bluuebunny/crossref_metadata_2025 huggingface dataset:
Prediction of Cutting Temperatures in Turning of Glass Fiber Reinforced Plastics (GFRP) Materials
Authors: Chang C.-S. , Lin Y.-L. , Hwang B.-C.
Published: May 2011

Thirty six kinds of chamfered and unchamfered main cutting edge carbide tips were used in turning of high-strength glass-fiber-reinforced plastics (GFRP) materials to study the cutting temperature of tip's surface. The frictional forces and heat generated on elementary cutting tools are calculated by using the measured cutting forces and the theoretical cutting analysis. The heat partition factors between the tip and chip are solved by using the inverse heat transfer analysis, which utilizes temperature on the K type carbide tip's surface measured by infrared as the input. The tip's surface temperature of the carbide is solved by finite element analysis (FEA) and compared with those obtained from experimental measurements. A good agreement demonstrates the accuracy of the proposed model.
Scattering of Elastic Waves by a Buried Tunnel Under Obliquely Incident Waves Using T Matrix
Authors: Liao W.-I. , Yeh C.-S. , Teng T.-J.
Published: May 2011

This paper first studies the transition matrix formulation for the analysis of responses of an elastic halfspace with a buried tunnel subjected to obliquely incident waves. The basis functions are constructed using the moving P-, SV-, and SH-wave source potentials and to represent the scattered and refracted wave fields in series forms. The associated T-matrix expression of elastic inclusion is derived using Betti's third identity. Second, this study proposes a technique for calculating the integral representation of basis functions in the wave-number domain using the method of steepest descent. Finally, typical numerical results obtained under incident plane waves are presented for verification.
Characteristics of Hydraulic Shock Waves in an Inclined Chute Contraction - Experiments
Authors: Jan C.-D. , Chang C.-J. , Lai J.-S. , Guo W.-D.
Published: May 2011

This paper presents the experimental results of the characteristics of hydraulic shock waves in an inclined chute contraction with consideration of the effects of sidewall deflection angle φ, bottom inclination angle θ and approach Froude number Fr0. Seventeen runs of laboratory experiments were conducted in the range of 27.45° ≤φ≤ 40.17°, 6.22°≤ θ ≤ 25.38° and 1.04 ≤ Fr0 ≤ 3.51. Based on the experimental data, three empirical dimensionless relations for the shock angle, maximum shockwave height, and corresponding position of maximum shockwave were obtained by regression analyses, respectively. These empirical relations would be useful for hydraulic engineers in designing chute contraction structures.
Dual Reciprocity Singular Hybrid Boundary Node Method for Solving Inhomogeneous Equations
Authors: SiMa Y. Z. , Zhu H. P. , Miao Y.
Published: May 2011

Based on the radial basis function (RBF) and the singular hybrid boundary node method (SHBNM), this paper presents an inherent meshless, boundary-only technique, which names dual reciprocity singular hybrid boundary node method (DRSHBNM), for numerical solution of various inhomogeneous equations. In this study, the RBFs are employed to approximate the inhomogeneous terms via dual reciprocity method (DRM), while the general solution is solved by means of SHBNM, in which only requires discrete nodes constructed on the boundary of a domain, while several nodes in the domain are needed for the RBF interpolation. The treatment of singularity integration and the 'boundary layer effect' have been given by a series of effective approaches. Numerical examples for the solution of inhomogeneous equations show that high convergence rates and high accuracy with a small node number are achievable.
An Effective Approach for Calculation of Exhaust Pipe Flows
Authors: Liang S.-M. , Tsai S.-J. , Wang S.-F.
Published: May 2011

In this study an effective numerical approach is proposed for calculation of exhaust pipe flows. The flow inside an exhaust pipe is very complicated, since that flow involves pulsating hot gases with blast waves discharged from an internal combustion engine. In order to accurately simulate the complicated pulsating flow with the effects of heat transfer and friction at the duct wall, two systems of quasi-onedimensional model equations are employed, which resulted from the governing equations of the mass, momentum and energy conservation. One system of model equations with the terms of heat loss and wall friction results from the dimensionless governing equations based on dimensionless time variable t1 where t1 is defined as the dimensional time divided by the ratio of the pipe length to the time-average flow velocity at the pipe inlet. This system of model equations is numerically solved for a steady exhausted gas-flow without blast waves. The computed steady flow is referred as a basic flow. The other system of model equations without the terms of heat loss and wall friction results from the dimensionless governing equations based on dimensionless time variable t2, where t2 is defined as the dimensional time divided by the ratio of the pipe length to the speed of sound at the pipe inlet. The latter model is used for predicting exhausted gas-flows with blast waves. These two systems of model equations are solved by a th-order weighted essential non-oscillation scheme. It is found that the computed result of the peak pressures, temperature, and flow velocity at some check points for an exhaust pipe at different engine speeds agrees reasonably well with experimental data.
Characteristics of Reliability-Dependent Hazard Rate for Composites Under Fatigue Loading
Authors: Chen C. L. , Tsai Y. T. , Wang K. S.
Published: May 2011

This paper studies the characteristics of a proposed reliability-dependent hazard rate function for composites under fatigue loading. The hazard rate function, in terms of reliability R, is in the form of e+c (1-R)p called (ecp) model, where e denotes the imbedded defects of material strength, c the coefficient of strength degradation, and p the memory characteristics of distributions of both applied stress and fatigue strength during the cumulative damage process. By taking a typical residual strength model in Monte Carlo simulation, this paper presents the time changing of the residual strength distribution and hazard rate of composite under various constant-amplitude cyclic stresses. The values of (e, c, p) are decided by fitting hazard rate function to the data generated in simulation. The results show that, under a suitable suggested value of e, p is a constant depending on the characteristics of stress distribution as well as the residual strength model used in Monte Carlo stimulation, and c is correlated to the maximum cyclic stress in a power-law relationship. Only by knowing the initial strength distribution and the maximum cyclic stress, the fatigue life can be easily estimated by integrating the reliability with time or its equivalent, i.e., the reciprocal of hazard rate function with reliability. Finally, by a proposed approximated equation of fatigue life, the (ecp) model is checked to be highly consistent with S-N curve in both the physical means and the equation form. The analysis presented here may be helpful in designing and maintenance planning of composite under fatigue loading.
Acoustic Transmission Through Cylindrical Shells Treated with FLD Mechanisms
Authors: Daneshjou K. , Talebitooti R. , Nouri A.
Published: May 2011

Analytical study is conducted in this paper to understand the characteristics of sound transmission through cylindrical shell with free layer damping (FLD) treatment. It is assumed an infinitely long circular cylindrical shell subjected to a plane wave with uniform airflow in the external fluid medium. The damping layer applied on the surface of the shell is represented by HN model with frequency-dependent specifications. An exact solution is obtained by solving the Markus equations of FLD shells and acoustic wave equations simultaneously. As the pressure and displacement terms are expressed in series form, an iterative procedure is founded to cut them with an appropriatenumber of modes. Transmission losses obtained from the solution are compared with “modal-impedance method” for an especial case of untreated shell. Eventually, the numerical results show the effects of stiffness, loss factor and thickness of damping material, and also incident wave angles on TL curves.
Numerical Simulation of Blast-Wave Propagation in a Small Two-Medium Duct
Authors: Liang S.-M. , Yuan J.-C.
Published: May 2011

In this study, a small two-medium duct with blast-wave propagation is numerically investigated by a high-resolution Euler/Navier-Stokes solver. The solver has a feature of treatment of the Tait equations of state for two media. One of the two media is water which is envisaged as a blood. The second medium is another liquid, used to simulate body's clot or tissue. The duct wall has a mass diffusion effect in addition to viscous effects. Since two different media are considered, the reflection and transmission of an underwater blast wave passing through the interfaces of the two media with different sound impedances are inevitable. The different properties of liquids may cause numerical oscillation at interfaces for very weak blast waves for a high-resolution scheme such as a 5th-order WENO scheme. In order to overcome this difficulty of numerical fictitious oscillation, a third-order WENO scheme was used. It was found that computed pressures of the transmitted blast wave for four kinds of simulated tissues are in good agreements with those obtained by the acoustic principle. Moreover, for the case of a simulated clot, the pressure force and impulse acted on the clot surface are investigated for different intensities of blast waves.
A Study of Sewing Ring Geometry on Wall Shear Stress of Implanting Bi-Leaflet Aortic Valves, Using Computational Fluid Dynamics
Authors: Hsu C.-H.
Published: May 2011

This paper concentrates on the wall shear stress discussion of implanting bi-leaflet aortic valve and concludes a better valve design. To simulate the haemodynamic characteristics of the blood flow, ANSYS CFX10.0 software was utilized to analyze the three-dimensional Reynolds-averaged Navier-Stokes equations. With a quasi-steady analysis model, we predict values of the blood velocity and the wall shear stress both over the valve leaflets and the endothelial lining. Analysis results highlight that leaflet opening angle and valve geometry affect the shear stress distribution and vortex flow regime. An analysis of haemodynamic study for the St. Jude valve with various openingangles is presented first and the sewing ring geometry change is then recommended. It is found that the wall shear stress decreases significantly after modifying the sewing ring geometry. Maximum shear stress reduces 18.5% compared to that of the original St. Jude model at peak systole. This would ease possible damage of endothelial lining of the aorta.
Editorial Retraction of a Paper
Authors: Wu Kuang-Chong
Published: May 2011

A Simple Model to Predict Critical Ricochet Angle in Long-Rod Penetration by Kamran Daneshjou and Majid Shahravi was published in Journal of Mechanics in the March issue of 2009 (Vol. 25, No. 1, pp. 117-128).
Study of Nanoscale Pressure-Driven Electrokinetic Flow with Effects of Wall Lattice Plane
Authors: Yen T.-H. , Soong C.-Y. , Tzeng P.-Y.
Published: May 2011

The objective of the present study is to explore pressure-driven flows with the presence of electric double layer (EDL) in nanochannels of various wall lattice planes. Three face-centered cubic (fcc) lattice planes, i.e. fcc(111), fcc(100), and fcc(110), of the channel wall are considered. The structure of diffuse EDL and electrokinetic flow characteristics are dealt with in an atomistic view. Fluid and charge density layering phenomena and their influences on the Stern layer are investigated with the molecular dynamic simulation results. In most of the simulations, a monatomic molecule, W, is used as the solvent model and the charged particles W+ and W− of the same size as the ions. To examine behaviors of the dissimilar particles, a simulation with the aqueous model W for fluid, Na+ for cation and Cl− for anion is also performed. Effects of ion concentrations, wall-fluid interaction energy, and surface charge density on the electro-hydrodynamics are studied. In addition, based on the continuum theory, two analytic expressions for zeta potential with the presence of fluid slippage are derived and analyzed. The present results disclose interesting physics about the influences of wall lattice-fluid interactions, which are significant in further understanding and applications of the nanoscale electrokinetic flows.
Closed-Form Approximate Formulas for Torsional Analysis of Hollow Tubes with Straight and Circular Edges
Authors: Doostfatemeh A. , Hematiyan M. R. , Arghavan S.
Published: May 2011

Some analytical formulas are presented for torsional analysis of homogeneous hollow tubes. The cross section is supposed to consist of straight and circular segments. Thicknesses of segments of the cross section can be different. The problem is formulated in terms of Prandtl's stress function. The derived approximate formulas are so simple that computations can be carried out by a simple calculator. Several examples are presented to validate the formulation. The accuracy of formulas is verified by accurate finite element method solutions. It is seen that the error of the formulation is small and the formulas can be used for analysis of thin to moderately thick-walled hollow tubes.
Mathematical Approach to Investigate the Behaviour of the Principal Parameters in Axisymmetric Supercavitating Flows, Using Boundary Element Method
Authors: Shafaghat R. , Hosseinalipour S. M. , Nouri N. M. , Vahedgermi A.
Published: May 2011

In this paper, a direct boundary element method (DBEM) is formulated numerically for the problems of the unbounded potential flows past supercavitating bodies of revolution (cones and also disks which are special case of cones with tip vertex angle of 180 degree) at zero degree angle of attack. In the analysis of potential flows past supercavitating cones and disks, a cavity closure model must be employed in order to make the mathematical formulation close and the solution unique. In the present study, we employ Riabouchinsky closure model. Since the location of the cavity surface is unknown at prior, an iterative scheme is used. Where, for the first stage, an arbitrary cavity surface is assumed. The flow field is then solved and by an iterative process, the location of the cavity surface is corrected. Upon convergence, the exact boundary conditions are satisfied on the body-cavity boundary. For this work, powerful software, based on CFD code, is developed in CAE center of IUST. The predictions of the software are compared with those generated by analytical solution and with the experimental data. The predictions of software for supercavitating cones and disks are seen to be excellent. Using the obtained data from software, we investigate the mathematical behavior of axisymmetric supercavitating flow parameters including drag coefficients of supercavitating cones and disks, cavitation number and maximum cavity width for a wide range of cone and disk diameters, cone tip angles and cavity lengths. The main objective of this study is to propose appropriate mathematical functions describing the behavior of these parameters. As a result, among all available functions such as linear, polynomial, logarithmic, power and exponential, only power functions can describe the behavior of mentioned parameters, very well.
Thermosolutal Convection in An Annular Enclosure with Steps
Authors: Wang L. W. , Kung Y. C. , Chen Y. S. , Kang M. F. , Hsu F. C.
Published: May 2011

This study attempts to examine convection caused by the combined effects of temperature and concentration gradients in an annular enclosure with steps. An experimental study of thermosolutal convection of a CuSO4+ H2SO4+ H2O solution in a horizontal annular enclosure with steps is conducted using an electrochemical system that enables either opposing or cooperating in temperature and concentration gradients to be imposed. The shadowgraph recording technique is utilized to visualize and analyze the flow field phenomenon. The large difference between the thermal and solutal diffusion rates causes the flow to exhibit double-diffusive characteristics. In both cooperating and opposing cases, some finger-type flow can be visualized in the layered flow structure. Furthermore, Sh (mass transfer rate) increased with increasing Grt for fixed Grm and S*. Sh is larger in the cooperating case than in the opposing case for given Grt and Grm values.
Dimensional Effect of Micro Capillary Pumped Loop
Authors: Leu T.-S. , Huang N.-J. , Wang C.-T.
Published: May 2011

This study discusses the components' geometry and its effect on the capability of heat transmission and pressure drop because of its evident influence on the performance of micro capillary pumped loop (MCPL). On analyzing the dimensional effect on heat transmission and pressure gradient of MCPL device, some results were yielded and addressed as follows: The vapor line was the most important factor among the components of MCPL in heat transmission and pressure drop. Furthermore, the depth of vapor line was the main parameter because of its drastic effect. In addition, at depth of vapor line,hv, ranging from 20 μm to 150 μm, the amount of heat transferred for system will increase, but decrease the pressure drop. However, forhvlarger than 150 μm, the heat transfer and pressure drop both will reach a limit. A new family of geometrical dimensions of MCPL possessing an excellent heat flux of 178 W/cm2would be obtained. These findings will be useful in designing a better MCPL.
Random Outcome and Stochastic Analysis of Some Fatigue Crack Growth Data
Authors: Wu W. F. , Ni C. C. , Liou H. Y.
Published: May 2011

Fatigue crack propagation data of a batch of AISI 4340 steel specimens are released in the present paper. The statistical nature of the data is specially emphasized, and a probabilistic fracture mechanics model is introduced to analyze the data. The stochastic differential equation associated with the model is then solved. The solution gives us the crack exceedance probability as well as the probability distribution of the random time to reach a specified crack size. These quantities are useful in the reliability assessment of structures made of the tested material. Comparing the analytical result with the experimental result, it is found that the proposed probabilistic fracture mechanics model can reasonably explain the experimental data. For those data that cannot be fitted well by the proposed model, methods of improvement are proposed in the present paper as well.
Dynamic Analysis of Circular Plate on Elastic Foundation by EFHT Method
Authors: Wu Lai-Yun , Lee Wen-Haur
Published: May 2011

The dynamic response of a homogeneous, isotropic and elastic circular plate on an elastic foundation subjected to axisymmetric time dependent loads is investigated both analytically and numerically in thisv paper. First, the Extended Finite Hankel Transform (EFHT) is derived. After applying the technique of the EFHT to the governing equation of the vibrating circular plate, the governing partial differential equation (PDE) is transformed into the governing ordinary differential equation (ODE). Therefore, the analytical solution of the plate problem can be found completely. Once the dynamic response of the plate is solved, the internal forces of the plate, including shear force, bending moment and torsion, can be obtained subsequently. Under the particular case that elastic springs do not exist under the foundation, the dynamic response of the circular plate by the method of EFHT matches exactly with that by the method of modal analysis. By comparing the methods of EFHT, Boundary Element Method (BEM) and Finite Element Method (FEM), the results indicate that the proposed method of EFHT is accurate, systematic and convenient.
A Non-Iterative Direct Displacement-Based Design Procedure for SDOF Steel Columns: Using Substitute Structure
Authors: Lin Y.-Y. , Chang K.-C.
Published: May 2011

Traditionally, the yield displacement of a nonlinear structure was calculated by using the direct displacement-based seismic design method which usually requires a repeatedly iterative procedure no matter whether the substitute structure or inelastic design spectra has been adopted in the procedure. This will sometimes result in inefficiency if too many iterative cycles need to be produced in a design case for convergency. To avoid this disadvantage, this paper presents a non-iterative direct displacement-based design procedure for SDOF steel columns using the substitute structure approach. By combining the yielding property with the stiffness property of the designed steel columns, the procedure can immediately obtain the column's cross-section via the chosen target displacement and ductility ratio.
A Unified Creep-Cyclic Plasticity Theory of Endochronic Viscoplasticity with Applications in 304 Stainless Steel
Authors: Lee C. F. , Shen H. T. , Peng W. T.
Published: May 2011

In this paper, a unified creep-cyclic plasticity theory of endochronic viscoplasticity is established, in which the computations in the cyclic stress-strain responses of fatigue loading and the creep strain responses of general thermal/creep loading histories are integrated.

Based on the relationship of convolutional integral between the relaxation modulus function ρ(Z) and the creep compliance function J(Z), and the given functional form of ρ(Z) obtained from the cyclic hysteresis loop; an explicit functional form of J(Z) can be generated numerically which covers creep response from the primary creep stage to the steady creep stage. As a consequence, the conventional cyclic stress-strain curve, the Bailey-Norton creep law and the power law of steady creep rate are interrelated.

Four experiments of 304 stainless steel at about 0.52 homologous temperature and under constant or variable amplitude loading histories are investigated. The success in the unified computational methodology is demonstrated by the well agreement between the computational results and the experimental data.
Flow Bifurcation and Transition in a Gap Between Two-Rotating Spheres
Authors: Luo W.-J. , Yang R.-J.
Published: May 2011

This study investigates the flow bifurcation and transition between stable states in the gap between two concentric rotating spheres. A continuation method is used together with linear stability analysis to investigate the bifurcation structure of the discretized governing equations and to determine the stability of the calculated states. The constructed bifurcation diagram is used to illustrate the restricted range of Reynolds number within which each equilibrium state exists. The diagram also identifies the permissible transitions between these states and indicates their terminative states. In the present study, it is shown how appropriate control of the angular velocity of the outer sphere results in the evolution of the flow state through a series of permitted stable states. The time-dependent transitions between these states are investigated by means of a backwards-Euler time stepping formulation. The terminate state of transition process can also be used to confirm the stability of the flow. The flow evolution between each transition is illustrated by means of temporal sequences of the meridional streamlines and transition curves. The present results indicate that all the flow transitions in a gap between two rotating spheres are produced symmetrically with respect to the equator.
Instability Modal Behavior of the Acoustically Excited Impinging Plane Jet With a Small Cylinder
Authors: Hsiao Fei-Bin , Hsu I-Che , Hsu Cheng-Chiang
Published: May 2011

The Instability modal behavior of coherent structures in a jet-small cylinder impinging flow field is extensively studied by hot-wire anemometry measurements. The free jet is employed with a small cylinder of 3 mm in diameter located in the potential core region at the impinging length of L/H = 1.5 for the near field impingement and L/H = 4 for the far field impingement. The jet exit velocity is operated at 10 m/sec with the Reynolds number of 1.03 × 104 based on the nozzle exit width H = 15mm. The impinging jet is locally excited at the nozzle exit with varicose mode (m =0) and sinuous mode (m = 1) disturbances at the fundamental frequency of the natural jet flow. Data indicate that the jet flow is greatly altered and significantly enhanced by strengthening the coherent structures of the flow due to resonance according to the feedback mechanism. Although the original natural jet preferably exhibits the varicose mode, the strong sinuous mode is dominant in the flow field owing to the presence of the small cylinder in the potential core region. In the near field impingement, the wake region behind the cylinder preserves the pure sinuous mode to where the jet vortices merge and then mildly fades out. Whereas in the jet shear layer, the sinuous mode exists in the initial portion and gradually transforms to the varicose mode. In the far field impingement, the alternate mode dominates in each frequency stage in pure impinging case and the modal behavior follows the selected mode with the introducing acoustic waves in the acoustic excitation cases.
Two-Dimensional Incompressible Viscous Flow Simulation Using Velocity-Vorticity Dual Reciprocity Boundary Element Method
Authors: Eldho T. I. , Young D. L.
Published: May 2011

This paper describes a computational model based on the dual reciprocity boundary element method (DRBEM) for the solution of two-dimensional incompressible viscous flow problems. The model is based on the Navier-Stokes equations in velocity-vorticity variables. The model includes the solution of vorticity transport equation for vorticity whose solenoidal vorticity components are obtained by solving Poisson equations involving the velocity and vorticity components. Both the Poisson equations and the vorticity transport equations are solved iteratively using DRBEM and combined to determine the velocity and vorticity vectors. In DRBEM, all source terms, advective terms and time dependent terms are converted into boundary integrals and hence the computational domain of the problem reduces by one. Internal points are considered wherever solution is required. The model has been applied to simulate two-dimensional incompressible viscous flow problems with low Reynolds (Re) number in a typical square cavity. Results are obtained and compared with other models. The DRBEM model has been found to be reasonable and satisfactory.
A Unified Approach for the Kinematic and Force Analysis of Simple Wire-Driven Platform Mechanisms
Authors: Lin Y. L. , Liu T.
Published: May 2011

In the analysis of simple wire-driven platform (SWDP) mechanisms, the tension and the posture of each wire can be formulated, and expressed in an integrated screw representation naturally. In this study, a unified approach for analyzing the kinematics and kinetics of SWDP mechanisms based on the screw theory is proposed and developed, which includes the screw-based Jacobian, the static and dynamic equilibrium of wires and platform, and the singularity analysis. Via using the unified screw-based approach, the investigation on the characteristics of SWDP mechanisms, therefore, can be more efficient and simplified. An example is presented to demonstrate this unified approach.
Withdrawal of a Conical Pin From a Pool of Liquid
Authors: Wang A.-B. , Chen Y.-S. , Wu Y.-J. , Sung J.-Y. , Yarin A. L.
Published: May 2011

The development of biochips leads to a straightforward, fast and cost effective method to obtain valuable genetic information. A key element of the emerging biochip technology is a microarray system, which fabricates high-density samples on solid materials of a microscopic area. In particular, dots of test liquid are printed on solids by a system of pins constituting a microarray. At present, however, the technique cannot make dots of arbitrary equivalent and controllable size. On the other hand, printing pins in microarrays represent themselves as a particular example of dip coating. In the experiments of the present work, a model of tapered stainless steel needle was withdrawn from different glycerine-water mixtures. Thicknesses and volumes of the withdrawn liquid films were measured as a function of the needle geometry, immersion depth, withdrawal rate, and physical parameters of the liquid. The experimental data are analyzed as a function of the capillary number Ca based on the withdrawal speed and compared to the predictions of the modified Landau-Levich-Deryagin (LLD) theory. The results show that forCa< 10-2the thickness and the volume of the liquid follow theCa2/3-scaling, while forCa>10-2— theCa½-scaling, as it is expected from the LLD theory. Flow visualization is utilized to resolve the detail flow structure. The results put the key element of the pin-printing technology exploited in microarrays into a familiar hydrodynamic context of dip coating. This allows one to expect that under appropriate operational conditions, high-precision sampling could be attainable.
Electronic Speckle Pattern Interferometry Applied to the Displacement Measurement of Sandwich Plates with Single ‘Fully Potted’ Insert
Authors: Huang S. J. , Lin H. L.
Published: May 2011

The construction and operation of electronic speckle pattern interferometer (ESPI) applied to single-inserted sandwich plates have been earliest presented in this paper. Proposed ESPI has advantages of full-field and non-destructive testing, which can measures microscopic out-of-plane displacement in the elastic region without wasting specimen. For validation purpose, the finite element method (FEM) analysis was conducted. By comparing the results of ESPI and FEM displacement fields around the inserts that a convincing agreement is revealed. The effect of potting material diameter on the displacement of single-inserted sandwich plates was obtained by the ESPI and FEM.
A Microcontact Model Developed for Asperity Heights with a Variable Profile Fractal Dimension, A Surface Fractal Dimension, Topothesy, and Non-Gaussian Distribution
Authors: Liou J. L. , Lin J. F.
Published: May 2011

The cross sections formed by the contact asperities of two rough surfaces at an interference are islandshaped, rather than having the commonly assumed circular contour. These island-shaped contact surface contours show fractal behavior with a profile fractal dimension Ds. The surface fractal dimension for the asperity heights is defined as D and the topothesy is defined as G. In the study of Mandelbrot, the relationship between D and Ds was given as D = Ds + 1 if these two fractal dimensions are obtained before contact deformation. In the present study, D, G, and Ds are considered to be varying with the mean separation (or the interference at the rough surface) between two contact surfaces. The D-Ds relationships for the contacts at the elastic, elastoplastic, and fully plastic deformations are derived and the inceptions of the elastoplastic deformation regime and the fully plastic deformation regime are redefined using the equality of two expressions established in two different ways for the number of contact spots (N). The contact parameters, including the total contact force and the real contact area, were evaluated when the size distribution functions (n) for the three deformation regimes were available. The results indicate that both the D and Ds parameters in these deformation regimes increased with increasing the mean separation (d*). The initial plasticity index before contact deformation (ψ)0 is also a factor of importance to the predictions of the contact load (F*t) and contact area (At*) between the model of variable D and G, non-Gaussian asperity heights and circular contact area and the present model of variable D and G, non-Gaussian asperity heights and fractal contact area.
Dynamic Interaction of a Distributed Supported Guideway and a Asymmetrical Multimagnet Suspension Vehicle with Unbalanced Mass
Authors: Hu C.-Y. , Chen K.-C. , Chen J.-S.
Published: May 2011

This study investigates the steady state dynamic interactions between a vehicle and guideway of a high-speed ground transportation system based on magnetically levitated (Maglev) vehicles. The guideway is assumed to be made up of identical simply supported beams with single spans and rigid supports. The vehicle is considered two-dimensional, with numerous degrees of freedom representing the passenger cabin and primary and secondary suspensions of the vehicle with lumped masses, linear springs and dampings. The Bernoulli-Euler beam equation is utilized to model the characteristics of a flexible guideway, and the guideway synthesis is based on a modal analysis method. The dynamic behaviors of both vehicle and guideway are then simulated to investigate how the locations of the passenger cabin mass of center and asymmetric suspension characteristics of the vehicle suspensions influence high speed vehicle-guideway interaction. Finally, simulation results are compared. Results of this study provide basic design guidelines for Maglev vehicle-guideway systems.
A Cylindrically Anisotropic Tube Containing a Mixed Dislocation
Authors: Wang C.-H.
Published: May 2011

This study presents an analytical methodology for solving an elastic problem of a cylindrically anisotropic tube infused with eigenstrains. The general solutions for the particular case of a tube containing a mixed dislocation are also provided. The mainframe of this analysis is based on the state space formulation in conjunction with the theory of eigenstrain. By using the technique of Fourier series expansion and the theory of matrix algebra on solving the state equation, the expressions of solutions are not only explicit but also compact. The dislocation considered in this study is a mixed dislocation which can be viewed as a combination of edge dislocations and a screw dislocation. In order to strengthen the feasibility of this analysis, the strategy to determine the inverse of a singular matrix is thoroughly discussed, such that the general solutions can be smoothly applied to an isotropic tube problem. The results for an isotropic tube, which are reduced from the general forms, are compared with the well-established researches of related cases in the literature. The acceptable correspondences indicate the applicability of this study. An elastic problem of a cylindrically orthotropic tube containing a dislocation is also investigated as a demonstrating example. On this example, several particular phenomenons of stress distribution on the tube surface are presented in figures and discussed.
Behaviors of Flame and Flow of Swirling Wake During Fuel Jet Oscillation Due to Acoustic Excitations
Authors: Loretero M. E. , Huang R. F.
Published: May 2011

The flame and flow behaviors along with the fuel jet oscillations of non-premixed and axisymmetric swirling wake during acoustic excitations are studied experimentally. Visual observations on the reaction zones are carried out to identify the flame behaviors. Close-up images at the flame base as well as the whole flame images are captured and discussed. Traditional photography techniques are adopted to illustrate the dimensional characteristics of every flame mode. The central jet oscillations are diagnosed by a two component laser Doppler anemometer. Combined images of the flame and flow are gathered using the laser-light sheet assisted Mie scattering method. Results showed that the short and wide flame which was induced during acoustic forcing is principally because of the severe premixing at the tip of the burner tube. Wake recirculation bubble enhanced premixing at low swirl number while it damped the jet oscillation at higher swirl number. Mechanics of mixing at every flame mode during acoustic excitation are reported and discussed.
Variation of Ovalization for Sharp-Notched Circular Tubes Under Cyclic Bending
Authors: Lee K.-L. , Hung C.-Y. , Pan W.-F.
Published: May 2011

In this paper, an experimental investigation on the variation of ovalization for sharp-notched circular tubes subjected to cyclic bending is discussed. The tube bending machine and curvature-ovalization measurement apparatus were used to test the unnotched and sharp-notched 304 stainless steel tubes. For sharp-notched tubes, five different notch depths (0.2, 0.4, 0.6, 0.8 and 1.0mm) were considered in this study. It was found that the experimental curve of the ovalization and the number of cycles could be divided into three stages-an initial, secondary and tertiary stage. An empirical relationship was proposed for simulating the aforementioned curve for the initial and secondary stages in this study. It has been shown that the derived empirical relationship was in good agreement with the experimental data.
Radiological and Mathematical Studies Regarding the Effects of Spinal Fixation on Kinematics and Mechanics at the Parafixed Segments
Authors: Lin S.-C. , Tsai W.-C. , Wu S.-S. , Chen P.-Q.
Published: May 2011

Spinal fixation and fusion has been adopted as a common procedure in spinal surgery. However, the degeneration as a result of parafixation may produce clinically significant problems. Previous studies have already shown increased loads, mobility, and intradiscal pressure at the parafixed segments. These may hasten the degeneration and instability of the neighboring segments. However, controversy remains regarding the correlation between surgical fixation and degeneration owing to parafixation. This study tried to elucidate their relationship by analyzing the in vivo roentgenograms of the post-fusion lumbar spine to measure the motion distribution of the fixed and adjacent unfused spinal segments. In addition, a mathematical model was developed to investigate the effects of implant fixation on the kinematics and mechanics at the parafixation segments.

The current radiological studies demonstrated that spinal fixation resulted in the redistribution of intersegmental mobility. The loss of flexion mobility at the fixed segments was unequally compensated for by the increased mobility at all adjacent free segments. This mechanical model can predict the redistribution patterns of mobility and stress at the parafixation segments. This redistribution depends on the fixation levels, implant rigidity, and subject predisposition. Additionally, such compensation was more marked in the tri-segmental than in the two-segment fixation, especially among patients who underwent greater spinal load.

This study concluded that the increased flexural rigidity at the fixed segment leads to the compensated kinematic and mechanical demands upon the unfixed adjacent segments. Accordingly, the cumulative effects of such increased mobility and loadings on the adjacent segments could be logically postulated to be the principal causes of accelerated degeneration of the adjacent lumbar segments, both upper and lower portions, subsequent to fusion surgery.
All Speed and High-Resolution Scheme Applied to Three-Dimensional Multi-Block Complex Flowfield System
Authors: Hsu Uzu- Kuei , Tai Chang- Hsien , Tsai Chien- Hsiung
Published: May 2011

The improved numerical approach is implemented with preconditioned Navier-Stokes solver on arbitrary three-dimensional (3-D) structured multi-block complex flowfield. With the successful application of time-derivative preconditioning, present hybrid finite volume solver is performed to obtain the steady state solutions in compressible and incompressible flows. This solver which combined the adjective upwind splitting method (AUSM) family of low-diffusion flux-splitting scheme with an optimally smoothing multistage scheme and the time-derivative preconditioning is used to solve both the compressible and incompressible Euler and Navier-Stokes equations. In addition, a smoothing procedure is used to provide a mechanism for controlling the numerical implementation to avoid the instability at stagnation and sonic region. The effects of preconditioning on accuracy and convergence to the steady state of the numerical solutions are presented. There are two validation cases and three complex cases simulated as shown in this study. The numerical results obtained for inviscid and viscous two-dimensional flows over a NACA0012 airfoil at free stream Mach number ranging from 0.1 to 1.0E-7 indicates that efficient computations of flows with very low Mach numbers are now possible, without losing accuracy. And it is effectively to simulate 3-D complex flow phenomenon from compressible flow to incompressible by using the advanced numerical methods.
Gasdynamic-Like Equations for Oblique Shock Waves and Nozzle Flows in Soap Films
Authors: Wen C.-Y. , Lai J.-Y.
Published: May 2011

The governing equations for oblique shock waves and nozzle flows in soap films are formulated based on their very specific property equations. The θ-β-M relation for oblique shock waves and the width-velocity relation for quasi-one-dimensional nozzle flows are presented. The results are similar to those of compressible gases. On short time scales, the analogy of soap films to two-dimensional (2-D) compressible gases with a specific heat ratio of γ = 1.0 that is shown by Wen and Lai [1], Wen, et al. [2] and Chomaz [3] is again demonstrated. The present results supplement the theory of compressible flows in soap films.
Micro-System Displacement and Profile Measurement By an Integrated Photon Tunneling and Confocal Microscope
Authors: Chen Wen-Jong , Lee Chih-Kung , Lu Shui-Shong , Huang Long-Sun , Chu Ta-Shun , Cheng Ying-Chou , Yeh Wu-Fone
Published: May 2011

An integrated optical method for measuring deformation of micro-mechanical systems with better than sub-micron resolutions is detailed. Both a confocal laser scanning microscope and a photon tunneling microscope were integrated into a single microscopy system due to their complimentary capabilities for examining sub-micrometer deformations. A halogen lamp and laser were adopted as the two light sources for the measurements. Since topographic information of samples up to a 15μm by 15μm area can be measured, a three-dimensional displacement field of the sample was extracted by comparing topographies of the same specimen area before and after deformation. The bending and twisting deformation of a micro-mirror driven by the electrostatic force was measured to demonstrate the capability of this newly developed instrument. The experimental data obtained agrees reasonably well with the theoretical results calculated by adopting an analytical solution and a finite element method. The small discrepancy in the result can be traced to the surface roughness effect, which is often non-negligible in micro-systems.
The Stress-Strain Behavior of Densified Mix Design of Concrete
Authors: Chang Ping-Kun
Published: May 2011

This paper investigates the compressive strength and workability of High-Performance Concrete (HPC) which yields a slump at 250 ± 20mm and a slump flow at 650 ± 50mm. From the complete stress-strain curve, it shows the peak strain will be higher while the strength increases. Two kinds of the post failure models can be distinguished. The first type (Type I) is called strain softening and the second type (Type II) is called strain snapping back. Also, it is found that the modulus of elasticityEcdecreases as the volume of cementitious pasteVpincreases. On the other hand, Poisson's ratio ν increases asVpincreases.
Evaluation of Bridge Safety Based on Concrete Nondestructive Test
Authors: Liu Pei-Ling , Sun Pi-Fen
Published: May 2011

This paper develops a framework for the safety assessment of bridges based on the nondestructive test (NDT) results of concrete. The transient elastic wave test is performed to measure the P wave velocity of concrete. The Bayesian approach is adopted to construct the posterior distribution of concrete strength. Then, reliability analysis is carried out to evaluate the safety of the bridge using the modified distribution. The limit-state function is formulated according to the AASHTO specifications. Finally, the reliability index is compared to the target reliability to see if repair or reconstruction is required. A numerical example is presented to illustrate the safety assessment of a solid-slab bridge using the proposed method.
On Approximate Solutions for Two-Dimensional Thermoelastic Problems with a Nearly Circular Hole
Authors: Wang Chung-Hao , Chao Ching-Kong
Published: May 2011

The general approximate solutions for the two-dimensional thermoelastic problems with a nearly circular hole are provided in this study. Based on Stroh formalism and the method of conformal mapping, the boundary perturbation analysis is applied to solve the problems of a hole with arbitrary shape. The radius of the hole considered here is represented as a sum of a reference constant and a perturbation magnitude that is expanded into a Fourier series. In order to illustrate the applicability and efficiency of the present approach, special examples associated with polygonal hole problems are solved explicitly and discussed in detail. Since the general solutions have not been found in the literature, comparison is made with some special cases for which the analytical solutions exist, which shows that our proposed method is effective and general.
A Gurson Yield Function for Anisotropic Porous Sheet Metals and its Applications to Failure Prediction of Aluminum Sheets
Authors: Wang D.-A. , Chien W. Y. , Liao K. C. , Pan J. , Tang S. C.
Published: May 2011

An approximate anisotropic yield function is presented for anisotropic sheet metals containing spherical voids. Hill's quadratic anisotropic yield function is used to describe the anisotropy of the matrix. The proposed yield function is validated using a three-dimensional finite element analysis of a unit cell model under different straining paths. The results of the finite element computations are shown in good agreement with those based on the yield function with three fitting parameters. For demonstration of applicability, the anisotropic Gurson yield function is adopted in a combined necking and shear localization analysis to model the failure of AA6111 aluminum sheets under biaxial stretching conditions.
Stress Wave Propagation for Nonlinear Viscoelastic Polymeric Materials at High Strain Rates
Authors: Wang Li-Lih
Published: May 2011

Without knowing the dynamic constitutive relation of materials under high strain rates, no wave propagation can be correctly analyzed. A Series of experimental and theoretical investigation at high strain rates revealed that the nonlinear viscoelastic behavior of polymers and the related composites are well described by the Zhu-Wang-Tang (ZWT) nonlinear viscoelastic constitutive equation. The impulsive reponse of ZWT materials consists of a rate independent nonlinear elastic response and a high frequency linear viscoelastic response. The dispersion and attenuation of nonlinear viscoelastic waves mainly depend on the effective nonlinearity and the high frequency relaxation time θ2. An “effective influence distance” or “effective influence time” is defined to characterize the wave propagation range where θ2 dominates the impact relaxation process.
A Rigid Elliptic Inclusion in an Elastic Medium With a Slipping Interface
Authors: Wang Yung-Ming
Published: May 2011

When an elastic medium containing an elliptic inclusion with a sliding interface is subjected to a remote pure shear, it was found that the inclusion behaves like a cavity. Since a circle is a special case of an ellipse, the solution should be applicable to a circular inclusion as well. However, it breaks down when the ellipse degenerates into a circle. This implies that the solution is questionable. In this paper the problem is examined by considering a rigid elliptic inclusion in an elastic medium with sliding interface between them. By taking account of a large rotation of the inclusion instead of a small rotation, we obtain a uniformly valid solution applicable to a circular inclusion as well as to an elliptic inclusion. The solution reveals a remarkable snapping behavior of the inclusion under a critical load. A simple condition for its occurrence is derived.