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Increased focus on fuel efficiency and vehicle emissions has led the automotive industry to look into low weight alternative designs for powertrain system components. These new design changes pose challenges to vehicle attributes like NVH, durability, etc. Further, the requirement of high power applications produces even more complexities. The present work explains how a potential design change of half shafts driven by a desire to reduce weight and cost can lead to NVH problems caused by half shaft resonances and explains how using multiple dynamic vibration absorbers can solve the issue to meet customer expectation while improving efficiency. With the aid of Finite Element Analysis (FEA) & optimization software, interactions between multiple DVA’s on a system was understood and optimal damper parameters for effective damping was identified. The final DVA design was tested and verified on the vehicle for optimal attribute performance.

Automotive vehicles equipped with Cardan joints may experience low frequency vehicle launch shudder vibration (5-30Hz) and high frequency driveline moan vibration (80-200Hz) under working angles and speeds. The Cardan joint introduces a 2nd order driveshaft speed variation and a 4th order joint articulation torque (JAT) causing the vehicle shudder and moan NVH issues. Research on the Cardan joint induced low frequency vehicle shudder using a Multi-Body System (MBS) method has been attempted. A comprehensive MBS method to predict Cardan joint induced high frequency driveline moan vibration is yet to be developed. This paper presents a hybrid MBS and Finite Element Analysis (FEA) approach to predict Cardan joint induced high frequency driveshaft moan vibration. The CAE method considers the elastically coupled driveshaft bending and engine block vibration due to Cardan joint excitation.

Hybrid electric vehicles are continuously challenged to meet cross attribute performance while minimizing energy usage and component cost in a very competitive automotive market. As electrified vehicles become more mainstream in the marketplace, hybrid customers are expecting more attribute refinement in combination with the enhanced fuel economy benefits. Minimizing fuel consumption, which tends to drive hybrid powertrain engines to operate under lugging type calibrations, traditionally challenge noise, vibration, and harshness (NVH) metrics. Balancing the design space to satisfy the cost metrics, energy efficiency, noise and vibration & drivability under the hybrid engine lugging conditions can be optimized through the use of multiple CAE tools. This paper describes how achieving NVH metrics can put undesirable boundaries on Powertrain Operation which could affect other performance attributes.

A low-frequency vehicle shuffle can be excited when a reversal of torque occurs in a vehicle's drivetrain. It usually occurs during a throttle tip-in or tip-out event, or a static engagement shift event. This drivetrain shuffle vibration can introduce a vehicle fore-aft vibration that may affect the customer satisfaction of ride comfort and/or powertrain performance. Vehicle test data of the seat track acceleration from a 30 MPH wide-open-throttle tip-out event suggested a strong coupling between the CVT drivetrain shuffle and vehicle fore-aft vibration. An ADAMS based CVT model was developed and integrated into a full vehicle model for dynamic simulation of this vehicle shuffle issue. CAE DOE studies were performed to identify key vehicle and powertrain design parameters that could directly impact the vehicle shuffle vibration. Experimental tests were performed to verify the CAE design improvements of the CVT vehicle shuffle vibration.

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.

Recent surveys of customer satisfaction with full size pickup trucks have raised the standards for passenger comfort and refinement of such vehicles. Customers for this type of vehicle demand performance levels for attributes such as NVH, ride, and handling that previously belonged to luxury passenger cars. Along with the increased passenger comfort, full size pickup trucks must retain a tough image and be as durable as the previous generation trucks. The challenge is to design for NVH performance that can match and surpass many well behaved and “good” NVH passenger cars without any compromise in durability performance. One aspect of “good” NVH is a steering wheel which is free from vibration. As part of the development of a new design for a full sized pick up truck, an NVH subjective rating of 8-9 (10 is maximum) was targeted for the design of steering column/ instrument panel assembly.

Automotive refrigerant system induced noise and vibration transients usually accompany A/C compressor engagement/disengagement. These transients include audible/perceivable metallic impact/slip (clink, chirp, etc.), engagement thump, delayed accumulator thump, orifice tube/TXV induced hiss, and occasionally very loud slugging. In this paper, the inherent noise source mechanisms of these transients are described, and a set of psychoacoustics based objective metrics quantifying these transients in terms of loudness and sharpness is developed. Some of the recommended design-fixes and noise control approaches for the related transient noises are also discussed.

The steering wheel is one of the primary sensory inputs for vehicle vibration while driving. Past research on hand-arm vibration has focused on a hand gripping a rod or a hand on a flat plate. Little work has focused on the perception of vibration felt through an automotive steering wheel. This paper discusses the investigation conducted at Ford's Vehicle Vibration Simulator Lab to develop equal annoyance contours for hand-arm vibration. These contours were developed for four different degrees-of-freedom: vertical, lateral, longitudinal and rotation about the steering wheel center. Rotation about the steering wheel is commonly induced by a 1st order tire non-uniformity force and imbalance of the wheel/tire. These 1st order excitation forces generate vibration in the frequency range of 8-20 Hz.

When driving or riding in a vehicle, the customer is bombarded with sensory stimuli. These include tactile, auditory, olfactory and visual. In addition, the customer may be asked to perform various routine driving tasks that can have an influence on the perception of each of the aforementioned senses. Or perhaps, the influence of one sense may affect the perception of another. Since sound rarely occurs void of felt vibration and vice-versa, there is reason to believe one may influence the perception of the other, or that the two may interact in some way when the customer is exposed to a particular NVH (Noise Vibration and Harshness) event in a vehicle. The NVH engineer wishes to gage a sound or vibration's impact on the customer and make a determination as to whether corrective actions on the vehicle are necessary. NVH issues routinely show up as top warranty and customer satisfaction concerns.

The shifter lever is one of the main customer contact points in the vehicle. Vibration levels at this contact point have an effect on perceived vehicle quality. For this reason, shifter lever vibration and the corresponding transfer paths from the transmission to the shifter lever need to be considered during vehicle development. On a recent program, experimental measurements identified the shifter cable to be a significant transfer path for shifter lever vibration. An integrated Computer Aided Engineering (CAE) and experimental effort was undertaken to model and optimize the shifter lever and cable assembly for reduced vibration. Experimental data was used to better understand the vibration phenomenon, set boundary conditions for the CAE modeling, and for correlation. The CAE model contains the shifter lever assembly and a detailed cable assembly model.

Transient road disturbances excite complex vehicle responses involving the interaction of suspension/chassis, powertrain, and body systems. Typical ones are due to the interactions between tires and road expansion joints, railway crossings and other road discontinuities. Such transient disturbances are generally perceived as “impact harshness” due to the harshness perception as sensed by drivers through both sound and vibration. This paper presents a study of quantifying the effects of sound, steering wheel and seat/floorpan vibrations on the overall perception of the “impact harshness” during impact transient events. The Vehicle Vibration Simulator (VVS) of the Ford Research Laboratory was used to conduct this study. The results of the study show that sound and vibration have approximately equal impact on the overall perception of impact harshness. There is no evidence of interaction between sound and vibration.

An automobile and a tracked military vehicle were instrumented with multiple tachometers, one for each drive wheel/sprocket and operated with accelerometers mounted at suspension, chassis, and powertrain locations on the vehicles. The Time Variant Discrete Fourier Transform, TVDFT, order tracking method was then used to extract the order tracks and operating shapes estimated based on each tachometer. It is shown that under some conditions a different operating shape is excited by each of the wheels/sprockets simultaneously. This is due to the asymmetries present in the vehicles. The strengths of the TVDFT order tracking method are shown for this type of analysis, which is difficult due to the closeness, within 0.001 orders, and crossing of the orders. Benefits of using multiple tachometers and advanced order tracking methods become apparent for solving a class of noise and vibration problems.

It is a well-know fact that cost and time-to-market constraints have gained an ever-increasing importance in the recent years in the global automotive industry. Either due to economic problems in emerging markets or to the presence of strong competition is US and Europe, automakers strive, using different strategies, to find ways of satisfying these constraints. One of the most promising tools to assist in reducing both development cost and time is CAE (Computer Aided Engineering) or Virtual Prototyping which, by using numerical models of components, systems and/or vehicles, is capable of assessing their behavior in areas such as noise, vibration and harshness (NVH), durability, impact safety and vehicle dynamics. A very important question that is frequently faced by CAE development teams is related to how well the numerical results match those that will be obtained when the vehicle is actually built.

Simulation tools usage in the automotive industry has faced a significant increase in the last decade, due to the significant advantages of time and cost reduction opportunities it can potentially provide. Therefore new modeling techniques are constantly developed in order to increase the correlation between simulated and physical test results. In particular, modeling of spot welds plays a very important role in defining the accuracy of a finite element model, mainly with large models, such as a complete trimmed body, have to be dealt with. The properties of a welded set depends on a significant number of variables, such as the temperature during welding, the compression load created by the welding probe and geometric variation of the nugget position. Although it is not possible to take all those variables into account in a finite elements model, a good modeling strategy should produce acceptable results even when those are neglected or only modeled in an approximate way.

Squeak and rattle is an important sub Noise and Vibration attribute which can be easily noticed by the costumer. A rattle was observed at seat belt retractor during subjective evaluation at a special test on a rough road It was developed an objective metric, in laboratory, with the aim to establish an acceptance criteria for the part. The objective of this paper is to show how noise, vibration and harshness engineers worked on the correlation between subjective and objective evaluation concerning this rattle.

Finite element simulations of powertrain assemblies and components such as an engine block, transmission case, and structural oil pan, are regularly carried out at Ford Motor Company to provide directions for design improvements relevant to durability, minimum weight, noise and vibration characteristics. This paper presents hands-on experience with analyses of two powertrains in terms of computational strategies and resource requirements. The course of future analysis work in the light of current developments in computer technology, is also presented.

Disc brake squeal is always a challenging multidisciplinary problem in vehicle noise, vibration, and harshness (NVH) that has been extensively researched. Theoretical analysis has been done to understand the mechanism of disc brake squeal due to small disturbances. Most studies have used linear modal approaches for the harmonic vibration of large models. However, time-domain approaches have been limited, as they are restricted to specific friction models and vibration patterns and are computationally expensive. This research aims to use a time-domain approach to improve the modeling of brake squeal, as it is a dynamic instability issue with a time-dependent friction force. The time-domain approach has been successfully demonstrated through examples and data.

The use of plastics and elastomers, for interior and exterior automotive components, presents a risk of frictionally incompatible materials contacting each other, resulting in squeaks, ticks, chirps… Ford's NVH S&R Department, and MB Dynamics have developed a tester (Figures 1 and 2) that can measure friction, and sound, as a function of sliding velocity, normal load, surface roughness, and environmental factors that allows us to provide up-stream engineering information to Forward Model Design Engineers. When material pairs undergo sliding contact, friction forces can cause elastic deformation adjacent to the contacting surfaces. The elastic deformation is a mechanism for storing energy and sound is produced when the energy is released. The sound that we hear may be a squeak or squeal (multiple stick-slip) or a tick (single stick-slip).

During the design conception of an automobile, typically low-fidelity physics-based simulations are coupled with engineering judgement to define key architectural components and subsystems which limits the capability to identify NVH issues arising from systems interaction. This translates to non-optimal designs because of unexplored design opportunities and therefore, lost business efficiencies. The sparse design information available during the design conception phase limits the development of representative higher fidelity physics-based simulations. To address that restriction on design optimization opportunities, this paper introduces an alternate approach to develop reduced order predictive models using regression techniques by harnessing historical measurement and simulation data. The concept is illustrated using two driveline NVH phenomenon: axle whine and take-off shudder.

Exhaust sensors and actuators used in automotive applications are subjected to wide variety of operating ambient conditions , the performance of these actuators is challenging especially at cold ambient operating conditions, active exhaust tuning valves with position sensors are used to adjust the sound levels, or noise, vibration and harshness (NVH) from a control unit within the vehicle that leads to an improved driving experience wherein the driver selects their preferred sound levels. However, the operating behavior is crucially influenced by the characteristics of the drive cycle and ambient temperature. The study in this paper is intended to evaluate the icing formation at the start of drive cycle and at different ambient temperature conditions. The test data were obtained through real road and chassis dyno testing at different ambient conditions.