bluuebunny/crossref_metadata_2025_split huggingface dataset:
Limitations on the Use of Effective Properties for Multicomponent Materials
Authors: Han R. , Ingber M. S. , Hsiao S. C. 
Published: May 2011

ABSTRACTMulticomponent 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

ABSTRACTThe 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

ABSTRACTThis 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

ABSTRACTThe 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

ABSTRACTThis 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.
Wave Equations of Elastic Type-II Superconductors
Authors: Chen K. C. , Yeh C.S. 
Published: May 2011

ABSTRACTIt 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

ABSTRACTDuring 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

ABSTRACTAn 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

ABSTRACTThis 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

ABSTRACTThe 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

ABSTRACTTo 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

ABSTRACTA 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

ABSTRACTThis 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

ABSTRACTThis 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

ABSTRACTTo 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

AbstractIn 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

AbstractBased 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

AbstractThis 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

AbstractA 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.