A numerical analysis of the unsteady flows in conical microdiffusers appropriate for valveless micropump applications is performed. The rectification efficiency of the diffuser valve is calculated directly as a function of geometric and operational parameters, including diffuser angle, diffuser slenderness, sizes of actuation chamber and inlet/outlet port, actuation frequency, and amplitude of actuation pressure. The computational results show that the diffuser with diverging angle of 10° and slenderness of 7.5 has the best rectification performance. For large actuation pressure amplitude, the optimal rectification efficiency and its corresponding Roshko number are relatively high. At the optimal Roshko number, the flow impedance is found to be dominated by fluid inertia. Sizes of the pump chamber and inlet/outlet port are shown to have a prominent effect on valve performance. Small actuation chamber or small inlet/outlet port can significantly deteriorate the valving performance of the diffuser.

A three-dimensional aggregate generation and packing algorithm applicable for modeling asphalt mixture with high content of graded aggregates is presented in this paper. In the algorithm, arbitrary-shaped polyhedra are used to model aggregates, so that the effect of aggregate shape on the mechanical performance of asphalt mixture can be considered. The algorithm consists of two steps: Aggregate generation and packing. Polyhedra are created by extending triangular fundaments and treated as visualized aggregates after passing through convex control and sharpness judgment. After that, graded aggregates are taken out from the aggregate base and randomly packed in a given cylindrical or cubical region one by one equiprobably. Overlapping between nearby aggregates is avoided by the help of Boolean partition operation in ANSYS. Finally, some asphalt mixture samples with a given gradation are modeled as examples, and their effective elastic properties and creep behaviors under uniaxial compression are simulated.

Free vibration analysis of rotating composite laminated conical shells with different boundary conditions using the generalized differential quadrature method (GDQM), is investigated. Equations of motion are derived based on Love's first approximation theory by taking the effects of initial hoop tension and the centrifugal and Coriolis acceleration due to rotation and initial uniform pressure load into account. Then, the equations of motion as well as the boundary condition equations are transformed into a set of algebraic equation applying the GDQM. The results are obtained for the frequency characteristics of different orthotropic parameters, rotating velocities, cone angles and boundary conditions. The presented results are compared with those available in the literature and good agreements are achieved.

Due to a lack of closed-form solutions for three dimensional anisotropic bodies, the computational burden of evaluating the fundamental solutions in the boundary element method (BEM) has been a research focus over the years. In engineering practice, transversely isotropic material has gained popularity in the use of composites. As a degenerate case of the generally anisotropic material, transverse isotropy still needs to be treated separately to ease the computations. This paper aims to investigate the computational efficiency of the BEM implementations for 3D anisotropic, transversely isotropic, and isotropic bodies. For evaluating the fundamental solutions of 3D anisotropy, the explicit formulations reported in [1,2] are implemented. For treating transversely isotropic materials, numerous closed form solutions have been reported in the literature. For the present study, the formulations presented by Pan and Chou [3] are particularly employed. At the end, a numerical example is presented to compare the computational efficiency of the three cases and to demonstrate how the CPU time varies with the number of meshes.

We present the development of a MEMS piezoelectric bimorph generator, a cantilever type bimorph which was formed by laminating two PZT piezoelectric layers. Our bimorph generator can scavenge mechanical energy from ambient vibrations and transform it into useful electrical energy. Two poling configurations of the PZT piezoelectric layers of our bimorph MEMS generator were fabricated and tested. A tip proof mass used for adjusting the resonance frequency was also demonstrated. Experimental results confirm that our device possessed a maximum open-circuit output voltage of 1.91VP-P and a 3.42VP-P for a parallel polarization device and a serial polarization device, respectively with a 2g externally applied vibration. At an optimal resistive load, the maximum output power was 1.548μ–W and 1.778μ–W for a parallel polarization device and a serial polarization device, respectively.

The induced magnetic fields generated by a line mechanical singularity in a magnetized anisotropic half plane are considered in this paper. The linear theory for a soft ferromagnetic elastic with multidomain structure, which has been developed by Pao and Yeh [1] is adopted to investigate this problem. By applying the Fourier transform technique, the exact solutions for the generated magnetic inductions due to various mechanical singularities such as single force, a dipole, single couple and dislocation are obtained in a closed form. The distributions of the generated inductions on the surface are shown graphically.

In this paper, the interaction of a generalized screw dislocation with multiple circular inclusions perfectly bonded to an unbounded matrix under remote magnetoelectromechanical loadings is dealt with. The analytical solutions of electric field, magnetic field and displacement field either in the inclusions or the matrix are obtained by use of the complex variable method. The image force acting on the magnetoelectric screw dislocation is calculated by using the generalized Peach-Koehler formula. Finally, the influence of material combinations on the image force is examined for several practical examples. The obtained solutions can be used as Green's functions for the analysis of the corresponding magnetoelectric crack problem.

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

External wrist fixators have been widely used to stabilize distal radial fractures. Ideally an external fixator would create a stable environment for the fracture to heal while allowing proper mobility for the wrist. However, this has been a great challenge to the designers.

The current study aimed to develop a bridging wrist external fixator that is easy for surgeons to create a stable environment for the fracture to heal while allowing proper wrist mobility for rehabilitative purposes. The kinematic geometry of the wrist-fixator system was described using loop equations defined by homogeneous transformation matrices (HTM) of the joints involved, and was evaluated numerically for a set of system parameters that are determined by surgeons during surgery. The results were validated with geometric models and computer simulation. The contributions of individual clinical parameters to the kinematic geometry of the wrist-fixator system were also analyzed using the Taguchi method.

Adequate pin placement and hinge alignment function were found to be critical for the postoperative bridged wrist motion. The results of the current study will be helpful for surgeons to perform fixation using the new wrist fixator and for designers to design new fixators in the future.

This study presents an analytical model for describing propagation of Rayleigh waves along the impermeable surface of an unsaturated poroelastic half-space. This model is based on the existence of the three modes of dilatational waves which employ the poroelastic equations developed for a porous medium containing two immiscible viscous compressible fluids (Lo, Sposito and Majer, [13]). In a two-fluid saturated medium, the three Rayleigh waves induced by the three dilatational waves can be expressed as R1, R2, and R3 waves in descending order of phase speed magnitude. As the excitation frequency and water saturation are given, the dispersion equation of a cubic polynomial can be solved numerically to obtain the phase speeds and attenuation coefficients of the R1, R2, and R3 waves. The numerical results show the phase speed of the R1 wave is frequency independent (non-dispersive). Comparatively, the R1 wave speed is 93 ∼ 95% of the shear wave speed, and 28% to 49% of the first dilatational wave speed for selected frequencies between 50Hz & 200Hz and relative water saturation ranging from 0.01 to 0.99. However, the R2 and R3 waves are dispersive at the frequencies examined. The ratios of R2 and R3 wave phase speeds to the second and third dilatational wave speeds fall between 56% and 90%. The R1 wave attenuates the least while the R3 wave has the highest attenuation coefficient. Furthermore, the phase speed of the R1 wave under an impermeable surface approaches 1.01 ∼ 1.37 times of the R1 wave under a permeable boundary. Impermeability has significant influence on the phase speeds and attenuation coefficients of the R1 and R2 waves at high water saturation due to the existence of confined fluids.

A number of factors affect rail vehicle steel wheels. Kinematic oscillations uncovered by Klingel, is amongst the parameters affecting dynamic behaviour of the wheelset. Normal and tangential forces are also included within the wheel/rail interface. Geometry and material properties of the contacting bodies are within these parameters. Altogether, these inputs to the rail/wheel system can result in plastic deformation and wear. The authors of this paper make their attempts to introduce a noble study including a harmonic wear pattern in circumference of the flange region when contacting the rail gauge corner. Theoretical aspects of this harmonic pattern are then developed and presented.

We consider an arbitrarily curved three-dimensional thin interphase with surface stresses between two anisotropic solids. Letting the interphase be infinitely thin and assuming that the kinematic constraints between the two anisotropic solids remain intact during the deformation, we derive the interface jump conditions along the interface. These conditions are derived analytically in general non-orthogonal curvilinear coordinates in the setting of linear elasticity and steady state conduction. The proof is made directly from a force balance consideration of a small element of the curved interface. Simplified results are also deduced for oblique coordinate systems in which the coordinate axes are straight lines that are not perpendicular to each other. When the axes are orthonormal, we prove that our results agree with the previous known Young-Laplace conditions in solids.

This paper studies a novel approach to optimize trusses and truss-like structures for minimum weight design. It is based on the force method of analysis which is incorporated inside the optimization routine. The design variables in force formulation are the member cross sectional areas and the redundant forces in each load condition. The optimization method used is the method of center points using the inscribed hyperspheres to the feasible-usable design space. By incorporating the analysis step as part of the optimization problem, a separate structural solution phase, which is necessary in all other methods, is avoided resulting in large computational savings. In this article the simplest form of structures i.e. trusses are treated to illustrate the efficacy of the method. Stress limits on the members as well as limitations on their sizes, and linking among them, under several load conditions have been considered. Combination of the method of center points and force formulation results in a viable routine for structural optimization. Comparison of the example results with those obtained by others clearly shows the effectiveness and novelty of the proposed method.

In Elastomeric foam materials find wide applications for their excellent energy absorption properties. The mechanical property of elastomeric foams is highly nonlinear and it is essential to implement mathematical constitutive models capable of accurate representation of the stress-strain responses of foams. A constitutive modeling method of defining hyperfoam strain energy function by a Simplex Strategy is presented in this work. This study will demonstrate that a strain energy function of finite hyperelasticity for compressible media is applicable to describe the elastic properties of open cell soft foams. This strain energy function is implemented in the FE-tool ABAQUS and proposed for high compressible soft foams. To determine this constitutive equation, experimental data from a uniaxial compression test are used. As the parameters in the constitutive equation are linked in a non-linear way, non-linear optimization routines are adopted. Moreover due to the in homogeneities of the deformation field of the uniaxial compression test, the quality function of the optimization routine has to be determined by an FE-tool. The appropriateness of the strain energy function is tested by a complex loading test.

By using the optimized parameters the FE-simulation of this test is in good accordance with the experimental data.

In this paper, the effect of delamination on free vibration of a simply supported rectangular homogeneous plate with through-width delamination was investigated by the finite strip method. A constrained model was used and a finite strip with bending and in-plane stiffness was derived for the free vibration analysis. The effects of delamination length, delamination location in the thickness-wise and spanwise directions, and aspect ratio of the plate on the natural frequencies of the plate were presented. Results show that the delamination has considerable effect on the natural frequencies of the plate. The aspect ratio of the plate is also having significant effect on the natural frequency of the plate, especially on the mode 2 frequency of the plate.

Fifteen young and fifteen older healthy adults walked and crossed obstacles of three different heights while kinematic data and ground reaction forces were acquired to calculate the three-dimensional motion of the centre of mass (COM) and lower limb joint moments. The older group had greater normalized jerk score of the COM. When the leading limb was crossing, the older group kept the COM more posterior and on the trailing stance limb for longer with increased knee extensor crossing moments and thus decreased anterioposterior COM deceleration. When the trailing limb was crossing, the older group decreased vertical COM deceleration through increased hip extensor crossing moments. The older group maintained the same COM motion as the young in the frontal plane with greater hip and knee abductor crossing moments. The older group exhibited significant kinetic changes in their locomotor system with increased muscular demand, leading to a more jerky motion of the body COM. However, these changes helped to maintain the frontal COM motion and to achieve a sagittal COM motion pattern which is thought to be helpful for a safe and successful obstacle-crossing. Failure to meet the kinetic demands in the elderly may increase the risk of falls during obstacle-crossing.

An analysis of the Poiseuille-Couette flow of two immiscible fluids between inclined parallel plates is investigated. One of the fluids is assumed to be electrically conducting while the other fluid and channel walls are assumed to be electrically insulating. The viscous and Ohmic dissipation terms are taken into account in the energy equation. The coupled nonlinear equations are solved both analytically valid for small values of the product of Prandtl number and Eckert number (= ε) and numerically valid for all ε. Solutions for large ε reveal a marked change on the flow and rate of heat transfer. The effects of various parameters such as Hartmann number, Grashof number, angle of inclination, ratios of viscosities, widths and thermal conductivities are presented and discussed in detail.

This paper is intended to present a preliminary framework for dynamic interaction analysis of a maglev (magnetically levitated) vehicle running on a two-span guideway using a comprehensive iterative approach. A maglev vehicle with electrodynamic suspension (EDS) system is simplified as a two degrees-of-freedom (2-DOF) maglev oscillator tuned by a PID (Proportional-Integral-Derivative) controller. The guideway is modeled as a two-span continuous beam with uniform section. Two sets of equations of motion are written, with the first set for the guideway and the second set for the maglev oscillator traveling on the guideway through a motion-dependent magnetic force. To achieve the stable levitation gap for a maglev vehicle moving on a flexible guideway, Ziegler-Nicholas (Z-N) tuning rules are used to determine the tuning parameters of the PID controller. Numerical simulations demonstrate that the levitation gap affects the dynamic response of the maglev vehicle while little influence on the guideway response since the inertial force of the moving maglev vehicle is much lower than its static load.

Friction compensation techniques are studied for control of a flexible-link robot based on the LuGre friction model. To overcome the problem of uncertain parameters in the friction model, adaptive control schemes are used for two different types of parametric uncertainties. A novel dual-observer technique is proposed to estimate the internal state inside the friction model. A distributed-parameter dynamic model is used for the flexible arm to design the controllers. The Lyapunov stability theorem is used to guarantee the global asymptotic stability of the controllers. The performance of position tracking and link vibration attenuation is verified through experimental results. The results also confirm the effectiveness of the proposed friction compensation schemes.

In this study, finite element modeling of composite beams with distributed piezoelectric sensors and actuators which is based upon a coupled electromechanical model has been considered. For modeling of mechanical displacement through the thickness, a sinus model that satisfies continuity conditions of transverse shear stresses and the boundary conditions on the upper and lower surfaces of the beam has been employed. In the presented model, the number of unknowns is not dependent on the number of layers. The variation of electric potential in each piezoelectric layer has been modeled using layer-wise theory. By applying the virtual work principle (VWP), a formulation has been developed for a twonodded Hermitian-2(n + 1) layer-wise nodded element for a n-layered beam. The VWP leads to a derivation that could include dynamic analysis. However, in this study only static problems have been considered. Comparison of results obtained from this formulation with available works in the literature, demonstrates efficiency of proposed model in analysis of laminated beams under mechanical and electrical loadings.