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SAE International Journal of Passenger Cars Mechanical Systems
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A Study of Low-Frequency and High-Frequency Disc Brake Squeal

SAE International Journal of Passenger Cars - Mechanical Systems

HMC-Jeongkyu Kim
Hyundai Mobis-Wan Gyu Lee, Young Sun Cho
  • Journal Article
  • 2016-01-1944
Published 2016-09-18 by SAE International in United States
When two identical brakes are simultaneously tested on a vehicle chassis dynamometer, very often the left hand brake is found to squeal more or less than the right hand brake, all at different frequencies. This study was performed to develop some understanding of this puzzling phenomenon. It is found that as the wear rate difference between the inner pad and the outer pad increases, low frequency (caliper and knuckle) squeals occur more and more, and as the differential wear becomes larger and larger, high frequency (disc) squeals occur less and less, finally disappearing all together. Discs and calipers are found to affect the differential pad wear, in turn affecting brake squeal generation.
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CVJ and Knuckle Design Optimization to Protect Inboard Wheel Bearing Seals from Splash

SAE International Journal of Passenger Cars - Mechanical Systems

General Motors Corporation-Robert G. Sutherlin, Douglas Reed
  • Journal Article
  • 2016-01-1956
Published 2016-09-18 by SAE International in United States
For higher mileage vehicles, noise from contaminant ingress is one of the largest durability issues for wheel bearings. The mileage that wheel bearing sealing issues increase can vary due to multiple factors, such as the level of corrosion for the vehicle and the mating components around the wheel bearing. In general, sealing issues increase after 20,000 to 30,000 km. Protecting the seals from splash is a key step in extending bearing life. Benchmarking has shown a variety of different brake corner designs to protect the bearing from splash. This report examines the effect of factors from different designs, such as the radial gap between constant velocity joint (CVJ) slinger and the knuckle, knuckle labyrinth height and varying slinger designs to minimize the amount of splash to the bearing inboard seal. This report reviews some of the bearing seal failure modes caused by splash. This study also discusses the test methodology to confirm the robustness of the various designs and provides information on the effectiveness of different features to protect the corner from splash.
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A Multiscale Model of a Disc Brake Including Material and Surface Heterogeneities

SAE International Journal of Passenger Cars - Mechanical Systems

Laboratoire de Mecanique-Jean-Francois Brunel
Laboratoire de Mecanique Trans-Vincent Magnier
  • Journal Article
  • 2016-01-1911
Published 2016-09-18 by SAE International in United States
During friction it is well known that the real contact area is much lower to the theoretical one and that it evolves constantly during braking. It influences drastically the system’s performance. Conversely the system behavior modifies the loading conditions and consequently the contact surface area. This interaction between scales is well-known for the problematic of vibrations induced by friction but also for the thermomechanical behavior. Indeed, it is necessary to develop models combining a fine description of the contact interface and a model of the whole brake system. This is the aim of the present work.A multiscale strategy is propose to integrate the microscopic behavior of the interface in a macroscopic numerical model. Semi-analytical resolution is done on patches at the contact scale while FEM solution with contact parameters embedded the solution at the microscale is used. Asperities and plateaus are considered at the contact interface. FFT techniques are used to accelerate the resolution at the micro-scale. As an example the multiscale model is applied into a complex value analysis used to identify modal coupling…
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The Effect of Outer Ring Flange Concavity on Automotive Wheel Bearings Performance

SAE International Journal of Passenger Cars - Mechanical Systems

ILJIN Global-Seungpyo Lee, Nahyon Lee, Jongkeun Lim, Jungyang Park
  • Journal Article
  • 2016-01-1958
Published 2016-09-18 by SAE International in United States
Through transmitting power and carrying vehicle weight, automotive wheel bearings play an important role. Counterbalancing the bearing responsibilities, they also are designed to last the life of a vehicle without servicing. When mounted to the vehicle steering knuckle by bolts, distortion occurs to the outer ring. Performance is affected when distortion takes place at the seal mounting location and raceways. Finite element analysis using commercial software was performed to analyze the outer ring distortion. Elasto-plastic and contact analyses were carried out to compute the clamping behavior of the outer ring, bolts and the knuckle under various conditions. To verify the reliability of this study, the distortion of the outer ring was measured. The experimental results proved to be comparative with the analysis results.
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Investigation of the Influence of ODE Based Friction Models on Complex FEM Brake Models in the Frequency Domain

SAE International Journal of Passenger Cars - Mechanical Systems

Braunschweig-Aaron Völpel, Georg Peter Ostermeyer
  • Journal Article
  • 2016-01-1931
Published 2016-09-18 by SAE International in United States
In today’s research and development of brake systems the model-based prediction of complex vibrations and NVH phenomena plays an important role. Despite the efforts, the high dimensional computational simulation models only provide a limited part of the results gained through experimental measurements. Several reasons are discussed by the industry and academic research.One potential source of these inadequacies is the very simple formulation of the friction forces in the simulation models. Due to a significant shorter computation time (by orders of magnitude), the complex eigenvalue analysis has been established, in comparison to the transient analysis, as the standard method in the case of industrial research, where systems with more than one million degrees of freedom are simulated. The coefficient of friction in the models is usually assumed to be constant, although it is known that the coefficient of friction is dependent on various system variables like temperature, pressure and velocity. Furthermore, well-known friction phenomena such as time lag behaviour, hysteresis, and the fading effect, can be observed in experimental measurements. For this purpose, new and complex…
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A Study of the Relationship between Leading offset and Squeal Noise

SAE International Journal of Passenger Cars - Mechanical Systems

Mando Co.-Joo Sang Park, Min Gyu Han, Seon Yeol Oh
  • Journal Article
  • 2016-01-1919
Published 2016-09-18 by SAE International in United States
This paper introduces the experimental test results of an investigation to understand the relationship between the leading offset and squeal propensity. In addition Transient Analysis (TA) and Complex Eigenvalue Analysis (CEA) are used simultaneously as a means to compare the experimental approach to two different numerical tools, so evaluating the validity of each theoretical approach. To confirm the CAE results. An ODS was recorded of the brake using a 3D laser scanning vibrometer. Even though the CEA approach is very popular in the study of brake squeal noise, there are some limitations and difficulties in replicating the real phenomenon especially containing unstable behavior. The differences are due to weak pad contact stiffness and friction characteristics which are dependent on the relative interface velocity between pad and rotor. It is necessary to consider stick-slip vibration and time domain analysis in addition. This paper introduces the differences between the transient analysis and the complex eigen-value analysis in their ability to replicate a squeal noise occurrence. There are some analogies between a floating type caliper and an opposed…
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Interactive Effects of Thermal Deformation and Wear on Lateral Runout and Thickness Variation of Brake Disc Rotors

SAE International Journal of Passenger Cars - Mechanical Systems

KIRIU Corporation-Toshikazu Okamura
  • Journal Article
  • 2016-01-1939
Published 2016-09-18 by SAE International in United States
Brake judder is one of the most serious problems in automotive-brake systems. It is basically a forced vibration caused by the friction-surface geometry of a brake disc, and therefore, disc rotors play a significant role in judder. There are two types of judder: cold and hot. Hot judder is caused by the thermo-mechanical deformation of a brake disc due to high-speed braking. There are several shapes of deformation, e.g., coning and circumferential waviness. Circumferential waviness is caused by thermo-mechanical buckling and typically found as a butterfly shape in a 2nd rotational-order and hot-spotting. In a previous paper, two groups of disc castings with different material homogeneity were machined intentionally to have two kinds of dimensional variations. From repetitive high-speed braking tests of these discs, both the material and dimensional homogeneity were found to affect the wave-like deformation of discs in the 1st and 2nd rotational-orders with different significance between the two casting groups. There are many mechanisms affecting disc geometry during braking. Plastic deformation and wear cause permanent effects, while thermal expansion and elastic deformation…
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Development of Advanced Braking System for Hybrid Sports Cars

SAE International Journal of Passenger Cars - Mechanical Systems

Honda R & D Americas, Inc.-Lorne R. Dyar, Yuichiro Akita, Scott Paul, Joseph Lepito, Yoshio Ishikawa, Tomohiro Watanabe
  • Journal Article
  • 2016-01-1923
Published 2016-09-18 by SAE International in United States
An advanced braking system had to be developed for a next-generation hybrid sports car with Sport Hybrid Super Handling All-Wheel Drive to achieve an intuitive brake feeling in a variety of driving conditions, ultimate track performance and reduction of CO2 emissions per vehicle. This paper outlines the integration of brake-by-wire with traditional high-performance braking hardware and describes the technology needed to achieve these goals. Key focus areas to generate these results were: brake feeling control, corner hardware specification considerations and brake cooling.
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Friction Coefficient Variation Mechanism under Wet Condition in Disk Brake (Variation Mechanism Contributing Wet Wear Debris)

SAE International Journal of Passenger Cars - Mechanical Systems

ADVICS Co. Ltd.-Satoshi Wakamatsu, Katsuya Okayama, Kyoko Kosaka
Toyota Central R&D Labs Inc.-Tadayoshi Matsumori, Yoshitsugu Goto, Noboru Sugiura
  • Journal Article
  • 2016-01-1943
Published 2016-09-18 by SAE International in United States
This paper deals with friction under wet condition in the disk brake system of automobiles. In our previous study, the variation of friction coefficient μ was observed under wet condition. And it was experimentally found that μ becomes high when wear debris contains little moisture. Based on the result, in this paper, we propose a hypothesis that agglomerates composed of the wet wear debris induce the μ variation as the agglomerates are jammed in the gaps between the friction surfaces of a brake pad and a disk rotor. For supporting the hypothesis, firstly, we measure the friction property of the wet wear debris, and confirm that the capillary force under the pendular state is a factor contributing to the μ variation. After that, we simulate the wear debris behavior with or without the capillary force using the particle-based simulation. We prepare the simulation model for the friction surfaces which contribute to the friction force through the wear debris. The simulation results support our hypothesis, that is, under the wet condition assuming the pendular state, the…
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New Developments of an On-Vehicle Brake Pad Waste Collection System

SAE International Journal of Passenger Cars - Mechanical Systems

Brake Pad Waste Collection Systems Inc.-Joe Gelb
JDF Consulting-John David Fieldhouse
  • Journal Article
  • 2016-01-1949
Published 2016-09-18 by SAE International in United States
The design of a braking system involves a delicate balance between the friction pair, the disc and pad, where the pad is a complex blend of constituents to provide predictable characteristics, typically, a known and consistent friction level. In its base form the brake has to absorb the vehicle kinetic energy by converting it into heat. This heat absorption by the friction pair can result in chemical and physical interactions with the release of debris about which we know little. Other than environmental concerns, brake dust causes unnecessary problems with wear, thermal gradients (hot banding) and NVH. This paper is concerned with the removal and collection of brake debris from the friction interface - the debris being regarded as solids and airborne particles, the latter less than 10μm in size. The test procedure consisted of a Burnish program followed by 8 different drive cycles. The overall effects of debris removal is then reported for each test. It will be shown that, by careful design of air circulation within a collection system, over 92% of dust…
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