Shingo Wanami

Finite element analysis of kinematic behaviour and injuries to pedestrians in vehicle collisions

In vehicle-to-pedestrian collisions, the characteristics of a vehicles frontal shape and structural stiffness have a significant influence on the kinematics and injury risk of the pedestrians body regions. In the present study, the kinematic behaviour and injury risk of the pedestrians were investigated in collisions against vehicles with different frontal shapes. The THUMS (Total HUman Model for Safety) pedestrian finite element (FE) model was used and impacted by three different types of vehicle FE models (passenger car, one-box vehicle and sport-utility vehicle [SUV]) representing the different frontal shapes at 40 km/h. In the simulation with the passenger car-to-pedestrian impact, the pedestrian wrapped around the hood, and the resulting bending moment of the lower extremity and head injury criterion (HIC) value were high. In the simulation with the one-box vehicle-to-pedestrian impact, the pedestrians upper torso was directly hit by the front end of the vehicle. The pelvis and chest had contact with the stiff vehicle frontal panel, resulting in a high stress being observed on the rib cage. In the simulation with the SUV-to-pedestrian impact, the force of the pelvis was high due to the contact with the vehicle hoods leading edge. The results indicated that the frontal shape of the vehicle has a large effect on the pedestrian kinematic behaviour, including the impact velocity of the pelvis, chest, and head against the vehicle. Moreover, the stiffness of the vehicle structure can affect the deformation mode of the human body segments, such as the lower extremities and the rib cage. The injury predictions for each body region from the FE analyses agreed with observations from pedestrian accidents involving a car, one-box vehicle and SUV, respectively.

Bumper contact sensor for pedestrian collisions based on analysis of pedestrian kinematic behaviour

An active bonnet and pedestrian airbag are effective in providing a high level of pedestrian head protection. For triggering the activation of these systems, a reliable sensor that distinguishes a pedestrian collision from collisions against other colliding objects is necessary. In this research, a pedestrian contact sensor based on the pressure of a deformable chamber was investigated from finite-element (FE) analysis. In a simulation of a component test of a chamber impact, the internal pressure of the chamber increased with the volume deformation of the chamber according to Boyles law. The chamber was installed above the top plane of the bumper energy absorber of a simple car model, and FE simulations of a car–pedestrian collision were conducted. The chamber deformed and its internal pressure increased as the bumper energy absorber deformed during contact with the pedestrian leg. It was shown that the pressure response of the chamber could be detected, irrespective of vehicle shape and structure. This particular pressure response in pedestrian collisions was different from that in collisions into other objects such as a road pole. The contact force of the bumper energy absorber tends to be linear with the pressure change of the chamber. It was shown that a pedestrian collision can be distinguished with high reliability from other colliding objects using the chamber pressure based on the colliding characteristics depending on each colliding object.