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Journal Article

Vehicle and Occupant Responses in a Friction Trip Rollover Test

Objective: A friction rollover test was conducted as part of a rollover sensing project. This study evaluates vehicle and occupant responses in the test. Methods: A flat dolly carried a Saab 9-3 sedan laterally, passenger-side leading to a release point at 42 km/h (26 mph) onto a high-friction surface. The vehicle was equipped with roll, pitch and yaw gyros near the center of gravity. Accelerometers were placed at the vehicle center tunnel, A-pillar near the roof, B-pillar near the sill, suspension sub-frame and wheels. Five off-board and two on-board cameras recorded kinematics. Hybrid III dummies were instrumented for head and chest acceleration and upper neck force and moment. Belt loads were measured. Results: The vehicle release caused the tires and then wheel rims to skid on the high-friction surface. The trip involved roll angular velocities >300 deg/s at 0.5 s and a far-side impact on the driver’s side roof at 0.94 s. The driver was inverted in the far-side, ground impact.
Technical Paper

Rear-Seat Occupant Responses in NHTSA Rear Crash Tests

This study analyzed FMVSS 301 rear impact tests with an instrumented rear-seat dummy. NHTSA conducted 15 FMVSS 301 rear crash tests with an instrumented and belted 50th Hybrid III dummy in the rear seat. In series 1, there were three repeat tests with the Jeep Liberty and two others, but no onboard camera view. In series 2, there were 8 tests with 2003-2005 MY (model year) vehicles that had rear head restraints. In series 3, there were two tests with 2004-2005 MY vehicles that did not have rear head restraints. There was an onboard camera view of the rear occupant in series 2 and 3. The dummy responses were evaluated and compared to relevant IARVs (injury assessment reference values). Based on the HRMD, the average height of the rear head restraints was 80.4 ± 3.4 cm (31.6″ ± 1.3″) above the H-point. In series 1, the delta V was 24.4 ± 2.0 km/h (15.2 ± 1.3 mph).
Technical Paper

Abdominal Injuries in Frontal Crashes: Influence of Occupant Age and Seating Position

Objective: This study investigated the incidence of abdominal injuries in frontal crashes by occupant age and seating position. It determined the risk for abdominal injury (AIS 2+) by organ and injury source. Methods: 1997-2015 NASS-CDS was analyzed to estimate the occurrence of abdominal injuries in non-ejected, belted occupants involved in frontal crashes. Vehicles were included with 1997+ model year (MY). The annual incidence and rate for different types of abdominal injury were estimated with standard errors. The sources for abdominal injury were determined. Results: 77.8% of occupants were drivers, 16.7% were right-front passengers and 5.4% were rear passengers. Rear passengers accounted for 77.1% of 8-11 year old (yo) and 17.2% of 12-17 yo group. The risk for moderate abdominal injury (MAIS 2 + abdo) was 0.30% ± 0.053% in drivers, 0.32% ± 0.086% in right-front passengers and 0.38% ± 0.063% in rear occupants.
Technical Paper

Bolster Impacts to the Knee and Tibia of Human Cadavers and an Anthropomorphic Dummy

Knee bolsters on the lower instrument panel have been designed to control occupant kinematics during sudden deceleration. However, a wide variability in car occupant anthropometry and choice of seating posture indicates that lower-extremity contacts with the impingement bolster could predominantly load the flexed leg through the knee (acting through the femur) or through the tibia (acting through the knee joint). Potential injuries associated with these types of primary loading may vary significantly and an understanding of potential trauma mechanisms is important for proper occupant restraint.
Technical Paper

Factors Influencing Knee Restraint

A planar mathematical model was developed to provide means of studying factors which can influence the function of lower torso restraint via a padded lower instrument panel or knee bolster. The following factors were judged to play the most significant role: 1) initial fore-and-aft position of the seated occupant relative to the knee restraint; 2) location of the knee-to-bolster contact; 3) angular orientation of the bolster face; 4) primary axis of the bolster resisting force, 5) variations in vehicle crash parameters (e.g., toepan rotation and displacement and seat deflection); and 6) deformation characteristics of the bolster. The model of a seated occupant included radiographic and empirical data on the anatomy of the links and joints in the lower extremity.
Technical Paper

Measurement of Head Dynamics and Facial Contact Forces In the Hybrid III Dummy

Injury and disability associated with head (brain), neck (spinal cord) and facial injury account for 61.7% of the total societal Harm in the most recent estimate of motor-vehicle related crash injuries. This paper discusses the need for accurate information on translational and rotational acceleration of the head as the first step in critiquing the Head Injury Criterion (HIC) and other injury predictive methods, and developing a fuller understanding of brain and spinal cord injury mechanisms. A measurement system has been developed using linear accelerometers to accurately determine the 3D translational and rotational acceleration of the Hybrid III dummy head. Our concept has been to use the conventional triaxial accelerometer in the dummy's head to assess translational acceleration, and three rows of in-line linear accelerometers and a least squares analysis to compute statistical best-fits for the rotational acceleration about three orthogonal axes.
Technical Paper

Evaluation of the SID Dummy and TTI Injury Criterion for Side impact Testing

The NHTSA's side impact dummy (SID) was evaluated against what is known of the side impact response of the human chest and responses were compared with data on Hybrid III frontal and EURQSID side impact characteristics. The SID dummy lacks a human-like chest deflection response which is crucial to the injury indicating capability of a dummy, it has a 9.8 kg near-side rib mass which is approximately an order of magnitude greater than that of the human, and it develops impact forces that are nearly three times higher than the recommended human chest response. It possesses characteristics primarily of an inertial device. The thoracic trauma index (TTI) was evaluated as an indicator of side impact injury risk, and design trends and optimized padding characteristics identified with the SID and TTI were compared with those from the Hybrid III dummy and viscous or compression injury criteria.
Technical Paper

Influence of Seatback Angle on Occupant Dynamics in Simulated Rear-End Impacts

In the early 1980's a series of tests was conducted simulating rear-end crashes. The tests demonstrated that a conventional automotive bucket seat adequately retains an unbelted dummy on the seat for rear-end impacts up to 6.4 m/s and 9.5 g severity. For this severity of impact the total rearward rotation of the seatback is less than 60° from the vertical and is associated with a normal acceleration of the dummy's chest into the seatback of up to 10 g. The tangential acceleration of the dummy, which may induce riding up the seat, was generally less than the normal component so that the occupant was prevented from sliding up the deflected seatback. The bucket seat provided adequate containment and control of occupant displacements for each of the initial seatback angles of 9°, 22°, and 35°.
Technical Paper

Biomechanics of Head Injury — Toward a Theory Linking Head Dynamic Motion, Brain Tissue Deformation and Neural Trauma

A “central” theory for the biomechanics of brain injury is proposed that includes the construct that acceleration of the head, per se, is not the proximate cause of injury. Rather, rapid motion of the skull causes displacement of the hard bony structures of the head against the soft tissues of the brain, which lag in their motion due to inertia and loose coupling to the skull. Relative displacement between brain and skull produces deformation of brain tissue and stretching of bridging veins, which contribute to the tissue-level causes of brain injury. The first step in an accurate interpretation of brain injury risk in dummies involves the measurement of the three-dimensional components of translational and rotational acceleration of the head.
Technical Paper

Thoracic Impact: New Experimental Approaches Leading to Model Synthesis

The following work was done in support of a continuing program to better characterize the behavior of the human chest during blunt sternal impact. Previous work on this problem has focused on determining the force-time, deflection-time, and force-deflection response of embalmed and fresh cadavers to impact by a 15 cm (6 in) diameter striker of variable mass traveling at velocities of 22.5-51 km/h (14-32 mph) and striking the sternum at the level of the fourth intercostal space. Additional questions persist concerning whether the anterior and posterior regions of the chest behave as highly damped masses or oscillate after impact, the relationship between force delivered to the surface of the body and the acceleration of the underlying regions, and the influence of air compressed in the lung on thoracic mechanics.
Technical Paper

Thoracic Impact Response of Live Porcine Subjects

Five anesthetized porcine subjects were exposed to blunt thoracic impact using a 21 kg mass with a flat contact surface traveling at 3.0 to 12.2 m/s. The experiments were conducted to assess the appropriateness of studying in vivo mechanical and physiological response to thoracic impact in a porcine animal model. A comprehensive review of comparative anatomy between the pig and man indicates that the cardiovascular, respiratory and thoracic skeletal systems of the pig are anatomically and functionally a good parallel of similar structures in man. Thoracic anthropometry measurements document that the chest of a 50 to 60 kg pig is similar to the 50th percentile adult male human, but is narrower and deeper. Peak applied force and chest deflection are in good agreement between the animal's responses and similar impact severity data on fresh cadavers.
Technical Paper

Influence of Initial Length of Lap-Shoulder Belt on Occupant Dynamics-A Comparison of Sled Testing and MVMA–2D Modeling

The primary purpose of this parameter study was to carefully document occupant dynamics in well-controlled sled tests for comparison with simulated responses from the MVMA-2D analytical model. The test involved a Part 572 dummy exposed to a frontal deceleration while on a bucket seat and restrained by a lap-shoulder belt system. The length of belt webbing was incrementally increased from a snug configuration by as much as 30 cm. The addition of webbing increased the forward excursion, velocity, and acceleration of the head, chest, and hip without affecting the peak tension in the belt segments of the restraint system. Belt tension was identified as a poor measure of the horizontal load on the chest due to significant reaction forces in the lateral and vertical direction at the belt anchorages.
Technical Paper

Test Dummy Interaction with a Shoulder or Lap Belt

Belt interaction with the dummy's chest or pelvis was investigated during simulated frontal decelerations to develop a better understanding of the mechanics of belt restraint. Hyge sled tests were conducted at acceleration levels of 6-16 g's with a Part 572 dummy forward facing on an automotive bucket seat. Dynamics were compared in similar tests where the dummy was restrained by a conventional shoulder belt or belt segments attached to a modified sternum - a steel sternum with extensions for fixed belt attachments. Tests were also conducted with a conventional lap belt or belt segments fixed to an extension of the H point. Deformation characteristics of the standard and modified thorax were determined for a lateral and superior point load or a belt yoke compression of the sternum. The pelvic structure was also compressed by a lap belt. Our evaluation of test dummy dynamics indicates the following sequence of events with a conventional shoulder belt: 1.)
Technical Paper

Interrelationship of Velocity and Chest Compression in Blunt Thoracic Impact to Swine

As part of a continuing study of thoracic injury resulting from blunt frontal loading, the interrelationship of velocity and chest compression was investigated in a series of animal experiments. Anesthetized male swine were suspended in their natural posture and subjected to midsternal, ventrodorsad impact. Twelve animals were struck at a velocity of 14.5 ± 0.9 m/s and experienced a controlled thoracic compression of either 15, 19, or 24%. Six others were impacted at 9.7 ± 1.3 m/s with a greater mean compression of 27%. For the 14.5 m/s exposures the severity of trauma increased with increasing compression, ranging from minor to fatal. Injuries included skeletal fractures, pulmonary contusions, and cardiovascular ruptures leading to tamponade and hemothorax. Serious cardiac arrhythmias also occurred, including one case of lethal ventricular fibrillation. The 9.7 m/s exposures produced mainly pulmonary contusion, ranging in severity from moderate to critical.
Technical Paper

Neck Biomechanical Responses with Active Head Restraints: Rear Barrier Tests with BioRID and Sled Tests with Hybrid III

Active head restraints are being used to reduce the risk of whiplash in rear crashes. However, their evaluation in laboratory tests can vary depending on the injury criteria and test dummy. The objective of this study was to conduct barrier tests with BioRID and sled tests with Hybrid III to determine the most meaningful responses related to whiplash risks in real-world crashes. This study involved: (1) twenty-four rear barrier tests of the Saab 9000, 900, 9-3 and 9-5 with two fully instrumented BioRID dummies placed in the front or rear seats and exposed to 24 and 48.3 km/h barrier impacts, and (2) twenty rear sled tests at 5-38 km/h delta V in three series with conventional, modified and SAHR seats using the Hybrid III dummy. A new target superposition method was used to track head displacement and rotation with respect to T1. Insurance data on whiplash claims was compared to the dummy responses.
Technical Paper

Biofidelity and Injury Assessment in Eurosid I and Biosid

Side impact pendulum tests were conducted on Eurosid I and Biosid to assess the biofidelity of the thorax, abdomen and pelvis, and determine injury tolerance levels. Each body region was impacted at 4.5, 6.7, and 9.4 m/s using test conditions which duplicate cadaver impacts with a 15 cm flat-circular 23.4 kg rigid mass. The cadaver database establishes human response and injury risk assessment in side impact. Both dummies showed better biofidelity when compared to the lowest-speed cadaver response corridor. At higher speeds, peak force was substantially higher. The average peak contact force was 1.56 times greater in Biosid and 2.19 times greater in Eurosid 1 than the average cadaver response. The Eurosid I abdomen had the most dissimilar response and lacks biofidelity. Overall, Biosid has better biofidelity than Eurosid I with an average 21% lower peak load and a closer match to the duration of cadaver impact responses for the three body regions.
Technical Paper

Finite Element Simulation Study of a Frontal Driver Airbag Deployment for Out-Of-Position Situations

As more and more active restraint devices are added by vehicle manufacturers for occupant protection, the history of driver frontal airbags illustrates that the design performance of such devices for in-position (IP) occupants often have to be limited in order to reduce their aggressiveness for out-of-position (OOP) situations. As of today, a limited number of publications dealing with FE simulation of airbag deployment for OOP are available. The objective of our study was to evaluate the feasibility of airbag deployment simulations based on an extensive set of well-defined physical test matrix. A driver frontal airbag was chosen (European mid-size car sample) for this study. It was deployed against a force plate (14 tests in a total of 6 configurations), and used with Hybrid III 50th percentile dummy (HIII) in OOP tests (6 tests, 4 configurations). Special attention was paid to control the boundary conditions used in experiments in order to improve the modelling process.
Journal Article

Basilar Skull Fractures by Crash Type and Injury Source

Purpose: This study investigates NASS-CDS data on basilar skull fractures by crash type and injury source for various crash scenarios to understand the injury risks, injury mechanisms and contact sources. Methods: 1993-2008 NASS-CDS data was used to study basilar skull fractures in adult front occupants by crash type and injury source. Injury risks were determined using weighted data for occupants with known injury status in 1994+ model year vehicles. In-depth analysis was made of far-side occupants in side impacts and rear crashes using the NASS electronic cases. Results: Basilar skull fractures occur in 0.507 ± 0.059% of rollovers and 0.255 ± 0.025% of side impacts. The lowest risk is in rear impacts at 0.015 ± 0.007%. The most common contact source is the roof, side rails and header (39.0%) in rollovers, the B-pillar (25.8%) in side impacts and head restraint (55.3%) in rear crashes.
Technical Paper

Assessment of Air Bag Deployment Loads

A study of air bag deployments has indicated that some occupant injury was “unexpected” and might have been related to loading by the inflating bag. Laboratory studies have found “high” loads on surrogates when they are out of a normal seating position and in the path and against an inflating air bag (out-of-position). The current study evaluated laboratory methods for assessing the significance of deployment loads and the interaction mechanics for the situation of an occupant located near or against a steering wheel mounted air bag. Analysis of the field relevance of the results must consider not only factors relating to the assessment of injury risk, but also exposure frequency. The highest responses for the head, neck, or torso were with that body region aligned with and against the air bag module. The risk of severe injury was low for the head and neck, but high when the torso was against and fully covering the air bag module.
Technical Paper

Assessing the Safety Performance of Occupant Restraint Systems

The purpose of this study was to investigate approaches evaluating the performance of safety systems in crash tests and by analytical simulations. The study was motivated by the need to consider the adequacy of injury criteria and tolerance levels in FMVSS 208 measuring safety performance of restraint systems and supplements. The study also focused on additional biomechanical criteria and performance measures which may augment FMVSS 208 criteria and alternative ways to evaluate dummy responses rather than by comparison to a tolerance level. Additional analysis was conducted of dummy responses from barrier crash and sled tests to gain further information on the performance of restraint systems. The analysis resulted in a new computer program which determined several motion and velocity criteria from measurements made in crash tests.