bluuebunny/crossref_metadata_2025_split huggingface dataset:
Thermal Stress Analysis of Thermally-Enhanced Plastic Ball Grid Array Electronic Packaging
Authors: Yeh Meng-Kao , Chiang Kuo-Ning , Su Jiann-An 
Published: May 2011

ABSTRACTThe thermally enhanced ball grid array (TEBGA) electronic packaging under thermal cycling and thermal loading was investigated numerically. Two-dimensional finite element analysis by ANSYS was used for calculating the temperature distribution and thermal stress on the symmetric and diagonal cross sections of TEBGA. The thermal failure based on the peel and shear stresses at interfaces of TEBGA took place at the interface between the heat sink and epoxy moulding compound. The Tasi-Hill failure criterion was modified to predict the failure at various interfaces in TEBGA package. The TEBGA geometric parameters, including the thickness of the heat sink, the thickness of the adhesive layer between the heat sink and the die, and the thickness of the reinforcing copper ring, were varied to assess their effects on the failure mode of TEBGA. The results showed that for a TEBGA under thermal cycling, the stress values were reduced for thicker adhesive layers and thinner heat sinks; for a TEBGA under thermal loading, the die-to-ambient thermal resistance of TEBGA decreased for thinner adhesive layers and thicker heat sinks. The slimmer heat sink of extruded plate type can dissipate more heat and can reduce the stress values. Proper choice of geometric parameters of TEBGA package can prevent its failure at interfaces and furthermore, improve the reliability of electronic packaging.
Optimal Distal Screw Alignment in the Gamma Nail
Authors: Chao Ching-Kong , Hsiao Chun-Ching , Chen Po-Quang 
Published: May 2011

AbstractThe effect of stress distribution due to the changes of the distal screw alignment in relation to the Gamma nail and the femoral shaft is thoroughly studied in this paper. Failure of the Gamma nail composite occurs through the cranial aperture of the distal screws and the insertion hole for the lag screw due to nonunion, delayed-union and continued weight-bearing. A three-dimensional finite element model was used to study the fractured femur, the Gamma nail, the lag screw and the distal locking screws. The first and the second distal screws were inserted into the Gamma nail in four different configurations. We found that the stress of the Gamma nail composite was substantially reduced with the two screws configured in the anterior to posterior direction. This alignment can bear greater loading in the more demanding fracture types. In the subtrochanteric fracture or the comminuted fractures at the proximal femur, the optimal alignment of the two distal screws was in the anterior to posterior direction.
In-Plane Bending Fracture of a Large Beam Containing a Circular-Arc Crack
Authors: Shiah Y. C. , Fang Jiunn , Wei Chin-Yi , Liang Y.C. 
Published: May 2011

AbstractIn this paper, the crack problem of a large beam-like strip weakened by a circular arc crack with in-plane bending moments applied at both ends is approximately solved using the complex variable technique. Complex stress functions corresponding to the applied bending moments are superposed with those due to the disturbance of the crack to satisfy the governing boundary equation. The conformal mapping function devised to transform the contour surface of a circular arc crack to a unit circle is then substituted in the boundary equation to facilitate the evaluation of Cauchy integrals. In this way, the complex stress functions due to the crack disturbance are determined and the stress intensity factors are calculated through a limiting process to give their explicit forms. Eventually, the geometric functions for the variation of the stress intensity factors on account of the crack shape are plotted as a function of the curvature of a circular-arc crack.
The Unsteady Viscous Flow Generated by an Oscillating Porous Plate
Authors: Liu C.-M. , Hwung H.-H. , Kong C.-H. 
Published: May 2011

ABSTRACTThe flow of a viscous still fluid disturbed by an oscillating porous plate with an arbitrary initial phase is investigated. Using the Laplace transform, the exact solution of the velocity profile is revisited. Subsequently, the wall stress implying the required driving force is derived in this study. The solutions are valid not only for large times but also for small times. Four special cases are discussed to investigate the influences of four parameters on the development of the flow. A dimensionless analysis for general cases is also provided. Our analyses significantly stress on the following subjects. Firstly, the porous velocity and the decay factor affecting the development of the flow are studied. Secondly, the occurrence time of separation and the corresponding critical condition are investigated. The period of the transient velocity influenced by the Reynolds number and the initial phase is discussed. Present study includes many existing solutions as special cases. Results can be also applied to many engineering problems with the same PDE form and boundary conditions. In conclusion, this study presents the detailed discussions and the magnitude of the required driving force which were missed in previous works.
Molecular Dynamic Simulation of Escape of Hydrogen Atoms from (5, 5) Carbon Nanotubes
Authors: Wang C. S. , Chen J. S. , Wang Y. C. , Lee J. , Chyou Y. P. 
Published: May 2011

ABSTRACTIn this article the mass and heat transfer between fluid molecule and carbon tube is studied via molecular dynamic simulation based on Lennard-Jones Potentia and Bernner-Tersoff Potential model. Some valve holes are formed by removing different numbers of molecules from flank of (5, 5) armchair carbon tube (the hole area = 17.3 ∼ 116.9Å2). The results indicate that only diffusion behavior is not able to describe the phenomena, otherwise the atom release rate and valve hole size are interdependent. Meanwhile the variation of potential energy barrier, work function, energy gap arose from different valve geometrical size are observed. These variations can influence the dynamic behavior such as flow rate and velocity by molecule penetration.
Nonlinear Panel Flutter of Composite Sandwich Plates with Thermal Effect
Authors: Shiau L.-C. , Kuo S.-Y. 
Published: May 2011

ABSTRACTBy considering the total transverse displacement of a sandwich plate as the sum of the displacement due to bending of the plate and that due to shear deformation of the core, a high precision higher order triangular plate element is developed for the nonlinear panel flutter analysis of thermally buckled sandwich plates. Von Karman large deformation assumptions and quasi-steady aerodynamic theory are employed for the analysis. Newmark numerical time integration method is applied to solve the nonlinear governing equations in time domain. Results show that temperature will increase both the maximum displacement and motion speed of the plate. But the maximum displacement and velocity of the plate will not vary much with the aerodynamic pressure. Buckle pattern change phenomenon occurred in some specific case will increase the flutter boundary and change the flutter motion type of the plate. Temperature gradient increases the overall stiffness of the plate, which in turn stabilizes the sandwich panel and increases the flutter boundary of the plate.
Shear Horizontal Piezoelectric Waves in a Piezoceramic Plate Imperfectly Bonded to Two Piezoceramic Half-Spaces
Authors: Chen Z. G. , Hu Y. T. , Yang J. S. 
Published: May 2011

ABSTRACTWe analyze the propagation of shear horizontal (SH) piezoelectric waves guided by a plate of polarized piezoceramics between two piezoceramic half-spaces with imperfectly bonded interfaces. The interfaces are described by the so-called shear-lag model with an elastic constant characterizing the interface physical behavior. Exact dispersion relations are obtained. It is found that the waves are sensitive to the physical nature of the interfaces. The results are useful for acoustic wave devices.
Failure Mechanism and Bearing Capacity of Shallow Foundation on Poorly Cemented Sandstone
Authors: Chang J.-C. , Liao J.-J. , Pan Y.-W. 
Published: May 2011

AbstractThis paper aims to investigate the failure mechanism of a shallow foundation on poorly cemented sandstone and to propose an upper bound solution for the bearing capacity of the foundation. A series of laboratory material and load-bearing model tests with specimens made of artificial rock mimic undisturbed natural poorly cemented sandstone.Based on a series of load-bearing model tests, bearing behavior and progressive failure mechanisms are investigated. It was found that the bearing behavior on poorly cemented sandstone is distinct from the cases on hard rock or on soil, and exhibits both plasticity and brittle characteristics. It is noted that the bearing capacity formulas for a shallow foundation commonly used for soil or hard rock are not appropriate for the case of poorly cemented soft sandstone. Based on the observed failure mechanism, a simplified plastic collapse mechanism is proposed and an upper-bound solution on the basis of a multi-block translation mechanism is formulated. It is shown that the upper bound solution agrees well with the experimental bearing capacity as long as a proper non-associated flow rule is adopted.
Vortex Simulations of the Flow-Field of a Flat Plate with a Non-Zero Angle of Attack
Authors: Hsu C.-C. , Huang C.-I 
Published: May 2011

AbstractA Lagrangian style vortex simulation technique is used to study the flow fields past a stationary flat plate at various angles of attack in the range 1° to 90°. Time mean values of oscillating lift and drag coefficients, and the Strouhal number versus angle of attack are computed and compared with experimental results. Time-mean and root-mean-square values of stream-wise and transverse velocities in the wake region are also calculated. Self-similar defect velocity distribution is obtained far downstream. Owing to the interaction of free shear layers, highly root-mean-square values of velocities appear at the downstream vertex of the triangular low velocity region, which exits behind an inclined flat plate.
Heat Transfer of Confined Circular Jet Impingement
Authors: Hsieh Shou-Shing , Huang Jung-Tai , Tsai Huang-Hsiu 
Published: May 2011

ABSTRACTExperiments for heat transfer characteristics of confined circular single jet impingement were conducted. The effect of jet Reynolds number, jet hole-to-plate spacing and heat flux levels on heat transfer characteristics of the heated target surface was examined and presented. The local heat transfer coefficient along the surface is measured and correlations of the stagnation point, local and average Nusselt number are developed and discussed. Finally, comparisons of the present data with existing results were also made.
The Endochronic Approach for Structural Steel Subjected to Cyclic Loading
Authors: Lu Jun-Kai , Ji Nai-Kuan 
Published: May 2011

ABSTRACTThe A36 structural steel shows significant Baushinger effect under cyclic loading. Present paper modifies the anisotropic endochronic model to describe the behaviors of the A36 structural steel subjected to cyclic loading. The deformation induced anisotropy has been considered to modify the definition of the intrinsic time. Also, the different hardening functions are used with respect to the mechanical behavior under loading and unloading condition, respectively. Then, the presented constitutive equations are used to describe the mechanical behaviors of the A36 structural steel under different cyclic strain paths. The theoretical results are compared with the experimental data. The test investigated includes several different cyclic uniaxial and axial-torsional loading experiments from Hong and his co-workers. It is shown that the present model is capable of describing the anisotropic behaviors of A36 structural steel well.
Thermal Stress in Discretely Layered Structures with Functional Graded Materials
Authors: Hwang S.-F. , Liao W.-T. 
Published: May 2011

AbstractFunctional graded materials are generally provided in discretely layered structures to reduce the abrupt mismatch and to improve failure performance. To investigate the thermal stress singularity occurring at the intersection of an interface and a free end, two-dimensional and three-dimensional finite element analyses are performed for titanium and aluminum layers with or without functional graded materials. The results indicate that once the functional graded material is added, the stress singularity around the intersection of an interface and a free end could be significantly relieved. If more FGM layers are used, the stress singularity could be further reduced to a very small value. If the longitudinal normal stresses and interlaminar shear stress are considered, two-dimensional finite element analysis may be enough, while three-dimensional analysis is necessary for the interlaminar normal stress. Otherwise, one may underestimate its stress singularity.
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

AbstractThirty 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

AbstractThis 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

AbstractThis 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

AbstractBased 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

AbstractIn 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

AbstractThis 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

AbstractAnalytical 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

AbstractIn 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

AbstractThis 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.