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The disc brake pad is a part that is expected to exert the stable performance in a wide variety of working conditions, for example, in a wide speed range and in a wide temperature range. In addition to these working conditions, the stable performance in a variety of humid conditions has also been demanded. This is because most non-asbestos brake pads have the low friction coefficient μ in high humid conditions, which affects the performance of the disc brake pad. This study notes the film of the friction material on the disc rotor as the reason of a decrease in friction coefficient μ in the high humid environment and discusses the mechanism of the decrease in friction coefficient μ.

Brake pad and disc wear is a significant factor in determining the maintenance intervals for motor vehicles. The ability to improve pad and disc life and thereby increase maintenance intervals requires fundamental studies of new and advanced friction pairs. Wear is essentially influenced by two factors, the friction power acting at the contact surfaces, which is in turn a function of brake pressure, friction coefficient and driving speed, and the temperature at the friction surface. A model has been developed describing the wear process and consising of four interlinked modules: a module describing the driving dynamics; a structural mechanical module describing the contact situation between pad and disc; a thermomechanical module representing the thermal conduction in pad and disc, and a law of wear. Based on wear values experimentally determined on a dynamometer, the model predicts the wear of a friction pair during a vehicle endurance run.

This paper documents the advantages of brake corner system modeling and simulation over traditional component analysis techniques. A better understanding of the mechanical dynamics of the disc-braking event has been gained through brake corner system modeling and simulation. Single component analyses do not consider the load transfer between components during the braking event. Brake corner system analysis clearly quantifies the internal load path and load transfer sequence between components due to clearances or tolerance variations in the brake assembly. By modeling the complete brake corner assembly, the interaction between components due to the contact friction loads and variational boundary conditions can be determined. The end result permits optimal design of brake corner systems having less deflection, lower stress, optimum material mass, and reduced lead-time for new designs.

Hayes Lemmerz has published papers (Ref 1 and 2 ) where different rotor designs were investigated to increase airflow velocity. We also have published the dynamometer test's data to show the 100 degrees F drop in temperature and 50% drop in deformation in rotors with 5% increase in airflow velocity (Ref 3). In the previous paper (Ref 4), the increase of 37.2% of airflow velocity in a 72 curved fin rotor design, was shown. In this paper, we are showing the results of dynamometer testing the 72 curved fin rotor design. When the 72 curve fin rotor design is compared to current production design, the 72 curve fin rotor design shows, a 140° F (60° C) drop in temperature during heating and cooling cycles. Hayes Lemmerz is testing this rotor design on standard vehicle tests ( LACT and DST). The results of these tests would be presented in another paper.

Automotive wheel speed sensors have generally been based on principles of magnetic field sensing. “Active” sensors, as Hall and Magneto-Resistive, overcome some drawbacks of the previous systems. However, recent conceptual advancements, focusing on the tone-wheel, have proved significant for system performance. The tone-wheel is replaced in fully active systems by a precise ring of steel, bonded to magnetized rubber, where multiple poles are produced in the circumference. The ring serves as an encoder for magnetic sensors, eliminating the need for a large, strong permanent magnet on the sensor - thus significantly reducing size. Active sensor and encoder allow detectable speeds down to zero, improved accuracy, and significantly larger air-gaps and allowable tolerances. These properties, in turn, provide major advantages in manufacture and assembly costs. Usage of elastomeric compounds provides excellent mechanical, dynamic and environmental behavior.

Creep-groan in vehicles is a low frequency vibration problem that occurs at low brake pressures and extremely low speeds. Noise, Vibration and Harshness (NVH) problems in brakes in general and creep-groan in particular manifest in different forms. Creep-groan is an example of self-excited vibration caused by stick-slip phenomenon. Most researchers to date have been concentrating on the characteristics between the friction material and the contacting surfaces and its effect on creep-groan vibration. This paper, instead, describes creep-groan and its relationship to vehicle dynamics by looking at the suspension response to creep-groan and presents a solution to reduce effects due to creep-groan vibrations.

This paper demonstrates that the time-domain average of coefficient of friction (COF) widely in use today does not serve as a reliable indication of a system's braking capability. For a given braking system, it may lead to large error in predicted stopping distance. When used in lining selection, it may lead to incorrect ranking of various linings' friction level. A new method for calculating the average of friction coefficient is proposed and compared with the time-domain average COF. A detailed error analysis is given for two special cases.

A new NVH matrix for brake noise test rigs is presented which combines the specifications of the European drag mode test developed by the AK Noise (‘Arbeitskreis Geräusch’) with US-American in-stop tests. Additionally parts, of the AK Master lining selection dynamometer program are included in the proposed procedure to correlate friction and noise. The NVH matrix has been assigned a SAE concept number J 2521. To aid data evaluation and correlation of dynamometer and vehicle results, a post-processing system has been developed offering high flexibility and fast data visualization.

In this paper, a brake damper is modeled with the finite element method to predict its response in a free-free impact modal test. A multi-layer representation of a brake shim is described which captures the dynamic characteristics of a damper, bonded to a brake shoe and lining. Calculations of damping values and natural frequencies are compared to impact modal test results over a wide temperature range. It was found that the finite element model accurately predicts the results from the experiment. A discussion is also given on how the model may be used to develop a material database and automation of the modeling process to analyze any layered brake damper.

A simple finite element model for the pads, caliper and mounting of a car disc brake system is built and its dynamic influence to the disc is established. The disc is modeled as a thin plate in sliding contact with the pads. Through the contact conditions, the dynamics of the whole disc brake system is formulated. The friction-induced instability of the disc brake system is analyzed for different system parameters and operating conditions so that their influences on the dynamic instability and squeal are understood. Numerical simulation indicates that in the specific cases considered reasonably stiff pads tend to reduce the likelihood of squeal.

The mode of vibration of a noisy disc brake is always diametral with a noise frequency marginally less than the free mode of vibration of the disc. Wheel speed does not affect the frequency but if brake pressure is altered then the noise frequency changes accordingly - an increasing pressure resulting in an increasing frequency over a specified range. Such observations have been made of a variety of different disc brake designs from single piston sliding fist type callipers to four piston opposed rigid callipers with it being possible to relate the noise frequency to the free mode of vibration of the disc in all cases. If the characteristics controlling this behaviour can be identified then the same principles and criteria may be used to predict the noise propensity of any brake at the design stage. The paper proposes, and shows, that the preferred frequencies of excitation of any disc brake system may be related directly to the free mode frequency of the disc.

The UK in-depth data, describing the causation of injuries to casualties in side impacts, was examined for crashes occurring between 1992 and 1998. Slightly more casualties died in side impacts than in frontal crashes, and one-third were seated on the side away from the collision. The collision severity was compared with the European and US legal test procedures and most MAIS 3+ survivors were observed to be in crashes above the severity of the test. The mean delta-V for the fatal group was 48 km/h compared with typically 25 km/h in the test. The most commonly injured body regions of both survivors and fatalities were the head, thorax and lower extremity. The lower extremity was the most frequent site of AIS 2+ injuries of survivors and fractures to the femur and tibia were highlighted, these injuries are not assessed by existing dummies.

Linear viscoelastic material parameters of porcine brain tissue and two brain substitute materials for use in mechanical head models (edible bone gelatin and dielectric silicone gel) were determined in small deformation, oscillatory shear experiments. Frequencies to 1000 Hertz could be obtained using the Time/Temperature Superposition principle. Brain tissue material parameters (i.e., dynamic modulus (phase angle) of 500 (10°) and 1250 Pa (27°) at 0.1 and 260 Hz, respectively) are within the range of data reported in literature. The gelatin behaves much stiffer (modulus on the order of 100 kPa) and does not show viscous behavior. Silicone gel resembles brain tissue at low frequencies but becomes more stiffer and more viscous at higher frequencies (dynamic modulus (phase angle) 245 Pa (7°) and 5100 Pa (56°) at 0.1 and 260 Hz, respectively).

Relative motion between the brain and skull may explain many types of brain injury such as intracerebral hematomas due to bridging veins rupture [1] and cerebral contusions. However, no experimental methods have been developed to measure the magnitude of this motion. Consequently, relative motion between the brain and skull predicted by analytical tools has never been validated. In this study, radio opaque markers were placed in the skull and neutral density markers were placed in the brain in two vertical columns in the occipitoparietal and temporoparietal regions. A bi-planar, high-speed x-ray system was used to track the motion of these markers. Due to limitations in current technology to record the x-ray image on high-speed video cameras, only low- speed (﹤ 4m/s) impact data were available.

Head injury is the most common cause of death and acquired disability in childhood. We seek to determine the influence of brain mechanical properties on inertial pediatric brain injury. Large deformation material properties of porcine pediatric and adult brain tissue were measured and represented by a first-order Ogden hyperelastic viscoelastic constitutive model. A 3-D finite element mesh was created of a mid-coronal slice of the brain and skull of a human adult and child (2 weeks old). Three finite element models were constructed: (1) a pediatric mesh with pediatric brain properties, (2) a pediatric mesh with adult tissue properties, and (3) an adult mesh with adult tissue properties. The skull was modeled as a rigid solid and an angular acceleration was applied in the coronal plane with center at C4/C5. The brain is assumed to be homogeneous and isotropic.

This work describes the development of a three-dimensional finite element model of the human arm. Mechanical properties of the arm were determined experimentally for use in the model development. The arm model is capable of predicting kinematics and potential injury when interacting with a deploying airbag. The arm model can be easily integrated with available finite element and rigid body dummy models. This model includes the primary components of a human arm. It includes all the bones of hand, ulna, radius and humerus. Anthropometry, moment of inertia, joint torque and tissue compressive properties were determined experimentally from human cadaveric subjects. To calibrate the model, both free-swinging motion and pendulum impact tests were used. The global responses of the pendulum force, pendulum velocity and the angle of rotation time histories of the arm were obtained and compared reasonably well with the experimental data.

All air bag systems use a pyrotechnic combustion process for the generation of gases. In some systems, it is also used for the heating of stored gases to quickly inflate the air bag. As a by-product of the process, gases and particles are produced that enter the passenger compartment resulting in inhalation of these substances. We have previously shown that systems using sodium azide as the gas generant can initiate asthmatic attacks in susceptible individuals. To evaluate whether the effluents from new-generation, non-azide air bag systems also have the potential to produce adverse responses, we performed controlled exposures of mild to moderate asthmatics to the effluents from six of these air bag systems. Each volunteer asthmatic subject was pulmonary function tested (baseline), and then seated in the back seat of the test vehicle. The air bag system was deployed and the subjects remained in the vehicle for twenty minutes.

A case-comparison study was conducted of children between one and twelve years of age exposed to passenger air bag (PAB) deployment. Cases were children fatally injured by PAB exposure and were investigated by the Special Crash Investigation Program of NHTSA. For comparison, children exposed to PABs, but suffering minor injury were identified through the Partners for Child Passenger Safety (PCPS) Study, a system utilizing insurance claims data for crashes involving children. The crash severity as measured by Delta V was not significantly different between the two groups. Restraint status in conjunction with pre-impact braking highly influenced injury outcome indicating the importance of pre-crash positioning as a risk factor in child exposure to PAB deployment. Other related variables such as child size and age reinforced the importance of restraint. No vehicle characteristics or interior vehicle space measurements were significantly different between the two groups.

It has been reported that lower extremity injuries represent a measurable portion of all moderate-to-severe automobile crash- related injuries. Thus, a simple tool to assist with the design of leg and foot injury countermeasures is desirable. The objective of this study is to develop a mathematical model which can predict load propagation and kinematics of the foot and leg in frontal automotive impacts. A multi-body model developed at the University of Virginia and validated for blunt impact to the whole foot has been used as basis for the current work. This model includes representations of the tibia, fibula, talus, hindfoot, midfoot and forefoot bones. Additionally, the model provides a means for tensioning the Achilles tendon. In the current study, the simulations conducted correspond to tests performed by the Transport Research Laboratory and the University of Nottingham on knee-amputated cadaver specimens.

A significant number of documented ankle injuries incurred in automobile accidents indicate some form of lateral loading is present to either cause or influence injury. A high percentage of these cases occur in the absence of occupant compartment intrusion. To date, no specific ankle injury mechanism has been identified to explain these types of injuries. To investigate this problem, several resources were used including full-scale crash test data, finite element models, and case study field data. Results from car-to-car, offset frontal crash tests indicate a significant lateral acceleration (10-18 g) occurs at the same time as the peak in longitudinal acceleration. The combined loading condition results in a significant lateral force being applied to the foot-ankle region while the leg region is under maximum compression.