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Finite element simulation of air bags as part of the automotive occupant restraint system is rapidly evolving as a new CAE tool in support of car product development. The majority of occupant computer simulations are concentrated around the study of occupant impact into the air bag when the air bag is substantially inflated. Further, the initial air bag representation in the simulation prior to deployment is of an unfolded configuration. These simplifications do not compromise simulation of crashes wherein the dummy comes in contact with the air bag after it is substantially full. The situation wherein the dummy interacts with the air bag early during the inflation is of interest when the occupant is located close to the air bag prior to deployment. In such cases the predeploy-ment geometry of the air bag in the model needs to be representative of the actual air bag folded configuration and the unfolding of the air bag needs to be simulated.

A PC based interactive program was developed to simulate the unfolding and deploying process of a driver side airbag in the sagittal plane. The airbag was represented by a series of nodes. The maximum allowable stretch was less or equal to one between any two nodes. We assumed that the airbag unfolding was pivoted about folded points. After the completion of the unfolding process the airbag would begin to deploy. During the deploying process, two parameters were used to determine the nodal priority of the inflation. The first parameter was the distance between the instantaneous and final positions of a node. Nodes with longer distances to travel will have to move faster. We also considered the distance between the current nodal position and the gas inlet location. For a node closer to the gas inlet, we assumed that the deploying speed was faster. A graphical procedure was used to calculate the area of the airbag.

Digital human modeling (DHM) progress worldwide will be much faster and cohesive if the diverse community now developing simulations has a global blueprint for DHM, and is able to work together efficiently. DHM developers and users can save time by building on each other's work. This paper highlights a panel discussion on DHM goals and strategic plans for the next decade to begin formulating the international blueprint. Four subjects are chosen as the starting points: (1) moving DHM into the public safety and internet arenas, (2) role of DHM in computer assisted surgery and automotive safety, (3) DHM in defense applications, and (4) DHM to improve workplace ergonomics.

Component tests were conducted in order to evaluate the biofidelity of the THOR-NT on the head, neck, thorax, abdomen, face, femur, and lower extremity (THOR-Lx). The biofidelity of the dummy was evaluated by comparing its biofidelic responses with the PMHS response corridors. Likewise, component tests on each body part of the Hybrid III were conducted, and the biofidelity between THOR-NT (THOR-Lx) and Hybrid III were compared. The THOR tests were subject to test procedures established by GESAC, Inc./NHTSA; the THOR-Lx tests were subject to NHTSA/VRTC procedures. Responses on the head and femur of both the THOR-NT and Hybrid III were within the PMHS response corridors. However, for other body parts - although each component of THOR-NT did not yield results that satisfied all the PMHS response corridors - the responses of THOR-NT were closer to the corridors than those of the Hybrid III.

A three-dimensional finite element model of a human neck has been developed in an effort to study the mechanics of cervical spine while subjected to impacts. The neck geometry was obtained from MRI scans of a 50th percentile male volunteer. This model, consisting of the vertebrae from C1 through T1 including the intervertebral discs and posterior elements, was constructed primarily of 8-node brick elements. The vertebrae were modeled using linear elastic-plastic materials, while the intervertebral discs were modeled using linear viscoelastic materials. Sliding interfaces were defined to simulate the motion of synovial facet joints. Anterior and posterior longitudinal ligaments, facet joint capsular ligaments, alar ligaments, transverse ligaments, and anterior and posterior atlanto-occipital membranes were modeled as nonlinear bar elements or as tension-only membrane elements. A previously developed head and brain model was also incorporated.

Regarding THOR-50AM dummy lower extremities (hereafter referred to as ""THOR''and ""THOR-LX'') developed as an assembly of lower extremities for next-generation dummies in frontal impact test, we have conducted a series of tests as follows. HYGE sled tests with a toe-board simulating the impact upon intrusion into the vehicle compartment around the occupant feet, dummy dropping tests with two different postures; one is the upright posture with the knees set straight and another is the posture with the knees bent, in order to apply impact loads and to measure/evaluate the impact response characteristics.

In recent years, several kinds of seat systems that aim to reduce cervical spinal injuries in rear impacts, so called ‘whiplash injuries’, have been released by some car manufacturers and seat suppliers in the world. Meanwhile, several kinds of dummies have been developed to be representatives of occupants under such conditions. One of these is the BioRID II equipped with a realistic spine constructed of multiple vertebrae similar to that of a human. It is regarded as the most biofidelic dummy for low speed rear impact. Using this dummy, some typical ‘whiplash protective’ seat systems currently available were dynamically tested to see their performance on injury reduction. From the results of these tests, the design direction to lessen the injury level more efficiently was determined.

Lower extremity injuries in frontal automotive crashes usually occur with footwell intrusion where both the knee and foot are constrained. In order to identify factors associated with tibial shaft injury, a series of numerical simulations were conducted using a finite element model of the whole human body. These simulations demonstrated that tibial mid-shaft injuries in frontal crashes could be caused by an abrupt change in velocity and a high rate of footwell intrusion.

A nonlinear foam was added to a previously created three-dimensional finite element model of the Hybrid III dummy chest which consisted of six steel ribs, rib damping material, the sternum, a spine box and a pendulum. Two standard calibration pendulum impact tests for a Hybrid III dummy chest were used to validate the new model. An explicit finite element analysis code PAM-CRASH was utilized to simulate the dynamic process. At impact velocities of 6.7 m/s and 4.3 m/s, the force and deflection time history as well as the force-deflection plots showed good agreement between model predictions and calibration data. Peak strains also agreed well with experimental data.

The structural differences between the Thor-NT and Thor-FT dummies, which have been proposed as next-generation dummies for frontal crash tests, were examined and the differences in dynamic response were verified by testing. Tests were performed on a HYGE sled simulating a frontal crash at an impact speed of 56 km/h. The 3-point seatbelt plus air bag combination was adopted as the restraint mechanism. Differences in characteristics of the two dummies in the neck, thorax, and abdomen were found by calibration tests. Test results showed that the variation in shape of the abdominal area of the pelvis generates some disparity in the flexion of the thorax and abdomen.

In occupant safety simulations it is desirable to extend existing rigid body occupant models towards deformable Finite Element models. Thereby a wider range of occupant / structure interactions can be covered and a better accuracy can be achieved. This paper describes some aspects of the FE modelling of the EUROSID thorax for use in an explicit Finite Element code. First a single rib model is evaluated, then a full thorax is generated and inserted into a rigid body Dummy model. Experimental results from impactor tests serve as a basis for the validation of the model.

Improvements for pedestrian head protection in a car-pedestrian accident have been discussed in several countries. Test methods for evaluating head protection have been proposed, and most are sub-systems using rigid headforms with or without headskin. In those tests, HIC is used as a criterion for head protection. This paper discusses the test conditions and requirements of the headform impact test. The influence of different test conditions and their importance on head impact test requirements, were verified. The primary items cited are as follows: (1) The results of the rigid headform were similar to that of the human cadaver skull in cases without skull fractures. Consequently, the rigid headform can be used for the impactor simulating a condition without skull fracture. (2) In the cases of HIC≤1000, the force-deformation curves of the hoodtops showed similar characteristics with maximum dynamic deformations over 60mm. (3) Impactor mass affected the maximum acceleration and HIC.

The mechanisms of knee fracture were studied experimentally using cadaveric knees and analytically by computer simulation. Ten 90 degree flexed knees were impacted frontally by a 20 kg pendulum with a rigid surface, a 450 psi (3.103 MPa) crush strength and a 100 psi (0.689 MPa) crush strength aluminum honeycomb padding and a 50 psi (0.345 MPa) crush strength paper honeycomb padding at a velocity of about five m/s. During rigid surface impact, a patella fracture and a split condylar fracture were observed. The split condylar fracture was generated by the patella pushing the condyles apart, based on a finite element model using the maximum principal stress as the injury criterion. In the case of the 450 psi aluminum honeycomb padding, the split condylar fracture still occurred, but no patella fractures were observed because the honeycomb provided a more uniform distribution of patella load. No bony fractures in the knee area occurred for impacts with a 50 psi paper honeycomb padding.

Previously, a 10-year-old (YO) pediatric thorax finite element model (FEM) was developed and verified against child chest stiffness data measured from clinical cardiopulmonary resuscitation (CPR). However, the CPR experiments were performed at relatively low speeds, with a maximum loading rate of 250 mm/s. Studies showed that the biomechanical responses of human thorax exhibited rate sensitive characteristics. As such, the studies of dynamic responses of the pediatric thorax FEM are needed. Experimental pediatric cadaver data in frontal pendulum impacts and diagonal belt dynamic loading tests were used for dynamic validation. Thoracic force-deflection curves between test and simulation were compared. Strains predicted by the FEM and the injuries observed in the cadaver tests were also compared for injury assessment and analysis. This study helped to further improve the 10 YO pediatric thorax FEM.

To investigate the human head impact tolerance in terms of changes in vital functions, a series of head impact experiments was performed using live monkeys, which are morphologically analogous to humans. To find a causal relationship between the impact and changes in vital functions, three kinds of experimental conditions were used: translational acceleration impact and rotational acceleration impact (both using a head restraint mask with broad contact area), and impact of the unrestrained head against a padded flat surface. The results indicated that the concussion, cerebral contusion and skull fracture in the monkeys depended on: i) the translational and rotational acceleration impact; ii) the contact area of the impact; iii) the amplitude and duration of the imposed head acceleration*; iv) the direction of the impact region (whether frontal or occipital).

A total of eight low-speed, rear-end impact tests using two Post Mortem Human Subjects (PMHS) in a seated posture are reported. These tests were conducted using a HYGE-style mini-sled. Two test conditions were employed: 8 kph without a headrestraint or 16 kph with a headrestraint. Upper-body kinematics were captured for each test using a combination of transducers and high-speed video. A 3-2-2-2-accelerometer package was used to measure the generalized 3D kinematics of both the head and pelvis. An angular rate sensor and two single-axis linear accelerometers were used to measure angular speed, angular acceleration, and linear acceleration of T1 in the sagittal plane. Two high-speed video cameras were used to track targets rigidly attached to the head, T1, and pelvis. The cervical spine kinematics were captured with a high-speed, biplane x-ray system by tracking radiopaque markers implanted into each cervical vertebra.

It is important to more clearly identify the relationship among the ramping-up motion, straightening of the whole spine, and cervical vertebrae motion in order to clarify minor neck injury mechanism. The aim of the current study is to verify the influence of the change of the spine configuration on human cervical vertebral motion and on head/neck/torso kinematics under low speed rear-end impacts. Seven healthy human volunteers participated in the experiment under the supervision of an ethics committee. Each subject sat on a seat mounted on a sled that glided backward on rails and simulated actual car impact acceleration. Impact speeds (4, 6, and 8 km/h), and seat stiffness (rigid and soft) without headrest were selected. During the experiment, the change of the spine configuration (measured by a newly developed spine deformation sensor with 33 paired set strain gauges and placed on the skin) and the interface load-pressure distribution was recorded.

The most important tool to date for testing seat-systems in rear impacts is a crash test dummy. However, investigators have noted limitations of the most commonly used dummy, the Hybrid III. Although the BioRID I is a step closer to a biofidelic crash test dummy it is not user-friendly and the straightening of the thoracic spine kyphosis is smaller than that of humans. The objective of this study is to compare the performance of the latest prototype of the BioRID, the P3, with those of volunteers. The BioRID P3 has new neck muscle substitutes, a softer thoracic spine and a softer rubber torso than does the BioRID I. The BioRID P3 was validated against volunteer test data in both a rigid and a standard seat without head restraints. The dummy kinematic performance, pressure distribution between subject and seatback, spine curvature, neck loads and accelerations were compared to those of seven volunteers and a Hybrid III fitted with a standard neck.

The non-physiological motions of human cervical vertebrae were analyzed in volunteer tests for rear-end impacts and were considered to be an important parameter for neck injuries. The objectives of this study are to improve the Marko de Jager neck model using volunteer test data and to analyze the influence of horizontal and vertical accelerations on cervical vertebral motion. In the beginning of this study, a neck model was positioned based on X-ray cineradiography of a volunteer. Motions of each vertebra were compared with those of volunteer test data for low speed rear-end impacts (4, 6, 8km/h). In these comparisons, the differences of vertebrae motions between the neck model and the volunteer tests were found. To improve the validity of the neck model, the connection properties and the bending properties of the upper and lower vertebrae of the model were modified to increase rigidity.

Computational human body models, especially detailed finite element models are suitable for investigation of human body kinematic responses and injury mechanism. A real-world lateral vehicle-tree impact accident was reconstructed by using finite element method according to the accident description in the CIREN database. At first, a baseline vehicle FE model was modified and validated according to the NCAP lateral impact test. The interaction between the car and the tree in the accident was simulated using LS-Dyna software. Parameters that affect the simulation results, such as the initial pre-crash speed, impact direction, and the initial impact location on the vehicle, were analyzed. The parameters were determined by matching the simulated vehicle body deformations and kinematics to the accident reports.