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

A rather complete dynamic model with special emphases on nonlinear conicity and creep force and in consideration of random irregularity of rail profile is proposed to simulate the response and investigate the ride quality of railway vehicles. The CP341 vehicle that will soon be used in Taipei Rapid Transit System is considered in particular as the studied role model. Some of the field test data carried out for this type of vehicle are revealed as well and used for the verification of the proposed model. Both simulation and test results show that the resonant frequency of the studied vehicle is in the range of 0.6∼1 Hz, and the one-third octave root-mean-square acceleration curves of the vehicle in all studied cases meet the ride quality criteria set for the mass rapid transit vehicle systems. It is observed that the secondary suspension of the vehicle has the low frequency filtering property and the primary suspension has high frequency characteristics. A poorer ride quality in vertical direction rather than in lateral direction is also confirmed in the study. It is concluded that the proposed model can be used to simulate the dynamic response and evaluate the ride quality of any railway vehicle.

The mixing properties of various orders of fluctuation correlations are investigated in the present paper for a rarefied gas free shear layer at hypersonic speed. The molecular kinetic theory and the direct simulation Monte Carlo (DSMC) method are employed for the present calculations. The Reynolds average process is assumed in obtaining the correlation functions. The results show that flow field structure was very similar to that of continuum flow ones at high Reynolds numbers. The probability density functions (pdf) in velocity space f(u′),f(v′), and f(u′, v′) are also calculated to counter explain the distributions of the correlation functions in the mixing layer. From the calculated distributions of the fluctuation correlation functions, <u′v′>, <u′2v′>, and <v′2u′>, one can find that the distributions behave similar to the turbulent transport phenomena in that of a continuum flow one. The distributions of the fluctuation correlation functions, <u′, v′> is described via the joint probability density function, f(u′, v′). The behavior of the higher-order fluctuation correlation functions, <u′2v′>, <u′3> and <u′4 >, are also explained via the probability density function.

Chaos theory has been seen as an efficient tool for studying the turbulent flow, the findings of attractor were also important and made in the study to investigate the wake flow behind the bluff body. Here, the fractal dimension value would then be found by Hurst analysis. According to the results found, the Hurst empirical formula derived by the self-similar laceration of vortex plane would be applied by self-similar property to decide the band of the frequency variations in the vortex shedding process. The three kinds of flow mode with their individual attractors and characteristics could be decomposed and shown as following: self-similar laceration, energy input and white noise band. Finally, the energy ratio for the three kinds of flow mode had been confirmed. Hence, these findings would be helpful to further study the wake flow in the vortex shedding process.

Pullout tests of bone screws have been performed on cadaver bones, animal bones or synthetic bones. These materials have been proven to be poor models from experimental observation, giving results with too much variability or difference. The finite element method was used in this study to evaluate the holding power for bone screws subject to the changes of outer diameter, inner diameter, pitch and radiuses of tip and bottom round corner. The displacement control mode was used in a way that 1 mm displacement was applied on the flatness region of bone screw head and the reaction force was then recorded to simulate the ability of pullout force. Numerical results showed that the patterns of tip corner on the bone screw were a deciding factor on the pullout force of bone screw. This study was significant for establishing a good bone-screw FEM model and suggesting important threaded parameters in selecting or manufacturing a bone screw to increase its holding power.

The hygrothermal-mechanical behavior of a quad flat non-lead (QFN) package without a chip inside is investigated experimentally and numerically. The present study is focused on understanding the effect of the inherent hygrothermal behaviors of epoxy molding compound (EMC) on the deformations of QFN package. Prior to studying the package, the coefficient of moisture expansion for the EMC is measured experimentally. Full-field moiré and Twyman-Green interferometries are used for measuring the real-time in-plane and out-of-plane deformations of the specimen, respectively, under thermal and moisture loading. In addition, the finite element and theoretical analyses are adopted for validating the experimental observations and further understanding the hygrothermal mechanics of the specimen. The coefficient of moisture expansion of the EMC was experimentally obtained to be about 0.2. The experimental results of the full-field deformations of the specimen, due to temperature, moisture and a combination of both, are presented. The experimental observations are validated by the finite element and theoretical analyses. It was observed that the maximum moisture-induced deformation (strain) can be up to as large as 50% of the thermal deformation (strain) caused by ΔT = 50°C for the specimen. As a result, neglecting moisture-induced deformations (strains) would cause the significant amount of error in thermal deformation (strain) measurement of plastic packages. Furthermore, the present study has laid down the fundamental mechanics and approaches for the QFN packaging structural design and analysis in terms of hygrothermal effects.

In this paper, a theory of Endochronic cyclic viscoplasticity of eutectic Tin/Lead (60Sn/40Pb) solder alloy under cyclically thermomechanical strain histories had been established. Under the conditions of isotropic and inelastically incompressible small deformation, the constitutive equation of deviatoric behavior was expressed as:

here and the strain rate dependent intrinsic time scale and . Employing the experimental cyclic shear stress-strain curves of various testing temperature and frequency, all temp. dependent material parameters and ; and the temp.-freq. dependent material function were determined for temp. between 213K and 423K and freq. between 0.3Hz and 0.01Hz. Predicative capability of the theory were then challenged by a set of experiments with complicate strain history such as (i) Fast in tension/Slow in compression constant strain amplitude cyclic tests (ii) Slow-Fast-Slow constant amplitude cyclic tests. Through the excellent computational results, the present theory demonstrated that it can, not only play a vital role in the area of electronic solder mechanics, but also meet the needs of reliability analysis and life assessment in the electronic/photoelectronic packagings.

With rapidly increasing use of piezoelectric materials in high-temperature environment, it is becoming increasingly important for reliable design of piezoelectric devices to study thermo-electroelastic damage and fracture mechanism. As the first step, a thermo-piezoelectric damage constitutive model is presented from continuum damage mechanics and effective properties of a damaged material are connected with both damages and the initial coefficients according to the theorem of energy equivalence in this paper. Then the finite element equations for a thermo-electroelastic damage problem are given by use of the virtual work principle. Finally, as a numerical illustration example, damage fields around a crack-tip in a three-point bending PZT-5H beam subjected to different thermal loads are calculated and analyzed. It is shown from both the damage curves and contours that influence of environmental temperature on the mechanical damage distribution is great but slight on the electrical damage.

Parameters of thermohydrodynamic (THD) lubrication are discussed for the laminar and turbulent regimes. The scales of pressure of temperature are analytically obtained, and are used to measure the variations of density and viscosity. Dominant THD parameters are identified by inspecting the practical applications.

This paper was an attempt to investigate, through numerical simulation, the designs of DEP flow sorters when applied with different ratios of the electrodes to generate different electrical fields, and to explore the sorting capability of the flow sorters, defined as the degree of particle deflection, under different operation of parameters.

In order to obtain the maximal DEP negative particle deflection, which was believed as an indicator of greater sorting capability, we have investigated different non-uniform electrical fields produced by combinations of electrodes with different length of two poles, ranging from 1:2 up to 1:9. The finding of numerical simulation indicated that the length ratio 1:3 of the electrode poles produced the electrical fields that maximized the particle deflection.

Moreover, different parameters of applied voltage, flow rate, particle diameters, and distance between two electrical poles were designed to investigate their effects on particle deflection of flow sorters. The numerical simulation of the study showed that the DEP flow sorter was demonstrated as a linear system with respect to the applied voltage and particle diameter. In this study, we tried to operationally define flow rate as the time duration while the flow passed the electrical fields, and thus investigated how particle deflect with the different time given. We found that the particle deflected more when the flow was allowed with longer time to pass the electrical fields. The study also showed that the distance the particles deflect from the centerline is in inverse proportion to the square distance between the two electrical poles.

Low-frequency variations in wake flow are complex and many aspects of its behavior remain poorly understood. A mode decomposition method developed by Huang et al is utilized herein because it can decompose any complicated data set into a finite number of intrinsic modes without distorting their original characteristics. The results of decomposition analysis of the measured base pressure signals reveal that a finite number of various kinds of flow structure modes, with their own characteristic time scales, coexist with the residue that exhibits most of the low-frequency variations in flow at Re = 11760 and 31600, respectively. As the Reynolds number increases, the decomposition method yields more components. Results also show exactly the vortex shedding structure in an intrinsic mode and the low-frequency variations that appear in the residue during vortex shedding process.

In this study, a simplified method for evaluating amount of deflection for the tooth of worm and worm gear under loading is proposed. In a previous study, the plate theory was used for the approximation. However, it was found that the deflection of gear tooth using the plate theory was far from the actual value, and that the values from 3D FE analyses were closer to the actual value than from the plate theory. However, the FE analysis process starting from the CAD model to the final analysis results is complicated and too time-consuming. Therefore, the form factors are needed to facilitate simple but accurate results for the design purpose. In this study, the equations of form factors obtained from the results of plate theory and the 3D FEM, are developed. Since the worm gear assembly has various tooth geometries, the moment of inertia and the deflection of tooth geometry are different. Therefore, tooth geometries with trapezoid and involute forms are investigated.

This paper presents the theoretical modal analysis for the use of PVDF sensor in structural modal testing via finite element analysis (FEA). A series of rectangular PVDF films are adhered on the surface of cantilever beam as sensors, while the point impact force is applied as the actuator for experimental modal analysis (EMA). Natural frequencies and mode shapes determined from both FEA and EMA are validated. In FEA, the beam structure is modeled by 3D solid elements, and the PVDF films are modeled by 3D coupled field piezoelectric elements. Both modal analysis and harmonic response analysis are performed to obtain the structural modal parameters and frequency response functions, respectively. Results show that both FEA and EMA results agree well. In particular, the PVDF sensor mode shapes, proportional to the slope difference between the two edges of PVDF film, are numerically and experimentally validated by FEA and EMA, respectively. Therefore, the simulation of PVDF films for vibration analysis in FEA can be verified and easily extended to other complex structures that may contain piezoelectric materials.

In this paper, a simpler formulation for the nonlinear motion analysis of reticulated space truss structures is developed by applying a new concept of computational mechanics, named the vector form intrinsic finite element (VFIFE or V-5) method. The V-5 method models the analyzed domain to be composed by finite particles and the Newton's second law is applied to describe each particle's motion. By tracing the motions of all the mass particles in the space, it can simulate the large geometrical and material nonlinear changes during the motion of structure without using geometrical stiffness matrix and iterations. The analysis procedure is vastly simple, accurate, and versatile. The formulation of VFIFE type space truss element includes a new description of the kinematics that can handle large rotation and large deformation, and includes a set of deformation coordinates for each time increment used to describe the shape functions and internal nodal forces. A convected material frame and an explicit time integration scheme for the solution procedures are also adopted. Numerical examples are presented to demonstrate capabilities and accuracy of the V-5 method on the nonlinear dynamic stability analysis of space truss structures.

The effective length of a piezoelectric cylindrical specimen in strain measurements is determined by considering the stress decay in a cylindrically anisotropic, circular cylinders of piezoelectric materials subjected to 2D surface tractions and prescribed end loads. On the basis of the state space formalism, the problem is studied by means of matrix algebra. The significance of the end effects is evaluated through a characteristic decay length. The study enables us to assess Saint-Venant's principle as applied to piezoelectricity in general and to determine the effective lengths of tensile and torsional specimens of piezoelectric materials in particular.

The normal function of the knee relies upon a complicated and delicate mechanical interaction between the force-bearing structures, including muscles, ligaments and articular surfaces. Injury or damage to any of these structures will lead to the degradation or loss of joint function. Stair locomotion is one of the most common forms of motion in daily living. The purposes of the study were to analyze forces transmitted by the force-bearing structures of the knee during normal stair ascent and descent and to evaluate their mechanical differences. Compared to stair descent, higher peak patellar tendon forces, peak flexor forces, posterior cruciate ligament (PCL) forces and contact forces were required during stair ascent. In contrast, the anterior cruciate ligament (ACL) trended to bear higher forces during stair descent. It is suggested that one should be cautious in the use of stair ascent and descent as a rehabilitation exercise for patients with injuries or diseases of the cruciate ligaments and articular surfaces. The results of the study will be helpful for the understanding of the normal mechanics of the knee during stair locomotion, contributing to the design and evaluation of rehabilitation programs for patients with knee problems such as ACL injury and osteoarthritis.

In this study, physical and numerical models were used to analyze pipe-soil interaction during pipejacking work. After calibrating with the physical modeling results, the finite element software ABAQUS [1] was used to study the pipejacking related behavior, such as surface subsidence, failure mechanism, pipe-soil interaction, etc. The results show that the driving force in the tunnelling face is very important and critical for pipejacking. Surface subsidence is mainly due to the lack of driving force, however, excessive driving force could cause the unfavorable surface heaving problem. It also suggests that the depth of the pipe is critical to determine a proper driving force to stabilize the tunnelling face.

The flows past a square cylinder in a channel are simulated using the multi-relaxation-time (MRT) model in the parallel lattice Boltzmann BGK method (LBGK). Reynolds numbers of the flow are in the range of 100 ∼ 1,850 with blockage ratio, 1/6, of cylinder height to channel height, in which the single-relaxation-time (SRT) scheme is not able to converge at higher Reynolds numbers. Computed results are compared with those obtained using the SRT scheme where it can converge. In addition, computed Strouhal numbers compare reasonably well with the numerical results of Davis (1984).

The paper investigates the stability of thin film flow from a liquid jet impinging on a circular concentric disk using a long-wave perturbation method to solve for the generalized nonlinear kinematic equations of free film interface. To begin with a normal mode approach is employed to obtain the linear stability solution for the film flow. In the linear stability solutions only subcritical region can be resolved. In other words, no solution of supercritical region can be obtained in linear domain. Furthermore, the role that the forces of gravitation and surface tension play in the flow is nothing but to stabilize the system. To further investigate the realistic impinging jet flow stability conditions, the weak nonlinear dynamics of a film flow is studied by using the method of multiple scales. Various subcritical nonlinear behaviors expressed in terms of absolute stability, conditional stability and explosive instability can be characterized by solving the Ginzburg-Landau equation. It is found that the jet flow will become relatively unstable for an increasing Reynolds number, a relative smaller distance from the center of the impinging jet on the disk and a smaller diameter of the exit jet. It is also concluded that the flow will always stay in a subcritical instability region if the characteristic diameter of the potential core at nozzle exit is less than 0.01mm for the numerical conditions given in this paper. In such a case when the amplitude of external flow disturbance is smaller than the threshold amplitude a stable jet flow can be ensured.

This paper is concerned with linear and buckling analyses of composite beams with partial shear connection (partial composite beams) using the finite element method. Two elements derived from different types of shape functions are proposed in this study. The first element, referred to as exact, is based on the exact shape functions obtained by solving the differential equations governing the transverse displacement and the slip of the shear connector layer of a partial composite beam. The second element, referred to as approximate, is based on the conventional linear and cubic shape functions used in conventional axial and beam elements. By making use of these two types of shape functions, the elastic and geometric stiffness matrices can be derived explicitly from the strain energy and the load potential, respectively. Both types of elements can be used to carry out linear static and buckling analyses. As expected, the exact element is more accurate than the approximate element if the same discretization is adopted. However, the approximate element has the advantage of easy implementation since the expressions of its elastic and geometric stiffness matrices are very simple. Also, the solutions obtained from the approximate element converge very fast; with reasonable discretization, say 8 elements per member, very accurate solutions can be obtained.