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The relative motion of the brain with respect to the skull has been widely studied to investigate brain injury mechanisms under impacts, but the motion patterns are not yet thoroughly understood. This work analyzes brain motion patterns using the most recent and advanced experimental relative brain/skull motion data collected under low-severity impacts. With a minimum total pseudo-strain energy, the closed-form solutions for rigid body translation and rotation were obtained by matching measured neutral density target (NDT) positions with initial NDT positions. The brain motion was thus separated into rigid body displacement and deformation. The results show that the brain has nearly pure rigid body displacement at low impact speed. As the impact becomes more severe, the increased brain motion primarily is due to deformation, while the rigid body displacement is limited in magnitude for both translation and rotation. Under low-severity impacts in the sagittal plane, the rigid body brain translation has a magnitude of 4-5 mm, and the whole brain rotation is on the order of +/-5 degrees.

Traumatic rupture of the aorta (TRA) is an important transportation-related injury. This study investigated TRA mechanisms using in situ human cadaver experiments. Four quasi-static tests and one dynamic test were performed. The quasi-static experiments were conducted by perturbing the mediastinal structures of the cadavers. The mechanisms investigated included anterior, superior, and lateral displacement of the heart and aortic arch. The resulting injuries ranged from partial tears to complete transections. All injuries occurred within the peri-isthmic region. Intimal tears were associated with the primary injuries. The average failure load and stretch were 148 N and 30 percent for the quasi-static tests. This study illustrates that TRA can result from appropriate application of nominal levels of longitudinal load and tension. The results demonstrate that intraluminal pressure and whole-body acceleration are not required for TRA to occur. The results suggest that the role of the ligamentum arteriosum is likely limited, and that TRA can occur in the absence of pulmonary artery injury. Tethering of the descending thoracic aorta by the parietal pleura is a principal aspect of this injury.

This study focuses on the biaxial mechanical properties of planar aorta tissue at strain rates likely to be experienced during automotive crashes. It also examines the structural response of the whole aorta to longitudinal tension. Twenty-six tissue-level tests were conducted using twelve thoracic aortas harvested from human cadavers. Cruciate samples were excised from the ascending, peri-isthmic, and descending regions. The samples were subjected to equibiaxial stretch at two nominal speed levels using a new biaxial tissue-testing device. Inertia-compensated loads were measured to facilitate calculation of true stress. High-speed videography and regional correlation analysis were used to track ink dots marked on the center of each sample to obtain strain. In a series of component-level tests, the response of the intact thoracic aorta to longitudinal stretch was obtained using seven aorta specimens. The aorta fails within the peri-isthmic region. The aorta fails in the transverse direction, and the intima fails before the media or adventitia. The aorta tissue exhibits nonlinear behavior. The aorta as complete structure can transect completely from 92 N axial load and 0.221 axial strain. Complete transection can be accompanied by intimal tears. These results have application to finite element modeling and the better understanding of traumatic rupture of the aorta.

This study characterizes the response of the human cadaver abdomen to high-speed seatbelt loading using pyrotechnic pretensioners. A test apparatus was developed to deliver symmetric loading to the abdomen using a seatbelt equipped with two low-mass load cells. Eight subjects were tested under worst-case scenario, out-of-position (OOP) conditions. A seatbelt was placed at the level of mid-umbilicus and drawn back along the sides of the specimens, which were seated upright using a fixed-back configuration. Penetration was measured by a laser, which tracked the anterior aspect of the abdomen, and by high-speed video. Additionally, aortic pressure was monitored. Three different pretensioner designs were used, referred to as system A, system B and system C. The B and C systems employed single pretensioners. The A system consisted of two B system pretensioners. The vascular systems of the subjects were perfused. Peak anterior abdominal loads due to the seatbelt ranged from 2.8 kN to 10.1 kN. Peak abdominal penetration ranged from 49 mm to 138 mm. Peak penetration speed ranged from 4.0 m/s to 13.3 m/s. Three cadavers sustained liver injury: one AIS 2, and two AIS 3. Cadaver abdominal response corridors for the A and B system pretensioners are proposed. The results are compared to the data reported by Hardy et al. (2001) and Trosseille et al. (2002).