Applied Mechanics and Materials Vols. 479-480

Abstract: This paper presents the light rail transit system (lrts) impact on the harmonic pollution of distribution feeder. To investigate the dynamic responses of the system voltage and current, the distribution system and lrts models are set up well by using the Alternative Transients Program (ATP). The harmonic analysis of the distribution system with the lrts is executed under various operation scenarios. The 6-pulses and 12-pulses rectifier are adopted for the lrts with a direct current (dc) power supply to the trams. Furthermore, the well-designed filters have also applied to improve the harmonic distortion resulted from the lrts.

Abstract: The van-der-pol hysteretic cycle was applied to describe the hysteretic nonlinear characteristic of the strain-stress relation of a shape memory alloy (SMA). A new model with nonlinear damping of a simply supported SMA beam was proposed. The Criterions determining the stochastic chaos is obtained by the random Melnikov approach. The numerical results show the effectiveness of the theoretical analysis. Clear fractal boundaries of the system's safe basin is observed.

Abstract: A Parametric study of a passive micromixer with convergent-divergent channel walls of sinusoidal variation is conducted numerically using combined Navier-Stokes equations and convection-diffusion model for a Reynolds number range, 10 ≤ Re ≤ 70. Water and ethanol are used as working fluids for mixing analysis. Mixing performance was used to compare different configurations (layout) of the micromixer. In comparison with previously published design, which was based on Dean vortices in the sub-channels, the new configurations offered Dean vortices in the sub-channels and recirculation zones in the recesses of the channel for effective mixing. The proposed configurations are competitive in terms mixing performance and pressure loss. Finally, effect of two geometrical parameters viz. the ratio of throat-width to diameter of circular wall and the ratio of diameter of circular wall to amplitude, on mixing performance was studied over a chosen Reynolds number range.

Abstract: The effects of micro-sized through-hole drug reservoirs on several key clinical attributes of the drug eluting depot stent were investigated. Finite element models were developed to predict the mechanical integrity of a balloon-expandable stent at various stages such as manufacturing and deployment, as well as the stent radial strength and fatigue life. Results show that (1) creating drug reservoirs on a stent could impact the stent fatigue resistance to certain degrees, and (2) drug reservoirs on the stent crowns led to much greater loss in all key clinical attributes than reservoirs on other locations. Based on these findings, an optimized depot stent was proposed/manufactured and proven to be a feasible design.

Abstract: This paper presents finite-element analysis (FEA) of the magnetic field of a magnetic gear mechanism. An external type magnetic gear mechanism, which consists of two identical magnetic gears with sector-shaped permanent magnets, is introduced first. Then, the magnetostatic field distribution and transmitted torque of the magnetic gear mechanism are simulated by a commercial FEA package Ansoft/ Maxwell. Next, the effects of design parameters, including the air-gap length, the number of magnetic pole pairs, and the height of permanent magnets, on the maximum transmitted torque are discussed. The results of this work are beneficial to the design of magnetic gear mechanisms.

Abstract: A transmission hub is a speed changing mechanism which is an important device in the transmission system of bicycles. This paper presents the kinematic analysis of an 8-speed bicycle transmission hub by using the fundamental circuit method. First, a distributed-flow type planetary gear mechanism, which consists of two parallel-connected transmission units and one differential unit, and the corresponding clutch sequence table of an 8-speed transmission hub are introduced. Based on the fundamental circuits, four kinematic equations of the transmission hub are derived. Then, the speed ratio of each speed is formulated, which is a function of gear ratios of external and internal gear pairs. By submitting the numbers of gear teeth into these formulas, the value of speed ratio at each speed can be calculated. Finally, the power-flow diagrams at related speeds are presented to illustrate the power-flow paths of the transmission hub.

Abstract: This study explores the characteristics of ground vibration induced by Taiwan high-speed trains on embankments. A series of field measurement data is used for evaluating near-field vibration, far-field vibration, and vibration influence distance. Various influence factors, including train speed, ground shear wave velocity, frequency dependence, and volume of the structure, are applied for evaluation. Based on the analyses, the near-field ground vibration mainly depends on the train speed, ground shear wave velocity, and frequency dependence. The far-field vibration propagation is affected by ground shear wave velocity and frequency dependence. In general, the high frequency range has the highest attenuation coefficient and the low frequency range has the lowest. The influence distance in hard ground is the farthest, whereas the soft ground is the shortest. Finally, a specific ground vibration assessment is established using these characteristics.

Abstract: Viscoelastic damping isolator (VDI) is a new way to reduce the vibration of punch press in automobiles, motorcycles, IT, aerospace, mold and other industries. It not only reduces the vibration of large punching machine and equipment, but also decreases its maintenance costs and avoids endangering the surrounding environment. VDI is composed of partitions, damping fluid, steel springs and level adjusters. Different number of the partitions are welded on upper and lower rectangular steel plates, respectively. Steel springs are placed at the edges between the plates to support up to 150 tons of weight of the punch press. Screw level adjusters are place between lower and thick bottom plates to adjust the horizontal level of the isolator. The damping fluid is filled in the space between interlacing partitions approximate 60% of the height of the composed isolator. The impact energy produced by the presser is dissipated by shear deformation between the damping fluid and partitions. This article used 3D graphing software and finite element method (FEM) to investigate the dynamic characteristic of the damping isolator after impacted by the puncher. The normal mode analysis of the VDI is obtained. The isolator is settled within 0.3 seconds after 300,000 N shock impact and satisfies industrial specification of large punchers with loading frequency of 100 cycle/min.

Abstract: The rectangular convergent/divergent channels with one sided ribbed surface only have the inclination angles of 0.72^oand1.43^o at which the ribbed wall is manufactured with a fixed rib height ( e) =10 mm and the ratio of rib spacing (p) to height ( e) =10. The comparison shows that among the four channels (D_ho/D_hi =0.67, 0.86, 1.16, and1.49) the divergent channel of D_ho/D_hi =1.49 has the highest thermal performance at the identical mass flow rate, and the divergent channel of D_ho/D_hii =1.16 has the highest at the identical pumping power and static pressure drop.

Abstract: This paper investigates the statistical dynamic behavior on the bridge-vehicle interaction problem with randomness in material properties and moving loads. The bridge is modeled as a beam with Gaussian random elastic modulus and mass density of material with random moving forces on top. The mathematical model of the bridge-vehicle system is established based on the finite element model in which the Gaussian random processes are represented by the Karhunen-Loéve expansion. Some statistical response such as the mean value and standard deviation of the deflections of the beam are obtained and checked by Monte Carlo simulation.