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This paper presents the design development of a SUV liftgate with the intention of minimizing low frequency noise. Structure topology optimization techniques were applied both to liftgate and body FEA models to reduce radiated power from the liftgate inner surface. Topology results are interpreted into structural changes to the original liftgate and body design. Favorable results of equivalent radiated power (ERP) performance with reduced cost and mass is shown compared to baseline liftgate and baseline with tuned vibration absorber (TVA). This simulation includes finite element modeling of coupled fluid/structure interaction between the interior air cavity volume and liftgate structure. In addition to ERP minimization, multi-model optimization (MMO) was used on separate models simultaneously to preserve liftgate structural performance for several customer usage load cases.

Exterior component integration presents competing performance challenges for balanced exterior styling, safety, ‘structural feel’ [1] and durability. Industry standard practices utilize noise and vibration mode maps and source-path-receiver [2] considerations for component mode frequency placement. This modal frequency placement has an influence on ‘structural feel’ and durability performance. Challenges have increased with additional styling content, geometric overhang from attachment points, component size and mass, and sensor modules. Base excitation at component attachment interfaces are increase due to relative positioning of the suspension and propulsion vehicle source inputs. These components might include headlamps, side mirrors, end gates, bumpers and fascia assemblies. Here, we establish basic expectations for the behavior of these systems, and ultimately consolidate existing rationales that are applied to these systems.

The Lockheed Martin Low-Speed Wind Tunnel (LSWT) is a closed-return wind tunnel with two solid-wall test sections. This facility originally entered into service in 1967 for aerodynamic research of aircraft in low-speed and vertical/short take-off and landing (V/STOL) flight. Since this time, the client base has evolved to include a significant level of automotive aerodynamic testing, and the needs of the automotive clientele have progressed to include acoustic testing capability. The LSWT was therefore acoustically upgraded in 2016 to reduce background noise levels and to minimize acoustic reflections within the low-speed test section (LSTS). The acoustic upgrade involved detailed analysis, design, specification, and installation of acoustically treated wall surfaces and turning vanes in the circuit as well as low self-noise acoustic wall and ceiling treatment in the solid-wall LSTS.

Transmission Control Module (TCM) bracket is mounted on the vehicle chassis and is subjected to the random load excitation due to the uneven surface of the road. Assembly of the TCM bracket on the vehicle chassis induces some constant stress on it due to bolt preload, which acts as a mean stress along with the varying random loads. It is important for a design engineer and CAE analyst to understand the effect of all sources of loads on vehicle mount brackets while designing them. The objective of this study is to consider the effect of mean stress in the random vibration fatigue assessment of TCM bracket. The random vibration fatigue analyses are performed for all the three directions without and with consideration of mean loads and results are compared to show the significance of mean stresses in random vibration fatigue life.

ISO has revised the 10844 International Standard for test surfaces used in measurement of exterior vehicle and tire noise emission. The revision has a goal to reduce the track to track sound level variation presently observed by 50%, without changing the mean value. ISO has incorporated improved texture measurement procedures, improved acoustic absorption measurement procedures, and has added measurement procedures for track roughness. In addition, specifications for texture, absorption, roughness, planarity, and asphalt mix were revised or added to recognize improved technical methods and to achieve the goal of variation reduction. The specification development was supported by a construction program where four candidate ISO 10844 tracks were constructed in Japan, France, and the US to verify the technical principles and to validate construction process capability. This paper will address the technical changes and reasons for these changes in the revised ISO 10844.

A Machine Learning (ML) approach is presented to correlate in-cylinder images of early flame kernel development within a spark-ignited (SI) gasoline engine to early-, mid-, and late-stage flame propagation. The objective of this study was to train machine learning models to analyze the relevance of flame surface features on subsequent burn rates. Ultimately, an approach of this nature can be generalized to flame images from a variety of sources. The prediction of combustion phasing was formulated as a regression problem to train predictive models to supplement observations of early flame kernel growth. High-speed images were captured from an optically accessible SI engine for 357 cycles under pre-mixed operation. A subset of these images was used to train three models: a linear regression model, a deep Convolutional Neural Network (CNN) based on the InceptionV3 architecture and a CNN built with assisted learning on the VGG19 architecture.

This paper presents the work of the SAE Brake NVH Standards Committee in developing a draft Low-Frequency Brake Noise Test Procedure. The goal of the procedure is to be able to accurately measure noise issues in the frequency range below 900 Hz using a conventional shaft brake noise dynamometer. The tests conducted while evaluating alternative test protocols will be discussed and examined in detail. The unique issues encountered in developing a suitable test procedure for low-frequency noise will be discussed, and the results of tests using both shaft brake dynamometers and chassis dynamometers will be described. The current draft procedure incorporating the knowledge gained from this development effort will be described in detail and conclusions as to its applicability will also be presented

During the development of an automotive acoustic package, valuable information can be gained by visualizing the acoustic energy flow through the Front-of-Dash (FOD) when a sound source is placed in the engine compartment. Two of the commonly used methods for generating the visual map of the acoustic field include Sound Intensity measurements and array technologies. An alternative method is to use a tracked 3-dimensional acoustic probe to scan and visualize the FOD in real-time when the sound source is injecting noise into the engine compartment. The scan is used to focus the development of the FOD acoustic package on the weakest areas by identifying acoustic leaks and locations with low Transmission Loss. This paper provides a brief discussion of the capabilities of the tracked 3-D acoustic probe, and presents examples of the implementation of the probe during the development of the FOD acoustic package for two mid-sized sedans.

Hybrid powertrain vehicles inherently create discontinuous sounds during operation. The discontinuous noise created from the electrical motors during transition states are undesirable since they can create tones that do not correlate with the dynamics of the vehicle. The audible level of these motor whines and discontinuous tones can be reduced via common noise abatement techniques or reducing the amount of regeneration braking. One electronic solution which does not affect mass or fuel economy is Masking Sound Enhancement (MSE). MSE is an algorithm that uses the infotainment system to mask the naturally occurring discontinuous hybrid drive unit and driveline tones. MSE enables a variety of benefits, such as more aggressive regenerative braking strategies which yield higher levels of fuel economy and results in a more pleasing interior vehicle powertrain sound. This paper will discuss the techniques and signals used to implement MSE in a hybrid powertrain equipped vehicle.

There is higher and higher demand by customers for vehicles with the maximum level of comfort, this aspect being a target to be achieved together with the general trend to increase performance and also with the necessity to reduce engine out emissions to satisfy the new environmental regulations. GMDAT has recently developed new EU5 2.0 and 2.2 liter L4-cylinder turbocharged Diesel engines that, to address customer demands, have improved power, lower exhaust gas emissions and NVH performance aligned to best in class in its segment. With the final aim of making this engine best in class from an NVH perspective, the NVH development has been executed in a very structured way, going through target setting and deployment, concept and design, combustion and mechanical development through computational analysis first and subsequently experimental tests.

The primary function of damping treatment on a vibrating panel in a vehicle is to reduce vibration levels or radiated sound power by the dissipation of energy. However, in automotive applications the mass effects of damping materials should not be ignored, especially with regard to airborne noise performance. In this paper, a Finite Element-Statistical Energy Analysis (FE-SEA) hybrid analysis is used to evaluate the mass effects of applied damping materials on Sound Transmission Loss (STL). The analysis takes into consideration effects on both the elastic properties and modal mass of the panel. It is shown that while uniformly distributing the mass of the damping material over the panel generally over-estimate the mass effects on STL, an area weighting approach underestimates the effects. Results are confirmed by laboratory testing. A nomogram is generated to show the total effect of the mass of the damping material on STL.

Styrene-Butadiene Rubber (SBR), a copolymer of butadiene and styrene, is widely used in the automotive industry due to its high durability and resistance to abrasion, oils and oxidation. Some of the common applications include tires, vibration isolators, and gaskets, among others. This paper characterizes the dynamic behavior of SBR and discusses the suitability of a visco-elastic model of elastomers, known as the Kelvin model, from a mathematical and physical point of view. An optimization algorithm is used to estimate the parameters of the Kelvin model. The resulting model was shown to produce reasonable approximations of measured dynamic stiffness. The model was also used to calculate the self heating of the elastomer due to energy dissipation by the viscous damping components in the model. Developing such a predictive capability is essential in understanding the dynamic behavior of elastomers considering that their dynamic stiffness can in general depend on temperature.

In traditional FE based structure-borne noise analysis, interior trims are normally modeled as lump masses in the FE structure model and acoustic specific impedance of the trim is assigned to the FE acoustics model when necessary. This simplification has proven to be effective and sufficient for low frequency analysis. However, as the frequency goes into the mid-frequency range, the elastic behavior of the trim may impose some effects on the structural and acoustic responses. The approach described in this paper is based on the structural FE and acoustic SEA coupling analysis developed by ESI, aiming to improve the modeling efficiency for a possible quick turnaround in virtual assessments.

Flexible molded polyurethane foams are widely used in automotive industry. As porous-elastic materials, they can be used as decoupler layers in conventional sound insulation constructions or as sound absorbers in vehicle trim parts. Flexible molded polyurethane foams are produced by reacting of liquid Isocyanate (Iso) with a liquid Polyol blend, catalysts, and other additives. Their acoustic performance can be changed by varying the mixing ratio, the weight proportion of two components: Iso and Polyol. Consequently, the sound insertion loss (IL) of barrier/foam constructions and acoustic absorption of a single foam layer will vary. In this paper, based on one industry standard flexible molded polyurethane foam process, the relationship between foam mixing ratio and foam acoustic performance is studied in terms of IL and sound absorption test results.

To achieve high robustness and quality, automotive ECUs must initialize from low-power states as quickly as possible. However, microprocessor and memory advances have failed to keep pace with software image size growth in complex ECUs such as in Infotainment and Telematics. Loading the boot image from non-volatile storage to RAM and initializing the software can take a very long time to show the first screen and result in sluggish performance for a significant time thereafter which both degrade customer perceived quality. Designers of mobile devices such as portable phones, laptops, and tablets address this problem using Suspend mode whereby the main processor and peripheral devices are powered down during periods of inactivity, but memory contents are preserved by a small “self-refresh” current. When the device is turned back “on”, fully initialized memory content allows the system to initialize nearly instantaneously.

In today's competitive market, noise and vibration are among the most important parameters that impact the success of a vehicle. In body-on-frame construction vehicles, elastomeric body mounts play a major role in isolating the passenger compartment from road noise, harshness, shake, and other vibrations in the chassis as well as improving ride quality across a wide frequency range. This paper describes the work carried out to design a fluid filled mount with high lateral stiffness that can alter the perceived Noise, Vibration and Harshness (NVH) performance of current production body-on-frame trucks. It was found that the quietness and ride qualities can be significantly improved by positioning the glycol-filled mounts at the anti-node of the frame first vertical bending mode; under the C-pillar intersection with the frame. The performance of mounts in this area is known to be critical to ride quality.

This paper reviews the relationship between taper wheel bearing damage and vehicle noise and vibration for a body-on-frame pickup truck and a body-on-frame SUV. In addition to understanding how the different levels of bearing damage relate to vehicle noise, it also discusses the level of noise versus the damaged bearing’s position in the vehicle. For this study, the wheel bearing supplier provided front and rear bearings with various amounts of Brinell damage to the bearing raceways. The different bearings were evaluated subjectively for noise in the vehicle. After vehicle testing, the bearing raceway Brinell depths were measured to correlate the level of bearing damage to vehicle noise. The study shows the relationship between bearing Brinell dent depth and vehicle noise for body-on-frame light trucks and SUVs. The noise was most apparent in vehicles between 45 and 60 mph. For bearings with moderate levels of damage, steering inputs were required to hear noise.

A primary goal of large eddy simulation, LES, is to capture in-cylinder cycle-to-cycle variability, CCV. This is a first step to assess the efficacy of 35 consecutive computed motored cycles to capture the kinetic energy in the TCC-III engine. This includes both the intra-cycle production and dissipation as well as the kinetic energy CCV. The approach is to sample and compare the simulated three-dimensional velocity equivalently to the available two-component two-dimensional PIV velocity measurements. The volume-averaged scale-resolved kinetic energy from the LES is sampled in three slabs, which are volumes equal to the two axial and one azimuthal PIV fields-of-view and laser sheet thickness. Prior to the comparison, the effects of sampling a cutting plane versus a slab and slabs of different thicknesses are assessed. The effects of sampling only two components and three discrete planar regions is assessed.

Today’s automotive customers have come to expect luxury and electric vehicles to be quiet and refined pieces of machinery. As customers have come to expect powertrain cancellation in most vehicles today, they are also increasingly looking for a reduction in road noise to improve their overall perception of luxury and electric vehicles. While the field of noise cancellation is ever expanding, several auto makers are exploring the possibility of introducing a real time Road Noise Cancellation (RNC) system to meet these customer expectations. An RNC system can be integrated into the vehicle infotainment system and be utilized to either noticeably reduce or shape the vehicle noise floor. This paper will look at the current traditional Noise and Vibration (N&V) methods of reducing road noise and then also the benefits associated with actively controlling the amount of road noise using an RNC system.

Torque ripple from electric motor can excite a system resonance perceived as vibration at the vehicle seat track. The CAE simulation procedure was applied to analyze the seat track acceleration excited by electric motor torque ripple. In this study, the transfer function between the electric motor torque and vehicle level seat track acceleration was developed, and it incorporates the control capability and vehicle sensitivity subfunctions. The motor level torque ripple requirement was developed, which can support motor design in early vehicle development stage based on vehicle level criteria. The analysis results obtained for motor level torque ripple requirement shows good agreement with the experimental validation using vehicle test data. The variation study on control capability and vehicle sensitivity was investigated, and the results can help to identify the solution to improve vehicle torque ripple response.