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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.

Epidemiological and clinical studies have identified the cervical facet capsule as a potential site of whiplash injury and prerotation of the head and neck as a risk factor for whiplash injury. However, biomechanical data related to the cervical facet capsule and its role in whiplash injury remain limited in the literature. In this study, cervical spine motion segments were tested in a pure moment test frame and the full field strains were determined throughout the facet capsule. Motion segments were tested with and without a pretorque in pure bending. Bending tests were followed by isolated facet elongation tests to failure. Maximum principal strains during bending were compared to failure strains. Statistically significant increases in principal capsular strains were observed in the facet which was contralateral to the pretorque. In contrast, no significant differences were present in the ipsilateral facet when large flexion-extension moments were applied.

Several investigators have noted limitations of the most commonly used dummy in rear impact testing, the Hybrid III. A dummy for rear impact testing, the BioRID I, has previously been presented. It was a step towards an effective tool for seat performance testing, but it was concluded that its neck extension and T1 upward motion were too small and that its user- friendliness could be improved. A new BioRID prototype has been developed. It has new neck muscle substitutes with damping and elastic elements that are independent of each other and fitted inside the torso. The new neck muscle substitutes extend to T3 and thus also load the upper thoracic spine. The new dummy has a softer thoracic spine and a torso made of softer rubber than was used for the original dummy. The BioRID prototype''s performance was compared to that of volunteers, the BioRID I and Hybrid III in rear impacts at ΔV=7 km/h.

A BioRID (biofidelic rear impact dummy) representing a 50th percentile adult male was seated in the front passenger seat of six new vehicle models in a series of low-speed crash tests. The neck injury criterion (NIC) and other dummy responses that may indicate whiplash injury risk were recorded. Both front-into- rear and rear-into-barrier tests with an average velocity change of 11 km/h were conducted. Head restraints were tested in both adjusted (up) and unadjusted (down) positions. Damage to all models was minor, and longitudinal vehicle accelerations were low (less than 7 g). Neck extension angles and bending moments were much less than injury assessment reference values (IARV) (80 degrees and 57 Nm, respectively), indicating low risk of hyperextension injuries. Neck tension and transverse forces also were less than IARVs used to indicate the risk of more serious neck injuries.

In a previous study by Demetropoules et al., (1998), it was shown that both cadaveric and Hybrid III lumbar spines exhibit loading rate dependency when loaded in a quasi-static mode up to a velocity of 100 mm/s. In these tests, the Hybrid III lumbar spines were generally found to have higher stiffnesses than the human lumbar spines, except in compression. This is probably due to the fact that muscle loading was not simulated when testing the human spines. Additionally, the speed previously used to test the spines was less than that typically seen in automotive crash environment. The purpose of this study was to use a high-rate testing machine to establish the flexion and extension stiffnesses of the human lumbar spine with simulated extensor muscle tone. Two Hybrid III lumbar spines were used to develop the test methodology and to obtain the response of the Hybrid III lumbar spines.

In vivo, tissue-level, mechanical thresholds for axonal injury in the guinea pig optic nerve were determined by comparing morphological injury to estimated in vivo tissue strain. The right optic nerve of adult male guinea pigs was stretched to one of seven ocular displacement levels. Morphological injury was detected three days post-stretch with neurofilament immunohistochemical staining (NF68). A companion set of in situ experiments was used to determine the empirical relationship between ocular displacement and optic nerve stretch. Logistics regression analysis, combined with sensitivity and specificity measures and receiver operating characteristic (ROC) curves were then used to predict strain thresholds for axonal injury. From this analysis, we determined three Lagrangian strain- based thresholds for morphological damage to the guinea pig white matter.

Validating a traumatic brain injury finite element model is often limited by a lack of extensive animal injury data that may be used to examine the conditions under which the model is accurate. Given that most published reports specify only general descriptions of injury, this study examined potential evaluation strategies and assessed the ability of a finite element model to simulate the general descriptions of injury in an animal model. The results of this study showed that 1) the results from a simplified finite element model could estimate trends that were similar to the injury patterns observed in a set of animal experiments, 2) a parameter (Z parameter), which quantified the comparison process between computational and animal data, estimated trends that would help in the model evaluation process, and 3) a more complete evaluation process would occur if multiple testing methods were included in the evaluation procedure.