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With rising fuel prices, lightweight structures and materials (like composites) are receiving more attention. Composite materials offer high stiffness to weight and strength to weight ratios when compared with traditional metallic materials. Traditionally, composite materials were generally costly which made them only attractive to very limited industries (e.g., the defense industry). Advances in their manufacturing and new innovations have brought the cost of these materials down and made them reasonably competitive. They have gained more and more usage in the last 3 decades in the aerospace industry and have recently been gaining more usage in the automotive industry. In automotive design, they yield lighter structures which have positive impact on attributes like fuel economy, emission and others. Proper modeling and analyses need to be performed to make sure that other attributes (e.g. durability, noise, vibration and harshness or NVH) are assessed properly and remain competitive.

With rising fuel prices, light weight structures and materials (like composites) are receiving more attention. Composite materials offer high stiffness to weight ratio when compared with traditional metallic materials. Traditionally, composite materials were generally costly which made them only attractive to very limited industries (e.g., the defense industry). Advances in their manufacturing and new innovations have brought the cost of these materials down and made them reasonably competitive. They have gained more and more usage in the last 3 decades in the aerospace industry and have recently been gaining more usage in the automotive industry. In automotive design, they yield lighter structures which have positive impact on attributes like fuel economy, emission and others. Proper modeling and analyses need to be performed to make sure that other attributes (e.g. noise, vibration and harshness or NVH) are assessed properly and remain competitive.

This paper studies the dynamics and noise of timing belt. A comprehensive theoretical contact dynamics model for belt tooth-sprocket tooth pair is developed. The general belt dynamics model in conjunction with the contact model is used to quantify the impact-sliding process of belt tooth. The effect of tooth meshing process is illustrated which results in the vibrations of belt span and tooth vibrations. The structural borne noise consists of structural impact portion and friction-induced portion. The relationship between system parameters and noise is quantified. The air borne noise due to air-pumping is investigated based on Lighthill's equation. A comprehensive model is developed and the spectrum signatures of the air-pumping noise are illustrated.

Serpentine belt system has been widely used to drive automotive accessories like power steering pump, alternator, and A/C compressor from a crankshaft pulley. Overload under severe conditions can lead to excessive slippage in the belt pulley interface in poorly designed accessory systems. This can lead to undesirable noise that increases warranty cost substantially. The mechanisms and data of these tribology performance, noise features and system response are of utmost interest to the accessory drive designers. As accessories belt systems are usually used in ambient condition, the presence of water on belt is unavoidable under the raining weather conditions. The presence of water in interface induces larger slippage as the water film in interface changes the friction mechanisms in rubber belt-pulley interface from coulomb friction to friction with mixed lubrication that has negative slope of coefficient of friction (cof) - velocity.

The objective of this paper is to explore the dynamic features of vibrations and instability in automotive front end accessory drive belt system. To address this issue, a non-linear model of a moving beam with friction coupling on elastic foundation is developed. The model takes into account of a variety of nonlinear effects, including the contact stiffness nonlinearity, nonlinearities associated with the friction, tensioned parametric excitation, as well as the beam geometry nonlinearity. Different nonlinear properties are examined, and numerical simulations are conducted to investigate the system and to correlate with the experimental results. The major contributors to the dynamic contact instability are illustrated and are attributed to modal coupling and/or negative damping.

This paper introduces a cumulative effort on the phenomenon of exhaust flow exited noise. The mechanisms of engine combustion noise via the exhaust system and flow excited noise are analyzed. Engine combustion noise contributes most to tailpipe noise at lower engine speed while flow excited noise dominates the tailpipe noise at high engine speed. WAVE model, a one dimension CFD and Acoustics model, is used to distinguish the engine combustion noise and flow excited noise. Both CAE and tests based results are used to draw conclusions. The influence of single system and quasi-dual system on the tailpipe noise is compared with each other. The paper analyzes the balance of different diameter pipes to achieve the desired sound at different rpm range. The evaluation balance between interior sound and tailpipe noise is described.

This paper analyzes the relation between sound pressure at tailpipe and exhaust Y-pipe structure. The length of Y-pipe influences sound order distribution that influences customers' responsiveness of sound. The equal Y-pipe remains the firing order and its harmonic contents while suppressing the half order and other whole order sounds. Various lengths of equal Y-pipe also influence the magnitude and frequency distribution of tailpipe noise. An air-to-air (induction-engine-exhaust) CAE model is built to predict tailpipe noise using up-to-date software. The real air-to-air model simulation shows that the 3rd and 6th orders are the dominating contents for equal Y-pipe exhaust system in 6-cylinder engine applications. The sound pressure of the half order contents increases with the length difference between two branches of a Y-pipe. The results are useful for exhaust Y-pipe design.

The function of flex decoupler is to reduce the vibration transferred from the engine to the vehicle body. The stiffness of the flex decoupler is a key parameter in the vibration control. This paper deals with decoupling exhaust hot end and cold end to minimize vibration transfer. A computer aided engineering (CAE) based design of experiment (DOE) is used to investigate the coupling stiffness. A finite element model is built to analyze the exhaust vibration responses. Robustness of the exhaust system is analyzed. The analysis reveals that vertical stiffness of the flex decoupler is the key parameter for the hanger force response. The main control factors for exhaust vertical and lateral bending frequencies are vertical and lateral stiffnesses of the decoupler, respectively.

Powertrain mounts are one of the important design characteristics of a vehicle. Powertrain is mostly mounted to the front subframe and once installed in a vehicle, powertrain mounting has an important role in determining the vehicle vibration characteristics. A good mounting system isolates engine input vibration from the vehicle body and minimizes the effect of road inputs to the customer. This paper discusses results of several dynamic models as they relate to noise, vibration and harshness (NVH) and compares the accuracy of these models. Various powertrain models are studied and their accuracy in comparison with full a vehicle model is discussed.

The reduction of powertrain noise, vibration and harshness (NVH) in modern vehicles resulted in unmasking other NVH issues and concerns in the vehicle. One of these concerns is driveline NVH. Driveline NVH is one of the customer complaints that appear in various forms including warranty. One of the main issue that drive this phenomenon is vehicle to vehicle variability. This is driven mainly by the variability of driveline imblance from one vehicle to the next as well as the variability of vehicle sensitivity to imbalance from vehicle to vehicle. One of the key reasons for such variability is the axle mounts themselves. This paper addresses the issue of variability, and robustness, of axle mount system to driveline NVH.

Pump whine as well as other NVH issues related to power steering system can become customer concerns at the vehicle level. In order to avoid that, proposed treatment of the pump structure and its installation on the engine should be performed. This is particularly important because most vane pumps have a wide range of excitation that can reach 1000 Hz (30th order @ 6000 rpm). This requires maximizing the ‘as installed’ frequencies of the pump to avoid coincidence with the engine and other FEAD harmonics.

This paper summarizes the attributes of automotive exhaust system and provides a guideline for exhaust system design, analysis and development. The exhaust system has various attributes including vibration, acoustics or noise, durability and thermal distribution, flow and power loss, emission, in addition to its interface with vehicle. This paper describes all these attributes and the corresponding performances, and develops criteria for each of the attributes. The paper also describes the interfaces between the exhaust system and powerplant with body structure.

Higher demands from automotive customers for quieter vehicles and the reduction of noise and vibration levels from major sources like the engine necessitate better performance of other sources of noise and vibrations in a vehicle. One of these sources that Original Equipment Manufacturers (OEM) demand making quieter is the power steering system. The pressure ripple generated by the power steering pump transfers to the fluid lines where it can generate objectionable noise and vibrations. This can become an excitation force to the structure of a vehicle or the steering gear and can become a source of discomfort to the vehicle occupants. Attenuation of the pressure ripple within the hose assembly can result in significant reduction in noise inside the vehicle. The NVH research team at the Fluid System Products of Dana Corporation has developed “Dana's Virtual Test Rig (DVTR™),” - a hydraulic system simulation software.