Search Results

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.

A series of twenty-nine tests was completed by conducting static deployment of side airbag systems to an out-of-position Hybrid III three-year-old dummy. Mock-ups (bucks) of vehicle occupant compartments were constructed. The dummy was placed in one of four possible positions for both door- and seat-mounted side airbag systems. When data from each type of position test were combined for the various injury parameters it was noted that the head injury criteria (HIC) were maximized for head and neck tests, and the chest injury parameters were maximized for the chest tests. For the neck injury parameters, however, all of the test positions produced high values for at least one of the parameters. The study concluded the following. Static out-of- position child dummy side airbag testing is one possible method to evaluate the potential for injury for worst-case scenarios. The outcome of these tests are sensitive to preposition and various measurements should be made to reproduce the tests.

This paper describes the development and validation of a finite element model of the SID-IIs beta+-prototype dummy using a nonlinear explicit finite element code. The geometry of the SID-IIs dummy is modeled with shell and solid elements from digital scans. The material properties are derived from dynamic tests and the model validation is conducted on component, subassembly and full assembly levels. Component level validation of the head/neck, arm, ribs, and lumbar spine is presented. The model validation of the thorax and pelvis subassemblies as well as pendulum calibration tests (shoulder, thorax, abdomen, and pelvis) and rigid-wall sled tests of the fully assembled dummy mode is also presented. The model response compares favorably with experimental data and provides a reasonable level of confidence in the model biofidelity.

The purpose of this study is to help understand the thoracic response and injury mechanisms in high-energy, limited-stroke, lateral velocity pulse impacts to the human chest wall. To impart such impacts, a linear impactor was developed which had a limited stroke and minimally decreased velocity during impact. The peak impact velocity was 5.6 ± 0.3 m/s. A series of BioSID and cadaver tests were conducted to measure biomechanical response and injury data. The conflicting effects of padding on increased deflection and decreased acceleration were demonstrated in tests with BioSID and cadavers. The results of tests conducted on six cadavers were used to test several proposed injury criteria for side impact. Linear regression was used to correlate each injury criterion to the number of rib fractures. This test methodology captured and supported a contrasting trend of increased chest deflection and decreased TTI when padding was introduced.

National Accident Sampling System (NASS) data, for the years 1993-1995, suggests a high frequency of tibiofemoral joint fractures among automotive accident victims. In addition, the NASS data also suggests that these injuries may be attributable to direct axial loading via the floor pan and/or the foot controls. Hirsch and Sullivan (1965), and Kennedy and Bailey (1968) conducted quasi-static fracture experiments axially compressing human tibiofemoral joints at low rates of loading and low angles of flexion. Hirsch and Sullivan observed a mean fracture load of approximately 8 kN compared to approximately 16 kN in the Kennedy and Bailey study. The current tibiofemoral joint injury criterion used in anthropomorphic dummies is based on Hrisch and Sullivan''s data. The current study involved impact experiments on human tibiofemoral joints (aged 71.4±11.2) directed in a superior direction along the axis of the tibia with the joint flexed 90°.

The response of the spine acceleration to rib and pelvis acceleration input of the side impact dummy (SID) is modeled using system identification methods. The basis for the modeling is a simplified representation of the SID by a 3-mass, 2-spring system. Based on this spring-mass representation, two types of response models are established. The first is a "gray-box" type with rib/pelvis-spine relationship modeled by Auto Regression with eXogeneous (or eXtra) input (ARX) type system models. The structure of these models is partially based on the spring-mass simplified representation, hence the notion "gray- box." The parameters of these models are identified through linear regression from test data. The second type of models is noted "physical model" here, since it is strictly a state- space form of the equation of motion of the simple spring-mass representation.

Although not life threatening in most cases, victims of lower extremity injuries frequently end up living with a poor quality of life. The implementations of airbag supplement restraint systems significantly reduce the incidence of head and chest injuries. However, the frequency of leg injuries remains high. Several finite element models of the foot and ankle have been developed to further the understanding of this injury mechanism. None of those models employed accurate geometry among various bony segments. The objective of this study is to develop a foot and ankle finite element model based on CT scan data so that joint geometry can be accurately represented. The model was validated against experimental data for several different configurations including typical car crash situations.

As of toady, statutory crash test dummies take neither bracing nor passive muscular effect into account in the lower limb area. The influence of the lower extremity musculature is however arising as a major concern for the study of front seat occupant protection. The lower extremity prototype of the THOR dummy, including a model of the human plantarflexion actuator passive response, was tested in dynamic dorsiflexion. A dynamic test series was performed on Thor-Lx under test conditions similar to those used by Portier et al., 1996, on cadavers and Hybrid III dummy. The test setup imposed a dynamic dorsiflexion to the foot by means of a load exerted under the ball of the foot with no impact velocity. The Thor-Lx and Hill responses are compared to cadaver responses. It is important to note that as of today there are no data available to demonstrate that the passive resistance of the cadaver is equivalent to resistance of a tensed human.

In the past, many studies have been dedicated to the comparison of dummies and human body behavior in different impact conditions. However, the complex boundary conditions generated by a complete restraint system render it difficult to compare both human surrogates in a car environment. Furthermore, the great dispersion among car occupants is an additional difficulty which is difficult to overcome with experimental studies, Computer simulation, as far as a validated human body model is available, gives a unique possibility to assess the influence of some restraint parameters, whilst all remaining parameters are unchanged. To this end, a 3D finite element human body model validated in many different impact configurations against a large number of biomechanical corridors was used. In order to compare responses, models of Hybrid III and Eurosid 1 dummies were also used.

A new lower extremity has been developed to be used with Thor, the NHTSA Advanced Frontal Dummy. The new lower extremity, known as Thor-Lx, consists of the femur, tibia, ankle joints, foot, a representation of the Achilles' tendon and the associated flash/skins, it has been designed to improve biomechanical response under axial loading of the femur during knee impacts, axial loading of the tibia, static and dynamic dorsiflexion, static plantarflexion and inversion/aversion. Instrumentation includes a standard Hybrid ill femur load cell, accelerometers, load cells, and rotary potentiometers to capture relevant kinematic and dynamic information from the foot and tibia. The design also allows the Tnor-Lx to be attached to the Hybrid III, either at the hip, or at the knee.

Previous experimental and theoretical studies on isolated human knees have shown that increasing the contact area over the knee during blunt impact can prevent serious knee injury (i.e. joint fracture). Because large contact areas are typically associated with lower stiffness impact interfaces, this suggests that instrument panels could provide some protection to the knee during a car accident. Further, the knee-to-IP contact is one of the first contact events which occur during a head-on crash, thus, one optimal scenario might be to dissipate as much energy as possible at the knee without causing serious knee injury. This would help minimize the kinetic energy in the upper body, possibly reducing the need for more aggressive countermeasures (i.e. air bags) later in the impact event. Our objective in the current study was to determine how different car interior geometries and crash pulses would affect specific occupant responses during a head-on car crash.

The occupants of passenger vehicles struck in the side by another vehicle are more likely to be fatally injured than are occupants of the striking vehicle. The risk of fatality in a side-struck car is higher still when the striking vehicle is a pickup or utility vehicle rather than a passenger car of the same mass. This suggests there are other factors inherent to pickup and utility vehicle design in addition to mass that contribute to this increased risk. In this paper, results are presented from a series of six 90-degree, front-to-side crash tests conducted with both vehicles moving. The side-struck vehicle, a Mercury Grand Marquis with a BioSID (biofidelic side impact dummy) in the driver position, was moving at 24 km/h (15 mi/h) in all tests.

Ten pairs of thawed fresh-frozen human cadaveric lower arm specimens were subjected to lateral three-point bending. Either the radius or ulna were impacted with a 4.5 kg dropped weight at approximately 3 m/s or tested quasi-statically in a materials testing machine. Fracture occurred primarily near the loading site with an average dynamic peak load of 1370 N and average peak moment of 89 Nm. Differences between the radius and ulna were not significant. Static fracture load and moments were approximately 20% lower. Sectional and mineral properties of each specimen near the fracture sites were measured.

New thermoset polyurethane polymers for automotive body panels can replace steel, SMC, and thermoplastics. These new materials offer short cycle times, thin wallstock, high temperature post mold processing, excellent durability, and new levels of productivity. Two new materials have been developed. One is a high-performance polyurea system that allows for oven bakes up to one hour at 190°C. The other is a high performance polyurethane developed for thin wallstock applications that has established new levels of productivity in the manufacture of rocker panels, fascia, and side moldings in Europe. The quality of these polymers is such that high productivity via robotic demold and trimming has been demonstrated. The durability of both these products is evident from the point of demold when the part exhibits an unprecedented toughness. Tight parameter control via a computer-based Expert System®1 improves cycle times, monitors manufacturing, and reduces scrap.

In comparison to other vehicles motorcycles have very special driving characteristics, so the typical use of motorcycles is clearly distinct from the use of passenger cars. At Darmstadt University the riding behavior of motorcyclists has been experimentally investigated [2, 3, 4, 5], especially in order to determine their exhaust and noise emissions in real traffic. The results and the essential differences between motorcycles and cars should be considered in the discussion of testing methods and limiting values, e.g., for exhaust and noise emissions of two-wheelers. This paper presents a comparison between the typical driving performance of motorcycles and passenger cars and contains results of motorcycle exhaust and noise emission measurements in real traffic and in statutory tests. The current legal measuring standards are found not to represent the reality of motorcycle traffic in a sufficient manner.