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Automobile brake squeal has been experimentally studied in many ways over the past 65 years. A large body of published research and a substantial amount of unpublished work have attempted to experimentally define the variables involved with and describe the system dynamics initiating the friction-induced self-excited vibration. Much of this work has centered on pin on disk type test rigs used to characterize the contact mechanics and/or friction laws without considering the brake system influence. This paper describes a dynamometer designed and constructed to study brake squeal on a system level.

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.

A proposed multi-coordinate spectral-based inverse substructuring approach is applied experimentally to examine the vibration transmissibility through chassis mounts. In this formulation, the vehicle system is partitioned into two substructures. One substructure comprises of the chassis and suspension, while the second one is the body structure and other attached components. The approach yields the free substructure dynamic characteristics that are extracted from the measured coupled system response spectra. The resultant free substructure transfer functions are verified by comparison of the re-synthesized results to the actual vehicle system measurements. A real life vehicle setup is utilized to demonstrate the salient features and capabilities of this approach, which includes the ability to compute the main structure-borne paths, dynamic interactions between the chassis and body, and interior noise and vibration response.

A multi-coordinate FRF-based inverse substructuring approach is proposed to partition a vehicle system into two or more substructures, which are coupled at discrete interface points. The joint and free substructure dynamic characteristics are then extracted from the coupled system response spectra. Depending on the actual form of the structural coupling terms, three forms of the coupling matrix are assumed here. The most general one constitutes the non-diagonal form, and the other two simpler cases are the block-diagonal and purely diagonal representations that can be used to simplify testing process and overcome computational problems. The paper is focused on the investigation of the durability of these three formulations when the input FRFs are noise contaminated. A finite element model of a simplified vehicle system is used as the case study.

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.

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.

Demand for accurate and reliable gamma dosimetry in a radiation environment and the unsatisfactory performance of the existing devices has given rise to the need for a better gamma measurement system, capable of operating in a high dose rate environment and withstanding a high total dose. The concept of a new gamma dose measurement device based on the principle of photoconductivity has the potential of filling this void. Preliminary experiments and analyses indicated that the selected dosimeter materials exhibit photoconductivity in a useful range, responsive to changes in gamma dose rate. The initial Pyrex glass dosimeter appeared to suffer radiation damage at the relatively high dose rates employed (up to 0.116 Mega rads/hour). Quartz is now being studied as an alternative material.

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.

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.

The prediction and control of gear vibration and noise has become very important in the design of a quiet, high-quality gearbox systems. The vibratory energy of the gear pair caused by transmission error excitation is transmitted structurally through shaft-bearing-housing assembly and radiates off from exterior housing surface. Most of the previous studies ignore the contribution of components flexibility to the transmission error (TE) and system dynamic responses. In this study, a system level model of axle system with hypoid gear pair is developed, aiming at investigating the effect of the elasticity of the shafts, bearings and housing on TE as well as the contribution of flexible bearings on the dynamic responses. The load distribution results and gear transmission errors are calculated and compared between different assumptions on the boundary conditions.

Actuator and roller screw mechanism are key components of electromechanical brake (EMB) system in automotive and aerospace industry. The inverted planetary roller screw mechanism (IPRSM) is particularly competitive due to its high load-carrying capacity and small assembly size. For such systems, friction characteristic and friction torque generated from rolling/sliding contacts can be an important factor that affects the dynamic performance as well as vibration behavior. This paper investigates the modeling and simulation of the EMB system in early design stage with special attention to friction torque modelling of IPRSM. Firstly, a step-by-step system model development is established, which includes the controller, servo motor, planetary gear train and roller screw mechanism to describe the dynamic behavior of the EMB system.

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.

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.

Test sensors are evaluated for noise path analysis applications. Newly developed ICP™ piezo-electric strain gages are used with accelerometers and microphones in a conventional noise path analysis test on the front body/suspension attachment points of a vehicle. In a less conventional application, a steering knuckle is converted into a 6-DOF force transducer using an array of strain gages and using an array of 3-DOF load cells. The two sensor arrays are both calibrated with a 6-DOF load cell. The result is an estimate of the three translation force and three moment operating inputs entering the steering knuckle from the wheel.

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.

The noise and vibration response of hypoid or bevel geared rotor system, primarily excited by transmission error (TE), and mesh vector and stiffness variations, can be affected significantly by the coupling between the driveline rotor dynamics and gear vibratory response. This is because of the inherent design comprising of non-parallel rotational axes and time-varying as well as spatial-varying gear mesh characteristics. One of the important factors of the driveline system dynamics is the rotor gyroscopic effect that has not been studied extensively in traditional gear dynamics. To address this gap in the literature, this paper attempts to examine the influence of incorporating gyroscopic terms in the hypoid gear dynamic simulation. A multi-degrees-of-freedom, multi-body dynamic model is used as a generalized representation of a hypoid geared rotor system.

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.

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.

Nonlinear interaction between time-varying hypoid gear mesh and bearing support is investigated in this study. Mesh parameters are time-varying due to complex tooth profile of hypoid gear. Bearing stiffness is formulated based on real geometry and instantaneous orbital position of rolling elements. Linear model is firstly analyzed to study the modal frequency and mode shape variations under different stiffness ratio between gear mesh and bearing support. Then, nonlinear analysis is conducted to compare the differences between linear and nonlinear dynamic response based on specific nonlinear conditions of geared rotor system. It is found that the coupling between hypoid gear mesh and bearing support can be either strong or weak depending on the ratio between mesh stiffness along line-of-action (LOA) and bearing stiffness in radial direction. Parametric studies indicate that dynamic mesh force is sensitive to bearing clearance for certain stiffness ratio.

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.