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Viewing 1 to 27 of 27
2009-05-19
Journal Article
2009-01-2034
Jae-Yeol Park, Rajendra Singh
Most of the prior work on active mounting systems has been conducted in the context of a single degree-of-freedom even though the vehicle powertrain is a six degree-of-freedom isolation system. We seek to overcome this deficiency by proposing a new six degree-of-freedom analytical model of the powertrain system with a combination of active and passive mounts. All stiffness and damping elements contain spectrally-varying properties and we examine powertrain motions when excited by an oscillating torque. Two methods are developed that describe the mount elements via a transfer function (in Laplace domain). New analytical formulations are verified by comparing the frequency responses with numerical results obtained by the direct inversion method (based on Voigt type mount model). Eigensolutions of a spectrally varying mounting system are also predicted by new models.
2005-05-16
Technical Paper
2005-01-2456
Chengwu Duan, Rajendra Singh
The chief objective of this paper is to study the non-linear behavior of torque converter clutch within the context of an automotive drivetrain. An analytical procedure to determine the pure stick to stick-slip motions is developed based on the linear system analysis. This procedure can efficiently and accurately identify the frequency ranges where linear or non-linear studies are needed. Stick-slip behavior can be clearly observed as a result of the engine torque irregularity and nonlinear friction characteristics. In particular, the effect of the friction disc inertia is studied. Both analytical and numerical results show that this inertia significantly affects the system dynamics. Our predictions compare well with prior measurements on a passive vibration absorber experiment.
2005-05-16
Technical Paper
2005-01-2292
Ashley R. Crowther, Nong Zhang, Rajendra Singh
A reduced model is developed for transient analysis of gear rattle in an automatic transmission (AT) powertrain. Linear modal analysis for the reduced order model compares well with a detailed model that includes planetary gear dynamics. Clearance type lash functions are used for the reduced geared coordinates of the automatic transmission and final drive. Impacts within the gear pairs are affected by the engine surging, shaft stiffness, component inertias, engine harmonics, drag torques, braking, viscous damping and vehicle load. The occurrence of these impacts, or clunk, from shuffle and axle oscillations is demonstrated under typical driving conditions.
2005-05-16
Technical Paper
2005-01-2338
Seungbo Kim, Akira Inoue, Rajendra Singh
This article examines the structure-borne noise transfer path measures by using a laboratory experiment with simulated engine and passenger compartments. It is excited by an emulated powertrain unit that is mounted in the engine room through three hard mounts. Indirect estimation methods for dynamic interfacial forces are first compared with direct measurements over the mid frequency regime. Two alternate path analysis issues, with focus on partial pressures in the receiver room, are then examined. This experimental study clearly demonstrates the strengths and limitations of path rank ordering schemes and analysis methods though only the translational motions are considered.
2005-05-16
Technical Paper
2005-01-2411
Song He, Rajendra Singh
New procedures are proposed to estimate the amplitude-sensitive parameters of hydraulic engine mounts that typically exhibit many nonlinearities. The estimation is based on the premise that the analyst has access to limited dynamic stiffness test data (say up to 50 Hz), and the detailed laboratory work required for the nonlinear model development would be minimized. By using an analogous mechanical model, a 3rd/2nd type transfer function is suggested to curve-fit the empirical dynamic stiffness data. Key parameters (such as the inertia-augmented fluid damping and decoupler gap length) are approximated and the effects of some system nonlinearities (such as the vacuum-induced asymmetric chamber compliance) are quantified, leading to a quasi-linear model. For the sake of illustration, transient predictions for a free decoupler mount are made; simulations match well with measurements. Main simplifications and limitations of the method are briefly discussed.
2005-05-16
Technical Paper
2005-01-2410
Song He, Rajendra Singh
The major objectives of this study are to identify the source(s) of high frequency resonance(s), suggest a method to effectively estimate mount parameters and propose both linear and nonlinear models capable of predicting the high frequency characteristics. First, a lumped parameter linear model is derived and the resonances controlled by decoupler, fluid column and rubber element are examined. By using a simplified mechanical model, typical parameters are estimated from measured dynamic stiffness data. Estimations correlate well with experiments and provide quantitative evaluation of the physical parameters, some of which (such as the decoupler damping) are otherwise difficult to measure by using conventional experimental techniques. A nonlinear time domain model for a free decoupler mount is proposed to predict both the inertia track and decoupler resonances. Both nonlinear and linear models match well with high frequency measurements.
2013-05-13
Journal Article
2013-01-1924
Tan Chai, Rajendra Singh, Jason Dreyer
Fluid filled bushings are commonly used in vehicle suspension and sub-frame systems due to their spectrally-varying and amplitude-dependent properties. Since the literature on this topic is sparse, a controlled laboratory prototype bushing is first designed, constructed, and instrumented. This device provides different internal combination of long and short flow passages and flow restriction elements. Experiments with sinusoidal displacement excitations are conducted on the prototype, and dynamic stiffness spectra along with fluid chamber pressure responses are measured. The frequency-dependent properties of several commonly seen hydraulic bushing designs are experimentally studied and compared under two excitation amplitudes. Further, new linear time-invariant models with one long and one short flow passages (in parallel or series) are proposed along with the limiting cases.
1997-05-20
Technical Paper
971936
Thomas J. Royston, Rajendra Singh
Decoupler nonlinearities of the automotive hydraulic engine mount affect its isolation performance and the transmission of structure-borne noise. The kinematic gap nonlinearity of the decoupler is examined in considerable detail in the context of the quarter car model. It is shown that while modeling it with a “softened” nonlinear expression may only moderately affect predicted system behavior at the excitation frequency, it can significantly after it at higher harmonics, changing the predicted level of structure-borne noise transmission. Studies of multi-harmonic motion and vibratory power transmission under sinusoidal and composite excitation conditions confirm that, in fact, use of a decoupler with a “softened” nonlinearity improves performance.
1993-10-01
Technical Paper
932897
Gun Kim, Rajendra Singh
Performance characteristics of passive, active, and broadband adaptive engine mounts are compared over a wide frequency range up to 250 Hz in the context of a quarter-vehicle heave model. The optimal damping coefficient of a rubber-metal mount is determined using random vibration theory. The small-scale active mount employs proportional-plus-integral control based on linear optimal control theory. The new adaptive hydraulic mount system implements an on-off damping control mode by using engine intake-manifold vacuum and a microprocessor-based solenoid valve controller. Through analytical methods, it is observed that this adaptive mount provides most desirable dynamic performance with regard to the engine-bounce control, shock absorption and vibration isolation performance requirements. Although technical prospects of the proposed adaptive system appear promising, in-situ performance needs to be evaluated.
1995-05-01
Technical Paper
951316
Chandramouli Padmanabhan, Todd E. Rook, Rajendra Singh
The sources of gear rattle in automotive transmission and other components are clearance non-linearities, which include backlashes, multi-valued springs, hysteresis, etc. Periodic vibro-impacts are generated because of the single sided or double sided impacts. It is obviously desirable to develop an appropriate computer simulation model which can aid in the control of transient noise and vibration signatures. Such models can also be used to design experiments and to interpret measured data. Several approaches have been attempted in the past, but most common is the digital simulation of the governing differential equations describing the non-linear, torsional dynamics of the drivetrain. Some progress has been made in understanding the basic rattle phenomenon and in developing suitable mathematical models. This article intends to be a status report on the mathematical or computer models including pre- and post-processing considerations.
1995-05-01
Technical Paper
951297
Thomas J. Royston, Rajendra Singh
A new semi-analytical framework for the study of passive or active engine mounting systems is presented. It recognizes that most practical problems incorporate a nonlinear mount or isolation element and the resulting physical system, consisting of the engine, mount and flexible base, involves many degrees of freedom. Unlike linear systems, sinusoidal excitation produces a periodic response, including super- and sub- harmonics. Two example case systems are employed to illustrate key concepts of the framework. The first numerical example case involves a passive hydraulic engine mount with an inertia track. The second example case is a novel experimental system that has been developed to study active and passive, nonlinear mounting problems. New analytical and experimental results are presented and various nonlinear phenomena are considered. The impact of nonlinearity on vibratory power transmission and active control is also investigated.
1995-05-01
Technical Paper
951243
Rajendra Singh, Shih-Wei Kung, Ayaz Sheikh, Michael Mitchell, Uma Nandi, Michael Ransdell
Many discrete tonal type noise and vibration problems in automotive systems and other physical structures require passive multi-layer visco-elastic damping treatments in mid to high frequency regimes. To address such issues, experimental modal analysis and dynamic finite element methods are suggested as suitable tools. Results are presented in terms of several test structures (four thin elastic beams, a thick elastic plate and an automotive brake pad) with free-free boundary conditions. Composite modal loss factors are measured and predicted for two different damping insulators consisting of adhesive, steel and coating combinations. Special attention is paid to the elastic deformation modes of test structures and spectral scaling of material properties for the finite element models.
2003-05-05
Technical Paper
2003-01-1477
Seungbo Kim, Rajendra Singh
A vibration isolator or mount is often modeled by the Voigt model describing uni-axial (longitudinal) motion with frequency-invariant parameters. However, wave effects due to the mass distribution within the isolator are observed as the frequency is increased. Further, flexural stiffness components play an important role, leading to off-axis and coupling effects. Thus, the simplified mount models could lead to erroneous predictions of the dynamic behavior of an overall system such as automotive powertrain or chassis mounting systems. This article compares various approximate isolator models using a multi-dimensional mobility model that is based on the continuous system theory. Harmonic force and moment excitations are separately applied to a rigid body source to investigate the multi-dimensional vibratory behavior. Analysis is however limited to a linear time-invariant system and the mobility synthesis method is utilized to predict the frequency domain behavior.
2003-05-05
Technical Paper
2003-01-1717
Pavak Mehta, Rajendra Singh
This paper examines the natural frequencies, mode shapes and modal damping ratios of a specially designed laboratory fixture with integral, welded or glued joints. The influence of these alternate joints on the dynamic properties of an assembly is demonstrated, using experimental, computational and analytical methods. Dimensions of a typical welded joint configuration are varied to study their effects on the modal properties of an assembly. Predictions are successfully compared with experimental modal data. This study should help in selecting the welded joint configuration to meet strength, durability or dynamic design criteria.
2003-05-05
Technical Paper
2003-01-1710
Pavak Mehta, Rajendra Singh
Accurate quantification of welded or adhesive joints in automotive chassis structures is necessary before reliable models can be developed. Such joints undergo shear and rotational deformations, which must be characterized via diagonal stiffness elements and cross-stiffness terms in order to describe static and dynamic problems. In this paper, a frequency domain decomposition technique is employed to extract static stiffness and viscous damping matrices of dimension 2 via analytical, computational or experimental models. Methods are applied to a laboratory fixture and alternate joints are compared.
2007-05-15
Technical Paper
2007-01-2418
Jae-Yeol Park, Rajendra Singh
Several mounting system design concepts have been conceptually used to decouple the engine roll mode though limited success is observed in practice. One shortcoming of the existing theories is that they ignore damping in their formulations. To overcome this deficiency, we re-formulate the problem for a non-proportionally damped, linear system while recognizing that significant damping may be possible with passive (such as hydraulic), adaptive or active mounts. Only rigid body modes of power train are considered and chassis is assumed to be rigid. Complex mode method is employed and the torque roll axis (TRA) paradigms are re-examined in terms of mount rate ratios, mount locations and orientation angles. We will show that true TRA decoupling is not possible with non-proportional damping though it is theoretically achieved for a proportionally damped system.
2007-05-15
Technical Paper
2007-01-2233
Jaspreet S. Gurm, Wan Joe Chen, Amir Keyvanmanesh, Takeshi Abe, Ashley R. Crowther, Rajendra Singh
A laboratory experiment is designed to examine the clunk phenomenon. A static torque is applied to a driveline system via the mass of an overhanging torsion bar and electromagnet. Then an applied load may be varied via attached mass and released to simulate the step down (tip-out) response of the system. Shaft torques and torsional and translational accelerations are recorded at pre-defined locations. The static torque closes up the driveline clearances in the pinion/ring (crown wheel) mesh. With release of the applied load the driveline undergoes transient vibration. Further, the ratio of preload to static load is adjusted to lead to either no-impact or impact events. Test A provides a ‘linear’ result where the contact stiffness does not pass into clearance. This test is used for confirming transient response and studying friction and damping. Test B is for mass release with sufficient applied torque to pass into clearance, allowing the study of the clunk.
2007-05-15
Technical Paper
2007-01-2179
Akira Inoue, Rajendra Singh
Previously we had found significant errors in the interfacial force results for a source-path-receiver system where only translational motions were measured. This paper examines the sources of those errors by using computational finite and boundary element models. The example case consists of a source structure (with few modes), a receiver (with many modes) and three steel rod paths. We first formulate indirect, yet exact, methods for estimating interfacial forces, by assuming that six-dimensional motions at any location are available though we focus on only the driving points. One- and three-dimensional sub-sets of the proposed formulation are compared with the six-dimensional theory in terms of interfacial force and partial sound pressure spectra.
2007-05-15
Technical Paper
2007-01-2365
Song He, Rajendra Singh
Competing linear, quasi-linear and non-linear hydraulic mount formulations of fixed and free decoupler types are comparatively evaluated for transient responses. First, features of the realistic excitation conditions are addressed. For instance, the mean load itself may vary with time, and several sinusoidal or transient excitations may be simultaneously present. Second, a multi-staged top chamber compliance model is proposed to capture asymmetric transient responses given step-up (-down) excitations. Third, implicit excitations introduced by the decoupler switching mechanism are identified at the odd harmonics of the explicit excitation frequency. Fourth, discontinuous model of bottom chamber compliance is proposed depending on the operating point(s) and/or dynamic loading. Some of the discrepancies observed between prior models and measurements can be explained using new models.
2007-05-15
Technical Paper
2007-01-2367
Song He, Rajendra Singh
This paper comparatively evaluates measurement-based quasi-linear and true non-linear (mechanical and fluid type) models of hydraulic engine mounts and examines their dynamic effects within the context of a simplified half-vehicle system. A non-linear approximate model is also developed to provide improved insight into the decoupling effects. The proposed model is validated by comparing predictions with those from a “true” non-linear fluid model. When embedded into the vehicle system, hydraulic mount efficiently provides high amplitude-sensitive damping and tunes the engine bounce mode. Proposed model concepts could be effectively utilized to examine linear and non-linear vehicle responses in both time and frequency domains.
2015-06-15
Journal Article
2015-01-2179
Laihang Li, Rajendra Singh
Abstract The transient vibration phenomenon in a vehicle powertrain system during the start-up (or shut-down) process is studied with focus on the development and experimental validation of the nonlinear powertrain models. First, a new nonlinear four-degree-of-freedom torsional powertrain model for this transient event, under instantaneous flywheel motion input, is developed and then validated with a vehicle start-up experiment. Second, the interactions between the clutch damper and the transmission transients are established via transient metrics. Third, a single-degree-of-freedom nonlinear model, focusing on the multi-staged clutch damper, is developed and its utility is then verified.
2015-06-15
Journal Article
2015-01-2180
Almahdi Saleh, Michael Krak, Jason Dreyer, Rajendra Singh
Abstract This study examines clutch-damper subsystem dynamics under transient excitation and validates predictions using a new laboratory experiment (which is the subject of a companion paper). The proposed models include multi-staged stiffness and hysteresis elements as well as spline nonlinearities. Several example cases such as two high (or low) hysteresis clutches in series with a pre-damper are considered. First, detailed multi-degree of freedom nonlinear models are constructed, and their time domain predictions are validated by analogous measurements. Second, key damping sources that affect transient events are identified and appropriate models or parameters are selected or justified. Finally, torque impulses are evaluated using metrics, and their effects on driveline dynamics are quantified. Dynamic interactions between clutch-damper and spline backlash nonlinearities are briefly discussed.
1999-05-17
Technical Paper
1999-01-1677
Shih-Wei Kung, Rajendra Singh
Damping material for automotive structures is often quantified in terms of composite loss factor or damping ratio by using ASTM/SAE beam or modal tests. Simplified expressions have also been used to estimate certain material properties. However, none of these tests provide any information on the properties of viscoelastic core material such as rubber or adhesive in practical structures. To overcome this deficiency, a refined estimation procedure is proposed. A new sandwich beam model has been developed which describes all layers of an arbitrarily applied damping patch. By using both analytical predictions and modal experiments on a cantilever beam, spectrally-varying loss factor and shear modulus of the unknown core are determined.
2003-05-05
Technical Paper
2003-01-1620
Hyeongill Lee, Rajendra Singh
Modal sound radiation of a brake rotor is expressed in terms of analytical solutions of a generic thick annular disk having similar geometric dimensions. Finite element method is used to determine structural modes and response. Vibro-acoustic responses such as surface velocities and radiated sound pressures due to a multi-modal excitation are calculated from synthesized structural modes and modal acoustic radiation of the rotor using the modal expansion technique. In addition, acoustic power and radiation efficiency spectra corresponding to a specific force excitation are obtained from the sound pressure data. Accuracy of the new semi-analytical method has been confirmed by purely numerical analyses based on finite element and boundary element models. Our method should lead to an improved understanding of the sound radiation from a brake rotor and strategies to minimize squeal noise radiation could be formulated.
2003-05-05
Technical Paper
2003-01-1489
Martin G. Foulkes, James P. De Clerck, Rajendra Singh
A study has been conducted to determine the noise and vibration effect of inserting a cardboard liner into a thin, circular cross-sectioned, cylindrical shell. The relevance of such a study is to improve the understanding of the effects when a cardboard liner is used in a propeller shaft for noise and vibration control purposes. It is found from the study that the liner adds significant modal stiffness, while an increase in modal mass is also observed for a particular shell type of mode. Further, the study has shown that the additional modal damping provided by the liner is not appropriately modeled by Coulomb friction damping, a damping model often intuitively associated with cardboard materials. Rather, the damping is best modeled as proportional viscous damping.
2001-04-30
Technical Paper
2001-01-1463
Jun Y. Kim, Rajendra Singh
Many automotive components and sub-systems require viscoelastic damping treatments to control noise and vibration characteristics. To aid the dynamic design process, new approaches are needed for modeling of partial damping treatments and characterization of the overall dynamic behavior. The analytical component of the design process is illustrated via the transmission casing cover, along with supporting experiments. First, the vibration response of production casing plates is examined, with and without the constrained layer treatment. A modified flat plate is employed along with a generic housing that provides the realistic boundary conditions for subsequent work. A simplified analytical damping model for constrained viscoelastic layer damping is suggested based on assumed modal functions. Using the analytical model, design guidelines in terms of optimal patch shapes and locations are suggested.
2001-04-30
Technical Paper
2001-01-1452
Seungbo Kim, Rajendra Singh
In many vibration isolation problems, translational motion has been regarded as a major contributor to the energy transmitted from a source to a receiver. However, the rotational components of isolation paths must be incorporated as the frequency range of interest increases. This article focuses on the flexural motion of an elastomeric isolator but the longitudinal motion is also considered. In this study, the isolator is modeled using the Timoshenko beam theory (flexural motion) and the wave equation (longitudinal motion), and linear, time-invariant system assumption is made throughout this study. Two different frequency response characteristics of an elastomeric isolator are predicted by the Timoshenko beam theory and are compared with its subsets. A rigid body is employed for the source and the receiver is modeled using two alternate formulations: an infinite beam and then a finite beam. Power transmission efficiency concept is employed to quantify the isolation achieved.
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