Introduction of Pulse Shapes and Durations into Impulse-Momentum Collision Models

Reconstruction of motor vehicle collisions using impulse center-based impulse-momentum formulations is commonly accomplished using computer codes to solve the conservation equations assuming instantaneous momentum exchange. Some models accommodate finite duration, or non-instantaneous impulses. This paper describes an impulse-momentum with impulse center, graphical-input computer code designed with selectable pulse width to better simulate real-world collisions compared with solutions based on instantaneous momentum exchange. This paper presents a more realistic approach to the momentum formulation using an impulse center by applying a finite duration, rectangular crash pulse to obtain modeling results that are then compared to the instantaneous momentum exchange approach. Detailed comparisons with two crash tests are presented to demonstrate the limitations and improvement. First, simulation of a frontal barrier impact with no rotation is expected to be insensitive to pulse duration. Second, results from an offset side impact vehicle-to-barrier test, with large resulting angular velocity, are compared with computations to illustrate the significant increase in accuracy when actual pulse width is modeled. The significant vehicle rotation during the collision changed the relationship of the vehicle center of gravity to the impulse center during the impact. Computed crash mechanics parameters such as speed, change in translational velocity, angular velocity, vehicle heading and deformation energy are compared with test results.