Test methodology for low-speed rear impact human kinematics and dynamics

Design of crash dummies and development of numeric models of the human body require data sets which specify the performance of real humans in crash impact conditions. Rear impact conditions have become increasingly important during the last decade. This resulted in a growing number of research projects focusing on the kinematic and dynamic response of the human body. A test and analysis methodology and procedure to set up these types of tests to establish a set of response parameters are presented in this chapter. Choice of instrumentation, film techniques, and data processing are discussed. An example of anthropometry measures required for further analysis is presented. A three-linkeage mechanism, as an analog used to define response parameters, is introduced. In the past, analysis was limited to head and neck for forward impacts, but this needs to be extended to include the spine and pelvis for rear impact conditions as the interaction of car seat and body cannot be omitted. The response corridors developed from a series of volunteer tests are presented as an illustration of a data set to be used for dummy and numeric model evaluation. The methodology presented here and the specified response parameters can be used for any rear impact full body test and would make it possible to combine results of several research projects which could create a growing database

Neck forces and moments and head accelerations in side impact

Objectives: Although side-impact sled studies have investigated chest, abdomen, and pelvic injury mechanics, determination of head accelerations and the associated neck forces and moments is very limited. The purpose of the present study was therefore to determine the temporal forces and moments at the upper neck region and head angular accelerations and angular velocities using postmortem human subjects (PMHS). Methods: Anthropometric data and X-rays were obtained, and the specimens were positioned upright on a custom-designed seat, rigidly fixed to the platform of the sled. PMHS were seated facing forward with the Frankfort plane horizontal, and legs were stretched parallel to the mid-sagittal plane. The normal curvature and alignment of the dorsal spine were maintained without initial torso rotation. A pyramid-shaped nine-accelerometer package was secured to the parietal-temporal region of the head. The test matrix consisted of groups A and B, representing the fully restrained torso condition, and groups C and D, representing the three-point belt-restrained torso condition. The change in velocity was 12.4 m/s for groups A and C, 17.9 m/s for group B, and 8.7 m/s for group D tests. Two specimens were tested in each group. Injuries were scored based on the Abbreviated Injury Scale. The head mass, center of gravity, and moment of inertia were determined for each specimen. Head accelerations and upper neck forces and moments were determined before head contact. Results: Neck forces and moments and head angular accelerations and angular velocities are presented on a specimen-by-specimen basis. In addition, a summary of peak magnitudes of biomechanical data is provided because of their potential in serving as injury reference values characterizing head-neck biomechanics in side impacts. Though no skull fractures occurred, AIS 0 to 3 neck traumas were dependent on the impact velocity and restraint condition. Conclusions: Because specimen-specific head center of gravity and mass moment of inertia were determined, and a suitable instrumentation system was used for data collection and analysis, head angular accelerations and neck forces and moments determined in the present study can be used with confidence to advance impact biomechanics research. Although the sample size is limited in each group, results from these tests serve as a fundamental data set to validate finite element models and evaluate the performance and biofidelity of federalized and prototype side-impact dummies with a focus on head-neck biomechanics

Biomechanics of human occupants in simulated rear crashes : documentation of neck injuries and comparison of injury criteria

The objective of this study was to subject smallfemale and large male cadavers to simulated rear impact, document soft-tissue injuries to the neck, determine the kinematics, forces and moments at the occipital condyles, and evaluate neck injury risks using peak force, peak tension and normalized tension-extension criteria. Five unembalmed intact human cadavers (four small females and one large male) were prepared using accelerometers and targets at the head, Tl, iliac crest, and sacrum. The specimens were placed on a custom-designed seat without head restraint and subjected to rear impact using sled equipment. High-speed cameras were used for kinematic coverage. After the test, x~rays were obtained, computed tomography scans were taken, and anatomical sections were obtained using a cryomicrotome. Two female specimens were tested at 4.3 mls (mean) and the other two were tested at 6.8 mls (mean), and one large male specimen was subjected to 6.6 mls velocity. One female specimen tested at 4.1 mls did not sustain injury. All others produced injuries to soft tissue and joint-related structures that included tearing of the anterior longitudinal ligament, rupture of the ligamentum flavum, hematoma at the upper facet joint, anterior disc disruption at the lower spine, and facet joint capsule tear. Compressive forces (100 to 254 N) developed within 60 ms after impact. Tensile forces 189 were higher (369 to 904) and developed later (149 to 211 ms). While peak shear forces (268 to 397 at 4.3 mls and 257 to 525 N at 6.8 m/s) did not depend on velocity, peak tensile forces (369 to 391 Nat 4.3 mlsand 672 to 904 N at 6.8 m/s) seemed to correlate with velocity. Peak extension moments ranged from 22.0 to 33.5 Nm at low velocity and 32.7 to 46.6 Nm at high velocity. All these biOIpechanical data attained their peaks in the extension phase (with very few exceptions), which ranged from 179 to 216 ms. The neck injury criterion, NIC, exceeded the suggested limit of 15 m2;s2 in all specimens; Axial force and bending moment data were used to evaluate various neck injury criteria (Nij, NTE, peak tension and peak extension). The risk for AIS ~ 3 injury for the combined tension-extension criteria was 3 percent in one female specimen tested at 6.8 m/s. For the other specimens the risk of AIS ~ 3 injury wass less than five percent using all criteria

Biomechanics of human occupants in simulated rear crashes : documentation of neck injuries and comparison of injury criteria

The objective of this study was to subject smallfemale and large male cadavers to simulated rear impact, document soft-tissue injuries to the neck, determine the kinematics, forces and moments at the occipital condyles, and evaluate neck injury risks using peak force, peak tension and normalized tension-extension criteria. Five unembalmed intact human cadavers (four small females and one large male) were prepared using accelerometers and targets at the head, Tl, iliac crest, and sacrum. The specimens were placed on a custom-designed seat without head restraint and subjected to rear impact using sled equipment. High-speed cameras were used for kinematic coverage. After the test, x~rays were obtained, computed tomography scans were taken, and anatomical sections were obtained using a cryomicrotome. Two female specimens were tested at 4.3 mls (mean) and the other two were tested at 6.8 mls (mean), and one large male specimen was subjected to 6.6 mls velocity. One female specimen tested at 4.1 mls did not sustain injury. All others produced injuries to soft tissue and joint-related structures that included tearing of the anterior longitudinal ligament, rupture of the ligamentum flavum, hematoma at the upper facet joint, anterior disc disruption at the lower spine, and facet joint capsule tear. Compressive forces (100 to 254 N) developed within 60 ms after impact. Tensile forces 189 were higher (369 to 904) and developed later (149 to 211 ms). While peak shear forces (268 to 397 at 4.3 mls and 257 to 525 N at 6.8 m/s) did not depend on velocity, peak tensile forces (369 to 391 Nat 4.3 mlsand 672 to 904 N at 6.8 m/s) seemed to correlate with velocity. Peak extension moments ranged from 22.0 to 33.5 Nm at low velocity and 32.7 to 46.6 Nm at high velocity. All these biOIpechanical data attained their peaks in the extension phase (with very few exceptions), which ranged from 179 to 216 ms. The neck injury criterion, NIC, exceeded the suggested limit of 15 m2;s2 in all specimens; Axial force and bending moment data were used to evaluate various neck injury criteria (Nij, NTE, peak tension and peak extension). The risk for AIS ~ 3 injury for the combined tension-extension criteria was 3 percent in one female specimen tested at 6.8 m/s. For the other specimens the risk of AIS ~ 3 injury wass less than five percent using all criteria