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In a frontal automotive crash, the driver's foot is usually stepping on the brake pedal as an instinctive response to avoid a collision. The tensile force generated in the Achilles tendon produces a compressive preload on the tibia. If there is intrusion of the toe board after the crash, an additional external force is applied to the driver's foot. A series of dynamic impact tests using human cadaveric specimens was conducted to investigate the combined effect of muscle preloading and external force. A constant tendon force was applied to the calcaneus while an external impact force was applied to the forefoot by a rigid pendulum. Preloading the tibia significantly increased the tibial axial force and the combination of these forces resulted in five tibial pylon fractures out of sixteen specimens.

A finite element human model has been developed to simulate occupant behavior and to estimate injuries in real-world car crashes. The model represents an average adult male of the US population in a driving posture. Physical geometry, mechanical characteristics and joint structures were replicated as precise as possible. The total number of nodes and materials is around 67,000 and 1,000 respectively. Each part of the model was not only validated against human test data in the literature but also for realistic loading conditions. Additional tests were newly conducted to reproduce realistic loading to human subjects. A data set obtained in human volunteer tests was used for validating the neck part. The head-neck kinematics and responses in low-speed rear impacts were compared between the measured and calculated results. The validity of the lower extremity part was examined by comparing the tibia force in a foot impact between the test data and simulation results.

Incompatibility between two colliding cars is becoming an important issue in passive safety engineering. Among various phenomena, indicating signs of incompatibility, over-riding and under-riding are likely caused by geometrical incompatibility in vertical direction. The issue of over-riding and under-riding is, therefore, not only a problem for partner-protection but also a possible disadvantage in self-protection. One of the possible solutions of this dual contradictory problem is to have a good structural interaction between the front-ends of two cars. Studies have been done to develop a test protocol for assessment of this interaction and to define criteria for evaluation but mostly in terms of aggressivity, which is a term describing incompatibility of a relatively stronger car. In this study, it was hypothesized that homogeneous front-end could be a possible better solution for good structural interaction.

A finite element model of the human lower extremity has been developed in this study to simulate lower extremity behavior in frontal car crashes. Precise geometry of the human lower extremity and material properties of the hard and soft tissues were introduced to the model. The performance of the model was evaluated by comparing with dynamic loading test data using post mortem human subjects (PMHS). The comparison proved its ability to estimate dynamic responses of the human lower extremity. A study was conducted using the model to investigate possible factors of loading to the ankle and tibia. Force and moment were calculated with different time history profiles of footwell intrusion and pelvis motion. The results suggested that timing of maximum intrusion was important as well as its magnitude. It was also found that loading to the tibia could be affected not only by intrusion but also by pelvis motion.

When considering a CTC (car to car) frontal crash between a small light car and a large heavy car, it is necessary to evaluate the stiffness and strength of each vehicle body. As interactive force at the contact surface cannot be measured directly in a car to car crash test, a simplified practical method has been developed to estimate the interactive force based on the vehicle deceleration. The adequacy and consistency of the proposed method was verified by using the principle of conservation of energy. The calculated force-deformation curves revealed that the interactive force reached the maximum designed strength of the small light car based on the ODB (Offset Deformable Barrier) test for crash protection, while the force level was far below the corresponding design limit of the large heavy car. It was observed that the relatively lower stiffness of the small light car resulted in absorbing a larger share of the total input energy of the system when crashed into the large heavy car.

This paper analyzed the mechanisms of injury in high speed, right-lateral impacts of stock car auto racing, and interaction of the occupant and the seat system for the purpose of reducing the risk of injury, primarily rib fractures. Many safety improvements have been made to stock car racing recently, including the Head and Neck Support devices (HANS®), the 6-point restraint harnesses, and the implementation of the SAFER Barrier. These improvements have contributed greatly to mitigating injury during the race crash event. However, there is still potential to improve the seat structure and the understanding of the interaction between the driver and the seat in the continuation of making racing safety improvements. This is particularly true in the case of right-lateral impacts where the primary interaction is between the seat supports and the driver and where the chest is the primary region of injury.

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.

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.)

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.

Sled tests were conducted at farside oblique angles of 15°, 45°, and 75° with a Part 572 dummy restrained by a conventional driver lap/shoulder belt system or a preinflated driver inflatable restaint. Occupant dynamics were compared in similar tests where an inboard energy absorbing lateral restraint of the upper torso was or was not used. It can be concluded that the seat wing improves the control of the dummy's dynamics in oblique impacts by directing the occupant's motion more forward into the restraint system, thereby taking more advantage of the restraining potential of the shoulder belt or inflatable restraint in controlling the deceleration of the dummy and enhancing the benefit of the restraint system. However, additional factors associated with the use of a seat wing remain to be investigated including the effect of impact force on the occupant, interaction with out-of-position occupants and comfort/convenience.

Previous pendulum impact tests have shown that knee joint injuries and tibial-fibular fractures may occur when loads are directed against the lower leg rather than directly against the femur in the knee. In order to further improve our understanding of lower extremity restraint mechanics, simulated frontal barrier crash experiments were conducted with unembalmed human cadavers and an anthropomorphic dummy restrained by a two-point shoulder belt. In the first test, an experimental bolster was specifically positioned so that the cadaver's lower leg would strike the bolster, thus inducing restraining loads entirely below the knee joint. The analysis of occupant kinematics showed that the flexed knee rode over and forward of the low-positioned bolster. Restraint induced considerable shearing load across the knee joint. Bolster measurements indicated a peak load of approximately 4.0 kN per leg which resulted in a contralateral central tear of the posterior cruciate ligaments.

Spinal kinematics and kinetics of human cadaveric specimens subjected to -Gx acceleration are reported along with an attempt to design a surrogate spine for use in an anthropomorphic test device (ATD). There were a total of 30 runs on 9 embalmed and 2 unembalmed cadavers which were heavily instrumented. External photographic targets were attached to T1, T12, and the pelvis to record spinal kinematics. The subjects were restrained by upper and lower leg clamps attached to an impact seat equipped with a six-axis load cell. A rigid link 486 mm long and pinned at both ends was proposed for use in an ATD as a surrogate spine. An optimization method was used to obtain the location and length of a linkage which followed the least squares path of Tl relative to the pelvis.

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.

A series of volunteer and dummy impact experiments was performed on a Hyge-type (accelerator) sled to study the relative motion between the upper torso restraint and the torso surface. Kinematic measurements were made using a three-dimensional photogrammetric analysis of high-speed film data. Belt slip was found to be in the range of approximately 10 to 30 mm with more slip experienced by volunteers than the dummy. The dummy showed a slight change in amount of slip with acceleration level and all slip takes place within the first 80 ms of belt loading.

The biodynamic response of the femur during passively restrained -Gx impact acceleration is reported in this paper. Eleven unembalmed cadavers, ranging in age from 21 to 65 and weighing from 50 to 96 kg, were tested in a VW Rabbit seat with a passive belt and knee restraint. Sectioned parts of the VW knee bolster were placed about 130 mm away from the patella at the initiation of the tests. The height of the knee bolsters was adjusted individually in the eleven tests. Ten were set for loading directly through the patella. In one run, the impact was below the knee joint. The sectioned bolsters were mounted on a rigid frame and instrumented with triaxial load cells. A six-axis load cell was installed in the right femur. Photo targets were attached directly to the femur and tibia. Sled runs were made at 22 and 35 g. Only one cadaver sustained bilateral femoral fractures at 35 g.

Head-to-knee interaction of the right front passenger dummy can occur in some 30-35 MPH crash barrier tests. The biofidelity and significance of these interactions as related to predicting human response was addressed in this study. In a series of laboratory experiments an instrumented headform was dropped on the dummy knee to simulate the barrier interactions. These test results were then related to the human by dropping the same headform on the cadaver leg. The instrumented headform was dropped from three heights to impact the Part 572 dummy knee at three velocities. Two impact sites and two impact angles were used. These test parameters bracketed the barrier conditions. Measurements from headform accelerometers permitted calculation of HIC value for comparison to barrier values. Comparable experiments were subsequently performed with three unembalmed cadaver subjects using the same headform and test procedures.

Post-crash conditions of a car's steering system, when properly measured and documented, provide an insight to the interaction between the driver and the steering system that occurs during a frontal car crash. Steering system conditions were investigated in two interrelated phases: 1. Deformation of the wheel rim, spokes, and hub, and 2. Compression resistance force of the steering column. Two devices were developed to document the “crash loading” response of these two segments of the car's steering system. One device was designed to measure the deformations of the steering wheel and the other the force required to further compress the steering column. An initial test series on 19 “crashed” cars “field tested” the devices, developed the test techniques and procedures needed for in-depth studies, and formulated necessary data handling methods and data collection forms.

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.

Finite element models of human body segments have been developed in recent years. Numerical simulation could be helpful when understanding injury mechanisms and to make injury assessments. In the lower leg injury research in NISSAN, a finite element model of the human ankle/foot is under development. The mesh for the bony part was taken from the original model developed by Beaugonin et al., but was revised by adding soft tissue to reproduce realistic responses. Damping effect in a high speed contact was taken into account by modeling skin and fat in the sole of the foot. The plantar aponeurosis tendon was modeled by nonlinear bar elements connecting the phalanges to the calcaneus. The rigid body connection, which was defined at the toe in the original model for simplicity, was removed and the transverse ligaments were added instead in order to bind the metatarsals and the phalanges. These tendons and ligaments were expected to reproduce a realistic response in compression.

Posterior translation of the tibia with respect to the femur can stretch the posterior cruciate ligament (PCL). Fifteen millimeters of relative displacement between the femur and tibia is known as the Injury Assessment Reference Value (IARV) for the PCL injury. Since the anterior protuberance of the tibial plateau can be the first site of contact when the knee is flexed, the knee bolster is generally designed with an inclined surface so as not to directly load the projection in frontal crashes. It should be noted, however, that the initial flexion angle of the occupant knee can vary among individuals and the knee flexion angle can change due to the occupant motion. The behavior of the tibial protuberance related to the knee flexion angle has not been described yet. The instantaneous angle of the knee joint at the timing of restraining the knee should be known to manage the geometry and functions of knee restraint devices.