Approximate Closed-Form Solutions for the Shift Mechanics of Rubber Belt Variators

The mechanical behavior of V-belt variators during the speed ratio shift is different from the steady operation as a gross radial motion of the belt is superimposed to the circumferential motion. The theoretical analysis involves equilibrium equations similar to the steady case, but requires a re-formulation of the mass conservation condition making use of the Reynolds transport theorem. The mathematical model of the belt-pulley coupling implies the repeated numerical solution of a strongly non-linear differential system. Nevertheless, an attentive observation of the numerical diagrams suggests simple and useful closed-form approximations for the four possible working modes of any pulley, opening/closing, driver/driven, whose validity ranges over most practical cases. The present analysis focuses on the development of such simplified solutions, succeeding in an excellent matching with the numerical plots, and on the comparison of the theory with some experimental tests on a motorcycle variator, revealing a very good agreement.

The Static and Dynamic Behavior of MEMS Arches Under Electrostatic Actuation

In this paper, we investigate theoretically and experimentally the static and dynamic behaviors of electrostatically actuated clamped-clamped micromachined arches when excited by a DC load superimposed to an AC harmonic load. A Galerkin based reduced-order model is used to discretize the distributed-parameter model of the considered shallow arch. The natural frequencies of the arch are calculated for various values of DC voltages and initial rises of the arch. The forced vibration response of the arch to a combined DC and AC harmonic load is determined when excited near its fundamental natural frequency. For small DC and AC loads, a perturbation technique (the method of multiple scales) is also used. For large DC and AC, the reduced-order model equations are integrated numerically with time to get the arch dynamic response. The results show various nonlinear scenarios of transitions to snap-through and dynamic pull-in. The effect of rise is shown to have significant effect on the dynamical behavior of the MEMS arch. Experimental work is conducted to test polysilicon curved microbeam when excited by DC and AC loads. Experimental results on primary resonance and dynamic pull-in are shown and compared with the theoretical results.

Material Property Characterization of Costal Cartilage Using AFM Indentation

Costal cartilage is one of the load bearing tissues of the rib cage. Literature on the material characterization of the costal cartilage is limited. Atomic force microscopy has been extremely successful in characterizing the elastic properties of articular cartilage, but no studies have been published on costal cartilage. In this study AFM indentations on human costal cartilage were performed and compared with macro scale indentation data. Spherical beaded tips of three sizes were used for the AFM indentations. The Hertz contact model for spherical indenter was used to analyze the data and obtain the Young’s modulus. The costal cartilage was found to be almost linearly elastic till 600 nm of indentation depth. It was also found that the modulus values decreased with the distance from the junction. The modulus values from macro indentations were found to be 2-fold larger than the AFM indentation modulus.

The Wolfrom Gear Train: A Case of Highest-Complexity Related Modifications of the Tooth Meshing

The Wolfrom gear is suitable for high speed ratios with an efficiency which is not optimal, but still acceptable. The version with single-rim satellites has significant design and technological advantages. However, the determination of the most appropriate modification coefficients poses a technical problem as the modifications are now related instead of being chosen independently. The geometrical calculations of the single-rim satellites version are performed in the paper. Speed ratio, number of teeth of the satellites, pressure angles and modification coefficients are determined. Advisable values for these parameters are given. As an example a specific design problem for the replacement of a three-stage planetary reducer (consisting of 15 gears) with a Wolfrom gear train (6 gears) the following calculations were performed.

Influence of Gear Rim Deflections on Planetary Gear Set Behavior

In this study, results of an experimental and theoretical study on the influence of rim thickness of the ring gear on rim deflections and stresses, and planet load sharing of a planetary gear set are presented. Experimental study consists of measurement of ring gear deflections and strains for gear sets having various numbers of planets, different ring gear rim thicknesses as well as various carrier pin hole position errors. Root and hoop strain gauges and displacement probes are placed at various locations so that the variations due to external splines of the stationary ring gear can also be quantified. A family of quasi-static deformable-body models of the test gear planetary gear sets is developed to simulate the experiments. The predictions and the measurements are compared to assess the accuracy of the models within wide ranges of parameters. Influence of rim thickness on ring gear stresses and deflections and planet load sharing are quantified together with the interactions between the rim flexibility and the spline conditions. The results from this study confirm that the ring gear deflections and the ring gear support conditions must be included in the design process as one of the major factors.

Fuel Efficiency Strategic Plan of Medium-Duty Tactical Truck

This paper reports the planning efforts on reducing fuel consumption rate in the current fleet of medium-duty tactical truck. A strategic plan was developed through investigation of current and future technology offerings from original equipment manufacturers and aftermarket suppliers. Research efforts consisted of an initial phase where a broad range of integration candidates were collected and a secondary phase where in-depth analysis was conducted to target those to consider for inclusion in the strategic plan. Each product was evaluated on its technical merits with consideration given to the needs and strategic goals of government agencies. The strategic plan lays out the integrated technologies in the near-term including hydrogen injection and auxiliary electrification of engine cooling fan. For the mid-term timeframe, the plan involves implementing an engine stop/start system and electrifying other auxiliaries. The final step in the plan is the development and implementation of a full (strong) hybrid population.

A Novel Semi-Analytical Approach for Micro Beams Subjected to Electrostatic Loads and Residual Stress Gradients

Beam structures are widely used in MEMS sensors and actuators. MEMS micro beams are usually curled due to residual stresses and the characteristics of micro beams subjected to both residual stress gradients and electrostatic forces must be investigated for providing accuracy information for designing sensors and actuators. In this work, a novel semi-analytical formulation to address the above needs is proposed. By assuming an admissible deformation shape and utilizing energy method to determine the coefficients of the shape functions, it is possible to find the pull-in characteristics of the curled cantilevers. Detail parametric studies are subsequently performed to quantify the influence of various geometry and processing parameters on the pull-in characteristics of those micro beams. The method and results presented in this work would be very useful for related micro sensors and actuator designs.

Optimization Based Geometric Modeling of Nano/Micro Scale Ion Milling of Organic Materials

Recently, Focused Ion Beam (FIB) instruments have begun be applied to organic materials such as polymers and biological systems. This provides a novel tool for sectioning biological samples for analysis, or microfabrication with environment friendly materials. The modeling of nano/micro scale geometry accurately sculptured by FIB milling is crucial for generating the milling plan and process control, and for computer simulation for prediction and visualization of the milled geometry. However, modeling of the ion milling process on compound materials, especially for high aspect ratio feature, is still difficult due to the complexity of target material, as well as multiple physical and chemical interactions involved. In this study, a comprehensive model of ion milling with organic targets is presented to address the challenges using a simulation based approach. This platform has also been validated by milling different features on water ice in a cryogenic environment, and the simulation and experiment results show great consistency. With the proliferation of nanotechnology to biomedical and biomaterial domains, the proposed approach is expected to be a flexible tool for various applications involving novel and heterogeneous milling targets.

Comparative Analysis of Two Numerical Methods of Rollover Simulation of a Semitrailer for Hydrogen Transport

Nowadays, the use of the Finite Element Method [1] by means of simulation computer tools has made possible a substantial step forward in the field of calculation and optimization of vehicle structures. More specifically, these modern calculation tools are achieving great cost reductions corresponding to the experimental tests necessary to verify the appropriate performance of a vehicle in impact cases. On the other hand, great efforts will have to be done to develop correct numerical models for calculation. Once these numerical models have been validated with experimental tests, elimination of experimental costs compensates for these calculation efforts. A greater flexibility in decision making with respect to design and optimization alternatives will be achieved as well. The objective of this paper is to obtain an appropriate test simulation methodology for a specific vehicle and a specific impact case: There have been carried out the simulations of two different rollover test typologies in order to verify an adequate and safe behaviour of a semitrailer designed for hydrogen transport. After results of these two simulations are obtained, they will be compared in order to set which is the most restrictive and therefore the most appropriate. A lightened configuration has been also considered so as to carry out a sensibility analysis of material and thickness of some structural parts over numerical results in both test typologies in order to verify these simulations.

Nano-Scale Impact Dynamics of Ultra-Thin Bonded Layers

The paper highlights the complex issues involved in impact dynamics at nano-scale, prevalent in MEMS. The role of protective layers on the silicon substrate is investigated. It is found that the expected viscoelastic behavior of these layers is not activated due to the very short (almost instantaneous) impact times.