Mohamad S. Qatu

Overview of automotive noise and vibration

Vehicle noise, vibration and harshness (NVH) is an important vehicle attribute. It is usually among the top five attributes in terms of its priority in the design of any vehicle type. Like other attributes of safety, performance, dynamics and fuel economy, this attribute has to be considered closely in the design process. This manuscript presents an overview of automotive NVH engineering. It classifies the interior noise into powertrain-related NVH, road- and tyre-related NVH and wind-related NVH. This paper also discusses brake- and chassis-related NVH, squeak and rattle and electromechanical-related NVH. In addition, the paper addresses exterior NVH, frequently described as drive-by NVH. The phenomenon is divided into usual or expected NVH and unusual or unexpected NVH. The paper provides a review of some of the recent literature in the field of automotive NVH.

Recent research on vehicle noise and vibration

Vehicle noise, vibration and harshness (NVH) is usually among the top five attributes in terms of its priority in the design of automotive vehicles. Its priority in other types of vehicles (e.g., aerospace) is also important. Like other attributes of safety, performance, dynamics, fuel economy, NVH has to be considered closely in the design process. This manuscript presents a summary of recent research in the general area of NVH with an emphasis in the automotive field. It follows up on a previous review and classifies the phenomena by the main sources of NVH into powertrain, road and tyre, wind and other NVH. The last includes brake and chassis, squeak and rattle, electromechanical NVH, exterior (or drive-by) NVH and others. The paper provides a review of some of the recent literature in this field.

Free vibration of thick laminated cylindrical shells with different boundary conditions using general differential quadrature

Equations of motion with required boundary conditions for deep and thick cylindrical composite shells are shown using two First-order Shear Deformation Theories. The difference between them is the inclusion of the effects of curvature in the evaluation of stiffness parameters. Equations of motion with stress resultants lead to a system of fifteen first-order differential equations for dynamics of cylindrical shells. These equations are solved numerically using the General Differential Quadrature method for free vibration of isotropic, cross-ply, angle-ply and general lay-up cylindrical shells with six types of different boundary conditions using the aforementioned theories. The first five frequency parameters and mode shapes which are obtained from both theories are compared with the available results in the literature and those obtained using a three-dimensional finite element analysis to test the accuracy of the shell theories presented here.

A Rigorous Beam Model for Static and Vibration Analysis of Generally Laminated Composite Thick Beams and Shafts

A first order shear deformation model for static and vibration analysis of composite thick beams and shafts is proposed and verified. The model is based on an earlier one proven to be accurate only for cross-ply laminates. The proposed model uses equivalent stiffness parameters that enable it to be accurate for every laminate. A three dimensional (3D) finite element model (FEM) is used to verify the proposed beam model. The results for different approaches for stiffness calculation were compared to the proposed model and those obtained by FEM in order to verify their accuracy. In addition, the model was applied to tubular cross section beams and the results were compared with experimental data and other models existing in the literature. The results of the proposed model were close to the 3D FEM as well as experimental results.

A MODEL AND EXPERIMENTAL INVESTIGATION OF BELT NOISE IN AUTOMOTIVE ACCESSORY BELT DRIVE SYSTEM

This paper presents a model to characterise V-ribbed belt (Micro-VTM) noise in accessory belt drive system (ABDS), or front-end accessory drive (FEAD) of automotive engines. It has been known that radial friction-induced vibrations generate belt misalignment noise and tangential friction-induced vibrations relates to belt slip noise. In this study, these two kinds of vibrations are found essentially different, and they are formulated mathematically by using forced vibration equation and self-excited vibration equation respectively. The formulations are consistent with conventional experimental results. A series of new tests were run to assess the properties of the belt noise using industry standard test rigs. The test results are agreeable with the results derived directly from the formulations. The proposed model is expected to provide accessory drive designers with insight into the issues associated with improving the overall noise performance of ABDS system.

Robustness of mount systems for idle NVH, Part I: Centre of Gravity (CG) mounts

A key parameter for frequency or modal separation of the powertrain is the basic mount design. For East-West engine configurations, there are two fundamental arrangements of mounts: the CG and pendulum arrangements. This paper discusses the variability of the modal separation of the powertrain rigid body modes as a function of the variability of the mount geometry and property parameters as well as sub-frame mount stiffness values. Six and 12 Degrees of Freedom (DOF) models are used in the analysis. Detailed Design of Experiment (DOE) studies are conducted.

Theory and Vibration Analysis of Laminated Barrel Thin Shells

This paper deals with analysis of laminated composite barrel shells. Barrel shells are essentially cylindrical shells for which the meridional direction of the shell has some initial curvature. The curvature may be due to imperfection in manufacturing, or is a part of the design as is the case in barrel shells. The equations are developed for the general dynamic analysis of laminated barrel shells and can be reduced to the static analysis and the free vibration analysis. Natural frequencies are obtained for open and closed, isotropic and laminated barrel shells having shear diaphragm boundary conditions. For composite shells, the effects of curvature, thickness, and orthotropy ratios as well as the lamination sequence on the nondimensional natural frequency parameters are studied.

Wet belt friction-induced dynamic instability and noise in Automotive Accessory Belt Drive Systems

This paper presents an investigation of V-ribbed belt (Micro-V TM ) wet friction and friction-induced slip noise in Accessory Belt Drive Systems (ABDS). A set of experiments was conducted by using an industry standard test rig and a standard material friction tester. A theoretical analysis and model are presented to elaborate the results. The tribological property of the interface is characterised to be unsteady mixed lubrication with water, which possesses the feature of negative slope of friction with velocity. The friction-induced dynamic instability and noises are also investigated. It is shown that the noise is directly associated with the negative slope of the friction-velocity curve.

Nonlinear seat cushion and human body model

This paper presents the nonlinear characteristics of typical automotive seat cushion structure. As discussed in an earlier paper by the authors (Pang et al., 2004), the experimental transfer functions between the seat butt and the seat track vary with changes in the excitation levels. Both the magnitudes and frequencies of the transfer functions shift to smaller values as the excitation increases. Two nonlinear models are established to reveal this nonlinear phenomenon in the automotive seats. One of the models is combined with the ISO linear human body model to form a nonlinear seat-human body model. The simulated transfer functions between the head and the seat track, between the body and the seat track, and between the seat butt and the seat track are correlated with experimental results. The models proposed here are intended to help engineers optimise the ride quality of the vehicle.

Vibration of Homogeneous and Composite Thick Barrel Shells

This paper presents a vibration analysis for homogeneous and laminated composite deep, thick barrel shells using recently derived equations of elastic deformation. Assuming a first-order linear displacement field, the equations include accurate force and moment resultants, in which the stresses over the thickness of the shell are integrated exactly on a trapezoidal-like cross-section of a shell element. Exact solutions were obtained for thick barrel, open and closed, shells having shear diaphragm boundary conditions and cross-ply lamination sequence. The results were compared with previously obtained results where various other thick shell theories were used. The effects of various parameters including radii of curvature on shell frequencies are studied.