bluuebunny/crossref_metadata_2025 huggingface dataset:
Optimization of Sandwich Monocoque Car Body with Equivalent Shell Element
Authors: Chang C.-K. , Cheng J.-H.
Published: May 2011

This research proposes a straightforward and efficient method to optimize a sandwich monocoque car body with the developed equivalent shell element based on stiffness equivalence. The fact that stiffness rather than strength is dominant constraint for ordinary car body optimization is demonstrated. A simple but heavy flat chassis plate is utilized as upper bound, while an ideal monocoque is used as lower bound for an actual car body optimization. Convergence hours can be significantly reduced with the equivalent element and the initial-bounded method. A novel electric car body optimization is presented, fulfilling UltraLight Steel Auto Body (ULSAB) stiffness requirements and showing similar optimal weight results as a conventional approach with a much lower analysis time cost.
Interaction of Oscillatory Flows with a Square Cylinder
Authors: Chern M.-J. , Lu Y.-J. , Chang S.-C. , Cheng I.-C.
Published: May 2011

The behaviour of vortices induced by a single square cylinder in an oscillating flow was investigated. The flow patterns in the vicinity of square cylinders were visualized using an in-house numerical model. Meanwhile, force coefficients exerted on the square cylinder were determined numerically. In terms of various Keulegan-Carpenter (KC) numbers, it turns out that the flow patterns for an oscillating flow past a single cylinder can be divided into three modes: (i) no vortex, (ii) pairs of symmetric vortices, and (iii) asymmetric vortex shedding. Reynolds (Re) number did not affect the flow field apparently in this study. In addition, the in-line force coefficient decreases exponentially as KC increases. Spectrum analysis of in-line force coefficients for various KCs was provided. It can be found that the flow system was at a periodic state at small KC for the first two modes. Variations of the flow system from a periodic state to a highly nonlinear state in which asymmetric vortex shedding appeared were demonstrated for increasing KC. The relationship between the in-line force and KC was provided for future applications.
Investigation of Tunnel Stress Path During Face Advancement
Authors: Chen C.-N. , Huang W.-Y.
Published: May 2011

Tunnel stress path during excavation was investigated in the study scope. The triple-center section is commonly designated for highway tunnels, but the analytical solution of the stress state for a non-circular tunnel section with multiple bench excavations is difficult to obtain. Our investigation provides an algorithmic procedure which reliably evaluates stress adjustment of a bench excavation with respect to the three-dimensional state of stress. Evaluation of a safety factor at the tunnel face during advancement is performed following the stress path and principal stress space.
Shape Optimization of Double-Chamber Side Mufflers with Extended Tube by Using Four-Pole Matrix and Simulated Annealing Method
Authors: Chiu M.-C.
Published: May 2011

As an excellent ability in eliminating venting noise in lower frequencies, the reactiv silencer has prevailed and is widely discussed. Most researchers have explored noise reduction effects due to the flowing rate and temperature gradient based on a pure plane wave theory; however, the maximum noise reduction of a silencer under a space constraint, which frequently occurs in engineering problems, is rarely addressed. Because most of the optimal assessments were oriented with a slower optimizer, the issue of using a novel optimizer to speed up the optimization of a complicated silencer has arisen. In this paper, the optimal design of a double-chamber side muffler connected with an internal extended tube under a limited space is presented; in addition, simulated annealing (SA) is selected as the optimizer. Based on a plane wave theory, the systems' matrices under a flowing effect have been established. To verify the accuracy of the mathematical model, one set of silencers has been constructed and acoustically tested in the laboratory. The results reveal that they are in agreement; thereafter, two numerical cases of optimal noise reduction to pure tone and octave band noise sources are exemplified. Consequently, the SA method can definitely provide a quick and efficient way in optimal muffler design work.
Analysis of Cohesive Crack Growth by the Element-Free Galerkin Method
Authors: Soparat P. , Nanakorn P.
Published: May 2011

In this study, the element-free Galerkin (EFG) method is extended to include nonlinear behavior of cohesive cracks in 2D domains. A cohesive curved crack is modeled by using several straight-line interface elements connected to form the crack. The constitutive law of cohesive cracks is considered through the use of these interface elements. The stiffness equation of the domain is constructed by directly including, in the weak form of the global system equation, a term related to the energy dissipation along the interface elements. The constitutive law of cohesive cracks can then be considered directly and efficiently by using this energy term. The validity and efficiency of the proposed method are discussed by using problems found in the literature. The proposed method is found to be an efficient method for simulating propagation of cohesive cracks.
Interactions Inside a Coupled Oscillation System of Bubble-Viscous Liquid-Vessel and the Induced Stresses and Strains Within the Vessel Wall
Authors: Hu Yuantai , Gao Farong , Hu Hongping , Chen Chuanyao
Published: May 2011

The evolution of a bubble confined inside a nonlinear micro vessel fully filled with a viscous liquid, subjected to a shock lithotripsy wave (SWL), is analyzed with a previously established asymmetrical model on bubble oscillation. Both the normal and shear stress components within the vessel wall are calculated. It is observed that although the shear stress induced by viscosity is far less than the normal stresses, hypertension patients are still at more risk than normal people in SWL because of the high blood pre-pressure and stiff vessel wall accompanying their high blood viscosity. Hence, safety of hypertensive patients with high blood viscosity must be taken into careful consideration in SWL. More detailed numerical results show that the increase of circumferential normal stress and strain in SWL is significantly larger than that of other stresses and strains. Large circumferential normal stress and strain are responsible for excessive dilation of vessel wall during asymmetrical oscillation of constrained bubbles, which implies that the vessel wall will rupture mainly in the form of a cleft along the vessel axial direction.
Limitations on the Use of Effective Properties for Multicomponent Materials
Authors: Han R. , Ingber M. S. , Hsiao S. C.
Published: May 2011

Multicomponent composite materials comprised of a dispersed phase suspended in a matrix material are important in a wide variety of scientific and engineering applications including electronic encapsulation, functionally graded materials, and fiber-reinforced structural components among others. Modelling of this class of composites is typically performed using an effective property approach. This approach presumes that the characteristic dimension of the dispersed phase elements is small in comparison to the characteristic length scale of the physical problem under consideration. However, it is not possible to predict a third effective elastic property based on two independent effective elastic properties as it is for homogeneous elastic isotropic materials. Therefore, a macroscale simulation based on an effective Young's modulus and Poisson ratio may yield poor results for a material subjected to shear loading since there is a potentially incorrect presumed effective shear modulus for the simulation. In the current research, boundary element simulations are performed for mesoscopic samples of composite materials to determine effective bulk moduli, shear moduli, Young's moduli, and Poisson ratios. From these analyses, limitations in the effective property approach can be examined.
Biomechanical Analysis of Nonconstrained and Semiconstrained Total Elbow Replacements: A Preliminary Report
Authors: Shih K.-S. , Lu T.-W. , Fu Y.-C. , Hou S.-M. , Sun J.-S. , Cheng C.-Y.
Published: May 2011

The development of elbow arthroplasties has significantly improved the quality of life for many patients suffering from disabling elbow disorders. However, the high complication rate such as loosening and instability limits the long term use of total elbow replacement (TER). In the present study, biomechanical analyses on patients with unilateral nonconstrained (Souter-Strathclyde) and semiconstrained (Coonard-Morrey) TER subjects were performed to investigate differences of their motion patterns under unloaded and loaded conditions. In a biomechanical laboratory, each subject performed vertical and horizontal elbow flexion/extension first without and then with external loading (5 lb). The kinematic data were measured using 3D motion analysis system and the motion axis of the elbow was calculated by a well-defined mathematic model. During these tests, the upperarm was fixed with a special fixation device and their forearms fully supinated. The elbow motion patterns of the affected sides were compared with those of the normal sides and between different conditions. The results revealed that the elbows moved about a relatively fixed axis both in the semiconstrained and nonconstrained groups in the vertical flexion/extension with or without external loading, compatible with the normal elbows. However, the nonconstrained elbows were less stable during horizontal flexion/externsion motion with or without external loading and the elbow axis moved significantly, indicating of less stability. We conclude that this methodology of elbow motion analysis is acceptable and can be widely recommended for total elbow study. Moreover, the nonconstrained TER is less stable than the semiconstrained TER during the horizontal movement, which was compatible with previous clinical results. The patients with nonconstrained TER are suggested to avoid using their elbows in horizontal motion, especially in loaded conditions.
Applied Mechanics in Science and Engineering
Authors: Pao Yih-Hsing
Published: May 2011

This article traces the development of applied mechanics and its relation to science and engineering by reviewing first the history of mechanics from 1600 to 1900, the physics of the 19th century, and the engineering education in the same period. The review is followed by a discussion on modern physics and modern engineering, and the formation of applied mechanics as a discipline in science and one in engineering, which is classified into 94 subjects in 10 categories by Applied Mechanics Reviews. The article concludes with a chart to summarize the relation between science and engineering, and the interactions of applied mechanics with other disciplines. There are 15 references included in this article.

Originally published in Applied Mechanics Reviews, Vol. 51, No. 2, February 1998
An Application of Elastodynamic Reciprocity to Reflection by an Obstacle in a Waveguide
Authors: Achenbach J.D.
Published: May 2011

The reciprocal identity which connects two elastodynamic states, denoted by A and B, is used in this paper to obtain two results for an elastic layer. The first is an orthogonality condition for wave modes. For that case the states A and B are wave modes propagating in the same direction. The second result concerns reflection and transmission of wave motion by an obstacle in the layer. Now state A is defined by a superposition of incident wave modes and its reflection and transmission by the obstacle. Expressions for the reflection and transmission coefficients are obtained by selecting counter propagating wave modes for state B. It is also shown that the reflection by an obstacle in a layer can be extended to obtain the reflection and transmission coefficients for a planar array of obstacles in an unbounded elastic solid. For clarity all results are presented for horizontally polarized transverse wave motion.
Efficacy of Drilling Degrees of Freedom in the Finite Element Modeling of P-and SV-Wave Scattering Problems
Authors: Kim Jaehwan , Varadan Vasundara V. , Varadan Vijay K.
Published: May 2011

This paper deals with a hybrid finite element method for wave scattering problems in infinite domains. Scattering of waves involving complex geometries, in conjunction with infinite domains is modeled by introducing a mathematical boundary within which a finite element representation is employed. On the mathematical boundary, the finite element representation is matched with a known analytical solution in the infinite domain in terms of fields and their derivatives. The derivative continuity is implemented by using a slope constraint. Drilling degrees of freedom at each node of the finite element model are introduced to make the numerical model more sensitive to the transverse component of the elastodynamic field. To verify the effects of drilling degrees freedom and slope constraints individually, reflection of normally incident P and SV waves on a traction free half space is considered. For P-wave incidence, the results indicate that the use of a slope constraint is more effective because it suppresses artificial reflection at the mathematical boundary. For the SV-wave case, the use of drilling degrees of freedom is effective in reducing numerical error at the irregular frequencies.
Multi-Pole Representation of Small Acoustic Sources
Authors: Santosa Fadil , Symes William W.
Published: May 2011

Band-limited acoustic sources of small spatial extent produce radiation patterns well approximated by those of multi-poles. Assumed limits on dimensionless size Ka and source efficiency lead to explicit rules for the necessary length of the multi-pole series.
Wave Equations of Elastic Type-II Superconductors
Authors: Chen K. C. , Yeh C.S.
Published: May 2011

It is shown that when the thermodynamic fluxes are included as independent thermodynamic state variables of the generalized entropy density, the constitutive equations for the conserved state variables and the evolution equations for the nonconserved state variables of elastic type-II superconductors can be derived systematically. In particular, the transport equations generalizing the Fourier law for heat transport and the time-dependent Ginzburg-Landau equation for the relaxation of superelectron are proposed in this paper.
Sensing and Control of Aerodynamic Separation by MEMS
Authors: Lee Gwo-Bin , Huang Adam , Ho Chih-Ming , Jiang Fukang , Grosjean Charles , Tai Yu-Chong
Published: May 2011

During the last decade, we have applied MEMS-based transducers to develop a technology for maneuvering aircraft by sensing and controlling the separation around the leading edge of a delta wing. In this paper, we will summarize our experience of this endeavor.
Ultimate Moment Capacities of Round Prestressed Concrete Poles
Authors: Liu Ine-Wei , Lu Jun-Kai
Published: May 2011

An alternative technique for the determination of ultimate moment capacities of round prestressed concrete poles is presented in this paper. The traditional concrete compression area of poles is determined using the conventional iterative design process, the compatibility and equilibrium approach. Moreover, the area of annulus defined by the neutral axis is multiplied by an area reduction factor. It is possible to use numerical methods to calculate the centroid of the reduced annulus. However, the concrete compression zone and strain variation in the longitudinal reinforcement makes the calculation awkward. This paper addresses the problem from a different perspective. No reference to area reduction factor is required in the course of locating the neutral axis. The results are compared in a very satisfactory manner with that obtained using PCI approach. The purpose is to provide formulations that can be easily computerized and implemented on relevant software for the design of round prestressed concrete poles.
Robust Kalman-Filter-Based Frequency-Shaping Optimal Active Vibration Control of Uncertain Flexible Mechanical Systems
Authors: Chen Shinn-Horng , Chou Jyh-Horng , Zheng Liang-An
Published: May 2011

This paper presents a time-domain control methodology, which is named as the robust Kalman-filter-based frequency-shaping optimal feedback (KFBFSOF) control method, to treat the active vibration control (or active vibration suppression) problem of flexible mechanical systems under simultaneously high frequencies unmodelled dynamics, residual modes, linear time-varying parameter perturbations in both the controlled and residual parts, noises (input noise and measurement noise),and noise uncertainties. Two robust stability conditions are proposed for the flexible mechanical system, which is controlled by a KFBFSOF controller and subject to mode truncation, noise uncertainties, and linear structured time-varying parameter perturbations simultaneously. The advantage of the presented KFBFSOF control methodology is that it can make the controlled closed-loop system to obtain both good robustness at high frequencies and good performance at low frequencies. Besides, the proposed robust stability criteria guarantee that the designed KFBFSOF controller can make the controlled flexible mechanical system to avoid the possibilities of both spillover-induced instability and time-varying-parameter-perturbation-induced instability. Two examples are given to illustrate the application of the presented control methodology to the active vibration control problems of a simply supported flexible beam and of a flexible rotor system.
On Evaluation of Lamb's Integrals for Waves in a Two-Dimension Elastic Half-Space
Authors: Yeh Chau-Shioung , Teng Tsung-Jen , Liao Wen-I
Published: May 2011

1. Figures 13 to 18 should be deleted from the paper.

2. The first sentence on page 118, “The corresponding and traction field at r = 1, 10 and 20 for the case of m = 0 are depicted in Figs. 12(a), (b) and (c),” should be modified as: “The corresponding radiation patterns of displacement and traction field at ksr = 1, 10 and 20 for the case of m = 0 are depicted in Figs. 12(a), (b) and (c), respectively.”
EndoFEM Crack Closure Analysis of AL2024-T3 CCT Specimen Under All Tension Fatigue Loading
Authors: Lee C. F. , Hsiao L. T.
Published: May 2011

The endochronic cyclic plasticity with finite element analysis (EndoFEM) is employed to simulate plasticity-induced crack closure phenomenon of Al 2024-T3 CCT specimens under maximum cyclic stress of 80MPa and 0.1 stress ratio (R). Various fatigue crack lengths are generated by a rc dominated-node-released strategy. The suitability of element-mesh planning around crack tip is supported by the real simulations in the decreasing tendencies of crack opening load (Pop) with increased distance behind the crack tip, and the enough elements to reflect the reversed plastic responses at minimum load.

EndoFEM results of vertical stress ahead of the crack tip show a typical distribution of small scale yield (SSY) in the realm of fracture mechanics; and Pop/Pmax ratio determined at 1mm behind crack tip is kept constant i.e. Kmax-independent. In these cases, fatigue parameters based on either the far field loading parameter ΔK, the effective ΔK (ΔKeff) with crack closure effect, or the mechanical responses ahead of crack tip (e.g. stress parameter, reversed (plastic) strain at 1mm) are all equivalent and are linearly correlated with the stage II fatigue crack growth (FCP) rate. However, for longer crack length with the ligament bending effect or shorter crack length with the starter notch effect, the Pop/Pmax ratio decreases and changes the SSY stress distribution. This result reduces the usefulness of the above fatigue parameters. As a consequence, a nonlinear correlation of FCP rates with ΔK or ΔKeff are purely empirical. The Kmax-dependent ΔKeff must be considered in the correlation as suggested by the present study of EndoFEM.
Effect of Lubrication on the Performance and Dynamic Loads of Scroll Compressors
Authors: Hsieh Jen-Jie , Lee Wen-Shing , Wu Wen-Fang , Chen Sih-Li
Published: May 2011

To study the effect of lubrication on the performance and dynamic loads of scroll compressors, a theoretical model is proposed in this paper. The model includes both thermal and dynamic analyses in which the lubrication theory is emphasized in particular. A computer simulation program is written accordingly, and the effects of different design parameters including oil flow rate, injection position, injection temperature and rotating speed are investigated. The output variables such as gas force, contact force, contact moment and thermal performance of the compressor are obtained. Some of the results are compared with experimentally measured data, and good agreements are found between the simulation results and the measured data. The applicability of the simulation program is thus verified.Analytical results from running this program can provide us valuable information on the design improvement of a scroll compressor.
Numerical Studies of the Passage Flowfield in a 3-D Transonic Turbine Blade Cascade
Authors: Tai Chang-Hsien , Wang Ding-San , Chen Ping-Hei , Hsu Uzu-Kuei , Miao Jr-Ming
Published: May 2011

A three-dimensional Navior-Stokes analyzer based on control volume method is developed to simulate the complex flow field within a turbomachinery. With VKI-CT2 turbine blade as the test model, numerical results are compared with experimented data and shows the existence of separation-transition bubble and the interaction of shock with turbulent boundary layer flow. The governing Navier-Stokes equations are solved by an improved numerical method that uses an upwind flux-difference split scheme for spatial descretization and an explicit optimally smoothing multi-stage scheme for time integration. Turbulent stresses are approximated by modifying Baldwin-Lomax algebraic, k-ε, R-k-ε and RNG k-ε turbulence models. According to the results of this research, this analyzer can indeed effectively modulate and simulate the aerodynamic characteristic of the transonic turbine rotor near the endwall.
A Point-Focus PVDF Transducer for Lamb Wave Measurements
Authors: Lee Yung-Chun , Tein Yi Fan , Chao Yu Yi
Published: May 2011

This paper reports the development of a point-focused PVDF transducer with a large aperture surface and its application on measuring Lamb wave dispersion curves. The point-focused transducer is constructed by forcing a piezoelectric PVDF film into a concave spherical shape. The acoustic waves radiated from the PVDF film are then focused into a point without using any acoustic lens. Similar to its line-focused counterpart, the point-focused transducer is capable of measuring dispersion curves of lamb waves provided its aperture angle is large enough. To verify this, experimental testing is carried out on several thin metal plates and good measurement results are observed. Future improvements and applications on the transducer will be addressed.
Numerical and Experimental Investigations of Wave Field Around a Circular Island with the Presence of Weak Currents
Authors: Lin Ming-Chung , Hsu Chao-Min , Wang Shou-Cheng , Ting Chao-Lung
Published: May 2011

This study elucidated the complicated phenomena of wave refraction and diffraction around a circular island due to random incident waves traveling with a current. Various combinations of random incident wave and current conditions were used to investigate the wave height distributions around a circular island numerically and experimentally. Numerical calculations were carried out based on the theory derived by Lin & Hsu [1]. According to the results, it shows that numerical calculations can predict experimental data quantitatively well.
Flame Stability Analysis of Turbulent Non-Premixed Reacting Flow in a Simulated Solid-Fuel Ramjet Combustor
Authors: Liou Tong-Miin , Hwang Po-Wen , Li Yi-Chen , Chan Chia-Yen
Published: May 2011

To investigate the flame stability in a solid-fuel ramjet combustor, time-accurate calculations using a compressible flow solver with a modified Godunov flux-splitting scheme have been performed on high Reynolds number turbulent non-premixed reacting flows over a backward-facing step with mass bleed on one wall. The combustion process considered was a one-step, irreversible, and finite rate chemical reaction. The numerical results for reacting flows show that the two-dimensional (2-D) simulations can provide reasonable predictions on the dimensionless particle number decay rate and residence time in the flame holding recirculation zone, evolutions of both axial and transverse mean velocity profiles, and critical characteristic exhaust velocity separating the sustained combustion from the non-sustained combustion. In addition to the validation of 2-D reacting flow calculations, two- and three-dimensionally computed mean-velocity profiles are compared with existing experimental data for isothermal flows to check the suitability of 2-D simulations on capturing the large-scale mean flows.
Endofem Integrated Methodology for Fatigue Crack Growth
Authors: Lee C. F. , Hsiao L. T.
Published: May 2011

In this paper, the FEM with the incremental endochronic cyclic plasticity (EndoFEM) and the rccontrolled node-released strategy are employed to study the fatigue crack opened/closed load (Pop) of Al 2024-T3 CCT specimens provided by Mageed and Pandey under several crack lengths and the constant amplitude with various load ratio (R). After statisfactory results are achieved by comparisons of computed Popvalues and cited experimental data, the simulations will be extended to the crack lengths with significant bending effect due to short ligaments or high peak (Pmax) or high positive or very low negative R cyclic loads. Through these simulations, the complete map of Pop/Pmaxvs. Kmaxand R can be constructed and thereafter its correspondant empirical formulae can be proposed. Using these formulae and selecting the traditional fatigue crack growth parameter ΔKeff, the Al 2024-T3 fatigue crack growth rate da/dN vs. ΔK and R data, provided by Hiroshi and Schijve, can be employed to proposed empirical formulae of da/dN vs. ΔKeffand R. After integration, fatigue-crack-growth length a vs. N curves computed by EndoFEM can be obtained. The results are agreed very well with the existing experimental curves.

According to the above procedures of simulation and steps of comparions with experiment, this paper may provides an integrate methodology of numerical simulation in the studies of fatigue crack growth for academic and industrial researches and design analysis.
Explicit Expressions of the Fundamental Elasticity Matrices of Stroh-Like Formalism for Symmetric/Unsymmetric Laminates
Authors: Hsieh M.C. , Hwu Chyanbin
Published: May 2011

Based upon our recent development of Stroh-like forma lism for symmetric/unsymmetric laminates, most of the relations for bending problems can be organized into the forms of Stroh formalism for two-dimensional problems. Through the use of Stroh-like formalism, the fundamental elasticity matrices Ni, S, H and L appear frequently in the real form solutions of plate bending problems. Therefore, the determination of these matrices becomes important in the analysis of plate bending problems. In this paper, by following the approach for two-dimensional problems, we obtain the explicit expressions of the fundamental elasticity matrices for symmetric and unsymmetric laminates, which are all expressed in terms of the extensional, bending and coupling stiffnesses of the composite laminates.
Crack Propagation Analysis of Statically Indeterminate Beam by Elastic-Plastic Fracture Mechanics
Authors: Liu Sung-Po , Shih C. J. , Kuo Liang-Yu
Published: May 2011

This paper develops an analytical model for the plastic collapse of a statically indeterminate rectangular beam containing a crack. Limit analysis, elastic-plastic fracture mechanics, compliance and J-integral concepts are used to study JIC and dJ/da that influence the crack propagation. The relations among the plastic hinge, applied load, linear displacement, rotational angle and crack growth leads to a better understanding of the problem as a consequence of this study. The conclusions are: (1) Unstable ductile fracture occurs at the crack propagates before plastic collapse or at dJ/da is smaller than the minimum critical value. (2) LBB (leak-before-break) characteristic of the statically indeterminate rectangular beam is valid if the crack propagates before plastic collapse.
Remeshing Strategy of the Supersonic Flow Over a Backward-Facing Step
Authors: Yang Shih-Ying
Published: May 2011

A modified error indicator and an extended locally implicit scheme with anisotropic dissipation model on quadrilateral-triangular mesh are developed to study the supersonic flow over a backward-facing step. In the Cartesian coordinate system, the unsteady Euler equations are solved. The modified error indicator, in which the unified magnitude of density gradient and unified magnitude of gradient of vorticity magnitude are incorporated, is utilized to treat the new node spacing of mesh remeshing. To assess the accuracy of the extended locally implicit scheme with anisotropic dissipation model on quadrilateral-triangular mesh, two flow calculations which include the oblique-shock reflection at a wall and transonic flow around an NACA 0012 airfoil are performed. Based on the comparison with the related numerical and experimental data, the accuracy of the present approach is confirmed. According to the high-resolutional result on the adaptive mesh, the structure of backstep corner vortex, expansion wave and oblique shock wave is distinctly captured.
Method of Fundamental Solutions for Stokes Problems by the Pressure-Stream Function Formulation
Authors: Young D. L. , Wu J. T. , Chiu C. L.
Published: May 2011

The main purpose of this paper is to investigate the pressure-stream function formulation to solve 2D and 3D Stokes flows by the meshless numerical scheme of the method of fundamental solutions (MFS). The MFS can be regarded as a truly scattered, grid-free (or meshless) and non-singular numerical scheme. By the proposed algorithm, the stream function is governed by the bi-harmonic equation while the pressure is governed by the Laplace equation. The velocity field is then obtained by the curl of the stream function for 2D flows and curl of the vector stream function for 3D flows. We can simultaneously solve the pressure, velocity, vorticity, stream function and traction forces fields. Furthermore during the present numerical procedure no pressure boundary condition is needed which is a tedious and forbidden task. The developed algorithm is used to test several numerical experiments for the benchmark examples, including (1) the driven circular cavity, (2) the circular cavity with eccentric rotating cylinder, (3) the square cavity with traction boundary conditions and (4) the uniform flow past a sphere. The results compare very well with the solutions obtained by analytical or other numerical methods such as finite element method (FEM). It is found that the meshless MFS will give a simpler and more efficient and accurate solutions to the Stokes flows investigated in this study.
The Method of Fundamental Solutions with Dual Reciprocity for thin Plates on Winkler Foundations with Arbitrary Loadings
Authors: Tsai C. C.
Published: May 2011

This paper describes the combination of the method of fundamental solutions (MFS) and the dual reciprocity method (DRM) as a meshless numerical method to solve problems of thin plates resting on Winkler foundations under arbitrary loadings, where the DRM is based on the augmented polyharmonic splines constructed by splines and monomials. In the solution procedure, the arbitrary distributed loading is first approximated by the augmented polyharmonic splines (APS) and thus the desired particular solution can be represented by the corresponding analytical particular solutions of the APS. Thereafter, the complementary solution is solved formally by the MFS. In the mathematical derivations, the real coefficient operator in the governing equation is decomposed into two complex coefficient operators. In other words, the solutions obtained by the MFS-DRM are first treated in terms of these complex coefficient operators and then converted to real numbers in suitable ways. Furthermore, the boundary conditions of lateral displacement, slope, normal moment, and effective shear force are all given explicitly for the particular solutions of APS as well as the kernels of MFS. Finally, numerical experiments are carried out to validate these analytical formulas.
Dynamic Responses of Beams with a Flexible Support Under a Constant Speed Moving Load
Authors: Lin H.-P.
Published: May 2011

This paper deals with the linear dynamic responses of beams with a flexible support under a moving load with a constant speed. The entire system is modeled as a two-span beam and each span of the continuous beams is assumed to obey the Euler-Bernoulli beam theory. Considering the compatibility requirements on the flexible constraint, the relationships between two segments can be obtained. By using a transfer matrix method, the characteristic equation of the entire system can then be determined. The forced responses of the system under a moving load can then be obtained through modal expansion theory. Some numerical results are presented to the effects of support stiffness and the different speeds of the moving load.
C1 in Displacement Coefficient Method for Taiwan to Estimate Maximum Inelastic Displacement Demands of Existing Structures
Authors: Lin Y.-Y.
Published: May 2011

The coefficient C1 in the displacement coefficient method of FEMA-273/356 is the modification factor to relate the expected maximum displacements of elasto-plastic inelastic SDOF systems to displacements calculated for linear response. It permits the estimation of maximum inelastic displacements from maximum elastic displacements for structures with known lateral strength (usually, the existing structures). Recently, an improved C1 has been presented in FEMA-440 because it was shown that the C1 in FEMA-273/356 underestimates the maximum inelastic displacement demands of structures significantly. However, the improved C1 in FEMA-440 was derived from the earthquake ground motions recorded in California. In addition, it was mentioned in FEMA-440 that “caution should be used when extrapolating the results presented in the report for ground motions and site conditions that differ”. Because the characteristics of earthquakes occurred in Taiwan are different from those occurred in California, the coefficient for used in Taiwan needs to be modified. The objective of this paper is to propose appropriate C1 for use in Taiwan.
Thickness Effect on Low-Aspect-Ratio Wing Aerodynamic Characteristics at a Low Reynolds Number
Authors: Hsiao F. B. , Lin C. Y. , Liu Y. C. , Wang D. B. , Hsu C. C. , Chiang C. H.
Published: May 2011

This paper presents the study of aerodynamic performance about low-aspect-ratio wings at a low Reynolds number in wind tunnel testing. The aerodynamic properties, including lift, total drag, lift-to-drag ratio and induced drag were measured and analyzed for detailed investigations. Two forms of nonlinear equations of lift curves were reported for comparison. The effect of airfoil thickness was found to be significant on aerodynamic characteristics for all wings tested. The lift due to tip vortices was prominent for wings of AR =1.0 and their stall angles were all larger than 20°, which was mainly augmented by tip vortices shed from the wing tips.
Long-Wave Perturbation Method to Investigate Nonlinear Stability of the Thin Power Law Liquid Film Flowing Down on a Vertical Cylinder
Authors: Cheng P. -J. , Liu K. -C.
Published: May 2011

The influence of both the flow index and the cylinder size on the nonlinear hydrodynamic stability of a thin power law liquid film flowing down along the surface of a vertical cylinder is investigated. The long-wave perturbation method is employed to solve for generalized nonlinear kinematic equations with a free film interface. The normal mode approach is first used to compute the linear stability solution for the film flow. The method of multiple scales is then used to obtain the weakly nonlinear dynamics of the film flow for stability analysis. The stability criteria are discussed theoretically and numerically and stability diagrams are obtained. The modeling results indicate that by increasing the flow index and increasing the radius of the cylinder the film flow can become relatively more stable as traveling down along the vertical cylinder.
MHD Mixed Convection of Viscoelastic Fluid Over a Stretching Sheet with Ohmic Dissipation
Authors: Hsiao K.-L.
Published: May 2011

A magnetic hydrodynamic (MHD) mixed convection of an incompressible viscoelastic fluid over a stretching sheet with ohmic dissipation is studied. The buoyant effect and the electric number E1 couple with magnetic parameter M to represent the dominance of the ohmic effect are presented in governing equations which is the main contribution by this study. The similarity transformation, the finitedifference method have been used to analyze the present problem. The numerical solutions of the flow velocity distributions, temperature profiles and the important wall unknown values of f″(0) and θ′(0) are carried out.
Analytical Predictions of Strong Pseudo-Steady Mach Reflections for the Polyatomic Gas: SF6
Authors: Liu J. J.
Published: May 2011

Strong pseudo-steady Mach reflections in sulfur hexafluoride (SF6) are analyzed using the three-shock and local three-shock theories, where both the vibrationally-frozen (γ = 1.333) and -equilibrated (γ = 1.093) perfect-gas models are used to compare with existing experiments. The ranges of the incident shock Mach number and reflecting wedge angle studied are 1.49 ≤ Ms ≤ 5.95 and 10° ≤ θω ≤ 42°, respectively. It is found that predicted angles between the incident and reflected shocks from the local three-shock theory using the vibrationally-equilibrated fictitious perfect-gas model (i.e., γ = 1.093) agree closely with those, currently available in literature, measured experimentally; while these predicted angles obtained using the vibrationally-frozen perfect-gas model (i.e., γ = 1.333) differ significantly from the existing experiments. Taking the convex Mach stem curvature at the triple point into consideration, it is shown that both the triple point trajectory angle and the angle between the incident and reflected shocks of strong pseudo-steady Mach reflections in SF6 can be more accurately determined for wide ranges of Ms and θω from the three-shock theory using the vibrationally-equilibrated fictitious perfect-gas model than those without considering this effect.
Motion of Miscible Magnetic Fluids in a Vertical Capillary Tube
Authors: Chen C.-Y. , Lin H.-C. , Tsai W.-K. , Lin C.-H.
Published: May 2011

An experimental study of miscible magnetic fluid motion in a vertical capillary tube is presented. Transporting ferrofluids is dominated by a dimensionless magnetic number Ma, which characterizes the ratio of upward magnetic force to the downward gravity. Two distinct stages of motion, referred to as the sub-critical mode of finite lift and the effective transportation, are identified. These two modes are determined by the values of the sub-critical magnetic number Masub and critical magnetic number Macr respectively. For the cases of sub-critical mode (Masub < Ma < Macr), the ferrofluids are lifted to quasiequilibrium heights, which are nearly proportional to the magnetic number Ma. As for the situations of effective transportation (Ma > Macr), a penetrating finger of ferrofluids is formed similar to the conventional miscible displacements. A dimensionless proportionality of fingertip velocity ν, magnetic number Ma and field distribution profile fz is obtained as ν ∼ Ma1/2fz by scaling arguments. This proportional correlation shows a good agreement with the experiments.
Nondestructive Damage Detection of Two Dimensional Plate Structures Using Modal Strain Energy Method
Authors: Hu H.-W. , Wu C.-B.
Published: May 2011

A nondestructive detection method of surface cracks in two dimensional plate structures using modal strain energy method is investigated in this paper. Experimental modal analysis (EMA) is conducted on an aluminum alloy 6061 thin plate to obtain the mode shapes before and after damage under a completely free boundary condition. The measured mode shapes are used to compute the strain energy of the plate. Limited by the measured points, a differential quadrature method is employed to compute the partial differential terms in strain energy formula. A damage index is then defined based on strain energy ratio of the plate before and after damage. This damage index is employed to identify the location of surface crack in plate structure. A finite element analysis (FEA) is also performed to access this approach and demonstrate a feasible process for the experimental work. Good correlation between FEA and EMA results is obtained. The damage index obtained from both FEA and EMA successfully identify the location of surface crack in the aluminum plate. Only few measured mode shapes of the plate are required in this method, which provides a quick, flexible, inexpensive and nondestructive technique to identify the damagein local and global 2D plate structures.
Buckling and Postbuckling Analyses of a Skew Plate
Authors: Liao H. W. , Huang H. Y.
Published: May 2011

The applications of skew plates in the construction of aerospace structures are well known. The critical buckling load and post-buckling strength are two important design parameters of skew composite laminates. In this study, the refined buckling and nonlinear postbuckling solutions of a homogenous isotropic skew plate based on polynomial expansions of various degrees have been examined. Numerical results based on high-order Rayleigh-Ritz solutions are presented for certain type of oblique plates.
Predicting Fatigue Initiation Life of Sn/3.8Ag/0.7Cu Solder using Endochronic Cyclic Damage-Coupled Viscoplastic Theory
Authors: Lee C. F. , Lee Z. H.
Published: May 2011

This paper studied cyclic behavior Sn/3.8Ag/0.7Cu solder with dendritic microstructure. A cyclic damage factor D under constant strain amplitude fatigue tests, was defined by using the reducing rate of maximum cyclic tensile stress σa. The critical cyclic damage DC and it's fatigue initiation life NI were determined very consistently by using separately the experimental σavs. N curves and the percolation theory. The endochronic cyclic damage-coupled viscoplastic theory proposed by the 1st author was used to simulate cyclic stress-strain hysteresis loops with damage under strain amplitude (εa) 0.8% at 298K. The results were in very good agreement with data. Combining the evolution equation of intrinsic damage and the computed cyclic stress-inelastic strain relation, a modified Coffin-Manson relationship was derived. By setting DC = 0.3, it predicted very effectively the NI data under σa from 0.2% to 1.0%.
A Study of Parallel Efficiency of Modified Direct Algorithm Applied to Thermohydrodynamic Lubrication
Authors: Wang N. , Tsai C.-M. , Cha K.-C.
Published: May 2011

This study examines the parallel computing as a means to minimize the execution time in the optimization applied to thermohydrodynamic (THD) lubrication. The objective of the optimization is to maximize the load capacity of a slider bearing with two design variables. A global optimization method, DIviding RECTangle (DIRECT) algorithm, is used. The first approach was to apply the parallel computing within the THD model in a shared-memory processing (SMP) environment to examine the parallel efficiency of fine-grain computation. Next, a distributed parallel computing in the search level was conducted by use of the standard DIRECT algorithm. Then, the algorithm is modified to provide a version suitable for effective parallel computing. In the latter coarse-grain computation the speedups obtained by the DIRECT algorithms are compared with some previous studies using other parallel optimization methods. In the fine-grain computation of the SMP machine, the communication and overhead time costs prohibit high speedup in the cases of four or more simultaneous threads. It is found that the standard DIRECT algorithm is an efficient sequential but less parallel-computing-friendly method. When the modified algorithm is used in the slider bearing optimization, a parallel efficiency of 96.3% is obtained in the 16-computing-node cluster. This study presents the modified DIRECT algorithm, an efficient parallel search method, for general engineering optimization problems.
The Endochronic Viscoplasticity for Sn/3.9Ag/0.6Cu Solder Under Low Strain Rate Fatigue Loading Coupled with Thermal Cycling
Authors: Lee C. F. , Lee Z. H. , Ou S. H.
Published: May 2011

In this paper a wide range of temp. dependent kernel function ρ(Z) and the strain-rate function h(, T) in the Endochronic viscoplasticity were established first by using experimental steady hysteresis loops of Wei et. al., for Sn/3.9Ag/0.6Cu Solder at fixed 298K or 373K and strain rate at 10−3, 10−4 and 10−51/s; and then extended to predict the thermomechanical behavior of solder under constant low strain rate (10−51/s), from 0 to 1% max. strain fatigue loading with in-phase thermal cycling between 298K and 373K.

A novel approach in the theory to account for the microstructural changes enhanced by the stressassisted grain boundary diffusion mechanism during thermal cycling was proposed by using a partial relaxation function h1(T) of back stress (i.e. ρ0 in ρ(Z)).The theoretical results were in very well agreement with experimental data. These results and the out-phase results from the present theory were new and might be used as references to compare with results derived from other theories.
Leg and Joint Stiffness in Patients with Bilateral Medial Knee Osteoarthritis During Level Walking
Authors: Wei I-P. , Hsu W.-C. , Chien H.-L. , Chang C.-F. , Liu Y.-H. , Ho T.-J. , Wang T.-M. , Lin J.-G. , Lu T.-W.
Published: May 2011

Knowledge of the control of the musculoskeletal system in patients with knee osteoarthritis (OA) during gait is helpful for the development of intervention programs in the management of these patients. The current study aimed to investigate the leg and joint stiffness, aswell as the associated joint kinematics and kinetics, in patients with bilateral medial knee OA during gait. Joint angles, moments and stiffness, as well as leg stiffness from fifteen patients with bilateral knee OA and fifteen normal controls during level walking, were obtained and their values at the beginning and end of single leg stance were compared using a t-test.

Patients with knee OA were found to modulate their leg and joint stiffness through acquired specific biomechanical strategies in order to maintain normal temporal-spatial patterns of gait. During weight acceptance, they increased their leg stiffness with increased knee stiffness but unalterd hip and ankle stiffness. During weight release, they modulated their hip and ankle kinetics with increased knee and ankle stiffness to improve the control stability of the limb with unaltered leg stiffness. It is suggested that muscle strengthening exercise intervention and/or rehabilitation for patients with knee OA should focus on activities that develop and/or maintain functions not only of the knee, but also of the overall lower extremity.
Experimental Study of the Heat Transfer Across Periodically Contacting Surfaces
Authors: Goudarzi K. , Shojaeefard M. H.
Published: May 2011

An experimental study for determining the thermal contact conductance between two periodically contacting surfaces is presented. The influence of the frequency of contact upon the thermal contact conductance is investigated. Also, the results show that the thermal contactconductance decreases as the frequency of contact increases. The experimental results obtained from present work are in agreement with the previous published data.