bluuebunny/crossref_metadata_2025_split huggingface dataset:
EndoFEM Studies in the Mode I Stable Crack Growth of Fatigue Precracked CT Specimen
Authors: Lee C.F. , Lee K.L. 
Published: May 2011

AbstractIn this paper, the EndoFEM incorporated with a node duplicated and then unloaded crack extension methodology, is employed to produce the CT specimen of A1 2024-T3 with initial fatigue crack and then to simulate its stable crack growth under Mode I condition. Using the experimental P-LLD data, the P-Δa diagram can be estimated by the effective compliance method. This results in a further simulation of crack extending procedures which can obtain the stress-plastic strain distributions of growing crack front and their crack opening profiles, CTOD and CTOA vs. Δa Diagram, COD and COA measured at 5 positions behind the original crack tip vs. Δa diagram. The results mentioned above have excellent agreements with results of related experiments and other computational simulations.In consequence, the paper proposes a single fracture parameter of crack growth which can be casted in the future studies of EndoFEM simulation: (1) Within the crack initiation range whose crack extension rates da/dP has the lowest constant value, the COA measured at 0.5mm behind the original crack tip is takes as 5°; (2) Within the stable crack growth region whose crack extension rates are nonlinearly and monotonically increasing with finite values, the COA measured at 1mm behind the current crack tip is also taken as 5°.
Heat Transfer of an Electrically Conducting Viscoelastic Fluid Over a Stretching Sheet
Authors: Liu I-C. , Kong C.-H. 
Published: May 2011

AbstractThe solutions for flow and heat transfer in a steady laminar boundary layer flow are presented analytically for an electrically conducting viscoelastic fluid, subject to a transverse uniform magnetic field, past a semi-infinite stretching sheet. The temperature profiles and thermal characteristics at the wall are drawn and tabulated for selected parameters with prescribed surface temperature (PST) and prescribed surface heat flux (PHF) conditions. We also give the asymptotic solutions for temperature when the Prandtl number is very large. It is found that the inclusion of Joule heating has a significant influence on the thermal characteristics at the wall and the wall heat transfer strongly depends on the Prandtl number Pr as well as the Eckert number Ec. The heat flow may transfer from the fluid to the wall when Ec is large rather than from wall to the fluid when Ec is small. A physical argument about the thermal characteristics at the wall is proposed.
Wrinkling of a Debonded Initially Compressed Si1−XGex Film
Authors: Fedorchenko A. I. , Wang A.-B. , Mashanov V. I. , Cheng H.-H. 
Published: May 2011

AbstractA compressively strained pseudomorphic Si1−xGex film being debonded from Si substrate by selective etching forms wrinkles with a uniform space periodicity. The present study provides experimental evidences and a theoretical model for the wrinkling process. To allow large deflection, non-linear Von Karman plate theory is employed. The amplitude and wavelength of wrinkles are determined by minimizing the total free energy of a debonded wrinkled film. The wrinkling analysis has shown that the amplitude and wavelength of wrinkled film are an outcome of a subtle compromise between bending energy, and normal and shearing components of the stretching energy. The wave number nondimentionalized over the depth of etch is a function of the membrane strain of a bonded film, Poisson's ratio, and the nondimensional film thickness.
Prediction of Cutting Forces in Milling Stainless Steels using Chamfered Main Cutting Edge Tool
Authors: Chang C.-S. 
Published: May 2011

AbstractTo study the cutting forces, the carbide tip's surface temperature, and the mechanism of secondary chip and main chip formation of face milling stainless steel with a chamfered main cutting edge has been investigated. Theoretical values of cutting forces were calculated and compared to the experimental results with SUS 304 stainless steel plate as a workpiece material. Force data from these tests were used to estimate the empirical constants of the mechanical model and to verify its prediction capabilities. A comparison of the predicted and measured forces shows good agreement. A preliminary discussion is also made for the design of special tool holders and their geometrical configurations. Next, the tips mounted in the tool holders are ground to a chamfered width and the tool dimensions are measured by using a toolmaker microscope.
Spatiotemporal Intermittency Measurements in a Gas-Phase Near-Isotropic Turbulence Using High-Speed Dpiv and Wavelet Analysis
Authors: Yang T. S. , Shy S. S. , Chyou Y. P. 
Published: May 2011

AbstractRecently, Shy and his co-workers developed a new turbulent flow system that used a pair of counter-rotating fans and perforated plates to generate stationary near-isotropic turbulence, as verified by LDV measurements, for the study of premixed turbulent combustion processes. This paper evaluates for the first time the correlations between spatial and temporal properties of small-scale intermittency in such a fan-stirred near-isotropic turbulence. These spatiotemporal properties are obtained simultaneously via high-speed digital particle image velocimetry together with wavelet analyses. It is found that the wavelet energy spectra in the inertial range of near-isotropic region all exhibit a slope of nearly −5/3 which spans at least from 3Hz to 100Hz. Characteristic scales, including the integral time and length scales, Taylor microscales, and viscous dissipation scales, are identified without the use of Taylor hypothesis. Thus, a direct evaluation of Taylor hypothesis in near-isotropic turbulence with zero mean velocity can be made. From variations of the flatness factor, equivalent to the 4th order velocity structure function, in the spatial and time domains, it is found that the characteristic spatial and temporal intermittent scales of intense vorticity structures in the dissipation range of the fan-stirred near-isotropic turbulence occur around 5 ∼ 8η and τk, respectively, where η and τk are the Kolmogorov length and time scales. These results are useful for further study of particle settling in turbulence, a problem of both engineering and geophysical interest.
Dielectric and Mechanical Loading Effects of a Fluid on Lamb Waves Propagating in an Immersed Piezoelectric Plate
Authors: Yang C.-H. , Lai Y.-A. 
Published: May 2011

AbstractThis research is focused on exploring the fluid loading effects on the dispersion curves of Lamb modes propagating in a piezoelectric plate. A theoretical treatment based on a partial wave analysis is developed to model the dispersion curves of Lamb modes propagating in an X-LiNbO3 plate loaded by a fluid with combined mechanical/dielectric properties. In particular, the mode-shifting characteristics caused by the fluid loading as a function of the propagation orientation are illustrated with numerical examples. Finally, for the case of water as an immersing fluid, individual attributions of the mechanical and dielectric loading effects causing the mode-shifting are analyzed. It is found that the dielectric loading effect dominates the mode-shifting while the mechanical density loading can be neglected while Lamb waves propagate in an X-LiNbO3 plate immersing in water. The current results provides useful information for the applications of acoustic plate mode (APM) devices used in liquid sensor applications.
Broadband Dispersion Behaviors of Wedge Waves Propagating Along Large-Angled Wedges
Authors: Yang C.-H. , Tsai K.-Y. 
Published: May 2011

AbstractBroadband dispersion behaviors of wedge waves traveling along large-angled wedges are investigated with a laser ultrasound technique. Wedge waves are guided acoustic waves propagating along wedge tips. Until now, no elasticity-based close-form solution is available for the prediction of dispersion behavior of wedge waves. By assuming the wedge as a thin plate with variable thickness, McKenna obtained a theoretical approximation for the prediction of dispersion relation of truncated wedges within limited apex angle and bandwidth. The current research provides experimental data on wideband dispersion spectra of wedge waves traveling along large-angled wedges. It is found that the thin plate theory is accurate only within a small wavenumber regime. Also, a limiting behavior in the large wavenumber regime the ASF dispersion spectra are found to approach the Rayleigh wave speed.
Forming Limits Prediction of the Sheet Metal Forming Process by the Energy-Based Damage Model
Authors: Yeh H.-Y. , Cheng J.-H. 
Published: May 2011

AbstractAn energy-based damage model is proposed and applied to predict the fracture initiation of the sheet metal forming process. The fracture mechanism is investigated through the plastic energy dissipation. The concepts of the damaging work and the fracture energy are proposed for the quantitative description of damage evolution and crack initiation. The developed formulations are implemented into the finite element program ABAQUS to simulate the biaxial stretching of sheet metals and to predict the fracture strains. The material parameter needed in the damage model for fracture prediction is determined by the stress-strain history of the uniaxial tensile test. The forming limits for aluminum alloy sheets under various strain paths are predicted by the present approach and then compared to the measured data quoted from the literatures [1,2]. Good agreements are found between this study and the previous results.
On the Almansi-Michell Problems for an Inhomogeneous, Anisotropic Cylinder
Authors: Lin H.-C. , Dong S.B. 
Published: May 2011

AbstractA semi-analytical finite element (SAFE) method is presented for constructing solutions for an arbitrarily loaded cylinder, whose cross-section is general in terms of its shape and the number of distinct, perfectly bonded elastic, rectilinear anisotropic materials. The surface traction and body force loads need to be expressed in a power series of the axial coordinate. Linear three-dimensional theory is used. For a homogeneous isotropic cylinder, it is known as the Almansi-Michell problem, and the SAFE analysis herein is an extension to inhomogeneous, anisotropic bodies. By SAFE, the cross-section is discretized. The displacement field is expressed by interpolation functions over the cross-section and by analytical functions axially. The method herein is an extension of the authors' previous method cylinder with a general cross-section. Herein, the SAFE solution procedure is given and numerical examples will be presented.
Equivalent Fixed-Base Model for Soil-Structure Interaction Analysis
Authors: Chen C.-H. , Hsu S.-Y. 
Published: May 2011

AbstractThis paper is to investigate the effects of Soil-Structure Interaction (SSI) on the dynamic response of a soil-structure system. An ideal model with a simple structure supported on elastic half space is utilized to derive the factor FSSIthat can completely represent the effects of SSI. This factor is able to characterize both the change of predominant frequency and damping ratio of the system when compared to the conventional rigid-base type structural analysis. Based on that, an Equivalent Fixed-Base (EFB) model, which takes the effects of SSI into account, can be constructed. The Hualien field test results are then used to verify the applicability of the proposed EFB model.
Master Curve of Creep in Polymeric Off-Axis Composite Laminates
Authors: Hu H-W. 
Published: May 2011

AbstractAn approach to establish a master curve for effective creep compliances of polymeric off-axis composites with various fiber orientations was presented. Carbon/epoxy composite IM7/977–3 was used to fabricate four types of off-axis specimens and then subjected to momentary creep tests after a period of initial aging. Creep compliance and elastic compliance were separated from the total compliance. Using one-parameter creep potential theory, creep compliances were transformed to effective creep compliances. After choosing a proper value for the one-parameter, all effective creep compliances with various off-axis fiber orientations were superposed into a master curve. This master curve enables us to obtain creep compliance with any off-axis fiber orientation by testing only one off-axis specimen.
Numerical Simulations of a Miscible Drop in a Spinning Drop Tensiometer
Authors: Chen Ching-Yao , Liu K.-T. 
Published: May 2011

AbstractThe present investigation addresses the estimation of the unconventional effective interfacial tension (EIT), the so-called Korteweg stress, for a miscible interface. Two independent characteristic estimations are calculated: (1) the measurement based on a Spinning Drop Tensiometer (SDT) commonly applied in an immiscible situation, and (2) the theoretical predication involving an unknown physical constant (Korteweg constant) and detailed concentration distributions. Excellent agreements between these two estimations are found. By demonstrating the excellent agreement between these two proposed measurements, the applicability of a SDT for measuring miscible EIT is numerically verified. This numerical conclusion provides a possible simple method for further estimations of currently unknown physical constants.
Nondestructive Evaluation of In-Isolation Pile Shaft Integrity by Wigner-Ville Distribution
Authors: Ni S.-H. , Charng J.-J. , Lo K.-F. 
Published: May 2011

AbstractThe Wigner-Ville Distribution is a new numerical analysis tool for signal process technique in the time-frequency domain and it can offer assistance and enhance signal characteristics for better resolution both easily and quickly. Time-frequency transform can describe how a spectrum of signals changes with time owing to defects and boundary conditions. In this study, five single pre-cast concrete piles have been tested and evaluated by both sonic echo method and Wigner-Ville distribution (WVD). The appropriateness of time-frequency domain analysis is discussed. Furthermore, two difficult problems in nondestructive evaluation problems are discussed and solved: the first one is with a pile with slight defect, whose necking area percentage is less than 10%, and the other is a pile with multiple defects. The results show that WVD can not only recognize the characteristics easily, but also locate the defects more clearly than the traditional pile integrity testing method.
Mechanics of Matrix Cracking in Bonded Composites
Authors: Chiang Y.-C. 
Published: May 2011

AbstractIn this paper, a general matrix cracking model including the effect of fiber/matrix debonding in the crack wake is developed for a unidirectional fiber reinforced composite. The debonding mechanics is incorporated into matrix cracking model by treating the crack-wake debonding as a particular crack propagation problem along the interface. Then, the closed-form analytical solution of the critical stress for the onset of widespread matrix cracking is derived, based on the analysis of steady state crack growth in the matrix. The fracture mechanics approach adopted in the present analysis is compared with the analysis in which the crack-wake debonding mechanics was modeled by energy balance approach. The conditions for attaining no-debonding and debonding as onset of widespread matrix cracking are discussed in terms of the interfacial properties of debond toughness and frictional shear stress. The theoretical results are compared with experimental data that are available in the literature.
Failure Probabilities of Reinforced Concrete Square Pile Caps
Authors: Lu W.-Y. 
Published: May 2011

AbstractAn analytical model for determining the shear strength of concrete pile caps under the failure mode of diagonal-compression originally based on the softened strut-and-tie model is proposed. The failure probabilities of reinforced concrete pile caps are investigated by Monte Carlo method. The results indicate that the proposed model can accurately predict the shear strength of the pile caps. The distribution of the failure probabilities for pile caps designed to ACI 318-02 Appendix A and the proposed design method are more uniform than that designed to the ACI 318-99. The ACI 318-99 is very conservative and cannot provide a consistent safety for pile caps design. It is suggested that the procedures in the ACI 318-02 Appendix A should be moved to the main body of ACI 318-02 and the proposed design method should be incorporated into the current reinforced concrete pile cap design methods.
Velocity-Vorticity Formulation for 2D Natural Convection in an Inclined Cavity by the DQ Method
Authors: Lo D. C. , Liao T. , Young D. L. , Gou M. H. 
Published: May 2011

AbstractThe aim of this paper attempts to apply the differential quadrature (DQ) method for solving two-dimensional natural convection in an inclined cavity. The velocity-vorticity formulation is used to represent the mass, momentum, and energy conservations of the fluid medium in an inclined cavity. We employ a coupled technique for four field variables involving two velocities, one vorticity and one temperature components. In this method, the velocity Poisson equation, continuity equation, vorticity transport equation and energy equation are all solved as a coupled system of equations so as to we are capable of predicting four field variables accurately. The main advantage of present approach is that coupling the velocity and the vorticity equations allows the determination of the boundary values implicitly without requiring the explicit specification of the vorticity values at the boundary walls. A natural convection in a cavity with different angle of inclinations for Rayleigh number equal to 103, 104, 105 and 106 and H/L aspect ratios varying from 1 to 3 is investigated. It is shown that with the use of the present algorithm the benchmark results for temperature and flow fields could be obtained using a coarse mesh grid.
Morphological Instabilities in Time Periodic Crystallization
Authors: Chung C. A. , Chien W. Z. , Hsieh Y. H. 
Published: May 2011

AbstractA linear stability analysis is performed on the interface that forms during directional solidification of a dilute binary alloy in the presence of time-periodic growth rates. The basic state, in which the flat crystal-melt interface advances at a steady rate with an oscillation superimposed, is solved analytically by expanding the governing equations in terms of the assumed-small amplitude of modulation. We find that there is a frequency window of stabilization, in which the Mullins-Sekerka instability can be stabilized synchronously. Outside of the window, large input frequencies may destabilize the Mullins-Sekerka mode. The subharmonic mode, which occurs with small wave numbers, is stabilized with increasing the frequency. As for the modulation amplitude, larger amplitude tends to reduce the synchronous mode while enhance the subharmonic mode.
Entropy Generation of Free Convection Film Condensation From Downward Flowing Vapors onto a Cylinder or Sphere
Authors: Dung S. C. , Tzeng S. H. , Yang S. A. 
Published: May 2011

AbstractThis study aims at analyzing entropy generation rate of saturated vapor flowing slowly onto and condensed on an isothermal sphere/horizontal cylinder. We derive an expression for entropy generation, which accounts for the resultant action of specified irreversibilities of film-wise condensation outside a cylinder/sphere. The result shows that local entropy generation rate increases with Brinkman group parameters. As Rayleigh group parameters increase, dimensionless heat transfer coefficient is enhanced, but entropy generation number is augmented too. Heat transfer irreversibility dominates over the film flow friction irreversibility in the upper half of a sphere, and vice versa for the lower half of a sphere. As for a cylinder, heat transfer irreversibility dominates over film flow friction irreversibility except around the middle way of streamwise length for the cases of Brinkman group parametersBr/ ψ≥ 0.75.
Experimental Study of Coal Pyrolysis and Gasification in Association with Syngas Combustion
Authors: Chen W.-H. , Chen J.-C. , Tsai C.-D. , Du S.-W. 
Published: May 2011

AbstractCoal pyrolysis and gasification incorporating synthesis gas (syngas) combustion are investigated experimentally in the present study. Two different coals are considered; one pertains to high-volatile bituminous and the other low-volatile one. For the pyrolysis, using thermogravimetry in association with mass spectrometry reveals that the concentrations of CO and CO2 increase with increasing temperature, whereas those of H2 and CH4 undergo increase followed by decrease. Regarding the gasification, the formations of the four gases between the two different coals are similar. However, when the reaction temperature is relatively low such as 800°C, carbon reactivity of the low-volatile coal decays in a significant way. Furthermore, with the reaction temperature of 1000°C the entire gasification histories of the two coals can be divided into five periods in accordance with syngas combustion. They are initiated, growing, rapidly decaying, progressively decaying, and frozen periods, sequentially. The flame is wrinkled in the growing and rapidly decaying periods where the reaction strength is much higher than that near extinction. When the reaction temperatures are 800 and 900°C, the growing and rapidly decaying periods tend to wither. Recognizing the syngas combustion characteristics, one is capable of figuring out the coal gasification process in more detail.
Effect of Interface Anisotropy on Elastic Wave Propagation in Particulate Composites
Authors: Hasheminejad S. M. , Maleki M. 
Published: May 2011

ABSTRACTThe scattering of time harmonic plane longitudinal and transverse elastic waves in a composite consisting of randomly distributed identical isotropic spherical inclusions embedded in an isotropic matrix with anisotropic interface layers is examined. The interface region is modeled as a spherically isotropic shell of finite thickness with five independent elastic constants. The Frobenius power series solution method is utilized to deal with the interface anisotropy and the effect of random distribution of particulates in the composite medium is taken into account via a recently developed generalized self-consistent multiple scattering model. Numerical values of phase velocities and attenuations of coherent plane waves as well as the effective elastic constants are obtained for a moderately wide range of frequencies, particle concentrations, and interface anisotropies. The numerical results reveal the significant dependence of phase velocities and effective elastic constants on the interface properties. They show that interface anisotropy can moderately depress the effective phase velocities and the elastic moduli, but leave effective attenuation nearly unaffected, especially at low and intermediate frequencies. Limiting cases are considered and good agreements with recent solutions have been obtained.
A Factorization Algorithm for Wave Propagation in Periodic Structures with Application to Torsional Waves in an Infinite Cylinder
Authors: Barone R.C.A. , Kaul R.K. 
Published: May 2011

ABSTRACTIn this paper we introduce a fundamentally new concept in the field of wave-propagation in periodic structures. We show that a phenomenal amount of simplification can be achieved by using symmetry arguments. Problems which ordinarily lead to (2n × 2n) determinantal eigenvalue equations, can effectively be reduced to two (n × n) determinantal equations. We state the final result in the form of a factorization theorem and then with the help of a simple problem, we show the superiority of this new result over the traditional methods of solution.