Abstract
Worldwide, the number of people killed in road traffic crashes each year is estimated at almost 1.2 million, while the number of people injured could be as high as 50 million. Deaths from road traffic injuries account for around 23% of all deaths from injury. The number of road traffic deaths worldwide and injuries is forecast to rise by some 65% between 2000 and 2020. The majority of such deaths are currently among “vulnerable road users”, under which are pedestrians (1).
During years, pedestrian accident statistics and kinematics were intensively studied and led to a discretization into experimental test methods to examine the pedestrian protection level of cars. One of these test methods represents the contact between the hip area of a pedestrian and the front end of the car during a collision. The performance of a car is examined by impacting with the so called Upper Legform, a testing device that represents the human femur and hip. These tests are carried out by Euro NCAP (European New Car Assessment Programme) (2) and results are published as consumer information. European regulation No 78/2009 (3) also prescribes Upper Legform testing. However, results are only used for monitoring purposes. Unfortunately, experimental results for this Upper Legform test method are not promising for most available car models. The kinetic energy levels at which to execute the Upper Legform tests are determined by the cars exterior design. In order to decrease the test energy levels, the car exterior’s geometry should be changed dramatically which seems unfeasible with current car styling conception for middle sized family cars. Stringent packaging requirements cause that clearance levels between exterior surface and hard underlying structures are not sufficient to absorb impact energy without exceeding the prescribed test limits.
This paper focuses on improving the crashworthiness of SEAT’s car models in the area of pedestrian hip protection. The car’s exterior design, and therefore the kinetic test energy level, is left untouched and the focus is on creating more clearance between exterior surface and hard internal structures to properly absorb the accompanying impact energy. Because packaging requirements do not allow for more ‘static’ clearance, a conceptual solution in the form of a collapsible structure is developed that is actuated only in case of pedestrian collision and allows for more ‘dynamic’ clearance. A series of Upper Legform experiments was executed to generate the data and knowledge required to develop and correlate a corresponding finite element model. The resulting simulation model is used as design instrument to develop conceptual solutions that can be applied to the car’s frontal structure in order to improve pedestrian hip protection. Both simulations and physical tests showed promising results.
Keywords: Pedestrian protection, Upper Legform, Frontal car design, Dynamic clearance, Collapsible structure