Can CRASH/damage analysis be used for breakaway collisions?

[MSI]

The conventional form of vehicle damage analysis in the case of a central collision with a fixed, rigid object is based on the assumption of a full-term collision, during which the vehicle velocity is reduced to zero (e.g., figure 1).

full term collision.jpg (14.24 KiB) Viewed 1837 times

Figure 1 Full-Term Collision
For the case of a fixed, rigid object,

full_term_collision.jpg (9.64 KiB) Viewed 1837 times

When a vehicle collides with a breakaway or yielding obstacle, once the obstacle breaks and/or yields, additional energy may be absorbed by movement of the obstacle. The mass of the obstacle must be considered as well as any additional resistance forces which may occur (i.e., contact friction forces between the obstacle and ground as it moves).
In the case of a breakaway or yielding obstacle, followed by a low-level deceleration (see Figure 2), the Delta-V corresponding to a given extent of vehicle damage is less than that obtained from equation (2).

interrupted_collision.jpg (14.8 KiB) Viewed 1837 times

Figure 2 Interrupted, or Incomplete, Collision
In the case of a continued high-level deceleration to rest, after crushing of the vehicle is complete (see Figure 3), the impact speed-change corresponding to a given extent of vehicle damage can be greater than that obtained from equation (2).

interuppted_collsion_2.jpg (25.22 KiB) Viewed 1837 times

Figure 3 Interrupted, or Incomplete Collision, Continued High-Level Deceleration
Thus, without proper consideration of the residual velocity after breakaway or yielding of the obstacle in the cited collision type, the value of Delta-V obtained from equation (2) on the basis of vehicle crush can be substantially in error. In an interrupted, or incomplete, collision, (Figure 2 and 3).