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The objective of this study is to present a potential mechanism for traumatic brain injury resulting from a lateral blunt impact to the head during SUV-to-pedestrian impact. An AM50th percentile model of the human head was developed, and the mechanical response predicted by the model was validated against available cadaveric test data. It was found that the traction force due to the inertia of the brain mass plays a key role in brainstem lesion prior to the primary contact as well as the local stress/strain distribution around the lateral ventricle immediately after the contact with a vehicle. For the covering abstract see ITRD E141569.
The present paper describes the tooth surface temperature and the power transmission efficiency of plastic sinecurve gears in the running condition. The plastic sine-curve and involute gears were manufactured by injection molding. The running tests for sine-curve and involute gears were performed under no-lubrication and grease-lubrication conditions, and the tooth surface temperature and the power transmission efficiency were measured. Test results show that the sine-curve gears for operating condition had lower tooth surface temperatures and higher power transmission efficiencies than involute gears under no-lubrication conditions, but in the grease-lubrication condition the superiority of sine-curve gears was not observed.
Backover collisions causing Traumatic Brain Injuries (TBIs) are underreported, and its severity may have been overlooked and underestimated.We conducted a series of pedestrian impact simulations involving backover collisions with a reversing vehicle, at a low speed of 10 km/h, to determine the risk of sustaining severe TBIs.Our modelling studies revealed a significant risk despite the 'moderate' impact configuration applied.By systematically performing injury analyses based on selected mechanical parameters, we found that TBI risk involved in primary head strike with a striking vehicle was almost negligible because of the low-speed collision, but significant injuries result from ground impact.Our study also demonstrated that pedestrians are potentially at a greater risk for TBI when struck by a Sport Utility Vehicle (SUV) than a conventional sedan, because the impact energy would be effectively transmitted from the SUV via its flat rear surface with a steep angle.
Abstract We developed a 50th-percentile American male pedestrian model including a detailed brain, and the mechanical responses and kinematic biofidelity predicted by this model were validated against the available cadaveric test data. Vehicle-to-pedestrian impact simulations were then performed to investigate a potential mechanism for traumatic brain injury resulting from a lateral blunt impact to the head. Due to inertia of the brain mass, it was found that the average traction force produced in the cervical spinal cord exceeded 50 N in the impact involving a sport utility vehicle and 25 N in the impact involving a sedan, when the striking vehicle was travelling at 40 km/h. This inertial loading may play a key role in a brainstem, or upper-cervical-cord, lesion occurring before head strike. Results of this study suggest that close attention should be paid to pedestrian kinematics during free flight even before the head makes primary contact with the striking vehicle. Keywords: traumatic brain injuryvehicle-to-pedestrian impacttraction forcecervical spinal cordbrainstemdiffuse axonal injury Acknowledgment The authors thank the staff of Bioengineering Center, Wayne State University, for their contribution to the development of the head and thoracic parts of our human model, THUMS.
Mechanical properties of brain tissue characterized in high-rate loading regime are indispensable for the analysis of traumatic brain injury (TBI). However, data on such properties are very limited. In this study, we measured transient response of brain tissue subjected to high-rate extension. A series of uniaxial extension tests at strain rates ranging from 0.9 to 25 s-1 and stress relaxation tests following a step-like displacement to different strain levels (15-50%) were conducted in cylindrical specimens obtained from fresh porcine brains. A strong rate sensitivity was found in the brain tissue, i.e., initial elastic modulus was 4.2 ± 1.6, 7.7 ± 4.0, and 18.6 ± 3.6 kPa (mean ± SD) for a strain rate of 0.9, 4.3, and 25 s-1, respectively. In addition, the relaxation function was successfully approximated to be strain-time separable, i.e., material response can be expressed as a product of time-dependent and strain-dependent components as:K(t) = G(t)σe(ε), where G(t) is a reduced relaxation function, G(t) = 0.416e-t/0.0096+0.327e-t/0.0138+0.256e-t/1.508, and σe(ε) is the peak stress following a step input of ε. Results of the present study will improve biofidelity of computational models of a human head and provide useful information for the analysis of TBI under injurious environments with strain rates greater than 10 s-1.
