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Hydraulic Engine Mount (HEM) is now widely used as a highly effective vibration isolator in automotive powertrain. A lumped parameter model is a traditional model for modeling the dynamic characteristics of HEM, in which the system parameters are usually obtained by experiments. In this paper, Computational Fluid Dynamics (CFD) method and nonlinear Finite Element Analysis (FEA) are used to determine the system parameters. A Fluid Structure Interaction (FSI) FEA technique is used to estimate the parameters of volumetric compliances, equivalent piston area, inertia and resistance of the fluid in the inertia track and decoupler of a HEM. A nonlinear FEA method is applied to determine the dynamic stiffness of rubber spring of the HEM. The system parameters predicated by FEA are compared favorably with experimental data and/or analytical solutions.

Quality control of NVH performance of Body and Chassis systems is a challenging task. In-line NVH monitoring is part of a practical solution in many cases. The associated technology is maturing, flexible, and economical. Benefits extend beyond a “safety net” sorting function. This paper presents a general overview of the current state of commercially available technology, and presents an example application of an in-line NVH monitoring system for a window regulator assembly line. A couple specific issues and resulting NVH monitoring techniques are discussed - the use of an enveloping function to highlight a cable interference issue, and the use of a microphone to highlight a motor noise issue in a relatively noisy environment.

One dominant “wind noise” generating mechanism in road vehicles is the interaction between turbulent flows and flexible structures which include side glass windows. In this study, the effects of seal mechanical properties on the sound generated from flow-induced vibration of side glass windows were investigated. The primary goal was to assess the influence of seal support properties on the noise generated from a plate. Two different models to calculate the optimal support stiffness of the seal that minimizes the velocity response are presented. The results show that both the velocity response and the sound radiation are strongly influenced by dissipation of vibration energy at the edges. It is demonstrate that support tuning can yield significant noise and vibration reduction.

An L18 Taguchi-style Design of Experiments (DOE) with eight factors was used to optimize exterior mirrors for wind noise and drag. Eighteen mirror properties were constructed and tested on a full size greenhouse buck at the Lockheed low-speed wind tunnel in Marietta, GA. Buck interior sound data and drag measurements were taken at 80 MPH wind speed (0° yaw angle). Key wind noise parameters were the fore/aft length of mirror housing and the plan view angle of the mirror housing's inboard surface. Key drag parameters were the fore/aft length of the mirror housing, the cross-section shape of the mirror pedestal, and the angle of the pedestal (relative to the wind).

Sound transmission through door and window sealing systems is one important contributor to vehicle interior noise. The noise generation mechanism involves the vibration of the seal due to the unsteady wall pressures associated with the turbulent flow over the vehicle. For bulb seals, sound transmission through the seal is governed by the resonance of the seal membranes and the air cavity within the bulb (the so-called mass-air-mass resonance). The objective of this study was to develop a finite element (FE) model to predict the sound transmission loss of elastomeric bulb seals. The model was then exercized to perform a parametric study of the influence of seveal seal design parameters. The results suggest that the sound transmission loss increases as the membrane thicknesses and/or the separation distance between the two seal walls are increased. The addition of additional internal “webs” was found to have adverse effects on the sound barrier performance.

Computational fluid dynamics (CFD) simulations of the transient flow-field around a generic side view mirror shape are presented that provide insight into the wind noise generated by the mirror. The generic mirror shape consists of half a cylinder, 0.2 m in diameter and length, topped with a quarter of a sphere of the same diameter. The transient flow past the generic side view mirror is simulated using the commercial CFD code Fluent with the LES turbulence model. A flow velocity of 200 km/hr is considered which correspond to a Reynolds number of 7 × 105. Detailed velocity vectors and contour plots of the time-varying velocity and pressure fields are presented along cut-planes in the flow-field. Mean and transient pressure are also monitored at several points in the flow field and compared to corresponding experimentally data published in literature. The results are also compared with predictions made using the Ffowcs-Williams-Hawkins acoustic analogy.

This paper reviews the aero-vibro-acoustic theory required to predict interior wind noise in an automobile passenger cabin. It describes how the exterior flow field needs to be defined as an input source to a statistical energy analysis (SEA) model of the body structural acoustics, with particular emphasis on separation of different wavenumber components. The paper then presents and evaluates the most recent work with unsteady computational fluid dynamics (CFD), as means to provide the required inputs to the SEA model. Comparison of predictions with test data is provided to illustrate progress to date and continuing development directions.

The reduction of aerodynamic noise sources is today an important topic in automotive industry. In order to localize the different sources on the arm and blade, a 48 microphones acoustic antenna coupled with a software based on the beam-forming imaging method has been used. Obtained results are validated inside the car on track. Aerodynamic numerical simulations are compared to aerodynamic measurements. The turbulent kinetic energy distribution obtained from the simulations is then compared with measured sound sources localization maps: the results are presented and commented for two wiper configurations.

Valve covers are a primary source of radiated engine noise. In this paper, we discuss an analytical approach that captures the complicated nonlinear response of the cam cover gaskets and grommets without the need for a prohibitively large finite-element model of the cam cover system. We utilize a detailed local analysis of the gasket and grommet components and abstract their isolation characteristics for later use in a global NVH (Noise-Vibration-Harshness) system analysis.

Driveline torsional vibration in vehicles equipped with an automatic gearbox can lead to increased fuel consumption. At low rpm the torque converter of the automatic gearbox is active. The earlier the torque converter can be disengaged and bypassed by a lock-up clutch, the better the efficiency of the engine. Torsional vibrations in the drivetrain could prevent this early locking of the torque convertor and thus lead to a higher fuel consumption. Furthermore, these torsional vibrations can also lead to lower driver comfort. In order to improve the efficiency and the passenger comfort, a hybrid approach has been developed to predict the torsional vibrations of a full vehicle during a run-up manoeuvre on a chassis dyno, including transient effects. The hybrid approach is based on multi body modeling of the full car in LMS DADS, taking into account the flexibility of all major components of the powertrain.

Customer feedback indicated that there was a difference in noise levels and frequency content between nominally identical diesel engines manufactured in two different plants. A test program was created to determine whether this perceived difference was real. This program opened the opportunity to investigate several levels of variability in SAE J-1074 noise measurements. From the data, estimates of confidence intervals were developed to predict true mean noise levels in the presence of back-to-back, install-test-remove, and sample-to-sample test variability. The data from this project can be used to estimate the number of tests required in order to achieve a given level of accuracy in estimating the true mean noise level of an engine or of an engine population. The results can also be used to design a test program that will provide a given level of confidence in determining whether there is a statistically significant difference between two engine populations.

A comprehensive formulation is presented for the dynamics of a rotating flexible crankshaft coupled with the dynamics of an engine block through a finite difference elastohydrodynamic main bearing lubrication algorithm. The coupling is based on detailed equilibrium conditions at the bearings. The component mode synthesis is employed for modeling the crankshaft and block dynamic behavior. A specialized algorithm for coupling the rigid and flexible body dynamics of the crankshaft within the framework of the component mode synthesis has been developed. A finite difference lubrication algorithm is used for computing the oil film elastohydrodynamic characteristics. A computationally accurate and efficient mapping algorithm has been developed for transferring information between a high - density computational grid for the elastohydrodynamic bearing solver and a low - density structural grid utilized in computing the crankshaft and block structural dynamic response.

A spectral-based substructuring approach applying linear frequency response functions (FRF) is proposed for improving the accuracy of simulating the dynamics of coupled systems. The method also applies a least square singular value decomposition (SVD) scheme to overcome the inherent computational deficiency in the basic substructuring formulation. The computational problem is caused by the magnification of measurement errors during any one of the matrix inversion calculations required for this method. The primary objective of applying this approach is to examine the possibility of analyzing higher frequency response that is normally not possible using conventional modeling technique such as the direct finite and boundary element, and lumped parameter techniques. In this study, additional concepts are also evaluated to quantify the limitations and range of applicability of the proposed substructuring approach for simulating the vibration response of complex powertrain structures.

Optimizing base engine design in view of performance, emission requirement, durability, and lighter weight has been a challenging work in automotive industry for a last couple of decades. While those functional requirements are designed and developed to be met, NVH requirement has been one of difficult objectives to be optimized in the design and development process, not only because of technical difficulties, but of the lesser degree of settlement of development process in a vehicle program. The combustion characteristic of an engine plays an important role in the performance, emission, and NVH development. In this paper, the engine radiation sound and mounting vibration have been measured simultaneously with the combustion pressure from each cylinder of a V8 engine while varying the engine speed under wide open throttle condition and spark timing.

In this paper, an interesting structural dynamics technique is presented to represent an operating deflection pattern, under order related forcing loads. In this technique, the measurements are performed using the Phase Assigned Spectrum technique with the use of reference and roving response accelerometers. Rotating components in car engines generate cyclic excitation forces at the fundamental rotational frequency and its harmonics and sub-harmonic components. This excitation will result in structural resonances being excited by those particular orders, at specific rotational speeds. The paper discusses in general the use of Order Tracking analysis under non-stationary conditions, for the determination of order-tracked deflection shapes obtained by Phase Assigned Spectrum analysis. A Vold-Kalman Order Tracking analysis is also performed on the set of data for extraction of time order waveforms or Phase Assigned Orders.

This paper discusses flexible, multi-body, coupled dynamic simulation of a crankshaft system acting upon a power plant structure that includes an engine block, cylinder heads, oil pan, crank train (i.e., crankshaft, connecting rods, bearings etc.) and transmission. The simulation is conducted using AVL/EXCITE [1]. Engine loads are first predicted, and then used to compute radiated noise from the engine assembly. Radiated noise level is computed by sweeping the excitation frequency through a range associated with the normal operating RPM of the engine. The results of the radiated noise computation are plotted on a “3D” Campbell plot diagram. The effects of different crankshaft materials is evaluated by imposing steel and cast iron material properties on the analysis model. A design of experiment (DOE) study is also performed to investigate the effects of main and rod bearing clearance, damper, and flexplate design on overall engine radiated sound power.

This paper presents the development of surrogate models (metamodels) for evaluating the bearing performance in an internal combustion engine without performing time consuming analyses. The metamodels are developed based on results from actual simulation solvers computed at a limited number of sample points, which sample the design space. A finite difference bearing solver is employed in this paper for generating information necessary to construct the metamodels. An optimal symmetric Latin hypercube algorithm is utilized for identifying the sampling points based on the number and the range of the variables that are considered to vary in the design space. The development of the metamodels is validated by comparing results from the metamodels with results from the actual bearing performance solver over a large number of evaluation points. Once the metamodels are established they are employed for performing probabilistic analyses.

Frequency response functions are frequently used production development to identify correlation levels between designs or between analytical simulation and tests. Frequency Response Assurance Criterion is one effective method to quantify such correlations. However, practical issues such as a large number of FRFs exist and complicated modal characteristics often prevent us using the traditional FRAC analysis. A Group FRAC method was developed and is introduced in this article to resolve these application difficulties. This Group FRAC method enables automatic and efficient processing of large number of FRFs in additional to other improvements. The benefit of using the Group FRAC is evidenced through practical applications.

Usual electromechanical horn technology doesn't allow any horn noise control and leaves disturbance vs. safety management to the civic sensibility of the drivers. Electronics, loudspeaker technology, multiplexing and psychoacoustics give the car designers as well as the public authorities new tools to control unnecessary horn noise without loosing safety or increasing costs. These technical solutions are already available, sometimes even applied for other purposes and don't require any major vehicle modification or cost increase. Furthermore, they can give car designers new sounding options and “Brand Management” opportunities without any public disturbance increase.

With the increasing demands to improve ride and handling, and CAFÉ requirements, the automakers are faced with evaluating alternative technologies to achieve new competitive standards. In particular, the use of structural foam as a reinforcing media for automotive hollow sections is being examined. The objective of this study is to examine the use of epoxy structural foam in a hollow section as an optimum reinforcing means, to compare the reinforcing performance of a solid fill versus a laminate configuration, and to determine critical design features that influence performance. For this comparative study, idealized hat shaped cross sections were physically tested in simple bending and are measured for dynamic stiffness. Beam compliance was measured over a range of input frequencies and was reported for a fully filled and laminate section.