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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.

Disc brakes operate with very close proximity of the brake pads and the brake rotor, with as little as a tenth of a millimeter of movement of the pads required to bring them into full contact with the rotor to generate braking torque. It is usual for a disc brake to operate with some amount of residual drag in the fully released state, signifying constant contact between the pads and the rotor. With this contact, every miniscule movement of the rotor pushes against the brake pads and changes the forces between them. Sustained loads on the brake corner, and maneuvers such as cornering, can both produce rotor movement relative to the caliper, which can push it steadily against one or both of the brake pads. This can greatly increase the residual force in the caliper, and increase drag. This dependence of drag behavior on the movement of the brake rotor creates some vehicle-dependent behavior.

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.

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.

The comfort assessment of seats in the automotive industry has historically been accomplished by subjective ratings. This approach is expensive and time consuming since it involves multiple prototype seats and numerous people in supporting processes. In order to create a more efficient and robust method, objective metrics must be developed and utilized to establish measurable boundaries for seat performance. Objective measurements already widely accepted, such as IFD (Indentation Force Deflection) or CFD (Compression Force Deflection) [1], have significant shortcomings in defining seat comfort. The most obvious deficiency of these component level tests is that they only deal with a seats' foam rather than the system response. Consequently, these tests fail to take into account significant factors that affect seat comfort such as trim, suspension, attachments and other components.

In the context of vehicle electrification, improving vehicle aerodynamics is not only critical for efficiency and range, but also for driving experience. In order to balance the necessary trade-offs between drag and downforce without significant impact on the vehicle styling, we see an increasing amount of active aerodynamic solutions on high-end passenger vehicles. Active rear spoilers are one of the most common active aerodynamic features. They deploy at high vehicle speed when additional downforce is required [1, 2]. For a vehicle with an active rear spoiler, the aerodynamic performance is typically predicted through simulations or physical testing at different static spoiler positions. These positions range from fully stowed to fully deployed. However, this approach does not provide any information regarding the transient effects during the deployment of the rear spoiler, which can be critical to understanding key performance aspects of the system.

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.

Electric motor whine is a major NVH source for electric vehicles. Traditional mitigation methods focus on e-motor hardware optimization, which requires long development cycles and may not be easily modified when the hardware is built. This paper presents a control- and software-based strategy to reduce the most dominant motor order of an IPM motor for General Motors’ Ultium electric propulsion system, using the patented active Torque Ripple Cancellation (TRC) technology with harmonic current injection. TRC improves motor NVH directly at the source level by targeting the torque ripple excitations, which are caused by the electromagnetic harmonic forces due to current ripples. Such field forces are actively compensated by superposition of a phase-shifted force of the same spatial order by using of appropriate current.

Edge stretchability reduction induced by mechanical trimming is a critical issue in advanced high strength steel applications. In this study, the tooling effects on the trimmed edge damage were evaluated by the specially designed in-plane hole expansion test with the consideration of three punch geometries (flat, conical, and rooftop), three cutting clearances (6%, 14%, and 20%) and two materials grades (DP980 and DP1180). Two distinct fracture initiation modes were identified with different testing configurations, and the occurrence of each fracture mode depends on the tooling configurations and materials grades. Digital Image Correlations (DIC) measurements indicate the materials are subject to different deformation modes and the various stress conditions, which result in different fracture initiation locations.

The importance of achieving good (low) assembled lateral runout of the brake disc is well recognized in the industry - it is a critical feature for avoiding issues such as wear-induced disc thickness variation and vibration/shudder during braking. Significant efforts and expense has been invested by the industry into reducing disc brake lateral runout. However, wheel assemblies also have some inherent runout, which in turn cause cyclical forces to act on the brake corner during vehicle movement. Despite the stiffness of the wheel bearing (which aligns the brake disc with the caliper and knuckle), these “tire non-uniformity” forces can be sufficient to promote deflection of the assembly that is appreciable compared to typical disc lateral runout tolerances. This paper covers measurements of this phenomenon on three different vehicles (compact, mid-size, and large cars), under a variety of operating conditions such as speed, wheel assembly runout, and wheel assembly balance.

This paper describes the new Honda R&D Americas Scale Model Wind Tunnel (SWT). To help address Honda's ongoing need to improve fuel economy, reduce the driving force of a vehicle, and decrease product development time, the wind tunnel was developed and implemented to achieve high accuracy aerodynamic predictions for product development and a significantly improved capability for vehicle aerodynamics research. The SWT can accommodate model scales up to 50%. The ¾-open jet test section has a top speed of 250 km/h, a 5-belt moving ground plane with a long center belt for proper wake simulation, a test section designed specifically for very low static pressure gradient, three separate dynamic pressure measurement systems for state-of-the-art blockage corrections, and an overhead traverse for specialized measurement activities. This paper describes the decision process that led to the SWT, key commissioning results, and performance validation results with models installed.

The Honda Automotive Laboratories of Ohio (HALO) includes a new aeroacoustic wind tunnel located near Marysville, Ohio that started operations in 2022. This facility provides world-class aerodynamic flow quality and acoustic testing capabilities for the development of both passenger and motorsports vehicles. This closed-return ¾ open jet wind tunnel features a two-position flexible nozzle system with cross sections of 25 m2 and 18 m2, providing wind speeds of up to 250 km/h and 310 km/h, respectively. There is a ±180 degree turntable with boundary layer control systems, and interchangeable single belt and 5-belt moving ground plane (MGP) modules. Extensive applications of acoustic treatment in the test section and throughout the wind tunnel circuit provide a hemi-anechoic test environment and low background noise levels. A temperature control system provides uniform and stable air temperature over an operating environment between 10 °C and 50 °C.

The Ford Motor Company Rolling Road Wind Tunnel (RRWT) is a state-of-the-art aerodynamic wind tunnel test facility in Allen Park, Michigan. The RRWT has operated since January 2022 and is designed for passenger and motorsport vehicle development. The test facility includes an office area, three secure customer vehicle preparation bays, a garage area, a vehicle frontal area measurement system, and a full-scale ¾ open jet wind tunnel. The wind tunnel features an interchangeable single belt and 5-belt Moving Ground Plane (MGP) system with an integrated 6-component balance, a two-position nozzle, boundary layer removal systems, and two independent flow traverse systems. Each flow traverse has a large horizontal box beam and vertical Z-strut that can position the flow traverse accurately within the test volume.

The new BMW Aerodynamisches Versuchszentrum (AVZ) wind tunnel center includes a full-scale wind tunnel, "The BMW Windkanal" and an aerodynamic laboratory "The BMW AEROLAB." The AVZ facility incorporates numerous new technology features that provide design engineers with new tools for aerodynamic optimization of vehicles. The AVZ features a single-belt rolling road in the AEROLAB and a five-belt rolling road in the Windkanal for underbody aerodynamic simulation. Each of these rolling road types has distinct advantages, and BMW will leverage the advantages of each system. The AEROLAB features two overhead traverses that can be configured to study vehicle drafting, and both static and dynamic passing maneuvers. To accurately simulate "on-road" aerodynamic forces, a novel collector/flow stabilizer was developed that produces a very flat axial static pressure distribution. The flat static pressure distribution represents a significant improvement relative to other open jet wind tunnels.

Commercially available Generation 3 (GEN3) advanced high strength steels (AHSS) have inherent capability of replacing press hardened steels (PHS) using cold stamping processes. 980 GEN3 AHSS is a cold stampable steel with 980 MPa minimum tensile strength that exhibits an excellent combination of formability and strength. Hot forming of PHS requires elevated temperatures (> 800°C) to enable complex deep sections. 980 GEN3 AHSS presents similar formability as 590 DP material, allowing engineers to design complex geometries similar to PHS material; however, its cold formability provides implied potential process cost savings in automotive applications. The increase in post-forming yield strength of GEN3 AHSS due to work and bake hardening contributes strongly toward crash performance in energy absorption and intrusion resistance.

Adiabatic heating during plastic straining can slow the diffusionless shear transformation of austenite to martensite in steels that exhibit transformation induced plasticity (TRIP). However, the extent to which the transformation is affected over a strain rate range of relevance to automotive stamping and vehicle impact events is unclear for most third-generation advanced high strength TRIP steels. In this study, an 1180MPa minimum tensile strength TRIP steel with carbide-free bainite is evaluated by measuring the variation of retained austenite volume fraction (RAVF) in fractured tensile specimens with position and strain. This requires a combination of servo-hydraulic load frame instrumented with high speed stereo digital image correlation for measurement of strains and ex-situ synchrotron x-ray diffraction for determination of RAVF in fractured tensile specimens.

The subsystem of front of dash (FOD) and instrument panel (IP) is a critical path to isolate the powertrain noise and road noise for vehicles. This subsystem mainly consists of sheet metal, dash mats, IP, and the components inside IP such as HVAC and wiring harness. To achieve certain level of cabin quietness, the sound transmission loss performance of this subsystem is usually used as a quantifier. In this paper, the sound transmission loss through the FOD and IP is investigated up to 10kHz, through both acoustic testing and numerical simulation. In the acoustic testing, the subsystem is cut from a vehicle and installed on the wall of two-rooms STL testing suite, with source room being reverberant and receiver room being anechoic. In the testing, various scenarios are measured to understand the contributions from different components.

Scania AB has opened the new CD7 climatic wind tunnel test facility, located at the Scania Technical Center in Södertälje, Sweden. This facility is designed for product development testing of heavy trucks and buses in a range of controllable environments. Having this unique test environment at the main development center enables Scania to test its vehicles in a controlled repeatable environment year round, improving lead times from design to production, producing higher quality and more reliable vehicles, and significantly improves the capability for large vehicle performance research. This state-of-the-art facility provides environmental conditions from -35°C to 50°C with humidity control from 5 to 95 percent. The 13 m2 nozzle wind tunnel can produce wind speeds up to 100 km/h. The dynamometer is rated at 800 kW for the rear axle and 150 kW for the front axle, which also has ±10° yaw capability.

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

Prior to making rotational vibration measurements with a laser vibrometer, it is good practice to establish that the instrument is operating properly. This can be accomplished by comparative measurement of a rotational vibration source with known amplitude and frequency. This paper describes the design and development of a rotational vibration apparatus with known amplitude and frequency to be used as a reference for comparison to concurrent and co-located measurements made by a rotational laser vibrometer (RLV). The comparative measurements acquired with the apparatus are helpful to verify proper laser vibrometer operation in between regular calibration intervals, and/or whenever the functionality of the vibrometer is suspect. In the subject apparatus, a Cardan shaft with variable input speed and angle is used to provide output torsional vibration with variable frequency and amplitude.