Human Shoulder Response to High Velocity Lateral Impact.

The armies of the North Atlantic Treaty Organization need a shoulder injury criterion for the EuroSID-2re dummy that must be reliable over a large range of loading conditions, from high velocity, short duration impacts (28 m/s - 3 ms) to low velocity long, duration impacts (4 m/s - 50 ms). In the literature, the human shoulder response to lateral impact was investigated at bounds of the loading condition spectrum as previously mentioned. For the low velocities, the injuries were mainly clavicle fractures and the maximum compression between the acromion and the sternum (Cmax) was proposed as an injury criterion. For the high velocities, the typical injury was humerus fractures, including a crushed humeral head. The present study investigates the human shoulder response at an intermediate loading condition (14 m/s - 9 ms). Six lateral shoulder impact tests have been performed with three Post Mortem Human Subjects using a rigid impactor. The duration of the impact was controlled by means of an aluminum honeycomb that decelerated the impactor during the impact. The shoulder external deflection (impactor-to-sternum) ranged between 40 to 64 mm and the applied forces ranged from 4.3 kN to 8 kN. Four shoulders out of six sustained AIS2 injuries. Two acromio-clavicular joint dislocations, one clavicle fracture, and one scapula fracture were observed. Though the shoulder force responses were closer to those induced by the high velocity, short duration impacts, the injury patterns resembled those observed for low velocity, long duration loading conditions. Furthermore, the estimated acromion-to-sternum deflection values were not inconsistent with the prediction of the shoulder injury risk curve of the literature. Despite the relatively high-velocity impact (14.3 m/s), the shoulder injury mechanism appeared to be similar to those observed in the automotive field.

3D deformation and dynamics of the human cadaver abdomen under seatbelt loading.

According to accident analysis, submarining is responsible for most of the frontal car crash AIS 3+ abdominal injuries sustained by restrained occupants. Submarining is characterized by an initial position of the lap belt on the iliac spine. During the crash, the pelvis slips under the lap belt which loads the abdomen. The order of magnitude of the abdominal deflection rate was reported by Uriot to be approximately 4 m/s. In addition, the use of active restraint devices such as pretensioners in recent cars lead to the need for the investigation of Out-Of-Position injuries. OOP is defined by an initial position of the lap belt on the abdomen instead of the pelvis resulting in a direct loading of the abdomen during pretensioning and the crash. In that case, the penetration speed of the belt into the abdomen was reported by Trosseille to be approximately 8 to 12 m/s. The aim of this study was to characterize the response of the human abdomen in submarining and OOP. A total of 8 PMHS abdomens were loaded using a lap belt. In order to investigate the injury mechanisms, the abdominal deflection rate and the compression were imposed such that they were not correlated. The specimens were seated upright in a fixed back configuration. The lap belt was placed at the level of the mid-umbilicus, between the iliac crest and the 12th rib. The belt was pulled horizontally along the sides of the specimens causing a symmetrical loading of the abdomen. In addition to the local parameters such as the belt and back forces or the belt displacements, the 3D external deformation of the abdomen was recorded. The forces measured between the back of the cadaver and the seat showed that a mass effect should be taken into account in the abdominal behaviour in addition to viscosity. The back force was greater than the belt force in low speed (submarining like) tests while it was lower for high-speed (OOP like) tests. A lumped parameter model was developed to confirm the experimental results and to be able to compare the load penetration characteristics to the results reported in the literature. The injury outcomes are provided and compared to all the published data. The PMHS sustained MAIS2-3 abdominal injuries in the low speed tests and MAIS2-4 injuries in the high speed tests. Finally, the dynamic 3D deformation of the abdominal wall was reconstructed and is provided for further validation of finite element models of the human abdomen.

Comparison of Hybrid III, Thor-alpha and PMHS Response in Frontal Sled Tests.

Two series of nine frontal sled tests were conducted to evaluate the behavior of the Hybrid III and Thor-alpha dummies. The first series was conducted at 50 kph with airbag and 4 kN force-limited shoulder belt and the second series at 30 kph and only a 4 kN force-limited shoulder belt. In each series, three replicate tests were conducted with each dummy and compared with three PMHS. The data provided by the same instrumentation located at the same position were compared to assess the biofidelity of both dummies. The results were mass scaled in order to account for the differences between the anthropometry of the cadaver. The good test-to-test repeatability for each dummy permitted to compare the mean value of each recorded parameter. Based on the cadaver response, the results show that the Thor-alpha provides responses that are more similar to those of PMHS than the Hybrid III. The flexible joints in the thoracic spine, the sternum design and the more humanlike ribcage give more similar accelerations than the Hybrid III as compared to those of the PMHS. Nevertheless, some parts have to be improved in order to better follow the behavior of the human subject. The head-neck complex, the chest, the shoulder and the pelvis of the Thor-alpha have a more humanlike behavior but some differences remain. The distribution of the deceleration between the components is sometimes different compared to those of the cadaver, even if the resultants are similar. The dummies and most particularly the Hybrid III are less sensitive to the change in restraint systems and tests conditions than a cadaver.