Atsutaka Tamura

Effects of ground impact on traumatic brain injury in a fender vault pedestrian crash

The present study replicated a series of vehicle–to–pedestrian crashes involved in a right–corner frontal impact up to a secondary or ground impact. The results showed that post–impact pedestrian kinematics and subsequent kinetics are not easily predictable and are considerably affected by the vehicle front structure and impact speed. The Head Injury Criterion (HIC), calculated with a resultant linear acceleration of the head, reached around 1000 or higher because of secondary head strike even at 25 km/h. Similarly, the maximum rotational acceleration of the head resulted in higher values owing to ground impact rather than primary head strike. This study has also suggested the importance of accounting for both linear and angular acceleration pulses applied to the head to assess the potential risk of sustaining Traumatic Brain Injury (TBI) due to eventual contact with the ground even at low impact speeds, and this should be a focus of future research.

Effects of Anatomical Site and Loading Rate on Tensile Behavior of Fiber Bundles Isolated From Nerve Roots

The present study has investigated the characteristics of the tensile behavior of fiber bundles isolated from the spinal nerve roots. By conducting a series of uniaxial stretching tests at three different velocities, 0.2, 2, and 20 mm/s, we found a significant difference (P < 0.05) in failure strain (∼0.15), linear portion of elastic modulus (∼20 MPa), and tensile strength (∼2 MPa) between low (0.2 mm/s) and high (20 mm/s) loading rates. However, it was revealed that mechanical properties of fiber bundles were resultantly on the order of the same magnitude, indicating that their mechanical responses were relatively insensitive to a strain rate irrespective of a 100-fold increase in the applied stretching velocities. It was also confirmed that the “spinal level effect” does exist in the nerve roots, i.e., a fiber bundle isolated from the thoracic spinal level is the strongest in mechanical strength compared to that of the cervical and lumbar spinal levels (P < 0.01), which suggests we should pay more close attention to an anatomical site where excised samples are obtained. The mechanical data obtained here will be useful to improve a mathematical human body model and to assess the potential injury in crash simulations relevant to whiplash associated disorder.Copyright

Gear and Bearing Failure Detection Using Vibration Monitoring and Mahalanobis-Taguchi System

Vibration monitoring is used to detect a failure in gear systems. An approach in this paper uses Mahalanobis-Taguchi System (MTS) along with vibration monitoring to improve a sensitivity of failure detection. Running tests were conducted by using a power-circulating-type gear test machine. Gear and bearing failures were examined. The Mahalanobis distance was calculated by using measured vibration acceleration data during the running tests. Relations between the Mahalanobis distance and the initiation and propagation of the gear failures or the bearing failures were discussed. The results show that the Mahalanobis distance is an effective indicator of the gear and bearing failures.Copyright

Pedestrian Accident Reconstruction Using a Human Body Finite Element Model

A series of numerical experiments were carried out using a full-scale vehicle finite element (FE) model and a validated pedestrian FE model with a detailed brain to replicate a typical, vehicle-to-pedestrian collision. We revealed that post-impact kinematics and kinetics are considerably unpredictable due to the intrinsic complexity of pedestrian crash, and ground impact rather than the primary head strike is likely to cause a serious traumatic brain injury (TBI) for struck pedestrians. We also found the importance of accounting for both translational and rotational acceleration pulses applied to the head to assess the potential risk of TBI due to eventual contact with the ground. These findings suggest that an effective countermeasure should be introduced to reduce the risk of sustaining TBIs due to secondary as well as primary head strikes even at the low-speed impact levels.Copyright

Strength of plastic helical wheels meshed with various types of worms

This study investigates the strength of plastic helical wheels meshed with enveloping and cylindrical worms whose tooth profiles mesh in line contact with helical wheels. Running fatigue tests of plastic helical wheels together with a conventional cylindrical involute worm, a line contact enveloping worm, and a line contact cylindrical worm were conducted. The tooth bearings, tooth temperatures, and fatigue lives of plastic helical wheels meshed with the different worms were examined at various center distances. From these results, the effects of worm tooth forms on the strength of the plastic helical wheels were determined.