In the early stages of the car development process, it is very important to determine the necessary crash depth, such as the clearance between the hood and the underlying engine, with respect to pedestrian head protection.
A review of past research indicates that the average deceleration magnitude and duration interval of an impact are important factors in the standard formula of Head Injury Criterion (HIC).
In this paper, in order to predict the minimal crash depth in the direction of the impact, a simplified uniaxial model is used throughout the analysis and the constant (average) deceleration magnitude is used to construct an ideal square-type deceleration curve rather than the practical deceleration curve. The mathematics behind the requirements for satisfactory crash depth for pedestrian head protection is discussed in detail. The basic relationships between crash depth and practical structural characteristics, such as structural stiffness and inertial force, are also discussed theoretically.
These studies are very useful not only for determining the necessary crash depth, but also for the development of actual crushable structures to improve vehicle assessment scores in the area of pedestrian head protection.