. It is very important to detect ply error before the laminate is cured for both manual procedure and fiber placement procedure. An ultrasonic technique would be very beneficial, which could be used to test the part after and before curing laminates and requires less time than the optical test. Also cross-polarized scan is very sensitive to the layup errors and ply misorientations. Scanners were set out for different measurement modalities for acquiring ultrasonic signals as a function of in-plane azimuthal angle. Firstly, a manual scanner was built for making transmission measurements using a pair of normal-incidence shear wave transducers to find the effect of fiber misorientations of composite laminates. Also a method for nondestructively determining the ply layup in a composite laminate is presented. The method employs a normal-incidence longitudinal ultrasound to perform C-scan of ply interfaces of the laminate. And a ply-by-ply vector decomposition model has been utilized for evaluating layup errors in composite laminates fabricated from unidirectional plies. Test results between after and before curing laminates with model data were compared for a fiber orientation of the laminates.
A Nondestructive Testing Method for Crack in Carbon Fiber Reinforced Concrete with Infrared Thermography
Authors: Huang Li , Li Zhuo Qiu , Song Xian Hui
Published: March 2009

Based on the functional characteristics of carbon fiber reinforced concrete (CFRC), an improved infrared nondestructive testing method, to detect crack in CFRC by using infrared thermography, is presented in this paper. The principle is that when a CFRC specimen is applied a low voltage, crack existing in the specimen will result in non-homogeneous surface temperature distribution due to the electro-thermal effect of the material. Monitoring the temperature difference on the surface, the crack under the observed surface can be inspected by using infrared thermography. In theory, the mechanism causing the temperature difference comes down to an unsteady heat transfer problem with internal energy sources. In the case of the thermo-physical property of CFRC as given, the sensitivity of this method to the depth of the crack is analyzed by numerical computation.
Study on 2-D Multi-Fiber Arrange Model Composites
Authors: Moon Chang Kwon , Nam Ki Woo
Published: March 2009

The effect of interfiber distance on the interfacial properties in two dimensional multi-Eglass fiber/epoxy resin composites has been investigated using fragmentation test. In additions, the effect of the fiber surface treatment on the interfacial properties has been studied. We found that the interfacial shear strength decreased with the decreasing of the interfiber distance at the range of under 50µm and the extent of the decreasing was more serious as the increasing of the number of adjacent fiber. This is probably that the interface between the fiber and the resin was damaged by the adjacent fiber breaks and the damage increased with closing the interfiber spacing and the number of adjacent fiber. We can guess from this interfacial shear strength in real composites is much smaller than that of multi-fiber fragmentation sample with touched fiber. It was seen that the interfacial shear strengths saturated when the interfiber distance was over 50µm, the ones were saturated regardless of fiber surface treatment and the ones were in close agreement with those of the single fiber fragmentation test. Finally, the interfacial shear strength evaluated using two dimensional fragmentation tests are shown as real values in-site regardless of fiber surface treatment, interfiber distance and existing of matrix cracks.
Strength Diagnosis of Large Scale Structure Using Accelerometers
Authors: Lee Kwan Sup , Konovalov Serguei F.
Published: March 2009

A new diagnosis equipment is designed to examine the strength of large scale bridge. It is composed of three accelerometers, radio modem, and related electronics parts. Two accelerometers with high accuracy are used for measuring the change of inclination angle of the structure base and two horizontal components of structure vibration. The third accelerometer measures a vertical component of vibration. The equipment is installed in the sidewalk of some Moscow bridges as an
application. Several factors such as traffic load, wind, water wave, and etc. cause the vibration of bridge. By means of appropriate processing, the spectral characteristics of the bridge itself are determined. Several month’s test shows that the spectral characteristics remains constant if the bridge state keeps constant, and is changed by the change of the bridge state (for example, before and after
repair). If the measured inclination angle of the base is increased to a particular orientation, or the spectrum of bridge is changed, it is assumed that the sagging of the structure base or deformation of its structural members might happen. Periodic or continuous monitoring of the structure state under in-service condition with the help of this diagnosis equipment makes it possible to reveal the beginning of destructive changes in structural members and to prevent the occurrence of an
emergency. The study result could be applied to other large structures such as towers and buildings.
Simultaneous Health Monitoring and Vibration Control of Structures Using Smart Materials
Authors: Kim Myung Hyun , Kang Sung Won , Lee Jae Myung , Inman Daniel J.
Published: March 2009

Large welded structures, including ships and offshore structures, are normally in operation under cyclic fatigue loadings. These structures include many geometric as well as material discontinuities due to weld joints, and the fatigue strength at these hot spots is very important for the structural performance. In the past, various Non-Destructive Evaluation (NDE) techniques have been developed to detect fatigue cracks and to estimate their location and size. However, an important limitation of most of the existing NDE methods is that they are off-line; the normal operation of the structure has to be interrupted and the device often has to be disassembled. In this study, a new impedance-based structural health monitoring system employing piezoceramic transducers is developed with a special interest in applying the technique for welded structural members in ship and offshore structures. In particular, the impedance-based structural health monitoring technique that employs the coupling effect of piezoceramic (PZT) materials and structures is investigated.