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A multi-point hypoid gear mesh model based on 3-dimensional loaded tooth contact analysis is incorporated into a coupled multi-body dynamic and vibration hypoid gear model to predict more detailed dynamic behavior of each tooth pair. To validate the accuracy of the proposed model, the time-averaged mesh parameters are applied to linear time-invariant (LTI) analysis and the dynamic responses, such as dynamic mesh force, dynamic transmission error, are computed, which demonstrates good agreement with that predicted by single-point mesh model. Furthermore, a nonlinear time-varying (NLTV) dynamic analysis is performed considering the effect of backlash nonlinearity and time-varying mesh parameters, such as mesh stiffness, transmission error, mesh point and line-of-action. Simulation results show that the time history of the mesh parameters and dynamic mesh force for each pair of teeth within a full engagement cycle can be simulated.

Due to the design of lightweight, high speed driveline system, the coupled bending and torsional vibration and rotordynamics must be considered to predict vibratory responses more realistically. In the current analysis, a lumped parameter model of the propeller shaft is developed with Timoshenko beam elements, which includes the effect of rotary inertia and shear deformation. The propeller shaft model is then coupled with a hypoid gear pair representation using the component mode synthesis approach. In the proposed formulation, the gyroscopic effect of both the gear and propeller shaft is considered. The simulation results show that the interaction between gear gyroscopic effect and propeller shaft bending flexibility has considerable influence on the gear dynamic mesh responses around bending resonances, whereas the torsional modes still dominate in the overall frequency spectrum.

Modeling of elastohydrodynamic lubrication phenomena for the spiral bevel gears is performed in the present study. The damping and the friction coefficient generated from the lubricated contact area will have profound effects on the dynamics of spiral bevel gears. Thus the damping value generated from this friction model will be time varying. This makes the use of constant and empirical damping value in the dynamics of spiral bevel gears questionable. The input geometric and kinematic data required for the elastohydrodynamic lubrication (EHL) simulations are obtained using Tooth Contact Analysis. A full numerical elastohydrodynamic lubrication simulations are carried out using asymmetric integrated control volume (AICV) algorithm to compute the contact pressures. The fast Fourier transform is used to calculate the elastic deformations on the gear surfaces due to contact load.

A general time-varying nonlinear dynamic model of a hypoid gear pair for rear axle applications is proposed. The dynamic model considers time-varying mesh position, line of action, mesh stiffness, mesh damping and backlash nonlinearity. Based on the model, dynamic analysis is conducted to study the effect of mean load, mesh damping and mesh parameter variations on dynamic mesh force response and the interaction between them and backlash nonlinearity. Numerous nonlinear phenomena such as tooth impacts and jump discontinuities are revealed by computational results.

High speed, precision geared rotor systems are often plagued by excessive vibration and noise problems. The response that is primarily excited by gear transmission error is actually coupled to the large displacement rotational motion of the driveline system. Classical pure vibration model assumes that the system oscillates about its mean position without coupling to the large displacement motion. To improve on this approach and understanding of the influences of the dynamic coupling, a coupled multi-body dynamic and vibration simulation model is proposed. Even though the focus is on hypoid geared rotor system, the model is more general since hypoid and bevel gears have more complicated geometry and time and spatial-varying characteristics compared to parallel axis gears.

This paper discusses an enhanced active vibration control concept to suppress the dynamic response associated with gear mesh frequencies. In active control application, the control of dynamic gear mesh tonal response is essentially the rejection or suppression of periodical disturbance. Our active control experimental work shows that the existence of un-controlled harmonic result in the increase at these harmonics when applying direct control to the target mesh frequencies. To address this problem, the effect of the existence of un-correlated harmonic components in error signal when applying active control to suppress the target gear mesh harmonics is examined. The proposed adaptive controller that is designed specifically for tackling gear mesh frequency vibrations is based on an enhanced filtered-x least mean square algorithm (FXLMS) with frequency estimation to synthesize the required reference signal.

The instability of a viscous liquid jet surrounded by a swirling air stream subject to a 3-D disturbance is predicted by a linear stability model. The effect of flow conditions, fluid properties and nozzle geometry on the disintegration of the liquid jet are investigated by conducting a parametric study. It is observed that the relative velocity between the liquid and gas phases promotes the interfacial aerodynamic instability. The predicted range of wave numbers in which asymmetric modes have higher growth rates than the axisymmetric mode and dominate the instability agrees very well with experimental data. The density ratio significantly enhances the instability as does the axial Weber number. Liquid viscosity inhibits the disintegration process and damps higher helical modes more significantly than the axisymmetric mode. It is observed that air swirl has a stabilizing effect on the liquid jet.

Spiral bevel gear dynamics are significantly affected by the flexibilities of shafts and bearings. In this study, a new shaft-bearing model has been proposed for computing the effective support stiffness. The results are applied to the lumped parameter dynamic model of spiral bevel geared rotor system with 3-bearing straddle-mounted pinion configuration. Also, using the multi-degree of freedom lumped parameter dynamic model and quasi-static three-dimensional finite element tooth contact analysis program, the responses of two typical shaft-bearing configurations used in automotive applications, that are the 3-bearing straddle mounted pinion configuration and the 2-bearing overhung mounted pinion configuration, are compared. The comparative analysis along with a set of parametric studies highlights their different contributions to the spiral bevel gear mesh characteristics and dynamic response.

The goal of the presented research is to study the effective operational range for a centrifugal vaneless diffuser turbocharger compressor with ported shroud typically used in diesel engines. A turbocharger bench facility was designed and tested in order to define the performances of the compressor and to better understand the occurrence of instabilities in the housing. Specific emphasis was given to the low mass flow rate region of the compressor performance characteristics where instabilities occur with fluctuations that can be significantly large in the case of surge. Static pressures and dynamic pressure fluctuations were measured at the inlet, the outlet, as well as at different positions around the volute and diffuser sections of the compressor in order to assess the development and propagation of flow instabilities. The dynamic signature of the flow was measured along with the elaboration of the compressor mapping.

This paper provides several examples of silicon “micromachined” semiconductor sensors with which the authors are involved for aerospace condition monitoring. This and related work in MEMS (Micro Electro Mechanical Systems) has the potential to revolutionize condition monitoring in aerospace condition and “health monitoring” by (1) moving “smart” electronics out to the sensor chip itself and (2) combining a vast quantity and types of, not only electronic, but micromechanical sensing schemes into the silicon chip . Precisely formed cantilevers, gears, valves, microplumbing and even micro motors of the cross-section of a human hair can be fabricated on a single silicon microchip. Silicon is an excellent mechanical material with a yield strength several times that of stainless steel. Also silicon has excellent thermal properties , whereas compatible silicon dioxide (which we typically use in connection with silicon microelectronics patterning) is virtually a thermal insulator.

The High Pressure Oxidizer Turbine (HPOT) discharge temperature of the Space Shuttle Main Engine (SSME) was estimated using Radial Basis Function Neural Networks (RBFNN) during the startup transient. Estimation was performed for both nominal engine operation and during simulated input sensor failures. The K-means clustering algorithm was used on the data to determine the location of the basis function centers. The performance of the RBFNN is compared with that of a feedforward neural network trained with the Quickprop learning algorithm.

Electrically passive optical sensors have been formed using optical waveguides and micromachined-micromechanical structures on silicon substrates. We present recent results on an interferometric pressure sensor where pressure-induced strain in a micromachined diaphragm alters the path length of an optical channel waveguide ring resonator. Pressure is detected as a change in the resonant condition of the ring and found to vary linearly over a range of -100 to 400 kPa with a sensitivity of 0.0094 rad/kPa. Problems with attaching this sensor for testing will be discussed. Our second device is an intensity-type accelerometer utilizing a micromachined cantilever beam. Light transmission across a gap between two channel waveguides, one located on a beam bent by acceleration and another which remains fixed, is measured optically. We show preliminary measurements of the coupling between two closely spaced waveguide sections which agree with overlap integral calculations.

In highly reverberant enclosures, the identification of noise sources is a difficult and time consuming task. One effective approach is the Inverse Frequency Response Function (IFRF) method. This technique uses the inverse of an acoustic FRF matrix, that when multiplied by operating pressure response data reveals the noise source locations. Under highly reverberant conditions the deployment of a sound absorbing body is especially useful in reducing the effects of resonant modes that obscure important information in the FRFs. Without the absorption, the IFRF method becomes practically difficult to perform in these environments due to poor conditioning of the FRF matrix. This study investigates the feasibility of using Boundary Element and Finite Element Methods to establish the frequency response functions between selected panel points and microphones in the array.

As the drive to make automobiles more noise and vibration free continues, it has become necessary to analyze transient events as well as periodic and random phenomena. Averaging of transient events requires a repeatable event as well as an available trigger event. Knowing the exact event time, the data can be post-processed by re-sampling the time scale to capture the recorded event at the proper instant in time to allow averaging. Accurately obtaining the event time is difficult given the sampling restrictions of current data acquisition hardware. This paper discusses the ideal hardware needed to perform this type of analysis, and provides analytical examples showing the transient averaging improvements using time scale re-sampling. These improvements are applied to noise source identification of a single transient event using an arrayed microphone technique. With this technique, the averaging is performed using time delays between potential sources and microphones in the array.

This study describes the application of novel chemistry methods for the fabrication of robust nanostructured TiO2 photocatalytic films and membranes for the development of efficient wastewater treatment and reuse systems for advanced life support in space missions. These films and membranes perform several functions, including water purification (i.e., destruction of organic contaminants, filtration) and water disinfection. Nanocrystalline TiO2 thin films and membranes, and the corresponding particles have been synthesized from a titania sol modified with nonionic long chain surfactants used as pore directing agents. The prepared materials were characterized to reveal material crystal structure, morphology, nanostructure, elemental composition, and other characteristics, and evaluated for their adsorptive properties and photocatalytic activity to destroy organic contaminants in water.

Vehicle electronics and sensor systems have become indispensable parts in providing safety, comfort, personal communication mobility and many other advanced functions in today's vehicles. As a result, reliability requirements for these critical parts have become extremely important. To meet these requirements, more advanced technologies and tools for degradation monitoring and failure prevention are needed. Currently, the development of diagnostics and prognostics techniques, which employ accurate degradation quantification by appropriate sensor selection, location decision, and feature selection and feature fusion, still remains a vital and unsolved issue. This paper addresses several realistic concerns of failure prevention in vehicle electronics and sensor systems. A unified monitoring and prognostics approach that prevents failures by analyzing degradation features, driven by physics-of-failure, is suggested as a general framework to overcome the unsolved challenge.

A new multi-level substructuring approach is proposed to predict the NVH response of driveline systems for the purpose of analyzing rear axle gear whine concern. The fundamental approach is rooted in the spectral-based compliance coupling theory for combining the dynamics of two adjacent subsystems. This proposed scheme employs test-based frequency response functions of individual subsystems, including gear pairs, propshaft, control arms and axle tube, in free-free state as sequential building blocks to synthesize the complete system NVH response. Using an existing driveline design, the salient features of this substructuring approach is demonstrated. Specifically, the synthesized results for the pinion-propshaft assembly and complete vehicle system are presented. The predictions are seen to be in excellent agreement with the experimental data from direct vehicle measurements.

Cycloid drives are widely used in the in-wheel motor for electric vehicles due to the advantages of large ratio, compact size and light weight. To improve the transmission efficiency and the load capability and reduce the manufacturing cost, a novel cycloid drive with non-pin design for the application in the in-wheel motor is proposed. Firstly, the generation of the gear pair is presented based on the gearing of theory. Secondly, the meshing characteristics, such as the contact zones, curvature difference, contact ratio and sliding coefficients are derived for performance evaluation. Then, the loaded tooth contact analysis (LTCA) is performed by establishing a mathematical model based on the Hertz contact theory to calculate the contact stress and deformation.

Turbochargers are commonly used in automotive engines to increase the internal combustion engine performance during off design operation conditions. When used, a most wide operation range for the turbocharger is desired, which is limited on the compressor side by the choke condition and the surge phenomenon. The ported shroud technology is used to extend the operable working range of the compressor, which permits flow disturbances that block the blade passage to escape and stream back through the shroud cavity to the compressor inlet. The impact of this technology on a speed-line at near optimal operation condition and near surge operation condition is investigated. A numerical study investigating the flow-field in a centrifugal compressor of an automotive turbocharger has been performed using Large Eddy Simulation. The wheel rotation is handled by the numerically expensive sliding mesh technique. In this analysis, the full compressor geometry (360 deg) is considered.

A series of novel metal-oxide (TiO2, TiO2-SiO2)-supported Mn, Fe, Co, V, Cu and Ce catalysts were prepared by incipient wetness technique and investigated for the low-temperature selective catalytic reduction (SCR) of NOx with ammonia at industrial relevantly conditions. Among all the prepared catalysts, Cu/TiO2 showed superior de-NOx performance in the temperature range of 150-200 °C followed by Mn/TiO2 in the temperature range of 200-250 °C. The Ce/TiO2 catalyst exhibited a broad temperature window with notable de-NOx performance in the temperature regime of 250-350 °C. The phyico-chemical characterization results revealed that the activity enhancement was correlated with the properties of the support material. All the anatasetitania-supported catalysts (M/TiO2 (Hombikat)) demonstrated significantly high de-NOx performance above 150 °C.